Browsing by Subject "Galaxy evolution"
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Item Characterizing bars at z~0 in the optical and NIR : implications for the evolution of barred disks with redshift(2007-08) Marinova, Irina Stoilova; Jogee, ShardhaCritical insights on galaxy evolution stem from the study of bars. With the advent of high redshift HST surveys that trace bars in the rest-frame optical band out to z [more or less] 1, it becomes increasingly important to provide a reference baseline for bars at z [more or less] 0 in the optical band. We present results on bars at z [more or less] 0 in the optical and near-infrared bands, based on 180 spirals in the OSUBSGS survey. (1) The deprojected bar fraction at z [more or less] 0 is [function]NIR1 [more or less] 60% [plus or minus] 6% in the near-infrared H band, and [function]optical1[more or less]44% [plus or minus] 6% in the optical B-band images. The latter likely miss bars obscured by dust and star formation. (2) The results before and after deprojection are similar, which is encouraging for high redshift studies that forego deprojection. (3) Studies of bars at z [more or less] 0.2 -1.0 (lookback times of 3-8 Gyr) have reported an optical bar fraction of [function]optical2 [more or less] 30% [plus or minus] 6%, after applying cutoffs in absolute magnitude (MV <-19.3), bar size (abar [greater than or equal to] 1.5 kpc), and bar ellipticity (ebar [greater than or equal to] 0.4) in order to ensure a complete sample, adequate spatial resolution, and reliable bar identification out to z [more or less] 1. Applying these exact cutoffs in magnitude, bar size, and bar ellipticity to the OSUBSGS data yields a comparable optical B- and bar fraction at z [more or less] 0 of [function]optical3 [more or less] 34% [plus or minus] 6%. This rules out scenarios where the optical bar fraction in bright disks declines strongly with redshift. (3)We investigate bar strengths at z [more or less] 0 using the maximum bar ellipticity (ebar) as a guide. Most ( [more or less] 70%) bars have moderate to high ellipticity (0.50 [less than or equal to] ebar [less than or equal to] 0.75), and only a small fraction (7%-10%) have 0.25 [less than or equal to] ebar [less than or equal to] 0.40. There is no bimodality in the distribution of ebar. The H-band bar fraction and ebar show no substantial variation across RC3 Hubble types Sa to Scd. (4) RC3 bar types should be used with caution. Many galaxies with RC3 types `AB' turn out to be unbarred and RC3 bar classes `B' and `AB' have a significant overlap in ebar. (5) Most (68% in B and 76% in H) bars have sizes below 5 kpc. Bar and disk sizes correlate, and the ratio (abar/R25) lies primarily in the range 0.1 to 0.5. This suggests that the growth of bars and disks is intimately tied.Item Connecting the dots : tracking galaxy evolution using constant cumulative number density at 3(2015-12) Jaacks, Jason Dale; Finkelstein, Steven L.; Bromm, VolkerUsing the cosmological smoothed particle hydrodynamical code GADGET-3 we make a realistic assessment of the technique of using constant cumulative number density as a tracer of galaxy evolution. We find that over a redshift range of 3Item Constraining the end of reionization with ly [alpha] spectroscopy(2019-07-29) Jung, Intae; Finkelstein, Steven L.; Dickinson, Mark; Bromm, Volker; Gebhardt, Karl; Casey, Caitlin MThe reionization of the intergalactic medium (IGM) marks the time in the early universe when the first stars and galaxies began to affect the universe around them, as during this last major phase transition high-energy ultraviolet photons from these objects ionized the gas in the IGM, and it remains ionized to the present day. Studying reionization is a key frontier in observational cosmology, as it can therefore provide key insights into the formation and evolution of galaxies in the early universe. As Lyα photons are resonantly scattered by neutral hydrogen in the IGM, an analysis of this line can be used to trace the existence of neutral hydrogen in the IGM at different points in the history of the universe (i.e., when the IGM becomes neutral, we should stop seeing these photons, as they are likely scattered out of our line-of-sight). The work in this dissertation focuses on completing a spectroscopic survey of galaxies in the early universe, to measure the Lyα equivalent width (EW) distribution into the epoch of reionization and investigate the evolution of the IGM during reionization, pinning down the late time-evolution of reionization. To measure the Lyα EW distribution in the reionization era, we utilize deep spectroscopic observations of candidate galaxies from the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) using both the DEIMOS (optical) and MOSFIRE (near-infrared; NIR) spectrographs on the Keck telescopes. Our large spectroscopic dataset compiled with both Keck telescope observations represent the deepest and most complete spectroscopic survey for galaxies in the epoch of reionization. We study the Lyα emission strength through constraining the Lyα equivalent width (EW) distribution with our spectroscopic dataset by constructing detailed simulations of mock emission lines, accounting for the observational conditions (e.g., exposure time, wavelength coverage, and sky emission) and galaxy photometric redshift probability distribution functions. The measurements of the EW distribution with the detected Lyα emission lines from our DEIMOS and MOSFIRE observations provide additional evidence that the Lyα EW distribution declines at z > 6, suggesting an increasing fraction of neutral hydrogen in the IGM. Thanks to plenty of high-quality observational data from space telescopes such as the Hubble Space Telescope and the Spitzer Space Telescope, observational studies of the evolution of galaxies in the early universe have been performed over the past decade. Those studies have revealed statistical trends of the star formation history and the evolution of those galaxies over the cosmic time. However, since the star formation happens in a complex way, an analysis of the integrated properties of galaxies is not enough to grasp the physical processes governing the star formation and the growth of galaxies. The advent of a spatially resolved study of each individual galaxy has provided us an excellent approach to explore star formation processes inside a galaxy and to examine the inside-out / outside-in growth scenarios of galaxies. We perform a spatially resolved study of galaxies in the early universe at z ≳ 4 using the CANDELS Survey and HAWK-I UDS GOODS (HUGS) survey data. We estimate stellar mass, star formation rate, and dust extinction for galaxy inner and outer regions via spatially resolved spectral energy distribution fitting based on a Markov Chain Monte Carlo algorithm. By comparing specific star formation rates (sSFRs) between inner and outer parts of the galaxies we find that the majority of galaxies with high central mass densities show evidence for a preferentially lower sSFR in their centers than in their outer regions, indicative of reduced sSFRs in their central regionsItem Evidence of a flat outer rotation curve in a starbursting disk galaxy at z=1.6(2018-11-29) Drew, Patrick Michael; Casey, Caitlin M.; Finkelstein, Steven L; Boylan-Kolchin, Michael; Bromm, VolkerObservations of the baryon to dark matter fraction in galaxies through cosmic time are a fundamental test for galaxy formation models. Recent observational studies have suggested that some disk galaxies at z>1 host declining rotation curves, in contrast with observations of low redshift disk galaxies where stellar or HI rotation curves flatten at large radii. We present an observational counterexample, a galaxy named DSFG850.95 at z=1.555 (4.1 Gyr after the big bang) that hosts a flat rotation curve between radii of ~6— 14 kpc (1.2—2.8 disk scale lengths) and has a dark matter fraction of 0.44±0.08 at the H-band half light radius, similar to the Milky Way. We create position-velocity and position-dispersion diagrams using Keck/MOSFIRE spectroscopic observations of Hα and [NII] emission features, which reveal a flat rotation velocity of V[subscript flat]=285±12 km/s and an ionized gas velocity dispersion of σ₀=48±4 km/s. This galaxy has a rotation-dominated velocity field with V[subscript flat]/σ₀~6. Ground-based H-band imaging reveals a disk with Sérsic index of 1.29±0.03, an edge-on inclination angle of 87±2°, and an H-band half light radius of 8.4±0.1 kpc. Our results point to DSFG850.95 being a massive, rotationally-supported disk galaxy with a high dark-matter-to-baryon fraction in the outer galaxy, similar to disk galaxies at low redshift.Item Exploring AGN and star formation activity of massive galaxies at cosmic noon(2020-08-17) Florez, Jonathan; Jogee, Shardha; Boylan-Kolchin, MichaelWe investigate the relation between AGN and star formation (SF) activity at 0.5 < z < 3 by analyzing 898 galaxies with X-ray luminous AGN (L [subscript x] > 10⁴⁴ erg s⁻¹) and a large comparison sample of ~ 320,000 galaxies without X-ray luminous AGN. Our samples are selected from a large (11.8 deg²) area in Stripe 82 that has multi-wavelength (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 [subscript *] > 10¹¹ \ [solar mass]) and X-ray luminous AGN. While many galaxy studies discard AGN hosts, we fit the SED of galaxies with and without X-ray luminous AGN with Code Investigating GALaxy Emission (CIGALE) 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 galaxies with X-ray luminous AGN is higher by a factor of ~ 3 to 10 compared to galaxies without X-ray luminous AGN at fixed stellar mass and redshift, suggesting that high SFRs and high AGN X-ray luminosities may be fueled by common mechanisms. The vast majority (> 95%) of galaxies with X-ray luminous AGN at z = 0.5 - 3 do not show quenched SF: this suggests that if AGN feedback quenches SF, the associated quenching process takes a significant time to act and the quenched phase sets in after the highly luminous phases of AGN activity.Item Exploring the interplay between star formation and active galactic nuclei and the role of environment in galaxy evolution(2021-08-13) Florez, Jonathan; Jogee, Shardha; Bromm, Volker; Finkelstein, Steven L; Evans, Neal J; Boylan-Kolchin, Michael; Conselice, ChristopherOne 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 ~ 0.2 to ~ 0.3 Gyr), and over a redshift range of 0.5 < z < 3.0 (lookback time of ~ 5 to ~ 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 [subscript *] > 10¹¹ M☉) and extremely luminous AGN (with X-ray luminosity L [subscript X] > 10⁴⁴ erg s⁻¹) out to z ~ 3, thereby limiting the effects of cosmic variance and Poisson statistics. I analyze the observed stellar masses and star formation rates of galaxies as a function of environment and AGN activity, compare the empirical results to theoretical models of galaxy evolution, and discuss the implications of such comparisons. This work will provide significant guidance and constraints to the future development of theoretical models of galaxy growth. In Chapter 2 (Florez et al. 2021, ApJ, 906, 97) I measure the environmental dependence, where environment is defined by the distance to the third nearest neighbor, of multiple galaxy properties inside the Environmental COntext (ECO) catalog. I focus primarily on void galaxies at redshifts z = 0.015 - 0.023, which I define as the 10% of galaxies having the lowest local density. I compare the properties of void and non-void galaxies: baryonic mass, color, fractional stellar mass growth rate (FSMGR), morphology, and gas-to-stellar-mass ratio. The void galaxies typically have lower baryonic masses than galaxies in denser environments, and they display the properties expected of a lower mass population: they have more late-types, are bluer, have higher FSMGR, and are more gas rich. I also control for baryonic mass and investigate the extent to which void galaxies are different at fixed mass. I find that void galaxies are bluer, more gas-rich, and more star forming at fixed mass than non-void galaxies, which is a possible signature of galaxy assembly bias and other environmental processes. Furthermore, I show that these trends persist even at fixed mass and morphology, and I find that voids host a distinct population of early-types that are bluer and more star-forming than the typical red and quenched early-types. In addition to these empirical observational results, I also present theoretical results from mock catalogs with built-in galaxy assembly bias. I show that a simple matching of galaxy properties to (sub)halo properties, such as mass and age, can recover the observed environmental trends in the local galaxy population. In Chapter 3 (Florez et al. 2020, MNRAS, 497, 3273) I investigate the relation between AGN and star formation activity at 0.5 < z < 3 by analyzing 898 galaxies with high X-ray luminosity AGN (L [subscript X] > 10⁴⁴ erg s⁻¹) and a large comparison sample of ~ 320,000 galaxies without such AGN. My samples are selected from a large (11.8 deg²) area in Stripe 82 that has multi-wavelength (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 [subscript *] > 10¹¹ M☉) and high X-ray luminosity AGN. While it is typical for studies of galaxy evolution to discard AGN host galaxies, I fit the SED of galaxies with and without high X-ray luminosity AGN with Code Investigating GALaxy Emission (CIGALE) and include AGN emission templates. I find that without this inclusion, stellar masses and star formation rates in AGN host galaxies can be overestimated, on average, by factors of up to ~ 5 and ~ 10, respectively. The average star formation rate of galaxies with X-ray luminous AGN is higher by a factor of ~ 3 to 10 compared to galaxies without X-ray luminous AGN at fixed stellar mass and redshift, suggesting that high star formation rates and high AGN X-ray luminosities may be fueled by common mechanisms. The vast majority (> 95%) of galaxies with X-ray luminous AGN at z = 0.5 - 3 do not show quenched star formation: this suggests that if AGN feedback quenches star formation, the associated quenching process takes a significant time to act and the quenched phase sets in after the highly luminous phases of AGN activity. In numerical simulations and theoretical models of galaxy evolution, AGN and star formation activity are closely linked and AGN feedback is invoked to regulate galaxy growth. However, few empirical tests exist on how well the models and simulations implement the growth and interplay between AGN and star formation. To address this issue, in Chapter 4 (Florez et al. submitted) I compare the hydrodynamical simulations IllustrisTNG and SIMBA, and the semi-analytical model SAG to the empirical results on AGN and star formation at cosmic noon reported in Chapter 3. The main results of my comparisons are: (i) SAG and IllustrisTNG both qualitatively reproduce the empirical result that galaxies with high X-ray luminosity AGN have higher mean star formation rates, at a given stellar mass, than galaxies without such AGN. SAG, however, strongly over-produces the number density of high X-ray luminosity AGN by a factor of 10 to 100, while IllustrisTNG shows a lack of high X-ray luminosity AGN at high stellar mass (M [subscript *] > 10¹¹ M☉) at z ~ 2. (ii) In SIMBA, the mean star formation rate of galaxies with high X-ray luminosity AGN is lower than the star formation rate of galaxies without such AGN. Contrary to the data, many high X-ray luminosity AGN in SIMBA have quenched star formation, suggesting that AGN feedback, or other feedback modes in galaxies with such AGN, might be too efficient in SIMBA. I discuss the implications of these results for our understanding of the evolution of galaxies and the growth of their stellar masses and black holes across cosmic time.Item Integral field spectroscopy : instrumentation and a new window into low-redshift galaxy populations(2021-05-07) Indahl, Briana; Hill, Gary J.; Finkelstein, Steven; Casey, Caitlin; Drory, Niv; McQuinn, Kristen; Bershady, Matthew; Chisholm, JohnIntegral field spectrographs (IFS) have transformed studies of low-redshift spatially resolved galaxies as they provide simultaneous spectral coverage over contiguous spatial regions. IFS surveys of galaxies have allowed for observations of the spatially varying physical diagnostics of galaxy disks. Though IFS instruments have been traditionally limited to small fields of view (FOV), on the order of 100 square arcseconds, constraining the extent to which IFS studies can map the most nearby galaxies. Small FOV have also restricted IFS studies of large galaxy samples to pre-selected targets. Scaling up the fields of IFS instruments is challenging due to the limited number of spatial elements that can be imaged on a single CCD. To cost effectively scale up IFS capability in order to observe larger fields, the Visible Integral-field Replicable Unit Spectrograph (VIRUS) utilizes massive replication on an unprecedented 100-fold scale to be able to image ∼35,000 fibers over a ∼22 arcminute FOV with a single observation. VIRUS consists of up to 78 replicable units, each with two integral field spectrograph channels. The VIRUS design takes advantage of large-scale replication of simple units to significantly reduce engineering and production costs of building a facility instrument of this scale. With VIRUS being 156 realizations of the same spectrograph and the first to be replicated on this massive scale, I present analysis that uncovers the statistical variations in performance of these units along with an assessment of cost/tolerance trade offs of scaling up instrument capabilities through massively replicated designs. The VIRUS instrument was designed to conduct the Hobby Eberly Telescope Dark Energy Experiment (HETDEX) which intends to build a sample of nearly a million Lyα emitting galaxies (LAEs) from 1.9Item On the evolution of galaxy protoclusters from the epoch of reionization to cosmic noon(2022-08-10) Champagne, Jaclyn Bradli; Casey, Caitlin M.; Finkelstein, Steven L; Boylan-Kolchin, Michael; Hawkins, Keith; Decarli, RobertoOver the last 7–8 billion years, mature galaxy clusters, characterized by massive quiescent galaxy populations residing in > 10¹⁴ M [subscript ☉] dark matter halos, have become ubiquitous features of the cosmic web. It is theorized that these clusters are preceded by a proto-cluster stage, which form at much earlier times in filamentary dark matter overdensities and later collapse into a central dark matter halo. Identifying and characterizing protoclusters between the epoch of reionization and cosmic noon, during which time they are expected to undergo periods of rapid star formation and evolution prior to gravitational collapse, remains in its nascent stages. With a heterogeneous mix of selection techniques, spectroscopic completeness, area coverage, and wavelength coverage, we are still vitally lacking a statistically complete catalog of protoclusters — and even more so a general understanding of their physical properties. This doctoral thesis addresses these questions twofold by: 1) using z ∼ 6 quasars as tracers of overdensities at multiple wavelengths, and 2) presenting a comprehensive X-ray to radio case study of a massive protocluster at z = 2.5. The first half of this thesis focuses on understanding the environments of the brightest quasars at z > 6, under the hypothesis that quasars hosting > 10⁹ M [subscript ☉] black holes signal regions of accelerated growth and mass buildup in the early Universe. In two separate studies, I present the results of searches for enhanced star formation in the vicinities of quasars, using two complementary tracers of star–forming galaxies. Using data from the Atacama Large Millimeter Array, I show that a search for extreme dust–obscured galaxies via millimeter continuum emission yields inconclusive results concerning our ability to detect a true overdensity signal. Using the Hubble Space Telescope to search for the more abundant and less massive population of Lyman break galaxies, I show a heterogeneity of overdensity signals near these quasars. The second half of this thesis focuses on multiwavelength observations of known protoclusters at lower redshifts, where more observational tools are available to constrain their environments. I present an analysis of the member galaxies within a structurally complex protocluster core at z = 2.5 located in the COSMOS extragalactic field, using data from the Atacama Large Millimeter Array, the Very Large Array, and the COSMOS archive. I evaluate possible evolutionary hypotheses on the basis of the morphology of the cold gas needed for future star formation, the spatial distribution of its member galaxies, and the existence of a marginal X-ray detection that all present a challenge to our cosmological understanding of virial collapse of clusters during this epoch. Finally, I present a future outlook on further case studies and large surveys which will be made possible by next generation facilities.Item Probing galaxy evolution by unveiling the structure of massive galaxies across cosmic time and in diverse environments(2013-08) Weinzirl, Timothy Michael; Jogee, ShardhaHow galaxies form and evolve is one of the primary outstanding problems in extragalactic astronomy. I conduct a quantitative census of the relative importance of the major structural components (flattened and dynamically cold disk-dominated components versus puffy and dynamically hot spheroidal or triaxial bulges/ellipticals) in massive galaxies over cosmic time and across different environments in order to explore how galaxies evolve under the action of the various assembly mechanisms (major mergers, minor mergers, gas accretion, and internal secular processes) in these different regimes. I perform three inter-related analyses focusing on massive galaxies from z ~ 0 - 3 in both field and rich cluster environments. Important strengths of this thesis include the use of high-resolution, panchromatic imaging from some of the largest and deepest galaxy surveys with the Hubble Space Telescope (HST), Spitzer, and Chandra space telescopes, and also the inclusion of detailed comparisons between the empirical data and hierarchical ΛCDM-based models of galaxy evolution.Item Pseudobulges in disk galaxies : growth, structure and frequency in the local Universe(2010-08) Fisher, David Bradley; Kormendy, J. (John); Evans II, Neal J.; Bender, Ralf; Gebhardt, Karl; Jogee, ShardhaContrary to historic assumptions, bulges in the local Universe present a heterogeneous class of objects. Observations indicate that bulges are bimodal in structure, interstellar medium, stellar populations and dynamical state. Using observations in the UV, optical, near-infrared and mid-infrared we study the nature of local bulge-disk galaxies. The aim is first to find consistent means to differentiate different bulge types. Then we can use these diagnostic methods to study the properties of bulges of each type, thereby better understanding the possible formation mechanisms of each type. Finally, we will use these diagnostic methods to determine how many of each type of bulge exists in the local Universe, and thus understand how the heterogeneity of bulges may affect our understanding of galaxy evolution. Using 3.6-8.0 micron colors we show that dichotomy in bulge morphology is closely tied to the dichotomy in bulge interstellar medium. We find that those bulges with active interstellar medium, per unit stellar mass, have morphological features commonly found in disks (e.g. nuclear spirals, bars and rings). We follow this up with more robust star formation rates, as measured by linear combining UV and 24 micron luminosity, and determine that the boundary is near specific star formation rate ~30 Gyr⁻¹. We also find that the shape of bulge surface brightness profiles correlates well with morphology. When parameterized by a Sérsic function, we find that bulges with n[subscript b]<2 have disk-like morphology and those bulges with n[subscript b]>2 have morphology that is very similar to that of an elliptical galaxy. We thus conclude that bulges with disk-like nuclear morphology, specific star formation rate that is less than 30 Gyr⁻¹, and/or Sérsic index n[subscript b]<2 represents a distinct class of object. We refer to these bulges as "pseudobulges" and the complimentary set of bulges that are inactive, with high Sérsic index, and morphologically like elliptical galaxies is referred to as "classical bulges." We find that a significant amount of evidence points to pseudobulges and classical bulges originating from separate formation mechanisms. First, we rule out the possibility that pseudobulges are the result solely from mass dependent phenomenon. Rather, pseudobulges and classical bulges over lap significantly in mass, luminosity and size. Also, they are found in galaxies of similar mass, luminosity and size. Therefore, pseudobulges are not simply a low-mass phenomenon of the same process. Also, we find that many of the properties of pseudobulges are connected to properties of the outer disk. We find that the half-light radius of pseudobulges correlates linearly with the scale-length of the outer disk. Furthermore, this correlation does not exist for classical bulges. Also, the mass of pseudobulges correlates with the mass of the outer disk. We find that the star formation rate density of pseudobulges is a function of the stellar mass of the exponential outer disk such that pseudobulges with high star formation rate densities only occur more massive stellar disks. Thus it appears that both structure and growth of pseudobulges is a function of the properties of the outer disk. However, classical bulges do not show the same correlations. Also, we find that the star formation rate density of pseudobulges positively correlates with the mass density, classical bulges do not show an analogous correlation. If secular growth were responsible for the formation of pseudobulges, such a correlation should exist. Furthermore, we find that the specific star formation rates of most pseudobulges are high enough to account for the stellar mass within the typical ages of disk (~10 Gyr). We also show that classical bulges participate in the same structural parameter correlations as elliptical galaxies. Just like elliptical galaxies, as classical bulges become brighter they also become larger in radius, lower in surface density, and have higher Sérsic index. However pseudobulges behave very differently. There is little-to-no correlation between the size of pseudobulges and the luminosity, surface brightness or Sérsic index. We stress that this observation extends of 9 magnitudes in brightness. Therefore the size of pseudobulges, has thus far only been found to correlate with the size of the outer disk. Furthermore we find that pseudobulges show a positive correlation between surface density and luminosity. The behavior of pseudobulges in these parameter correlations implies that they are not virialized stellar systems that have experienced violent relaxation. Thus it is likely that the formation of pseudobulges is not like that of elliptical galaxies and classical bulges. Furthermore, the connection between pseudobulge properties and those of their associated outer disk seem to favor long-term growth that is more likely to be driven by disk processes, commonly called "secular evolution." Finally we show that the dichotomy of bulge types has a strong influence on our understanding of galaxy evolution. We find that global galaxy properties are tied to the bulge dichotomy. Galaxies with pseudobulges are found to be in "blue sequenc" galaxies and those with classical bulges are found to be in "red sequence" galaxies. A large body of literature has shown that blue and red galaxies appear to be distinct classifications of galaxies. The correlation with bulge type implies that the bulge dichotomy may be also be a consequence of the bimodal nature of galaxy evolution. Finally, we show that in the local Universe pseudobulges are by far the most common type of massive galaxy. We find that only 17% of galaxies have a detectable classical bulge. Also we show that over 3/4 of the star formation in spiral and elliptical galaxies in the local Universe occurs in galaxies with pseudobulges. Thus understanding pseudobulges is a necessary step to understanding the processes that have lead to the population of galaxies in the nearby Universe.Item Studying star formation at low and high redshift with integral field spectroscopy(2011-05) Blanc, Guillermo; Gebhardt, Karl; Evans, Neal J.; Hill, Gary J.; Bromm, Volker; Gawiser, EricIn this thesis I focus mainly in studying the process of star formation in both high redshift, and local star forming galaxies, by using an observational technique called integral field spectroscopy (IFS). Although these investigations are aimed at studying the star formation properties of these objects, throughout this work I will also discuss the geometric, kinematic, and chemical structures in the inter-stellar medium of these galaxies, which are intimately connected with the process of star formation itself. The studies presented here were conducted under the umbrella of two different projects. First, the HETDEX Pilot Survey for Emission Line Galaxies, where I have studied the properties of Ly-alpha emitting galaxies across the 2Item The birth of cosmic complexity(2018-06-15) Jaacks, Jason Dale; Bromm, Volker; Finkelstein, Steve L.; Jogee, Shardha; Boylan-Kolchin, Mike; Milosavljevic, Milos; Yoshida, NaokiIn this thesis, we construct custom built sub-grid models for the first and second generation of stars, the so-called Population III and II (Pop III/II). Implementing them in the state of the art hydrodynamical/N-body code GIZMO, we explore the legacy left by star formation processes in the first billion years of the Universe. With this powerful tool, we are able to create a virtual universe in a computational box with which we can study, in detail, the processes of star and galaxy formation. This technique is well suited to investigate epochs in cosmic history which are currently still beyond the reach of existing telescopes. More specifically, we examine how Pop III stars, which form from primordial, metal-free gas, leave behind a legacy of metal enrichment, thus setting the stage for the observable second generation of stars and first galaxies. They also begin the process of creating the basic chemical building blocks, the elements beyond H and He, for everything we know. We have found that Pop III star formation continues at a high rate down to ~750 million years after the Big Bang. While we find that Pop III dominated galaxies are likely to remain beyond our view, the inferred high rate of star formation could lead to the detection of the theorized pair-instability supernova (PISN), thought to be the consequence of the death of high mass Pop III stars. We also find that the metal enrichment provided by the death of Pop III stars is insufficient to significantly redden the spectrum from the first galaxies, but that it is critical to determining where and when the second generation of stars forms. Finally, we are able to quantify the number density of galaxies with specific brightness to determine that the number of galaxies at low luminosities assumes a near-plateau value. This is in contrast to the current paradigm, where it is assumed that this number will continue to grow along a power-law track. With the launch of the next generation James Webb Space Telescope (JWST) on the horizon, this thesis provides key constraints for future frontier observations.