Simon Birrer

A simple model linking galaxy and dark matter evolution

We construct a simple phenomenological model for the evolving galaxy population by incorporating pre-defined baryonic prescriptions into a dark matter hierarchical merger tree. Specifically the model is based on the simple gas-regulator model introduced by Lilly et al. 2013 coupled with the empirical quenching rules of Peng et al. 2010/12. The simplest model already does quite well in reproducing, without re-adjusting the input parameters, many observables including the Main Sequence sSFR-mass relation, the faint end slope of the galaxy mass function and the shape of the star-forming and passive mass functions. Compared with observations and/or the recent phenomenological model of Behroozi et al. 2013 based on epoch-dependent abundance-matching, our model also qualitatively reproduces the evolution of the Main Sequence sSFR(z) and SFRD(z) star formation rate density relations, the

The mass-sheet degeneracy and time-delay cosmography: analysis of the strong lens RXJ1131-1231

M_s - M_h

GRAVITATIONAL LENS MODELING WITH BASIS SETS

stellar-to-halo mass relation and also the

Lensing substructure quantification in RXJ1131-1231: a 2 keV lower bound on dark matter thermal relic mass

SFR - M_h

Models of the strongly lensed quasar DES J0408-5354

relation. Quantitatively the evolution of sSFR(z) and SFRD(z) is not steep enough, the

Probing the nature of dark matter by forward modelling flux ratios in strong gravitational lenses

M_s - M_h

Line-of-sight effects in strong lensing: putting theory into practice

relation is not quite peaked enough and, surprisingly, the ratio of quenched to star-forming galaxies around M* is not quite high enough. We show that these deficiencies can simultaneously be solved by ad hoc allowing galaxies to re-ingest some of the gas previously expelled in winds, provided that this is done in a mass-dependent and epoch-dependent way. These allow the model galaxies to reduce an inherent tendency to saturate their star-formation efficiency. This emphasizes how efficient galaxies around M* are in converting baryons into stars and highlights the fact that quenching occurs just at the point when galaxies are rapidly approaching the maximum possible efficiency of converting baryons into stars.

Cosmic Shear with Einstein Rings

We present extended modelling of the strong lens system RXJ1131-1231 with archival data in two HST bands in combination with existing line-of-sight contribution and velocity dispersion estimates. Our focus is on source size and its influence on time-delay cosmography. We therefore examine the impact of mass-sheet degeneracy and especially the degeneracy pointed out by Schneider & Sluse (2013) [1] using the source reconstruction scale. We also extend on previous work by further exploring the effects of priors on the kinematics of the lens and the external convergence in the environment of the lensing system. Our results coming from RXJ1131-1231 are given in a simple analytic form so that they can be easily combined with constraints coming from other cosmological probes. We find that the choice of priors on lens model parameters and source size are subdominant for the statistical errors for H0 measurements of this systems. The choice of prior for the source is sub-dominant at present (2% uncertainty on H0) but may be relevant for future studies. More importantly, we find that the priors on the kinematic anisotropy of the lens galaxy have a significant impact on our cosmological inference. When incorporating all the above modeling uncertainties, we find H0 = 86.6+6.8−6.9 km s−1 Mpc−1, when using kinematic priors similar to other studies. When we use a different kinematic prior motivated by Barnabe et al. (2012) [2] but covering the same anisotropic range, we find H0 = 74.5+8.0−7.8 km s−1 Mpc−1. This means that the choice of kinematic modeling and priors have a significant impact on cosmographic inferences. The way forward is either to get better velocity dispersion measures which would down weight the impact of the priors or to construct physically motivated priors for the velocity dispersion model.

Core or Cusps: The Central Dark Matter Profile of a Strong Lensing Cluster with a Bright Central Image at Redshift 1

We present a strong lensing modeling technique based on versatile basis sets for the lens and source planes. Our method uses high performance Monte Carlo algorithms, allows for an adaptive build up of complexity and bridges the gap between parametric and pixel based reconstruction methods. We apply our method to a HST image of the strong lens system RXJ1131-1231 and show that our method finds a reliable solution and is able to detect substructure in the lens and source planes simultaneously. Using mock data we show that our method is sensitive to sub-clumps with masses four orders of magnitude smaller than the main lens, which corresponds to about

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign. I. Overview and classification of candidates selected by two techniques

10^8 M_{\odot}