Studies of central black holes (BHs) in nearby galaxies revealed tight correlation between the BH mass the host galaxy bulge mass, indicating a link between BH and star formation (SF) in the host galaxy. Luminous active galactic nuclei (AGN) are powered by mass accretion onto supermassive BHs. Observations of the AGNs and the SF in their host galaxies are required to understand their relation and how they establish this BH mass-galaxy bulge mass correlation over a wide range of cosmic lookback times. This thesis presents a survey of 24 μm-selected luminous AGN and their host galaxies up to z ~ 3.2. It focuses on the foreground and background broad line (Type-1) and narrow line (Type-2) AGNs of 30 massive galaxy cluster fields with total survey area of 5.2 deg², using the multi-wavelength dataset from the ultraviolet (UV) to far infrared (FIR) from the Local Cluster Substructure Survey. The AGN sample is nearly complete to a 1 mJy flux cutoff at 24 μm, and is optical-spectroscopically identified. With this dataset and the accompanying MMT/Hectospec spectroscopy survey, the properties of AGNs such as BH masses, BH accretion rates, and total luminosities, can be readily determined. Particularly, the Herschel data (100, 160, 250, 350, and 500 μm) sample the FIR peak of sources in our sample, and provide constraints on the star formation rates (SFR) in the host galaxies. For the Type 1 AGN sample, most of the systems are at z > 0.6 with luminosities > 10^45 ergs/s. Out of the 205 Type-1 AGNs, 107 are detected in at least two Herschel bands. We use AGN, stellar, and SF galaxy templates to decompose their spectral energy distributions (SEDs) from the UV to the FIR, and estimate their IR SF luminosities, AGN luminosities, and their host galaxy stellar masses. The SED decomposition reveals that a high level of SF is ubiquitous for our 24 μm-selected Type-1 AGN sample. For sources at z < 1, the stellar components from SED decomposition provide direct constraints on the stellar mass. For sources at z > 1, the BH mass-bulge stellar mass correlation is used for indirect constraints on the stellar mass. We carried out a similar analysis on the 85 Type-2 AGNs and their host galaxies up to z ~ 0.8, out of which 55 are detected in at least two Herschel bands. We reach the same conclusion as for the Type 1 AGN sample. That is, 1) These AGN host galaxies are very massive, and the vast majority of these galaxies have specific star formation rates (SSFR) consistent with those of main-sequence, star-forming galaxies rather than starbursting galaxies; 2) Most of these AGNs accrete at a rate close to 10% of Eddington; 3) We also find a strong correlation between the IR luminosity of the SF component and the AGN total luminosity, for both Type 1 and Type 2 AGNs. However, we show that the correlation could arise just because the BH mass (and hence AGN total luminosity) and the SF are both correlated with the galaxy mass, rather than requiring a causal connection between the observed rates of SF and the nuclear activity.

This dissertation focuses on determining the properties of the environments and the line-of-sight mass distributions for a sample of strong gravitational lenses as well as establishing their effects on the observed lens properties and the Hubble constant.Strong gravitational lenses ought to be able to provide important constraints for cosmology, however the lack of understanding of their large--scale environments has hindered their use. Here, we present a spectroscopic survey of the environments and lines of sight of 28 strong galaxy--mass lenses. We determine redshifts for 9698 galaxies in the fields of these lenses and identify 163 structures with at least five members in 26 fields. We find that 12 of 26 lenses are group members. Six of these groups are newly discovered. Overall, between 38--67% of lenses are in groups, and in 8--31% of the lenses the group makes a significant contribution to the lens potential. Line-of-sight structures are present in virtually every lens field, and in 19% of lenses the structures appear to be a significant perturbation to the lens potential. We consider the effect of the environment on H0 derived from gravitational lenses. We find that, when the environment is ignored, lenses in groups predict a systematically higher value of H0, inconsistent at the 1 sigma level with H0 derived from isolated lenses. Correcting for the environment and line of sight structures brings the two values into agreement and lowers the combined value (H=66-3.2+3.4). Without correction for the environment, the H0 values from strong lenses should be considered a strict upper limit. We explore the correlation between the observed lens properties and external perturbations from the observational perspective. We find that four-image lenses are statistically more likely to be in groups than two-image lenses. Furthermore, the distributions of convergences are statistically different for quads and doubles. This finding strongly supports the idea that the high quad-to-double ratios are at least partially due to the effect of the environment. We also examine the connections between flux anomalies and environment and the correlations between image separations and convergence. We find no significant links due to the limitations of our sample.

Within the past decade, the CDM model has emerged as a standard paradigm of structure formation. While it has been very successful in explaining the structure of the Universe on large scales, on smaller (galactic) scales problems have surfaced. In this thesis, we investigate several of these problems in more detail. The thesis is organized as follows. In Chapter 1, we give a brief introduction about structure formation in the universe and discuss some of the problems being faced by the current CDM paradigm of galaxy formation.In Chapter 2, we analyze the angular momentum properties of virialized halos obtained from hydrodynamical simulations. We describe an analytical function that can be used to describe a wide variety of angular momentum distributions (AMDs), with just one parameter α. About $90-95% of halos turn out to haveα < 1.3, while exponential disks in cosmological halos would require 1.3 < α < 1.6. This implies that a typical halo in simulations has an excess of low angular momentum material as compared to that of observed exponential disks, a result which is consistent with the findings of earlier works.In Chapter 3, we perform controlled numerical experiments of merging galactic halos in order to shed light on the results obtained in cosmological simulations. We explore the properties of shape parameter α of AMDs and the spin ratio λGas/λDM in merger remnants and also their dependence on orbital parameters. We find that the shape parameter α is typically close to 1 for a wide range of orbital parameters, less than what is needed to form an exponential disk.The last chapter of the thesis (Chapter 4) is devoted to the analysis of phase space structure of dark matter halos. We first present a method to numerically estimate the densities of discretely sampled data based on a binary space partitioning tree. We implement an entropy-based node splitting criterion that results in a significant improvement in the estimation of densities compared to earlier work. We use this technique to analyze the phase space structure of halos.

The presence of massive objects is detectable in observations via the gravitational lensing effect on light from more distant sources. From this effect it is possible to reconstruct the masses of clusters, and the distribution of matter within the cluster. However, further theoretical work needs to be done to properly contextualize any proposed projects involving, for instance, SALT data sets. Observational lensing studies use one of two techniques to recover the lens mass distribution: parametric (model dependent) techniques; and, a more recent innovation, non-parametric methods. The latter deserves further study as a tool for cluster surveys. To this end, we provide a comprehensive analysis of existing non-parametric algorithms and software, as well as estimates on the likely errors to be expected when used as an astronomical tool. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2009.

In studies of triaxial elliptical galaxies, one of the least observationally studied phenomena is figure rotation. Figure rotation has important consequences for the orbital structure and could explain the survival of steep nuclear cusps. For this project, we thus wish to investigate the possibility of measuring the figure rotation of an elliptical galaxy for which the geometry is approximately known using the Tremaine-Weinberg (TW) method. Originally meant for measuring the pattern speed of barred disk galaxies, we test the validity of the method using NGC 5266, a minor-axis dust-lane elliptical. In the process, the galaxy's line-of-sight velocity distribution (LOSVD) is measured along several slit positions. Measurements of the velocity v, velocity dispersion a, skewness /J3, and kurtosis h^ are derived using the Fourier Correlation Quotient method and a Gauss-Hermite series. This work represents the most detailed stellar kinematic measurements of NGC 5266 to date and confirm that it is one of the fastest rotating elliptical galaxies known today (Varnas et al. 1987). We find a maximum velocity of about 167 km s_1 at both a PA of 274° and 304°. This is compared to a maximum of 212 ± 7kms~1 at a PA of 287° found elsewhere (Varnas et al. 1987). The TW method yields significantly different values for the pattern speed. These vary between -19 and 22kms Wcsec"1. The discrepancy between the results casts doubt on the ability to straightforwardly apply the TW method to elliptical systems, but the study provides some insight into how the method may be more successfully implemented in the future. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope programme that imaged 43 early-type galaxies in the Fornax cluster, using the ACS F475W (~g) and F850LP (~z) bandpasses. We use this data set, which spans a range of ~600 in blue luminosity down to M_B ~ -16 mag, to study and characterize the properties of central galactic nuclei by fitting ellipses to the galaxy isophotes and examining their 1-dimensional surface brightness profiles. To test the robustness of this method, we perform a similar analysis with 2-dimensional surface brightness profile fitting using GALFIT, and find acceptable agreement between the derived structural parameters from the two techniques. We determine 72% of our sample (31 galaxies) to be nucleated, a significant increase from 28% found in the ground-based study of Ferguson et al. (1989). This high frequency of nucleation suggests that the creation of a compact nuclear component is a common outcome in early-type galaxy formation. Only three of the nuclei (10%) are observed to be significantly offset (by > 0.5") from their host galaxy photocentres, and a trend of increasing offset in fainter galaxies is observed, which indicates that nucleus formation timescales and/or pathways may vary with host luminosity. The nuclei are found to be larger and approximately 50 times brighter than typical globular clusters from our Fornax sample, and to follow different half-light surface brightness versus magnitude scaling relations. The colours of the nuclei are characteristic of intermediate to old stellar populations, and those residing in galaxies with B_T > 13 mag are observed to correlate with the nucleus luminosities. Both nucleus and galaxy colours become redder with increasing host luminosity, although the trend with the nuclei is steeper, and the nuclei in the brightest galaxies are found to be redder than their hosts. However, the majority of nuclei are bluer than their hosts, having an average colour difference of 0.27 +/- 0.25 mag. Comparison of our results to the complementary ACS Virgo Cluster Survey (ACSVCS) study of nuclei Côté et al. (2006), which examined 100 early-type galaxies in the Virgo cluster, yields strikingly similar results. Both samples show similar frequency of nucleation (68% in the ACSVCS), a constant nucleus-to-galaxy luminosity ratio (with a mean value of 0.41% +/- 0.04% derived from the combined samples), as well as excellent agreement in the nucleus luminosity functions and sizes (with median values of 6 pc in g and 7 pc in z in both studies). Since the Fornax cluster presents a much denser environment than Virgo, such consistency between the properties of the nuclei indicates that their formation and evolution may be influenced by local factors more than environmental ones. In particular, a constant nucleus-to-galaxy luminosity ratio suggests that a host galaxy's luminosity (or, more likely, mass) may be a key element in determining the properties of its nucleus. Since simulations have found the two main theorized nucleus formation pathways to be effective on different mass scales (with dissipationless infall of star clusters being more efficient in lower-mass galaxies, and in-situ gas accretion in higher-mass hosts), we propose that both processes may both in fact be responsible for nucleus formation, but varying in relative importance along the galaxy luminosity function. / Graduate

In this thesis, several theoretical concepts relating to the large-scale structure of the universe are presented. In particular, various aspects of the hierarchical scenario are investigated. The initial perturbation field and its early evolution are discussed in Chapter 3. Chapter 4 is concerned with two-point correlation functions for galaxies, clusters and super-clusters. In Chapter 5, some effects of using velocity as a distance measure are examined. In particular, it will be argued that caustics in redshift space are an almost inevitable feature of the hierarchical scenario. Chapter 6 concentrates on the possibity that quasar Ly-α absorption lines are redshift caustics.

We quantify the structure and scale of the Universe using redshift surveys of galaxies and QSOs and observations of Galactic open star clusters. We obtain the galaxy power spectrum from the Durham/UKST Galaxy Redshift Survey. By comparing the shape of the observed power spectrum to the APM real space power spectrum, we quantify the size of the redshift space distortions and find β = Ω(^0.6)/b=0.60±0.35. We also apply counts-in-cells analysis to the Durham/UKST and Stromlo-APM Surveys and measure the skewness directly out to 20h(^-1)Mpc. We find that the skewness measured from CDM models can only be reconciled with that of galaxies if bias is non-linear. We make predictions for the clustering in the 2dF QSO Survey by constructing mock catalogues from the Hubble Volume N-body simulation, with geometry, selection function and clustering matching those expected in the completed Survey. We predict that the correlation function will be reliably measured out to ~ 1, 000h(^-1)Mpc and the power spectrum out to 500h(^-1)Mpc. We measure the power spectrum from the 2dF QSOs observed by January 2000 and find it has a shape of F ~ 0.1. We also find little evolution in the clustering amplitude as a function of redshift. We obtain constraints on the cosmo- logical parameters Ωn and β by combining results from modeling geometric distortions introduced into the clustering pattern due to inconsistent cosmological assumptions and results from the QSO-mass bias. Finally, we consider the scale of the Universe. We check the calibration of the Cepheid Period-Luminosity relation using U,B,V and K'band imaging of Galactic Open Clusters containing Cepheids and measure the distance modulus to the LMC to be 18.51 ±0.10. However, we find anomalous colour-colour diagrams for two clusters and suggest that the effects of metallicity may be greater than previously considered.

This thesis investigates the dynamical evolution of systems orbiting within deeper potentials. Initially we use a simple satellite-halo interaction to study the dynamical processes that act on orbiting systems and we compare these results to analytical theory. Deep images of the Centaurus cluster reveal a spectacular arc of diffuse light that stretches for over 100 kpc and yet is just a few kpc wide. We use numerical simulations to show that this feature can be produced by the tidal debris of a spiral galaxy that has been disrupted by the potential of one of the central cD galaxies of the cluster. The evolution of sub-halos is then studied in a cosmological context using high resolution N-body simulations of galactic mass halos that form in a cold dark matter (CDM) simulation. CDM halos form via a complex series of mergers, accretion events and violent relaxation. Halos are non-spherical, have steep singular density profiles and contain many thousands of surviving dark matter substructure clumps. This will lead to several unique signatures for experiments that aim to detect dark matter either indirectly, through particle annihilation, or directly in a laboratory. For the first time it is possible to construct maps of the gamma-ray sky that result from the annihilation of dark matter particles within simulated dark matter halo distributions.

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