Cluster morphologies and model-independent Y_SZ estimates from Bolocam Sunyaev-Zel'dovich images

TL;DR

This paper presents high-resolution Bolocam SZ images of galaxy clusters, demonstrating the detection of SZ signals beyond r500, modeling cluster morphologies, and providing model-independent estimates of Y500 that align with theoretical expectations.

Contribution

It introduces model-independent Y500 estimates from Bolocam data and confirms elliptical cluster morphologies with consistent ellipticity measurements.

Findings

Detection of SZ signal beyond r500 in cluster profiles

Elliptical models preferred over spherical models with mean ellipticity 0.27

Model-independent Y500 estimates align with self-similar scaling and have ~10% uncertainties

Abstract

We present initial results from our ongoing program to image the Sunyaev-Zel'dovich (SZ) effect in galaxy clusters at 143 GHz using Bolocam; five clusters and one blank field are described in this manuscript. The images have a resolution of 58 arcsec and a radius of 6-7 arcmin, which is approximately r500 - 2r500 for these clusters. The beam-smoothed RMS is ~10 uK_CMB in these images; with this sensitivity we are able to detect SZ signal to beyond r500 in binned radial profiles. We have fit our images to beta and Nagai models, fixing spherical symmetry or allowing for ellipticity in the plane of the sky, and we find that the best-fit parameter values are in general consistent with those obtained from other X-ray and SZ data. Our data show no clear preference for the Nagai model or the beta model due to the limited spatial dynamic range of our images. However, our data show a definitive preference for elliptical models over spherical models. The weighted mean ellipticity of the five clusters is 0.27 +- 0.03, consistent with results from X-ray data. Additionally, we obtain model-independent estimates of Y500, the integrated SZ y-parameter over the cluster face to a radius of r500, with systematics-dominated uncertainties of ~10%. Our Y500 values, which are free from the biases associated with model-derived Y500 values, scale with cluster mass in a way that is consistent with both self-similar predictions and expectations of a 10% intrinsic scatter.