Results from the OVRO SZE Survey of Nearby X-Ray Selected Clusters

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Session 57 -- COBE and Related Papers
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[57.12] Results from the OVRO SZE Survey of Nearby X-Ray Selected Clusters

J.E.\ Baker (U.C. Berkeley), S.T.\ Myers, A.C.S.\ Readhead (Caltech), T. Herbig (Princeton)

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We present results from the Sunyaev-Zeldovich Effect (SZE) survey underway at the Caltech Owens Valley Radio Observatory (OVRO). An X-ray flux limited sample of nearby clusters was selected from Edge et.\ al. (1990), and a luminosity limited subset of 11 clusters was targeted for observations using the OVRO 5.5-m telescope at a frequency of 32~GHz. This sample includes the Coma cluster previously observed at OVRO by Herbig {\it et.\ al.} (1994). We report new significant detections of the SZE in A85, A478, A2029, A2142, and A2256. The 5.5-m telescope system is ideal for observations of nearby clusters. The system employs a dual-horn switched HEMT receiver with low noise ($< 40$K), wide bandwidth (29--35 GHz), a large beam ($7\pmin4$ FWHM), and a large switching angle ($22\pmin16$), and is thus able to make a $3\sigma$ detection of the SZE decrement in these massive clusters in a few hours of observing.

We use the SZE measurements and X-ray data for A478, A2142, A2256 and Coma to place constraints upon the state of the cluster medium and the value of the Hubble constant $H_0$. The OVRO SZE detections are significant at better than $13\sigma$ (A478), $18\sigma$ (A2142), $11\sigma$ (A2256) and $6\sigma$ (Coma). The unavailability of accurate models for the cluster gas, especially for the cooling flow clusters A478 and A2142, and the proposed merging cluster A2256, limit the utility of the data to constrain $H_0$, but as an ensemble the sample promises to provide important new tests of cosmology and cluster astrophysics.

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