Day 783

Tuesday.

Planetary-Science.com
Punga Mare Waves
Cassini/VIMS observes rough surfaces on Titan's Pnga Mare in specular reflection.


1411.2050
The impact of foregrounds on redshift space distortion measurements with the highly-redshifted 21 cm line
Pober
The highly redshifted 21 cm line of H has become recognized as a unique probe of cosmo from relatively low redshifts (z~1) up through EoR (z~8) and even beyond.  To date, most work has focused on recovering the spherically averaged PS of the 21 cm signal, since this approach maximizes the S/N in the initial measurement.  However, like galaxy surveys, the 21 cm signal is effected by z space distortion effects, and is inherently anisotropic between the LoS and transverse directions.  A full measurement of this anisotropy can yield unique cosmological information, potentially even isolating the matter PS from astrophysical effects at high z.  However, FGs also have an anisotropic footprint between the LoS and transverse directions: the so-called FG "wedge".  Although techniques to subtract FGs are actively being developed, a "FG avoidance" approach of simply ignoring contaminated modes has arguably proven most successful to date.  In this work, analyze the effect of this FG anisotropy in recovering the z space distortion signature in 21 cm measurements using a FG avoidance approach at both high and intermediate redshifts.  Find the FG wedge corrupts nearly all of the z space signal for even the largest proposed EoR experiments (HERA and the SKA), making cosmological information unrecoverable without FG subtraction.  The situation is somewhat improved at lower redshifts, where the z-dependent mapping from observed coordinates to cosmo coordinates significantly reduces the size of the wedge.  Using only FG avoidance, find that a large experiment like CHIME can place non-trivial constraints on cosmological parameters.