A joint analysis of AMI and CARMA observations of the recently discovered SZ galaxy cluster system AMI-CL J0300+2613

TL;DR

This paper combines AMI and CARMA observations to analyze a newly discovered galaxy cluster via the Sunyaev-Zel'dovich effect, using Bayesian methods to estimate its properties and detection significance.

Contribution

It introduces a joint Bayesian analysis of AMI and CARMA data for galaxy clusters, comparing physical models and assessing detection probabilities without prior redshift knowledge.

Findings

Bayesian probability of detection exceeds 4,500:1 with combined data.

Estimated cluster mass within r200 is 4.1x10^14 solar masses.

The SZ temperature decrement is 170 microKelvin, with weaker signals in CARMA data.

Abstract

We present CARMA observations of a massive galaxy cluster discovered in the AMI blind SZ survey. Without knowledge of the cluster redshift a Bayesian analysis of the AMI, CARMA and joint AMI & CARMA uv-data is used to quantify the detection significance and parameterise both the physical and observational properties of the cluster whilst accounting for the statistics of primary CMB anisotropies, receiver noise and radio sources. The joint analysis of the AMI & CARMA uv-data was performed with two parametric physical cluster models: the {\beta}-model; and the model described in Olamaie et al. 2012 with the pressure profile fixed according to Arnaud et al. 2010. The cluster mass derived from these different models is comparable but our Bayesian evidences indicate a preference for the {\beta}-profile which we, therefore, use throughout our analysis. From the CARMA data alone we obtain a Bayesian probability of detection ratio of 12.8:1 when assuming that a cluster exists within our search area; alternatively assuming that Jenkins et al. 2001 accurately predicts the number of clusters as a function of mass and redshift, the Bayesian probability of detection is 0.29:1. From the analysis of the AMI or AMI & CARMA data the probability of detection ratio exceeds 4.5x10^3:1. Performing a joint analysis of the AMI & CARMA data with a physical cluster model we derive the total mass internal to r200 as MT,200 = 4.1x10^14Msun. Using a phenomenological {\beta}-model to quantify the temperature decrement as a function of angular distance we find a central SZ temperature decrement of 170{\mu}K in the AMI & CARMA data. The SZ decrement in the CARMA data is weaker than expected and we speculate that this is a consequence of the cluster morphology. In a forthcoming study we will assess the impact of cluster morphology on the SZ decrements that are observed with interferometers such as AMI and CARMA.