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Skillman, Samuel W.

Publications and source records attributed to Skillman, Samuel W..

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

The concentration dependence of the galaxy–halo connection: Modeling assembly bias with abundance matching

Empirical methods for connecting galaxies to their dark matter halos have become essential for interpreting measurements of the spatial statistics of galaxies. In this work, we present a novel approach for parameterizing the degree of concentration dependence in the abundance matching method. Furthermore, this new parameterization provides a smooth interpolation between two commonly used matching proxies: the peak halo mass and the peak halo maximal circular velocity. This parameterization controls the amount of dependence of galaxy luminosity on halo concentration at a fixed halo mass. Effectively this interpolation scheme enables abundance matching models to have adjustable assembly bias in the resulting galaxy catalogs. With the new $400\,\mathrm{Mpc}\,{h}^{-1}$ DarkSky Simulation, whose larger volume provides lower sample variance, we further show that low-redshift two-point clustering and satellite fraction measurements from SDSS can already provide a joint constraint on this concentration dependence and the scatter within the abundance matching framework.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

How much can we learn from a merging cold front cluster? Insights from X-ray temperature and radio maps of A3667

The galaxy cluster A3667 is an ideal laboratory to study the plasma processes in the intracluster medium. High-resolution Chandra X-ray observations show a cold front in A3667. At radio wavelengths, A3667 reveals a double radio-relic feature in the outskirts of the cluster. These suggest multiple merger events in this cluster. In this paper, we analyze the substantial archival X-ray observations of A3667 from the Chandra X-ray Observatory and compare these with existing radio observations as well as state-of-the-art adaptive mesh refinement MHD cosmological simulations using Enzo. We have used two temperature map making techniques, weighted Voronoi tessellation and adaptive circular binning, to produce the high-resolution and largest field-of-view temperature maps of A3667. These high-fidelity temperature maps allow us to study the X-ray shocks in the cluster using a new two-dimensional shock-finding algorithm. We have also estimated the Mach numbers from the shocks inferred from previous ATCA radio observations. The combined shock statistics from the X-ray and radio data are in agreement with the shock statistics in a simulated MHD cluster. We have also studied the profiles of the thermodynamic properties across the cold front using ∼447 ks from the combined Chandra observations on A3667. Our results show that the stability of the cold front in A3667 can be attributed to the suppression of the thermal conduction across the cold front by a factor of ∼100-700 compared to the classical Spitzer value.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Building a Community-Focused Data Platform

The National Data Service (NDS) presents a broad-reaching vision of integrating discovery, publishing, and sharing of data. Metcalfe's Law states that the value of a network increases with the number of connections in the network, not the number of nodes. The NDS must develop and steward connections not only between data, as is in its vision statement, but between individuals as well. We propose that this be accomplished by explicitly developing it as a platform on which data exploration can be constructed by individual researchers.

97 MATHEMATICS AND COMPUTING↗