Swift BAT, Fermi LAT, and the Blazar Sequence

Abstract

Using public \fermi LAT and \swift BAT observations, we constructed the first sample of blazars selected at both hard X-rays and gamma-rays. Studying its spectral properties, we find a luminosity dependence of the spectral slopes at both energies. Specifically, luminous blazars, generally classified as FSRQs, have {\it hard} continua in the medium-hard X-ray range but {\it soft} continua in the LAT gamma-ray range (photon indices ${\Gamma }_X$ \ltsima 2 and ${\Gamma }_G$ \gtsima 2), while lower luminosity blazars, classified as BL Lacs, have opposite behavior, i.e., {\it soft} X-ray and {\it hard} gamma-ray continua (${\Gamma }_X$ \gtsima 2.4 and ${\Gamma }_G<2$). The trends are confirmed by detailed Monte Carlo simulations explicitly taking into account the observational biases of both instruments. Our results support the so-called ``blazar sequence'' which was originally based on radio samples of blazars and radio luminosities. We also argue that the X-ray-to-gamma-ray continua of blazars may provide independent insights into the physical conditions around the jet, complementing/superseding the ambiguities of the traditional classification based on optical properties.

Accepted by ApJ

References in corpus (12)

• Fermi Large Area Telescope Bright Gamma-ray Source List
• The power of blazar jets
• Bright AGN Source List from the First Three Months of the Fermi Large Area Telescope All-Sky Survey
• The blazar sequence: a new perspective
• Swift BAT Survey of AGN
• The Fermi blazars divide
• The Evolution of Swift/BAT blazars and the origin of the MeV background
• On the relation between AGN gamma-ray emission and parsec-scale radio jets
• A Connection Between Apparent VLBA Jet Speeds and Initial Active Galactic Nucleus Detections Made by the Fermi Gamma-ray Observatory
• The Blazar Sequence: Validity and Predictions
• Testing the blazar spectral sequence: X-ray selected blazars
• Fermi/LAT discovery of gamma-ray emission from the flat-spectrum radio quasar PKS 1454-354

Cited by in corpus (13)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• Similarity of the Optical-IR and Gamma-Ray Time Variability of Fermi Blazars
• Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources
• Bethe-Heitler emission in BL Lacs: filling the gap between X-rays and $\gamma$-rays
• The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey
• Hard X-ray properties of NuSTAR blazars
• Blazars at the Cosmic Dawn
• Basic properties of Fermi blazars and the "blazar sequence"
• Radio-Optical-Gamma-Ray properties of MOJAVE AGN detected by Fermi/LAT
• Fermi/LAT Observations of Swift/BAT Seyferts: on the Contribution of Radio-quiet AGN to the Extragalactic Gamma-ray Background
• High energy emission component, population, and contribution to the extragalactic gamma-ray background of gamma-ray emitting radio galaxies
• Gamma-Ray Burst Afterglows as Analogues of High Frequency-Peaked BL Lac Objects
• Multiple inverse Compton scatterings and the blazar sequence