Very-High Energy Observations of the Galactic Center Region by Veritas in 2010-2012

Abstract

The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) γ-ray observations. Potential sources of GeV/TeV γ-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g., Sgr A East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above ∼2.5 TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic, and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.

Review of Dark Matter searches with Cherenkov telescopes

“…The detected signal was therefore concluded to most likely be of non-dark matter origin, and limits to σ v of the order of 10 −24 -10 −23 cm 3 s −1 could be inferred. Later observations by MAGIC [23] and VERITAS [24] are in agreement with these conclusions.…”

TeV gamma rays from Galactic Center pulsars

“…The HESS, VERITAS and MAGIC Collaborations have each reported the detection of very high-energy (VHE) gamma-ray emission from the direction of the Galactic Center, extending to energies of ∼30-50 TeV [1][2][3][4][5][6][7][8]. When this emission was initially identified, it was suggested that it may originate from the Milky Way's central supermassive black hole, Sgr A * [9][10][11][12].…”

Similarity and diversity of black holes - view from the Very High Energies

“…Galactic center is a strong and well established source of VHE γ-rays (Aharonian et al 2004, Albert et al 2006a, Archer et al 2014. It was already early suggested that the point source in the galactic centre would correspond to a central black hole (Aharonian et al 2004), but as there are also other candidates, such as supernova remnant Sgr A East, the question of direct emission of the black hole in the center of our galaxy is not yet resolved.…”