Day 429

Friday.
1305.1630
The cosmic star formation rate from the faintest galaxies in the unobservable universe
Kistler, Yuksel, Hopkins

Deep surveys see only the brightest galaxies at any epoch and must extrapolate to arbitrary lower limit to estimate the total rate of SF.  First argue: galaxy populations seen in LBG surveys yield a GRB rate at z>8 that is an order of magnitude lower than observed; find that integrating the inferred UV luminosity functions down to M_UV~-10 brings LBG- and GRB-inferred SFR density values into agreement up to z~8.  But GRBs favor a far larger amount of as yet unseen star formation at z>9.  Suggest that the SFR density may only slowly decline out to z~11, in accord with WMAP and Planck reionizaton results, and that GRBs may be useful in measuring the scale of this multitude of dwarf galaxies.

1305.1881
AGN in dusty hosts: implications for galaxy evolution
Symeonidis et al

Find strong empirical evidence for connection between SB occurrence and a luminous AGN phase.  Find: locus of type-2 AGN hosts in the optical color-magnitude and color-color space significantly overlaps with that of IR-luminous [dusty, I guess] galaxies.  Propose that, when simultaneously building their BH and M*, type-2 AGN hosts are located in the same part of color-color space as dusty SF galaxies.  In fact, results show that IR-luminous galaxies at z<1.5 are on average 3x more likely to host a type-2 AGN than would be expected serendipitously, if AGN and SF events were unrelated.  In addition, the optical and IR properties of the AGN/SB hybrid systems tentatively suggest that the AGN phase might be coeval with a particularly active phase in a galaxy's SF history.  Also find a significant fraction of type2 AGN hosts offset from the dusty galaxy sequence in color-color space, possibly representing a transitional or post-SB phase in galaxy evolution.  Findings are consistent with a scenario whereby AGN play a role in the termination of SF in massive galaxies.

1305.1891
Probability Friends-of-Friends (PFOF) group finder: performance study and observational data applications on photometric surveys
Jian et al

As the title says.

1305.1928
Evidence for dust destruction from the early-time colour change of GRB 120119A
Morgan, Perley, Cenko, Bloom, .. Richards, Filippenko, et al

Broadband observations of GRB, early-time afterglow began under 15s after the burst in the host frame (z=1.73), yield constraints on the burst energetics and local environment.  Exhibit a significant red-to-blue colour change in the first ~200s after the trigger at levels heretofore unseen in GRB afterglows.  This color change (coincident with the final phases of the prompt emission) is a hallmark prediction of the photodestruction of dust in GRB afterglows.  Test whether dust-destruction signatures are significantly distinct from other sources of color change, namely a change in the intrinsic spectral index beta.  Find: a time-varying power-law spectrum alone cannot adequately describe the observed color change, and allowing for dust destruction (via a time-varying A_V) significantly improves the fit.  While not definitively ruling out other possibilities, this event provides the best support yet for the direct detection of dust destruction in the local environment of a GRB.

1305.1943
Quiescent galaxies in the 3D-HST survey: spectroscopic confirmation of a large number of galaxies with relatively old stellar populations at z~2
Whitaker, van Dokkum, et al

Galaxies with relatively old stellar populations (i.e., with metal absorption lines) already existed when the universe was ~3 Gyr old, and that rest-frame color selection techniques can efficiently select them.  Average age of 1.3 Gyr, from stellar population fits.  Redder, the older (color correlates to age).  Also find [OIII] and Hbeta emission, although spectrum is dominated by an evolved stellar population.  Emission is more centrally concentrated than the continuum with L_[OIII]=1.7e40 erg/s, indicating residual central SF or nuclear activity.

1305.1964
Collisions with other universes: the optimal analysis of the WMAP data
Osborne, Senatore, Smith

Search for evidence of this Universe born out of a nucleation bubble from a phase of false vacuum eternal inflation, in WMAP7.  Find no detectable signal.