Day 742

Thursday.

1409.2883
A uniform history for galaxy evolution
Steinhardt, Speagle

Recent observations indicate a remarkable similarity in the properties of evolving galaxies at fixed mass and redshift; possible that most galaxies may evolve with a common history encompassing star formation, quasar accretion, and eventual quiescence.  Quantify this by defining a "synchronization timescale" for galaxies as a function of mass and z that characterizes the extent to which different galaxies of a common mass are evolving in the same matter at various cosmic epochs.  Measure this synchronization timescale using 9 different SF galaxy observations from the literature and SDSS quasar observations spanning 0<z<6.  This synchronization timescale is a constant, approximately 1.5 Gyr for all combinations of mass and time.  Also find that the ratio between the stellar mass of galaxies turning off SF and BH mass mass of turnoff quasars is approximately 30:1, much lower than the 500:1 for quiescent galaxies at low redshift.  As a result, propose a model in which the SF "main sequence", analogous quasar behavior, and other observations form a galactic evolution "main sequence", in which SF occurs earliest, followed by SMBH accretion, and feedback between the two are dominated by deterministic rather than stochastic processes.

1409.2900
Characterizing SL2S galaxy groups using the Einstein radius
Verdugo et al

Analyze Einstein radius theta_E and compare with the distance from the arcs to the center of the lens R_A. Find corruption between theta_E and R_A, but with large scatter.  Find a weak evidence of anti-correlation between R_A and z, with log R_A=0.58pm0.06-0.04pm0.1z, suggesting a possible evolution of the Einstein radius with z, as previously reported.  Results show that R_A is correlated with L and N (more luminous and richer groups have greater R_A), and a possible correlation between R_A and the N/L ratio.  Analysis indicates that R_A is correlated with theta_E in the sample, making R_A useful to characterize properties like L and N in galaxy groups.  Additionally, present evidence suggesting that the Einstein radius evolves with z.