The Massive Star Forming Region, Cygnus OB2

TL;DR

This study catalogs 1696 X-ray sources in Cygnus OB2, analyzing stellar ages, disk fractions, and the initial mass function, and introduces a future deep X-ray survey of the region.

Contribution

It provides a comprehensive X-ray source catalog, age estimates for stellar populations, and insights into disk fractions and the initial mass function in Cygnus OB2.

Findings

Stellar populations are 3.5 and 5.25 Myrs old.

Disk fraction is unusually low, possibly due to older star contamination.

Initial mass function slope is Gamma = -1.27.

Abstract

We present results from a catalogue of 1696 X-ray point sources detected in the massive star forming region (SFR) Cygnus OB2, the majority of which have optical or near-IR associations. We derive ages of 3.5 and 5.25 Myrs for the stellar populations in our two fields, in agreement with recent studies that suggest that the central 1-3 Myr OB association is surrounded and contaminated by an older population with an age of 5-10 Myrs. The fraction of sources with proto-planetary disks, as traced by K-band excesses, are unusually low. Though this has previously been interpreted as due to the influence of the large number of OB stars in Cyg OB2, contamination from an older population of stars in the region could also be responsible. An initial mass function is derived and found to have a slope of Gamma = -1.27, in agreement with the canonical value. Finally we introduce the recently approved Chandra Cygnus OB2 Legacy Survey that will image a 1 square degree area of the Cygnus OB2 association to a depth of 120 ks, likely detecting ~10,000 stellar X-ray sources.