Bolocam observations of two unconfirmed galaxy cluster candidates from the planck early Sunyaev-Zel'Dovich sample

Abstract

We present Bolocam observations of two galaxy cluster candidates reported as unconfirmed in the Planck early Sunyaev-Zel'dovich (eSZ) sample, PLCKESZG115.71+17.52 and PLCKESZG189.84-37.24. We observed each of these candidates with Bolocam at 140 GHz from the Caltech Submillimeter Observatory in 2011 October. The resulting images have white noise levels of ≃ 30 μKCMB arcmin in their central regions. We find a significant SZ decrement toward PLCKESZG115.71. This decrement has a false detection probability of 5.3 × 10-5, and we therefore confirm PLCKESZG115.71 as a cluster. The maximum SZ decrement toward PLCKESZG189.84 corresponds to a false detection probability of 0.027, and it therefore remains as an unconfirmed cluster candidate. In order to make our SZ-derived results more robust, we have also analyzed data from the Wide-field Infrared Survey Explorer (WISE) at the location of each cluster candidate. We find an overdensity of WISE sources consistent with other clusters in the eSZ at the location of PLCKESZG115.71, providing further evidence that it is a cluster. We do not find a significant overdensity of WISE sources at the location of PLCKESZG189.84. © © 2012. The American Astronomical Society. All rights reserved.