Day 616

Friday.

1403.6827
Statistics of dark matter substructure: I. model and universal fitting functions
Jiang, van den Bosch

Present a SAM describing the evolution of DM sub haloes.  The model uses merger trees constructed using the method of Parkinson+2008 to describe the masses and redshifts of sub haloes at accretion, which are subsequently evolved using a simple model for the orbit-averaged mass loss rates.  The model is extremely fast, treats sub haloes of all orders, accounts for scatter in orbital properties and halo concentrations, and uses a simple recipe to convert sub halo mass to maximum circular velocity.  The model accurately reproduces the average sub halo mass in excess of 80% of its infall mass during its first radial orbit within the host halo.  Demonstrate that the total mass fraction in sub haloes is tightly correlated with the 'dynamical age' of the host halo, defined as the number of halo dynamical times that have elapsed since its formation.  Using this relation, present universal fitting functions for the evolved and involved sub halo mass and velocity functions that are valid for any host halo mass, at any redshift, and for any LCDM cosmology.

1403.6828
The effects of varying cosmological parameters on halo substructure
Dooley et al

Investigate how different cosmo params (e.g. WMAP and Planck) affect the nature and evolution of Dm halo substructure.  Use a series of flat LCDM cosmo N-body sims of structure formation, each with a different PS but the same initial white noise field.  Fiducial sim is based on WMAP7 cosmology.  Systematically vary the spectral index, matter density, and sigma8 for 7 unique sims.  Across these, study variations in the sub halo mass function, mass fraction, maximum circular velocity function, spatial distribution, concentration, formation times, accretion times, and peak mass.  Eliminate dependence of sub halo properties on host halo mass and average over many hosts to reduce variance.  While the "same" sub haloes from identical initial overdensity peaks in higher sigma8, ns, and Omega_m simulations accrete earlier and end up less massive and closer to the halo center at z=0, the process of continuous sub halo accretion and destruction leads to a steady state distribution of these properties across all sub haloes in a given host.  This steady state mechanism eliminates cosmological dependence on all properties listed above except sub halo concentration and V_max, which remain greater for higher sigma8, n_s and Omega_m sims, and sub halo formation time, which remains earlier.  Also find that the numerical technique for computing scale radius and the halo finder used can significantly affect the concentration-mass relationship computed for a simulation.

1403.7186
The Blanco cosmology survey: an optically-selected galaxy cluster catalog and a public release of optical data products
Bleem, … Busha, Gladders, High, Rest, Wechsler et al

The Blanco cosmology survey is a griz-band optical-imaging survey that covers 80 sq deg of the southern sky.  The survey consists of two fields roughly centered at ra,dec = 23h,-55d and 5h30m,-53d with imaging designed to reach depths sufficient for the detection of L* galaxies out to a redshift of one.  In this paper, describe the reduction of the survey data, the creation of calibrated source catalogs and a new method for the separation of stars and galaxies.  Search these catalogs for galaxy clusters at z<0.75 by identifying spatial over-densities of red-sequence galaxies.  Report the coordinates, redshift, and optical richness, Lambda, for 764 detected galaxy clusters at z<0.75.  This sample, >85% of which are new discoveries, has a median redshift of 0.52 and median richness Lambda(0.4L*) of 16.4.  Accompanying this paper, also release data products including the reduced images and calibrated source catalogs.  These products available over the web.