Day 338

Thursday.


1211.4583
A possible impact near the Milky Way of a former major merger in the local group
Fouquet et al

MW dwarf system has 2 'exceptional' features: Thick plane ("Vast Polar Structure") and the MCs (irregulars that almost never seen this close from a L* galaxy like the MW).  Simulation of M31 show that a former gas-rich major merger's tidal tail may have reached the MW.  Most of the MW dwarves (including the MCs) may have been formed within a tidal tail during the former merger in the local group.  Leads to a fair reproduction of the VPOS as well as to a simple explanation of the MCs proximate to the MW (accounts for both the weird features).  But, this scenario predicts DM-free MW dwarves, in contradiction with their intrinsically large velocity dispersions.  Requires further investigation.

1211.4584
The rate of WD-WD head-on collisions may be as high as the SNe Ia rate
Katz, Dong

As the title says.

1211.4345
Cosmic microwave background filters and the dark-flow measurement
Atrio-Barandela, Kashlinsky, Ebeling, Kocevski

[Oh wait, I think I pretended to read this one before, but I didn't understand it was about DM flow]  kSZ measurements identifies a bulk flow roughly aligned with CMB dipole and of magnitude 600-1000 km/s at 0.5-1 Gpc scale; [then talks about data filtering] no detection of large-scale flow indicates inadequate filtering.  Filter normalization gives results similar to their result.  Discrepancies come from cluster profiles.  

1211.4439
A multi-wavelength study of the gravitational lens COSMOS J095930+023427
Cao et al

z=0.89 lens, with LoS group lens at z=0.7.  Source redshift ~2.0.  Einstein radius of 0.79".  SIE and PIEMD mass analysis; total mass, DM fraction within Einstein radius,, and external shear due to a FG galaxy group are robust wrt the choice of parametric model and source redshift.  Measure luminous mass from photometric data; DM fraction between 0.71 to 0.79 depending on the unknown source z.  The non-null external shear found in lensing models supports the presence and structure of galaxy group at z~0.7, and an independent measurement of 0.5-2 keV X-ray luminosity within 20" around X-ray centroid provides a group mass of M=3-10*1e13 Msun, in good agreement with previous WL estimate.

1211.4480
Cosmology with photometrically-classified Type Ia supernovae from the SDSS-II supernova survey
Campbell, D'Andrea, Nichol, Sako, ... et al

752 photometrically classified SNIa from SDSS-II SN survey, supplemented by BOSS.  Host galaxy redshifts of 0.05<z<0.55; SNIa typing efficiency of 70.8% with 3.9% contamination.  Demonstrate that this contamination has no effect on the cosmology constraints; quantify and correct for selection effects (Malmquist bias) with simulations.  Fit to flat LCDM; omega_m=024pm0.07 (statistical errors only).    Competitive omega_m and omega_lambda from SNLS3.  w=-0.96pm0.1, omega_k=0pm0.03; competitive with spectro SNIa.  Lower redshift leverage of SDSS-II SN sample, but lack of spectroscopic confirmation.

1211.4585
Toward a direct measurement of the cosmic acceleration
Darling

HI 21cm absorption line redshifts observed in multiple epochs (13.5 years)