If a subset of advanced civilizations in the universe choose to rapidly expand into unoccupied space, these civilizations would have the opportunity to grow to a cosmological scale over the course of billions of years. If such life also makes observable changes to the galaxies they inhabit, then it is possible that vast domains of life-saturated galaxies could be visible from the Earth. Here, w...

Ghostly Stellar Halos in Dwarf Galaxies Hoyoung Kang Department of Physics, University of Maryland Our study aims at probing the typical masses of the smallest and faintest galaxies that have ever formed in the universe. We carry out numerical simulations to characterize the size, stellar mass, and stellar mass surface density of stellar halos as a function of dark matter halo mass and a parame...

Tree-SPH, numerical simulations of disk galaxy formation in a cosmological context are presented. For the " passive " variant of such simulations, i.e. simulations not including the effects of stellar feedback processes, it is found that the resulting disk " galaxies " are far too small and specific angular momentum deficient, by about a factor of 8 in size and about a factor of 20 in specific ...

We investigated the color and morphology of optically selected galaxies in the region of clusters at z ∼ 1.2 near to the radio galaxy 3C 324 using archived data taken with the Hubble Space Telescope. The faint galaxies selected at the HST F702W band that contribute to the surface-density excess of the region have wide ranges of color, size, and morphology, which are not likely to be due to cont...

We measure the sizes of 82 massive (M ≥ 10M⊙) galaxies at 1.7 ≤ z ≤ 3 utilizing deep HST NICMOS data taken in the GOODS North and South fields. Our sample is almost an order of magnitude larger than previous studies at these redshifts, providing the first statistical study of massive galaxy sizes at z > 2, confirming the extreme compactness of these galaxies. We split our sample into disk-like ...

The size distributions of 2D and 3D Voronoi cells and of cells of Vp(2, 3),—2D cut of 3D Voronoi diagram—are explored, with the singleparameter (re-scaled) gamma distribution playing a central role in the analytical fitting. Observational evidence for a cellular universe is briefly reviewed. A simulated Vp(2, 3) map with galaxies lying on the cell boundaries is constructed to compare, as regard...

We present new high spatial resolution Kuiper Airborne Observatory (KAO) 50 μm and/or 100 μm data for 11 infrared-bright galaxies. The sizes of the central far-infrared emitting regions in three of these galaxies, NGC 660, NGC 891, and M 83, agree with those of the central star formation complexes. The Sb galaxy NGC 7331, which does not have observed star formation in its bulge, has a flat-topp...

We compare the properties of local spiral galaxies with the predictions of the Cole et al. semi-analytic model of hierarchical galaxy formation, in order to gain insight into the baryonic processes, such as gas cooling and star formation, that were responsible for shaping these galaxies. On the whole, the models reproduce the properties of presentday spirals rather well, including the trend in ...

We investigate the relation between the projected morphology and the velocity dispersion of groups of galaxies using two recently compiled group catalogs, one based on the 2MASS redshift survey (Crook et al. 2007) and the other on the SDSS Data Release 5 galaxy catalog (Tago et al. 2008). We analyse a suitable subsample of groups from each catalog selected such that it minimizes possible system...