THE FERMI-LAT HIGH-LATITUDE SURVEY: SOURCE COUNT DISTRIBUTIONS AND THE ORIGIN OF THE EXTRAGALACTIC DIFFUSE BACKGROUND

By A. Abdo, M. Ackermann, M. Ajello, E. Antolini, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, B. Baughman, K. Bechtol and 160 more. 2010

189 citations recorded by the source corpus.

This is the first of a series of papers aimed at characterizing the populations detected in the high-latitude sky of the Fermi-LAT survey. In this work, we focus on the intrinsic spectral and flux properties of the source sample. We show that when selection effects are properly taken into account, Fermi sources are on average steeper than previously found (e.g., in the bright source list) with an average photon index of 2.40 ± 0.02 over the entire 0.1–100 GeV energy band. We confirm that flat spectrum radio quasars have steeper spectra than BL Lacertae objects with an average index of 2.48 ± 0.02 versus 2.18 ± 0.02. Using several methods, we build the deepest source count distribution at GeV energies, deriving that the intrinsic source (i.e., blazar) surface density at F100 ⩾ 10−9 ph cm−2 s−1 is 0.12+0.03−0.02 deg−2. The integration of the source count distribution yields that point sources contribute 16(±1.8)% (±7% systematic uncertainty) of the GeV isotropic diffuse background. At the fluxes currently reached by LAT, we can rule out the hypothesis that pointlike sources (i.e., blazars) produce a larger fraction of the diffuse emission.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/cd6d51ace1749598c6f44b83296d610ddbfea5be

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Citations in the corpus

THE COSMOLOGICAL IMPACT OF LUMINOUS TeV BLAZARS. I. IMPLICATIONS OF PLASMA INSTABILITIES FOR THE INTERGALACTIC MAGNETIC FIELD AND EXTRAGALACTIC GAMMA-RAY BACKGROUND (2011, methodology): “This has been measured at high energies by EGRET (Sreekumar et al. 1998; Strong et al. 2004) and more recently strongly constrained between 200MeV and 100GeV byFermi (Abdo et al. 2010b,a).”
THE LUMINOSITY FUNCTION OF FERMI-DETECTED FLAT-SPECTRUM RADIO QUASARS (2011, methodology): “This is done in order to reproduce the inherent systematic uncertainty of ﬁtting the curved spectrum of a source with a power law (Abdo et al. 2010a).”
Sensitivity projections for dark matter searches with the Fermi large area telescope (2016, methodology): “32: Left: Flux distribution of simulated blazars using the intrinsic dN/dS of the 1FGL catalog [326] (blue points) together with a fit (black solid line) and the 1σ uncertainty band (cyan).”
Optimized dark matter searches in deep observations of Segue 1 with MAGIC (2013, background): “Fermi-LAT is contributing to the indirect dark matter searches in other ways as well: one of its first striking results was the discovery that AGNs are not the main source of the diffuse extragalactic background, as it was assumed, but instead can account for just a small fraction of it (∼16%) [141]”
THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV (2014, methodology): “This change contributes to a reduced integrated IGRB intensity above 100 MeV of 7.2± 0.6× 10−6 ph cm−2 s−1 sr−1 in comparison to the 1.03± 0.17× 10−5 ph cm−2 s−1 sr−1 reported in Abdo et al. (2010b).”
GeV OBSERVATIONS OF STAR-FORMING GALAXIES WITH THE FERMI LARGE AREA TELESCOPE (2012, methodology): “…by harder gamma-ray spectra relative to quiescent galaxies of the Local Group (Acero et al. 2009; Acciari et al. 2009; Abdo et al. 2010a; Ohm et al. 2011), and that global gammaray luminosities of galaxies likely scale quasi-linearly with SFRs (e.g. Abdo et al. 2010a,d; Lenain & Walter 2011).”
GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND? (2010, background): “H E ] 1 8 O ct 2 01 0 Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50 degrees above and below the Galactic center, with a width of about 40 degrees in longitude.”
THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND AND IMPLICATIONS FOR DARK MATTER ANNIHILATION (2015, methodology): “Blazars, which constitute the largest population detected by the LAT, were found to contribute ∼20–30% of the unresolved EGB (Abdo et al. 2010c; Singal et al. 2012; Harding & Abazajian 2012; Di Mauro et al. 2014), and a larger fraction in some models (Stecker & Venters 2011).”
THE COSMIC EVOLUTION OF FERMI BL LACERTAE OBJECTS (2013, methodology): “At GeV-TeV energies BL Lacs are characterized by a harder spectrum than FSRQs and are found to outnumber (by a factor >3) the latter particularly above 10GeV (Abdo et al. 2010c).”
THE FIRST CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE (2010, methodology): “This source is associated with M82, also known as NGC 3034 and 3C 231, a starburst galaxy previously detected by the LAT (Abdo et al. 2010d).”
THE FIRST FERMI-LAT CATALOG OF SOURCES ABOVE 10 GeV (2013, methodology): “The fifth radio galaxy, Cen A, is exceptional because of its proximity and also a presence of γ -ray emitting giant lobes clearly resolved with the LAT (Abdo et al. 2010d).”
Active galactic nuclei: what’s in a name? (2017, methodology): “This includes 415 FSRQs (all of the LSP type), 657 BL Lacs (mostly of the HSP type), and 402 blazars of uncertain type (assumed to be blazars because of their radio to γ -ray SED but with no optical spectrum yet available to classify them as FSRQs or BL Lacs).”
The Nine Lives of Cosmic Rays in Galaxies (2015, methodology): “The Galactic centre itself shows two bright coincident γ-ray sources, above 1 GeV with Fermi -LAT and up to 40 TeV with H.E.S.S. (Chernyakova et al. 2011), with matching, but complex spectra, and whose origin is unclear at present.”
CONTRIBUTION OF GAMMA-RAY-LOUD RADIO GALAXIES’ CORE EMISSIONS TO THE COSMIC MeV AND GeV GAMMA-RAY BACKGROUND RADIATION (2011, methodology): “Their average photon index at 0.1–10 GeV is ∼2.4, which is the same as that of the GeV EGRB (Abdo et al. 2010e) and blazars (Abdo et al. 2010f).”