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Resolving Black Hole and Star-Formation Activity in Nearby Galaxies

Resolving Black Hole and Star-Formation Activity in Nearby Galaxies
Author: Mallory Elyse Molina
Publisher:
Total Pages:
Release: 2019
Genre:
ISBN:

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Black hole accretion and star formation exhibit different properties with observed spatial scale. To fully understand them, we must consider the local environment's impact on measured global properties. My dissertation focuses on the spatially resolved excitation mechanisms that power observed emission, and the dust that obscures it. Low ionization nuclear emission regions (LINERs) are common in nearby galaxies, and are often explained by photoionization by low luminosity active galactic nuclei (AGNs). But this energy source is not sufficient to power the observed emission lines that define LINERs on 100 pc scales. Using the Hubble Space Telescope, I resolved the nuclear regions of three nearby LINERs on the 10 pc scale to track the dominant power source with distance from the nucleus. The resulting physical model involved photoionization from the AGN within the central 20 pc, and shock excitation at larger distances. I conclude that integrated LINER-like emission can be explained by a combination of photoionization by the AGN and shocks on different spatial scales.The advancement and cessation of star formation within a galaxy is vital for understanding galaxy evolution. Furthermore, the rest-frame ultra violet (UV) and optical bands are crucial for disentangling the star formation history, metallicity and age of systems. To that end, I construct a data set of 150 galaxies with Swift Ultra Violet Optical Telescope (UVOT) UV photometry and Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV/MaNGA) optical IFU spectroscopy. I present properties of the data set, and use it to quantify relations between the UV and H-alpha star formation rate proxies.Unfortunately, our understanding of star formation is highly dependent on dust attenuation, which itself depends on the spatial scales and properties on which it is observed. This is especially true in the UV band, where the attenuation laws from literature differ dramatically. Therefore, any attempts to understand star formation histories in using the Swift+MaNGA data catalog will be subject to this systematic. To address this, I studied the attenuation law of kiloparsec-sized star forming regions using a subset of 29 galaxies. I compared the attenuation from the individual regions with that of the parent galaxy, and find the attenuation of the optical nebular emission is similar between the two physical scales, but that of the UV stellar continuum is not. I attribute this difference to sightline-dependencies of the stellar continuum attenuation and dilution of the UV light by older stars.Through spatially resolved studies of black hole accretion and star formation activity in nearby galaxies, my dissertation work provides context for the integrated properties of nearby galaxies, and provides context for future statistical surveys.


The Properties of Star-Forming Galaxies at Z~2

The Properties of Star-Forming Galaxies at Z~2
Author: Dawn Erb
Publisher: Universal-Publishers
Total Pages: 168
Release: 2005
Genre: Science
ISBN: 1581122977

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We study the properties of star-forming galaxies at redshift z 2, an era in which a substantial fraction of the stellar mass in the universe formed. Using 114 near-IR spectra of the H-alpha and [N II] emission lines and model spectral energy distributions fit to rest-frame UV through IR photometry, we examine the galaxies' star formation properties, dynamical masses and velocity dispersions, spatially resolved kinematics, outflow properties, and metallicities as a function of stellar mass and age. While the stellar masses of the galaxies in our sample vary by a factor of 500, dynamical masses from H-alpha velocity dispersions and indirect estimates of gas masses imply that the variation of stellar mass is due as much to the evolution of the stellar population and the conversion of gas into stars as to intrinsic differences in the total masses of the galaxies. About 10% of the galaxies are apparently young starbursts with high gas fractions, caught just as they have begun to convert large amounts of gas into stars. Using the [N II]/H-alpha ratio of composite spectra to estimate the average oxygen abundance, we find a monotonic increase in metallicity with stellar mass. From the estimated gas fractions, we conclude that the observed mass-metallicity relation is primarily driven by the increase in metallicity as gas is converted to stars. The picture that emerges is of galaxies with a broad range in stellar population properties, from young galaxies with ages of a few tens of Myr, stellar masses M 10 DEGREES9 Msun, and metallicities Z 1/3 Zsun, to massive objects with M* 10 DEGREES11 Msun, Z Zsun, and ages as old as the universe allows. All, however, are rapidly star-forming, power galactic-scale outflows, and have masses in gas and stars of at least 10 DEGREES10 Msun, in keeping with their likely role as the progenitors of elliptical galaxies


Astrophysics Of Gas Nebulae and Active Galactic Nuclei

Astrophysics Of Gas Nebulae and Active Galactic Nuclei
Author: Donald E. Osterbrock
Publisher: University Science Books
Total Pages: 488
Release: 2006
Genre: Science
ISBN: 9781891389344

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Thoroughly revised and expanded throughout, the new edition is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants. Much of the new data and new images are from the Hubble Space Telescope with two wholly new chapters being added along with other new features. The previous edition which was tried and tested for thirty years has now been succeeded by a revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.


Galactic and Extragalactic Star Formation

Galactic and Extragalactic Star Formation
Author: Ralph E. Pudritz
Publisher: Springer Science & Business Media
Total Pages: 652
Release: 2012-12-06
Genre: Science
ISBN: 9400929730

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Recent advances in the instrumentation used to observe star forming regions in both our own Milky Way and in external galaxies have transformed the subject from a phenomenological pursuit into an increasingly unified, physical science. High resolution centimetre, millimetre, infrared, and optical studies of local star forming clouds have allowed us to probe the physics of star formation down to spatial scales approaching those of the solar system. These developments make it possible to better constrain the basic physical processes underlying star formation itself. At the same time, these new instruments have placed extragalactic studies on a footing detailed enough to allow comparison with star forming regions within our own galaxy. This revolution means that we will soon be able to link the physics of local star forming regions to the global star forming properties of galaxies. The entire structure of this NATO Advanced Study Institute was designed to explore this new view of the subject. This Institute on "Galactic and Extragalactic Star Formation" was held from June 21 -July 4, 1987 at the Conference Centre in the village of Whistler, British Columbia, Canada. The informal atmosphere of this lovely mountain resort stim ulated many valuable scientific exchanges. The Institute was funded by a major grant from NATO Scientific Affairs. Additional financial and I.I1oral assistance was provided by the Canadian Institute for Theoretical Astrophysics (CITA) and Mc Master University.