Day 603

Monday.

1403.1578
Predicting galaxy star formation rates via the co-evolution of galaxies and halos
Watson, Hearin, Berlind, Becker, Behroozi, Skibba, Reyes, Zentner

Test the age matching hypothesis that the SFR of a galaxy is determined by its DM halo formation history, and as such, that more quiescent galaxies reside in older halos.  This simple model has been remarkably successful at predicting color-based galaxy statistics at low z as measured in the SDSS.  To further test this method with observations, present new SDSS measurements of the galaxy 2pt correlation function and galaxy-galaxy lensing as function of stellar mass and SFR, separated into quenched and SF galaxy samples.  Find that the age matching model is in excellent agreement with these new measurements.  Also employ a galaxy group finder and show that the model is able to predict: (1) the relative SFRs of central and satellite galaxies, (2) the SFR-dependence of the radial distribution of satellite galaxy populations within galaxy groups, rich groups, and clusters and their surrounding larger scale environments, and (3) the interesting feature that the satellite quenched fraction as a function of projected radial distance from the central galaxy exhibits an ~r^-.15 slope, independent of environment.  The accurate prediction for the spatial distribution of satellites is intriguing given the fact that the satellite-specific processes after infall is not modeled, and that in the model the virial radius does not mark a special transition region in the evolution of a satellite, contrary to most galaxy evolution models.  The success of the model suggests that present-day galaxy SFR is strongly correlated with halo mass assembly history.

1403.1585
The evolution of the star forming sequence in hierarchical galaxy formation models
Mitchell, Lacey, cole, Baugh

It has been argued that the sSFRs of SF galaxies inferred form observational data decline more rapidly below z=2 than is predicted by hierarchical galaxy formation models.  Present a detailed analysis of this problem by comparing predictions from the GALFORM SAM with an extensive compilation of data on the average SFRs of SF galaxies.  Also use this data to infer the form of the stellar mass assembly histories of SF galaxies.  Analysis reveals that the currently available data favors a scenario where the stellar mass assembly histories of SF galaxies rise at early times and then fall towards the present day [the histories rise?].  In contrast, model predicts stellar mass assembly histories that are almost flat below z=2 for SF galaxies, such that the predicted SFRs can be offset with respect to the observational data by factors of up to 2-3.  This disagreement can be explained by the level of coevolution between stellar and halo mass assembly that exists in contemporary galaxy formation models.  In turn, this arises because the standard implementations of SF and SN feedback used in the models result in the efficiencies of these process remaining approximately constant over the lifetime of a given SF galaxy.  Demonstrate how a modification to the timescale for gas ejected by feedback to be reincorporated into galaxy haloes can help to reconcile the model predictions with the data.

1403.1667
The rest-frame sub millimeter spectrum of high-redshift, dusty, star-forming galaxies
Spilker et al

As the title says.  22 sources, 2.0<z<5.7.

1403.1705
Distribution of slow and fast rotators in the Fornax cluster
Scott et al

IFS of 10 early-type galaxies in the nearby, low-mass Fornax cluster, from which spatially resolved stellar kinematics is derived.  Based on the morphologies of their stellar velocity maps, classify 2/10 galaxies as slow rotators, with the remaining 8 galaxies fast rotators.  Supplementing the integral field observations with morphological and kinematic data from the literature, analyze 30 galaxies with M_K<-21.5 mag (M*~6e9 Msun).  The slow rotator fraction within 1 virial radius is 7%.  13% of early-type galaxies are slow rotators, consistent with the observed fraction in other galaxy aggregates.  The fraction of slow rotators in Fornax varies with cluster-centric radius, rising to 16% of all kinematic types within the central 0.2 virial radii, from 0% in the closer outskirts.  Find that, even in mass-matched samples of slow and fast rotators, slow rotators are found preferentially at higher projected environmental density than fast rotators.  This demonstrates that dynamical friction alone cannot be responsible for the differing distributions of slow and fast rotators.  For dynamical friction to play a significant role, slow rotators must reside in higher mass sub-haloes than fast rotators and/or form in the centers of groups before being accreted on to the cluster.