Day 803

Wednesday.

1412.0133
New constraints on $f(R)$ gravity from clusters of galaxies
Cataneo, Rapetti, ... Mantz, Allen, Applegate, ... von der Linden, ... et al

The abundance of massive galaxy clusters is a probe of departures from GR on cosmic scales.  Despite current stringent constraints placed by stellar and galactic tests, on large scales alternative theories of gravity such as f(R) can still work as effective theories  Here, present constraints on two popular models of f(R), Hu-Sawicki and "designer", derived from a fully self-consistent analysis of current samples of X-ray selected clusters and accounting for al the covariances between cosmological and astrophysical parameters.  Constraints are mainly driven by cluster number counts, and we obtain substantial improvements on previous upper bounds employing this method.  Also combine these results with recent data from the CMB and the CMB lensing potential generated by LSS, as well as with other cosmological constraints on the background expansion history and its mean matter density.  The robustness of the results derives from high quality cluster growth data for the most massive clusters known out to z~0.5, a tight control of systematic uncertainties including an accurate and precise mass calibration from WL, and the use of the full shape of the halo MF over the mass range of data.

1412.2745
Deuterium enrichment of the interstellar medium
Das, Majumdar, Chakrabarti, Sahu

Explore various aspects of D enrichment by constructing a chemical evolution model in gas and grain phases.  Depending on various physical parameters, gas and grains are allowed to interact with each other through exchange of their chemical species.  It is known that HCO+ and N2H+ are two abundant gas phase ions in ISM and their D fractionation are generally used to predict degree of ionization in various regions of a molecular cloud.  To have a more realistic estimation, consider a density profile of a collapsing cloud.  Present radial distributions of important interstellar molecules along with their deuterated isotopomer.  Carry out quantum chemical simulation to study effects of isotropic substitution on spectral properties of these important interstellar species.  Calculate vibrational (harmonic) frequency of the most important deuterated species (neutral & ions).  Rotational and distortional constants of these molecules are also computed to predict rotational transitions of these species.  Compare vibrational (harmonic) and rotational transitions as computed here with existing observational, experimental and theoretical results.  Results would assist observes in their quest of several hitherto unobserved deuterated species.

1412.2748
Local group galaxies emerge from the dark
Sawala, Frenk, ... 

The LCDM model of cosmic structure formation is eminently falsifiable: once its parameters are fixed on large scales, it becomes testable in the nearby Universe.  Observations within our Local Group of galaxies, including the satellite populations of the MW and Andromeda, appear to contradict LCDM predictions: there are far fewer satellite galaxies than DM haloes (the "missing satellites" problem), galaxies seem to avoid the largest substructures (the "too big to fail" problem), and the brightest satellites appear to orbit their host galaxies on a thin plane (the "planes of satellites" problem).  Present results from the first hydrodynamic simulations of the LG that match the observed abundance of galaxies.  Find that when baryonic and DM are followed simultaneously in the context of a realistic galaxy formation model, all 3 "problems" are resolved within the LCDM paradigm.