The Blazar Main Sequence

Abstract

We propose a sequence (the Blazar main sequence, BMS) that links the two main components of the Blazar class, namely, the Flat Spectrum Radio Quasars and the BL Lacertae objects, and yields all their distinctive features in a correlated way. In this view, both type of sources are centered on a supermassive Kerr hole close to maximal spin that produces a relativistic jet observed close to the axis, and on the associated accretion disk that emits more isotropically. But the FSRQs are energized by accretion at rates dm/dt ~ 1, and are dominated by the disk components (thermal and electrodynamic jet-like component) which provide outputs in excess of L ~ 10^46 erg/s. On the other hand, accretion levels dm/dt << 1 are enough to energize the BL Lacs; here the radiation is highly non-thermal and the power partly contributed by the rotational energy of the central Kerr hole, with the latter and the disk together sustaining L ~ 10^44 erg/s in the jet frame for several Gyrs. If so, we expect the BL Lacs to show quite different evolutionary signatures from the FSRQs, and in particular, number counts close to the Euclidean shape, or flatter if the sources make a transition to the BL Lac from a FSRQ mode. In addition, for lower dm/dt along the BMS, we expect the large scale electric fields to be less screened out, and to accelerate fewer particles to higher energies with non-thermal radiations at higher frequencies; so in moving from FSRQs to BL Lacs these non-thermal radiations will peak at frequencies inversely correlated with the disk output. For the BL Lacs such dependence implies increased scatter when one tries a correlation with the total ouput. At its endpoint, the BMS suggests widespread objects that are radiatively silent, but still efficient in accelerating cosmic rays to ultra high energies.Comment: 26 pages, 2 eps figures, revised version #2, accepted for pubblication in Ap

Jet/accretion and unification for FSRQs/FRII and BL Lac objects/FRI radio galaxies

“…Since η is not the sample for all objects, log η may contribute to the dispersion around the linear relation ). Our results are also consistent with the results of D'Elia & Cavaliere (2001), Xie et al (2003), Cavaliere & D'Elia (2002), and Böttcher & Dermer (2002). Rawlings & Saunders (1991) found a close relationship between total kinetic power and narrow line luminosity for FRII and FRI radio galaxy.…”

“…Dissipation in the jet occurs outside the BLR (if it exists at all). In other words, the quasars evolves into BL Lacs (Cavaliere & D'Elia 2002). Cao (2002) got that the the evolutionary sequence of blazars is from a flat-spectrum radio quasars to a low-energy-peaked BL Lac object to a highenergy-peaked BL Lac object.…”

From the ‘blazar sequence' to unification of blazars and radio galaxies

“…So the synchrotron ⋆ E-mail: ynzx@yeah.net and Compton peaks shift to lower frequencies. Various lines of evidence support the blazar sequence (Georganopoulos et al 2001;Cavaliere & D'Elia 2002;Maraschi & Tavecchio 2003;Xie et al 2007;Maraschi et al 2008;Ghisellini et al 2009Ghisellini et al , 2010Abdo et al 2010a;Chen & Bai 2011;Sambruna et al 2010;Finke et al 2013;Chen 2014). But many contrary opinions have been presented (Giommi, Menna & Padovani 1999;Caccianiga & Marcha 2004;Padovani et al 2003;Anton & Browne 2005;Nieppola et al 2006Nieppola et al , 2008Padovani 2007;Giommi et al 2012).…”

Gamma rays from blazars

“…The phenomenological division between FSRQ and BL Lac objects can be interpreted as reflecting a more fundamental difference in the nature of the accretion flow in the two kind of sources, ultimately regulated by the accretion rate of the infalling material, e.g. [9,10]. In FSRQ, which show bright thermal features (optical lines) and, in some cases, a bump at optical-UV frequencies (thought to mark the direct emission from the hot accreting gas), the accretion likely occurs through a radiatively efficient (optically thick) accretion disk.…”

“…Farther out (1-10 pc), dust grains -likely organized in the geometrical shape of a torus -intercepts a fraction ξ ≈ 0.5 of the disk continuum, reprocessing it as thermal IR emission (with temperature close to that corresponding to the sublimation of dust, T ≈ 10 3 K). On the other hand, the lack of strong thermal components in BL Lac optical spectra is generally interpreted as an evidence that the accretion flow present in these sources is radiatively inefficient, as expected for accretion rates much smaller than that of quasars, when the accretion flow assumes the structure of an ADAF/ADIOS [9]. This scheme could allows one to explain the difference between the GeV γ-ray spectra of BL Lacs (generally displaying hard spectra) and those of FSRQ (characterized by soft -photon index larger than 2 -spectra), as the effect of the different radiative losses characterizing the high-energy electrons in the two kind of sources [10].…”