Day 1017

Friday.


1512.00849
Dust production 0.7-1.5 billion years after the Big Bang
Michałowski

Cosmic dust in an important component of the Universe, and its origin, especially at high redshifts, is still unknown.  Present a simple but powerful method of assessing whether dust observed in a given galaxy could in principle have been formed by AGN stars or SNe.  Using this method, show that for most of the galaxies with detected dust emission between z=4 and 7.5 (1.5-0.7 Billion years after the BB) AGB stars are not numerous and efficient enough to be responsible for the measured dust masses.  SNe could account for most of the dust, but only if all of them had efficiencies close to the maximal theoretically allowed value.  This suggests that a different mechanism is responsible for dust production at high redshifts, and the most likely possibility is the grain growth in the ISM.


1512.00910
The Atacama Cosmology Telescope: Dynamical masses for 44 SZ-selected galaxy clusters over 755 square degrees
Sifón, et al

Present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via SZ by ACT.  Dynamical masses for 18 clusters are reported here for the first time. Using N-body sims, model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies.  Find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7% in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster center.  Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamic mass estimates regardless of the observing strategy.  Cluster masses M200 are in the range (1-15)e14 Msun.  Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1.10±0.13, consistent with previous determinations at these mass scales.


1512.01214
Hyper calibration: a Pan-STARRS1-based recalibration of the Sloan Digital Sky Survey
Finkbeiner, Schlafly, Schlegel, Padmanabhan, et al

Present a recalibration of SDSS photometry with new flat fields and zero points derived from Pan-STARRS1 (PS1).  Using PSF photometry of 60 million stars with 16<r<20, derive a model of amplifier gain and flat-field corrections with per-run RMS residuals of 3 mag in griz bands and 15 mag in u band.  The new photometric zero points are adjusted to leave the median in the Galactic North unchanged for compatibility with previous SDSS work.  Also identify transient non-photometric periods in SDSS ("contrails") based on photometric deviations co-temporal in SDSS bands.  The recalibrated stellar PSF photometry of SDSS and PS1 has an RMS difference of {9,7,7,8} mag in griz, respectively, when averaged over 15' regions.