Day 850

Tuesday.

1503.04271
Gravitational microlensing I: a unique astrophysical tool
Rahvar

Review article.  Most frequent microlensing events are single-lens events, historically used for searching DM in the form of compact astrophysical halo objects in the Galactic halo.  Discuss the degeneracy problem in the parameters of lens and perturbation effects that can partially break the degeneracy between the lens parameters.  Astrophysical applications of microlensing: in stellar physics, by probing the surface of source stars in the high magnification microlensing events.  The astrometric and polarimetric observations will be complimentary for probing the atmosphere and stellar spots on the surface of source stars.  Future projects: space-based telescopes for parallax and astrometry observations of microlensing events.  Expect to produce a complete stellar and remnant mass function and study the structure of Galaxy in term of distribution of stars along the LoS towards the center of the Galaxy.


1503.04321
Co-evolution of BCGs and ICL using CLASH
Burke, Hilton, Collins

Examine the stellar mass assembly in galaxy cluster cores using data from CLASH.  Measure the growth of BCG stellar mass, the fraction of the total cluster light which is in the ICL and the numbers of mergers that occur in the BCG over the z range of the sample, 0.18<z<0.90.  Find that BCGs grow in stellar mass by a factor of 14 on average from accretion of their companions, and this growth is reduced to a factor of 1.2 assuming 50% of the accreted stellar mass becomes ICL, in line with the predictions of simulations.  Find that the ICL shows significant growth over this same range, growing by a factor of 4-5 in its contribution to the total cluster light.  This result is in line with the previous findings for ICL at higher z, however the measured growth is somewhat steeper than is predicted by simulations of ICL assembly. Find high mass companions and hence major merging (mergers with objects of masses >1/2 of the BCG) to be very rare for the sample.  Conclude that minor mergers (mergers with objects with masses <1/2 of the BCG) are the dominant process for stellar mass assembly at low z, with the majority of the stellar mass from interactions ending up contributing to the ICL rather than building up the BCG.  From a rough estimate of the stellar mass growth of the ICL, also conclude that the majority of the ICL stars must come from galaxies which fall from outsize of the core of the cluster, as is predicted by simulations.  The growth of the ICL appears to be the major evolution even in galaxy cluster acres during the second half the lifetime of the universe.


1503.04324
The importance of the cosmic web and halo substructure for power spectra
Pace, Manera, Bacon, Crittenden, Percival

Study the relevance of the cosmic web and substructures on the matter and lensing PS measured from halo mock catalogues extracted from N-body sims.  Since N-body sims are computationally expensive, it is common to use faster methods that approximate the DM field as a set of haloes.  In this approximation, replace mass concentrations in sims by a spherically symmetric NFW halo density profile.  Also consider the full mass field as the sum of two distinct fields: DM halos (M>9e12 Msun/h) and particles not included into halos.  Mock haloes reproduce well the matter PS, but underestimate the lensing PS on large and small scales.  For sources at z_s=1 the lensing PS is underestimated by up to 40% at ell~1e4 with respect to the simulated haloes.  The large scale effect can be alleviated by combining the mock catalogue with the DM distribution outside the haloes.  In addition, the evaluate the contribution of substructures, smear out the intrahalo substructures in a N-body sim while keeping the halo density profiles unchanged.  For the matter PS the effect of this smoothing is only of the order of 5%, but for lensing substructures are much more important, for ell~1e4 the internal structures contribute 30% of the total spectrum.  These findings have important implications in the way mock catalogues have to be created, suggesting that some approximate methods currently used for galaxy surveys will be inadequate for future WL surveys.


1503.04412
Central mass profiles of the nearby cool-core galaxy clusters Hydra A and A478
Okabe, Umetsu, ... et al

SLstudy of Hydra A (z=0.0538) and A478 (z-0.0881), of which BCGs host powerful AGNs.  For each cluster, observed tangential shear profile is well described either by NFW or a two-component model including the BCG as an unresolved point mass.  For A478, combine WL and stellar photometry.  Find that the choice of IMFs can introduce a factor of 2 uncertainty in BCG mass, where as the host halo mass is well constrained by data.  For Hydra A, joint analysis of Wl and stellar kinematics, which allows constraint of the central ass profile without assuming specific IMFs.  Find that the central mass profile (r<300 kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disk component, X-ray hydrostatic total mass emits, and the central stellar mass estimated based on the Saltpeter IMF.  The observed DM fractions around the BCGs for the two clusters are found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as the AGN feedback and/or dissipationless mergers.


1503.04451
Giant comets and mass extinctions of life
Napier

Find a strong correlation between bombardment episodes and major biostratigraphic and geological boundaries, and propose that episodes of extinction are most effectively driven by prolonged encounters with meteoroid streams during bombardment episodes.  Possible mechanisms are discussed.


1503.04650
Towards accurate rescaling of a halo mass function
Yankelevich, Pilipenko

Propose a new method of calculating DM halo MF based on the rescaling of a MF measured in sims.  Tests show that the accuracy almost linearly depends on the difference f the cosmo parameters and amounts to few percent the case of WMAP5 and PLANCK parameters.