Optical spectroscopy and modeling are applied to four independent problems related to the structure and evolution of galaxies. The problems cover a broad range of look-back time and galaxy mass. Integral field spectroscopy with low surface brightness sensitivity is the tool employed to advance our understanding of the distribution, interplay, and evolution of the stars, dark matter, and gas. First, I review development and commissioning work done on the VIRUS-P instrument. I then present a large sample of galaxies over redshifts 1.9<z<3.8 selected solely through their Lyman-alpha flux. This work is done as a pilot survey to the Hobby-Eberly Telescope Dark Energy eXperiment (HETDEX). I create a redshift catalog of 397 galaxies discovered over 169 square arcsecs taken over 113 nights. Second, I study a high redshift (z=3.4) radio galaxy halo by mapping the Lyman-alpha velocity field. The signal extends far beyond the optical and radio extents of the system. Plausible, but non-unique, models are made to explain the Lyman-alpha signal that require a very large reservoir of neutral hydrogen (>= 10E12 solar masses). Third, I study the dark matter halo profile in a nearby late-type dwarf galaxy in the context of the "core-cusp" controversy. N-body simulations predict such galaxies to have cuspy dark matter halos, while HI rotation curves and more recent hydrodynamical simulations indicate that such halos may instead be strongly cored. I measure the spatially resolved stellar velocity field and fit with two-integral Jeans models. A cuspy halo is preferred from the stellar kinematics. The mass models from stellar and gaseous kinematics disagree. The gas models assume circular motion in an infinitely thin disk which is likely unrealistic. The stellar kinematics presented are the first measurements of a collision-less tracer in such galaxies. Fourth, I attempt to measure diffuse H-alpha emission, fluoresced by the metagalactic UV background, in the outskirts of a nearby gas rich galaxy. I do not make a detection, but the deep flux limit over a large field-of-view places the most sensitive limit to-date on the UV background's photoionization rate of Gamma(z=0)<1.7x10E-14 1/s at 5 sigma certainty. / text

My dissertation focuses on a relatively new field of study: the region immediately around galaxies known as the circumgalactic medium (CGM). The CGM holds vast quantities of mass and metals, yet its connection to galaxies is not well understood. My work uses cosmological hydrodynamic simulations and comparisons to data from Hubble's Cosmic Origins Spectrograph (COS) to understand the CGM's connection to galaxy evolution, gas accretion, outflows, star formation, and baryon cycling. This includes studies of the CGM's extent and physical conditions; the cause and nature of outflows; gas dynamics, including the first comprehensive study of tracers of inflowing and outflowing gas at low redshift (z=0.25); and direct comparison of theoretical results to observational data. Chapter 1 introduces my research and show its connection to galaxy evolution. Chapter 2 investigates hydrogen and metal line absorption around low-redshift galaxies in cosmological hydrodynamic simulations. This chapter studies different models for stellar outflows, physical conditions, and dependencies on halo mass. Chapter 3 examines the flow of gas into, out of, and around galaxies using a novel particle tracking technique. This chapter examines the baryon cycle in detail for our preferred model of stellar outflows. Chapter 4 compares our model results, including two separate prescriptions for outflows, with data from COS. We contrast these wind models, showing how they cycle baryons differently, and show degeneracies in observational diagnostics. In Chapter 5, I summarize and discuss plans for future research in this field, and how it can be more fully leveraged to understand galaxy evolution.

I investigate the emission properties of the molecular interstellar medium in protoplanetary disks and galaxy mergers, though focus largely on the latter topic. I utilize both numerical models as well as observations to relate the emission characteristics to physical models for the formation and evolution of gas giant planets and galaxies. The main results of this thesis follow. (1) Gas giant protoplanets may be detectable via self-absorption signatures in molecular emission lines with sufficiently high critical density. Given the spatial resolution of e.g. ALMA, gas giant planets in formation may be directly imageable. (2) Starburst and AGN feedback-driven winds in galaxies can leave imprints on the molecular line emission properties via morphological outflows and high velocity peaks in the emission line spectra. Methods for distinguishing between high velocity peaks driven by dynamics versus those driven by winds are discussed. (3) CO line widths on average trace the virial velocity of z ∼ 6 quasar host halos. Thus, if the earliest quasars formed in ∼1013 M ⊙ halos, they are predicted to have broad molecular line widths. Selection effects may exist which tend quasars selected for optical luminosity toward molecular line widths narrower than the slightline-dependent mean. (4) Using the SMT, I observe a roughly linear relation between infrared luminosity and CO (J=3-2) luminosity in local galaxies confirming the results of recently observed L(IR)-HCN (J=1-0) relations. Subsequent modeling shows that observed SFR-molecular line luminosity relations owe to the average fraction of subthermally excited gas in galaxies, and are simply reflective of the assumed Schmidt law governing the SFR.

I investigate the chemical evolution of the Universe in a series of cosmological hydrodynamic simulations with the purpose of finding a self-consistent evolutionary scenario of galaxy formation able to reproduce key observables focusing on the enrichment of the intergalactic medium (IGM). The most successful models I run and analyze use the scalings of momentum-driven feedback whereby UV photons generated during the Main Sequence stage accelerate dust-driven winds while providing a significantly larger energy budget than from supernovae alone. The success of this outflow model relies on its ability to drive highly mass-loaded winds from small galactic haloes. These feedback relations, supported by observations of local starburst, are inserted into simulations at all epochs, reproducing observables including the C IV column density and linewidth distributions at z=6->1.5 and the O VI forest at z=0-0.5. Outflows at z>=5 propagate early nucleosynthetic products traced by C IV and lower ionization species into an otherwise metal-free IGM. Continual outflows at the peak ages of star formation (z=5->1.5) produce a non-evolving cosmic mass density of C IV despite continual enrichment increasing IGM metallicity by a factor of ten. The z=0-0.5 O VI forest is composed of weaker absorbers tracing photo-ionized diffuse IGM metals, sometimes injected by primordial galaxies, and stronger absorbers tracing recently injected metals, often unable to escape their parent haloes and sometimes collisionally ionized. Tracking the individual histories of metals in outflows shows the average outflow travels ~100 physical kpc and returns to galaxies on an average timescale of 1-2 Gyr; this result implies metals in superwinds do not remain in the IGM for a Hubble time and are more likely to rejoin galaxies. Metal absorbers aligned with Lyman-alpha are examined in detail, finding that the two often trace different phases of gas with the former tracing an inhomogeneous distribution of metals exhibiting turbulence imparted during the outflow phase dissipating on a Hubble timescale. I find this is the first model to self-consistently reproduce the wide range of IGM observables spanning the history of heavy metal production while being consistent with key galaxy observables. The link between star formation and galactic superwinds requires that a successful model of galaxy formation reproduces both the evolution of galaxies and the IGM.

We present a precision study of large-scale structure from large galaxy redshift surveys. We focus on two main subjects of large-scale structure: precisioncosmology with baryon acoustic oscillations from large galaxy surveys and the evolution of galaxy clustering for passively flowing galaxies.The baryon acoustic oscillations in galaxy redshift surveys can serve as an efficient standard ruler to measure the cosmological distance scale, i.e., theangular diameter distances and Hubble parameters, as a function of redshift, and therefore dark energy parameters. We use a Fisher matrix formalism to show that such a standard ruler tests can constrain the angular diameter distances and Hubble parameters to a precision of a few percent, thereby providing robust measurements of present-day dark energy density and its time-dependence.We use N-body simulations to investigate possible systematic errors in the recovery of the cosmological distance scale from galaxy redshift surveys. We show that the baryon signature on linear and quasi-linear scales is robust against nonlinear growth, redshift distortions, and halo (or galaxy) bias, albeit partial obscuration of the signature occurs due to nonlinear growth and redshift distortions.We present the improved Fisher matrix formalism which incorporates the Lagrangian displacement field to describe the nonlinear effects on baryon signature as a function of time and scale. We present a physically motivated, reduced 2-dimensional fitting formula for the full Fisher matrix formalism. We show that distance precision from the revised formalism is in excellent agreement with distance precision from N-body simulations.Finally, we present a numerical study of the evolution of galaxy clustering when galaxies flow passively from high redshift to low redshift, that is, without merging or new formations. We show that passive flow evolution induces interesting characteristics in the galaxy distribution at low redshift: we find an asymptotic convergence in galaxy clustering and halo occupation distribution regardless of the initial distribution of galaxies.

We study specific aspects of the relationship between the stellar content and the intracluster media (ICM) of galaxy clusters. First, we attempt to solve the long-standing difficulty in explaining the highly enriched ICM by including a previously unaccounted for stellar component: the intracluster stars. To determine the relative contributions of galactic and intracluster stars to the enrichment of the intracluster medium (ICM), we present X-ray surface brightness, temperature, and Fe abundance profiles for a set of twelve galaxy clusters for which we have extensive optical photometry. Assuming a standard IMF and simple chemical evolution model scaled to match the present-day cluster early-type SN Ia rate, the stars in the brightest cluster galaxy (BCG) plus the intracluster stars (ICS) generate 31⁺¹¹₋₉%, on average, of the observed ICM Fe within r₅₀₀(∼ 0.6 times r₂₀₀, the virial radius). Because the ICS typically contribute 80% of the BCG+ICS Fe, we conclude that the ICS are significant, yet often neglected, contributors to the ICM Fe within r₅₀₀. However, the BCG+ICS fall short of producing all the Fe, so metal loss from stars in other cluster galaxies must also contribute. By combining the enrichment from intracluster and galactic stars, we can account for all the observed Fe. These models require a galactic metal loss fraction (0.84(−0.14)^(+0.11)) that, while large, is consistent with theoretical models of Fe mass not retained by galactic stars. The SN Ia rates, especially as a function of galaxy environment and redshift, remain a significant source of uncertainty in further constraining the metal loss fraction. Second, we study the effects of ram-pressure stripping on infalling galaxies using a warm molecular hydrogen (H₂) as a tracer by carrying out a Spitzer infrared spectrograph (IRS) survey of four galaxies with signatures of ram-pressure stripping. We have discovered two galaxies, ESO 137-001 and NGC 4522, with warm H₂ tails stretching 20 kpc and 4 kpc in length, respectively. In the case of ESO 137-001 where we measure a warm H₂ mass loss rate of ∼ 2 − 3 M⊙ yr⁻¹, we estimate that the galaxy will lose all of its gas in a single pass through the cluster core. Strong warm H₂ emission is detected in one other galaxy, CGCG 97-073, which a region within its tail that is mainly dominated by H₂ emission. The warm H₂ observed in these three galaxies share similar temperature and column density properties with warm H₂ masses ranging from 10⁶ − 10⁸ M⊙. From a comparison with the SINGS warm H₂ sample, our results indicate that these galaxies experiencing significant ram-pressure stripping show anomalously high warm H₂ emission that cannot be explained purely from star formation. This adds credence to the hypothesis that H₂ within these galaxies is being shock-heated from the interaction with the ICM. We also discover that stripping of warm and hot dust, as measured at 8 μm and 24 μm, is a common feature of the galaxies observed in our sample. In the case of NGC 4522, we capture the turbulent nature of the stripping process. We measure the star formation rates using published Hα and measured 24 μm luminosities for all of our galaxies and find that some of them have suppressed star formation rates compared to similar mass counterparts in the field. We find a possible association between Hα and warm H₂ emission in three of the four galaxies observed. We conclude that the variation of H₂ properties observed in our sample is likely due to the galaxies being in different stages of ram-pressure stripping. Finally, we report on our efforts to improve the performance of the Lochkeed Arizona Infrared Spectrometer (LAIRS), a near-IR, tunable filter imager. We have made significant progress in identifying the sources of key issues such as the a highly asymmetric line profile and the unstable performance of the servo controller at the MMT. Solutions have been implemented for these issues, such as a revised mounting strategy for the tunable filter plates and a completely new controller with higher bandwidth. Significant progress has been made towards resolving these issues, but a few issues remain before LAIRS meets all of its requirements.

Blue compact galaxies (BCGs) are gas-rich star-forming low redshift galaxies with low metallicities. In some cases the relative strength of the starburst can be so high that it completely dominates the light output of the galaxy, an obstacle which has been countered by deeper optical imaging data and observations in the near infra-red (NIR) regime. This has revealed an older population referred to as the "host". In an effort to study the hosts of BCGs we have analyzed new and extremely deep UBVRIHKs imaging data for 46 high and low luminosity BCGs. For several BCGs the data reveal previously undetected extended low surface brightness components beyond the μB~26 mag arcsec-2 isophote. These are predominantly the luminous BCGs in the sample, and they show tails, plumes, optical bridges between companion galaxies, and other signs of merging or strong tidal interactions. The low luminosity BCGs, on the other hand, are well represented by an exponential disk profile down to the reliability limit of the data at a surface brightness level of μB~28 mag arcsec-2. The burst and host populations are examined separately. The integrated colors of both are compared to predictions from spectral evolutionary models, giving an indication of their respective ages and metallicities. Our analysis suggests that for the luminous BCGs a strong contribution by nebular emission is present almost down to the Holmberg radius, invalidating the host structural parameters obtained from brighter isophotes. Possible evolutionary links to quiescent galaxies like dEs, dIs, and LSBGs are explored by examining the structural parameters derived from two radial ranges typically assumed to be dominated by the underlying host galaxy. In this parameter space the luminous BCGs in our sample deviate from their low luminosity counterparts and from BCG data in the literature. They are instead consistent with the structural properties of giant low surface brightness galaxies with central surface brightnesses μB≥23 mag arcsec-2. We further examine the asymmetry and concentration parameters for the sample and study the correlation between the minimum asymmetry distribution in the optical and NIR vs morphological class, concentration and integrated colors to identify mergers/tidally interacting galaxies. A shift in the asymmetry distribution occurs for low luminosity BCGs from the optical to the NIR. In contrast, we find that the flocculent asymmetry component (due to star formation) completely dominates the composite asymmetry of high luminosity BCGs. We introduce an alternative asymmetry measure which successfully traces the dynamical asymmetry component (due to merging/tidal interaction) of the host. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.</p>

We investigate the uses of gravitational lensing for analysing the dark matter haloes around galaxies, comparing galaxies within groups and clusters to those in the field. We consider two cases: when only photometric redshift data is available, and when spectroscopic redshift data is available for a sufficiently large sample of galaxies. For the case of data with photometric redshifts, we analyse the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 deg^2 of high-quality shape data. Using the photometric redshifts to estimate local density, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (~61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (~87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, we show that the subhaloes of HDE galaxies are less massive than those around LDE galaxies by a factor 0.65+/-0.12, significant at the 2.9 sigma level. A natural explanation is that the haloes of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ~40 kpc. For the case of data with spectroscopic redshifts, we analyse the GAMA-I and the ongoing GAMA-II surveys. We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups, using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 10^12 Msun to 10^15 Msun.

A number of stellar streams, moving and kinematic groups were identified in the Milky Way galaxy. Some of them are suspected to originate from accreted satellites. Can we also find such traces of ancient merger events in the solar neighbourhood? Helmi et al. (2006) identified three new coherent groups of stars in the Geneva-Copenhagen survey (Nordström et al. 2004) and suggested that those might correspond to remains of disrupted satellites. With the detailed chemical composition analysis of the newly identified kinematic group we aim to contribute to the Galactic substructure studies. The main aim of the study is to perform a high-resolution spectroscopic elemental abundance analysis in stars belonging to one of the newly identified kinematic groups and to compare the results with other stars in the Galactic disc. We performed the detailed chemical analysis of 21 stars attributed to Group 3 of the Geneva-Copenhagen survey and six comparison Galactic thin disc stars. The main atmospheric parameters and abundances of 22 chemical elements were determined. All programme stars are overabundant in oxygen and α-elements compared with the Galactic thin-disc. This abundance pattern has similar characteristics to those of the Galactic thick disc. The abundances of chemical elements produced predominantly by the r-process are overabundant in comparison with Galactic thin-disc dwarfs of the same metallicity. The abundances of iron-group elements and chemical elements produced mainly... [to full text] / Paukščių Tako galaktikoje yra identifikuota žvaigždžių srautų, judančių bei kinematinių grupių, kurių kilmė siejama su įkritusiomis galaktikomis. Aktualu ištirti, ar yra tokių senųjų substruktūrų pėdsakų mūsų Saulės aplinkoje? Helmi ir kt. (2006), panaudoję Nordström ir kt. (2004) Ženevos–Kopenhagos apžvalgos (ŽKA) katalogą, identifikavo tris naujas koherentines žvaigždžių grupes, kurios pasižymi išskirtiniais kinematiniais parametrais ir gali būti užgalaktinės kilmės. Šiuo disertacijos darbu siekiama prisidėti prie Galaktikos substruktūrų tyrimų, nustatant detalią cheminę vienos iš Helmi ir kt. identifikuotų žvaigždžių grupių sudėtį. Svarbu išsiaiškinant, ar ŽKA kinematinės grupės žvaigždžių atmosferų cheminė sudėtis skiriasi nuo Galaktikos disko žvaigždžių. Nustatėme 21 3–osios ŽKA kinematinės grupės bei 6 palyginamųjų plonojo disko žvaigždžių atmosferų pagrindinius parametrus bei 22 cheminių elementų gausas. Kinematinės žvaigždžių grupės deguonies ir α–elementų gausos yra padidėjusios lyginant su plonuoju disku ir yra panašios į storojo disko. Cheminių elementų, daugiausia pagaminamų s–procese, gausos ir geležies grupės elementų gausos yra panašios į to paties metalingumo plonojo disko nykštukių cheminių elementų gausas, o cheminių elementų, daugiausia pagaminamų r–procese, gausos yra padidėjusios lyginant su plonuoju disku. Panaši cheminė tirtos kinematinės grupės bei storojo Galaktikos disko sudėtis rodo, kad kinematinės žvaigždžių grupės ir storojo disko žvaigždžių... [toliau žr. visą tekstą]

Paukščių Tako galaktikoje yra identifikuota žvaigždžių srautų, judančių bei kinematinių grupių, kurių kilmė siejama su įkritusiomis galaktikomis. Aktualu ištirti, ar yra tokių senųjų substruktūrų pėdsakų mūsų Saulės aplinkoje? Helmi ir kt. (2006), panaudoję Nordström ir kt. (2004) Ženevos–Kopenhagos apžvalgos (ŽKA) katalogą, identifikavo tris naujas koherentines žvaigždžių grupes, kurios pasižymi išskirtiniais kinematiniais parametrais ir gali būti užgalaktinės kilmės. Šiuo disertacijos darbu siekiama prisidėti prie Galaktikos substruktūrų tyrimų, nustatant detalią cheminę vienos iš Helmi ir kt. identifikuotų žvaigždžių grupių sudėtį. Svarbu išsiaiškinant, ar ŽKA kinematinės grupės žvaigždžių atmosferų cheminė sudėtis skiriasi nuo Galaktikos disko žvaigždžių. Nustatėme 21 3–osios ŽKA kinematinės grupės bei 6 palyginamųjų plonojo disko žvaigždžių atmosferų pagrindinius parametrus bei 22 cheminių elementų gausas. Kinematinės žvaigždžių grupės deguonies ir α–elementų gausos yra padidėjusios lyginant su plonuoju disku ir yra panašios į storojo disko. Cheminių elementų, daugiausia pagaminamų s–procese, gausos ir geležies grupės elementų gausos yra panašios į to paties metalingumo plonojo disko nykštukių cheminių elementų gausas, o cheminių elementų, daugiausia pagaminamų r–procese, gausos yra padidėjusios lyginant su plonuoju disku. Panaši cheminė tirtos kinematinės grupės bei storojo Galaktikos disko sudėtis rodo, kad kinematinės žvaigždžių grupės ir storojo disko žvaigždžių... [toliau žr. visą tekstą] / A number of stellar streams, moving and kinematic groups were identified in the Milky Way galaxy. Some of them are suspected to originate from accreted satellites. Can we also find such traces of ancient merger events in the solar neighbourhood? Helmi et al. (2006) identified three new coherent groups of stars in the Geneva-Copenhagen survey (Nordström et al. 2004) and suggested that those might correspond to remains of disrupted satellites. With the detailed chemical composition analysis of the newly identified kinematic group we aim to contribute to the Galactic substructure studies. The main aim of the study is to perform a high-resolution spectroscopic elemental abundance analysis in stars belonging to one of the newly identified kinematic groups and to compare the results with other stars in the Galactic disc. We performed the detailed chemical analysis of 21 stars attributed to Group 3 of the Geneva-Copenhagen survey and six comparison Galactic thin disc stars. The main atmospheric parameters and abundances of 22 chemical elements were determined. All programme stars are overabundant in oxygen and α-elements compared with the Galactic thin-disc. This abundance pattern has similar characteristics to those of the Galactic thick disc. The abundances of chemical elements produced predominantly by the r-process are overabundant in comparison with Galactic thin-disc dwarfs of the same metallicity. The abundances of iron-group elements and chemical elements produced mainly... [to full text]