The Far-Infrared-Radio Correlation in MS0451-03

Résumé : We present a multi-wavelength analysis of star-forming galaxies in the massive cluster MS0451.6-0305 at z $\sim$ 0.54 to shed new light on the evolution of the far-infrared-radio relationship in distant rich clusters. We have derived total infrared luminosities for a spectroscopically confirmed sample of cluster and field galaxies through an empirical relation based on $Spitzer$ MIPS 24 $\mu$m photometry. The radio flux densities were measured from deep Very Large Array 1.4 GHz radio continuum observations. We find the ratio of far-infrared to radio luminosity for galaxies in an intermediate redshift cluster to be $q_{\rm FIR}$ = 1.80$\pm$0.15 with a dispersion of 0.53. Due to the large intrinsic dispersion, we do not find any observable change in this value with either redshift or environment. However, a higher percentage of galaxies in this cluster show an excess in their radio fluxes when compared to low redshift clusters ($27^{+23}_{-13}\%$ to $11\%$), suggestive of a cluster enhancement of radio-excess sources at this earlier epoch. In addition, the far-infrared-radio relationship for blue galaxies, where $q_{\rm FIR}$ = 2.01$\pm$0.14 with a dispersion of 0.35, is consistent with the predicted value from the field relationship, although these results are based on a sample from a single cluster.