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The extragalactic gamma-ray sky in the Fermi era

  • Francesco Massaro
  • David J. Thompson
  • Elizabeth C. Ferrara
Review Article

Abstract

The Universe is largely transparent to \(\gamma \)-rays in the GeV energy range, making these high-energy photons valuable for exploring energetic processes in the cosmos. After 7 years of operation, the Fermi  Gamma-ray Space Telescope has produced a wealth of information about the high-energy sky. This review focuses on extragalactic \(\gamma \)-ray sources: what has been learned about the sources themselves and about how they can be used as cosmological probes. Active galactic nuclei (blazars, radio galaxies, Seyfert galaxies) and star-forming galaxies populate the extragalactic high-energy sky. Fermi observations have demonstrated that these powerful non-thermal sources display substantial diversity in energy spectra and temporal behavior. Coupled with contemporaneous multifrequency observations, the Fermi results are enabling detailed, time-dependent modeling of the energetic particle acceleration and interaction processes that produce the \(\gamma \)-rays, as well as providing indirect measurements of the extragalactic background light and intergalactic magnetic fields. Population studies of the \(\gamma \)-ray source classes compared to the extragalactic \(\gamma \)-ray background place constraints on some models of dark matter. Ongoing searches for the nature of the large number of \(\gamma \)-ray sources without obvious counterparts at other wavelengths remain an important challenge.

Keywords

Gamma rays Extragalactic astronomy Active galactic nuclei Quasars BL Lac objects Background light 

Abbreviations

AGN(s)

Active galactic nucleus(i)

AGU

Active galaxy of uncertain type

BCU

Blazar candidate of uncertain type

CGRO

Compton Gamma-Ray Observatory

CSS

Compact steep spectrum radio source

DM

Dark matter

EBL

Extragalactic gamma-ray background light

EGB

Extragalactic gamma-ray background

EC

External Compton

FR

Fanaroff–Riley radio source class

FSRQ

Flat-spectrum radio quasar

GRB

Gamma-ray burst

HBL

High-frequency peaked BL Lac object

HSP

High-synchrotron peaked BL Lac object

QSO

Quasi-stellar object (a.k.a. quasar)

RG

Radio galaxy

RLNLSy1

Radio-loud narrow-line Seyfert of type 1

SED

Spectral energy distribution

SFR

Star formation rate

SSC

Synchrotron self-Compton

SSRQ

Steep spectrum radio quasar

UGS

Unidentified/unassociated gamma-ray source

1FGL

First Fermi gamma-ray LAT point source catalog

2FGL

Second Fermi gamma-ray LAT point source catalog

3FGL

Third Fermi gamma-ray LAT point source catalog

1LAC

First Fermi LAT AGN catalog

2LAC

Second Fermi LAT AGN catalog

3LAC

Third Fermi LAT AGN catalog

2PC

Second LAT pulsar catalog

3EG

Third EGRET catalog

CRATES

The combined radio all-sky targeted eight GHz survey

LBAS

LAT bright AGN sample

Roma-BZCAT

Roma-multifrequency blazar catalog

WGS

WISE gamma-ray strip

WIBRaLS

WISE blazar-like radio-loud source catalog

AGILE

Astrorivelatore Gamma a Immagini Leggero

ATCA

Australia Telescope Compact Array

BAT

Burst Alert Telescope

CGRH

Cosmic gamma-ray horizon

COS-B

Celestial Observation Satellite-B

CTA

Cherenkov Telescope Array

EGRET

Energetic Gamma-Ray Experiment Telescope

FAVA

Fermi all-sky variability analysis

FoV

Field of view

GASP

GLAST-AGILE support program

GBM

Gamma-Ray Burst Monitor

GLAST

Gamma-Ray Large Area Space Telescope

HESS

High-Energy Stereoscopic System

IBIS

Imager on-Board the INTEGRAL Satellite

INTEGRAL

INTErnational Gamma-Ray Astrophysics Laboratory

IR

Infrared energy range

LAT

Large Area Telescope

LR

Likelihood ratio

MAGIC

Major Atmospheric Gamma-Ray Imaging Cherenkov Telescope

MOJAVE

Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments

OSO-3

Orbiting Solar Observatory-3

PSF

Point spread function

SAS-2

Small Astronomy Satellite-2

SMARTS

Small and Medium Aperture Research Telescope System

SOAR

Southern Astrophysical Research Telescope

UV

Ultraviolet energy range

VERITAS

Very Energetic Radiation Imaging Telescope Array System

VLA

Very Large Array

VLBA

Very Long Baseline Array

VLBI

Very long baseline interferometry

WEBT

Whole Earth Blazar Telescope

Notes

Acknowledgments

This review would not have been possible without the dedicated efforts of scientists, engineers, and technicians who have made the Fermi Gamma-ray Space Telescope mission so successful. We extend thanks to all those who contributed. Special thanks to Justin Finke, Filippo D’Ammando and Seth Digel for valuable comments on the manuscript. F. Massaro wishes to thank M. Ajello, R. D’Abrusco, D. Gasparrini, M. Giroletti, L. Latronico, N. Masetti, A. Paggi, H. Smith and G. Tosti for their support during the last 4 years spent working on Fermi blazars. The work by is supported by the Programma Giovani Ricercatori—Rita Levi Montalcini—Rientro dei Cervelli (2012). This review is also supported by the NASA grants NNX12AO97G and NNX13AP20G. Part of this work is based on archival data, software or on-line services provided by the ASI Science Data Center. This research has made use of data obtained from the high-energy Astrophysics Science Archive Research Center (HEASARC) provided by NASA’s Goddard Space Flight Center; the SIMBAD database operated at CDS, Strasbourg, France; the NASA/IPAC Extragalactic Database (NED) operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. TOPCAT (http://www.star.bris.ac.uk/~mbt/topcat/) (Taylor 2005) for the preparation and manipulation of the tabular data and the images. The Aladin Java applet (http://aladin.u-strasbg.fr/aladin.gml) was used to create the finding charts reported in this paper (Bonnarel 2000). It can be started from the CDS (Strasbourg, France), from the CFA (Harvard, USA), from the ADAC (Tokyo, Japan), from the IUCAA (Pune, India), from the UKADC (Cambridge, UK), or from the CADC (Victoria, Canada).

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Francesco Massaro
    • 1
  • David J. Thompson
    • 2
  • Elizabeth C. Ferrara
    • 2
  1. 1.Dipartimento di FisicaUniversità degli Studi di TorinoTurinItaly
  2. 2.NASA Goddard Space Flight CenterGreenbeltUSA

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