The Fermi blazars' divide based on the diagnostic of the SEDs peak frequencies

TL;DR

This study classifies Fermi blazars into two groups based on their SED peak frequencies, revealing a divide related to their emission processes and spectral characteristics.

Contribution

It introduces a diagnostic method using SED peak frequencies to distinguish blazar types and their dominant emission mechanisms.

Findings

Fermi blazars are divided into two groups based on SED peak frequencies.

Objects below the SSC region are HBL or LBL/IBL, not Compton dominated.

Objects above the SSC region are FSRQs or IBLs/LBLs with significant Compton dominance.

Abstract

We have studied the quasi-simultaneous Spectral Energy Distributions (SED) of 48 LBAS blazars, detected within the three months of the LAT Bright AGN Sample (LBAS) data taking period, combining Fermi and Swift data with radio NIR-Optical and hard-X/gamma-ray data. Using these quasi-simultaneous SEDs, sampling both the low and the high energy peak of the blazars broad band emission, we were able to apply a diagnostic tool based on the estimate of the peak frequencies of the synchrotron (S) and Inverse Compton (IC) components. Our analysis shows a Fermi blazars' divide based on the peak frequencies of the SED. The robust result is that the Synchrotron Self Compton (SSC) region divides in two the plane were we plot the peak frequency of the synchrotron SED vs the typical Lorentz factor of the electrons most contributing to the synchrotron emission and to the inverse Compton process. Objects within or below this region, radiating likely via the SSC process, are high-frequency-peaked BL Lac object (HBL), or low/intermediate-frequency peaked BL Lac object (LBL/IBL). All of the IBLs/LBLs within or below the SSC region are not Compton dominated. The objects lying above the SSC region, radiating likely via the External radiation Compton (ERC) process, are Flat Spectrum Radio Quasars and IBLs/LBLs. All of the IBLs/LBLs in the ERC region show a significant Compton dominance.