The blazar sequence 2.0

TL;DR

This paper updates the observational 'blazar sequence' using Fermi data, revealing relationships between jet power and accretion, and highlighting diversity in low-luminosity blazars' spectral energy distributions.

Contribution

It provides an empirical update to the blazar sequence based solely on data, without theoretical modeling, showing new insights into blazar properties and SED diversity.

Findings

Jet and accretion power are related.

The blazar sequence retains its properties with less gamma-ray dominance.

Low luminosity blazars show large SED shape dispersion.

Abstract

I discuss the spectral energy distribution (SED) of all blazars with redshift detected by the {\it Fermi} satellite and listed in the 3LAC catalog. I will update the so called "blazar sequence" from the phenomenological point of view, with no theory or modelling. I will show that: i) pure data show that jet and accretion power are related; ii) the updated blazar sequence maintains the properties of the old version, albeit with a less pronounced dominance of the $\gamma$--ray emission; iii) at low bolometric luminosities, two different type of objects have the same high energy power: low black hole mass flat spectrum radio quasars and high mass BL Lacs. Therefore, at low luminosities, there is a very large dispersion of SED shapes; iv) in low power BL Lacs, the contribution of the host galaxy is important. Remarkably, the luminosity distribution of the host galaxies of BL Lacs are spread in a very narrow range; v) a simple sum of two smoothly joining power laws can describe the blazar SEDs very well.