Day 662

Thursday.

1405.3332
First detection of $^{56}$Co gamma-ray lines from type Ia supernova (SN2014J) with INTEGRAL
Churazov et al

First ever detection of 56Co lines at 847 and 1237 keV and a continuum in the 200-400 keV band from Type Ia SN2014J in M82.  Data taken between 50th and 100th day since the SN2014J outburst.  The line fluxes suggest that 0.62pm0.13 Msun of radioactive 56Ni were synthesized during the explosion.  Line broadening gives a characteristic eject expansion velocity V_e~2100pm500 km/s. The flux at lower energies (200-400 keV) flux is consistent with the 3-photon positronium annihilation, Compton down scattering and absorption in the ~1. Msun eject composed from equal fractions of Fe-group and intermediate-mass elements and a kinetic energy E_k~1.4e51 erg.  All these parameters are in broad agreement with a "canonical" model of an explosion of a Chandrasekhar-mass White Dwarf, providing an unambiguous proof of the nature of Type Ia supernovae as a thermonuclear explosion of a solar mass compact object.

1405.5216
Dwarf galaxies in CDM and SIDM with baryons: observational probes of the nature of dark matter
Vogelsberger et al

Dark matter collisions lead to dwarf galaxies with larger stellar cores and smaller stellar central densities compared to the CDM case.  The central metallicity within 1kpc is also larger by up to ~15% in the former case.  Conclude that the mass distribution and characteristics of the central stars in dwarf galaxies can potentially be used to probe the self-interacting nature of DM.

1405.5221
The decomposed bulge and disk size-mass relations of massive galaxies at 1<z<3 in CANDELS
Bruce et al

A mass-selected sample of M*>1e11 Msun galaxies at 1<z<3 in CANDELS UDS and COSMOS fields, decomposed into their bulge and disk components according to their H(160)-band morphologies.  Extend this analysis to multiple bands, and conduct individual bulge and disk component SED fitting with stellar-mass and star-formation rate estimates for the separate bulge and disk components.  These have been combined with size measurements to explore the evolution of these massive high-z galaxies.  By utilizing the new decomposed stellar-mass estimates, confirm that the bulge components display a stronger size evolution than the disks.  This can be seen from both the fraction of bulge components which lie below the local relation and the median sizes of the bulge components, where the bulges are a median factor of 2.9x times smaller than similarly massive local galaxies at 1<z<2 and 3.4x smaller at 2<z<3; for the disks the corresponding factors are 1.6 and 2.0.  Moreover, by splitting the sample in the the passive and SF bulge and disk sub-populations and examining their sizes as a fraction of their present-day counter-parts, find that the SF and passive bulges are equally compact, SF disks are larger, while the passive disks have intermediate sizes.  This trend is not evident when classifying galaxy morphology on the basis of single-Sersic fits and adopting the overall SFRs.  By evolving the SFHs of the passive disks back to the redshifts when the passive disks were last active, show that the passive and SF disks have consistent sizes at the relevant epoch.  These trends need to be reproduced by any mechanisms which attempt to explain the morphological evolution of galaxies.