Herschel and ALMA Observations of Massive SZE-selected Clusters

Wu, John F.; Aguirre, Paula; Baker, Andrew J.; Devlin, Mark J.; Hilton, Matt; Hughes, John P.; Infante, Leopoldo; Lindner, Robert R.; Sifón, Cristóbal

doi:10.3847/1538-4357/aaa0dc

Authors

RefereedArticle

Abstract

We present new Herschel observations of four massive, Sunyaev-Zel’dovich effect-selected clusters at 0.3≤slant z≤slant 1.1, two of which have also been observed with the Atacama Large Millimeter/submillimeter Array (ALMA). We detect 19 Herschel/Photoconductor Array Camera and Spectrometer (PACS) counterparts to spectroscopically confirmed cluster members, five of which have redshifts determined via CO (4-3) and [C I] ({}³{P}₁{--}{}³{P}₀) lines. The mean [C I]/CO line ratio is 0.19 ± 0.07 in brightness temperature units, consistent with previous results for field samples. We do not detect significant stacked ALMA dust continuum or spectral-line emission, implying upper limits on mean interstellar medium (H₂ + H I) and molecular gas masses. An apparent anticorrelation of {L}_{IR} with clustercentric radius is driven by the tight relation between star formation rate and stellar mass. We find an average specific star formation rate of log(sSFR/yr^-1) = -10.36, which is below the {SFR}{--}{M}_* correlation measured for field galaxies at similar redshifts. The fraction of infrared-bright galaxies (IRBGs; {log}({L}_{IR}/{L}_☉)> 10.6) per cluster and average sSFR rise significantly with redshift. For CO detections, we find {f}_{gas}∼ 0.2, comparable to those of field galaxies, and gas depletion timescales of about 2 Gyr. We use radio observations to distinguish active galactic nuclei (AGNs) from star-forming galaxies. At least four of our 19 Herschel cluster members have {q}_{IR}< 1.8, implying an AGN fraction {f}_{AGN}≳ 0.2 for our PACS-selected sample.