Shedding light on foregrounds with new MWA and PAPER data

Abstract

Summary form only given. Significant effort has recently been turned to the problem of detecting and characterizing intergalactic hydrogen prior to its complete ionization by stars, occurring sometime before t=950Ma (z=6). The distribution of HI, visible in redshifted 21cm radio emission, is one of the few observables into the onset of non-linear structure leading to the birth of the first stars and galaxies. Before it was ionized by stellar UV radiation, HI was found throughout the universe, roughly tracing out the underlying matter distribution and temperature. HI 21cm emission from this epoch (6 <; z <; 12) is redshifted into the VHF radio band (100 <; f <; 200 MHz) and with a observer frequency depending on redshift/distance provides a fully three dimensional view. The emission is expected to have surface brightness of ~25mK with a non-gaussian distribution and most power occurring on scales of 10cMpc. Here we describe how data from PAPER and MWA have significantly tightened our constraints on bright foregrounds, and through comparison, identified some of the most likely sources of error in foreground removal steps. In addition we present early results of an exploration of the redshift and spatial dependence of fainter foreground components identified in the deep PAPER data which has so far given the tightest constraints. Comparing with new MWA observations we seek to separate possible faint foreground contamination from equally likely systematic corruption.