Day 627

Monday.

1404.2930
The Spitzer South Pole Telescope Deep Field Survey: linking galaxies and haloes at z=1.5
Martinz-Manso, Gonzalez, Ashby, Stanford, Brodwin, Holder, Stern

An analysis of the clustering of high-z galaxies in the 94 deg2 Spitzer-SPT Deep Field survey.  Applying flux and color cuts to the MIR photometry efficiently selects galaxies at z~1.5 in the stellar mass range 1e10-11 Msun, making this ample the largest used so far to study such a distant population.  Measure the angular correlation function in different flux-limited samples at scales >6" (corresponding to physical distances >0.05Mpc) and thereby map the one- and two-halo contributions to the clustering.  Fit halo occupation distributions and determine how the central galaxy's stellar mass and satellite occupation depend on the halo mass.  Measure a prominent peak in the stellar-to-halo mass ratio at a halo mass of log(Mhalo/Msun)=12.44, 4.5x higher than the z=0 value.  This supports the idea of an evolving mass threshold above which SF is quenched.  Estimate the large-scale bias in the range b_g=2-4 and the satellite fraction to be f_sat~0.2, showing a clear evolution compared to z=0.  In addition, measure that this fraction mildly increases with the stellar mass limit at z=1.5, which is the opposite of the behavior seen at low-z.

1404.2933
The photon underproduction crisis
Kollmeier, et al

Examine the statistics of the low-z Lyman-alpha forest from smoothed particle hydro sims in light of recent improvements n the estimated evolution of the cosmic UVB and recent observations from COS.  Find that the value of the metagalactic photoionization rate required by the simulations to match the observed properties of the low-z Ly-a forest is a factor of 5 larger than the value predicted by state-of-the-art models for the evolution of this quantity.  This mismatch results in the mean flux decrement of the Lya forest being under predicted by at least a factor of 2 (a 10 sigma discrepancy with observations) and a column density distribution of Lya forest absorbers systematically and significantly elevated compared to observations over two decades in column density.  Examine potential resolutions to this mismatch and find that either conventional sources of ionizing photons (galaxies and quasars) must be significantly elevated relative to current observational estimates or our theoretical understanding of the low-z universe is in need of substantial revision.

1404.2936
North-South non-Gaussian asymmetry in PLANCK CMB maps
Bernui, Oliveira, Pereira

Directional statistical analyses, using the variance momentum, on the four FG-cleaned Planck maps evidence a net dipolar distribution pointing in the direction (l,b)~(245deg,-35deg), consistent with the direction of the N-S asymmetry phenomenon.  Although the magnitude of this variance dipole is not statistically significant, ~85% CL, as compared with maps produced with similar directional analysis, it evidences interesting attributes.  First, Planck's variance dipole - magnitude and direction - appears robust against the four different component separation algorithms (employed to clean contaminants in Planck data), various Planck masks, map's pixelization parameters, and the addition of inhomogeneous real noise. Moreover, Planck's variance dipole magnitude has a curious behavior: it gets lower values for larger sky-cut masks, independent of the map analyzed, strongly suggesting two causes: either FG remnants that diminish their influence when severe masks are used or CMB power from the quadrupole-octupole alignment whose larger influence is cut off in the region where the masks act.  Extra analyses were performed here to elucidate this point.  From one side, show that Planck's variance dipole is robust in magnitude and direction against frequency dependence, disfavoring the FG residuals as an explanation.  From the other side, shuffling Planck's quadrupole and octupole components leaves their magnitudes intact: the result was a variance dipole with half of its original magnitude pointing in a different direction, showing that these CMB multipoles have a definitive effect on the PLanck's variance dipolar distribution.  Albeit the FG residuals can not be excluded altogether, analysis suggest that the main reason for this variance dipole is the CMB quadrupole-octupole alignment phenomenon.