Day 1178

Friday.

1610.08525
Strong lensing signatures of luminous structure and stub structure in early-type galaxies
Gilman, et al

The arrival times, positions, and fluxes of multiple images in SL systems can be used to infer the presence of dark sub haloes in the deflector, and thus test predictions of CDM models.  However, gravitational lensing does not distinguish between perturbations to a smooth gravitational potential arising from baryonic and non-baryonic mass.  In this work, quantify the extent to which the stellar mass distribution of a deflector can reproduce flux ratio and astrometric anomalies typically associated with the presence of DM subhalo.  Using HST images of nearby galaxies, simulate SL systems with real distributions of stellar mass as they would be observed at z_d=0.5.  Add a DM halo and external shear to account for the smooth DM field, omitting dark substructure, and use a MC procedure to characterize the distributions of image positions, time delays, and flux ratios for a compact background source of diameter 5pc.  By convolving high-resolution images of real galaxies with a Gaussian PSF, simulate the most detailed smooth potential one could construct given high quality data, and find scatter in flux ratios of ~10%, which is interpreted as a typical deviation from a smooth potential caused by large and small scale structure in the lensing galaxy.  Demonstrate that the flux ratio anomalies arising from galaxy-scale baryonic structure can be minimized by selecting the most massive and round deflectors, and by simultaneously modeling flux ratio and astrometric data.


1610.08948
A galaxy-halo model for multiple cosmological tracers
Bull

The information extracted from large galaxy surveys with the likes of DES, DESI, Euclid, LSST, SKA, and WFIRST will be greatly enhanced if the resultant galaxy catalogues can be cross-correlated with one another.  Predicting the nature of the information gain, and developing the tools the realize it, depends on establishing a consistent model of how the galaxies detected by each survey trace the same underlying matter distribution. Existing analytic models, such as HOD modelling, are not well-suited for this task, and can suffer from ambiguities and tuning issues when applied to multiple tracers.  Construct a simple alternative that provides a common model for the connection between galaxies and DM haloes across a wide range of wavelengths (and thus tracer populations).  This is based on a change of parameterized statistical distributions that model the connection between (a) halo mass and bulk physical properties of galaxies, such as SFR; and (b) those same physical properties and a variety of emission processes.  The result is a flexible parametric model that allows analytic halo model calculations to be carried out for multiple tracers, as well as providing semi-realistic galaxy properties for fast mock catalogue generation.