Title: The Lx–Luv–Lradio relation and corona–disc–jet connection in optically selected radio-loud quasars
Speaker: Dr. Shifu Zhu (PSU)
Time: 8:30am, Nov. 3 (Tuesday)
Abstract: Radio-loud quasars (RLQs) are more X-ray luminous than predicted by the Lx-Luv relation for radio-quiet quasars (RQQs). The excess X-ray emission depends on the radio-loudness parameter (R) and radio spectral slope (alpha_r). We construct a uniform sample of 729 optically selected RLQs with high fractions of X-ray detections and alpha_r measurements. We find that steep-spectrum radio quasars (SSRQs) follow a quantitatively similar Lx-Luv 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) are generally more X-ray luminous than SSRQs at given Luv 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 compare critically 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. We suggest that RLQs and RQQs are in different accretion states, similar to those of microquasars when their ballistic jets are either active or quenched. 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 processes in the vicinity of SMBHs, probably associated with the magnetic flux/topology instead of black-hole spin, are controlling the radio-loudness of quasars.