Radio Sources toward Galaxy Clusters at 30 GHz

Abstract

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 0 of the cluster center) are a factor of 8:9 þ4:3 À2:8 times higher than counts in the outer regions of the cluster fields (radius greater than 0.5 0 ). Counts in the outer regions of the cluster fields are, in turn, a factor of 3:3 þ4:1 À1:8 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 ¼ 0:66 with an rms dispersion of 0.36, where flux S / À . 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.

X-Ray Properties of the First Sunyaev-Zel'dovich Effect Selected Galaxy Cluster Sample From the South Pole Telescope

“…The majority of radio sources in clusters have been found to have steep spectra with α < −0.5 (where S ∝ ν α ) (e.g., Coble et al 2007;Lin et al 2009). For example, Coble et al (2007) find a median spectral index of −0.72 between 1.4 and 28.5 GHz for radio sources toward a sample of massive clusters ranging from 0.14 < z < 1.0. In V10, they noted that a typical cluster would suffer a decrease of Δξ = 1 for a 2 mJy (5 mJy) source at 150 GHz located at 0.…”

“…For the mass limit of this work, M 500 ≈ 3 × 10 14 h −1 M , these studies predict that in 1% of clusters there would be radio source contamination large enough to affect the SZ flux measurement at the >20% level, with this result largely independent of redshift. V10 estimate a similar rate of contamination using a radio source count model (de Zotti et al 2005) and the measured overabundance of radio sources near clusters (Coble et al 2007). Overall, the combination of the above results leads us to not expect any significant radio source contamination.…”

Redshift evolution of the 1.4 GHz volume averaged radio luminosity function in clusters of galaxies

“…As extreme values of the ensemble average spectral slope, we use the 25th and 75th percentiles (α = 0.51 and α = 0.92, respectively) of the slope distribution of Coble et al (2007). We recompute the maxBCG RLF using these extreme spectral slopes for all sources.…”

Peculiar Velocity Constraints From Five-Band Sz Effect Measurements Toward Rx J1347.5−1145 With Music and Bolocam From the Cso

“…As a result, a wide range of available measurements of the AGN at frequencies close to the Bolocam+MUSIC observing bands were used to obtain a power-law fit to the flux density of the AGN. Specifically, these data include a 1.4 GHz measurement from NVSS (Condon et al 1998), 8.5 and 22.5 GHz measurements from VLA (Komatsu et al 2001), a 28.5 GHz measurement from OVRO/BIMA (Coble et al 2007), a 30.9 GHz measurement from SZA (Bonamente et al 2012), a 90 GHz measurement from MUSTANG (Korngut et al 2011), 86 and 90 GHz measurements from CARMA (Plagge et al 2013), a 100 GHz measurement from NMA (Komatsu et al 1999), a 140 GHz measurement from Diablo (Pointecouteau et al 2001), and a 250 GHz measurement from SCUBA (Komatsu et al 1999). All of these data were collected using interferometers except for MUSTANG (which is a high angular-resolution single-dish photometer), Diablo (where the SZ effect and AGN signals were simultaneously modeled), and SCUBA (which was relatively close to the null in the thermal SZ effect signal).…”