Day 831

Wednesday.

1502.02661
The dust sublimation radius as an outer envelope to the bulk of the narrow Fe Kalpha line emission in Type 1 AGN
Gandhi, Hoenig, Kishimoto

The Fe Kalpha emission lines is the most ubiquitous feature in the X-ray spectra of AGN, but the origin of its narrow core remains uncertain.  Investigate the connection between the sizes of the Fe Kalpha core emission regions and the measured sizes of the dusty tori in 13 local Type 1 AGN.  The observed Fe Kalpha emission radii (R_fe) are determined from spectrally resolved line widths in X-ray grating spectra, and the dust sublimation radii (R_dust) are measured either from optical/NIR reverberation time lags or from resolved NIR interferometric data.  This direct comparison shows that the dust sublimation raids forms an outer envelope to the bulk of the Fe Kalpha emission.  R_fe matches R_dust well in the AGN with the best constrained line widths currently.  In a significant fraction of objects without a clear narrow line core,  R_fe is similar to, or smaller than the radius of the optical broad line region.  These facts place important constraints on the torus geometries for the sample.  Extended tori in which the solid angle of fluorescing gas peaks at well beyond the dust sublimation radius can be ruled out.  Also test for luminosity scalings of R_fe, finding that Eddington ratio is not a prime driver in determining the line location in the sample.  Large uncertainties on the line core widths preclude more detailed investigations at present, a limitation which Astro-H will help to overcome.

1502.02681
On the cosmic evolution of the specific star formation rate
Lehnert et al

The apparent correlation between the sSFR and the total stellar mass M* of galaxies is a fundamental relationship indicating how they formed their stellar populations.  To attempt to understand this relation, hypothesize that the relation and its evolution is regulated by the increase in the stellar and gas mass surface density in galaxies with redshift, which is itself governed by the angular momentum of the accreted gas, the amount of available gas, and by self-regulation of star formation.  This model can reproduce the sSFR-M* relations at z~1-2 by assuming gas fractions and gas mass surface densities similar to those observed for z=1-2 galaxies.  Further argue that it is the increasing angular momentum with cosmic time that causes a decrease in the surface density of accreted gas.  The gas mass surface densities in galaxies are controlled by the centrifugal support (i.e., angular momentum), and the sSFR is predicted to increase as, sSFR(z)=(1+z)^3/t_H0, as observed (where t_H0 is the Hubble time and no free parameters are necessary) . At z>~2, argue that SF is self-regulated by high pressures generated by the intense SF itself.  The SF intensity must be high enough to either balance the hydrostatic pressure (a rather extreme assumption) or to generate high turbulent pressure in the molecular medium which maintains galaxies near the line of instability (i.e., Toomre Q~1).  The most important factor is the increase in stellar and gas mass surface density with redshift, which allows distant galaxies to maintain high levels of sSFR.  Without a strong feedback from massive stars, such galaxies would likely reach very high sSFR levels, have high SF efficiencies, and because strong feedback drives outflows, ultimately have an excess of stellar baryons.

1502.02867
The galaxy-halo connection from a joint lensing, clustering and abundance analysis in the CFHTLenS/VIPERS field
Coupon,  et al

Present new constraints on the relationship between galaxies and their host DM haloes, measured from the location of the peak of the stellar-to-halo mass ratio (SMHR), up to the most massive galaxy clusters at z~0.8 and over a volume of nearly 0.1 Gpc^3.  Use a unique combination of deep observations in the CFHTLenS/VIPERS field from the near-UV to the near-IR, supplemented by ~60k secure spec-z, analyzing galaxy clustering, gg lensing and the stellar MF.  Interpret measurements within the HOD framework, separating the contributions from central and satellite galaxies.  Find that the SHMR for the central galaxies peaks at M_h,peak = 1.9e12 Msun with an amplitude of 0.025, which decreases to ~0.001 for massive haloes (M_h>1e14 Msun).  Compared  to central galaxies only the total SHMR (including satellites) is boosted by a factor 10 in the high-mass regime (cluster-size halos), a result consistent with cluster analyses from the literature based on fully independent methods.  After properly accounting for differences in modeling, compare results with a large number of results from the literature up to z=1: find good general agreement, independently of the method used, within the typical stellar-mass systematic errors at low to intermediate mass (M*<1e11 Msun) and the statistical errors above.  Have also compared SHMR results to semi-analytic simulations and found that the SHMR is tilted compared to measurements in such a way that they over-(under-) predict SF efficiency in central (satellite) galaxies.