Day 997

Tuesday.


1510.07040
A multiwavelength study of tadpole galaxies in the Hubble ultra deep field
Straughn, et al

Multiwavelength dat are essential in order to provide a complete picture of galaxy evolution and to inform studies of galaxies' morphological properties across cosmic time.  Present realists of a multi wavelength investigation of the morphologies of "tadpole" galaxies at intermediate redshift (0.314<z<3.175) in the HUDF.  These galaxies were previeously selected from deep HST F774W data based on their distinct asymmetric knot-plug-tail morphologies (Sraughn+2006).  Use deep WFC3 NIR imaging in addition to the HST optical data in order to study the rest-frame UV/optical morphologies of these galaxies across the redshift range 0.3<z<3.2.  This study reveals that the majority of these galaxies do retain the general asymmetric morphology in the rest-frame optical over this redshift range, if not the district "tadpole" shape.  The average stellar mass of tadpole galaxies is lower than field galaxies, with the effect being slightly greater at higher redshift within the errors.  Estimated from SED fits, the average age of tadpole galaxies is younger than field galaxies in the lower redshift bin, and the average metallicity is lower (whereas the sSFR for tadpoles is roughly the same as field galaxies across the redshift range probed here).  These average effects combined support the conclusion that this subset of galaxies is in an active phase of assembly, either late-stage merging or cold gas accretion causing localized clumpy star-formation.


1510.07574
A daytime measurement of the lunar contribution to the night sky brightness in LSST's ugrizy bands-- initial results
Coughlin, Stubbs, Claver

Report measurements from which the spatial structure of the lunar contribution to nigh sky brightness is determined.  Taken at the LSST site on Cerro Pachon in Chile.  Use an array of six photodiodes with filters that approximate the LSST's ugriz and y bands.  Use the sun as a proxy for the moon, and measure sky brightness as a function of zenith angle of the point on sky, zenith angle of the sun, and angular distance between the sun and the point on sky.  Make a correction for the difference between the illumination spectrum of the sun and the moon.  Since scattered sunlight totally dominates the daytime sky brightness, this technique allows clean determination of the contribution to the (cloudless) night sky from backscattered moonlight, without contamination from other sources of night sky brightness.  Estimate the uncertainty in the relative lunar night sky brightness vs. zenith and lunar angle to be 10%.  This information is useful in planning the optimal execution of the LSST survey, and perhaps for other astronomical observations as well.  Although the primary objective is to map out the angular structure and spectrum of the scattered light form the atmosphere and particulates, also make an estimate of the expected number of scattered lunar photons per pixel per second in LSST, and find values that are in overall agreement with previous estimates.