Toggle Main Menu Toggle Search

Open Access padlockePrints

Probing the origin of low-frequency radio emission in PG quasars with the uGMRT - I

Lookup NU author(s): Dr Christopher HarrisonORCiD


Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


© 2020 The Author(s). We present the results from 685 MHz observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) of 22 quasars belonging to the Palomar-Green (PG) quasar sample. Only four sources reveal extended radio structures on ∼10-30 kpc scales, while the rest are largely a combination of a radio core unresolved at the uGMRT resolution of ∼3-5 arcsec, surrounded by diffuse emission on few kpc to ∼10 kpc scales. A few sources reveal signatures of barely resolved jets and lobes in their spectral index images that are created using the 685 MHz uGMRT data and similar resolution GHz-frequency data from the Very Large Array. On the basis of their position on the radio-IR correlation as well as the spectral index images, we find that the radio emission in the two radio-loud (RL) quasars and nearly one-third of the radio-quiet (RQ) quasars is active galactic nucleus (AGN) dominated whereas the remaining sources appear to have significant contributions from stellar-related processes along with the AGN. While the two RL sources exhibit inverted spectral index in their cores, the RQ sources exhibit a range of spectral indices varying from flat to steep (-0.1 ≳ αR ≳ -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 that may not be related to the current BH activity state.

Publication metadata

Author(s): Silpa S, Kharb P, Ho LC, Ishwara-Chandra CH, Jarvis ME, Harrison C

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2020

Volume: 499

Issue: 4

Pages: 5826-5839

Print publication date: 01/12/2020

Online publication date: 28/09/2020

Acceptance date: 22/09/2020

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press


DOI: 10.1093/MNRAS/STAA2970


Altmetrics provided by Altmetric