Day 1186

Tuesday.

1611.03859
Rocky Planetesimal formation via fluffy aggregates of nanograins
Arakawa, Nakamoto

Several pieces of evidence suggest that silicate grains in primitive meteorites are not interstellar grains but condensates formed in the early solar system.  Moreover, the size distribution of matrix grains in chondrites implies that these condensates might be formed as nanometer-sized grains.  Therefore, propose a novel scenario for rocky planetesimal formation in which nanometer-sized silicate grains are produced by evaporation and recondensation events in early solar nebula, and rocky planetesimals are formed via aggregation of these nano grains.  Reveal that silicate nano grains can grow into rocky planetesimals via direct aggregations without catastrophic fragmentation and serious radial drift, and the results provide a suitable condition for protoplanet formation in the SS.


1611.03866
Cluster mass calibration at high redshift: HST weak lensing analysis of 13 distant galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich survey
Schrabback, Applegate, Dietrich, Hoekstra, et al

Present an HST/ACS WL analysis of 13 massive high-z (z_median=0.88) galaxy clusters discovered in SPT SZ survey.  This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmo constraints from the SPT cluster sample.  Introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scale relations significantly.  First, efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour.  The estimate of the source redshift distribution is based on CANDELS data, where source selection criteria of the cluster fields is carefully mimicked.  Apply a statistical correction for systematic photo-z errors as derived form Hubble UDF data and verified through spatial cross-correlations.  Account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys.  Finally, account for biases in the mass modelling caused by miscentering and uncertainties in the m-c relation using sims.  In combination with temperature estimates from Chandra, constrain the normalization of the m-T scaling relation ln(E(z) M_500c/1e14 Msun) = A+1.5 ln(kT/7.2 keV) to A=1.81+0.24-0.14(stat.) ± 0.09 (sys.), consistent with self-similar z evolution when compared to lower z samples.  Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6+3.7-1.8.


1611.04165
Reconstruction of halo power spectrum from redshift-space galaxy distribution: cylinder-grouping method and halo exclusion effect
Okumura, Takada, More, Masaki

The peculiar velocity field measured by RSD in galaxy surveys provides a unique probe of the growth of large-scale structure.  However, systematic effects arise when including satellite galaxies in the clustering analysis.  Since satellite galaxies tend to reside in massive haloes with a greater halo bias, the inclusion boosts the clustering power.  In addition, virial motions of the satellite galaxies cause a significant suppression of the clustering power due to nonlinear RSD effects.   Develop a novel method to recover the redshift-space power spectrum of haloes from the observed galaxy distribution by minimizing the contamination of satellite galaxies.  The cylinder grouping method (CGM) study effectively excludes satellite galaxies from a galaxy sample.  However, find that this technique produces apparent anisotropies in the reconstructed halo distribution over all the scales which mimic RSD.  On small scales, the apparent anisotropic clustering is caused by exclusion of haloes within the anisotropic cylinder used by the CGM.  On large scales, the misidentification of different haloes in the LSS, aligned along the LoS, into the same CGM group, causes the apparent anisotropic clustering via their cross-correlation with the CGM haloes.  Construct an empirical model for the CGM halo power spectrum, which includes correction terms derived using the CGM window function at small scales as well as the linear matter power spectrum multiplied by a simple anisotropic function at large scales.  Apply this model to a mock galaxy catalog at z=0.5, designed to resemble SDSS-III BOSS CMASS galaxies, and find that the model can predict both the monopole and quadrupole PS of the host haloes up to k<0.5 h/Mpc to within 5%.