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

January 2017 • 2017MNRAS.464.2378R

Authors • Rodríguez-Gonzálvez, C. • Chary, R. R. • Muchovej, S. • Melin, J. -B. • Feroz, F. • Olamaie, M. • Shimwell, T.

Abstract • We use a Bayesian software package to analyse CARMA-8 data towards 19 unconfirmed Planck Sunyaev-Zel'dovich-cluster candidates from Rodríguez-Gonzálvez et al. that are associated with significant overdensities in WISE. We use two cluster parameterizations, one based on a (fixed shape) generalized-NFW (gNFW) pressure profile and another on a β gas density profile (with varying shape parameters) to obtain parameter estimates from the CARMA-8 data for the nine CARMA-8-detected clusters. Results from the β model show that our cluster candidates exhibit a heterogeneous set of brightness-temperature profiles. Comparison of Planck and CARMA-8 measurements show good agreement in Y500 and an absence of obvious biases. Applying a Planck prior in Y500 to the CARMA-8 gNFW results reduces uncertainties in Y500 and Θ500 dramatically (by a factor >4), relative to the independent Planck or CARMA-8 measurements. From this combined analysis, we find that our sample is comprised of massive (Y500 ranging from 3.3^{+0.2}_{-0.2} to 10^{+1.1}_{-1.5} × 10-4 arcmin2, sd = 2.2 × 10-4), relatively compact (θ500 ranging from 2.1^{+0.1}_{-0.3} to 5.5^{+0.2}_{-0.8} arcmin, sd = 1.0) systems. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our cluster candidates at z = 0.565. At the preferred photometric redshift of 0.5, we estimate the cluster mass M500 ≈ 0.8 ± 0.2 × 1015 M. We here demonstrate a powerful technique to find massive clusters at intermediate (z ≳ 0.5) redshifts using a cross-correlation between Planck and WISE data, with high-resolution CARMA-8 follow-up. We also use the combined capabilities of Planck and CARMA-8 to obtain a dramatic reduction, by a factor of several, in parameter uncertainties.


IPAC Authors

Ranga-Ram Chary

Senior Scientist