Day 981

Monday.


1510.00390
Galaxies infalling into groups: filaments vs. isotropic infall
Martinez, Muriel, Coenda

Perform a comparative analysis of the properties of galaxies infalling into groups classifying them accordingly to whether they are: calling along filamentary structures; or they are falling isotropically.  For this purpose, identify filamentary structures connecting massive groups of galaxies in the SDSS.  Perform a comparative analysis of some properties of galaxies in filaments, in the isotropic infall region, in the field, and in groups. Study the luminosity functions (LF) and the dependence of the sSFR on stellar mass, galaxy type, and projected distance to the groups that define the filaments.  Find that the LF of galaxies in filaments and in the isotropic infalling region are basically indistinguishable between them, with the possible exception of late-type galaxies.  On the other hand, regardless of galaxy type, their LFs are clearly different from that of field or group galaxies.  Both of them have characteristic absolute magnitudes and faint end slopes in between the field and group values.  More significant differences between galaxies in filaments and in the isotropic infall region are observed when the sSFR is analyzed.  Find that galaxies in filaments have a systematically higher fraction of galaxies with low sSFR as a function of both, stellar mass and distance to the groups, indicating a stronger quenching of the SF in the filaments compared to both, the isotropic infalling region, and the field.  Results suggest that some physical mechanisms that determine the differences observed between field galaxies and galaxies in systems, affect galaxies even when they are not yet within the systems.


1510.00393
On the clustering of faint red galaxies
Xu, Zhen, Guo, Zhu, Zehavi

Faint red galaxies in SDSS show a puzzling clustering pattern in previous measurements.  In the 2PCF, they appear to be strongly clustered on small-scales, indicating a tendency to reside in massive haloes as satellite galaxies.  However, their weak clustering on large scales suggests that they are more likely to be found in low mass haloes.  The interpretation of the clustering pattern suffers from the large sample variance in the 2PCF measurements, given the small volume of the volume-limited sample of such faint galaxies.  Introduce a method to improve the clustering measurements of faint galaxies by making a full use of a flux-limited sample to obtain volume-limited measurements with an increased effective volume.  In the improved 2PCF measurements, the fractional uncertainties on large-scales drop by more than 40%, and the strong contrast between small-scale and large-scale clustering amplitudes see in previous work is no longer prominent.  From HOD modeling of the measurements, find that a considerable fraction of faint red galaxies to be satellites in massive haloes, a scenario supported by the strong covariance of small-scale 2PCF measurements and the relative spatial distribution of faint red galaxies and luminous galaxies.  However, the satellite fraction is found to be degenerate with the slope of the distribution profile of satellites in inner haloes.  Compare the modeling results with SAM predictions and discuss the implications.


1510.00688
Is there concordance within the concordance $\Lambda$CDM model?
Raveri

Use a complete and rigorous statistics indicator to measure the level of concordance between cosmological data sets, without relying on the inspection of the marginal posterior distribution of some selected parameters.  Apply this test to state of the art cosmo data sets, to assess their agreement within the LCDM model.  Find that there is a good level of concordance between all the experiments with one noticeable exception.  There is substantital evidence of tension between CMB, temperature and polarization, measurements of the Planck satellite and the data from the CFHTLenS weak lensing survey even when applying ultra conservative cuts.  These results robustly point toward the possibility of having unaccounted systematics effects in the data, an incomplete modeling of the cosmo predictions or hints toward new physical phenomena.