Detection of diffuse TeV gamma-ray emission from the nearby starbust galaxy NGC 253

Abstract

We report the TeV gamma-ray observations of the nearby normal spiral galaxy NGC 253. At a distance of ∼2.5 Mpc, NGC 253 is one of the nearest starburst galaxies. This relative closeness, coupled with the high star formation rate in the galaxy, make it a good candidate TeV gamma-ray source. Observations were carried out in 2000 and 2001 with the CANGAROO-II 10m imaging atmospheric Cerenkov telescope. TeV gamma-ray emission is detected at the ∼11σ level with a flux of (7.8 ± 2.5) × 10⁻¹² cm⁻² s⁻¹ at energies >0.5 TeV. The data indicate that the emission region is broader than the point spread function of our telescope.