Day 859

Monday.

1503.07863
A first detection of the acoustic oscillation phase shift expected from the cosmic neutrino background
Follin, Knox, Millea, Pan

The free streaming of cosmological neutrinos prior to recombination of the baryon-photon plasma alters gravitational potentials and therefore the details of the time-dependent gravitational driving of acoustic oscillations.  Report here a first detection of the resulting shifts in the temporal phase of the oscillations, which is inferred form their signature in the CMB temperature PS.  The magnitude of the shift is proportional to the fraction of the total radiation density in neutrinos.  Parameterizing the shift via an effective number of neutrino species, find 1.9<N_nu^{delta phi} < 3.4 at 68% confidence, consistent with the standard model value of N_nu=3.046, and inconsistent with zero.


1503.07880
The difficulty getting high escape fractions of ionizing photons from high-redshift galaxies: a few from the FIRE cosmological simulations
Ma, Kasen, Hopkins, Gaucher-Giguere, Quataert, Keres, Murray

Because the high intrinsic ionizing photons are dominated by stellar populations younger than 3Myr, which tend to be buried in dense birth clouds.  The escaping photons mostly come from populations between 3-10 Myr, whose birth clouds have been largely cleared by stellar feedback, but these populations only contribute a small fraction of intrinsic ionizing photon budgets according to standard stellar population models.