Day 609

Monday.

1403.3393
A large catalog of accurate distances to molecular clouds from PS1 photometry
Schlafly, … Finkbeiner, Rix, Bell, … Kaiser, et al

Distance measurements to molecular clouds are important, but are often made separately for each cloud of interest,employing very different data and techniques.  Present a large, homogeneous catalog of distances to molecular clouds, most of which are of unprecedented accuracy.  Determine distances using optical photometry of stars along LoS towards these clouds, from PanSTARRS-1.  Simultaneously infer the reddenings and distances to these stars, tracking the full probability distribution function.  … Typical statistical uncertainties in the distances are 5%, though the systematic uncertainty stemming from the quality of the stellar models is about 10%.  The resulting catalog is the largest catalog of accurate, directly-measured distances to molecular clouds.  The distance estimates are generally consistent with available distance estimates from the literature, though in some cases the literature estimates are off any a factor of more than two.

1403.3395
Turbulence and cooling in cluster cores
Banerjee, Sharma

Study the interplay between turbulent heating, mixing, and radiative cooling in an idealized model of cool cluster cores.  AGN jets are expected to drive turbulence and heat cluster cores.  Cooling of the ICM and stirring by AGN jets are tightly coupled in a feedback loop.  Impose the feedback loop by balancing radiative cooling with turbulent heating.  In addition to heating the plasma, turbulence also mixes it, suppressing the formation of cold gas at small scales.  In this regard, the effect of turbulence is analogous to thermal conduction.  For uniform plasma in thermal balance (turbulent heating balancing radiative cooling), cold gas condenses only if the cooling time is shorter than the mixing time.  This condition requires the turbulent kinetic energy to be >~ the plasma internal energy; such high velocities in cool cores are ruled out by observations.  The results with realistic B-fields and thermal conduction are qualitatively similar to the hydrodynamic simulations.  Simulations where the runaway cooling of the cool core is prevented due to mixing with the hot ICM show cold gas even with subsonic turbulence, consistent with observations.  Thus, turbulent mixing is the likely mechanism via which AGN jets heat cluster cores.  The thermal instability growth rates observed in simulations with turbulence are consistent with the local thermal instability interpretation of cold gas in cluster cores.

1403.3402
Cosmology with galaxy clusters: systematic effects in the halo mass function
Paranjape

Investigate potential systematic effects in constraining the amplitude of primordial fluctuations sigma_8 arising from the choice of halo MF in the likelihood analysis of current and upcoming galaxy cluster surveys.  Study the widely used N-body sim of Tinker+08 and the recently proposed analytical model of Excursion Set Peaks (ESP).  First assess the relative bias between these prescriptions when constraining sigma8 by sampling the ESP MF to generate mock catalogs and using the T08 fit to analyze them, for various choices of survey selection threshold, mass definition and statistical priors.  To asses the level of absolute bias in each prescription, repeat the analysis on DM halo catalogs in N-body sims designed to mimic the mass distribution in the current data release of Planck SZ clusters.  This N-body analysis shows that using the T08 fit without accounting for the scatter introduced when converting between mass definitions (alternatively, the scatter induced by errors on the parameters of the fit) can systematically overestimate the value of sigma8 by as much as 2 sigma for current data, while analysis that account for this scatter should be close to unbiased in sigma8.  With an increase number of objects as expected in upcoming data releases, regardless of accounting for scatter, the T08 fit could over-estimate the value of sigma8 by 1.5 sigma.  The ESP MF leads to systematically more biased but comparable results.  A strength of the ESP model is its natural predication of a weak non-universality in the MF which closely tracks the one measured in simulations and described by the T08 fit.  Suggest that it might now be prudent to build new unbiased ESP-based fitting functions for use with the larger datasets of the near future.

1403.3411
Position-dependent power spectrum of the large-scale structure: a novel mouthed to measure the squeezed-limit bispectrum
Chiang, Wagner, Schmidt, Komatsu

The influence of LS density fluctuations on structure formation on small scales is described by the 3pt correlation function (bispectrum) in the "squeezed configurations," in which one wavenumber k3 is much smaller than the other two (k3<<k1~k2).  This bispectrum is generated by NL gravitational evolution and possibly also by inflationary physics.  In this paper, use this fact to show that the bispectrum in the squeezed configurations can be measured without employing 3pt function estimators.  Specifically, use the "position-dependent PS", i.e., the PS measured in smaller sub volumes of the survey (or simulation box), and correlate it with the mean overdensity of the corresponding sub volume.  This correlation directly measures an integral of the bispectrum dominated by the squeezed configurations.  Measuring this correlation is only slightly more complex than measuring the PS itself, and sidesteps the considerable complexity of the full bispectrum estimation.  Use cosmological N-body simulations of collision less particles with Gaussian IC to show that the measured correlation between the position-dependent PS and the log-wavelength overdensity agrees with the theoretical expectation.  The position-dependent PS thus provides a new, efficient, and promising way to measure the squeezed limit bisect rum from large-scale structure observations such as galaxy redshift surveys.

1403.3441
Extreme emission-line galaxies out to z$\sim$1 in zCOSMOS-20k.  I.  Sample and characterization of global properties
Amorin et al

EELGs are luminous and extremely compact at rest-frame UV wavelengths and include strong Lya emitters.  Morphologies and low surface brightness features strongly suggest recent or ongoing interactions.  As star-forming dwarfs in the local universe, EELGs are preferably found in relative isolation.  Almost 1/3 of them are found n spectroscopically confirmed loose pairs or triplets.  EELGs are galaxies caught in a transient and probably early period of their evolution, where they are efficiently building-up a significant fraction of their present-day stellar mass in an ongoing galaxy-wide starburst.  EELGs constitute and ideal benchmark for comparison studies between low-and high-z low-mass SF galaxies.

1403.3569
Cosmology from weak lensing of CMB
Namikawa

WL effect on CMB induces distortions in spatial pattern of CMB anisotropies, and statistical properties of CMB anisotropies become a weakly non-Gaussian field  First summarize the WL effect on the CMB in the presence of scalar, vector and tensor perturbations.  Then focus on the lensing effect on CMB statistics and methods to estimate deflection angles and there PS.  End by summarizing recent observational progress and future prospect.

1403.3614
The mass profile and dynamical status of the z~0.8 galaxy cluster LCDCS 0504
Guennou, … Limousin, … Clowe, … Ilbert, … Jullo, et al

Constraints on the mass distribution in high-z clusters of galaxies are not very strong.  Aim to constrain the mass profile M(r) and dynamical status of the z~0.8 LCDCS 0504 cluster of galaxies characterized by prominent giant gravitational arcs near its center.  Analysis is based on deep X-ray, optical, and IR imaging, as well as optical spectroscopy.  Model the mass distribution of the cluster with 3 different mass density profiles, whose parameters are constrained by the SL features of the inter cluster regions, by the X-ray emission from the ICM, and by the kinematics of 71 cluster members.  Obtain consistent M(r) determinations from 3 methods out to the cluster virial radius and beyond.  The mass profile inferred by the SL analysis in the central cluster region is slightly above, but still consistent with, the kinematics estimate.  On the other hand, the X-ray based M(r) is significantly below both the kinematics and SL estimates.  Theoretical predications from LCDM cosmology for the concentration-mass relation are in agreement with observational results, when taking into account the uncertainties in both the observational and theoretical estimates.  Here appears to be a central deficit in the intra-cluster bass mass fraction compared to nearby clusters.  Despite the relaxed appearance of this cluster, the determinations of its mass profile by different probes show substantial discrepancies, the origin of which remains to be determined.  The extension of a similar dynamical analysis to other clusters of the DAFT/FADA survey will shed light on the possible systematics that affect the determination of mass profiles of high-z clusters, possibly related to incomplete understanding of interacluster baryon physics.