subject:(Astronomy)

UCLA

1. Boehle, Anna Lee. The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph.

Degree: Astronomy, 2017, UCLA

URL: http://www.escholarship.org/uc/item/25p9r0nr

► In this thesis, I explore the environments around supermassive black holes (SMBHs) in the nearby universe. The thesis is divided into five chapters. I begin… (more)

▼ In this thesis, I explore the environments around supermassive black holes (SMBHs) in the nearby universe. The thesis is divided into five chapters. I begin with an introduction to SMBHs in general and to the astronomical instrumentation that is used to study their direct environments in the highest possible detail. The second chapter focuses on the closest galactic nucleus to Earth: the center of our own Milky Way galaxy. The orbits of stars around the Milky Way SMBH, Sgr A*, can be used to determine the black hole mass and distance. I present a new method of analyzing images of the Galactic center to increase the time baseline for faint, short-period stars that orbit Sgr A*. I use this new analysis method to improve the constraints on the mass of the SMBH and the distance to the Galactic center by a factor of 2. The second chapter discusses the upgrade of the detector in the OSIRIS instrument at W.M. Keck Observatory. This adaptive-optics-fed instrument uses an array of small lenses to sample a rectangular section of the focal plane, producing up to 3,000 spectra simultaneously with a spectral resolution of 3,800 and diffraction-limited spatial resolution. I helped to upgrade the original near-infrared (NIR) Hawaii-2 detector to a Hawaii-2RG, which improved the raw sensitivity of OSIRIS by a factor of 2 at J-band wavelengths (1.2 - 1.4 μm) and 1.6 at H- and K-band wavelengths (1.5 - 2.4 microns). The third and fourth chapters discuss a NIR integral field spectroscopic survey of nearby LINER (low ionization nuclear emission line) galaxies, the lowest luminosity class of active galactic nuclei. LINERs are found at the centers of ∼1/3 of galaxies within 40 Mpc, but it is unclear whether accretion onto a supermassive black hole or another mechanism such as shock excitation drives their emission. I use the OSIRIS instrument to map the strength and kinematics of singly ionized iron, molecular hydrogen, and hydrogen recombination lines at spatial scales of 1-10 pc in the nuclei of 11 nearby LINERs, in close proximity to their central SMBHs. The third chapter presents a detailed study of the closest LINER in the sample, NGC 404, in which I find that its LINER emission is likely excited by shocks, and the final chapter presents results from the survey sample as a whole.

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Boehle, A. L. (2017). The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph. (Thesis). UCLA. Retrieved from http://www.escholarship.org/uc/item/25p9r0nr

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Boehle, Anna Lee. “The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph.” 2017. Thesis, UCLA. Accessed March 02, 2021. http://www.escholarship.org/uc/item/25p9r0nr.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Boehle, Anna Lee. “The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph.” 2017. Web. 02 Mar 2021.

Vancouver:

Boehle AL. The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph. [Internet] [Thesis]. UCLA; 2017. [cited 2021 Mar 02]. Available from: http://www.escholarship.org/uc/item/25p9r0nr.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Boehle AL. The Environments Around Nearby Supermassive Black Holes and the Upgrade of the OSIRIS Integral Field Spectrograph. [Thesis]. UCLA; 2017. Available from: http://www.escholarship.org/uc/item/25p9r0nr

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. MacLeod, Morgan Elowe. Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy.

Degree: Astronomy & Astrophysics, 2016, University of California – Santa Cruz

URL: http://www.escholarship.org/uc/item/8p01x7b9

► This thesis uses computational modeling to study of phases of dramatic interaction that intersperse stellar lifetimes. In galactic centers stars trace dangerously wandering orbits dictated… (more)

▼ This thesis uses computational modeling to study of phases of dramatic interaction that intersperse stellar lifetimes. In galactic centers stars trace dangerously wandering orbits dictated by the combined gravitational force of a central, supermassive black hole and all of the surrounding stars. In binary systems, stars' evolution – which causes their radii to increase substantially – can bring initially non-interacting systems into contact. Moments of strong stellar interaction transform stars, their subsequent evolution, and the stellar environments they inhabit. In tidal disruption events, a star is partially or completely destroyed as tidal forces from a supermassive black hole overwhelm the star's self gravity. A portion of the stellar debris falls back to the black hole powering a luminous flare as it accretes. This thesis studies the relative event rates and properties of tidal disruption events for stars across the stellar evolutionary spectrum. Tidal disruptions of giant stars occur with high specific frequency; these objects' extended envelopes make them vulnerable to disruption. More-compact white dwarf stars are tidally disrupted relatively rarely. Their transients are also of very different duration and luminosity. Giant star disruptions power accretion flares with timescales of tens to hundreds of years; white dwarf disruption flares take hours to days. White dwarf tidal interactions can additionally trigger thermonuclear burning and lead to transients with signatures similar to type I supernovae. In binary star systems, a phase of hydrodynamic interaction called a common envelope episode occurs when one star evolves to swallow its companion. Dragged by the surrounding gas, the companion star spirals through the envelope to tighter orbits. This thesis studies accretion and flow morphologies during this phase. Density gradients across the gravitationally-focussed material lead to a strong angular momentum barrier to accretion during common envelope. Typical accretion efficiencies are in the range of 1 percent the Hoyle-Lyttleton accretion rate. This implies that compact objects embedded in common envelopes do not grow significantly during this phase, increasing their mass by at most a few percent. This thesis models the properties of a recent stellar-merger powered transient to derive constraints on this long-uncertain phase of binary star evolution.

Subjects/Keywords: Astronomy

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APA (6^th Edition):

MacLeod, M. E. (2016). Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy. (Thesis). University of California – Santa Cruz. Retrieved from http://www.escholarship.org/uc/item/8p01x7b9

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

MacLeod, Morgan Elowe. “Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy.” 2016. Thesis, University of California – Santa Cruz. Accessed March 02, 2021. http://www.escholarship.org/uc/item/8p01x7b9.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

MacLeod, Morgan Elowe. “Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy.” 2016. Web. 02 Mar 2021.

Vancouver:

MacLeod ME. Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy. [Internet] [Thesis]. University of California – Santa Cruz; 2016. [cited 2021 Mar 02]. Available from: http://www.escholarship.org/uc/item/8p01x7b9.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

MacLeod ME. Social Stars: Modeling the Interactive Lives of Stars in Dense Clusters and Binary Systems in the Era of Time Domain Astronomy. [Thesis]. University of California – Santa Cruz; 2016. Available from: http://www.escholarship.org/uc/item/8p01x7b9

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

UCLA

3. Mace, Gregory Nathan. Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy.

Degree: Astronomy, 2014, UCLA

URL: http://www.escholarship.org/uc/item/56q669xw

► The mass of a star at formation determines its subsequent evolution and demise. Low-mass stars are the most common products of star formation and their… (more)

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Mace, G. N. (2014). Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy. (Thesis). UCLA. Retrieved from http://www.escholarship.org/uc/item/56q669xw

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Mace, Gregory Nathan. “Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy.” 2014. Thesis, UCLA. Accessed March 02, 2021. http://www.escholarship.org/uc/item/56q669xw.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Mace, Gregory Nathan. “Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy.” 2014. Web. 02 Mar 2021.

Vancouver:

Mace GN. Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy. [Internet] [Thesis]. UCLA; 2014. [cited 2021 Mar 02]. Available from: http://www.escholarship.org/uc/item/56q669xw.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Mace GN. Investigating Low-Mass Binary Stars And Brown Dwarfs with Near-Infrared Spectroscopy. [Thesis]. UCLA; 2014. Available from: http://www.escholarship.org/uc/item/56q669xw

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

4. Nayyeri, Hooshang. A Study of Massive and Evolved Galaxies at z>3.

Degree: Physics, 2014, University of California – Riverside

URL: http://www.escholarship.org/uc/item/7379d0g5

► I use deep data taken as part of the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) observations by the Cosmic Assembly Near-infrared Deep… (more)

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Nayyeri, H. (2014). A Study of Massive and Evolved Galaxies at z>3. (Thesis). University of California – Riverside. Retrieved from http://www.escholarship.org/uc/item/7379d0g5

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Nayyeri, Hooshang. “A Study of Massive and Evolved Galaxies at z>3.” 2014. Thesis, University of California – Riverside. Accessed March 02, 2021. http://www.escholarship.org/uc/item/7379d0g5.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Nayyeri, Hooshang. “A Study of Massive and Evolved Galaxies at z>3.” 2014. Web. 02 Mar 2021.

Vancouver:

Nayyeri H. A Study of Massive and Evolved Galaxies at z>3. [Internet] [Thesis]. University of California – Riverside; 2014. [cited 2021 Mar 02]. Available from: http://www.escholarship.org/uc/item/7379d0g5.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Nayyeri H. A Study of Massive and Evolved Galaxies at z>3. [Thesis]. University of California – Riverside; 2014. Available from: http://www.escholarship.org/uc/item/7379d0g5

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of California – Berkeley

5. Newman, Sarah. Galactic Winds and Structure of z~2 Star-forming Galaxies.

Degree: Astrophysics, 2013, University of California – Berkeley

URL: http://www.escholarship.org/uc/item/93c8g0n1

► Galactic-scale outflows are a key driver of galaxy evolution through their feedback effect on star-formation and their ejection of metals and energy into the inter-galactic… (more)

▼ Galactic-scale outflows are a key driver of galaxy evolution through their feedback effect on star-formation and their ejection of metals and energy into the inter-galactic medium (IGM). While it is known that outflows likely play an important role in the quenching of star-formation - transforming actively star-forming, blue galaxies into their `red and dead' counterparts - this role is currently not well understood. In particular, at z~2, during the most active epoch of star-formation, the mass and energy in these outflows is poorly constrained, as is the mechanism for launching them. Furthermore, active-galactic nuclei (AGN) in the centers of massive star-forming galaxies (SFGs) likely play an important role in star-formation quenching, but we do not have a clear understanding of how this AGN feedback compares with that of star-formation driven feedback, and it is not known how many of these massive SFGs at z~2 even have AGN. This issue is complicated by the fact that many high-z AGN are likely highly obscured, and have strong nebular emission line contributions from both star-formation and the AGN.In this dissertation, I explore these issues using high-spatial and spectral resolution integral field unit spectroscopic data of z~2 SFGs. The observations are obtained with the instrument SINFONI on the European Southern Observatory (ESO) Very Large Telescope (VLT) at Cerro Paranal. These high-quality data allow spatially-resolved studies of the gas-phase kinematics of these galaxies, as well dynamical information on their outflows. In this work, I explore outflow properties in one galaxy with exceptionally deep data, allowing detailed examination of the outflow energetics, spatial extent and underlying ISM properties, as well those from a larger sample of galaxies. I also probe the fraction of SFGs in our sample which contain (possibly obscured) AGN, and study how this affects our determination of galaxy properties, such as gas-phase metallicity. Finally, I study a subsample of z~2 galaxies whose turbulent velocities dominate the kinematic signature, and examine the link between the overall evolution of z~2 galaxies and the systems we see today. Together this body of work explores how galactic-scale outflows in z~2 SFGs are launched, effect the IGM and eventually shape the evolution of their host galaxies.

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Newman, S. (2013). Galactic Winds and Structure of z~2 Star-forming Galaxies. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/93c8g0n1

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Newman, Sarah. “Galactic Winds and Structure of z~2 Star-forming Galaxies.” 2013. Thesis, University of California – Berkeley. Accessed March 02, 2021. http://www.escholarship.org/uc/item/93c8g0n1.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Newman, Sarah. “Galactic Winds and Structure of z~2 Star-forming Galaxies.” 2013. Web. 02 Mar 2021.

Vancouver:

Newman S. Galactic Winds and Structure of z~2 Star-forming Galaxies. [Internet] [Thesis]. University of California – Berkeley; 2013. [cited 2021 Mar 02]. Available from: http://www.escholarship.org/uc/item/93c8g0n1.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Newman S. Galactic Winds and Structure of z~2 Star-forming Galaxies. [Thesis]. University of California – Berkeley; 2013. Available from: http://www.escholarship.org/uc/item/93c8g0n1

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Oulu

6. Venhola, A. (Aku). Modeling galaxy interactions with Holmberg’s analog computer.

Degree: 2015, University of Oulu

URL: http://urn.fi/URN:NBN:fi:oulu-201504021286

► Galaxy dynamics using simulation models has been an important research field during the last 50 years. In the beginning of the 20th century there were… (more)

▼ Galaxy dynamics using simulation models has been an important research field during the last 50 years. In the beginning of the 20th century there were already extensive catalogs of galaxies which showed the large diversity of the galaxy shapes, although there was no theory to explain those. Nowadays, galaxy dynamics can be extensively studied by simulating the dark matter, star, and gas cloud orbits numerically, but before the era of modern computers constructing even a simple model was a considerable challenge. In the beginning of the 1940’s Erik Holmberg (University of Lund) introduced his new integration procedure for galaxy simulations (Holmberg, 1941) which can be considered as a pioneering study in galaxy dynamics. In his work, Holmberg replaced gravitation with light intensity, based on the fact that they both obey the same 1/r² attenuation with distance. He modeled the interaction of two galaxies with light bulbs and came out with the conclusion that some features of the galaxies, for example tails and intergalactic bridges, can be explained by gravitational tidal forces. Holmberg’s work was significant for being the first simulation of galaxy dynamics, which could be upgraded only 20 years later, when the first simulations with electronic computers were started. Despite the significance of the Holmberg’s simulations and the large number of citations they have received, there is no marks that the simulations would have been repeated. During the summer of 2013 I reconstructed the Holmberg’s experimental setting in the University of Oulu. The experiment was made two times: once using exactly the same parameters that Holmberg used, and another time with small changes in the initial parameters. In this thesis I introduce the Holmberg’s experiments and the theory behind that. In chapter 2, I give a brief overview of disk galaxies and methods used in galaxy simulations. In chapter 3, I present the theoretical basis of Holmberg’s analog simulation. Chapter 4 covers the hardware and the practical realization of the experiment. In chapter 4, I represent the results and compare them with the Holmberg’s results.

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Venhola, A. (. (2015). Modeling galaxy interactions with Holmberg’s analog computer. (Masters Thesis). University of Oulu. Retrieved from http://urn.fi/URN:NBN:fi:oulu-201504021286

Chicago Manual of Style (16^th Edition):

Venhola, A (Aku). “Modeling galaxy interactions with Holmberg’s analog computer.” 2015. Masters Thesis, University of Oulu. Accessed March 02, 2021. http://urn.fi/URN:NBN:fi:oulu-201504021286.

MLA Handbook (7^th Edition):

Venhola, A (Aku). “Modeling galaxy interactions with Holmberg’s analog computer.” 2015. Web. 02 Mar 2021.

Vancouver:

Venhola A(. Modeling galaxy interactions with Holmberg’s analog computer. [Internet] [Masters thesis]. University of Oulu; 2015. [cited 2021 Mar 02]. Available from: http://urn.fi/URN:NBN:fi:oulu-201504021286.

Council of Science Editors:

Venhola A(. Modeling galaxy interactions with Holmberg’s analog computer. [Masters Thesis]. University of Oulu; 2015. Available from: http://urn.fi/URN:NBN:fi:oulu-201504021286

University of Oulu

7. Mustonen, J. (Juha). Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella.

Degree: 2015, University of Oulu

URL: http://urn.fi/URN:NBN:fi:oulu-201504021200

► Pro Gradu-tutkielmassa kartoitetaan Marsin Protonilus Mensaen ja Moreux-kraatterin alueelta löytyviä jäätikkömäisiä kohteita. Alue sijaitsee Marsin dikotomiarajalla, joka sisältää runsaasti merkkejä amatsoonisella aikakaudella tapahtuneesta jäätiköitymisestä. Protonilus… (more)

▼ Pro Gradu-tutkielmassa kartoitetaan Marsin Protonilus Mensaen ja Moreux-kraatterin alueelta löytyviä jäätikkömäisiä kohteita. Alue sijaitsee Marsin dikotomiarajalla, joka sisältää runsaasti merkkejä amatsoonisella aikakaudella tapahtuneesta jäätiköitymisestä. Protonilus Mensaen alueelta tehdyissä aiemmissa tutkimuksissa on löydetty paljon merkkejä jäätä sisältävistä laattamaisista LDA-muodostumista ja laaksojen pohjia täyttävistä LVF-muodostumista [Squyres 1978, 1979] ja [Levy et al. 2010]. Kyseistä aluetta ei ole kuitenkaan aiemmin kartoitettu laaja-alaisesti uuden sukupolven avaruusluotaimien tuottamaa kuvamateriaalia hyödyntäen. Tämän työn päämääränä on ollut kartoittaa Protonilus Mensaen alue uuden sukupolven Mars Global Surveyor-, Mars Express-, Mars Reconnaissance Orbiter- ja Mars Odyssey-luotaimien tuottaman kuvamateriaalin avulla. Työssä on etsitty merkkejä mahdollisesti eri aikakausina toimineista jäätiköitymisprosesseista. Toisen mielenkiintoisen tutkimusaiheen muodostavat merkit veden virtauksesta alueella. Lisäksi tutkielmassa käydään läpi veden ja jään historiaa, koska niiden merkitys Marsin historiassa on koko ajan kasvanut. Tämän vuoksi on tärkeää käydä läpi, kuinka nykyinen käsityksemme Marsin vedestä on muodostunut. Tämän tutkielman myötä lukija saa kattavan käsityksen Marsin veden historiasta sekä nykyhetkestä. Tutkimuksen aineistona käytetään erityisesti Mars Odyssey-luotaimen Mola-instrumentin tuottamaa topografiatietoja sekä muiden luotaimien CTX-, HiRISE- ja HRSC-kameroiden tuottamaa kuvamateriaalia. Mars Reconnaissance Orbiter-luotaimen CTX-kameran tarkat ja hyvälaatuiset kuvat ovat toimineet kartoituksen pohjamateriaalina. CTX-instrumentin avulla Protonilus Mensaen aluetta voidaan tutkia noin kuuden metrin resoluutiolla. HiRISE- ja HRSC-kameroiden tarkempia ja yksityiskohtaisempia kuvia on käytetty alueilta, joista niitä on ollut saatavilla. Topografiatiedon avulla on mahdollista ymmärtää alueen jäätikkömäisten muodostumien liikettä sekä merkkejä veden virtauksesta. Tutkielman historiaosuudessa on käytetty hyväksi aiempien tutkimusryhmien tuloksia 1970-luvulta 2010-luvulle. Kartoituksessa pääasiallisena työkaluna on käytetty ArcGis-kartoitusohjelmaa, jonka avulla voidaan kartoittaa tehokkaasti laajoja alueita. Pienempiä alueita kartoitettaessa on käytetty myös Photoshop-kuvankäsittelyohjelmaa. Kartoituksessa Marsin Protonilus Mensaen alueelta löytyi paljon jäätikkömäisiä muodostumia. Laattamaiset LDA-muodostumat keskittyvät sirpaloituneelle ylänköalueelle ja Moreux-kraatterin keskuskohouman ympärille. Protonilus Mensae-alueen vuorien ympärille on muodostunut vaihtelevan kokoisia LDA-muodostumia. Tutkitulta alueelta löydetyt LVF-muodostumat keskittyvät sirpaloituneen ylänköalueen laaksoihin ja noaakkisella ylänköalueella vanhoihin virtausuomiin. Kraattereiden täytteitä eli CCF-muodostumia löytyy jokaisen kraatterin pohjalta. Noaakkiselta ylänköalueelta löydettiin yksi muinainen kraatterijärvi, josta on lähtenyt uoma kohti alempana sijaitsevia alueita. Jäätikkömäiset muodostumat ovat…

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mustonen, J. (. (2015). Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella. (Masters Thesis). University of Oulu. Retrieved from http://urn.fi/URN:NBN:fi:oulu-201504021200

Chicago Manual of Style (16^th Edition):

Mustonen, J (Juha). “Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella.” 2015. Masters Thesis, University of Oulu. Accessed March 02, 2021. http://urn.fi/URN:NBN:fi:oulu-201504021200.

MLA Handbook (7^th Edition):

Mustonen, J (Juha). “Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella.” 2015. Web. 02 Mar 2021.

Vancouver:

Mustonen J(. Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella. [Internet] [Masters thesis]. University of Oulu; 2015. [cited 2021 Mar 02]. Available from: http://urn.fi/URN:NBN:fi:oulu-201504021200.

Council of Science Editors:

Mustonen J(. Jäätikkömäiset muodostumat Moreux-kraatterin ja Protonilus Mensaen alueella. [Masters Thesis]. University of Oulu; 2015. Available from: http://urn.fi/URN:NBN:fi:oulu-201504021200

Boston University

8. Sanhueza, Patricio. Characterizing molecular clouds in the earliest phases of high-mass star formation.

Degree: PhD, Astronomy, 2015, Boston University

URL: http://hdl.handle.net/2144/15420

► High-mass stars play a key role in the energetics and chemical evolution of molecular clouds and galaxies. However, the mechanisms that allow the formation of… (more)

▼ High-mass stars play a key role in the energetics and chemical evolution of molecular clouds and galaxies. However, the mechanisms that allow the formation of high-mass stars are far less clear than those of their low-mass counterparts. Most of the research on high-mass star formation has focused on regions currently undergoing star formation. In contrast, objects in the earlier prestellar stage have been more difficult to identify. Recently, it has been suggested that the cold, massive, and dense Infrared Dark Clouds (IRDCs) host the earliest stages of high-mass star formation. The chemistry of IRDCs remains poorly explored. In this dissertation, an observational program to search for chemical variations in IRDC clumps as a function of their age is described. An increase in N2H+ and HCO+ abundances is found from the quiescent, cold phase to the protostellar, warmer phases, reflecting chemical evolution. For HCO+ abundances, the observed trend is consistent with theoretical predictions. However, chemical models fail to explain the observed trend of increasing N2H+ abundances. Pristine high-mass prestellar clumps are ideal for testing and constraining theories of high-mass star formation because their predictions differ the most at the early stages of evolution. From the initial IRDC sample, a high-mass clump that is the best candidate to be in the prestellar phase was selected (IRDC G028.23-00.19 MM1). With a new set of observations, the prestellar nature of the clump is confirmed. High-angular resolution observations of IRDC G028.23-00.19 suggest that in order to form high-mass stars, the detected cores have to accrete a large amount of material, passing through a low- to intermediate-mass phase before having the necessary mass to form a high-mass star. The turbulent core accretion model is inconsistent with this observational result, but on the other hand, the observations support the competitive accretion model. Embedded cores have to grow in mass during the star-formation process itself; the mass is not set at early times as the turbulent core accretion model predicts. The observed gas velocity dispersion in the cores is transonic and mildly supersonic, resulting in low virial parameters (neglecting magnetic fields). The turbulent core accretion model assumes highly supersonic linewidths and virial parameters sim1, inconsistent with the observations, unless magnetic fields in the cores have strengths of the order of 1 mG.

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Sanhueza, P. (2015). Characterizing molecular clouds in the earliest phases of high-mass star formation. (Doctoral Dissertation). Boston University. Retrieved from http://hdl.handle.net/2144/15420

Chicago Manual of Style (16^th Edition):

Sanhueza, Patricio. “Characterizing molecular clouds in the earliest phases of high-mass star formation.” 2015. Doctoral Dissertation, Boston University. Accessed March 02, 2021. http://hdl.handle.net/2144/15420.

MLA Handbook (7^th Edition):

Sanhueza, Patricio. “Characterizing molecular clouds in the earliest phases of high-mass star formation.” 2015. Web. 02 Mar 2021.

Vancouver:

Sanhueza P. Characterizing molecular clouds in the earliest phases of high-mass star formation. [Internet] [Doctoral dissertation]. Boston University; 2015. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/2144/15420.

Council of Science Editors:

Sanhueza P. Characterizing molecular clouds in the earliest phases of high-mass star formation. [Doctoral Dissertation]. Boston University; 2015. Available from: http://hdl.handle.net/2144/15420

9. McAdam, Margaret M. Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids.

Degree: 2018, University of Maryland, College Park

URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10623671

► This thesis investigates connections between low albedo asteroids and carbonaceous chondrite meteorites using spectroscopy. Meteorites and asteroids preserve information about the early solar system… (more)

▼ This thesis investigates connections between low albedo asteroids and carbonaceous chondrite meteorites using spectroscopy. Meteorites and asteroids preserve information about the early solar system including accretion processes and parent body processes active on asteroids at these early times. One process of interest is aqueous alteration. This is the chemical reaction between coaccreted water and silicates producing hydrated minerals. Some carbonaceous chondrites have experienced extensive interactions with water through this process. Since these meteorites and their parent bodies formed close to the beginning of the Solar System, these asteroids and meteorites may provide clues to the distribution, abundance and timing of water in the Solar nebula at these times. Chapter 2 of this thesis investigates the relationships between extensively aqueously altered meteorites and their visible, near and mid-infrared spectral features in a coordinated spectral-mineralogical study. Aqueous alteration is a parent body process where initially accreted anhydrous minerals are converted into hydrated minerals in the presence of coaccreted water. Using samples of meteorites with known bulk properties, it is possible to directly connect changes in mineralogy caused by aqueous alteration with spectral features. Spectral features in the mid-infrared are found to change continuously with increasing amount of hydrated minerals or degree of alteration. Building on this result, the degrees of alteration of asteroids are estimated in a survey of new asteroid data obtained from SOFIA and IRTF as well as archived the Spitzer Space Telescope data. 75 observations of 73 asteroids are analyzed and presented in Chapter 4. Asteroids with hydrated minerals are found throughout the main belt indicating that significant ice must have been present in the disk at the time of carbonaceous asteroid accretion. Finally, some carbonaceous chondrite meteorites preserve amorphous iron-bearing materials that formed through disequilibrium condensation in the disk. These materials are readily destroyed in parent body processes so their presence indicates the meteorite/asteroid has undergone minimal parent body processes since the time of accretion. Presented in Chapter 3 is the spectral signature of meteorites that preserve significant amorphous iron-bearing materials and the identification of an asteroid, (93) Minerva, that also appears to preserve these materials.

Subjects/Keywords: Astronomy

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APA (6^th Edition):

McAdam, M. M. (2018). Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids. (Thesis). University of Maryland, College Park. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10623671

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

McAdam, Margaret M. “Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids.” 2018. Thesis, University of Maryland, College Park. Accessed March 02, 2021. http://pqdtopen.proquest.com/#viewpdf?dispub=10623671.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

McAdam, Margaret M. “Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids.” 2018. Web. 02 Mar 2021.

Vancouver:

McAdam MM. Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids. [Internet] [Thesis]. University of Maryland, College Park; 2018. [cited 2021 Mar 02]. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10623671.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

McAdam MM. Water in the Early Solar System| Infrared Studies of Aqueously Altered and Minimally Processed Asteroids. [Thesis]. University of Maryland, College Park; 2018. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10623671

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

West Virginia University

10. Perera, Benetge Bhakthi Pranama. Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population.

Degree: PhD, Physics and Astronomy, 2013, West Virginia University

URL: https://doi.org/10.33915/etd.233 ; https://researchrepository.wvu.edu/etd/233

► The double pulsar, PSR J0737-3039A/B, is a unique binary system in which both neutron stars have been detected as radio pulsars. We analyze the evolution… (more)

▼ The double pulsar, PSR J0737-3039A/B, is a unique binary system in which both neutron stars have been detected as radio pulsars. We analyze the evolution of the radio emission from the second born, 2.8 s pulsar (pulsar B) based on five years of Green Bank Telescope data since 2003 December. We find that the pulse profile and the flux density of pulsar B change significantly over time, culminating in its radio emission disappearance towards our line of sight since 2008 March. Over this time, the flux density decreases dramatically and the pulse profile evolves from a single to a double peak. This profile shape evolution is likely caused by relativistic spin precession. We explain the profile evolution by an elliptical beam shape geometry model based on geodetic spin precession. By fitting for the observed pulse profile widths, the model constrains the geometry angles of pulsar B, namely the magnetic misalignment from the spin axis alphaB = 61 deg and the spin misalignment from the orbit normal thetaB = 138.5 deg, which are consistent with and similar to those derived by Breton et al. (2008) with a completely different geometry framework. The elliptical beam model predicts that the radio emission reappearance from pulsar B towards our line of sight is expected to happen between 2014 and 2035, with the variation depending on assumptions of the symmetry of the beam.;The strong stellar wind produced by the high spin-down luminosity of the first born, recycled, 23 ms pulsar (pulsar A) of the double pulsar system distorts the magnetosphere of its companion pulsar B. The wind-magnetosphere interaction model determines a bow-shock around pulsar B and it is likely the boundary of its magnetosphere. With geodetic spin precession, pulsar B provides an excellent opportunity to study different emission regions in the magnetosphere. Using the distorted magnetosphere and the well-defined geometrical parameters of pulsar B, we estimate the emission altitude to be ~20 neutron star radii in the bright orbital longitude regions. We further find that the emission altitude varies across the orbit due to the change in the orientation of the bow-shock with respect to our line of sight. Moreover, the emission altitude of pulsar B changes over time due to spin precession.;We then study the pulse profile variation of pulsar A. Analyzing more than six years of data, we confirm that pulsar A does not show a significant pulse width variation over time, which is consistent with previous works. Following a similar geometry framework as for pulsar B, we determine the geometry of pulsar A based on geodetic spin precession, including subtle changes of the pulse width at lower intensity levels from pulse peaks. By knowing the complete geometry of both pulsars, we construct the full geometrical configuration of the system. We find that the relative angle between the spin axes of the two pulsars varies periodically over time. This is the first time that this relative spin angle has been estimated for a double neutron star system.;Finally, we use Fermi… Advisors/Committee Members: Maura McLaughlin, Paul Cassak, Duncan Lorimer.

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Perera, B. B. P. (2013). Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population. (Doctoral Dissertation). West Virginia University. Retrieved from https://doi.org/10.33915/etd.233 ; https://researchrepository.wvu.edu/etd/233

Chicago Manual of Style (16^th Edition):

Perera, Benetge Bhakthi Pranama. “Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population.” 2013. Doctoral Dissertation, West Virginia University. Accessed March 02, 2021. https://doi.org/10.33915/etd.233 ; https://researchrepository.wvu.edu/etd/233.

MLA Handbook (7^th Edition):

Perera, Benetge Bhakthi Pranama. “Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population.” 2013. Web. 02 Mar 2021.

Vancouver:

Perera BBP. Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population. [Internet] [Doctoral dissertation]. West Virginia University; 2013. [cited 2021 Mar 02]. Available from: https://doi.org/10.33915/etd.233 ; https://researchrepository.wvu.edu/etd/233.

Council of Science Editors:

Perera BBP. Probes of pulsar emission physics: The double pulsar and the gamma-ray pulsar population. [Doctoral Dissertation]. West Virginia University; 2013. Available from: https://doi.org/10.33915/etd.233 ; https://researchrepository.wvu.edu/etd/233

University of Oulu

11. Nättilä, J. (Joonas). Mass and radius constraints for neutron stars using the cooling tail method.

Degree: 2013, University of Oulu

URL: http://urn.fi/URN:NBN:fi:oulu-201312041966

► Neutron stars (NS) are the most compact objects that can be directly observed. They can be used to study properties of matter at supranuclear densities.… (more)

▼ Neutron stars (NS) are the most compact objects that can be directly observed. They can be used to study properties of matter at supranuclear densities. This in turn gives us information to separate between numerous theoretical equations of states of dense matter. Thermonuclear (type-I) X-ray bursts from low mass X-ray binaries can be used to address this issue. Some of these bursts can be so energetic that they cause the whole photosphere of the NS to expand. The cooling of these photospheric radius expansion bursts can be compared to theoretical atmosphere models to obtain the mass and radius measurements of the NS. These measurements can then be used to differentiate between the different equations of state. We present a set of differential equations needed to compute these atmospheric models. We introduce an exact treatment of Compton scattering via the relativistic integral equation and an angle-dependent redistribution function. Using these equations, we can construct a set of atmosphere models in plane-parallel approximation in a local thermodynamical equilibrium for hot NSs. The emergent spectra is then fitted by a diluted blackbody to obtain the dilution factor w and the colour-correction factor f_c. On the other hand, the observed spectra from X-ray bursting neutron stars are close to thermal and can be fitted with a blackbody with two free parameters: the observed blackbody temperature T_bb and the normalization K. By equating the dilution factor w and the normalization K, we obtain a relation between the theoretical atmosphere models and the observations. This connection is the main idea of the so called cooling tail method. We then introduce a small correction to this method and discuss the consequences. A common problem encountered using this method is that different bursts from a given system can yield completely different mass and radius measurements. This fact casts a doubt on the robustness of the entire method. We study the burst emission from 4U 1608 – 52 at various persistent fluxes. We find a strong dependence of the burst properties on the flux before the burst. Bursts that ignite during the hard state at a low accretion rate show strong evolution of the apparent blackbody radius which is consistent with the model predictions of the neutron star atmosphere models. On the other hand, bursts occurring during the soft state at a higher accretion rate show constant apparent radius, which is inconsistent with the models. We then use the hard state bursts only to constrain the neutron star mass and radius from our set of sources. By taking only the physically relevant results into account, we also get information of the chemical composition of the atmosphere. This then gives us a way to conclude if the atmosphere is hydrogen- or helium-rich. After we know the chemical composition, we constrain the NS radius to be between 12 and 16 km. This implies a stiff equation of state of neutron star matter.

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Nättilä, J. (. (2013). Mass and radius constraints for neutron stars using the cooling tail method. (Masters Thesis). University of Oulu. Retrieved from http://urn.fi/URN:NBN:fi:oulu-201312041966

Chicago Manual of Style (16^th Edition):

Nättilä, J (Joonas). “Mass and radius constraints for neutron stars using the cooling tail method.” 2013. Masters Thesis, University of Oulu. Accessed March 02, 2021. http://urn.fi/URN:NBN:fi:oulu-201312041966.

MLA Handbook (7^th Edition):

Nättilä, J (Joonas). “Mass and radius constraints for neutron stars using the cooling tail method.” 2013. Web. 02 Mar 2021.

Vancouver:

Nättilä J(. Mass and radius constraints for neutron stars using the cooling tail method. [Internet] [Masters thesis]. University of Oulu; 2013. [cited 2021 Mar 02]. Available from: http://urn.fi/URN:NBN:fi:oulu-201312041966.

Council of Science Editors:

Nättilä J(. Mass and radius constraints for neutron stars using the cooling tail method. [Masters Thesis]. University of Oulu; 2013. Available from: http://urn.fi/URN:NBN:fi:oulu-201312041966

University of Oulu

12. Lesonen, J.-P. (Juho-Petteri). Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies.

Degree: 2017, University of Oulu

URL: http://urn.fi/URN:NBN:fi:oulu-201711043039

► In this thesis, the goal is to disentangle the real morphological evolution of galaxies from the observational effects, caused by redshift. This was done by… (more)

▼ In this thesis, the goal is to disentangle the real morphological evolution of galaxies from the observational effects, caused by redshift. This was done by taking a sample of ~1300 high-redshift (0.1 ≤ z ≤ 1.3) galaxies, observed with HST (Hubble Space telescope), from the GOODS-south field and then dividing them into six redshift bins of ∆z ≈ 0.2 and further into absolute magnitude bins of ∆M = 0.5. The sample was then matched to low-redshift (z ≤ 0.025) galaxies from the SDSS with the same comoving number density per ∆M-bin to create a sample of galaxies of the possible descendants of the high-redshift galaxies. Spectroscopic redshifts of the high-redshift sample were fetched from data provided by the 3DHST project. The low-redshift sample was then spatially scaled, dimmed and k-corrected to simulate redshift effects caused by the accelerating expansion of space. To appear as observed with the HST, the images were convolved with a new point-spread function (PSF), created by deconvolving the HST PSF with the SDSS PSF. This results in a change of the PSF 2D-distribution and a resolution change from 0.396”/pix (SDSS) to 0.03”/pix (HST). To achieve this the FERENGI and the KCORRECT codes were used. All three (low-redshift, high-redshift, redshifted) samples were then classified both visually and with CAS (concentration, asymmetry, smoothness) parameters. The results were compared between these samples. The redshifting process did not produce clumpy structures in the low-redshift galaxies as seen in real high-redshift galaxies. Visual classification becomes increasingly difficult for z ≥ 0.55. The concentration index hardly changes with redshift. The asymmetry of the high-redshift galaxies seem to be genuinely higher than that of the low-redshift galaxies. The smoothness parameter values increase with redshift, implying an increasing clumpiness, but some of the change could be due to the redshift effects. For the high-redshift sample, all the CAS parameters between redshift bins show very little evolution for a given morphological type and could be used to differentiate between them. We also note that we found a significant amount of “clumpy” galaxy types, already in the nearest redshift bin of 0.1 ≤ z ≤ 0.3, as opposed to previous studies.

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lesonen, J. -. (. (2017). Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies. (Masters Thesis). University of Oulu. Retrieved from http://urn.fi/URN:NBN:fi:oulu-201711043039

Chicago Manual of Style (16^th Edition):

Lesonen, J -P (Juho-Petteri). “Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies.” 2017. Masters Thesis, University of Oulu. Accessed March 02, 2021. http://urn.fi/URN:NBN:fi:oulu-201711043039.

MLA Handbook (7^th Edition):

Lesonen, J -P (Juho-Petteri). “Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies.” 2017. Web. 02 Mar 2021.

Vancouver:

Lesonen J-(. Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies. [Internet] [Masters thesis]. University of Oulu; 2017. [cited 2021 Mar 02]. Available from: http://urn.fi/URN:NBN:fi:oulu-201711043039.

Council of Science Editors:

Lesonen J-(. Morphological study of 0.1 ≤ z ≤ 1.3 galaxies:comparison to artificially redshifted local galaxies. [Masters Thesis]. University of Oulu; 2017. Available from: http://urn.fi/URN:NBN:fi:oulu-201711043039

University of Cape Town

13. Tekola, Abiy G. On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies.

Degree: Image, Astronomy, 2011, University of Cape Town

URL: http://hdl.handle.net/11427/11499

► This thesis, entitled "On evolution of star forming galaxies: the metallicity of dwarfs and the effect of environment on local luminous infrared galaxies" is divided… (more)

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Tekola, A. G. (2011). On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/11499

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Tekola, Abiy G. “On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies.” 2011. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/11499.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Tekola, Abiy G. “On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies.” 2011. Web. 02 Mar 2021.

Vancouver:

Tekola AG. On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies. [Internet] [Thesis]. University of Cape Town; 2011. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/11499.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Tekola AG. On the evolution of star forming galaxies : the metallicity of dwarfs and the effect of environment on local luminous IR galaxies. [Thesis]. University of Cape Town; 2011. Available from: http://hdl.handle.net/11427/11499

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

14. Sorgho, Amidou. Deep HI observations of nearby late-type galaxies.

Degree: PhD, Astronomy, 2019, University of Cape Town

URL: http://hdl.handle.net/11427/31122

► This thesis makes use of sensitive Hi observations to map the distribution and kinematics of the low column density neutral hydrogen in late-type nearby mostly… (more)

▼ This thesis makes use of sensitive Hi observations to map the distribution and kinematics of the low column density neutral hydrogen in late-type nearby mostly isolated galaxies and in the nearby M81 group. Using the KAT-7, GBT and MeerKAT AR1 telescopes, we present in the second chapter a survey of the Hi in a sample of twenty nearby, mostly isolated galaxies down to low column density levels. This provided a new Hi view of some of these galaxies, which allowed to derive their kinematics out to unprecedented extents. Despite the short spacings of KAT-7 and MeerKAT AR1, and the large size of the single-dish GBT that make these telescopes ideal for detecting faint structures, the observations revealed no clear detection of low column density Hi clouds down to a typical sensitivity of ∼2.2 × 1018 cm−2 that could be associated to gas accretion in the observed galaxies. However, we do not discard the existence of such structures that, we note, could be in the form of discrete clouds smaller than the beam size of the telescopes. In the third chapter, we use the DRAO telescope to perform a sensitive survey of the Hi in a 5 ◦ × 5 ◦ area of the M81 group. Similarly to previous observations, we find that the three major and interacting galaxies of the group – M81, M82 and NGC 3077 – are connected through Hi bridges and intergalactic Hi clouds. One of the major findings of the survey is the more complete map of the western Hi arm connecting the three galaxies to the dwarf galaxy NGC 2976. These observations offer enough resolution to map the structure of the arm, and reveal a complex of small clouds filling the space between the arm and the Hi forming “main body” of the interacting galaxies. Using a tilted-ring model, we also construct a large-scale rotation curve of the system formed by the interacting galaxies. Consistently with the large-scale velocity field, we observe a flat trend for the rotation velocity of the system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. The fourth chapter focuses on a subset of the M81 survey containing the dwarf galaxy IC 2574 and the Hi complex HIJASS J1021+68. In this chapter we perform a thorough analysis of the distribution and kinematics of the Hi in the two systems, and thanks to the high sensitivity we are able to detect a substantially large amount of low column density Hi around IC 2574, in the form of an Hi envelope, and in two large concentrations around the galaxy. We find evidence that HIJASS J1021+68 – which is found to be connected to IC 2574 through a filament of discrete clouds – is not a dark galaxy as previously suggested, but is instead a complex of clouds either stripped from, or falling onto the primordial Hi envelope of IC 2574. The kinematical analysis of IC 2574 using a 3D tilted-ring model brings us to derive its rotation curve out to a larger extent than previous works and allows us to constrain its Dark Matter halo parameters, which we find consistent with the literature.… Advisors/Committee Members: Carignan, Claude (advisor).

Subjects/Keywords: astronomy

Record Details Similar Records Cite « Share

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sorgho, A. (2019). Deep HI observations of nearby late-type galaxies. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/31122

Chicago Manual of Style (16^th Edition):

Sorgho, Amidou. “Deep HI observations of nearby late-type galaxies.” 2019. Doctoral Dissertation, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/31122.

MLA Handbook (7^th Edition):

Sorgho, Amidou. “Deep HI observations of nearby late-type galaxies.” 2019. Web. 02 Mar 2021.

Vancouver:

Sorgho A. Deep HI observations of nearby late-type galaxies. [Internet] [Doctoral dissertation]. University of Cape Town; 2019. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/31122.

Council of Science Editors:

Sorgho A. Deep HI observations of nearby late-type galaxies. [Doctoral Dissertation]. University of Cape Town; 2019. Available from: http://hdl.handle.net/11427/31122

University of Cape Town

15. Randriamanakoto, Rojovola Zara-Nomena. Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies.

Degree: Image, Astronomy, 2015, University of Cape Town

URL: http://hdl.handle.net/11427/15766

► Super star clusters (SSCs) represent the youngest and most massive form of known gravitationally bound star clusters in the Universe. They are born abundantly in… (more)

Subjects/Keywords: Astronomy

Record Details Similar Records Cite « Share

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Randriamanakoto, R. Z. (2015). Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/15766

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Randriamanakoto, Rojovola Zara-Nomena. “Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies.” 2015. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/15766.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Randriamanakoto, Rojovola Zara-Nomena. “Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies.” 2015. Web. 02 Mar 2021.

Vancouver:

Randriamanakoto RZ. Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies. [Internet] [Thesis]. University of Cape Town; 2015. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/15766.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Randriamanakoto RZ. Formation of young massive star clusters: a high-resolution multi-wavelength study of intensely star-formation galaxies. [Thesis]. University of Cape Town; 2015. Available from: http://hdl.handle.net/11427/15766

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

16. Sorgho, Amidou. Deep HI observations of nearby late-type galaxies.

Degree: PhD, Astronomy, 2019, University of Cape Town

URL: http://hdl.handle.net/11427/31121

► This thesis makes use of sensitive Hi observations to map the distribution and kinematics of the low column density neutral hydrogen in late-type nearby mostly… (more)

▼ This thesis makes use of sensitive Hi observations to map the distribution and kinematics of the low column density neutral hydrogen in late-type nearby mostly isolated galaxies and in the nearby M81 group. Using the KAT-7, GBT and MeerKAT AR1 telescopes, we present in the second chapter a survey of the Hi in a sample of twenty nearby, mostly isolated galaxies down to low column density levels. This provided a new Hi view of some of these galaxies, which allowed to derive their kinematics out to unprecedented extents. Despite the short spacings of KAT-7 and MeerKAT AR1, and the large size of the single-dish GBT that make these telescopes ideal for detecting faint structures, the observations revealed no clear detection of low column density Hi clouds down to a typical sensitivity of ∼2.2 × 1018 cm−2 that could be associated to gas accretion in the observed galaxies. However, we do not discard the existence of such structures that, we note, could be in the form of discrete clouds smaller than the beam size of the telescopes. In the third chapter, we use the DRAO telescope to perform a sensitive survey of the Hi in a 5 ◦ × 5 ◦ area of the M81 group. Similarly to previous observations, we find that the three major and interacting galaxies of the group – M81, M82 and NGC 3077 – are connected through Hi bridges and intergalactic Hi clouds. One of the major findings of the survey is the more complete map of the western Hi arm connecting the three galaxies to the dwarf galaxy NGC 2976. These observations offer enough resolution to map the structure of the arm, and reveal a complex of small clouds filling the space between the arm and the Hi forming “main body” of the interacting galaxies. Using a tilted-ring model, we also construct a large-scale rotation curve of the system formed by the interacting galaxies. Consistently with the large-scale velocity field, we observe a flat trend for the rotation velocity of the system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. The fourth chapter focuses on a subset of the M81 survey containing the dwarf galaxy IC 2574 and the Hi complex HIJASS J1021+68. In this chapter we perform a thorough analysis of the distribution and kinematics of the Hi in the two systems, and thanks to the high sensitivity we are able to detect a substantially large amount of low column density Hi around IC 2574, in the form of an Hi envelope, and in two large concentrations around the galaxy. We find evidence that HIJASS J1021+68 – which is found to be connected to IC 2574 through a filament of discrete clouds – is not a dark galaxy as previously suggested, but is instead a complex of clouds either stripped from, or falling onto the primordial Hi envelope of IC 2574. The kinematical analysis of IC 2574 using a 3D tilted-ring model brings us to derive its rotation curve out to a larger extent than previous works and allows us to constrain its Dark Matter halo parameters, which we find consistent with the literature.… Advisors/Committee Members: Carignan, Claude (advisor).

Subjects/Keywords: astronomy

Record Details Similar Records Cite « Share

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Sorgho, A. (2019). Deep HI observations of nearby late-type galaxies. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/31121

Chicago Manual of Style (16^th Edition):

Sorgho, Amidou. “Deep HI observations of nearby late-type galaxies.” 2019. Doctoral Dissertation, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/31121.

MLA Handbook (7^th Edition):

Sorgho, Amidou. “Deep HI observations of nearby late-type galaxies.” 2019. Web. 02 Mar 2021.

Vancouver:

Sorgho A. Deep HI observations of nearby late-type galaxies. [Internet] [Doctoral dissertation]. University of Cape Town; 2019. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/31121.

Council of Science Editors:

Sorgho A. Deep HI observations of nearby late-type galaxies. [Doctoral Dissertation]. University of Cape Town; 2019. Available from: http://hdl.handle.net/11427/31121

17. Randriamampandry, Toky Herimandimby. Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar.

Degree: Image, Astronomy, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/25430

► The mass distribution of disk galaxies is usually determined through the use of rotation curves. This determination relies on two key assumptions; that the gas… (more)

▼ The mass distribution of disk galaxies is usually determined through the use of rotation curves. This determination relies on two key assumptions; that the gas moves on circular orbits and that this motion traces the underlying gravitational potential. In the case of barred spiral galaxies the first assumption is false as the bar induces non-circular streaming motions in the gas. Therefore, the rotation curves of barred galaxies need to be corrected for the non-circular motions before being used for mass model analysis. In this dissertation, we use numerical simulations to quantify and correct for the non-circular flows induced by a bar. The aim is to investigate and quantify the effect of the bar properties on the amplitude of the non-circular motions. This is done by comparing the observational data such as rotation curves and bar properties with the kinematics and bar properties obtained from mocked galaxies. In chapter III, we examine the performance of ROTCUR and DISKFIT for deriving rotation curves from velocity maps of barred spiral galaxies using mock observations. Our results confirm that ROTCUR under-/overestimates measured rotation curves if the bar is aligned with one of the symmetry axes. The DISKFIT algorithm, which is specifically designed for barred galaxies only works for galaxies of intermediate bar orientations. In chapter IV, we quantify the magnitude of the non-circular flows and constraint the range of bar orientation angles where DiskFit fails by using Tree-SPH simulations from the GalMer database by Chilingarian et al . (2010 ). We found that the rotation curve obtained from ROTCUR was 40% smaller/larger than the expected velocities calculated from the gravitational potential when the bar is aligned with the major/minor axis. For the DISKFIT analysis, we found that DiskFit produces unrealistic values for all the models when the bar is within ten degrees of the symmetry axes. New hydrodynamic simulations of three disc galaxies (NGC 1300 , NGC 1530 and NGC 3621 ) are presented in chapter IV. Our objective is to create more realistic simulated galaxies that replicate the bar properties and velocity elds of the galaxies of our sample. The initial conditions for our simulations are determined through a Bayesian analysis of the azimuthally averaged rotation curve, the stellar surface brightness, and the gas surface density. The parameters posterior distribution functions (PDFs) combine with the disc stability parameters PDFs are used as criterion to select the model parameters. The velocities of the gas particles are transformed into velocity maps and compared with the observed galaxies. We are able to reproduce the bar properties and kinematics of the three galaxies in our sample. These findings imply that a tailored simulation is an effective way of investigating non-circular flows in disc galaxies especially when the bar orientation is close to the minor or major kinematical axis of the galaxy. Advisors/Committee Members: Carignan, Claude (advisor).

Subjects/Keywords: Astronomy

10 more images…

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APA (6^th Edition):

Randriamampandry, T. H. (2017). Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/25430

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Randriamampandry, Toky Herimandimby. “Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar.” 2017. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/25430.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Randriamampandry, Toky Herimandimby. “Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar.” 2017. Web. 02 Mar 2021.

Vancouver:

Randriamampandry TH. Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/25430.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Randriamampandry TH. Correcting the rotation curve of spiral galaxies for the non-circular motions induced by a bar. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/25430

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

18. Aydi, Elias. Multiwavelength studies of classical novae.

Degree: PhD, Astronomy, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/29576

► Classical novae are transient astronomical events resulting from an eruption on the surface of an accreting white dwarf in interacting binary stars, namely cataclysmic variables.… (more)

▼ Classical novae are transient astronomical events resulting from an eruption on the surface of an accreting white dwarf in interacting binary stars, namely cataclysmic variables. These eruptions and their progenitors are ideal astronomical events/objects to study a variety of interesting topics, such as mass-transfer mechanisms, binary evolution, and thermonuclear and radiative emission processes. Novae share some general observational characteristics during their eruption phases, yet each nova is new and can show unique light-curve and spectral developments. Therefore, carrying out detailed multiwavelength studies of individual novae is important to provide an holistic picture of the eruption development with the ultimate aim of a general understanding of the physical mechanisms involved in nova eruptions, as well as the structure and evolutionary condition of their progenitors. This dissertation presents detailed multiwavelength studies of three nova events, namely V5852 Sgr, SMCN 2016-10, and V407 Lup, as a series of chapters (papers). Our data were collected using several ground-based and space telescopes including: high- and mediumresolution optical spectroscopy from SALT, SOAR, and FLOYDS, optical and near-infrared photometry from IRSF, OGLE and SMARTS, UV and X-ray data from Swift, Chandra, and XMM-Newton. In the second chapter, we present an optical and infrared study of the unusual nova V5852 Sgr. This nova is a moderately fast nova showing features of the Fe II spectroscopic type. The light-curve development is unique, showing a combination of several light-curve classes. Estimates of the distance and measurements of the line velocities suggest that the nova might be associated with the Sagittarius stream. If so, it would be the first nova to be discovered in a dwarf spheroidal galaxy. The third chapter presents a multiwavelength study of the very fast nova SMCN 2016-10a. The fast light-curve development suggests that the system hosts a massive white dwarf (& 1.25 M), in good agreement with the high temperature of the super-soft X-ray emission and the turn-on/turn-off time of the super-soft state. At the distance of the Small Magellanic Cloud our measurements suggest that SMCN 2016-10a is the brightest nova in the Small Magellanic Cloud and one of the brightest novae on record, with an absolute maximum magnitude of ∼ −10.5 in the V -band. Chapter four is a multiwavelength study of nova V407 Lup. With a light-curve decline time t2 ≤ 2.9 d, this is one of the fastest known examples and the white dwarf is possibly more massive than 1.25 M. Our set of optical, UV, and X-ray data suggest that this system is an intermediate-polar cataclysmic variable based essentially on the presence of two periodicities (3.57 h and 565 s) in the light-curves. These periodicities are attributed to the orbital period of the binary and rotational period of the white dwarf. The late optical spectra (taken from day 165 post-eruption) show narrow and moving lines of He II and O VI, possibly associated with accretion regions within the… Advisors/Committee Members: Mohamed, Shazrene (advisor), Whitelock, Patricia (advisor).

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Aydi, E. (2018). Multiwavelength studies of classical novae. (Doctoral Dissertation). University of Cape Town. Retrieved from http://hdl.handle.net/11427/29576

Chicago Manual of Style (16^th Edition):

Aydi, Elias. “Multiwavelength studies of classical novae.” 2018. Doctoral Dissertation, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/29576.

MLA Handbook (7^th Edition):

Aydi, Elias. “Multiwavelength studies of classical novae.” 2018. Web. 02 Mar 2021.

Vancouver:

Aydi E. Multiwavelength studies of classical novae. [Internet] [Doctoral dissertation]. University of Cape Town; 2018. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/29576.

Council of Science Editors:

Aydi E. Multiwavelength studies of classical novae. [Doctoral Dissertation]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/29576

University of Cape Town

19. Ramphul, Rajin Anand. Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT).

Degree: Image, Astronomy, 2018, University of Cape Town

URL: http://hdl.handle.net/11427/28380

► Context: Stellar population modelling is a popular technique that has been extensively applied to main sequence galaxies. Yet starburst galaxies and Luminous InfraRed Galaxies (LIRGs)… (more)

▼ Context: Stellar population modelling is a popular technique that has been extensively applied to main sequence galaxies. Yet starburst galaxies and Luminous InfraRed Galaxies (LIRGs) have, so far, not been studied as much using the method. LIRGs in the local universe are known to be highly interacting galaxies with strong star formation in obscured environments. Still, LIRGs also have diversity in terms of morphology and mode and location of star formation. Aim: This thesis investigates the stellar population properties of a group of 52 starbursts and luminous infrared galaxies (LIRGs) in the local universe that forms part of the SUperNovae and starBurst in the InfraReD (SUNBIRD) survey. The galaxies in a distance range of 3.5 < Dl < 280 Mpc and infrared luminosity of 10.30 < LIR < 11.91 L were observed with the Southern African Large Telescope in long-slit spectroscopy mode. Method: The stellar populations of the galaxies are derived by fitting Bruzual & Charlot (2003) templates to the reduced spectra using STARLIGHT software with a Monte Carlo method implemented to recover uncertainties on age, metallicity and extinction. The derived stellar population models are then subtracted from the observed spectra to produce emission spectra from which emission line fluxes are measured. Both integrated spectra and spatially resolved apertures are extracted to be analysed in this work. Results: The light-weighted and mass weighted age of the sample is found to be 160 Myr and 7.2 Gyr respectively. The star formation history of the sample shows a rise of activity in the past ∼ 50 Myr and with a jump of an order of magnitude in the past 3 Myr. Analysis of the stellar metallicity hints at inflow of pristine gas, which decreases the observed metallicity content as well as ignites SF-activity. Analysis of the oxygen abundances shows that while LIRGs and SF galaxies are under abundant, their under-abundance may have previously been over-estimated as compared to main sequence galaxies. The radial age profile of the sample is flat, similar to that of late-type Sd galaxies. Interaction is found to cause a drop in the age of apertures although the post-merging stages shows continued star forming activity in the nuclear region. The stellar metallicity gradient is found to be −0.029 ± 0.018 dex/kpc, comparable to Sb or Sbc galaxies favouring an inside-out formation scenario for the galaxies. As interaction stage increases, both age and metallicity gradients are seen to get flatter, eventually getting slightly positive. The more active interaction stages are HII driven, while isolated and post merging stages shows higher AGN activity. The current work offers an update on the abundances of IR dominated galaxies from the previous work done by Rupke et al. (2008). The formation scenario of our LIRGs in the local universe is shown to be in line with the scenario put forward by Hopkins et al. (2008). Future works with medium resolution spectra acquired during the course of this thesis should allow for detection of gas inflows and better… Advisors/Committee Members: Vaisanen, Petri (advisor), van Der Heyden, Kurt (advisor).

Subjects/Keywords: astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Ramphul, R. A. (2018). Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT). (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/28380

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Ramphul, Rajin Anand. “Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT).” 2018. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/28380.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Ramphul, Rajin Anand. “Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT).” 2018. Web. 02 Mar 2021.

Vancouver:

Ramphul RA. Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT). [Internet] [Thesis]. University of Cape Town; 2018. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/28380.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Ramphul RA. Characterising star forming and luminous infrared galaxies with the Southern African Large Telescope (SALT). [Thesis]. University of Cape Town; 2018. Available from: http://hdl.handle.net/11427/28380

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

20. Spark, Mellony. Exploring the application of new telescope technologies in the testing of dwarf novae accretion models.

Degree: Image, Astronomy, 2011, University of Cape Town

URL: http://hdl.handle.net/11427/11037

In this thesis I investigate emerging telescope technologies and demonstrate, within the context of accretion in cataclysmic variables (CVs), their role in contributing to the stellar variability studies which help drive their development. Advisors/Committee Members: Donoghue, Darragh O' (advisor).

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Spark, M. (2011). Exploring the application of new telescope technologies in the testing of dwarf novae accretion models. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/11037

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Spark, Mellony. “Exploring the application of new telescope technologies in the testing of dwarf novae accretion models.” 2011. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/11037.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Spark, Mellony. “Exploring the application of new telescope technologies in the testing of dwarf novae accretion models.” 2011. Web. 02 Mar 2021.

Vancouver:

Spark M. Exploring the application of new telescope technologies in the testing of dwarf novae accretion models. [Internet] [Thesis]. University of Cape Town; 2011. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/11037.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Spark M. Exploring the application of new telescope technologies in the testing of dwarf novae accretion models. [Thesis]. University of Cape Town; 2011. Available from: http://hdl.handle.net/11427/11037

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

21. Mogotsi, Keoikantse Moses. The star formation and dynamics of nearby galaxies.

Degree: Image, Astronomy, 2016, University of Cape Town

URL: http://hdl.handle.net/11427/22855

► A scaling relation between the surface density of star formation and gas in the disks of galaxies has become the basis of our understanding of… (more)

▼ A scaling relation between the surface density of star formation and gas in the disks of galaxies has become the basis of our understanding of extragalactic star formation on scales of hundreds of parsecs and larger. This is an empirical law but star formation is a complex process - the presence of gas at sufficiently high densities to collapse and form stars depends on a wide variety of physical processes. These processes can be thought of in terms of the stability of galaxy disks, which is a balance between the gravitational force and competing forces such as the outward force due to pressure. In this study I explore how star formation is related to galaxy dynamics in the central regions of galaxies. This is done by determining the dominant contributor to the inner dynamics of galaxies and developing star formation models based on self-regulating disks that maintain a constant sub-critical stability parameter. Stability parameters for a gas-only disk and a two- uid disk containing both gas and stars are considered. These models are tested in the central regions of a sample of galaxies with a wide range of Hi masses, sizes, morphologies and stellar masses. The analysis is performed using Hα integral field spectroscopy, R-band, narrowband Hα, and near-infrared photometry to determine the star formation rates and kinematics of the galaxies. In agreement with previous studies I find that the central stellar surface density is tightly correlated with the central velocity gradient, which traces the steepness of the inner gravitational well. The baryonic fractions found in the analysis suggest that baryons dominate the central density of most galaxies in the sample, but better constraints on these are needed to make more firm conclusions. There are correlations between the star formation surface density and velocity gradient, however the observed relations do not match predictions from the models. Tests suggest that the failure of the models is due to the implied stability parameters in the galaxy centers not being constant across the galaxy sample, and that the star formation laws used in the analysis may not hold over the full parameter space of the sample. Advisors/Committee Members: Carignan, Claude (advisor), Meurer, G R (advisor), De Blok, W J G (advisor).

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Mogotsi, K. M. (2016). The star formation and dynamics of nearby galaxies. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/22855

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Mogotsi, Keoikantse Moses. “The star formation and dynamics of nearby galaxies.” 2016. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/22855.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Mogotsi, Keoikantse Moses. “The star formation and dynamics of nearby galaxies.” 2016. Web. 02 Mar 2021.

Vancouver:

Mogotsi KM. The star formation and dynamics of nearby galaxies. [Internet] [Thesis]. University of Cape Town; 2016. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/22855.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Mogotsi KM. The star formation and dynamics of nearby galaxies. [Thesis]. University of Cape Town; 2016. Available from: http://hdl.handle.net/11427/22855

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

22. Rajoelimanana, Andry Fitiavana. Long-term properties of X-ray binaries in the magellanic clouds.

Degree: Image, Astronomy, 2013, University of Cape Town

URL: http://hdl.handle.net/11427/4405

► Long-term variability in all types of X-ray binaries is a well established characteristic, but due to observation limitations and lack of long-term monitoring capability these… (more)

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Rajoelimanana, A. F. (2013). Long-term properties of X-ray binaries in the magellanic clouds. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/4405

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Rajoelimanana, Andry Fitiavana. “Long-term properties of X-ray binaries in the magellanic clouds.” 2013. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/4405.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Rajoelimanana, Andry Fitiavana. “Long-term properties of X-ray binaries in the magellanic clouds.” 2013. Web. 02 Mar 2021.

Vancouver:

Rajoelimanana AF. Long-term properties of X-ray binaries in the magellanic clouds. [Internet] [Thesis]. University of Cape Town; 2013. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/4405.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Rajoelimanana AF. Long-term properties of X-ray binaries in the magellanic clouds. [Thesis]. University of Cape Town; 2013. Available from: http://hdl.handle.net/11427/4405

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

23. Kotze, Enrico Juan. Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables.

Degree: Image, Astronomy, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/25356

► Doppler tomography has revolutionised the interpretation of phase-resolved spectra of interacting binaries. The standard technique extracts emission and kinematic information contained in such spectra and… (more)

▼ Doppler tomography has revolutionised the interpretation of phase-resolved spectra of interacting binaries. The standard technique extracts emission and kinematic information contained in such spectra and projects it onto a two-dimensional velocity coordinate frame. This thesis describes my investigation of constructing Doppler tomograms in 'inside-out' coordinates by reversing the velocity axis. The aim was to determine if the emission distribution in the inside-out tomogram is more intuitive to interpret than the standard tomogram, and if it reveals indiscernible or enhances less discernible details. The inside-out tomogram is constructed by projecting the spectra onto the inside-out coordinate frame with zero velocity transposed to the outer circumference and the maximum velocities to the centre of the tomogram. In addition, this thesis describes a new flux modulation mapping technique applied to the standard and inside-out Doppler tomography of magnetic cataclysmic variables. I developed this technique with the aim to obtain more information from their observed spectra and present it in a useful format. It extracts the flux modulation from consecutive half-phase tomograms and constructs maps of the amplitude and phasing characteristics of the modulation in these systems. My investigation, involving the spectra of non-magnetic and magnetic cataclysmic variables, shows that the inside-out projection redistributes the relative contrast levels in and amongst the emission components. The inside-out projection exposes low-velocity emission details which are overly compacted and enhances high-velocity emission details which are overly tenuous in the standard projection. In addition, the flux modulation mapping technique gives a significant improvement in reproducing the input spectra adding more confidence in the interpretation of the modulation maps. Notable results were obtained for the polars where the blob-like low-velocity emission in their standard tomograms is more exposed in their inside-out tomograms, making it easier to distinguish between the ballistic and magnetic accretion flows that are evident in their trailed spectra. Also, for all the polars investigated the high-velocity magnetic accretion flows not seen in their standard tomograms are revealed in their inside-out tomograms. This extra information is extremely valuable to form a more complete picture of the emission components, broadening our knowledge of the accretion dynamics in these systems. Advisors/Committee Members: McBride, Vanessa A (advisor), Potter, Stephen B (advisor).

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kotze, E. J. (2017). Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/25356

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Kotze, Enrico Juan. “Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables.” 2017. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/25356.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Kotze, Enrico Juan. “Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables.” 2017. Web. 02 Mar 2021.

Vancouver:

Kotze EJ. Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/25356.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kotze EJ. Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/25356

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

24. Mutabazi, Tom. The distance to the Norma cluster and its relation to the great attractor region.

Degree: Image, Astronomy, 2015, University of Cape Town

URL: http://hdl.handle.net/11427/15742

► The Local Group's peculiar motion with respect to the cosmic microwave background has been measured with high precision and found to be ~627±22 km s-1,… (more)

▼ The Local Group's peculiar motion with respect to the cosmic microwave background has been measured with high precision and found to be ~627±22 km s-1, but the source of this motion is not clear. Studies to constrain the fractional contribution of the local mass overdensity, particularly in the Great Attractor region and the more distant Shapley Supercluster, remain contradictory. This work is an attempt to disentangle these contributions by measuring a redshift-independent distance to the Norma cluster, which lies at, or close to, the core of the Great Attractor, in order to determine its peculiar velocity. A reliable measurement of the distance and peculiar velocity of Norma will help clarify the velocity flows in the Great Attractor region. The challenge is with observing in the Zone of Avoidance since star crowding and Galactic extinction effects are severe at such low Galactic latitudes. High quality near-infrared images have been used in the photometric analysis for the Norma cluster sample so as to minimise the effect of Galactic extinction. In addition, the imaging cameras used have a small pixel scale resulting in well resolved images for reliable foreground star-subtraction hence accurate photometry. In order to determine the redshift-independent distance, I applied two independent, complemen- tary methods: the Fundamental Plane and the Tully-Fisher relations. The redshift-independent distance and the peculiar velocity of the Norma cluster were measured using 1) the Ks-band Fundamental Plane analysis for 31 galaxies using the 3.6m New Technology Telescope (NTT) at the European Southern Observatory (ESO) 2) the J- and Ks-band Fundamental Plane analysis for 31 galaxies using the Japanese 1.4 m InfraRed Survey Facility (IRSF) at the South African Astronomical Observatory (SAAO) 3) the combined NTT and IRSF Ks-band Fundamental Plane analysis for 41 galaxies 4) the Ks-band Tully-Fisher analysis for 12 galaxies using near-infrared images from the IRSF and HI profiles obtained from the 64-m Parkes radio telescope. Advisors/Committee Members: Blyth, Sarah-Louise (advisor), Woudt, Patrick A (advisor).

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Mutabazi, T. (2015). The distance to the Norma cluster and its relation to the great attractor region. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/15742

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Mutabazi, Tom. “The distance to the Norma cluster and its relation to the great attractor region.” 2015. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/15742.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Mutabazi, Tom. “The distance to the Norma cluster and its relation to the great attractor region.” 2015. Web. 02 Mar 2021.

Vancouver:

Mutabazi T. The distance to the Norma cluster and its relation to the great attractor region. [Internet] [Thesis]. University of Cape Town; 2015. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/15742.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Mutabazi T. The distance to the Norma cluster and its relation to the great attractor region. [Thesis]. University of Cape Town; 2015. Available from: http://hdl.handle.net/11427/15742

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Cape Town

25. Ramatsoku, Mpati Analicia. A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance.

Degree: Image, Astronomy, 2017, University of Cape Town

URL: http://hdl.handle.net/11427/27351

► In this thesis we study a structure associated with the Perseus-Pisces Supercluster (PPS; cz ~ 6000 km s⁻¹), where it crosses the Zone of Avoidance… (more)

▼ In this thesis we study a structure associated with the Perseus-Pisces Supercluster (PPS; cz ~ 6000 km s⁻¹), where it crosses the Zone of Avoidance (ZoA) at the Galactic longitude of ℓ ≈ 160ᵒ. This largely unexplored region contains the X-ray emitting 3C 129 cluster which hosts two strong radio sources with bent morphologies, thus indicative of a rich intra-cluster medium (ICM). Due to its low Galactic latitude of b = 0.27, where Galactic extinction is severe at optical wavelengths (AB = 1.8 − 8.0), the details of its galaxy population and dynamics had not been investigated in detail before. Additionally, the diverse and dynamic cosmic environments of the PPS with the embedded galaxy cluster make this region an ideal laboratory to study the effects on these environments on the galaxy properties and galaxy transformation processes therein. We used the Westerbork Synthesis Radio Telescope (WSRT) to blindly map this ZoA crossing of the PPS in the 21 cm HI-wavelength. This was conducted through 35 individual pointings observed for a total of 420 hours, covering a large area of about 9.6 sq.deg and a velocity range of approximately cz ~ 2000− 16000 km s⁻¹, thus mapping the immediate surrounding regions to enable investigations of the various cosmic environmental effects on the HI properties of galaxies. With the resulting spectral line data cubes of an angular resolution of 23" x 16" and a velocity resolution of 16.5 km s⁻¹ with a rms sensitivity of ~ 0.4 mJy/beam, we detect 211 galaxies within the entire surveyed volume. These new HI detections reveal a total of four distinct overdensities. Of these overdensities, the two major ones are located at the distance of the PPS at cz ~ 4000 − 8000 km s⁻¹ and behind it at cz ~ 8000 − 12000 km s−1. The galaxy overdensity associated with the PPS is used to demonstrate how this supercluster connects across the ZoA and confirms earlier indications of a filamentary connection between Perseus, Pisces and the A569 clusters through this region of the sky. Galaxies in the background of the PPS seem to be part of the CID15 structure that had been earlier predicted in the reconstructed density and velocity maps from the 2MASS Redshift Survey. We carry out a detailed census of the galaxy population in the 3C129 cluster by combining the HI-data of the gas-rich galaxies with the near-infrared (NIR) images of the gas-poor galaxies. The NIR galaxies are identified from the high resolution (0.2"/pix, seeing ~0.8") images of the UKIDSS Galactic Plane Survey. We obtain photometry in the J,H and K bands for about 9700 galaxies identified in the NIR images within the WSRT HI surveyed area. These measurements are used to derive the red-sequence of this cluster through the (J − K) vs K colour-magnitude diagram to identify the gas-poor cluster member candidates. Within the spatial extent of the cluster of radius ~ 1.7 Mpc, a total of 261 galaxies are identified as cluster members, with 23 detected in HI. An assessment of the morphologies of these galaxy members reveals a clear morphological… Advisors/Committee Members: Kraan-Korteweg, Renée C (advisor), Verheijen, M A W (advisor), De Blok, W J G (advisor).

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Ramatsoku, M. A. (2017). A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/27351

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Ramatsoku, Mpati Analicia. “A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance.” 2017. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/27351.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Ramatsoku, Mpati Analicia. “A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance.” 2017. Web. 02 Mar 2021.

Vancouver:

Ramatsoku MA. A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance. [Internet] [Thesis]. University of Cape Town; 2017. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/27351.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Ramatsoku MA. A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance. [Thesis]. University of Cape Town; 2017. Available from: http://hdl.handle.net/11427/27351

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

26. Kuhn, Rudolf Bruwer. Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope.

Degree: Image, Astronomy, 2014, University of Cape Town

URL: http://hdl.handle.net/11427/12920

► In this thesis I present the work I performed during the initial construction and deployment of the second telescope in the KELT project and I… (more)

▼ In this thesis I present the work I performed during the initial construction and deployment of the second telescope in the KELT project and I report the results of the search for transiting exoplanets and variable stars using one of the first commissioning datasets obtained with the telescope. The KELT-South telescope is located in Sutherland, South Africa and construction started in 2008. The telescope has been operating at full capacity since 2010, after two commissioning seasons from late 2008 to early 2010. I developed all the code that allows it to be fully automatic and robotic and over the last 5 years I have been responsible for the observing operations and general maintenance of the telescope. I also developed many other software tools that help with the identification of the exoplanet candidates. The Kilodegree Extremely Little Telescope (KELT) project at present consists of two robotic, wide field, small aperture telescopes that are designed primarily to find transiting exoplanets around bright stars in the magnitude range 8 < V < 11. Transiting planets orbiting bright stars can be studied with intense follow-up programs with relative ease on larger telescopes, making them favourable targets to determine the atmospheric composition of the planet as well as a host of other properties that cannot be obtained from planets orbiting fainter stars. Of the known 1811 (August 2014) exoplanets only 60 are transiting stars with V < 11 and only 16 of those have been found from the southern hemisphere. The discovery of more of these exoplanets will help constrain the theories of formation and evolution of short period, gas giant exoplanets. Data reduction on one of the commissioning datasets was completed in 2012. The dataset spans 46 days and lightcurves for 78297 objects were obtained. I performed a search for periodicities in the lightcurves and found that 1411 stars showed clear signs of variability and these objects were compiled into a catalogue of possible variable stars. 1018 of the catalogue members were not previously known to be variable. I searched for planetary transits and eight possible exoplanet candidates were identified. Photometric follow-up observations of two targets eliminated them as exoplanet candidates, each being a blended eclipsing binary system. The remaining six candidates are awaiting follow-up observations at present. Although the commissioning dataset served primarily to refine the data reduction pipeline and the procedures I used to find variable stars, I have demonstrated that the KELT-South telescope is capable of detecting the kinds of signals required for exoplanet discovery. Advisors/Committee Members: Whitelock, Patricia A (advisor), Menzies, John W (advisor).

Subjects/Keywords: Astronomy

11 more images…

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APA (6^th Edition):

Kuhn, R. B. (2014). Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope. (Thesis). University of Cape Town. Retrieved from http://hdl.handle.net/11427/12920

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Kuhn, Rudolf Bruwer. “Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope.” 2014. Thesis, University of Cape Town. Accessed March 02, 2021. http://hdl.handle.net/11427/12920.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Kuhn, Rudolf Bruwer. “Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope.” 2014. Web. 02 Mar 2021.

Vancouver:

Kuhn RB. Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope. [Internet] [Thesis]. University of Cape Town; 2014. [cited 2021 Mar 02]. Available from: http://hdl.handle.net/11427/12920.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Kuhn RB. Photometric techniques for exoplanet detection: the construction and deployment of the KELT-South telescope. [Thesis]. University of Cape Town; 2014. Available from: http://hdl.handle.net/11427/12920

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Yale University

27. Merritt, Allison Taylor. Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array.

Degree: 2018, Yale University

URL: http://pqdtopen.proquest.com/#viewpdf?dispub=10783454

► This thesis explores the ways in which observations of the low surface brightness universe can inform our views of galaxy evolution and, specifically, the… (more)

▼ This thesis explores the ways in which observations of the low surface brightness universe can inform our views of galaxy evolution and, specifically, the extent to which galaxies assemble stellar mass through mergers and accretion events. I first present a study of the variation in the stellar halos of galaxies, using data from the Dragonfly Nearby Galaxies Survey (DNGS). The survey consists of wide field, deep (μg > 31 mag aresec^-2) optical imaging of nearby galaxies using the Dragonfly Telephoto Array. The sample in question includes eight spiral galaxies with stellar masses similar to that of the Milky Way, inclinations of 16 – 90 degrees and distances between 7–18 Mpc. I construct stellar mass surface density profiles from the observed g-band surface brightness in combination with the g – r color as a function of radius, and compute the halo fractions from the excess stellar mass (relative to a disk+bulge fit) beyond 5 half-mass radii. I find a mean halo fraction of 0.009 ± 0.005 and a large RMS scatter of 1.01[special characters omitted] dex. The peak-to-peak scatter of the halo fraction is a factor of > 100 – while some galaxies feature strongly structured halos resembling that of M31, three of the eight have halos that are completely undetected in our data. I conclude from this sample that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. I find no convincing evidence for an environmental or stellar mass dependence of the halo fraction in the sample. In addition to being the future building blocks of the stellar halos of galaxies, dwarf satellite galaxies are a key probe of dark matter and of galaxy formation on small scales and of the dark matter halo masses of their central galaxies. They have very low surface brightness, however, which makes it difficult to identify and study them outside of the Local Group. I used the Dragonfly Telephoto Array to search for dwarf galaxies in the field of the massive spiral galaxy M101, and identified seven large, low surface brightness objects in this field, with effective radii of 10-30 arcseconds and central surface brightnesses of μg,0 ~ 25.5 – 27.5 mag aresec^-2. Given their large apparent sizes and low surface brightnesses, these objects would likely be missed by standard galaxy searches in deep fields. Their radial surface brightness profiles are well fit by Sersic profiles with a very low Sersic index (n ~ 0.3 – 0.7). The properties of the sample are similar to those of well-studied dwarf galaxies in the Local Group, such as Sextans I and Phoenix. Finally, follow-up observations of these low surface brightness objects with the Hubble Space Telescope subsequently revealed that three of the seven objects were bonafide satellite galaxies of the M101 group. I show that, unexpectedly, the other four galaxies are ultra-diffuse galaxies in a…

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Merritt, A. T. (2018). Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array. (Thesis). Yale University. Retrieved from http://pqdtopen.proquest.com/#viewpdf?dispub=10783454

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Merritt, Allison Taylor. “Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array.” 2018. Thesis, Yale University. Accessed March 02, 2021. http://pqdtopen.proquest.com/#viewpdf?dispub=10783454.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Merritt, Allison Taylor. “Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array.” 2018. Web. 02 Mar 2021.

Vancouver:

Merritt AT. Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array. [Internet] [Thesis]. Yale University; 2018. [cited 2021 Mar 02]. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10783454.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Merritt AT. Characterizing Assembly Histories in the Local Universe with the Dragonfly Telephoto Array. [Thesis]. Yale University; 2018. Available from: http://pqdtopen.proquest.com/#viewpdf?dispub=10783454

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Columbia University

28. Zimmerman, Neil Thomas. High-Contrast Observations with an Integral Field Spectrograph.

Degree: 2011, Columbia University

URL: https://doi.org/10.7916/D8GM8F91

► This thesis is comprised of work carried out during the commissioning phase of Project 1640, a combined coronagraph – integral field spectrograph for Palomar Observatory's adaptive… (more)

Subjects/Keywords: Astronomy

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APA (6^th Edition):

Zimmerman, N. T. (2011). High-Contrast Observations with an Integral Field Spectrograph. (Doctoral Dissertation). Columbia University. Retrieved from https://doi.org/10.7916/D8GM8F91

Chicago Manual of Style (16^th Edition):

Zimmerman, Neil Thomas. “High-Contrast Observations with an Integral Field Spectrograph.” 2011. Doctoral Dissertation, Columbia University. Accessed March 02, 2021. https://doi.org/10.7916/D8GM8F91.

MLA Handbook (7^th Edition):

Zimmerman, Neil Thomas. “High-Contrast Observations with an Integral Field Spectrograph.” 2011. Web. 02 Mar 2021.

Vancouver:

Zimmerman NT. High-Contrast Observations with an Integral Field Spectrograph. [Internet] [Doctoral dissertation]. Columbia University; 2011. [cited 2021 Mar 02]. Available from: https://doi.org/10.7916/D8GM8F91.

Council of Science Editors:

Zimmerman NT. High-Contrast Observations with an Integral Field Spectrograph. [Doctoral Dissertation]. Columbia University; 2011. Available from: https://doi.org/10.7916/D8GM8F91

Columbia University

29. Kreckel, Kathryn Joyce. Gas in Void Galaxies.

Degree: 2011, Columbia University

URL: https://doi.org/10.7916/D8BV7PMR

► Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an… (more)

▼ Void galaxies, residing within the deepest underdensities of the Cosmic Web, present an ideal population for the study of galaxy formation and evolution in an environment undisturbed by the complex processes modifying galaxies in clusters and groups, and provide an observational test for theories of cosmological structure formation. We investigate the neutral hydrogen properties (i.e. content, morphology, kinematics) of void galaxies, both individually and systematically, using a combination of observations and simulations, to form a more complete understanding of the nature of these systems. We investigate in detail the H I morphology and kinematics of two void galaxies. One is an isolated polar disk galaxy in a diffuse cosmological wall situated between two voids. The considerable gas mass and apparent lack of stars in the polar disk, coupled with the general underdensity of the environment, supports recent theories of cold flow accretion as an alternate formation mechanism for polar disk galaxies. We also examine KK 246, the only confirmed galaxy located within the nearby Tully Void. It is a dwarf galaxy with an extremely extended H I disk and signs of an H I cloud with anomalous velocity. It also exhibits clear misalignment between the kinematical major and minor axes, and a general misalignment between the H I and optical major axes. The relative isolation and extreme underdense environment make these both very interesting cases for examining the role of gas accretion in galaxy evolution. To study void galaxies as a population, we have carefully selected a sample of 60 galaxies that reside in the deepest underdensities of geometrically identified voids within the SDSS. We have imaged this new Void Galaxy Survey in H I at the Westerbork Synthesis Radio Telescope with a typical resolution of 8 kpc, probing a volume of 1.2 Mpc and 12,000 km s^-1 surrounding each galaxy. We reach H I mass limits of 2 x 10⁸ M_sun and column density sensitivities of 5 x 10¹⁹ cm^-2. We find that the void galaxies are generally gas rich, low luminosity, blue disk galaxies, but identify three as early type galaxies. The void galaxy optical and H I properties are not unusual for their luminosity and morphology. The small scale clustering in the void is similar to that in higher density regions, and we identify 18 H I rich neighboring galaxies in the voids. Two of these are systems of three galaxies linearly aligned and joined by a H I bridge, suggestive of filamentary formation within the void. We find no population of H I rich low luminosity galaxies within the observed voids that are not close companions of the targeted sample. Finally, to put these observations in a theoretical context, we analyze a (120 h^-1 Mpc)³ adaptive mesh refinement hydrodynamic simulation that contains a high resolution subvolume centered on a ~30 Mpc diameter void. We construct mock observations with ~1 kpc resolution of the stellar and gas properties of these systems which reproduce the range of colors and luminosities observed in the SDSS for nearby…

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Kreckel, K. J. (2011). Gas in Void Galaxies. (Doctoral Dissertation). Columbia University. Retrieved from https://doi.org/10.7916/D8BV7PMR

Chicago Manual of Style (16^th Edition):

Kreckel, Kathryn Joyce. “Gas in Void Galaxies.” 2011. Doctoral Dissertation, Columbia University. Accessed March 02, 2021. https://doi.org/10.7916/D8BV7PMR.

MLA Handbook (7^th Edition):

Kreckel, Kathryn Joyce. “Gas in Void Galaxies.” 2011. Web. 02 Mar 2021.

Vancouver:

Kreckel KJ. Gas in Void Galaxies. [Internet] [Doctoral dissertation]. Columbia University; 2011. [cited 2021 Mar 02]. Available from: https://doi.org/10.7916/D8BV7PMR.

Council of Science Editors:

Kreckel KJ. Gas in Void Galaxies. [Doctoral Dissertation]. Columbia University; 2011. Available from: https://doi.org/10.7916/D8BV7PMR

Columbia University

30. Schroeder, Joshua. Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars.

Degree: 2014, Columbia University

URL: https://doi.org/10.7916/D8BC3WRP

► In this dissertation, I explore the subject of short-period binary millisecond pulsars discovered by the Fermi Gamma-ray Space Telescope and radio follow-up teams, and present… (more)

▼ In this dissertation, I explore the subject of short-period binary millisecond pulsars discovered by the Fermi Gamma-ray Space Telescope and radio follow-up teams, and present observations of fields containing eight recently discovered short-period (Porb < 1 d) binary millisecond pulsars using the telescopes at MDM Observatory. The goal of these observations was to detect the optical counterparts of the binaries and, for the best-suited counterparts detected, to observe the photometric variation of the companion that happens over the course of the orbit in various filters. The hope was to then use the light curves to model the systems and obtain constraints on the mass of the neutron stars which are likely to be some of the most massive neutron stars in the galaxy. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, I present the fully orbital phase-resolved B, V , and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135, for which I employ the ELC model of Orosz & Hauschildt (2000) to measure the unknown system parameters. For PSR J1810+1744 I find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be MNS > 1.75 solar masses; at the 3-sigma level. I also find a discrepancy between the model temperature and the measured colors of this object which I interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2215+5135 contains a relatively high mass companion (Mc > 0.1 solar masses), I propose that similar to the binary pulsar systems PSR J1023+0038 and IGR J18245-2452, the pulsar may transition between accretion- and rotation-powered modes.

Subjects/Keywords: Astronomy

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Schroeder, J. (2014). Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars. (Doctoral Dissertation). Columbia University. Retrieved from https://doi.org/10.7916/D8BC3WRP

Chicago Manual of Style (16^th Edition):

Schroeder, Joshua. “Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars.” 2014. Doctoral Dissertation, Columbia University. Accessed March 02, 2021. https://doi.org/10.7916/D8BC3WRP.

MLA Handbook (7^th Edition):

Schroeder, Joshua. “Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars.” 2014. Web. 02 Mar 2021.

Vancouver:

Schroeder J. Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars. [Internet] [Doctoral dissertation]. Columbia University; 2014. [cited 2021 Mar 02]. Available from: https://doi.org/10.7916/D8BC3WRP.

Council of Science Editors:

Schroeder J. Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars. [Doctoral Dissertation]. Columbia University; 2014. Available from: https://doi.org/10.7916/D8BC3WRP

Open Access Theses and Dissertations