Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M87
2009 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 1, 55-60 p.Article in journal (Refereed) Published
We report the Fermi Large Area Telescope (LAT) discovery of high-energy (MeV/GeV) γ-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10σ in 10 months of all-sky survey data. Following the detections of Cen A and Per A, this makes M87 the third radio galaxy seen with the LAT. The faint point-like γ-ray source has a >100 MeV flux of 2.45 (±0.63) × 10–8 photons cm–2 s–1 (photon index = 2.26 ± 0.13) with no significant variability detected within the LAT observation. This flux is comparable with the previous EGRET upper limit (<2.18 × 10–8 photons cm–2 s–1, 2σ), thus there is no evidence for a significant MeV/GeV flare on decade timescales. Contemporaneous Chandra and Very Long Baseline Array data indicate low activity in the unresolved X-ray and radio core relative to previous observations, suggesting M87 is in a quiescent overall level over the first year of Fermi-LAT observations. The LAT γ-ray spectrum is modeled as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the core. The resultant SSC spectrum extrapolates smoothly from the LAT band to the historical-minimum TeV emission. Alternative models for the core and possible contributions from the kiloparsec-scale jet in M87 are considered, and cannot be excluded.
Place, publisher, year, edition, pages
2009. Vol. 707, no 1, 55-60 p.
galaxies: active, galaxies: individual: M87, galaxies: jets, gamma rays: observations, radiation mechanisms: non-thermal
Astronomy, Astrophysics and Cosmology Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-33758DOI: 10.1088/0004-637X/707/1/55ISI: 000272162900004ISBN: 0004-637XOAI: oai:DiVA.org:su-33758DiVA: diva2:283662