A simplified view of blazars: clearing the fog around long‐standing selection effects

By P. Giommi, P. Padovani, G. Polenta, S. Turriziani, V. D’Elia, S. Piranomonte. 2011

256 citations recorded by the source corpus.

We propose a scenario where blazars are classified as flat-spectrum radio quasars (FSRQs), BL Lacs, low synchrotron, or high synchrotron peaked objects according to a varying mix of the Doppler boosted radiation from the jet, the emission from the accretion disk, the broad line region, and the light from the host galaxy. In this framework the peak energy of the synchrotron power (ν S ) in blazars is independent of source type and of radio luminosity. We test this new approach, which builds upon unified schemes, using extensive Monte Carlo simulations and show that it can provide simple answers to a number of long-standing issues including, amongst others, the different cosmological evolution of BL Lacs selected in the radio and X-ray bands, the larger ν S peak values observed in BL Lacs, the fact that high synchrotron peaked blazars are always of the BL Lac type, and the existence of FSRQ/BL Lac transition objects. Objects so far classified as BL Lacs on the basis of their observed weak, or undetectable, emission lines are of two physically different classes: intrinsically weak lined objects, more common in X-ray selected samples, and heavily diluted broad lined sources, more frequent in radio selected samples, which explains some of the confusion in the literature. We also show that strong selection effects are the main cause of the diversity observed in radio and X-ray samples, and that the correlation between luminosity and ν S , that led to the proposal of the “blazar sequence”, is also a selection effect arising from the comparison of shallow radio and X-ray surveys, and to the fact that high ν S peak - high radio power objects have never been considered because their redshift is not measurable.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/ae58d2f8601ebae44628e7b322b3b1b9a61f03fc

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Citations in the corpus

THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS (2013, background): “The optical spectra of BL Lac objects are power-law dominated indicating either especially strong non-thermal continuum (jet aligned very close to our line of sight) or unusually weak thermal disk/broad line emission (plausibly attributed to low accretion activity; Giommi et al. 2012).”
MOJAVE. X. PARSEC-SCALE JET ORIENTATION VARIATIONS AND SUPERLUMINAL MOTION IN ACTIVE GALACTIC NUCLEI (2013, background): “Giommi et al. (2012) discuss the possibility of quasars masquerading as low-equivalent line width BL Lacs due to the swamping of their emission lines by highly Doppler boosted optical synchrotron emission.”
Properties of flat-spectrum radio-loud Narrow-Line Seyfert 1 Galaxies (2014, background): “We noted some BL Lacs with strong accretion disk, in the region occupied by FSRQs: these are the so-called “intruders” (Ghisellini et al. 2011, Giommi et al. 2012).”
The faint radio sky: radio astronomy becomes mainstream (2016, background): “…mention the fact that there appears to be a consensus on the strong and positive evolution of FSRQs/SSRQs/FR IIs (i.e., radiative-mode RL AGN), and on the weak, if any, evolution of BL Lacs/FR Is (i.e., jet-mode RL AGN) (see also Padovani et al., 2007; Giommi et al., 2012, and references therein).”
SPECTROSCOPY OF THE LARGEST EVER γ-RAY-SELECTED BL LAC SAMPLE (2013, background): “Thus the distinction between the traditional BLL and the FSRQ is sensitive to the precise state and orientation of the jet (e.g. Giommi et al. 2012) and, indeed, variations in jet power or direction can bring individual sources in or out of the BLL class (S12).”
Active galactic nuclei: what’s in a name? (2017, background): “To this purpose Giommi, Padovani and collaborators published a series of papers (Giommi et al. 2012, 2013; Padovani and Giommi 2015; Giommi and Padovani 2015), where, through a detailed Monte Carlo approach, called the blazar simplified view (BSV), they showed that the widely different statistical…”
The Fermi blazar sequence (2017, background): “As discussed in the introduction, Giommi et al. (2012) proposed the “simplified scenario” for blazars, completely alternative to the blazar sequence.”