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We present results of a convergence study in which we compare the density profiles of CDM dark matter halos simulated with varying mass and force resolution. We show that although increasing the mass and force resolution allows one to probe deeper into the inner halo regions, the halo profiles converge at scales larger than the " effective " spatial(More)
We discuss how measurements of the absorption of gamma-rays from GeV to TeV energies via pair production on the extragalactic background light (EBL) can probe important issues in galaxy formation. Semi-analytic models (SAMs) of galaxy formation, based on the flat LCDM hierarchical structure formation scenario, are used to make predictions of the EBL from(More)
The violent hierarchical nature of the Λ-Cold Dark Matter cosmology poses serious difficulties for the formation of disk galaxies. To help resolve these issues, we describe a new, merger-driven scenario for the cosmological formation of disk galaxies at high redshifts that supplements the standard model based on dissipational collapse. In this picture,(More)
We use the rotation curves of a sample of dark matter dominated dwarf and low-surface brightness (LSB) late-type galaxies to study their radial mass distributions. We find that the shape of the rotation curves is remarkably similar for all (both dwarf and LSB) galaxies in the sample, suggesting a self-similar density distribution of their dark matter (DM)(More)
  • Philip J Humphrey, David A Buote, Fabio Gastaldello, Luca Zappacosta, James S Bullock, Fabrizio Brighenti +1 other
  • 2006
We present a Chandra study of mass profiles in 7 elliptical galaxies, of which 3 have galaxy-scale and 4 group-scale halos. These represent the best available data for nearby objects with comparable X-ray luminosities. We measure ∼flat mass-to-light (M/L) profiles within an optical half-light radius (R eff), rising by an order of magnitude at ∼10R eff ,(More)
We study the formation of fifty-three galaxy cluster-size dark matter halos (M = 10 14.0−14.76 M ⊙) formed within a pair of cosmological ΛCDM N-body simulations, and track the accretion histories of cluster subhalos with masses large enough to host ∼ 0.1L * galaxies. By associating subhalos with cluster galaxies, we find the majority of galaxies in clusters(More)
One of the main challenges facing standard hierarchical structure formation models is that the predicted abundance of galactic subhalos with circular velocities v c ∼ 10−30 km s −1 is an order of magnitude higher than the number of satellites actually observed within the Local Group. Using a simple model for the formation and evolution of dark halos, based(More)
We make predictions for diffuse stellar mass fractions in dark matter halos from the scales of small spiral galaxies to those of large galaxy clusters. We use an extensively-tested analytic model for subhalo infall and evolution and empirical constraints from galaxy survey data to set the stellar mass in each accreted subhalo to model diffuse light. We add(More)
Numerical simulations of Milky-Way size Cold Dark Matter (CDM) halos predict a steeply rising mass function of small dark matter subhalos and a substructure count that greatly outnumbers the observed satellites of the Milky Way. Several proposed explanations exist, but detailed comparison between theory and observation in terms of the maximum circular(More)
We present a series of high-resolution cosmological zoom-in simulations 1 of galaxy formation to z = 0, spanning halo masses M halo ∼ 10 8 − 10 13 M and stellar masses M * ∼ 10 4 − 10 11 M. Our simulations include a fully explicit treatment of both the multi-phase ISM (molecular through hot) and stellar feedback. The stellar feedback inputs (energy,(More)