2006/08/31 by K. Coble, Massimiliano Bonamente, M. Bonamente +14
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Cluster (spacecraft) #Cosmic microwave background #Flux (metallurgy) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Optics #Physics #RADIUS #Radio Astronomy Observations and Technology #Spectral index #Spectral line #astro-ph
paper · pdf · doi:10.1086/519973
published as Astron.J.134:897-905,2007 · 32 pages, 6 figures, accepted to AJ
arxiv created 2007/06/27 · openalex publication_date 2007/06/29 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/08
Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5' of the cluster center) are a factor of 8.9 times higher than counts in the outer regions of the cluster fields (radius greater than 0.5'). Counts in the outer regions of the cluster fields are, in turn, a factor of 3.3 greater than those in the noncluster fields. Counts in the noncluster fields are consistent with extrapolations from the results of other surveys. We compute the spectral indices of millijansky sources in the cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of α = 0.66 with an rms dispersion of 0.36, where flux S ∝ ν -α . The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.