Day 63

Friday.  Took Thursday and Friday off at a place w/o internet connection.


1108.3678
XMM-Newton/SDS: star fromation efficiency in galaxy clusters and constraints on the matter density parameter
Lagana, Zhang, Reiprich, Schneider


The gas fraction in clusters are probably not uniform--past papers show that the baryonic fraction is higher for higher-mass clusters.  This study shows that at M_500 = 1e15 M_sun the baryonic content (determined from SDSS stellar mass and XMM-Newton gas mass) is about WMAP7 value.  The stellar mass decreases with increasing total mass fraction -- from 4.5% to 1.0%.  There must be differences in stellar formation efficiencies such that lower mass systems are likely to have higher SF efficiencies (why not quenching in massive clusters?).  Dependence of the stellar mass fraction on total mass results in an increase of the M/L ratio from lower to higher mass systems.


1108.3567
WR 38/38a and the ratio of total-to-selective extinction in Carina
Turner


* Wolf-Rayet stars: Has unusual spectra, where no H absorption is found, but has wide He, C, N, etc, emission lines.  A massive star whose H burning has generated a massive He core, the H is removed from the star due to stellar winds, the hot, internal core is exposed, and becomes a blue giant. This is a Wolf-Rayet star.  The broad emission line comes from the Doppler effect from the hot gas.  Three types: WN (N dominant), WC (C dominant), and WO (O dominant emission lines).  It is expected for WR stars to go nova, presumably Ib or Ic (i.e., those without H absorption).


There seems to be anomalous dust extinction that is widespread in the Carina region, as studied from existing UVB and 2MASS JHK observations.  Affects interpretation of distances to optical spiral arm indicators.