The Two Micron All Sky Survey at IPAC

Soares & Bica used the 2MASS Point Source Catalog from the Second Incremental Data Release to study the stellar clusters embedded in the nebulae NGC 2327 and bright-rimmed cloud (BRC) 27 in the Canis Majoris R1 molecular cloud (at left). The resulting JHKs color-color and color-magnitude diagrams for these two clusters are shown below. The emission-line star LkH 221 (filled square) is the brightest object within NGC 2327. Several studies have analyzed this star, but none before this one had focused on a related surrounding star cluster or stellar group. These clusters contain objects that are still forming, and theoretical isochrones for main sequence stars (dashed line) alone are inadequate. For this reason, the authors employed 2MASS photometry for a known cluster in likely a similar phase of evolution, the Trapezium cluster in Orion (open colored diamonds, solid line), as a template for comparison. From this, the authors derive fundamental properties for these two clusters (filled circles): Both clusters are at a distance of 1.2 kpc; the mean visual extinction toward NGC 2327 is AV=5.5 mag, while toward BRC 27, it is AV=6.5 mag; and, both clusters are coeval and quite young, with ages of about 1.5 Myr. 2MASS is ideal for studying the embedded stellar content in molecular clouds. Detailed analysis of the Point Source Catalog sources reveals very young objects in the pre-main-sequence stage and enables detections of Ks excesses, which originate in dust disks or envelopes of contracting objects.

Three-color JHKs composite 2MASS Atlas Image mosaic

NGC 2327
Color-color diagram	Color-magnitude diagram
BRC 27
Color-color diagram	Color-magnitude diagram

Original figures ©The European Southern Observatory (ESO)

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