Probing the Origin of Low Frequency Radio Emission in PG Quasars with the uGMRT -- I

We present the results from 685 MHz observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) of 22 quasars belonging to the PG quasar sample. Only four sources reveal extended radio structures on $\sim$10-30 kpc scales, while the rest are largely a combination of a radio core unresolved at the uGMRT resolution of $\sim$3-5 arcsec, surrounded by diffuse emission on few kpc to $\sim$10 kpc scales. A few sources reveal signatures of barely resolved jets and lobes in their spectral index images. On the basis of their position on the radio-IR correlation as well as the spectral index images created using similar resolution GHz-frequency data from the VLA, we find that the radio emission in the 2 radio-loud (RL) quasars and nearly one-third of the radio-quiet (RQ) quasars is AGN dominated whereas the remaining sources appear to have significant contributions from stellar-related processes along with the AGN. While the 2 RL sources exhibit inverted spectral index in their cores, the RQ sources exhibit a range of spectral indices ranging from flat to steep ($-0.1\lesssim\alpha_{R}\lesssim-1.1$) indicating the presence of unresolved jets/lobes or winds. Except for a significant correlation between the 685 MHz radio luminosity and the Eddington ratio, we do not find strong correlations between other 685 MHz radio properties and black hole (BH) properties in the RQ PG sources. This lack of correlations could be explained by the contribution of stellar-related emission, or radio emission from previous AGN activity episodes which may not be related to the current BH activity state.