Observation of gamma-ray emission from the galaxy M87 above 250 GeV with VERITAS

  • V. A. Acciar
  • , M. Beilicke
  • , G. Blaylock
  • , S. M. Bradbury
  • , J. H. Buckley
  • , V. Bugaev
  • , Y. Butt
  • , O. Celik
  • , A. Cesarini
  • , L. Ciupik
  • , P. Cogan
  • , P. Colin
  • , W. Cui
  • , M. K. Daniel
  • , C. Duke
  • , T. Ergin
  • , A. D. Falcone
  • , S. J. Fegan
  • , J. P. Finley
  • , G. Finnegan
  • P. Fortin, L. F. Fortson, K. Gibbs, G. H. Gillanders, J. Grube, R. Guenette, G. Gyuk, D. Hanna, E. Hays, J. Holder, D. Horan, S. B. Hughes, M. C. Hui, T. B. Humensky, A. Imran, P. Kaaret, M. Kertzman, D. B. Kieda, J. Kildea, A. Konopelko, H. Krawczynski, F. Krennrich, M. J. Lang, S. LeBohec, K. Lee, G. Maier, A. McCann, M. McCutcheon, J. Millis, P. Moriarty, R. Mukherjee, T. Nagai, R. A. Ong, D. Pandel, J. S. Perkins, M. Pohl, J. Quinn, K. Ragan, P. T. Reynolds, H. J. Rose, M. Schroedter, G. H. Sembroski, A. W. Smith, D. Steele, S. P. Swordy, A. Syson, J. A. Toner, L. Valcarcel, V. V. Vassiliev, S. P. Wakely, J. E. Ward, T. C. Weekes, A. Weinstein, R. J. White, D. A. Williams, S. A. Wissel, M. D. Wood, B. Zitzer

Research output: Contribution to journalArticlepeer-review

Abstract

The multiwavelength observation of the nearby radio galaxy M87 provides a unique opportunity to study in detail processes occurring in active galactic nuclei from radio waves to TeV γ-rays. Here we report the detection of γ-ray emission above 250 GeV from M87 in spring 2007 with the VERITAS atmospheric Cerenkov telescope array and discuss its correlation with the X-ray emission. The γ-ray emission is measured to be pointlike with an intrinsic source radius less than 4.5′. The differential energy spectrum is fitted well by a power-law function: dΦ/dE = (7.4 ± 1.3stat ± 1.5sys)(£/TeV) (-2.31±0.17stat±0.2sys)10-9 m-2 s-1 TeV-1. We show strong evidence for a year-scale correlation between the γ-ray flux reported by TeV experiments and the X-ray emission measured by the ASM RXTE observatory, and discuss the possible short-timescale variability. These results imply that the γ-ray emission from M87 is more likely associated with the core of the galaxy than with other bright X-ray features in the jet.

Original languageEnglish
Pages (from-to)397-403
Number of pages7
JournalAstrophysical Journal
Volume679
Issue number1
DOIs
Publication statusPublished - 20 May 2008
Externally publishedYes

Keywords

  • Galaxies: individual (M87, NGC 4486, Virgo A)
  • Gamma rays: observations

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