1509.03632
Quenching star formation: insights from the local main sequence
Leslie, Kewley, Sanders, Lee
The so called "star forming main sequence" of galaxies is the apparent tight relationship between the star formation rate and stellar mass of a galaxy. Previous studies exclude galaxies which are not strictly "star forming" from the main sequence, because they do not lie on the same tight relation. Using local galaxies in SDS, classify galaxies according to their emission in ratios, and study their location on the SFR - stellar mass plane. Find that galaxies form a sequence from the "blue cloud" galaxies which are actively forming stars, through a combination of composite, Seifert, and LINER (Low-ionization nuclear emission-line region) galaxies, ending as "read-and-dead" galaxies. The sequence supports an evolutionary pathway for galaxies in which SF quenching by AGN plays a key role.
1509.03947
Formation of emission line dots and extremely metal-deficient dwarfs from almost dark galaxies
Bekki
Recent observations have discovered a number of extremely gas-rich very faint dwarf galaxies possibly embedded in low-res DM haloes. Investigate SFHs of these gas-rich dwarf ("almost dark") galaxies both for isolated and interacting/merging cases. Find that although SFRs are very low (1e-5 Msun/yr) in the simulated dwarfs in isolation for the total halo masses (M_h) of 1e8-9 Msun, they can be dramatically increased to be ~1e-4 Msun/yr when they interact omega with other dwarfs. These interacting faint dwarfs with central compact HII regions can be identified as isolated emission dots ("ELdots") owing to their very low surface brightness envelopes of old stars. The remnant of these interacting and merging dwarf can finally develop central compact stellar systems with very low metallicities (Z/Zsun<0.1), which can be identified as extremely metal-deficient ("XMD") dwarfs. These results imply that although there would exist many faint dwarfs that can be hardly detected n the current optical observations, they can be detected as isolated ELdots or XMD dwarfs, when they interact with other galaxies and their host environments. Predict that owing to the very low surface brightness stellar envelopes, if they are distant objects.
1509.04071
A direct measurement of tomographic lensing power spectra from CFHTLenS
Köhlinger, Viola, Valkenburg, Joachimi, Hoekstra, Kuijken
Measure the WL shear power spectra and their cross-power in 2 photo-z bins from the CFHTLenS. The measurements are performed directly in multipole space in terms of adjustable band powers. For the extraction of the band powers from the data, implemented and extended a quadratic estimator, a maximum likelihood method that allows to readily take into account irregular survey geometries, masks, and varying sampling densities. Find the 68% credible intervals in the sigma8-Omega_m-plane to be marginally consistent with results from Planck for a single five parameter LCDM model. For the projected parameter S8==sigma8(Omega_m/0.3)^0.5, obtain a best-fitting value of S8=0.768+0.045=0.039. This constraint is consistent with results from other CFHTLenS studies as well as the DES. The most conservative model, including modifications to the power spectrum due to baryon feedback and marginalization over photo-z errors, yields an upper limit on the total mass of 3 degenerate massive neutrinos of Sigma m_nu<4.53 eV at 95 % credibility, while a Bayesian model comparison does not favor any model extension beyond a simple 5 parameter LCDM model. Combining the shear likelihood with Planck breaks the sigma8-Omega_m degeneracy and yields sigma8=0.817+0.013-0.014 and Omega_m=0.298±0.011 which is fully consistent with results from Planck alone.
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