Day 570

Monday.

1312.3944
Discovery of a transparent sightline at {\rho} < 20 kpc from an interacting pair of galaxies
Johnson … Prochaska, et al

Very low HI column density and little absorption towards a pair of interacting galaxies, suggesting that cool gas reservoir of the galaxies have been significantly depleted by the galaxy interaction; underscore the potential impact of galaxy interactions on the gaseous halos around galaxies.

1312.3948
Compressed convolution
Elsner, Wandelt

A technique to convolve a given data set with a large number of non-orthogonal kernels; drastically reduces the effective number of computations.  For a CMB experiment with O(10,000) detectors with similar beam properties, demonstrate that the algorithm can decrease the costs of beam convolution by two to three orders of magnitude with negligible loss of accuracy.  …

1312.3950
X-ray properties of K-selected galaxies at 0.5<z<2.0: investigating trends with stellar mass, redshift and spectral type
Jones, Kriek, van Dokkum, … et al

~3500 galaxies at 0.5<z<2.0 in the COSMOS field; binned in SED type (32), redshifts and stellar mass, and perform an X-ray stacking analysis using the Chandra-COSMOS data.  Find: bolometric X-ray luminosity increases with stellar mass, and at similar mass and SED higher at larger redshifts.  Younger SED types tend to have higher X-ray luminosity, but the scatter in the relation is large.  For blue galaxies, XRBinaries can almost fully account for the observed emission, while for older galaxies, AGN or hot gas dominate the measured X-ray flux.  After correcting for XRBs, the X-ray luminosity is still slightly higher in younger galaxies, although this correlation is not significant.  AGN appear to be a larger component of galaxy X-ray luminosity at earlier times, as the hardness ratio increases with redshift.  Together with the slight increase in X-ray luminosity this may indicate more obscured AGNs or higher accretion rates at earlier times.

1312.3963
Optical selection of quasars: SDSS and LSST
Ivezic, et al

Over the last decade, quasar sample size has increased from O(1e3) to O(1e5), thanks mostly to SDSS imaging and spectroscopic surveys.  LSST will provide hundreds of detections per object for a sample of >1e7 quasars with up to z~7.  Briefly review optical quasar select techniques, with emphasis on methods based on colors, variability properties and astrometric behavior.

1312.3966
Optical variability of quasars: a damped random walk
Ivezic, MacLeod

A damped random walk model provides a satisfactory statistical description of observed quasar variability in the optical, for rest-fram timescales from 5 days to 2000 days.  The best-fit timescale and asymptotic variability amplitude scale with luminosity, M_BH, and rest wavelength, and appear independent of redshift.  In addition to providing insights into the physics of quasar variability, the best-fit model parameters can be used to efficiently separate quasars from stars in imaging surveys with adequate long-term multi-epoch data, such as expected from LSST.  

1312.3996
CANFAR+Skytree: A cloud computing and data mining system for astronomy
Ball

CANFAR = Canadian Astronomy Data Centre cloud computing system; Skytree = machine learning software.  500 processor cores available.  Storage by VOSpace protocol.  World's first cloud computing system for data mining in astronomy.

1312.4214
Peculiar velocities in redshift space: formalism, N-body simulations and perturbation theory
Okumura, Seljak, Vlah, Desjacques

Direct measurements of peculiar velocities of galaxies and clusters of galaxies can in principle provide explicit information on the 3d mass distribution, but this information is modulated by the fact that velocity field is sampled at galaxy positions, and is thus probing galaxy momentum.  Derive expressions for the cross PS between the density and momentum field and the auto spectrum of the momentum field in redshift space, by extending the distribution function method to these statistics.  The resulting momentum cross and auto PS in z space are expressed as infinite sums over velocity moment correlators in real space, as is the case for the density PS in z space.  Compare the predictions of the velocity statistics to those measured from N-body simulations for both DM and halos.  Find that in redshift space in ear theory predictions of the density-momentum cross PS as well as for the momentum auto spectrum fail to predict the N-body result at very large scales.  On the other hand, the NL PT prediction dramatically improves the accuracy.  Also present the same analysis in configuration space, computing the z-space pairwise mean infall velocities and velocity correlation function and compare to NL PT.

1312.4329
The ginger-shaped astroid 4179 Toutatis: new observations from a successful flyby of Chang'e-2
Huang et al

As the title says.  Neat picture of a ginger-shaped asteroid.

1312.4403
Mapping dark matter in the gamma-ray sky with galaxy catalogs
Ando, Benoit-Lévy, Komatsu

Cross-correlating gamma-ray maps with locations of galaxies in the low-z Universe vastly increases sensitivity to signatures of annihilation of DM particles.  Low-z galaxies are ideal targets, as the largest contribution to anisotropy in the gamma-ray sky from annihilation comes from z<0.1, where minimum contributions from astrophysical sources such as blazers are expected.  Cross-correlating the five-year data of Fermi-LAT with the redshift catalog of the 2MASS survey can detect gamma rays from annihilation if DM has the canonical annihilation cross section and its mass is smaller than about 100 GeV.

1312.4418
Star formation and environmental quenching of GEEC2 group galaxies at z~1
Mok, … Finoguenov, Tanaka, et al

Galaxy groups at 0.8<z<1: Observed quiescent / SF / intermediate population fractions are best matched with at model that includes a delay that is proportional to the dynamical time and a rapid quenching timescale (~0.25 Gyr), but this model predicts intermediate galaxies Hdelta strength higher than observed.  Using stellar synthesis models, test other scenarios (e.g., residual SF).  If environment quenching plays a roll, then work suggests that only a fraction of intermediate galaxies may be undergoing this transition, and that quenching occurs quite rapidly in satellite galaxies.

1312.4450
How many ore-bearing asteroids?
Elvis

Ore == commercially profitable material, e.g., platinum group metals and water.  If Ni-Fe asteroids only, then 1% of NEOs are rich in PGMs; for large (>100m diameter) and slow (delta-v,4.5 km/s) asteroids, only ~1 in 2000 NEOs.  Total population of ~100m asteroids with value of >=1B USD are ~10 (conservative value, highly uncertain).  Water-ore for utilization in space---likely found in ~1/1100 NEOs.

1312.4525
Detection of thermal SZ -- CMB lensing cross-correlation in Planck nominal mission data
Hill, Spergel

tSZ-CMB lensing cross-correlation is a unique probe of the physics of intracluster gas in high-z, low-mass groups and clusters.  Report first detection at 6.2 sigma, from Planck.  Sensitive to combination of sigma8 and Omega_m.  Detection is a direct confirmation that hot, ionized gas traces the DM distribution over a wide range of scales in the universe (~0.1-50 Mpc/h).