Day 1239

Wednesday.

1704.00729
Quenching of supermassive black hold growth around the apparent maximum mass
Ichikawa, Inayoshi

Recent quasar surveys have revealed that SMBHs rarely exceed a mass of M_BH ~ a few 1e10 Msun during the entire cosmic history.  It has been argued that quenching of the BH growth is caused by a transition of a nuclear accretion disk into an advection dominated accretion flow, with which strong outlaws and/or jets are likely to be associated.  Investigate a relation between the maximum mass of SMBHs and the radio-loudness of quasars with a well-defined sample of 1e5 quasars at 0<z<2, obtained from SDSS DR7 catalog.  Find that the number fraction of the radio-loud (RL) quasars increases above a threshold of M_BH~1e9.5 Msun, independent of their redshifts.  Moreover, the number fraction of RL quasars with lower Eddington ratios (out of the whole RL quasars), indicating lower accretion rates, increases above the critical BH mass.  These observational trends can be natural consequences of the proposed scenario of suppressing BH growth around the apparent maximum mass of ~1e10 Msun.  The ongoing VLS sky survey on radio will allow estimation of the exact number fraction of RL quasars more precisely, which gives further insights to understand quenching processes for BH growth.


1704.00920
Testing approximate predictions of displacements of cosmological dark matter halos
Munari, Monaco, Koda, Kithara, Sefusatti, Borgani

Present a test to quantify how well some approximate methods, designed to reproduce the mildly non-linear evolution of perturbations, are able to reproduce the clustering of DM haloes once the grouping of particles into haloes is defined and kept fixed.  The following methods have been considered: Lagrangian Perturbation Theory (LPT) up to a 3rd order, Truncated LPT, Augmented LPT, MUSCLE and COLA.  The test runs as follows: haloes are defined by applying FoF halo finder to the output of an N-body sim.  The approximate methods are then applied to the same initial conditions of the simulation, producing for all particles displacements from their starting position and velocities.  The position and velocity of each halo are computed by averaging over the particles that belong to that halo, according to the FoF halo finder.  This procedure allows performing a well-posted test of how clustering of the matter density and halo density fields are recovered, without asking to the approximate method an accurate reconstruction of haloes.  Consider the results at z=0, 0.5, 1, and analysed power spectrum in real and z-space, object-by-object difference in position and velocity, density PDF and its moments, phase difference of Fourier modes.  Find that higher LPT orders are generally able to better reproduce the clustering of haloes, while little or no improvement is found for the matter density field when going to 2LPT and 3LPT.  Augmentation provides some improvement when coupled with 2LPT, while its effect is limited when coupled with 3LPT.  Little improvement is brought by MUSCLE with respect to Augmentation.  The more expensive particle-mesh code COLA outperforms all LPT methods.

1704.01054
The effect of Limber and flat-sky approximations on galaxy weak lensing
Lemos, Challinor, Efstathiou

Review the effect of the commonly-used Limber and flat-sky approximation so n the calculation of shear power spectra and correlation functions for galaxy weak lensing.  These approximations are accurate at small scales, but it has been claimed recently that their impact on low multipoles could lead to an increase in the amplitude of the mass fluctuations inferred from surveys such as CFHTLenS, reducing the tension between galaxy WL and the amplitude determined by Planck from observations of the cosmic microwave background.  Here, explore the impact of these approximations on cosmo parameters derived from WL surveys, using CFHTLenS data as a test case.  Conclude that the use of small-angle approximations for cosmo parameter estimation is negligible for current data, and does not contribute to the tension between current WL surveys and Planck.