Day 863

Friday.


1504.00362
The Illustris simulation: public data release
Nelson, et al

First public data release of Illustris: a suite of large volume, cosmo hydro sim with the moving-mesh code Arepo and including a comprehensive set of physical models critical for following the formation and evolution of galaxies across cosmic time.  Each simulates a volume of (106.5 Mpc)^3 and self-consistently evolves 5 different types of evolution elements from a starting redshift of z=127 to the present day, z=0.  These components are: DM particles, gas cells, passive gas tracers, stars and stellar wind particles, and SMBHs.  This data release includes the snapshots at all 136 available z, halo and sub halo catalogs at each snapshot, and two distinct merger trees.  Six primary realizations of the illustrious volume are released, including the flagship Illustris-1 run.  These include 3 resolution levels with the fiducial "full" baryonic physics model, and a DM only analog for each. In addition, provide 4 distinct, high time resolution, smaller volume "sub boxes".  The total data volume is ~265 TB, including ~800 full volume snapshot and ~30k sub snapshots.  This paper describes the released data products as well as tools developed for their analysis.  All data may be directly downloaded in its native HDF5 format.  Additionally, release a comprehensive, web-based API which allows programmatic access to search and data processing tasks.  In both cases, provide example scripts and a getting-started guide in several languages: currently, IDL, Python and Matlab.  Finally, this paper addresses scientific issues relevant for the interpretation of the simulations, serves as a pointer to published and on-line documentation of the project, describes planned future additional data releases, and comments on technical aspects of the release.


1504.00598
Ultraviolet morphologies and star-formation rates of CLASH brightest cluster galaxies
Donahue, et al

BCGs are usually quiescent, but many exhibit SF.  Exploit the opportunity provided by rest-frame UV imaging of galaxy clusters in CLASH Multi-Cycle Treasury Project to reveal the diversity of UV morphologies in BCGs and to compare them with recent simulations of the cool, SF gas structures produced by precipitation-driven feedback.  All of the CLASH BCGs are detected in the rest-frame UV (280 nm), regardless of their SF activity, because evolved stellar populations produce a modest amount of UV light that traces the relatively smooth, symmetric, and centrally peaked stellar distribution seen in the near IR.  UV morphologies among the BCGs with strong UV excesses exhibit distinctive knots, multiple elongated clumps, and extend filaments of emission that distinctly differ from the smooth profiles of the UV-quitet BCGs.  These structures, which are similar to those seen in the few SF BCGs observed in the UV at low z, are suggestive of bi-polar streams of clumpy SF, but not of spiral rms of large, kpc-scale disks.  Based on the number of streams and lack of culprit companion galaxies, these streams are unlikely to have arisen from multiple collisions with gas-rich galaxies.  These SF UV structures are morphologically similar to the cold-gas structures produced in simulations of precipitation-dirven AGN feedback in which jets uplift low-entropy gas to greater altitudes, causing it to condense.  Unobscured SFRs estimated from CLASH UV images using the Kennicutt relation range up to 80 solar masses per year in the most extended and highly structured systems.  The circumgalactic gas-entropy threshold for SF in CLASH BCGs at z~0.2-0.5 is indistinguishable from that for clusters at z<0.2.