CARMA observations of massive Planck-discovered cluster candidates at z>0.5 associated with WISE overdensities: Breaking the size-flux degeneracy

TL;DR

This study demonstrates how combining Planck, WISE, and CARMA-8 data effectively identifies and characterizes massive galaxy clusters at z>0.5, reducing uncertainties and breaking degeneracies in size-flux measurements.

Contribution

The paper introduces a method integrating Planck, WISE, and CARMA-8 observations to accurately detect and analyze high-redshift galaxy clusters, improving parameter precision.

Findings

Identified massive, compact galaxy clusters at z>0.5.

Good agreement between Planck and CARMA-8 measurements of Y_{500}.

Reduced parameter uncertainties by over a factor of 4 using combined data.

Abstract

We use a Bayesian software package to analyze CARMA-8 data towards 19 unconfirmed Planck SZ-cluster candidates from Rodriguez-Gonzalvez et al. (2015), that are associated with significant overdensities in WISE. We used two cluster parameterizations, one based on a (fixed shape) generalized-NFW pressure profile and another based on a beta-gas-density profile (with varying shape parameters) to obtain parameter estimates for the nine CARMA-8 SZ-detected clusters. We find our sample is comprised of massive, Y_{500}=0.0010 \pm 0.0015 arcmin^2, relatively compact, theta_{500}= 3.9 \pm 2.0 arcmin systems. Results from the beta model show that our cluster candidates exhibit a heterogeneous set of brightness-temperature profiles. Comparison of Planck and CARMA-8 measurements showed good agreement in Y_{500} and an absence of obvious biases. We estimated the total cluster mass M_{500} as a function of z for one of the systems; at the preferred photometric redshift of 0.5, the derived mass, M_{500} \approx 0.8 \pm 0.2 \times 10^{15} Msun. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our cluster candidates to be at z=0.565. Applying a Planck prior in Y_{500} to the CARMA-8 results reduces uncertainties for both parameters by a factor >4, relative to the independent Planck or CARMA-8 measurements. We here demonstrate a powerful technique to find massive clusters at intermediate z \gtrsim 0.5 redshifts using a cross-correlation between Planck and WISE data, with high-resolution follow-up with CARMA-8. We also use the combined capabilities of Planck and CARMA-8 to obtain a dramatic reduction by a factor of several, in parameter uncertainties.