English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Cygnus OB2 is the nearest example of a massive star forming region,containing over 50 O-type stars and hundreds of B-type stars. We have analysedthe properties of young stars in two fields in Cyg OB2 using the recentlypublished deep catalogue of Chandra X-ray point sources with complementaryoptical and near-IR photometry. Our sample is complete to 1 Msun (excluding Aand B-type stars that do not emit X-rays), making this the deepest study of thestellar properties and star formation history in Cyg OB2 to date. From Siess etal. (2000) isochrone fits to the near-IR color-magnitude diagram, we deriveages of 3.5 (+0.75/-1.0) and 5.25 (+1.5/-1.0) Myrs for sources in the twofields, both with considerable spreads around the pre-MS isochrones. Thepresence of a stellar population somewhat older than the present-day O-typestars, also fits in with the low fraction of sources with inner circumstellardisks (as traced by the K-band excess) that we find to be very low, butappropriate for a population of age ~5 Myrs. We also find that the region lacksa population of highly embedded sources that is often observed in young starforming regions, suggesting star formation in the vicinity has declined. Wemeasure the stellar mass functions in this limit and find a power-law slope ofGamma = -1.09 +/- 0.13, in good agreement with the global mean value estimatedby Kroupa (2002). A steepening of the slope at higher masses is observed andsuggested as due to the presence of the previous generation of stars that havelost their most massive members. Finally, combining our mass function and anestimate of the radial density profile of the association suggests a total massof Cyg OB2 of ~3 x 10^4 Msun, similar to that of many of our Galaxy's mostmassive star forming regions.

The Massive Star Forming Region Cygnus OB2. II. Integrated Stellar Properties and the Star Formation History