Contribution from unresolved discrete sources to the extragalactic gamma-ray background (EGRB)

Debbijoy Bhattacharya, Parameswaran Sreekumar, Reshmi Mukherjee

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


The origin of the extragalactic gamma-ray background (EGRB) is still an open question, even nearly forty years after its discovery. The emission could originate either from truly diffuse processes or from unresolved point sources. Although the majority of the 271 point sources detected by EGRET (Energetic Gamma Ray Experiment Telescope) are unidentified, of the identified sources, blazars are the dominant candidates. Therefore, unresolved blazars may be considered the main contributor to the EGRB, and many studies have been carried out to understand their distribution, evolution and contribution to the EGRB. Considering that γ-ray emission comes mostly from jets of blazars and that the jet emission decreases rapidly with increasing jet to line-of-sight angle, it is not surprising that EGRET was not able to detect many large inclination angle active galactic nuclei (AGNs). Though Fermi could only detect a few large inclination angle AGNs during the first three months of its survey, it is expected to detect many such sources in the near future. Since non-blazar AGNs are expected to have higher density as compared to blazars, these could also contribute significantly to the EGRB. In this paper, we discuss contributions from unresolved discrete sources including normal galaxies, starburst galaxies, blazars and off-axis AGNs to the EGRB.

Original languageEnglish
Pages (from-to)1205-1214
Number of pages10
JournalResearch in Astronomy and Astrophysics
Issue number11
Publication statusPublished - 2009

All Science Journal Classification (ASJC) codes

  • Space and Planetary Science
  • Astronomy and Astrophysics


Dive into the research topics of 'Contribution from unresolved discrete sources to the extragalactic gamma-ray background (EGRB)'. Together they form a unique fingerprint.

Cite this