The $L_{\mathrm{x}}$-$L_{\mathrm{uv}}$-$L_{\mathrm{radio}}$ relation and corona-disk-jet connection in optically selected radio-loud quasars

Abstract

Radio-loud quasars (RLQs) are more X-ray luminous than predicted by the X-ray-optical/UV relation (i.e. $L_{\mathrm{x}}\propto L_{\mathrm{uv}}^3$) for radio-quiet quasars (RQQs). The excess X-ray emission depends on the radio-loudness parameter ($R$) and radio spectral slope ($\hat{I}{\pm }_{\mathrm{r}}$). We construct a uniform sample of 729 optically selected RLQs with high fractions of X-ray detections and $\hat{I}{\pm }_{\mathrm{r}}$ measurements.We find that steep-spectrum radio quasars (SSRQs; $\hat{I}{\pm }_{\mathrm{r}}\le -0.5$) follow a quantitatively similar $L_{\mathrm{x}}\propto L_{\mathrm{uv}}^3$ relation as that for RQQs, suggesting a common coronal origin for the X-ray emission of both SSRQs and RQQs. However, the corresponding intercept of SSRQs is larger than that for RQQs and increases with $R$, suggesting a connection between the radio jets and the configuration of the accretion flow. Flat-spectrum radio quasars (FSRQs; $\hat{I}{\pm }_{\mathrm{r}}>-0.5$) are generally more X-ray luminous than SSRQs at given $L_{\mathrm{uv}}$ and $R$, likely involving more physical processes. The emergent picture is different from that commonly assumed where the excess X-ray emission of RLQs is attributed to the jets. We thus perform model selection to comparecritically these different interpretations, which prefers the coronal scenario with a corona-jet connection. A distinct jet component is likely important for only a small portion of FSRQs.The corona-jet, disk-corona, and disk-jet connections of RLQs are likely driven by independent physical processes. Furthermore, the corona-jet connection implies that small-scale processesin the vicinity of SMBHs, probably associated with the magnetic flux/topology instead of black-hole spin, are controlling the radio-loudness of quasars.

30 pages, 17 figures, published in MNRAS