Speaker
Description
Utilising the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Early Science data from the COSMOS field, we select radio-detected galaxies down to a radio flux density limit of 2 μJy. Source detection was performed using the PYTHON Blob Detector and Source Finder (pybdsf) catalogue. Cross-matching these detections with multiwavelength photometric data in the X-rays, optical, and infrared allows us to select the radio active galactic nuclei (AGN) host galaxies and star-forming galaxies (SFGs) across the redshift range 0 ≲ z ≲ 6. Using MAGPHYS, we fit the spectral energy distribution for the selected radio galaxies to obtain their stellar masses (M$_*$) and star formation rates (SFR). Our key objective is to calibrate the SFR-1.4 GHz radio luminosity (L$_{\rm 1.4 ~ GHz}$) relation for non-jetted AGN (i.e., radio-quiet AGN), radio-loud AGN (RL AGN), and SFGs. We obtain a positive correlation for non-jetted AGN, with an average slope of 0.81, while RL AGN deviates significantly from the linear trend observed for non-jetted and SFGs, particularly at L$_{\rm 1.4 ~ GHz}$ > 10$^{23}$ W/Hz. Our findings indicate that at z < 0.5, the radio emission observed in non-jetted AGN is driven by star formation processes within the host galaxies, following a relation like SFGs. However, at higher redshift (z > 0.5), the radio-FIR correlation becomes shallower, suggesting that while FIR luminosity (tracing star formation) increases significantly, the corresponding increase in radio luminosity is slower. This suggests that in the early universe, non-jetted AGN experience increased star formation, but the radio emission is suppressed. This is likely due to young stellar populations that have not yet evolved to produce supernova remnants.
