The MeerKAT Galaxy Clusters Legacy Survey: star formation in massive clusters at 0.15 < z < 0.35

Abstract

We investigate dust-unbiased star formation rates (SFRs) as a function of the environment in 20 massive clusters ($M_{200}\gt 4\times 10^{14}\, {\rm M}_{\odot }$) between 0.15 < $z$ < 0.35 using radio luminosities (L_1.4GHz) from the recently released MeerKAT Galaxy Cluster Legacy Survey catalogue. We use optical data from the Dark Energy Camera Legacy Survey to estimate photo-$z$s and assign cluster membership. We observe a steady decline in the fraction (f_SF) of star-forming galaxies from 2R₂₀₀ to the cluster centres in our full cluster sample, but notice a significant difference in f_SF gradients between clusters hosting large-scale extended radio emission in the form of haloes and relics (associated with ongoing merger activity) and non-radio-halo/relic hosting clusters. For star-forming galaxies within R₂₀₀, the f_SF in clusters hosting radio haloes and relics (0.148 ± 0.016) is $\approx 23{{\ \rm per\ cent}}$ higher than in non-radio-halo/relic hosting clusters (0.120 ± 0.011). We observe a 3σ difference between the total SFR normalized by cluster mass for non-radio-halo/relic hosting clusters (21.5 ± 1.9 M_⊙yr^-1/10¹⁴M_⊙) and for clusters with radio haloes and relics (26.1 ± 1.4 M_⊙yr^-1/10¹⁴M_⊙). There is a ≈4× decline in the mass normalized total SFR of clusters for galaxies with SFR above the luminous infrared galaxies (LIRGs) SFR limit at our redshift slice, corresponding to 2 Gyr in lookback time. This is consistent with the rapid decline in SF activity with decreasing redshift amongst cluster LIRGs seen by previous studies using infrared-derived SFR.