Day 876

Tuesday.


icarus 2014.01.030
Glory on Vemus cloud tops ad the unknown UV absorber

Report on the implications of the observations of the glory phenomenon by Venus Express orbiter.  Obtain a very accurate estimate of the cloud particle size at 70 km altitude of 1.2 um with a very narrow size distribution.  Also find that the two observations presented the clouds are homogeneous in cloud particle sizes, on scale of at least 1200km.  This is in contrast to previous estimates that were either local, from entry probes data, or averaged over space and time from polarization data.  Secondly, find that the refractive index for the data discussed here is higher than that of sulfuric acid previously proposed for the clouds composition.  Assuming that the species contributing to the increase of the refractive index is the same as the unknown UV absorber, able to constrain the list of candidates.  Investigated several possibilities and argue that either small ferric chloride (FeCL3) cores inside sulfuric acid particles or elemental sulfur coating their surface are good explanations of the observation.


1504.06621
The local group as time machine: studying the high-redshift universe with nearby galaxies
Boylan-Kolchin, et al

Infer the UV luminosities of LG galaxies at early cosmic times (z~2 and ~7) by combining stellar population synthesis modeling with SFHs derived from deep color-magnitude diagrams constructed from HST observations.  Analysis provides a basis for understanding high-z galaxies - including those that may be unobservable even with the JWST - in context of familiar, well-studied objects in the very low-z Universe.  Find that, at the epoch of reionization, all LG dwarfs were less luminous than the faintest galaxies detectable in deep HST observations of blank fields.  Predict that JWST will observe z~7 progenitors of galaxies similar to the LMC today; however, the HST Frontier Fields initiative may already be observing such galaxies, highlighting the power of gravitational lensing.  Consensus reionization models require an extrapolation of the observed blank-field luminosity function at z~7 by at least two orders of magnitude in order to maintain reionization.  This scenario requires the progenitors of the Fornax and Sagittarius dwarf spheroidal galaxies to be contributors to the ionizing background at z~7.  Combined with numerical simulations, the results argue for a break in the UV luminosity function from a faint-end slope of alpha~-2 at M_UV<-13 to alpha~1.2 at lower luminosities.  Applied to photometric samples at lower redshifts, the analysis suggests that HST observations in lensing fields at z~2 are capable of probing galaxies with luminosities comparable to the expected progenitor of Fornax.


1504.06821
From outside-in to inside-out: galaxy assembly mode depends on stellar mass
Pan, et al

Investigate how galaxy mass assembly mode depends on stellar mass M*, using a large sample of ~10k low z galaxies.  The sample is selected to have SDSS R_90>5.0", which allows the measures of both the integrated and the central NUV-r color indices.  Find that: in the M*-(NUV-r) green valley, the M*<1e10 Msun galaxies mostly have positive or flat color gradients, while most f the M*>1e10.5 Msun galaxies have negative color gradients.  When their central Dn4000 index values exceed 1.6, the M*<1e10.0 Msun galaxies have moved to the UV red sequence, whereas a large fraction of the M*>1e10.5 Msun galaxies still lie on the UV blue cloud or the green valley region.  Conclude that the main galaxy assembly mode is transiting from the "outside-in" mode to the "inside-out" mode at M*<1e10 Msun and at M*>1e10.5 Msun.  Argue tat the physical origin of this is the compromise between the internal and the external process that driving the SF quenching in galaxies.  These results can be checked with the upcoming large data produced by the on-going IFS survey projects, such as CALIFA, MaNGA and SAMI in the near future.


1504. 06974
Properties of weak lensing clusters detected on Hyper Suprime-Cam 2.3 square degree field
Miyazaki, et al

Present properties of moderately massive clusters of galaxies detected by the newly developed HSC on Subaru using WL.  8 peaks exceeding a S/N ratio of 4.5 are identified on the convergence SN map of a 2.3 sq deg field observed during the early commissioning phase of the camera.  Multi-color photometric data is used to generate optically selected clusters using the CAMIRA algorithm.  The optical cluster positions were correlated with the peak positions from the convergence map.  All 8 significant peaks have optical counterparts.  The velocity dispersion of clusters are evaluated by adopting the SIS fit to the tangential shear profiles, yielding viral mass estimates, M500c, of the clusters which range from 2.7e13 to 4.4e14 Msun . The number of peaks is considerably larger than the average number expected from LCDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account.  However, could safely argue that the peak count strongly favors the recent Planck result suggesting high sigma8 value of 0.83.  The ratio of stellar mass to the DM halo mass shows a clear decline as the halo mass increases.  If the gas mass fraction, fg, in haloes is universal, as has been suggested in the literature, the observed baron mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.