Day 755

Wednesday.

1409.8297
The effect of baryons on the inner density profiles of rich clusters
Schaller, Frenk, Bower, et al

Use the "Evolution and assembly of galaxies and their environment" (EAGLE) cosmo sim to investigate the effect of baryons on the density profiles of rich galaxy clusters.  Focus on the 6 most massive EAGLE clusters (>1e14Msun) which can be compared with a recent analysis of 7 real clusters by Newman+.  The central BCGs in EAGLE have steep stellar density profiles rho_*(r)~r^-3.  Stars dominate the mass density for r<10 kpc, and, as a result, the total mass density profiles are steeper than the NFW profile.  However, the DM halo itself closely follows the NFW form at all resolved radii (r>3.0 kpc).  The EAGLE BCGs have similar surface brightness and LoS velocity dispersion profiles as the BCGs observed.  The central slopes of the total mass profiles are also consistent with the observed clusters.  However, after subtracting the contribution of the stars to the central density, Observation find significantly shallower slopes than NFW, in contradiction with EAGLE results.  Discuss possible reasons for the discrepancy, such as differences in the mass of the simulated and observed clusters or orientation biases in the observed sample.  Conclude that an inconsistency between the kinematical model adopted by observation for their BCGs, which assumes isotropic stellar orbits, and the kinematical structure of the EAGLE BCGs, in which the orbital stellar anisotropy varies with radius and tends to be radial biased, could explain at least par of the discrepancy.

1409.8562
Extending the supernova Hubble diagram to z~1.5 with the Euclid space mission
Astier et al

Forecast DE constraints that could be obtained from SNIa at high-z with Euclid.  Simulate a 3-prong SN survey: z<0.35 (8000 SNe), 0.2<z<0.95 (8800 SNe), and 0.75<z<1.55 (1700 SNe) samples.  The nearby and intermediate surveys are assumed to be conducted from the ground, while the high-z is a joint ground- and space-based survey.  This latter survey, the DE SN IR experiment (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing program.  Simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints.  Account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the SN model used to fit the SN light curves. Using conservative assumptions and 1d geometric Planck prior, find that the ensemble of surveys would yield competitive constraints: a constant EoS parameter can be constrained to sigma(w)=0.022, and DETF FoM of 203 is found for a 2-param EoS.  Simulations thus indicate that Euclid can bring a significant contribution to a purely geometrical cosmo constraint by extending a high-quality SN Hubble diagram to z~1.5.  Also present other science topics enabled by the DESIRE Euclid observations.