Herschel-ATLAS: Far-infrared properties of radio-loud and radio-quiet quasars

TL;DR

This study compares the far-infrared properties of radio-loud and radio-quiet quasars, revealing correlations between radio and FIR luminosities, and suggesting a link between radio jets and star formation at lower accretion rates.

Contribution

It provides the first detailed analysis of FIR properties in radio-loud versus radio-quiet quasars using stacking and grey-body models.

Findings

Significant correlation between FIR and radio luminosities in radio-loud quasars.

Radio-loud quasars have lower dust temperatures than radio-quiet quasars.

Radio-loud quasars at lower optical luminosities show higher FIR luminosities.

Abstract

We have constructed a sample of radio-loud and radio-quiet quasars from the Faint Im- ages Radio Sky at Twenty-one centimetres (FIRST) and the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), over the H-ATLAS Phase 1 Area (9h, 12h and 14.5h). Using a stacking analysis we find a significant correlation between the far-infrared luminosity and 1.4-GHz luminosity for radio-loud quasars. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution while for radio-quiet quasars no partial correlation is found. Using a single-temperature grey-body model we find a general trend of lower dust temperatures in the case of radio-loud quasars comparing to radio-quiet quasars. Also, radio-loud quasars are found to have almost constant mean values of dust mass along redshift and optical luminosity bins. In addition, we find that radio-loud quasars at lower optical luminosities tend to have on average higher FIR and 250-micron luminosity with respect to radio-quiet quasars with the same optical luminosites. Even if we use a two-temperature grey-body model to describe the FIR data, the FIR luminosity excess remains at lower optical luminosities. These results suggest that powerful radio jets are associated with star formation especially at lower accretion rates.