Day 613

Tuesday.

1403.5559
The extent of the MgII absorbing circum-galactic medium of quasars
Farina et al

Investigate the extent and the properties of the MgII cool, low-density absorbing gas located in the halo and in the circum-galactic environment of quasars, using a sample of 31 projected quasar pairs with impact parameter pd<200kpc in the range 0.4<z<1.6.  In the transverse direction, detect 18 MgII absorbers associated with the FG quasars, while no absorption system originated by the gas surrounding the quasar itself is found along the LoS.  This suggests that the quasar emission induces an anisotropy in the absorbing gas distribution.  Observations indicate that the covering fraction (fc) of MgII absorption systems with rest frame equivalent width Wr(2796)>0.3 A. ranges from fc~1.0 at pd<65kpc to fc~0.2 at pd>150kpc, and appears to be higher than for galaxies.  Findings support a scenario where the luminosity/mass of the host galaxies affect the extent and the richness of the absorbing MgII circum-galactic medium.

1403.5563
Galaxies in filaments have more satellites: the influence of the cosmic web on the satellite luminosity function in the SDSS
Guo, Tempel, Libeskind

Investigate if the satellite luminosity function (LFs) of primary galaxies identified in SDSS DR8 depends on whether the host galaxy is in a filament or not.  Isolated primary galaxies are identified in the SDSS spectra sample while potential satellites are searched for in the much deeper photometric sample.  Filaments are constructed from the galaxy distribution by the "Bisous" process.  Isolated primary galaxies are divided into two subsamples: those in filaments and those not in filaments.  Examine the stacked mean LF of each sample and found that, in the mean, the satellite LFs of primary galaxies (extending to at least 4 magnitude fainter than the primary galaies) in filaments is significant higher than those of primary galaxies not in filaments.  The filamentary environment can increase the abundance of the brightest satellites (Msat<Mprim+2), by a factor of ~2 compared with non-filament galaxies.  This result is independent of primary galaxy magnitude, although the satellite LF of galaxies in the faintest magnitude bin is too noisy to determine if such a dependent exists.  Since filaments are extracted from a flux-limited sample, consider the possibility that the difference in satellite LF is due to a z, color, or environment bias, finding these to be insufficient to explain the result.  The dependence of the satellite LF on the cosmic web suggests that the filamentary environment may have a strong effect on the efficiency of galaxy formation.

1403.5755
Absolute-magnitude distributions of supernovae
Richardson et al

As the title says.  For 7 SN types.

1403.5898
Background power subtraction in Lyman-alpha forest
Irsic, Slosar

When measuring the 1d PS of the Lya forest, it is common to measure the PS in flux fluctuations red-ward of the Lya emission of quasars and subtract this power form the measurements of the Lya flux power spectrum.  This removes excess power present in the Lya forest which is believed to be dominated by metal absorption by the low-redshift metals uncorrelated with the neutral hydrogen absorbing in Lya.  In this report, note that assuming the contaminants are additive in optical depth, the correction contains a second order term.  Estimate the magnitude of this term for two currently published measurements of the 1d Lya flux PS and show that it is negligible for the current generation of measurements.  However, future measurements will have to take this into account when errors improve by a factor of 2 or more.

0511164
Galaxy halo mass and satellite fractions from galaxy-galaxy lensing in the SDSS: stellar mass, luminosity, morphology, and environment dependencies
Mandelbaum, Seljak, Kauffmann, Hirata, Brinkmann

The relationship between galaxies and DM can be characterized by the halo mass of the central galaxy and the fraction of galaxies that are satellites.  Present observational constraints from the SDSS on these quantities as a function of r-band luminosity and stellar mass using gg WL, with a total of 351k lenses.  Use stellar masses derived from spectroscopy and virial halo masses derived from WL to determine the efficiency with which baryons in the halo of the central galaxy have been converted into stars.  Find that an L* galaxy with a stellar mass of 6e10 Msun is hosted by a halo with mass 1.4e12 Msun/h, independent of morphology, yielding baryon conversion efficiencies of 17 (early) and 16 (late)% at the 95% CL (statistical, not including systematic uncertainty due to assumption of a universal IMF).  Find that for a given stellar mass, the halo mass is independent of morphology below M*=1e11 Msun, in contrast to typically a factor of 2 difference in halo mass between ellipticals and spirals at a fixed luminosity.  This suggests that stellar mass is a good proxy for halo mass in this range and should be used preferentially whenever a halo mass selected sample is needed.  For higher stellar masses, the conversion efficiency is a declining function of stellar mass, and the differences in halo mass between early and late types become larger, reflecting the fact that most group and cluster haloes with masses above 1e13 Msun host ellipticals at the center, while even the brightest central spirals are hosted by haloes of mass below 1e13 Msun.