Day 826

Tuesday.

1501.06709
Extremely metal-poor galaxies: the environment
Filho et al

Probe the environment in which extremely metal-poor dwarf galaxies (XMPs) reside, from bibliographical observational data and theoretical predictions.  Assess the HI component and its relation to the optical galaxy, the cosmic web type, the overdensity parameter and analyze the nearest galaxy neighbors.  The aim is to understand the role of interactions and cosmo accretion flows in the XMP observational properties, particularly the triggering and feeding of the SF.  Find that XMPs behave similarly to Blue Compact Dwarfs; they preferably populate low-density environments in the local Universe: ~60% occupy underdense regions, and ~75% reside in voids and sheets.  This is more extreme than the distribution of irregular galaxies, and in contrast to those regions preferred by elliptical galaxies (knots and filaments).  Further find results consistent with previous observations; while the environment does determine the fraction of a certain galaxy type, it does not determine the overall observational properties.  With the exception of 5 documented cases (4 sources with companions and one recent merger), XMPs do not generally show signatures of major mergers and interactions; find only one XMP with a companion galaxy within a distance of 100 kpc, and the HI gas in XMPs is typically well-behaved, demonstrating asymmetries mostly in the outskirts.  Conclude that metal-poor accretion flows may be driving the XMP evolution.  Such cosmo accretion could explain all the major XMP observational properties: isolation, lack of interaction/merger signatures, asymmetric optical morphology, large amounts of unsettled, metal-poor HI gas, metallicity inhomogeneities, and large sSF.
1501.06893
Mass calibration of galaxy clusters at redshift 0.1-1.0 using weak lensing in the Sloan Digital Sky Survey Stripe 82 Co-add
Wiesner et al

Present mass-richness relations found in SDSS Stripe 82 coadd.  Relations found using stacked WL shear observed in a large sample of galaxy clusters.  Presented in 4 redshift binds: [0.1, 0.4, 0.7, 1.0] and [0.1, 1.0].  Describe the sample of galaxy clusters and explain how these clusters were found using Moroni Tessellation cluster finder.  Fin an NFW profile to the stacked WL shear signal in z and richness bins in order to measure M200.  Describe several effects that can bias WL measurements, including photo-z bias, the effect of central BCG, halo miscentering, photometric z uncertainty and FG galaxy contamination.  Present mass-richness relations using richness measure N_VT with each of these effects considered separately as well as considered altogether.  Present values for the mass coefficient M200|20 and the power law slope alpha for power law fits to the mass and richness values in each of the z bins.  Find values of the mass coefficient of 8. 13, 27, and 8e13 Msun/h for each of the four z bins respectively.  Find values of the power law slope of 0.988, 0.96, 1.52 and 1.01 respectively.  Examine z evolution of the mass-richness relation.

1501.07064
The radial velocity profile of the filament galaxies in the vicinity of the Virgo cluster as a test of gravity
Lee, Kim, Rey

The radial velocities of the galaxies in the vicinity of a massive cluster shows deviation from the pure Hubble flow due to their gravitational interaction with the cluster.  According to a recent study of Falco+ with a high-res N-bondy sim based on GR< the radial velocity profile of the galaxies located at distances larger than 3x the viral raids of a neighbor cluster has a universal shape and could be reconstructed from direct observables provided that the galaxies are distributed along 1d filament.  Analyzing the narrow filamentary structure identified by Kim+ in the vicinity of the Virgo cluster from the NASA-Sloan-Atlas catalog, reconstruct the radial velocity profile of the Virgo filament galaxies and compare with the universal formula derived by Falco+.  It is found that unless the viral mass of the Virgo cluster exceeds 1e15 Msun/h, the universal formal fails to describe the reconstructed radial velocity profile whose peculiar velocity term turns out to decrease much less rapidly.  Speculating that the disagreement between the GR prediction and the observed radial velocity profile of the Virgo filament galaxies may be due to the presence of unscreened 5th force, suggest the radial velocity profile of the filament galaxies around the clusters as a powerful test of gravity on the cosmo scale.  

1501.07512
Halo Zeldovich model and perturbation theory: dark matter power spectrum and correlation function
Seljak, Vlah

Perturbation theory for DM clustering has received a lot of attention in recent years, but its convergence properties remain poorly justified and there is no successful model that works both for correlation function and for PW.  Present Halo Zeldovich approach combined with perturbation theory (HZPT), in which the standard perturbation theory at one loop order (SPT) at very low k is used, and connect it to a version of the halo model, for which the Zeldovich approximation plus a Pade expansion of a compensated one halo term is adopted.  This low k matching allows determination of the one halo term amplitude and z evolution, both of which are in excellent agreement with simulations, and approximately agree with the expected value from the halo model.  The Pade expansion approach of the one halo term added to Zeldovich approximation identified two typical halo scales averaged over the halo mass function, the halo radius scale of order 1Mpc/h, and the halo mass compensation scale of order 26 Mpc/h.  The model gives better than 1% accurate predictions for the correlation function above 5 Mpc/h at all redshifts, without any free parameters.  With 3 fitted Pade expansion coefficient the agreement in PS is good to a percent up to k~1h/Mpc, which can be improved to arbitrary k by adding higher order terms in Pade expansion.