Quantifying the Physical Properties of High-Redshift Galaxies: A Multi-wavelength Survey on the Progenitors of Local Galaxies

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Quantifying the Physical Properties of High-Redshift Galaxies: A Multi-wavelength Survey on the Progenitors of Local Galaxies

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Title: Quantifying the Physical Properties of High-Redshift Galaxies: A Multi-wavelength Survey on the Progenitors of Local Galaxies
Author: Petty, Sara Michelle
Abstract: Since the discovery of galaxies outside of the Milky Way, studies of nearby galaxies have revealed a very different population of galaxies compared to distant galaxies. My thesis has been motivated by galaxy evolution. In particular, I focus on the connection between nearby and distant galaxies, changes in morphologies with wavelength, and the physical properties of galaxies when the Universe was 1.5 (<italic>z</italic> = 4) to 6 (<italic>z</italic> = 1) Gyr old. Rest-frame far-ultraviolet morphologies of 8 nearby interacting and starburst galaxies are artificially redshifted and compared with 54 galaxies at <italic>z</italic> ∼ 1.5 and 46 galaxies at <italic>z</italic> ∼ 4. I calculated the Gini coefficient (G), the second-order moment of the brightest 20% of the galaxy's flux (<italic>M</italic><sub>20</sub>), and the S&eacute;rsic index (<italic>n</italic>). I showed that ∼20-30% of Lyman-break galaxies have structures similar to local starburst mergers, and may be driven by similar processes. I also determined that Mrk 8, NGC 3079, and NGC 7673 have structures similar to merger-like and clumpy star-forming galaxies observed at <italic>z</italic> ∼ 1.5 and 4. I selected 301 galaxies from the Ultra Deep Field parallel survey (UDF05) done with HST's infrared camera, NICMOS, to calculate their spectral energy distributions (SEDs). The galaxies are cross-matched using HST ACS and NICMOS filters, and the infrared Spitzer IRAC filters. Photometric redshifts, dust extinction, stellar masses, bolometric luminosity, starburst age and metallicity are estimated through Balmer-break SED fitting. Comparisons of 16 photometric redshifts with spectroscopic redshifts give 75% agreement. I determined through Monte Carlo simulations that the SED parameters are robust for the redshift ranges <italic>z</italic> > 1.2. I find that luminosities and star formation rates increase with redshift for a subsample of galaxies at <italic>z</italic> ∼ 1.5 and <italic>z</italic> ∼ 4. I demonstrate that multi-wavelength analysis is fundamental to the understanding of galaxy evolution. I determined that G-<italic>M</italic><sub>20</sub> values of Balmer-break galaxies are more bulge-like in the rest-frame optical than <italic>z</italic> ∼ 1 and 4 starburst galaxies in the UV. I conclude that the Balmer-break selected galaxies are probably progenitors to local early type galaxies.
Description: Degree awarded: Ph.D. Physics. The Catholic University of America
URI: http://hdl.handle.net/1961/9221
Date: 2011-02-24


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