Day 1329

Tuesday.

1710.10264
Probing the relic neutrinos properties with CMB, HST and galaxy clusters
Nunes, Bonilla

Investigate the observational constraints on the CNB (cosmic neutrino background) given by the extended LCDM scenario LCDM + N_eff + m_nu + c_eff^2 + c_vis^2 + xi_nu using the latest observational data from Planck CMB (temperature power spectrum, low-polarization and lensing reconstruction), BAO, the new recent local value of the Hubble constant from HST and information of the abundance of galaxy clusters (GC).  Study the constraints on the CNB background using CMB + BAO + HST data with and without the GC data.  Find Delta N_eff = 0.614±0.26 at 68% CL when the GC data are added in the analysis.  Do not find significant deviation for sound speed in the CNB rest frame.  Also analyze the particular case LCDM + Neff + m_nu + xi+nu with the observational data.  Within this scenario, find Delta N_eff=0.60±0.28 at 68%CL.  In both the scenarios, no mean deviations are found for the degeneracy parameter.


1710.10943
Photometric characterization of the Dark Energy Camera
Bernstein, et al

Characterize the variation in photometric response of the DECam across its 520 Mpix science array during 4 yrs of operation.  This variations are measured using high S/N aperture photometry of >1e7 stellar images in thousands of exposures of a few selected fields, with the telescope dithered to move the sources around the array.  A calibration procedure based on these results brings the RMS variation in aperture magnitudes of bright stars on cloudless nights down to 2-3 mmag, with <1 mmag of correlated photometric errors for stars separated by >=20".  On cloudless nights, any departures of the exposure zero points from a secant airmass low exceeding >1 mmag are plausibly attributable to spatial/temporal variations in aperture corrections.  These variations can be inferred and corrected by measuring the fraction of stellar light in an annulus between 6" and 8" in diameter.  Key elements of this calibration include: correction of amplifier nonlinearities; distinguishing pixel-area variations and stray light from quantum-efficiency variations in the flat fields; field-dependent color corrections; and the use of an aperture-correction proxy.   The DECam response pattern across the 2-degree field drifts over months by up to ±7 mmag, in a nearly-wavelength-independent low-order pattern.  Find no fundamental barrier to pushing global photometric calibrations toward mmag accuracy.


1710.10958
Comparing simulations and test data of a radiation damaged charge-couple device for the Euclid mission
Skottfelt, et al

The VIS instrument on board the Euclid mission is a WL experiment that depends on very precise shape measurements of distant galaxies obtained by a large CCD array.  Due to the harsh radiative environment outside the Earth's atmosphere, it is anticipated that the CCDs over the mission lifetime will be degraded to an extent that these measurements will only be possible through the correction of radiation damage effects.  Create a MC model that simulates the physical processes taking place when transferring signal through a radiation-damaged CCD.  The software is based on Shockley-Read-Hall theory, and is made to mimic the physical properties in the CCD as closely as possible.  The code runs on a single electrode level and takes 3D trap position, potential structure of the pixel, and multi-level clocking into account.  A key element of the model is that it also takes device specific simulations of electron density as a direct input, thereby avoiding to make any analytical assumptions about the size and density of the charge cloud.  This paper illustrates how test data and simulated data can be compared in order to further the understanding of the positions and properties of the individual radiation-induced traps.


1710.011100
The Next Generation Transit Survey (NGTS)
Wheatley, et al

NGTS: a ground-based project searching for transiting exoplanets orbiting bright stars.  Higher photometric precision, and hence find smaller planets than have previously been detected from the ground.  Also operates in red light, maximizing sensitivity to late K and early M dwarf stars.  Survey specs: photometric precision of 0.1% in red light over an instantaneous FoV of 100 sq. degs; enables detection of Neptune-sized exoplanets around Sun-like stars and super-Earths around M dwarfs.  The survey is carried out with a purpose-built facility at Cerro Paranal, Chile, which is the premier site of ESO.  An array of twelve 20cm f/2.8 telescopes fitted with back-illuminated deep-depletion CCD cameras are used to survey fields intensively at intermediate Galactic latitudes.  The instrument is also ideally suited to ground-based photometric follow-up of exoplanet candidates from space telescopes such as TESS, Gaia and PLATO. Present observations that combine precise auto guiding and the superb observing conditions at Paranal to provide routine photometric precision of 0.1% in 1 hr for stars with I-band magnitudes brighter than 13.  Describe the instrument and data analysis methods as well as the status of the survey, which achieved first light in 2015 and began full survey operations in 2016.  NGTS data will be made publicly available through the ESO archive.