General physical properties of bright Fermi blazars

Abstract

We studied all blazars of known redshift detected by the Fermi satellite during its first three months survey. For the majority of them, pointed Swift observations ensures a good multiwavelength coverage, enabling us to to reliably construct their spectral energy distributions (SED). We model the SEDs using a one-zone leptonic model and study the distributions of the derived interesting physical parameters as a function of the observed gamma-ray luminosity. We confirm previous findings concerning the relation of the physical parameters with source luminosity which are at the origin of the blazar sequence. The SEDs allow to estimate the luminosity of the accretion disk for the majority of broad emitting line blazars, while for the line-less BL Lac objects in the sample upper limits can be derived. We find a positive correlation between the jet power and the luminosity of the accretion disk in broad line blazars. In these objects we argue that the jet must be proton-dominated, and that the total jet power is of the same order of (or slightly larger than) the disk luminosity. We discuss two alternative scenarios to explain this result.Comment: 23 pages, 20 figures, accepted for publication in MNRAS. Very minosr change

Basic properties of Fermi blazars and the ‘blazar sequence’

“…The result is consistent with other authors (e.g. Rawlings & Saunders 1991;Falcke & Biermann 1995;Serjeant, Rawlings & Maddox 1998;Cao & Jiang 1999;Wang, Luo & Ho 2004;Liu, Jiang & Gu 2006;Xie et al 2007;Ghisellini, Tavecchio & Ghirlanda 2009a;Ghisellini et al 2009bGhisellini et al , 2010Ghisellini et al , 2011Gu, Cao & Jiang 2009;Sbarrato et al 2012). Linear regression is applied to analyze the correlation between broad line luminosity and jet power, and we obtain log LBLR ∼ (0.94 ± 0.12) log Pjet for Fermi blazars and log LBLR ∼ (0.39 ± 0.12) log Pjet for non-Fermi blazars.…”

“…Ghisellini et al (2009b) studied general physical properties of bright Fermi blazars. They modeled the spectral energy distribution (SED) using a one zone leptonic model and confirmed the relations of the physical parameters with source luminosity which are at the origin of the blazar sequence.…”

Gamma rays from blazars

“…For FSRQ we have some control on the accretion power through the observed thermal components and it is thus possible to compare the power carried by the jet with that advected by the accreting material. The comparison show that, on average, jets carry a power larger than that associated to the infalling accretion flow, suggesting that the source of the jet power is the BH spin [24,26], as supported by recent GR-MHD simulations [27].…”

“…The "canonical" choice is to locate the emission region within the BLR, thus exploiting for the IC emission the dense radiation field produced by the photoionized gas. Representative values of the magnetic field are larger than those of BL Lacs, in the range 1-10 G, but Doppler factors and radius are similar [24,25]. For FSRQ we have some control on the accretion power through the observed thermal components and it is thus possible to compare the power carried by the jet with that advected by the accreting material.…”

“…For FSRQ, the physical conditions inferred for the emission regions are in better agreement with the magnetic reconnection scenario than those of BL Lac jets. In fact, equipartition between magnetic fields and relativistic particles (predicted for the magnetic reconnection model) generally holds for FSRQ [24]. However, a still acute problem could remain, since the jets do not appear to be magnetically dominated at the distances assumed for the emission [26,93], a conditio sine qua non for the model to work (magnetic reconnection models generally assume that the magnetic luminosity of the jet is >10 times larger than the kinetic one).…”