Opening the 21cm EoR Window: Measurements of Foreground Isolation with PAPER

摘要

We present new observations with the Precision Array for Probing the Epoch ofReionization (PAPER) with the aim of measuring the properties of foregroundemission for 21cm Epoch of Reionization experiments at 150 MHz. We focus on thefootprint of the foregrounds in cosmological Fourier space to understand whichmodes of the 21cm power spectrum will most likely be compromised by foregroundemission. These observations confirm predictions that foregrounds can beisolated to a "wedge"-like region of 2D (k-perpendicular, k-parallel)-space,creating a window for cosmological studies at higher k-parallel values. We alsofind that the emission extends past the nominal edge of this wedge due tospectral structure in the foregrounds, with this feature most prominent on theshortest baselines. Finally, we filter the data to retain only this "unsmooth"emission and image specific k-parallel modes of it. The resultant images showan excess of power at the lowest modes, but no emission can be clearlylocalized to any one region of the sky. This image is highly suggestive thatthe most problematic foregrounds for 21cm EoR studies will not be easilyidentifiable bright sources, but rather an aggregate of fainter emission.