Galaxy Cluster Scaling Relations between Bolocam Sunyaev-Zel'dovich Effect and Chandra X-Ray Measurements

Abstract

We present scaling relations between the integrated Sunyaev–Zel'dovich effect (SZE) signal, Y_(SZ), its X-ray analogue, Y_X ≡ M_(gas)T_X, and total mass, M_(tot), for the 45 galaxy clusters in the Bolocam X-ray SZ (BOXSZ) sample. All parameters are integrated within r_(2500). Y_(2500) values are measured using SZE data collected with Bolocam, operating at 140 GHz at the Caltech Submillimeter Observatory. The temperature, T_X, and mass, M_(gas,2500), of the intracluster medium are determined using X-ray data collected with Chandra, and M_(tot) is derived from M_(gas) assuming a constant gas mass fraction. Our analysis accounts for several potential sources of bias, including selection effects, contamination from radio point sources, and the loss of SZE signal due to noise filtering and beam-smoothing effects. We measure the Y_(2500)–Y_X scaling to have a power-law index of 0.84 ± 0.07, and a fractional intrinsic scatter in Y_(2500) of (21 ± 7)% at fixed YX, both of which are consistent with previous analyses. We also measure the scaling between Y_2500 and M_2500, finding a power-law index of 1.06 ± 0.12 and a fractional intrinsic scatter in Y_(2500) at fixed mass of (25 ± 9)%. While recent SZE scaling relations using X-ray mass proxies have found power-law indices consistent with the self-similar prediction of 5/3, our measurement stands apart by differing from the self-similar prediction by approximately 5σ. Given the good agreement between the measured Y_(2500)–Y_X scalings, much of this discrepancy appears to be caused by differences in the calibration of the X-ray mass proxies adopted for each particular analysis.

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