1112.5151 (Jack Sayers et al.)

Bolocam Observations of Two Unconfirmed Galaxy Cluster Candidates from the Planck Early SZ Sample    [PDF]

Jack Sayers, Nicole G. Czakon, Carrie Bridge, Sunil R. Golwala, Patrick M. Koch, Kai-Yang Lin, Sandor M. Molnar, Keiichi Umetsu

We present Bolocam observations of two clusters of galaxies reported as unconfirmed in the Planck early Sunyaev-Zel'dovich (eSZ) sample, PLCKESZ G115.71 and PLCKESZ G189.84. These are the only remaining unconfirmed candidates from the original list of eight unconfirmed candidates in the eSZ. We observed each of these candidates with Bolocam at 140 GHz from the Caltech Submm Observatory in October 2011. The resulting images have white noise levels of \simeq 30 {\mu}KCMB-arcmin in their central regions. We find a significant SZ decrement towards PLCKESZ G115.71. This decrement has a false detection probability of 5.3\times10-5, and we therefore confirm PLCKESZ G115.71 as a cluster. The maximum SZ decrement towards PLCKESZ G189.84 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 PLCKESZ G115.71, providing further evidence that it is a cluster. We do not find a significant overdensity of WISE sources at the location of PLCKESZ G189.84, although the number of WISE sources is above average.

View original: http://arxiv.org/abs/1112.5151