Open AccessAn Australia Telescope survey for CMB anisotropies
Author(s) -
Subrahmanyan Ravi,
Kesteven Michael J.,
Ekers Ronald D.,
Sinclair Malcolm,
Silk Joseph
Publication year - 2000
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2000.03444.x
Subject(s) - physics , cosmic microwave background , sky , astrophysics , telescope , brightness , anisotropy , noise (video) , background radiation , brightness temperature , astronomy , south pole telescope , optics , radiation , image (mathematics) , artificial intelligence , computer science
We have surveyed six distinct ‘empty fields’ using the Australia Telescope Compact Array (ATCA) in an ultracompact configuration with the aim of imaging, with a high brightness sensitivity, any arcminute‐scale brightness‐temperature anisotropies in the background radio sky. The six well‐separated regions were observed at a frequency of 8.7 GHz, and the survey regions were limited by the ATCA primary beams which have a full width at half‐maximum of 6 arcmin at this frequency; all fields were observed with a resolution of 2 arcmin and an rms thermal noise of 24 μJy beam −1 . After subtracting foreground confusion detected in higher resolution images of the fields, residual fluctuations in Stokes I images are consistent with the expectations from thermal noise and weaker (unidentified) foreground sources; the Stokes Q and U images are consistent with expectations from thermal noise. Within the sensitivity of our observations, we have no reason to believe that there are any Sunyaev–Zeldovich holes in the microwave sky surveyed. Assuming Gaussian‐form CMB anisotropy with a ‘flat’ spectrum, we derive 95 per cent confidence upper limits of Q flat <10–11 μK in polarized intensity and Q flat <25 μK in total intensity. The ATCA filter function peaks at l =4700 and has half‐maximum values at l =3350 and 6050.