Correlations among Jet, Accretion Disk, and Broad Line Region of Flat Spectrum Radio Quasars
Abstract
The SEDs of 18 GeV FSRQs are collected and compiled from literature, in which both the jet emission and the accretion disk radiation can be observed, in order to investigate the correlations among their jet power (Pjet), accretion disk luminosity (Ldisk), and luminosity of broad line region (BLR, LBLR). On the basis of the SED fits with the jet radiation and accretion disk radiation models, we calculate Pjet and Ldisk. No correlation between Pjet with either Ldisk or LBLR is found. With a sub-sample of LBLR for 13 GeV FSRQs, it is observed that LBLR is strongly correlated with their Ldisk. We also study the BLR covering factors of the GeV FSRQs in our sample, averagely which are smaller than that of the large samples of radio-loud and radio-quiet quasars. Pjet of some GeV FSRQs is higher than Ldisk, but Pjet of all the GeV FSRQs is lower than the accretion power of black hole (BH), which is estimated by Mc2=Ldisk/0.1, indicating that the total accretion power of BH is sufficient to drive the jets in these sources; however the uncorrelation between Ldisk and Pjet of the GeV FSRQs may suggest that their jets are launched by the BZ process via extracting the rotational energy of BH. Using the LBLR-Ldisk relation of the GeV FSRQs, we estimate Ldisk of a BL Lac sample with their LBLR. A comparison of LBLR and Eddington ratio (Ldisk/LEdd) among BL Lacs, very radio-loud NLS1 galaxies, and FSRQs is also presented. It is found that along with the BL Lac-NLS1-FSRQ sequence LBLR and Ldisk/LEdd increase, which may correspond to the change of the accretion disk structure and the transformation of the dominant mechanism for jet launching. This is also consistent with the division of their parent populations, i.e., low-excitation radio galaxies and high-excitation radio galaxies.