Tuesday. And neither on Monday.
1207.3078
Aspect ratio dependence of the free-fall time for non-spherical symmetries
Pon et al
* homologous: having the same relation, relative position, or structure.
Investigate the collapse of non-spherical substructures (sheets and filaments) in molecular clouds. Collapse homologously in their interiors, but edge effect causes their edges to be preferentially accelerated. Compute homologous collapse timescales of interiors of uniform-density, self-gravitating filaments; homologous collapse timescale scales linearly with the aspect ratio. Edge-driven collapse in a filament is shown to have square root dependence on the aspect ratio. Lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. SFR estimates based on gas densities can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.
1207.3080
The current status of galaxy formation
Silk, Mamon
As the title says. 30 pages, 32 figures, 192 references.
1207.3081
The detection of interstellar lithium n a low-metallicity galaxy
Howk, Lehner, Fields, Mathews
The BBN predicted primordial 7Li abundance is 4x that measured in atmospheres of Galactic halo stars. This discrepancy: caused by modification of surface Li abundance, or by physics beyond the SM that impacts early nucleosynthesis; but Li abundance in low-metallicity gas provides an alternative constraint, not susceptible to the in situ modification that affect stellar atmospheres. Measure 7Li in SMC (1/4 solar metallcity galaxy), find nearly equal to BBN predictions (constrains amount of post-BBN enrichment of the gas by stellar and CR nucleosynthesis. Need extremely fine-tuned depletion of stellar Li with metallicity. Mostly consistent with standard BBN (but also non-standard BBN).
1207.3189
The Dark Energy Survey Data processing and calibration system
Mohr, ..., Yanny, et al, the DES collaboration
DES: 5k degsq grizY survey to 24th mag (10 sigma) -- photometry 10x fainter than SDSS. 3 degsq DECam, CTIO Blanco 4m upgrade, HPC (high performance computing) enabled data manage system (DESDM). DESDM used for processing, calibrating and serving the DES data. Data volume ~2 PB (high), automated processing and quality control system. Image detrending [?] and photometric calibration codes developed; survey astrometric calibration, coalition and cataloging rely on AstrOmatic code extensions (incl. PSF molding, PSF homogenization, PSF corrected model fitting cataloging, joint model fitting across multiple input images. HPC systems in US and Germany. Tested on BCS. Used for DECam commissioning.
1207.3235
Probing non-Gaussianities in the CMB on an incomplete sky using surrogates
Rossmanith et al
Generate surrogates by Fourier-based methods for an incomplete data set. Non-Gaussianities and hemispherical asymmetries in the CMB as identified in several former investigations can still be detected even when the complete Galactic plane (|b| < 30 deg) is removed. Galactic plane cannot be dominant source for these anomalies. Results point towards a violation of statistical isotropy [is that good or bad?].
1207.3260
The importance of galaxy interactions in triggering type II quasar activity
Bessiere et al
Results consistent with the idea that galaxy interaction plays an important role in the triggering of quasar activity. Looked at 20 SDSS type II quasars with 0.3<z<0.41 and [OIII] emission line Lum > 1e8.5 Lsun. Use these Gemini GMOS-S images for evidence of interaction (tails, shells, double nuclei).
1207.3326
Measuring gravitational lensing of the cosmic microwave background using cross-correlation with large scale structure
Feng, ... Zahn et al
Cross-correlate gravitational lensing map from WMAP with radio galaxy distribution from NVSS by using a quadratic estimator technique. Use full covariance matrix to filter the data and calculate the cross-power spectra for the lensing-galaxy correlation. Statistical detection significance of >3 sigma.
1207.3347
Spectroscopic failures in photometric redshift calibration: cosmological biases and survey requirements
Cunha, Hurterer, Lin, Busha, Wechsler
What happens if there are spectroscopic failures when calibrating photo-z? N-body spectro-photometric simulations : investigate impact of incompleteness and incorrect redshifts in spec-z surveys to photometric redshift training and calibration; and resulting effects on cosmological parameter estimation from WL shear correlations. Modeled after DES. Principal systematic errors: spectra follow-up encounters incompleteness, or wrong redshifts. Neural network-based approach can effectively describe the spec-z incompleteness in terms of the galaxy colors, so spec selection can be applied to photometric sample. Spec incompleteness yield no appreciable biases to cosmology, although statistical constraints degrade because the photometric survey has to be culled to match the spec selection. Wrong redshifts have a more severe impact: cosmo bias are intolerable if more than a percent of the spec-z's are incorrect. Incorrect redshifts can also degrade the accuracy of training-set based photo-z estimators [duh]. Main problem: difficulty of obtaining redshifts (spec or photo) for z>1.3 objects. Discuss several approaches for reducing cosmo bias, in particular photo-z error estimators can reduce biases appreciably.
[Mon **/40]
1207.3354
Binary black hole mergers in magnetized disks: simulations in full general relativity
Farris et al
Fully GR MHD simulations of equal-mass BH-BH binary in a magnetized, circumbinary accretion disk. Prior to decoupling, competition between tidal torques and effective viscous torques due to MHD turbulence depletes the disk interior to the binary orbit; but it also induces a two-stream accretion flow and mildly relativistic polar outflows from the BHs. Following decoupling, the accretion rate is reduced, while the EM luminosities peak near merger due to shock heating. This is a preliminary run.
1207.3382
The chemical composition of ultra compact dwarf galaxies in the Virgo and Fornax clusters
Francis et al
Spectro observations of UCD galaxies (stellar population study) on Geminis. Ages, metallicities and abundances from Lick line-strength/direct spectral fitting technique. UCDs are old (10 Gyr) and metal-rich [Fe/H]=-0.8. Alpha-element abundances are super-Solar. Test hypothesis that UCDs are form red by tidal disruption of present-day nucleated dwarf elliptical galaxies. Data not consistent with this hypothesis (both age and abundances significantly higher than dwarf galaxy nuclei). They are more consistent with globular star clusters, but at higher mean metallicity. UCDs display a wide range of metallicity spanning the full range of both globular clusters and dwarf galaxy nuclei. Confirm most UCDs have high metallicity for their luminosity, significantly above the metallicity-luminosity relation of early-type galaxies. No significant difference in the mean ages or the mean metallicities in the UCD populations in the two clusters.
1207.3452
Simulations of barred galaxies in triaxial dark matter haloes: the effects of gas
Machado et al
Bars are generally weaker for larger initial gas content and for larger halo triaxiality. The presence of gas is a more efficient factor in inhibiting the formation of a strong bar than halo triaxiality is.
1207.3460
PS2: managing the next step in the Pan-STARRS wide field survey system
Burgett
Lessons learn in management on PS1, and using this for PS2 (technical development, financial and schedule planning, and critical path and risk management; status and schedule).
1207.3534
Atmospheric considerations for CTA site search using global models
Louedec, Will
Cherenkov Telescope Array (CTA): the next HE gamma-ray observatory, using atmosphere as a giant calorimeter. Choose potential sites based on atmospheric conditions: cloud cover, wind speed, and the backward trajectories of air masses traveling above the sites and directly linked to the aerosol concentrations. Namibian site favored.
1207.3535
Origin of atmospheric aerosols at the Pierre Auger Observatory using backward trajectory of air masses
Louedec, for PAC.
Calorimetric measurements of extensive air showers from CRs performed with a fluorescence detector. Monitor atmosphere, air mass trajectories. Compare backward trajectories to aerosol [?] concentration values.
1207.3579
Cosmic connections: from cosmic rays to gamma rays, to cosmic backgrounds and magnetic fields
Kusenko
Possible contribution of transient galactic sources (GRB and hyper nova in MW) to the observed flux of UHE CR nuclei. Measurement of IG B-fields based on spectra of distant sources; hard spectra of distant blazers.
1207.3669
Experiments on centimeter-sized dust aggregates and their implications for planetesimal formation
Meisner et al
Dust aggregates: first macroscopic bodies in protoplanetary disks. Experiments forming dust aggregates from micron-sized quartz grains. Collision experiments: well-defined upper-filling factor of 0.31. Increase projectile mass by 100x, compared to earlier study. Dust-aggregate can retain its highly porous core if dense shell forms. Mechanical properties of cm-sized dust samples (filling factor 0.34-0.5): Tensile strength is 1 to 6 kPa. Sound speed is 80-140 m/s, Young's modulus derived from sound speed. Compression strengths, flow functions measured. Provides basic data for future simulations. Explains the specific collisional outcomes; in general support a scenario where collisional growth of planetesimals is possible.
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