The Chandra Cygnus OB2 Legacy Survey: Design and X-ray Point Source Catalog

TL;DR

The Chandra Cygnus OB2 Legacy Survey provides a comprehensive X-ray point source catalog of the largest young and massive star association within 2 kpc, using a carefully designed imaging strategy to ensure uniform coverage.

Contribution

This paper introduces a novel survey design with overlapping pointings to achieve uniform X-ray coverage of Cygnus OB2 and presents a catalog of 8,000 X-ray sources.

Findings

Catalog of 8,000 X-ray point sources

Survey design with 36 overlapping pointings

Uniform exposure over the central 0.5 deg^2

Abstract

The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated 65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer onboard the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg^2 of the Cyg OB2 association with an effective exposure of 120ks and an outer 0.35 deg^2 area with an exposure of 60ks. Here we describe the survey design and observations, the data reduction and source detection, and present a catalog of 8,000 X-ray point sources. The survey design employs a grid of 36 heavily (~50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg^2. The full X-ray catalog is described here and is made available online.