Day 687

Friday.

1406.6692
The VIMOS public extragalactic redshift survey (VIPERS).  Measuring nonlinear galaxy bias at z~0.8
Di Porto, Branchini, ... et al

Use the first release of VIPERS of ~50k objects to measure the biasing relation between galaxies and mass in 0.5<z<1.1.  Estimate the PDF of VIPERS galaxies from counts in cells and, assuming a model for the mass PDF, infer their mean bias relation.  The reconstruction of the bias relation from PDFs is performed through a novel method that accounts for Poisson noise, redshift distortions, inhomogeneous sky coverage and other selection effects.  With this procedure, constrain galaxy bias and its deviations from linearity down to scales as small as 4 Mpc/h and out to z=1.1.  Detect small (~3%) but significant deviations from linear bias.  The mean biasing function is close to linear in regions above the mean density.  The mean slope of the biasing relation is a proxy to the linear bias parameter.  It increases both with luminosity, in agreement with results of previous analyses, and with redshift.  However, detect a strong bias evolution only for z>0.9 in agreement with some, but not all, previous studies.  Also detected a significant increase of the bias with the scale, from 4 to 8 Mpc/h, now seen for the first time out to z=1.  The amplitude of NL depends on redshift, luminosity and on scales but no clear tree is detected.  Thanks to the large cosmic volume probed by VIPERS, find that the mismatch between the previous estimates of bias at z~1 from zCOSMOS and VVDS-Deep samples is fully accounted for by cosmic variance.  The results of the work confirm the importance of going beyond the over-simplistic linear bias hypothesis showing that NLs can be accurately measured through the applications of the appropriate statistical tools to existing datasets like VIPERS.

1406.6762
Constraining dust formation in high-redshift young galaxies
Hirashita, Ferrara, Dayal, Ouchi

Core-collapse SNe are believed to be the first significant source of dust in the Universe.  Such SNe are expected to be the main dust producers in young high-z LAEs given their young ages, providing an excellent testbed of SN dust formation models during the early stages of galaxy evolution.  Focus on the dust enrichment of a specific, luminous LAE (Himiko, z~6.6) for which a stringent upper limit of 52.1 uJy (3sigma) has recently been obtained from ALMA continuum observations at 1.2 mm.  Predict its sub millimeter dust emission using detailed models that follow SN dust enrichment and destruction and the equilibrium dust temperature, and obtain a plausible upper limit to the dust mass produced by a single SN: m_d,SN<0.15-0.45 Msun, depending on the adopted dust optical properties.  These upper limits are smaller than the dust mass deduced for SN1987A and that predicted by dust condensation theories, implying that dust produced in SNe are likely to be subject to reverse shock destruction before being injected into the ISM.  Finally, provide a recipe for deriving m_d,SN from sub millimeter observations of young, metal poor objects wherein condensation in SN ejecta is the dominant dust formation channel.