One of the central goals of extragalactic astronomy is to understand how galaxies grow their stel... more One of the central goals of extragalactic astronomy is to understand how galaxies grow their stellar mass and central black holes, the connection between star formation and active galactic nuclei (AGN), and the impact of environment on this growth. In this thesis, I utilize multiwavelength surveys that are both deep and wide, advanced computational codes that model the spectral energy distributions of galaxies with and without AGN, as well as state-of-the-art simulations of galaxy evolution in order to explore how galaxy properties are impacted by their surrounding environment and AGN activity. These studies explore galaxies over a redshift range of $0.015 < z < 0.023$ (lookback time of $\sim 0.2$ to $\sim 0.3$ Gyr), and over a redshift range of $0.5 < z < 3.0$ (lookback time of $\sim 5$ to $\sim 12$ Gyr). The large-area surveys used here provide some of the largest and most statistically robust samples to-date of rare massive galaxies (with stellar mass $M_* > 10^{11...
We present the most-detailed probe yet into the impact of active galactic nuclei feedback on star... more We present the most-detailed probe yet into the impact of active galactic nuclei feedback on star formation by measuring the shape of the bright end of the galaxy UV luminosity function at z~4.
Monthly Notices of the Royal Astronomical Society, 2021
We present the main sequence for all galaxies and star-forming galaxies for a sample of 28 469 ma... more We present the main sequence for all galaxies and star-forming galaxies for a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) galaxies at cosmic noon (1.5 < z < 3.0), uniformly selected from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). Our large sample allows for a novel approach to investigating the galaxy main sequence that has not been accessible to previous studies. We measure the main sequence in small mass bins in the SFR–M⋆ plane without assuming a functional form for the main sequence. With a large sample of galaxies in each mass bin, we isolate star-forming galaxies by locating the transition between the star-forming and green valley populations in the SFR–M⋆ plane. This approach eliminates the need for arbitrarily defined fixed cutoffs when isolating the star-forming galaxy population, which often biases measurements of the scatter around the star-forming galaxy main sequence. We find that the main sequence for all galaxies becomes increasingly flat towar...
Monthly Notices of the Royal Astronomical Society, 2021
In theoretical models of galaxy evolution, active galactic nucleus (AGN) and star formation (SF) ... more In theoretical models of galaxy evolution, active galactic nucleus (AGN) and star formation (SF) activity are closely linked and AGN feedback is routinely invoked to regulate galaxy growth. In order to constrain such models, we compare the hydrodynamical simulations IllustrisTNG and SIMBA, and the semi-analytical model SAG to the empirical results on AGN and SF at cosmic noon (0.75 < z < 2.25) reported in Florez et al. (2020). The empirical results are based on a large mass-complete sample drawn from 93 307 galaxies with and without high X-ray luminosity AGN (LX ≳ 1044 erg s−1), selected from a 11.8 deg2 area (∼0.18 Gpc3 comoving volume at z = 0.75–2.25). The main results of our comparisons are: (i) SAG and IllustrisTNG both qualitatively reproduce the empirical result that galaxies with high X-ray luminosity AGN have higher mean SFR, at a given stellar mass, than galaxies without such AGN. SAG, however, strongly overproduces the number density of high X-ray luminosity AGN by ...
Monthly Notices of the Royal Astronomical Society, 2020
We investigate the relation between active galactic nucleus (AGN) and star formation (SF) activit... more We investigate the relation between active galactic nucleus (AGN) and star formation (SF) activity at 0.5 < z < 3 by analysing 898 galaxies with X-ray luminous AGNs (LX > 1044 erg s−1) and a large comparison sample of ∼320 000 galaxies without X-ray luminous AGNs. Our samples are selected from a large (11.8 deg2) area in Stripe 82 that has multiwavelength (X-ray to far-IR) data. The enormous comoving volume (∼0.3 Gpc3) at 0.5 < z < 3 minimizes the effects of cosmic variance and captures a large number of massive galaxies (∼30 000 galaxies with M* > 1011 M⊙) and X-ray luminous AGNs. While many galaxy studies discard AGN hosts, we fit the SED of galaxies with and without X-ray luminous AGNs with Code Investigating GALaxy Emission and include AGN emission templates. We find that without this inclusion, stellar masses and star formation rates (SFRs) in AGN host galaxies can be overestimated, on average, by factors of up to ∼5 and ∼10, respectively. The average SFR of g...
Monthly Notices of the Royal Astronomical Society, 2020
We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) gal... more We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) galaxies at redshifts 1.5 < $z$ < 3.0, drawn from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). This allows for a robust study of the quiescent fraction as a function of mass at 1.5 < $z$ < 3.0 with a sample ∼40 times larger at log(M⋆/$\rm M_{\odot })\ge 11.5$ than previous studies. We derive the quiescent fraction using three methods: specific star formation rate, distance from the main sequence, and UVJ colour–colour selection. All three methods give similar values at 1.5 < $z$ < 2.0, however the results differ by up to a factor of 2 at 2.0 < $z$ < 3.0. At redshifts 1.5 < $z$ < 3.0, the quiescent fraction increases as a function of stellar mass. By $z$ = 2, only 3.3 Gyr after the big bang, the universe has quenched ∼25 per cent of M⋆ = 1011 M⊙ galaxies and ∼45 per cent of M⋆ = 1012 M⊙ galaxies. We discuss physical mechanisms across a range ...
Monthly Notices of the Royal Astronomical Society, 2019
We present the high-mass end of the galaxy stellar mass function using the largest sample to date... more We present the high-mass end of the galaxy stellar mass function using the largest sample to date (5352) of star-forming galaxies with M⋆ > 1011 M⊙ at cosmic noon, 1.5 < z < 3.5. This sample is uniformly selected across 17.2 deg2 (∼0.44 Gpc3 comoving volume from 1.5 < z < 3.5), mitigating the effects of cosmic variance and encompassing a wide range of environments. This area, a factor of 10 larger than previous studies, provides robust statistics at the high-mass end. Using multiwavelength data in the Spitzer/HETDEX Exploratory Large Area (SHELA) footprint, we find that the SHELA footprint star-forming galaxy stellar mass function is steeply declining at the high-mass end probing values as high as ∼10−4 Mpc3 dex−1 and as low as ∼5 × 10−8 Mpc3 dex−1 across a stellar mass range of log(M⋆/M⊙) ∼ 11–12. We compare our empirical star-forming galaxy stellar mass function at the high-mass end to three types of numerical models: hydrodynamical models from IllustrisTNG, abundan...
One of the central goals of extragalactic astronomy is to understand how galaxies grow their stel... more One of the central goals of extragalactic astronomy is to understand how galaxies grow their stellar mass and central black holes, the connection between star formation and active galactic nuclei (AGN), and the impact of environment on this growth. In this thesis, I utilize multiwavelength surveys that are both deep and wide, advanced computational codes that model the spectral energy distributions of galaxies with and without AGN, as well as state-of-the-art simulations of galaxy evolution in order to explore how galaxy properties are impacted by their surrounding environment and AGN activity. These studies explore galaxies over a redshift range of $0.015 < z < 0.023$ (lookback time of $\sim 0.2$ to $\sim 0.3$ Gyr), and over a redshift range of $0.5 < z < 3.0$ (lookback time of $\sim 5$ to $\sim 12$ Gyr). The large-area surveys used here provide some of the largest and most statistically robust samples to-date of rare massive galaxies (with stellar mass $M_* > 10^{11...
We present the most-detailed probe yet into the impact of active galactic nuclei feedback on star... more We present the most-detailed probe yet into the impact of active galactic nuclei feedback on star formation by measuring the shape of the bright end of the galaxy UV luminosity function at z~4.
Monthly Notices of the Royal Astronomical Society, 2021
We present the main sequence for all galaxies and star-forming galaxies for a sample of 28 469 ma... more We present the main sequence for all galaxies and star-forming galaxies for a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) galaxies at cosmic noon (1.5 < z < 3.0), uniformly selected from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). Our large sample allows for a novel approach to investigating the galaxy main sequence that has not been accessible to previous studies. We measure the main sequence in small mass bins in the SFR–M⋆ plane without assuming a functional form for the main sequence. With a large sample of galaxies in each mass bin, we isolate star-forming galaxies by locating the transition between the star-forming and green valley populations in the SFR–M⋆ plane. This approach eliminates the need for arbitrarily defined fixed cutoffs when isolating the star-forming galaxy population, which often biases measurements of the scatter around the star-forming galaxy main sequence. We find that the main sequence for all galaxies becomes increasingly flat towar...
Monthly Notices of the Royal Astronomical Society, 2021
In theoretical models of galaxy evolution, active galactic nucleus (AGN) and star formation (SF) ... more In theoretical models of galaxy evolution, active galactic nucleus (AGN) and star formation (SF) activity are closely linked and AGN feedback is routinely invoked to regulate galaxy growth. In order to constrain such models, we compare the hydrodynamical simulations IllustrisTNG and SIMBA, and the semi-analytical model SAG to the empirical results on AGN and SF at cosmic noon (0.75 < z < 2.25) reported in Florez et al. (2020). The empirical results are based on a large mass-complete sample drawn from 93 307 galaxies with and without high X-ray luminosity AGN (LX ≳ 1044 erg s−1), selected from a 11.8 deg2 area (∼0.18 Gpc3 comoving volume at z = 0.75–2.25). The main results of our comparisons are: (i) SAG and IllustrisTNG both qualitatively reproduce the empirical result that galaxies with high X-ray luminosity AGN have higher mean SFR, at a given stellar mass, than galaxies without such AGN. SAG, however, strongly overproduces the number density of high X-ray luminosity AGN by ...
Monthly Notices of the Royal Astronomical Society, 2020
We investigate the relation between active galactic nucleus (AGN) and star formation (SF) activit... more We investigate the relation between active galactic nucleus (AGN) and star formation (SF) activity at 0.5 < z < 3 by analysing 898 galaxies with X-ray luminous AGNs (LX > 1044 erg s−1) and a large comparison sample of ∼320 000 galaxies without X-ray luminous AGNs. Our samples are selected from a large (11.8 deg2) area in Stripe 82 that has multiwavelength (X-ray to far-IR) data. The enormous comoving volume (∼0.3 Gpc3) at 0.5 < z < 3 minimizes the effects of cosmic variance and captures a large number of massive galaxies (∼30 000 galaxies with M* > 1011 M⊙) and X-ray luminous AGNs. While many galaxy studies discard AGN hosts, we fit the SED of galaxies with and without X-ray luminous AGNs with Code Investigating GALaxy Emission and include AGN emission templates. We find that without this inclusion, stellar masses and star formation rates (SFRs) in AGN host galaxies can be overestimated, on average, by factors of up to ∼5 and ∼10, respectively. The average SFR of g...
Monthly Notices of the Royal Astronomical Society, 2020
We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) gal... more We explore the build-up of quiescent galaxies using a sample of 28 469 massive (M⋆ ≥ 1011 M⊙) galaxies at redshifts 1.5 < $z$ < 3.0, drawn from a 17.5 deg2 area (0.33 Gpc3 comoving volume at these redshifts). This allows for a robust study of the quiescent fraction as a function of mass at 1.5 < $z$ < 3.0 with a sample ∼40 times larger at log(M⋆/$\rm M_{\odot })\ge 11.5$ than previous studies. We derive the quiescent fraction using three methods: specific star formation rate, distance from the main sequence, and UVJ colour–colour selection. All three methods give similar values at 1.5 < $z$ < 2.0, however the results differ by up to a factor of 2 at 2.0 < $z$ < 3.0. At redshifts 1.5 < $z$ < 3.0, the quiescent fraction increases as a function of stellar mass. By $z$ = 2, only 3.3 Gyr after the big bang, the universe has quenched ∼25 per cent of M⋆ = 1011 M⊙ galaxies and ∼45 per cent of M⋆ = 1012 M⊙ galaxies. We discuss physical mechanisms across a range ...
Monthly Notices of the Royal Astronomical Society, 2019
We present the high-mass end of the galaxy stellar mass function using the largest sample to date... more We present the high-mass end of the galaxy stellar mass function using the largest sample to date (5352) of star-forming galaxies with M⋆ > 1011 M⊙ at cosmic noon, 1.5 < z < 3.5. This sample is uniformly selected across 17.2 deg2 (∼0.44 Gpc3 comoving volume from 1.5 < z < 3.5), mitigating the effects of cosmic variance and encompassing a wide range of environments. This area, a factor of 10 larger than previous studies, provides robust statistics at the high-mass end. Using multiwavelength data in the Spitzer/HETDEX Exploratory Large Area (SHELA) footprint, we find that the SHELA footprint star-forming galaxy stellar mass function is steeply declining at the high-mass end probing values as high as ∼10−4 Mpc3 dex−1 and as low as ∼5 × 10−8 Mpc3 dex−1 across a stellar mass range of log(M⋆/M⊙) ∼ 11–12. We compare our empirical star-forming galaxy stellar mass function at the high-mass end to three types of numerical models: hydrodynamical models from IllustrisTNG, abundan...
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