We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum lambda(Re) and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3 degrees (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between lambda(Re) and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

We model the dynamics of dwarf early-type galaxies in the Virgo cluster when subject to a variety of environmental processes. We focus on how these processes imprint trends in the dynamical state (rotational versus pressure support as measured by the lambda(Re/2)* statistic) with projected distance from the cluster center, and compare these results to observational estimates. We find a large scatter in the gradient of lambda(Re/2)* with projected radius. A statistical analysis shows that models with no environmental effects produce gradients as steep as those observed in none of the 100 cluster realizations we consider, while in a model incorporating tidal stirring by the cluster potential 34% of realizations produce gradients as steep as that observed. Our results suggest that tidal stirring may be the cause of the observed radial dependence of dwarf early-type dynamics in galaxy clusters.

We present a simulation setup for studying the dynamical and chemical evolution of the intracluster medium (ICM) and analyze a sample of 12 galaxy clusters that are diverse both kinetically (pre-merger, merging, virialized) and in total mass (M-vir = 1.17 x 10(14) - 1.06 x 10(15) M-circle dot). We analyzed the metal mass fraction in the ICM as a function of redshift and discuss radial trends as well as projected 2D metallicity maps. The setup combines high mass resolution N-body simulations with the semi-analytical galaxy formation model GALACTICUS for consistent treatment of the subgrid physics (such as galactic winds and ram-pressure stripping) in the cosmological hydrodynamical simulations. The interface between GALACTICUS and the hydro simulation of the ICM with FLASH is discussed with respect to observations of star formation rate histories, radial star formation trends in galaxy clusters, and the metallicity at different redshifts. As a test for the robustness of the wind model, we compare three prescriptions from different approaches. For the wind model directly taken from GALACTICUS, we find mean ICM metallicities between 0.2-0.8 Z(circle dot) within the inner 1 Mpc at z = 0. The main contribution to the metal mass fraction comes from galactic winds. The outflows are efficiently mixed in the ICM, leading to a steady homogenization of metallicities until ram-pressure stripping becomes effective at low redshifts. We find a very peculiar and yet common drop in metal mass fractions within the inner similar to 200 kpc of the cool cores, which is due to a combination of wind suppression by outer pressure within our model and a lack of mixing after the formation of these dense regions.

We present the results of a Keck-ESI study of dwarf galaxies across a range of environment: the Perseus Cluster, the Virgo Cluster, the NGC 1407 group, and the NGC 1023 group. 18 dwarf ellipticals (dEs) are targeted for spectroscopy, three for the first time. We confirm cluster membership for one Virgo dE, and group membership for one dE in the NGC 1023 group, and one dE in the NGC 1407 group for the first time. Regardless of environment, the dEs follow the same size-magnitude and sigma-luminosity relation. Two of the Virgo dwarfs, VCC 1199 and VCC 1627, have among the highest central velocity dispersions (sigma(0) = 58.4 and 49.2 km s(-1)) measured for dwarfs of their luminosity (M-R approximate to -17). Given their small sizes (R-e < 300 pc) and large central velocity dispersions, we classify these two dwarfs as compact ellipticals (cEs) rather than dEs. Group dEs typically have higher mean dynamical-to-stellar mass ratios than the cluster dEs, with M-dyn/M-star = 5.1 +/- 0.6 for the group dwarfs, versus M-dyn/M-star = 2.2 +/- 0.5 for the cluster sample, which includes two cEs. We also search for trends in M-dyn/M-star versus distance from M87 for the Virgo Cluster population, and find no preference for dwarfs with high values of M-dyn/M-star to reside in the cluster outskirts dyn centre.

Many properties of the Milky Way's (MW) dark matter halo, including its mass-assembly history, concentration, and subhalo population, remain poorly constrained. We explore the connection between these properties of the MW and its satellite galaxy population, especially the implication of the presence of the Magellanic Clouds for the properties of the MW halo. Using a suite of high-resolution N-body simulations of MW-mass halos with a fixed final M-vir similar to 10(12.1) M-circle dot, we find that the presence of Magellanic Cloud-like satellites strongly correlates with the assembly history, concentration, and subhalo population of the host halo, such that MW-mass systems with Magellanic Clouds have lower concentration, more rapid recent accretion, and more massive subhalos than typical halos of the same mass. Using a flexible semi-analytic galaxy formation model that is tuned to reproduce the stellar mass function of the classical dwarf galaxies of the MW with Markov-Chain Monte-Carlo, we show that adopting host halos with different mass-assembly histories and concentrations can lead to different best-fit models for galaxy-formation physics, especially for the strength of feedback. These biases arise because the presence of the Magellanic Clouds boosts the overall population of high-mass subhalos, thus requiring a different stellar-mass-tohalo-mass ratio to match the data. These biases also lead to significant differences in the mass-metallicity relation, the kinematics of low-mass satellites, the number counts of small satellites associated with the Magellanic Clouds, and the stellar mass of MW itself. Observations of these galaxy properties can thus provide useful constraints on the properties of the MW halo.

Dwarf galaxies are known to have remarkably low star formation efficiency due to strong feedback. Adopting the dwarf galaxies of the Milky Way (MW) as a laboratory, we explore a flexible semi-analytic galaxy formation model to understand how the feedback processes shape the satellite galaxies of the MW. Using Markov Chain Monte Carlo, we exhaustively search a large parameter space of the model and rigorously show that the general wisdom of strong outflows as the primary feedback mechanism cannot simultaneously explain the stellar mass function and the mass-metallicity relation of the MW satellites. An extended model that assumes that a fraction of baryons is prevented from collapsing into low-mass halos in the first place can be accurately constrained to simultaneously reproduce those observations. The inference suggests that two different physical mechanisms are needed to explain the two different data sets. In particular, moderate outflows with weak halo mass dependence are needed to explain the mass-metallicity relation, and prevention of baryons falling into shallow gravitational potentials of low-mass halos (e.g., "pre-heating") is needed to explain the low stellar mass fraction for a given subhalo mass.

Using a cosmological N-body simulation, we investigate the origin and distribution of stars in the intracluster light (ICL) of a Fornax-like cluster. In a dark-matter-only simulation, we identify a halo that, at z = 0, has M-200 similar or equal to 4.1 x 10(13)M(circle dot) and r(200) = 700 kpc, and replace infalling subhalos with models that include spheroid and disc components. As they fall into the cluster, the stars in some of these galaxies are stripped from their hosts, and form the ICL. We consider the separate contributions to the ICL from stars that originate in the haloes and the discs of the galaxies. We find that disc ICL stars are more centrally concentrated than halo ICL stars. The majority of the disc ICL stars are associated with one initially disc-dominated galaxy that falls to the centre of the cluster and is heavily disrupted, producing part of the cD galaxy. At radial distances greater than 200 kpc, well beyond the stellar envelope of the cD galaxy, stars formerly from the stellar haloes of galaxies dominate the ICL. Therefore at large distances, the ICL population is dominated by older stars.

The Galaxy Evolution Probe (GEP) is a concept for a mid and far-infrared space observatory designed to survey sky for star-forming galaxies from redshifts of z = 0 to beyond z = 4. Furthering our knowledge of galaxy formation requires uniform surveys of star-forming galaxies over a large range of redshifts and environments to accurately describe star formation, supermassive black hole growth, and interactions between these processes in galaxies. The GEP design includes a 2 m diameter SiC telescope actively cooled to 4 K and two instruments: (1) An imager to detect star-forming galaxies and measure their redshifts photometrically using emission features of polycyclic aromatic hydrocarbons. It will cover wavelengths from 10 to 400 mu m, with 23 spectral resolution R = 8 filter-defined bands from 10 to 95 mu m and five R = 3.5 bands from 95 to 400 mu m. (2) A 24 - 193 mu m, R = 200 dispersive spectrometer for redshift confirmation, identification of active galactic nuclei, and interstellar astrophysics using atomic fine-structure lines. The GEP will observe from a Sun-Earth L2 orbit, with a design lifetime of four years, devoted first to galaxy surveys with the imager and second to follow-up spectroscopy. The focal planes of the imager and the spectrometer will utilize KIDs, with the spectrometer comprised of four slit-coupled diffraction gratings feeding the KIDs. Cooling for the telescope, optics, and KID amplifiers will be provided by solar-powered cryocoolers, with a multi-stage adiabatic demagnetization refrigerator providing 100 mK cooling for the KIDs.

A key obstacle to developing a satisfying theory of galaxy evolution is the difficulty in extending analytic descriptions of early structure formation into full non-linearity, the regime in which galaxy growth occurs. Extant techniques, though powerful, are based on approximate numerical methods whose Monte Carlo-like nature hinders intuition building. Here, we develop a new solution to this problem and its empirical validation. We first derive closed-form analytic expectations for the evolution of fixed percentiles in the real-space cosmic density distribution, averaged over representative volumes observers can track cross sectionally. Using the Lagrangian forms of the fluid equations, we show that percentiles in delta - the density relative to the median - should grow as delta(t) proportional to delta(alpha)(0) t(beta), where alpha 2 and beta 2 for Newtonian gravity at epochs after the overdensities transitioned to non-linear growth. We then use 9.5 square degress of Carnegie-Spitzer-IMACS Redshift Survey data to map galaxy environmental densities over 0.2 < z < 1.5 (similar to 7 Gyr) and infer alpha = 1.98 +/- 0.04 and beta = 2.01 +/- 0.11 - consistent with our analytic prediction. These findings - enabled by swapping the Eulerian domain of most work on density growth for a Lagrangian approach to real-space volumetric averages - provide some of the strongest evidence that a lognormal distribution of early density fluctuations indeed decoupled from cosmic expansion to grow through gravitational accretion. They also comprise the first exact, analytic description of the non-linear growth of structure extensible to (arbitrarily) low redshift. We hope these results open the door to new modelling of, and insight-building into, galaxy growth and its diversity in cosmological contexts.

We present the first detections of the mean flux of the optical extragalactic background Light (EBL) at 3000, 5500, and 8000 Angstrom, derived from coordinated data sets taken at Las Campanas Observatory and with HST. In addition to detections in all three bands, we identify the minimum surface brightness contributed by resolved galaxies (23 < V < 28 AB mag) using a novel method of aperture photometry to which these data are uniquely suited. By comparing these results to the surface brightness from resolved galaxies measured using standard methods of galaxy photometry, we identify systematic errors in the results of faint galaxy photometry and place Limits on the EBL flux originating from undetected sources.