Dale D. Kocevski

The Evolution of the Galaxy Rest-Frame Ultraviolet Luminosity Function Over the First Two Billion Years

We present a robust measurement and analysis of the rest-frame ultraviolet (UV) luminosity functions at z = 4-8. We use deep Hubble Space Telescope imaging over the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey/GOODS fields, the Hubble Ultra Deep Field, and the Hubble Frontier Field deep parallel observations near the Abell 2744 and MACS J0416.1-2403 clusters. The combination of these surveys provides an effective volume of 0.6-1.2 x 10(6) Mpc(3) over this epoch, allowing us to perform a robust search for faint (M-UV = -18) and bright (Muv textless -21) high-redshift galaxies. We select candidate galaxies using a well-tested photometric redshift technique with careful screening of contaminants, finding a sample of 7446 candidate galaxies at 3.5 textless z textless 8.5, with textgreater1000 galaxies at z approximate to 6-8. We measure both a stepwise luminosity function for candidate galaxies in our redshift samples, and a Schechter function, using a Markov Chain Monte Carlo analysis to measure robust uncertainties. At the faint end, our UV luminosity functions agree with previous studies, yet we find a higher abundance of UV-bright candidate galaxies at z textgreater= 6. Our best-fit value of the characteristic magnitude MN is consistent with -21 at z textgreater=, 5, which is different than that inferred based on previous trends at lower redshift, and brighter at similar to 2 sigma significance than previous measures at z = 6 and 7. At z = 8, a single power law provides an equally good fit to the UV luminosity function, while at z = 6 and 7 an exponential cutoff at the bright end is moderately preferred. We compare our luminosity functions to semi-analytical models, and find that the lack of evolution in M-UV(*) is consistent with models where the impact of dust attenuation on the bright end of the luminosity function decreases at higher redshift, although a decreasing impact of feedback may also be possible. We measure the evolution of the cosmic star-formation rate (SFR) density by integrating our observed luminosity functions to M-UV = -17, correcting for dust attenuation, and find that the SFR density declines proportionally to (1 +z)(-4.3 +/- 0 5) at z textgreater 4, which is consistent with observations at z textgreater= 9. Our observed luminosity functions are consistent with a reionization history that starts at z greater than or similar to 10, completes at z textgreater 6, and reaches a midpoint (xH = 0.5) at 6.7 textless z textless9.4. Finally, using a constant cumulative number density selection and an empirically derived rising star-formation history, our observations predict that the abundance of bright z = 9 galaxies is likely higher than previous constraints, although consistent with recent estimates of bright z similar to 10 galaxies.

ARE COMPTON-THICK AGNs THE MISSING LINK BETWEEN MERGERS AND BLACK HOLE GROWTH?

We examine the host morphologies of heavily obscured active galactic nuclei (AGN) at

Galaxy Zoo:are bars responsible for the feeding of active galactic nuclei at 0.2 < z < 1.0

zsim1

Mass assembly and morphological transformations since z ∼ 3 from CANDELS

to test whether obscured supermassive black hole growth at this epoch is preferentially linked to galaxy mergers. Our sample consists of 154 obscured AGN with

CAUGHT IN THE ACT: GAS AND STELLAR VELOCITY DISPERSIONS IN A FAST QUENCHING COMPACT STAR-FORMING GALAXY AT z ∼ 1.7

N_{rm H}>10^{23.5}

Structural and Star-forming Relations since z similar to 3: Connecting Compact Star-forming and Quiescent Galaxies

cm

Beyond spheroids and discs: classifications of CANDELS galaxy structure at 1.4 < z < 2 via principal component analysis

^{-2}

THE INTERSTELLAR MEDIUM AND FEEDBACK IN THE PROGENITORS OF THE COMPACT PASSIVE GALAXIES AT z ∼ 2

and

Galaxy Zoo: Quantitative Visual Morphological Classifications for 48,000 galaxies from CANDELS

z<1.5

CANDELS MULTI-WAVELENGTH CATALOGS: SOURCE IDENTIFICATION AND PHOTOMETRY IN THE CANDELS COSMOS SURVEY FIELD

. Using visual classifications, we compare the morphologies of these AGN to control samples of moderately obscured (