<p>The influence of environment in galaxy evolution has been observed in a wide range of environments, where in general red quiescent early-type galaxies preferentially reside in high-density regions. The aim of this thesis is to understand the role that galaxy groups, and in particular group dynamics, play in galaxy evolution.</p> <p>We examine substructure in rich groups at intermediate redshifts and find that 4/15 groups contain substructure, which is preferentially found on the group outskirts. Galaxies in groups with substructure have properties similar to the field, while the galaxies in groups with no substructure are similar to cluster populations. These results indicate that substructure galaxies do not feel the effects of the environment until well inside the group potential.</p> <p>We then study the evolution of group dynamics to z~1 and find that the fraction of non-Gaussian groups increases with redshift, while the fraction of groups with substructure remains constant. Additionally, we find that the quiescent fraction correlates with galaxy stellar mass, but has little or no dependence on group dynamical mass or state. However, we do observe some correlation between substructure and quiescent fraction for low mass galaxies.</p> <p>Finally, we investigate infalling subhalo galaxies to probe the importance of pre-processing in galaxy evolution. At r200 > 2, galaxies in subhaloes show enhanced quenching, when compared to non-subhalo galaxies. At these radii, the infall population dominates, indicating that enhanced quenching is due to the infalling subhalo population. Additionally, the fraction of groups with subhaloes is a function of halo mass, where more massive systems have a higher fraction of subhaloes. We conclude that for groups, pre-processing is insignificant; however, for the most massive clusters a significant fraction (∼ 25%) of the member galaxies have been pre-processed.</p> / Doctor of Philosophy (PhD)

We review the evidence for existence of a magnetic field of the galaxy and whatever evidence there is of an intergalactic magnetoionic medium. We then consider the magnetohydrodynamics (MHD) of such a medium. The formation of galaxies through purely gravitational means in an expanding universe is then reviewed. Next the role of magnetohydrodynamics in such a universe is analyzed for their effects on galaxy formation. Finally, the importance of MED behavior in the early universe is emphasized from physical considerations and from present day evidence. Appendices discuss isotropic cosmologies, magnetic fields in such a background, the detailed MHD perturbations, and similar MHD studies.

For a sample of collisional ring galaxies, archival Hubble Space Telescope images were used to compare individual star clusters and kpc-sized clumps of star formation to each other in a variety of ways. For each galaxy, instrument, and filter, the magnitude of the brightest cluster in a clump was compared to the magnitude of the entire clump, and the fraction of the flux of the clusters in a clump over the flux of the entire clump was calculated and compared to star formation rates. In addition, a cluster luminosity function for each galaxy was derived. Comparing the brightest cluster in a clump to the magnitude of the entire clump and the flux ratio to the star formation rate did not show any significant patterns. However, the α found for the galaxies tended to be much flatter than what had been found in previous research. The α found seemed to be affected by the size of the bin used in the luminosity function. Using this information, α could be calculated for other incredibly luminous galaxies to see if the trend of flatter α continues.

<p>Globular clusters have linear sizes (tidal radii) which are theoretically de- termined by their mass and by the gravitational potential of their host galaxy. However observationally, cluster sizes are simply a determination of where the cluster’s surface brightness profile becomes zero. This distance is also known as the limiting radius. While it is commonly assumed that the tidal radius and the limiting radius of a globular cluster are the same thing, it has yet to be validated. The purpose of this thesis is to explore the assumption that cluster tidal radii and limiting radii are equal by comparing the tidal radii of an observed and simulated globular cluster population.</p> <p>An established link between cluster tidal radii and limiting radii will yield new methods of utilizing globular clusters as tools for studying galaxies. If cluster sizes are truly imposed by the tidal field of the host galaxy, then tidal radii measurements can be used to trace the mass distribution within a galaxy, including the dark matter halo. Additionally, as we will demonstrate in this thesis, cluster sizes can also be used a tracer for the orbital anisotropy profile of a galaxy.</p> <p>To explore the assumption that tidal radii and limiting radii are equal, we utilize the globular cluster population of the Virgo giant M87. Unusually deep, high signal-to-noise images of M87 are used to determine the radius for approximately 2000 globular clusters. To compare with these observations, we simulate a globular cluster population that has the same characteristics to the observed M87 cluster population. These characteristics include cluster radial distribution, mass distribution, central concentration distribution and line of sight velocity dispersion. Placing these simulated clusters in the well-studied tidal field of M87, the orbit of each cluster is solved and the theoretical tidal radius of each cluster is determined. We compare the predicted relationship between cluster size and projected galactocentric distance found in our sim- ulation to observations in order to test whether a cluster’s tidal radius and limiting radius are equal. We find that for an isotropic distribution of cluster velocities, theoretical tidal radii are approximately equal to observed limiting radii. The simulation predicts the observed increase in cluster size with galac- tocentric distance, which is expected if tidal radii are dependent on the tidal field. Additionally, simulated cluster sizes are of the same order of magnitude as observed cluster sizes. However the simulation does underestimate cluster sizes in the inner regions of M87. To minimize the discrepancy between theory and observations, we further explore the effects of orbital anisotropy on cluster sizes, and suggest a possible orbital anisotropy profile for M87 which yields the best fit between theory and observations. Finally, we suggest multiple future studies which will aid in our understanding of tidal theory and in establishing a stronger link between tidal radii and limiting radii.</p> / Master of Science (MSc)

<p>Ultra/Luminous infrared galaxies (U/LIRGs) are some of the most amazing systems in the local universe exhibiting extreme star formation triggered by mergers. Since molecular gas is the fuel for star formation, studying the warm, dense gas associated with star formation is important in understanding the processes and timescales controlling star formation in mergers. We have used high resolution (∼2.3”) observations of the local LIRG Arp 299 to map out the physical properties of the molecular gas. The molecular lines 12CO J=3-2, 12CO J=2-1 and 13CO J=2-1 were observed with the Submillimeter Array and the short spacings of the 12CO J=3-2 and J=2-1 observations have been recovered using James Clerk Maxwell Telescope single dish observations. We use the radiative transfer code RADEX to measure the physical properties such as density and temperature of the different regions in this system. The RADEX solutions of the two galaxy nuclei, IC 694 and NGC 3690, show two gas components: a warm moderately dense gas with T_kin ∼ 30-500 K (up to 1000K for NGC3690) and n(H2)~0.3-3×10^3 cm^−3 and a cold dense gas with T_kin~10-30 K and n(H2) > 3 × 10^3 cm^−3. The overlap region is shown to have a well-constrained solution with T_kin ∼ 10-30 K and n(H2)~3-30 × 10^3 cm^−3. We estimate the gas masses and star formation rates of each region in order to derive molecular gas depletion times. The depletion time of each region is found to be about 2 orders of magnitude lower than that of normal spiral galaxies. This can be probably explained by a higher fraction of dense gas in Arp 299 than in normal disk galaxies.</p> / Master of Science (MSc)

<p>The study of ongoing mergers is vital to understanding how intense star bursts are triggered, and how luminous infrared galaxies and ultra luminous infrared galaxies are formed. The Antennae (NGC 4038/39), at a distance of only 24.9 Mpc, represents the nearest example of a major merger between two gas rich spirals and provides us with a unique laboratory for studying molecular gas and star formation. I have obtained two fully sampled observations of the Antennae using the Herschel SPIRE Fourier Transform Spectrometer which I have supplemented with JCMT CO J = 3 − 2 observations. I detect CO, CI and NII emission throughout both the overlap region and the nucleus of NGC 4038. I measured the integrated intensity of the CO J = 4−3 to 8−7 and find that the overlap region is brighter for all but the J = 4 − 3 line. I find that, in the nucleus of NGC 4038, the CO spectral line energy distribution peaks at the 4−3 transition, while in the overlap region it peaks at the 3−2 transition. I modelled the CO emission using the non-local thermal equilibrium radiative transfer code RADEX coupled with a Bayesian likelihood code. I find a warm (Tkin > 600K) lower density (nH2 ∼ 200cm−3) component of molecular gas in the nucleus of NGC 4038, and similarly in the overlap region (Tkin > 600 K, nH2 ∼ 300cm−3) and find widespread evidence for multiple components of molecular gas throughout the system. These warm components in both regions correspond to ~ 1% of the total molecular gas. I find no evidence of x-ray dominated regions, cosmic rays or turbulent heating being the primary source of heating throughout the galaxy, while photodissociation regions or supernova and stellar winds may be the primary source of heating throughout the galaxy.</p> / Master of Science (MSc)

<p>The currently-favoured cosmological paradigm, Lamda-CDM, predicts that galaxies are built up from smaller galaxies in a bottom-up process known as hierarchical merging. Lambda-CDM is extremely successful for large-scale structures, but is less so for the detailed features of individual galaxies. We can study these features - the galaxies’ foundations and the remnants of the smaller components that built them - only in the closest galaxies in which we can resolve individual stars. In this thesis, we use data from the Canada-France-Hawaii Telescope (CFHT)/MegaCam as part of the Pan-Andromeda Archaeological Survey (PAndAS) to observe M33 (the Triangulum Galaxy) and the detailed features of its old stellar population. The study of these details is vital for our understanding of galaxy formation and evolution. We search for two types of components within the old stellar population: globular star clusters and the faint, diffuse stellar halo. We find only one new unambiguous outer halo star cluster, in addition to the five previously known in the M33 outer halo (r=10-50 kpc). A further 2440 cluster candidates are identified, which we analyse using two different types of simulated clusters. We are able to describe the type of clusters that are likely to remain hidden from our searches. Our study of a population of red giant branch (RGB) stars far from the M33 disk reveals a low-luminosity, centrally concentrated component which we interpret as the discovery of M33’s halo. It is everywhere in our data fainter than mu_V ~ 33 mag arcsec^−2, with scale length r_exp ~ 20 kpc, an overall luminosity not more than a few percent of the total luminosity of M33, and is possibly also not azimuthally symmetric. For M33 to have so few outer halo clusters compared to M31 and to have such a low-luminosity halo, with the possible asymmetry that we see, suggests tidal stripping of M33’s halo components by M31 - a view that is also favoured by the morphology of the disk substructure and recent modelling.</p> / Doctor of Philosophy (PhD)

Bell's inequalities impose an upper limit on correlations between measurements of two-photon states under the assumption that the photons play by a set of local rules rather than by quantum mechanics. Quantum theory and decades of experiments both violate this limit. Recent theoretical work in quantum foundations has demonstrated that a local realist model can explain the non-local correlations observed in experimental tests of Bell's inequality if the underlying probability distribution of the local hidden variable depends on the choice of measurement basis, or ``setting choice''. By using setting choices determined by astrophysical events in the distant past, it is possible to asymptotically guarantee that the setting choice is independent of local hidden variables which come into play around the time of the experiment, closing this ``freedom-of-choice'' loophole. Here, I report on a novel experimental test of Bell's inequality which addresses the freedom-of-choice assumption more conclusively than any other experiment to date. In this first experiment in Vienna, custom astronomical instrumentation allowed setting choices to be determined by photon emission events occurring six hundred years ago at Milky Way stars. For this experiment, I selected the stars used to maximize the extent over which any hidden influence needed to be coordinated. In addition, I characterized the group's custom instrumentation, allowing us to conclude a violation of local realism by $7$ and $11$ standard deviations. These results are published in Handsteiner et. al. (\textit{Phys. Rev. Lett.} 118:060401, 2017). I also describe my design, construction, and experimental characterization of a next-generation ``astronomical random number generator'', with improved capabilities and design choices that result in an improvement on the original instrumentation by an order of magnitude. Through the 1-meter telescope at the NASA/JPL Table Mountain Observatory, I observed and generated random bits from thirteen quasars with redshifts ranging from $z = 0.1-3.9$. With physical and information-theoretic analyses, I quantify the fraction of the generated bits which are predictable by a local realist mechanism, and identify two pairs of quasars suitable for use as extragalactic sources of randomness in the next cosmic Bell test. I also propose two additional applications of such a device. The first is an experimental realization of a delayed-choice quantum eraser experiment, enabling a foundational test of wave-particle complementarity. The second is a test of the Weak Equivalence Principle, using our instrument's sub-nanosecond time resolution to observe the Crab pulsar at optical and near-infrared wavelengths. Using my data from the Crab Pulsar, I report a bound on violations of Einstein's Weak Equivalence Principle complementary to recent results in the literature. Most of these results appear in Leung et. al. (arXiv:1706.02276, submitted to \textit{Physical Review X}).

Radio-loud active galactic nuclei (AGN) are one class of objects associated with accretion activity onto supermassive black holes in centers of massive galaxies. They are believed to be in a radiatively-inefficient accretion mode with low accretion rate. To understand this accretion mode, it is important to measure its radiative output at high energies (> 13.6eV), which can be traced through optical emission lines. However, little is known about their true radiative output. This is because no correlation between optical emission-line and radio luminosity has been found for the majority of low-luminosity radio AGN, which are often classified as low-excitation radio galaxies, or Fanaroff-Riley Class I (FR-I) radio galaxies. We demonstrate that most of the line emission found in these galaxies is not powered by the central AGN, but likely powered by some old stellar population. Only when this component is subtracted or otherwise taken into account can we estimate the true line emission associated with the AGN. These emissions may show interesting correlations with the radio luminosities in some cases.

A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated galaxies have ignored the cosmological spin of halos. The goal of my thesis is to analyze the J-redistribution in barred galaxies embedded in spinning DM halos, and quantify the DM response. Using high-resolution N-body stellar and DM numerical simulations, I model and analyze the dynamical and secular evolution of stellar bars in disk galaxies and their DM counterparts —induced DM bars in spinning halos with a range of cosmological spin parameter λ ~ 0-0.09. Using a novel method to create initial conditions for the self-consistent equilibrium disk-halo systems, and evolving them for 10 Gyr, I follow the basic parameters of stellar and DM bars, including their observational corollaries. My conclusions are based on nonlinear orbit analysis which quantifies the orbit trapping by the resonances. My main results emphasize a new effect: the DM halo spin has a profound effect on the evolution of stellar and DM bars. Specifically, with increasing λ in the prograde direction: (1) stellar bars develop faster dynamically, but (2) experience a reduced growth during the secular phase of evolution, and basically dissolve for λ > 0.06. These disks can represent the unbarred branch of galaxies on the Hubble Fork Diagram; (3) the stellar bar pattern speeds level off and lose less J; and (4) the stellar bars exhibit ratios of corotation-to-bar radii, RCR/Rbar > 2, representing the so-called slow bars without offset dust lanes. Furthermore, I find that (5) the induced DM bars reach maximal amplitudes which strongly depend on λ, while those of the stellar bars do not; (6) efficiency of resonance trapping of DM orbits by the DM bars, their masses and volumes — all increase with λ; (7) contribution of resonant transfer of J to the DM halo increases with λ as well. (8) prograde and retrograde DM orbits play different roles in J-transfer. (9) Finally, I find that dependence of DM response on λ has important implications for a direct detection of DM and of the associated stellar tracers, such as 'streamers.' Additional results relate the above analysis of corotating disks and halos with those of the counter-rotating ones.