<p> Red giants with solar-like oscillations are astrophysical laboratories for probing the Milky Way. The <i>Kepler </i>Space Telescope revolutionized asteroseismology by consistently monitoring thousands of targets, including several red giants in eclipsing binaries. Binarity allows us to directly measure stellar properties independently of asteroseismology. In this dissertation, we study a subset of eight red giant eclipsing binaries observed by <i> Kepler</i> with a range of orbital periods, oscillation behavior, and stellar activity. Two of the systems do not show solar-like oscillations at all. We use a suite of modeling tools to combine photometry and spectroscopy into a comprehensive picture of each star's life. One noteworthy case is a double red giant binary. The two stars are nearly twins, but have one main set of solar-like oscillations with unusually low-amplitude, wide modes, likely due to stellar activity and modest tidal forces acting over the 171 day eccentric orbit. Mixed modes indicate the main oscillating star is on the secondary red clump (a core-He-burning star), and stellar evolution modeling supports this with a coeval history for a pair of red clump stars. The other seven systems are all red giant branch stars (shell-H-burning) with main sequence companions. The two non-oscillators have the strongest magnetic signatures and some of the strongest lifetime tidal forces with nearly-circular 20-34 day orbits. One system defies this trend with oscillations and a 19 day orbit. The four long-period systems (> 100 days) have oscillations, more eccentric orbits, and less stellar activity. They are all detached binaries consistent with coevolution. We find the asteroseismic scaling laws are approximately correct, but fail the most for stars that are least like the Sun by systematically overestimating both mass and radius. Strong magnetic activity and tidal effects often occur in tandem and act to suppress solar-like oscillations. These red giant binaries offer an unprecedented opportunity to test stellar physics and are important benchmarks for ensemble asteroseismology. Future asteroseismic studies should know they are excluding magnetically active stars and close binaries and be aware that asteroseismic masses and radii are both overestimated. </p>

<p> In this thesis, I explore two topics in exoplanet science. The first is the prevalence of Earth-size planets in the Milky Way Galaxy. To determine the occurrence of planets having different sizes, orbital periods, and other properties, I conducted a survey of extrasolar planets using data collected by NASA&rsquo;s <i>Kepler Space Telescope</i>. This project involved writing new algorithms to analyze <i>Kepler</i> data, finding planets, and conducting follow-up work using ground-based telescopes. I found that most stars have at least one planet at or within Earth&rsquo;s orbit and that 26% of Sun-like stars have an Earth-size planet with an orbital period of 100 days or less. </p><p> The second topic is the connection between the properties of planets and their host stars. The precise characterization of exoplanet hosts helps to bring planet properties like mass, size, and equilibrium temperature into sharper focus and probes the physical processes that form planets. I studied the abundance of carbon and oxygen in over 1000 nearby stars using optical spectra taken by the California Planet Search. I found a large range in the relative abundance of carbon and oxygen in this sample, including a handful of carbon-rich stars. I also developed a new technique called SpecMatch for extracting fundamental stellar parameters from optical spectra. SpecMatch is particularly applicable to the relatively faint planet-hosting stars discovered by <i>Kepler</i>.</p>

<p> One of the most important scientific discoveries to be had this century is the spectroscopic characterization of Earth-like exoplanets to determine the occurrence rate of worlds capable of supporting life and to potentially answer: are we alone in the universe? To accomplish these lofty goals requires an advancement in the technology to separate the overwhelming starlight from that of the exoplanet. I believe starshades are the key technology that will enable these discoveries within our lifetime. This dissertation work is a contribution to the advancement of starshade technology to put us on the path towards discovery.</p><p> In this dissertation I present a number of suborbital methods developed for testing small-scale starshades, which include a Vertical Takeoff Vertical Landing rocket, the surface of a dry lake bed, and the heliostat of a solar telescope. The results from our high contrast observations are used to validate the optical model I developed to conduct tolerance analyses that will drive future starshade designs. The results from testing a formation flying sensor on the VTVL rocket demonstrate the rocket&rsquo;s potential for conducting starshade experiments in the stratosphere.</p><p> This dissertation (along with [Novicki, et al. (2016)]) presents the first astronomical observations with a starshade that provide photometric measurements of stars, previously unobserved in the visible spectrum, in the proximity of Vega. These observations led to the development of a visual feedback system for the heliostat that allows us to push farther in separation and inner working angle. These high contrast observations were made using a starshade in the most flight-like configuration (in terms of Fresnel number, inner working angle, and resolution) to date.</p><p> The results of this dissertation have helped demonstrate the effectiveness and practicality of starshades for starlight suppression and have outlined a path forward to further advance starshade technology through optical testing and high contrast astronomy.</p>

<p> This thesis reports on the characterization of the thermal and chemical distribution of Jupiter&rsquo;s polar regions. The quantities are derived from mid-infrared images covering all longitudes at unprecedented spatial resolution using the COMICS instrument at the Subaru Telescope on the nights of January 24 and 25, 2016. Because of Jupiter&rsquo;s slight axial tilt of 3&deg; and low angular resolution and incomplete longitudinal coverage of previous mid-infrared observations, the physical and chemical properties of Jupiter&rsquo;s polar regions have been poorly characterized. In advance of the exploration of the structure of Jupiter&rsquo;s polar regions by the Juno spacecraft, this study focuses on mapping the 3-dimensional structure of Jupiter&rsquo;s polar regions, specifically to characterize the polar vortices and compact regions of auroral influence. Using mid-infrared images taken in the 7.8 &mu;m - 24.2 &mu;m range, the 3-dimensional temperature field, para-H2 fraction, aerosol opacity, and the constraint on the distribution of gaseous-NH3 are determined on a range from 400 mbar to 100 mbar. Retrievals of these atmospheric parameters were performed using NEMESIS, a radiative transfer forward model and retrieval code. Results indicate that there are vortices at both poles, each with very distinct boundaries approximately 70&deg; latitude in the north and -75&deg; latitude in the south. The boundaries can be defined by sharp thermal gradients extending at least from the upper troposphere (500 mbar of atmospheric pressure) and into the stratosphere (0.1 mbar of atmospheric pressure). These polar regions are characterized by lower temperatures and lower para-hydrogen concentration, compared with the regions immediately outside the vortex boundaries.</p>

<p> Studies of scaling relations in groups and clusters of galaxies have shown that the X-ray properties of groups deviate the most from the self-similar prediction. This is because groups are more affected by non-gravitational processes due to their shallower potential well, a behaviour which makes groups an ideal class of systems for the study of the impact of feedback. From the observational point of view, the study of the X-ray properties of groups, especially at high redshifts is hindered by their lower surface brightness compared to their more massive counterparts. We present the result from the Chandra Deep Group Survey, a survey dedicated to find high redshift groups in the deepest observations available in the Chandra archive. We found 26 groups and 36 clusters with available redshifts, with largest redshift being 1.3. We have used this sample to investigate the evolution of cool cores in these two classes of systems using cooling time divided by the age of the cluster as a parameter to describe the cooling state. We have found that groups and clusters have similar evolution in their cool core properties. Both classes of systems have a wide spread in the cool core parameter at low redshifts, which then narrows at high redshifts showing a lack of strong cool core systems. </p>

<p>A high resolution measurement of the distribution of star formation within galaxies is key to understanding the emergence of galactic structure. The aim of this thesis is to understand how the structure of galaxies is built by developing a new method to spatially resolve their star formation. Using Ha maps for 2676 galaxies, this thesis shows where star formation is distributed in galaxies during the epoch 0.7 &lt; <i>z</i> &lt; 1.5 when a third of the total star formation in the history of the universe occurred. Across the star formation rate - stellar mass plane (the "main sequence"), star formation is `spatially coherent': in galaxies with higher than average star formation rates, Ha is enhanced throughout the disk; similarly, in galaxies with low star formation rates Ha is depressed throughout the disk. This places constraints both on the mechanisms for enhancing and quenching star formation as well as on how the structure of galaxies is built. The disk scale length of star formation in galaxies is larger than that of the stars, a direct demonstration that the disks of galaxies grow inside-out. While most star formation in most galaxies occurs in disks, not all of it does. With the first spatially resolved measurement of the Balmer decrement at <i>z</i> > 1, it can be seen that galaxies with M_* > 10¹⁰M[special characters omitted] have significant dust attenuation toward their centers. This means that we are witnessing the build-up of the dense stellar cores of massive galaxies through dust-obscured in-situ star formation. The most massive galaxies are thought to have formed their dense stellar cores at even earlier cosmic epochs. This thesis presents the first confirmed example of a massive galaxy core in the process of formation at <i>z</i> = 2.3. It has one of the highest velocity dispersions ever measured for a normal star forming galaxy and also appears to be building through very dense, dust-enshrouded star formation. </p>

<p> Feedback from active galactic nuclei (AGN) is thought to regulate the growth of supermassive black holes (SMBHs) and galaxies. The most direct evidence of AGN feedback is probably galactic outflows. This thesis addresses the link between SMBHs and their host galaxies from four different observational perspectives. First, I study the local correlation between black hole mass and the galactic halo potential (the <i>M</i><i>BH</i> &ndash; <i> V</i>_c relation) based on Very Large Array (VLA) HI observations of galaxy rotation curves. Although there is a correlation, it is no tighter than the well-studied <i>M</i>_BH &ndash; &sigma;* relation between the black hole mass and the potential of the galactic bulge, indicating that physical processes, such as feedback, could link the evolution of the black hole to the baryons in the bulge. In what follows, I thus search for galactic outflows as direct evidence of AGN feedback. Second, I use the Atacama Large Millimeter Array (ALMA) to observe a luminous obscured AGN that hosts an ionized galactic outflow and find a compact but massive molecular outflow that can potentially quench the star formation in 10</p><p>6 years.The third study extends the sample of known ionized outflows with new Magellan long-slit observations of 12 luminous obscured AGN. I find that most luminous obscured AGN (<i>L</i>_bol > 10⁴⁶ ergs s^&ndash;1) host ionized outflows on 10 kpc scales, and the size of the outflow correlates strongly with the luminosity of the AGN. Lastly, to capitalize on the power of modern photometric surveys, I experiment with a new broadband imaging technique to study the morphology of AGN emission line regions and outflows. With images from the Sloan Digital Sky Survey (SDSS), this method successfully constructs images of the [OIII]&lambda;5007 emission line and reveals hundreds of extended emission-line systems. When applied to current and future surveys, such as the Large Synoptic Survey Telescope (LSST), this technique could open a new parameter space for the study of AGN outflows. In summary, through multi-phase and multi-scale galactic outflows, AGN feedback can link the growth of SMBHs with the evolution of galaxies. </p>

<p> We study the problem of separating stars and galaxies in the Hyper Suprime-Cam (HSC) multi-band imaging data at high galactic latitudes. We show that the current separation technique implemented in the HSC pipeline is unable to produce samples of stars with <i>i</i> 24 without a significant contamination from galaxies (> 50%). We study various methods for measuring extendedness in HSC with simulated and real data and find that there are a number of available techniques that give nearly optimal results; the extendedness measure HSC is currently using is among these. We develop a star/galaxy separation method for HSC based on the Extreme Deconvolution (XD) algorithm that uses colors and extendedness simultaneously, and show that with it we can generate samples of faint stars keeping contamination from galaxies under control to <i>i</i> &le; 25. We apply our star/galaxy separation method to carry out a preliminary study of the structure of the Milky Way (MW) with main sequence (MS) stars using photometric parallax relations derived for the HSC photometric system. We show that it will be possible to generate a tomography of the MW stellar halo to galactocentric radii &sim; 100 kpc with &sim; 10⁶ MS stars in the HSC Wide layer once the survey has been completed. We report two potential detections of the Sagittarius tidal stream with MS stars in the XMM and GAMA15 fields at &ap; 20 kpc and &ap; 40 kpc respectively.</p>

<p> Studying dwarf galaxies can shed light on the original building blocks of galaxy formation. Most large galaxies are thought to be built up over billions of years through the collisions and mergers of smaller galaxies. The dwarf galaxies we see today are the evolved remnants of those building blocks, and by understanding their nature and evolution, we can study the raw ingredients of galaxy formation. </p><p> Blue Compact Dwarf galaxies (BCDs) and Almost Dark galaxies are at opposite extremes of today's population of dwarf galaxies. BCDs are exceptionally compact and host very intense starbursts, while Almost Dark galaxies are much more diffuse and have weak stellar populations. </p><p> This work studies the evolutionary context of BCDs by using deep, high-resolution images to study the detailed structure of their components, and by fitting our multi-wavelength observations with models to describe the properties of their stars, gas, and dust. BCDs appear to have exceptionally compact old stellar populations and unusually large star formation rates, when compared to typical dwarf galaxies. </p><p> By contrast, the optically faint, gas-dominated Almost Dark galaxies have extremely low star formation rates and weak stellar populations. In particular, one of the Almost Darks studied in this work has very unusual properties and is in disagreement with widely-studied scaling relations for large samples of galaxies. It appears to have too little stellar mass, a distribution of HI that is too extended to be supported by its modest rotation, and the highest well-measured gas mass-to-light ratio ever observed. </p><p> These two extreme classes may represent evolutionary stages that all galaxies pass through, and appear to be extreme ends of the broad continuum of dwarf galaxy properties. In order to use today's dwarf galaxies as windows into the building blocks of early galaxy formation, these unusual states and evolutionary pathways must be understood.</p>

<p> Galaxy star formation histories (SFHs) form a central thread of the cosmological narrative. Assessing and understanding them is therefore a central mission of the study of galaxy evolution. Although an ever-better picture is emerging of the build-up of the stellar mass of the <i>average</i> galaxy over time, the relevance of this track to the growth of <i>individual </i> galaxies is unclear. Largely, this ambiguity is due to the availability of only loose, ensemble-level constraints at any redshift appreciably greater than zero. In this thesis, I outline how these constraints &mdash; principally the cosmic star formation rate density, stellar mass function, and the star formation rate/stellar mass relation &mdash; shape empirically based SFH models, especially in terms of the diversity of paths leading to a given end-state. Along the way, I show that three models propose very different answers to this question, corresponding (largely) to three different interpretations of the scatter in instantaneous galaxy growth rates at fixed stellar mass. I describe how these interpretations affect one's stance on the fundamental importance of so-called galaxy "bimodality" and quenching mechanisms, the influence of environment, and the role starbursts play in galaxy evolution. Ultimately, I conclude that there is insufficient evidence at present to select one interpretation over all others, but suggest that the situation might soon be resolved by upcoming observations that could clearly identify which model (or hybrid) is the most accurate description of galaxy growth.</p>