Day 581

Tuesday.  Wednesday.

1401.4065
Cosmological parameter uncertainties from SALT-II Type Ia supernova light curve models
Mosher, … Sako, … et al

Use simulated SN Ia samples to validate cosmology analysis using SALT-II light curve model.  Validation includes residuals from the light curve training process, systematic biases in SN Ia distance measurements, and the bias in the DE EoS parameter w.  Make similar dataset to SNLS3.  Vary input spectral model, the model of intrinsic scatter, and the smoothing parameters during SALT-II model training.  Biases indistinguishable from each other within uncertainty; average bias on w is -0.014pm0.007.

1401.4094
Herschel-ATLAS/GAMA: SDSS cross-correlation induced by weak lensing
González-Nuevo et al

H-ATLAS z>1.5 galaxies and SDSS/GAMA galaxies at 0.2<z<0.6 has 10 sigma spatial correlation; this is explained by weak lensing (sub-mm galaxies amplified by FG structures, mu<2).  Sims show measured amplitude and range of angular scales of signal are larger than can be accounted for GGL (weak lensing).  For scales <2 arcmin, signal can be reproduced if SDSS/GAMA galaxies act as signposts of galaxy groups/clusters with halo masses of range 1e13.2-14.5 Msun.  The signal detected on large scales appears to reflect the clustering of such halos.  Make use of simulations to show that lensing can induce an apparent clustering of randomly distributed BG galaxies, but the amplitude of the corresponding angular correlation function is at least a factor of 10 per than observed between H-ATLAS and SDSS/GAMA galaxies; the gravitational magnification effects on counts of sub-mm sources are nevertheless dominated by GGL (strong lensing).

1401.4169
Implementation of robust image artifact removal in SWarp through clipped mean stacking
Gruen, Seitz, Bernstein

Implement and algorithm for detecting and removing artifacts from astronomical images by means of outlier rejection during stacking---addresses both CR (small and significant artifacts) and, by applying a filtering technique to generate single frame masks, ghosts of bright stars (larger area but lower SB features).  In contrast to the common method of building a median stack, the clipped or outlier-filtered mean stacked PSF is a linear combination of the single frame PSFs as long as the latter are moderately homogeneous, a property of great importance for WL shape measurement or model fitting photometry.  In addition, it has superior noise properties, allowing a significant reduction in exposure time compared to median stacking.  Make publicly available a modified version of SWarp that implements clipped mean stacking and SW to generate single frame masks from the list of outlier pixels.

1401.4170
Detection of ultraviolet halos around highly inclined galaxies
Hodges-Kluck, Bregman

Discovery of diffuse UV around late-type galaxies out to 5-20 kpc from the mid plane using Swift and GALEX images.  Consistent with the stellar outskirts in the early-type galaxies, but not in the late-type galaxies, where the emission is quite blue and consistent with a reflection nebula powered by light escaping from the galaxy and scattering off dust in the halo.  Fitting a simple reflection nebula model to the halo SEDs points to SMC-type dust (lacking a UV bump), and the halo colors and luminosities are consistent with this scenario.  Results agree with expectations from halo dust discovered (at larger radii) in extinction by Menard+ (2010) to within a few kpc of the disk and imply a comparable amount of hot and cold gas in galaxy halos (a few e8 Msun within 20 kpc) if the dust resides primarily in Mg II absorbers.

1401.4182
An eccentricity-mass relation for galaxies from tidally disrupting satellites
Chakrabarti et al

Infer the past orbit of Sgr dwarf galaxy by integrating backwards from observed position and proper motions, including dynamical friction effects.  Show that there is a power-law relation between e of Sgr's orbit and the mass of MW (M_T) in the limit of no dynamical friction.  At fixed MW mass, the dynamical friction term increases the mean eccentricity of the orbit and lowers the spread in eccentricities in proportion to the mass of Sgr dwarf.  Explore the implications of various observational constraints on Sgr's epicenter on the e-M relation.  Assuming Belokurov+2014's observation represents farthest point of Sgr's stream, then MW masses in excess of 2e12 Msun are excluded for M_Sgr >~ 1e10 Msun.  Deeper observations of Sgr's tidal debris, from upcoming surveys such as GAIA, will allow better measurement of MW mass and the Sgr dwarf.