Day 421

Friday.

1304.6719
The column density distribution and continuum opacity of the intergalactic and circumgalactic medium at redshift <z>=2.4
Rudie, Steidel, Shapley, Pettini

As the title says.  Use hyperluminous QSO, fit Voigt profile to full Lyman alpha and beta forests in 15 high-res high-S/N spectra; measure IGM, CGM.  Find that the incidence of absorbers in the CGM is much higher than in the IGM.  In agreement with Rudie+, find that there are fractionally more high-NHI absorbers than low-NHI absorbers in the CGM compared to the IGM, leading to a shallower power law fit to the CGM frequency distribution.  Reproducing the opacity measured as well as the incidence of absorbers with log(NHI)>17.2 requires a broken power law parameterization of the frequency distribution with a break near log(NHI)~15.  Compute new estimates of the MFP (mean free path) to H-ionizing photos at z=2.4; find MFP=147 pm 15 Mpc when considering only IGM opacity.  If considering photos emanating from a high-z SF galaxies and account for the local excess opacity due to the surrounding CGM of the galaxy itself, the MFP is reduced to 121 pm 15 Mpc.  These MPF measurements are smaller than recent estimates and should inform future studies of the metagalactic UV background and of ionizing sources at z~2-3.

1304.6780
Practices in source code sharing in astrophysics
Shamir et al

Suggest that a paper that involves a computer program not be accepted for publication unless the source code becomes publicly available.