1609.00037
Good enough practices in scientific computing
Wilson, et al
Present a set of computing tools and techniques that every researcher can and should adopt. These recommendations synthesize inspiration from the authors' own work, from the experiences of the thousands of people who have taken part in Software Carpentry and Data Carpenetry workshops over the past six years, and from a variety of other guides. The recommendations are aimed specifically at people who are new to research computing.
1610.06566
On the origin and evolution of the galaxy stellar mass function
Kelson, Benson, Abramson
Explore the evolution of galaxy ensembles at early times by working the in situ stellar mass growth of galaxies purely as a stationary stochastic (e.g., quasi-steady state) process. By combining the mathematics of such processes with Newtonian gravity and a mean local star formation efficiency, show that the stellar mass evolution of galaxy ensembles is directly related to the average acceleration of baryons onto dark matter haloes at the onset of star formation, which explicit dependencies on the initial local matter densities and halo mass. The density term specifically implies more rapid average rates of growth in higher density regions of the universe compared to low density regions, i.e., assembly bias. With this framework, using standard cosmo parameters, a mean star formation efficiency derived by other authors, and knowledge of the shape of the cosmo matter power spectrum at small scales, analytically derive (1) the characteristic stellar masses of galaxies (M*), (2) the power-law low-mass slope (alpha) and normalization (phi*) of the stellar mass function, and (3) the evolution of the stellar mass function in time over 12.5>z>2. Correspondingly, the rise in the cosmic SFR density over these epochs, while the universe can sustain unabated fueling of star formation, also emerges naturally, All of the findings are consistent with the deepest available data, including the expectation of alpha~-7/5; i.e., a stellar mass function low-mass slope that is notably shallower than that of the halo mass function, and with no systematic deviations from a mean star formation efficiency with density or mass, nor any explicit, additional feedback mechanisms. These derivations yield a compelling richness and complexity but also show that very few astrophysical details are required to understand the evolution of cosmic ensemble of galaxies at early times.
1610.06673
Probabilistic cosmological mass mapping from weak lensing shear
Schneider, Ng, Dawson, Marshall, Meyers, Bard
Infer gravitational lensing shear and convergence fields from galaxy ellipticity catalogs under a spatial process prior for the lensing potential. Demonstrate the performance of the algorithm with simulated Gaussian-distributed cosmo lensing shear maps and a reconstruction of the mass distribution of the merging galaxy cluster A781 using galaxy ellipticities measured with the DLS. Given interim posterior samples of lensings shear or convergence fields on the sky, describe an algorithm to infer cosmo parameters via lens field marginalization. In the most general formulation of the algorithm, make no assumptions about weak shear or Gaussian distributed shape noise or shears. Because it requires solutions and matrix determinate of a linear system of dimension that scales with the number of galaxies, expect the algorithm to require parallel high-performance computing resources for application to ongoing wide field lensing surveys.
1610.06890
Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification data
Melchior, Gruen, et al
Use WL shear measurements to determine the mean mass of optically selected galaxy clusters in DES SV data. In a blinded analysis, split the sample of more than 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5<=lambda<=180 and redshifts 0.2<=z<=0.8, and fit the averaged mass density contrast profiles with a model that accounts for 7 distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentering; deviations from the NFW halo profile; halo triaxiality; and line-of-sight projections. Combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, M(lambda,z)~M0 lambda^F (1+z)^G. Find M0==<M_200m | lambda=30,z=0.5> = [2.35±0.22(stat)±0.12(sys)] x 1e14 Msun, with F=1.12±0.20(stat)±0.06(sys) and G-0.18±0.75(stat)±0.24(sys). The amplitude of the mass-richness relation is in excellent agreement with the WL calibration of redMapPer clusters in SDSS by Simet+2016 and with the Saro+2015 calibration based on abundance matching of SPT-deteted clusters. The results extend the z range over which the mass-richness relation of redMaPPer clusters has been calibrated with WL from z<=0.3 to z<=0.8. Calibration uncertainties of shear measurements and photometric z estimates dominate the systematic error budget and require substantial improvements for forthcoming studies.
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