Day 390

Tuesday.

1303.3887
Probing patchy reionization through tau-21cm correlation statistics
Meerburg, Dvorkin, Spergel

Free electrons traced by optical depth tau, neutral hydrogen by 21cm emission.  Their correlation is sensitive to the detailed physics of reionization.  If reionizaton occurs through the merger of relatively large halos hosting an ionizing source, the free electrons and neutral hydrogen are anti-correlated for most of the reionization history.  A positive correlation can occur when the halos that can form an ionizing source are small.  A measurement of this sign change in the cross-correlation would directly measure the bubble bias, and the halo mass.  Estimate S/N of the cross-correlation using the estimator for inhomogeneous reionization tau_lm.  Find that with upcoming radio interferometers and CMB experiments, the cross-correlation is measurable going up to multiples l~1000.  Also derive parameter constraints and conclude that, despite the foregrounds, the cross-correlation proofs a complementary measurement of the EoR parameters to the 21cm and CMB polarization auto-correlations expected to be observed in the coming decade.

1303.3915
The IMACS Cluster building survey. I. Description of the survey and analysis methods
Oemler, Dressler, Gladders, ... et al

IMACS spectrograph on the 6.5m Baade telescope, survey LS environment surrounding rich intermediate-z clusters of galaxies.  Goal: understand the process which may be transforming SF field galaxies into quiescent cluster members as groups and individual galaxies fall into the cluster from the surrounding supercluster.  Describe data taking and reduction methods.  Demonstrate that there is a tight relation between the observed SFR per unit B luminosity, and the ratio of the extinctions of the stellar continuum and the optical emission lines; obtain accurate extinction-corrected colors of galaxies.  Determine new criteria for the existence of ongoing and recent starbursts in galaxies.

1303.3916
The IMACS cluster building survey.  III. the star formation histories of field galaxies
Oemler et al

SFR from z=0,60 to present; data from IMACS Cluster building survey and from nearby galaxy surveys.  Find a rapid evolution of M*_B consistent with that found in other deep surveys; at the present epoch M*_B is evolving at the rate of 0.38/Gyr, several times faster than the predictions of simple models for the evolution of old, coeval galaxies.  The evolution of the distribution of sSFR is also too rapid to explain by such models.  Demonstrate the SB cannot, in principle, explain the evolution of the sSFR distribution.  But the rapid evolution of both M*_B and the sSFR distribution can be explained if some fraction of galaxies have SFR characterized by both short rise and fall times and by an epoch of peak SF more recent than the majority of galaxies.  Although galaxies of every stellar mass up to 1.5e11 Msun show a range of epochs of peak SF, the fraction of "younger" galaxies falls from about 40% at a mass of 4e10 Msun to 0 at a mass of 1.4e11 Msun.  The incidence of younger galaxies appears to be insensitive to the density of the local environment; but does depend on group membership: relatively isolated galaxies are much more likely to be young than are group members.

1303.4302
The SDSS-III Baryonic oscillation spectroscopic survey: constraints on the integrated Sachs Wolfe effect
Hernandez-Monteagudo, Ross, Cuesta, ... et al

Construct a template of the projected density distribution up to z~0.7 by using the LGs from SDSS DR8.  Use a photo-z catalogue trained with more than a 100k galaxies from BOSS in the SDSS DR8 imaging area.  Consider two different LG samples whose selection matches that of SDSS-III/BOSS: the LOWZ sample (0.15<z<0.5) and the CMASS sample (0.4<z<0.7).  When building the LG density maps, use the information from star density, survey footprint, seeing conditions, sky emission, dust extinction and airmass to explore the impact of these artifacts on the two LG samples.  In agreement with previous studies, find that the CMASS sample is particularly sensitive to Galactic stars, which dominate the contribution to the auto-angular power spectrum below L=7.  Other potential systematics affects mostly the low multipole range 2<l<7, but leave fluctuations on small scales unchanged.  The resulting power spectra in the multipole range 2<l<100 for the LOWZ, CMASS and ALL samples are compatible with linear LCDM expectations and constant bias values of b=1.98, 2.08, 1.88, respectively, with no traces of non-Gaussianity f_NL=59pm75 at 95% CL for the full sample in the range 4<l<100.  After cross-correlating WMAP-9yr data with the LOWZ+CMASS LG density field, the ISW signal is detected at the level of 1.62-1.69 sigma.  While this result is in close agreement with predictions from Monte Carlo simulations in the concordance LCDM model, it cannot rule out by itself an Einstein-de Sitter scenario, and has a moderately low signal compared to previous studies conducted on subsets of this LG sample.