Detection of TeV Gamma-Rays from extended sources with Milagro

TL;DR

This paper reports the first detection of TeV gamma-rays from the inner Galactic plane, an extended source coincident with an EGRET source, and extended emission from the Cygnus region, using the Milagro water Cherenkov detector.

Contribution

It introduces the Milagro detector's capabilities and reports novel detections of extended TeV gamma-ray sources in the Galactic plane.

Findings

Detection of TeV gamma-rays from the inner Galactic plane

Identification of an extended TeV source coincident with EGRET source 3EG J0520+2556

Observation of extended TeV emission from the Cygnus region

Abstract

The Milagro gamma-ray observatory employs a water Cherenkov detector to observe extensive air showers produced by high-energy particles impacting in the Earth's atmosphere. A 4800 m$^{2}$ pond instrumented with 723 8" PMTs detects Cherenkov light produced by secondary air-shower particles. An array of 175 4000 liter water tanks surrounding the central pond detector was recently added, extending the physical area of the Milagro observatory to 40,000 m$^{2}$ and substantially increasing the sensitivity of the detector. Because of its wide field of view and high duty cycle, Milagro is ideal for monitoring the northern sky almost continuously ($>$90% duty cycle) in the 100 GeV to 100 TeV energy range. Here we discuss the first detection of TeV gamma-rays from the inner Galactic plane region. We also report the detection of an extended TeV source coincident with the EGRET source 3EG J0520+2556, as well as the observation of extended TeV emission from the Cygnus region of the Galactic plane.