Narrow Results

The Milky Way is the product of a complex evolution of generations of mergers, collapse, star formation, supernova and collisional heating, radiative and collisional cooling, and ejected nucleosynthesis. Moreover, all of this occurs in the context of the cosmic expansion, the formation of cosmic filaments, dark matter halos, spiral density waves, and emerging dark energy. In this review we summarize observational evidence and discuss recent calculations concerning the formation, evolution nucleosynthesis in the galaxies of the Local Group (LG). In particular, we will briefly summarize observations and simulations for the dwarf galaxies and the two large spirals of the LG. We discuss how galactic halos form within the dark matter filaments that define a super-galactic plane. Gravitational interaction along this structure leads to streaming flows toward the two dominant galaxies in the cluster. These simulations and observations also suggest that a significant fraction of the Galactic halo formed as at large distances and then arrived later along these streaming flows. We also consider the insight provided by observations and simulations of nucleosynthesis both within the galactic halo and dwarf galaxies in the LG.

In this contribution we review and discuss several aspects of Cosmic Voids. Voids are a major component of the large scale distribution of matter and galaxies in the Universe. Their instrumental importance for understanding the emergence of the Cosmic Web is clear. Their relatively simple shape and structure makes them into useful tools for extracting the value of a variety cosmic parameters, possibly including even that of the influence of dark energy. Perhaps most promising and challenging is the issue of the galaxies found within their realm. Not only does the pristine environment of voids provide a promising testing ground for assessing the role of environment on the formation and evolution of galaxies, the dearth of dwarf galaxies may even represent a serious challenge to the standard view of cosmic structure formation.

Properties of host galaxies of gamma-ray bursts (GRBs) are investigated, using N-body/Eulerian hydrodynamic simulations and the stellar population synthesis model, Starburst99, to infer observable properties. The simulations include gravitation, hydrodynamical shocks, and radiative cooling, as well as a phenomenological description of galaxy formation. We first focus on the overall population at intermediate redshifts and emphasize the strong relationships between the specific star formation rate (SFR) and the epoch of formation, color index and mass-to-light ratio, quantities known to reflect the star formation history of galaxies. The faintest and bluest galaxies are objects with the highest specific rates. Faint and blue colors are common properties among the population of GRB host galaxies. We then consider a well-defined sample of observed GRB host galaxies with optical estimates of SFR and SFR-to-luminosity ratios and look for their numerical counterparts by selecting objects that have both values nearest to those of the observed host galaxies. Comparing the numerical counterparts to the overall simulated galaxy population at different redshifts suggests that GRB host galaxies are a particular sub-population of galaxies, likely to be drawn from the high specific SFR population, rather than the high SFR galaxy population. In a separate, preliminary study, we address the link between the cosmological evolution of galaxy properties and the properties of the gas surrounding galaxies by tracing the history of galaxies through their main progenitors. We show that high specific SFRs tend to occur in the early evolutionary stages of galaxies. GRB host galaxies may thus be a powerful way to select those proto-galaxies and contribute to our understanding of galaxy evolution.