A Very High Energy γ-Ray Survey toward the Cygnus Region of the Galaxy

Abstract

We present results from deep observations toward the Cygnus region using 300 hr of very high energy (VHE) γ -ray data taken with the VERITAS Cerenkov telescope array and over 7 yr of high-energy γ -ray data taken with the Fermi satellite at an energy above 1 GeV. As the brightest region of diffuse γ -ray emission in the northern sky, the Cygnus region provides a promising area to probe the origins of cosmic rays. We report the identification of a potential Fermi -LAT counterpart to VER J2031+415 (TeV J2032+4130) and resolve the extended VHE source VER J2019+368 into two source candidates (VER J2018+367* and VER J2020+368*) and characterize their energy spectra. The Fermi -LAT morphology of 3FGL J2021.0+4031e (the Gamma Cygni supernova remnant) was examined, and a region of enhanced emission coincident with VER J2019+407 was identified and jointly fit with the VERITAS data. By modeling 3FGL J2015.6+3709 as two sources, one located at the location of the pulsar wind nebula CTB 87 and one at the quasar QSO J2015+371, a continuous spectrum from 1 GeV to 10 TeV was extracted for VER J2016+371 (CTB 87). An additional 71 locations coincident with Fermi -LAT sources and other potential objects of interest were tested for VHE γ -ray emission, with no emission detected and upper limits on the differential flux placed at an average of 2.3% of the Crab Nebula flux. We interpret these observations in a multiwavelength context and present the most detailed γ -ray view of the region to date.