Day 1121

Wednesday.

1607.03107
Predicting Quiescence: the dependence of specific star formation rate on galaxy size and central density at 0.5<z<2.5
Whitaker et al

Investigate the relationship between star formation and structure, using a mass-complete sample of 27k galaxies at 0.5<z<2.5 from 3D-HST.  Confirm that at fixed stellar mass, SF galaxies are larger than quiescent galaxies at all redshifts.  However, within the SF population, there is no relation between SFR and size: when dividing SF galaxies into quartiles based on their residual offsets in SFR, find that the sizes of galaxies in the highest quartile are 0.27±0.47 dex larger than galaxies in the lowest quartile, a difference that is not significant.  Also show that 50% of all SF in galaxies at fixed stellar mass takes place within a narrow range of sizes (0.26 dex).  Taken together, these results suggest that there is an abrupt cessation of SF after galaxies attain particular structural properties.  Confirming earlier results, find that the central stellar density within a fixed physical radius of 1 kpc is the key parameter connecting galaxy morphology and SFHs: galaxies with high central densities are red and have increasingly lower sSFRs, whereas galaxies with low central densities are blue and have a roughly constant (higher) sSFR at a given redshift interval.  Find remarkable little scatter in the average trends and a strong evolution in the central density (or equivalently central circular velocity) threshold correlated with quiescence.  This quenching threshold decreases by >0.5 dex from z~2 to z~0.7.  Neither a compact galaxy size nor a high n are sufficient to assess the likelihood of quiescence for the average galaxy; rather, it is the combination of these two parameters together with stellar mass that results in a unique quenching threshold in central density or velocity.


1607.03136
Variations of cosmic large-scale structure covariance matrices across parameter space
Reischke, Kiessling, Schäfer

The likelihood function for cosmo params, given by e.g. WL shear measurements, depends on contributions to the covariance induced by the nonlinear evolution of the cosmic web.  As nonlinear clustering to date has only been described by numerical N-body simulations in a reliable and sufficiently precise way, the necessary computational costs for estimating those covariances at different points in parameter space are tremendous.  In this work, describe the change of the matter covariance and of the WL covariance matrix as a function of cosmo parameters by construction a suitable basis, where the contribution to the covariance from NL structure formation using Eulerian perturbation theory at their order is modeled.  Show that the formalism is capable of dealing with large matrices and reproduces expected degeneracies and scaling with cosmo parameters in a reliable way.  Comparing the analytical results to numerical sims found that the method describes the variation of the covariance matrix found in the SUNGLASS WL sim pipeline within the errors at one-loop and tree-level for the spectrum and the trispectrum, respectively, for multipoles up to ell<=1300.  Show that it is possible to optimize the sampling of parameter space where numerical sims should be carried out by minimizing interpolation errors and propose a corresponding method to distribute points in parameter space in an economical way.


1607.03143 through 03155  (13 papers)
SDSS-III BOSS final set of papers