Day 403

Thursday.

1304.0764
Weak lensing analysis of RXC J2248.7-4431
Gruen [Daniel!], .. Seitz, et al

WL analysis of massive cluster at z=0.3475 with SL features covered by HST/CLASH survey.  UBVRIZ imaging of WFI, measure photo-z and galaxy shapes; mass peak at 5 sigma.  Density parametrized as NFW, fitting for M_200 = 3e15 Msun and c = 2.6 pm 1.5.  Second cluster found inside the FoV at z~0.6, with NFW mass of 4e14 Msun.

1304.0765
Models for the mass function and assembly histories of dark haloes: an approach to inventory isolated overdense regions in random fields
Firmani, Avila-Reese

Introduce a probability conditional formalism (CF) based on an inventory of isolated overdense regions in a density random field, for a statistical description of the evolution of density fluctuations that agrees with numerical simulations [this sentence is too complicated].  Useful for describing the MF of dark haloes, theirm ass aggregation histories (MAHs), and merging rates (MRs).  CF focuses on virialized regions in a self-consistent way rather than in mass elements, and it offers an economical description for a variety of random fields.  Within the framework of the CF, confirm that for a Gaussian field, it is not possible to reproduce MF, MAH, and MR of haloes both for a constant and moving barrier.  Develop an inductive method of constraining the cumulative conditional probability from a given halo MF description; using the CF, calculate the halo MAGs and MRs.  Apply this method to MF measured in numerical simulations, and find a reasonable solution, justified by a mass conversation argument, if rescaling of the simulation virial mass by +30%, and a slight deviation from Gaussianity.  Both the MAH and MR obtained by MC merger tree agree with the predictions of numerical simulations.  Discuss on the necessity of rescaling the virial mass in simulations when comparing with analytical approaches on the ground of the matter not accounted as part of the haloes and the halo mass limit due to numerical.  Analysis supports the presence of a diffuse DM component that is not taken into account in the measured halo MFs inasmuch as it is not part of the collapsed structures.  [I didn't understand this abstract at all.  I just typed it out.]

1304.0768
The discovery of the most distant known type Ia supernova at redshift 1.914
Jones, ... Riess, ... Filippenkko, et al

As the title says.

1304.0770
Galaxy clusters around radio-loud AGN at 1.3<z<3.2 as seen by Spitzer
Wylezalek et al

Clusters Around Radio-Loud AGN (CARLA) Spitzer snapshot program.  For 387 fields, reach 22.6/22.9 mags at 3.6/4.5um at 95% completeness (~2-3x fainter than L* at this z range).  Find: 92% of the radio-lound AGN reside in environments richer than average.  Majority (55%) of the radio-loud AGN fields are found to be overdense at >2 sigma; 10% are overdense at >5 sigma.  A clear rise in surface density of IRAC-selected sources towards the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN.  Results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-z galaxy (proto-)clusters.  Find no correlation of environment with either AGN type or radio luminosity.  Find a decrease in density with z, consistent with galaxy evolution for this uniform, flux-limited survey.  These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.

1304.0771
Thermal and chemical evolution of collapsing filaments
Gray, Scannapieco

Filaments: important reservoir of gas for galaxy growth and accretion.  Present high-res sims of thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from H, O, and C.  Study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity.  In low-z, Z~0.1 Z_sun filaments, the evolution is determined completely by the initial cooling time.  If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules.  In high-z, Z=1e-3 Z_sun filaments, the collapse proceeds much more slowly.  This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient.  Finally, study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby SB dwarf galaxy thought to be fueled by the accretion of filament gas.  In contrast to the fiducial case, a substantial density peak forms at the center of the potential.  This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur.  Find that similar accretion rates achieved [in sims, presumably] as NGC 5253, but the 2d simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

1304.0795
Outflow vs. infall in spiral galaxies: metal absorption in the halo of NGC 891
Bregman, Miller, Seitzer, Cowley, Miller

Accreting gas (onto a galaxy) has low metallicity, while halo gas due to galactic fountain will be of near-solar metallicity.  Test these predictions by measuring the metal absorption line properties of halo gas 5 kpc above the plane of the edge-on galaxy NGC 891, using observations with HST toward a bright BG quasar.  Metal absorption lines of FE II, Mg II, and Mg I in the halo are clearly seen, and combined with deep HI observations, able to place constraints on the metallicity of te halo gas.  Difference in Fe/H and Mg/H, probably due to differential depletion onto grains.  Correct for depletion effects, both elements have approximately solar or even supersolar abundances.  This suggests that the gas is from the galaxy disk, probably expelled into the halo by a galactic fountain, rather than from accretion of intergalactic gas, which would have low metallicity.  The abundances would be raised by significant amounts if the absorbing gas lies in a few clouds with thermal widths smaller than the rotational velocity of the halo.  If this is the case, both the abundances and Mg/Fe would be supersolar.

1304.0824
The ACS Virgo cluster survey.  XVII.  The spatial alignment of globular cluster systems with early-type host galaxies
Wang, .. Blakeslee, Mei, et al

In host galaxies with visible elongation (epsilon > 0.2) and intermediate to high luminosities (M_z<-19), the GCs are preferentially aligned along the major axis of the stellar light.  The red (metal-rich) GC subpopulations show strong alignment with the major axis of the host galaxy, which supports the notion that these GCs are associated with metal-rich field stars.  The metal-rich GCs in lenticular galaxies show signs of being more strongly associated with disks rather than bulges.  Surprisingly, find that the blue (metal-poor) GCs can also show the same correlation.  If the metal-poor GCs are part of the early formation of the halo and built up through mergers, then these results support a picture where halo formation and merging occur anisotropically, and where the present day major axis is an indicator of the preferred merging axis.

1304.0931
Parameters of galactic disks at optical and NIR wavelengths
Gusev, Guslyakova, Khramtsova

Radial scales, central surface brightnesses, and colors of 404 disks of various types of galaxies analyzed.  ...  No sharp boundary in the properties of disks in lenticular, spiral, and irregular galaxies has been found; all parameters vary smoothly along the Hubble sequence.  Correlation between the central disk surface brightness and the total luminosity of the galaxy is observed.  Show that the dust concentrated in dust lines [lanes?] towards the spiral arms and bars do not influence the scale lengths ratio.


1304.0962
Black hole formation in the early universe
Latif et al

The direct collapse model provides a viable pathway of forming high-mass BHs at early cosmic times.  SMBH presence confirmed at z>6.  Gravitational collapse in atomic cooling haloes with virial temperatures T_vir>1e4K may lead to the formation of massive seed BHs in the presence of an intense BG UV flux.  Turbulence play a central role in regulating accretion and transporting angular momentum.  Present the highest resolution cosmological large-eddy simulations which track evolution of high-density regions on scales of 0.25 AU beyond the formation of the first peak, and study the impact of subgrid-scale turbulence.  Find: while fragmentation occasionally occurs, it does not prevent the growth of a central massive object resulting fro turbulent accretion and occasional mergers.  Central object reaches 1e3 Msun within 4 free-fall times, and expect further growth up to 1e6 Msun through accretion in about 1 million years.