Day 1167

Friday.  Monday.

1610.01599
Line-of-sight effects in strong lensing: putting theory into practice
Birrer, Welschen, Amara, Refregier

Present a simple method to accurately infer LoS integrated lensing effects for galaxy scale SL systems through image reconstruction. The approach enables to separate WL LoS effects from the main SL deflector.  Test the method using mock data and show that SL systems can be accurate probes of cosmic shear with a precision on the shear terms of ±0.003.  Apply the formalism to reconstruct the lens COSMOS 0038+4133 and its LoS.  In addition, estimate the LoS properties with a halo-rendering estimate based on the COSMOS field galaxies and a galaxy-halo connection.  The two approaches are independent and complementary in their information content.  Find that when estimating the convergence at the SL system, performing a joint analysis improves the measure by a factor of 2 compared to a halo model only analysis.  Furthermore, the constraints of the SL reconstruction lead to tighter constraints on the halo masses of the LoS galaxies.  Joint constraints of multiple SL systems may add valuable information to the galaxy-halo connection and may allow independent WL shear measurement calibrations.


1610.01991
How are galaxies assigned to haloes?  Searching for assembly bias in the SDSS galaxy clustering
Vakili

Clustering of DM haloes has been shown to depend on halo properties beyond mass such as halo concentration, a phenomenon referred to as halo assembly bias.  Standard halo occupation modeling (HOD) in LSS assumes that halo mass alone is sufficient in characterizing the connection between galaxies and haloes.  Modeling of galaxy clustering can ease systematic effects if the number or properties of galaxies are correlated with other halo properties.  Using the Small MultiDark-Planck high resolution N-body simulation and the measurements of the projected 2pt correlation function and the number density of SDSS DR7 main galaxy sample, investigate the extent to which the dependence of halo occupation on halo concentration can be constrained, and to what extent allowing for this dependence can improve the modeling of galaxy clustering.  Given the SDSS clustering data, the constraints on HOD with assembly bias suggests that satellite population is not correlated with halo concentration at fixed halo mass.  Furthermore, in terms of the occupation of centrals at fixed halo mass, the results favor lack of correlation with halo concentration in the most luminous samples (Mr<-21,5,-21), modest levels of correlation of Mr<-20.5,-20,-19.5 samples, lack of correlation for Mr<-19,-18.5 samples, and anti-correlation for the faintest sample Mr<-18.  Show that in comparison with abundance-matching mock catalogs, the findings suggest qualitatively similar but modest levels of assembly bias that is only present in the central occupation.  Furthermore, by performing model comparison based on information criteria, find that in most cases, the standard mass-only HOD model is still favored by the observations.