OB Associations at the Upper End of the Milky Way Luminosity Function
arXiv:1211.3362 · doi:10.1088/0004-637X/766/2/135
Abstract
The Milky Way's most luminous, young and massive (M > 10^4 Msun) star clusters and OB associations have largely evaded detection despite knowledge of their surrounding H II regions. We search for these clusters and associations within the 40 star forming complexes from Rahman & Murray in the 13 most luminous WMAP free-free emission sources of the Galaxy. Selecting for objects with the dust-reddened colors of OB stars, we identify new candidate associations using the 2MASS point source catalog. In 40 star forming complexes searched, 22 contain cluster/association candidates with sizes and masses in the range of 3' - 26' and 10^{2.3} - 10^{5} Msun. Of the 22 candidates, at least 7 have estimated masses > 10^4 Msun, doubling the number of such massive clusters known in the Galaxy. Applying our method to a statistically similar set of test locations, we estimate that 3.0 +/- 0.6 of our 22 candidate associations are unrelated to the star forming complexes. In addition, the apparent extinctions of our candidate associations correlate well with the predictions from a Galactic model. These facts, along with the clear detection of a known OB association and the previous spectral verification of one cluster found by this method, validate our method. Only one of the searched WMAP sources remains without a candidate. In 8 of the most luminous WMAP sources, the candidate associations can account for the observed free-free flux. With our new compilation, the Galactic census of young, massive stellar associations may now be about half complete.
25 pages, 14 figures. To appear in ApJ
References in corpus (15)
- The UKIRT Infrared Deep Sky Survey (UKIDSS)
- The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
- UBVJHK synthetic photometry of Galactic O stars
- The mass function of young star clusters in spiral galaxies
- A systematic survey for infrared star clusters with |b|<20deg using 2MASS
- A massive cluster of Red Supergiants at the base of the Scutum-Crux arm
- The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics observations
- Discovery of an Extraordinarily Massive Cluster of Red Supergiants
- Interstellar Extinction Law toward the Galactic Center II: V, J, H, and Ks Bands
- Star Cluster Demographics. I. A General Framework and Application to the Antennae Galaxies
- Intermediate to low-mass stellar content of Westerlund 1
- Rotational Velocities For B0-B3 Stars in 7 Young Clusters: Further Study of the Relationship between Rotation Speed and Density in Star-Forming Regions
- A third red supergiant rich cluster in the Scutum-Crux Arm
- A Census of the Carina Nebula -- II. Energy Budget and Global Properties of the Nebulosity
- Massive Star Forming Regions in the Galaxy using the Spitzer GLIMPSE Survey