Day 951

Monday.


1508.05098
Supermassive black hole seed formation at high redshifts: long-term evolution of the direct collapse
Shlosman, CHoi, Begelman, Nagamine

Use cosmo AMR code Enzo zoom-in sims to study the long term evolution of the collapsing gas within DM haloes at high redshifts.  This direct collapse process is a leading candidate for rapid formation of SMBH seeds at high z.  To circumvent the Courant condition at small radii, use the sink particle method, and focus on the evolution on scales ~0.01-10pc.  The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc, and with no detected fragmentation.  The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level.  Their mass never exceeds ~1e3 Mo, with the sole exception of the central seed which grows dramatically to ~2e6 Mo in ~2 Myr, confirming the feasibility of this path to the SMBH.  The time variability of angular momentum axis in the accreted gas results in the formation of two misaligned disks -- a small inner disk, and a more massive, outer disk which is inclined by ~45deg to the inner disk. The self-gravity of these disks is heavily diluted -- both disks lie within the Roche limit of the central seed.  While the inner disk is geometrically thin and weakly asymmetric, the outer disk flares due to turbulent motions as a result of the massive inflow along a pair of penetrating filaments.  The geometry of inflow via filaments determine the dominant and secondary Fourier modes in this disk -- these modes have a non-self-gravitational origin.  Do not confirm that m=1 is a principal mode that derive the inflow in the presence of a central massive object.  While the positions of the disks depend on the scale chosen to break the self-similar collapse, the overall configuration appears to be generic, and is expected to form when the central seed becomes sufficiently massive.


1508.05308
Statistical uncertainties and systematic errors in weak lensing mass estimates of galaxy clusters
Köhlinger, Hoekstra, Eriksen

Upcoming and ongoing large area weak lensing surveys will also discover large samples of galaxy clusters.  Accurate and precise masses of galaxy clusters are of major importance for cosmology, for example, in establishing well calibrated observational halo mass functions for comparison with cosmo predictions.  Investigate the level of statistical uncertainties and sources of systematic errors expected for WL mass estimates.  Future surveys that will cover large areas on the sky, such as Euclid or LSST and to lesser extent DES, will provide the largest weak lensing cluster samples with the lowest level of statistical noise regarding ensembles of galaxy clusters.  However, the expected low level of statistical uncertainties requires scrutinizing various sources of systematic errors. In particular, investigate the bias due to miscentering, i.e., the displacement between any observationally defined cluster centre and the true minimum of its gravitational potential.  The impact of this bias might be significant with respect to the statistical uncertainties.  However, complementary future missions such as eROSITA will allow definition of stringent priors on miscenetring parameters which will mitigate this bias significantly.