2025A&A...697A.150S

Context. Galaxies in overdense environments, such as clusters, present predominantly quenched populations up to z∼1. This suggests that environmental mechanisms suppress the star formation in these galaxies for the majority of cosmic history. At low redshifts, galaxies in rich group and cluster environments frequently show a radio emission excess in the IR-radio correlation, but this has yet to be confirmed at high redshifts, when environmental effects begin to strongly affect the evolution of cluster galaxies.
Aims. We investigate the effect of the environment on the infrared and radio emission of cluster galaxies during the transition epoch at 1<z<2 when they first start to quench consistently in the majority of galaxy clusters.
Methods. We considered a sample of 129 cluster member galaxies from 11 massive clusters at a confirmed redshift of 1.0-1.8 from the IRAC Shallow Cluster Survey (ISCS), the IRAC Distant Cluster Survey (IDCS), and new 3 GHz images from the Karl G. Jansky Very Large Array (VLA). We calculated the IR-radio correlation slope parameter, q, in order to identify differences in the ratios of IR to radio of cluster galaxies and field galaxy comparison samples at different redshifts. Active galactic nuclei (AGNs) were identified and analyzed to search for any effect on the IR-radio correlation. The correlation parameter values were also compared by the Kolmogorov-Smirnov test with field galaxies.
Results. Our comparison of the IR-radio correlation in cluster galaxies to the control sample of field galaxies reveals a marginally to modestly significant difference in the correlation slope parameter at the ∼2σ-3σ level. A split of the clusters into low-redshift (1<z<1.37) and high-redshift (1.37<z<1.8) bins indicates a more significant difference in the correlation parameter in the lower-redshift cluster subsample, where widespread quenching begins. We find no difference in the IR-radio correlation between the high-z cluster and field samples, which is consistent with environmental effects on galaxy properties. These are less consistently observed at z≳1.4. Our results suggest no evidence of any difference in the IR-radio correlation between galaxies that lie closer to the cluster center (projected radius R<1 Mpc) and galaxies in the cluster outskirts (R>1 Mpc). We find no difference in the IR-radio correlation between galaxies that host AGNs and non-active star-forming galaxies either. This suggests that our AGNs are overwhelmingly radio quiet and therefore do not affect the results we described above. We conclude that further investigations based on larger datasets are needed to constrain the impact of the cluster environment on the IR-radio correlation better.