Day 587

Wednesday.

1402.2277
Investigating evidence for different black hole accretion modes since redshift z~1
Georgakakis et al

Chandra on COSMOS, AEGIS-XD and 4Ms CDFS combined with optical/NIR to determine the rest-frame U-V vs V-J colors of X-ray AGN hosts at mean redshifts 0.40 and 0.85.  This combination of colors (UVJ) provides efficient means of separating quiescent from SF, including dust reddened, galaxies.  Morphological info emphasizes differences between AN split by their UVJ colors.  AGN in quiescent galaxies are dominated by spheroids, while SF hosts are split between bulges and disks.  The UVJ diagram of AGN hosts is then used to set limits on the accretion density associated with evolved and SF systems.  Most of the BH growth since z~1 is associated with SF hosts.  Nevertheless, ~15-20% of the X-ray luminosity density since z~1, is taking place in the quiescent region of the UVJ diagram.  For the z~0.40 subsample, there is tentative evidence that AGN split by their UVJ colors differ in Eddington ratio.  AGN in SF hosts dominate at high Eddington ratios, while AGN in quiescent hosts become increasingly important as a fraction of the total population toward low Eddington ratios.  At higher redshift, z~0.8, such differences are significant at the 2sigma level only at Eddington ratios >1e-3.  These findings are consistent with scenarios in which diverse accretion modes are responsible for the build-up of SMBHs at the centers of galaxies.  Compare results with the GALFORM SM, which postulates two BH fueling modes, the first linked to SF and the second occurring in passive galaxies.  GALFORM predicts a larger fraction of BH growth in quiescent galaxies at z<1, compared to the data.  Relaxing the strong assumption of the model that passive AGN hosts have zero SF rate could reconcile this disagreement.

1402.2280
Galaxy luminosity function and Tully-Fisher relation: reconciled through rotation-curve studies
Cattaneo, Salucci, Papastergis

The relation between galaxy luminosity L and halo virial velocity v_vir required to fit the galaxy LF differs from the observed Tully-Fisher relation between L and disc speed v_rot.  Reproducing the galaxy LF and the TF relation simultaneously problematic for SAMs; study the relation between v_rot and v_vir by fitting observational average rotation curves of disc galaxies binned in luminosity.  Show that the v_rot-v_vir relation obtained this way can fully account for the inconsistency.  The reconciliation of the LF with the TF relation rests on the complex dependence of v_rot on v_vir, which arises because the ratio of stellar mass to DM mass is a strong function of halo mass.

1402.2283
An analytic solution for the minimal bathtub toy model: challenges in the star-formation history of high-z galaxies
Dekel, Mandelker

Study key processes of galaxy evolution and identify robust successes and challenges in reproducing observations at high z.  The source and sink terms of the continuity equations for gas and stars are expressed in simple terms from first principles.  The assumed dependence of SFR on gas mass self-regulates the system into a unique asymptotic behavior, which is approximated by an analytic quasi-steady-state solution (QSS).  Address the validity of the QSS at different epochs independent of earlier conditions.  At high z, where the accretion is assumed to consist of gas only, the sSFR is robustly predicted to be sSFR=[(1+z)/3]^{5/2} Gyr^-1, slightly higher than the cosmological specific accretion rate, in agreement with observations at z=3-8.  The gas fraction is expected to decline slowly, and the observations constrain the SFR efficiency per dynamical time to epsilon[?]=0.02.  The stellar-to-virial mass ratio f_sv is predicted to be constant in time, and the observed value requires an outflow mass-lading factor of eta=1-3, depending on the penetration efficiency of gas into the galaxy. However, at z=2, where stars are also accreted through mergers, the simplest model has an apparent difficulty in matching observations.  The model that maximizes the sSFR, with the outflows fully recycled, falls short by a factor 3 in sSFR, and overestimates f_sv.  With strong outflows, the model can reproduce the observed f_sv but at the expense of underestimating the sSFR by an order of magnitude.  Discuss potential remedies including a bias due to the exclusion of quenched galaxies.

1402.2336
Higher moments of primordial non-gaussianity and N-body simulations
Adhikari, Shandera, Dalal

Perform cosmo N-body sims with non-Gaussian IC generated from two independent fields (purely Gaussian, dominant + local non-Gaussian that is not necessarily weak).  This scenario allows assessment of the relative importance of non-G contributions beyond the skewness, producing a scaling of the higher moments different from (and stronger than) the scaling in the usual single field local ansatz.  Compare semi-analytic prescriptions for the non-G MF, large scale halo bias, and stochastic bias against the simulation results.  Discuss applications of this work to large scale structure measurements that can test a wider range of models for the primordial fluctuations that is usually explored.

1402.2352
Spitzer UltRa Faint SUrvey Program (SURFS UP) I: an overview
Bradac et al

A joint Spitzer and HST program using 10 galaxy clusters as cosmic telescopes to study z>~7 galaxies at intrinsically lower luminosities, enabled by gravitational lensing, than blank field surveys of the same exposure time.  Main goal: measure stellar masses and ages of these galaxies, which are most likely sources of the ionizing photons that drive reionization.  Accurate knowledge of the SF density and SFH at this epoch is necessary to determine whether these galaxies indeed recognized the universe.  Determination of the stellar masses and ages requires measuring rest frame optical light, which only Spitzer can probe for z>7, for a large enough sample of typical galaxies.  Program consists of 550 hours of Spitzer/IRAC of 10 clusters with very well-known mass distributions (i.e., known lens property).  Combine data with archival observations to obtain mosaics with ~30 hrs exposure time in each 3.6 um and 4.5 um in the central (4 arcmin)^2, and ~15 hrs in the flanking fields.  Illustrate survey strategy and characteristics: introduce the sample, present the details of the data reduction and demonstrate that these data are sufficient for in-depth studies of z>7 sources (e.g., using a z=9.5 galaxy behind a cluster lens).  For the first cluster of the survey (Bullet), released all high-level data mosaics and IRAC PSF models.  Plan to release data products for the entire survey.