Montage Used To Study The Structure of the Star-forming Cluster RCW 38

E. Winston et al. (2011) report that they used  Montage in their recent paper “The Structure of the Star-forming Cluster RCW 38.” This was a multiwavelength investigation that used Spitzer, Chandra and 2MASS data that probed the spatial distribution of the young stellar population in this high mass star-formation region.

The RCW 38 region observed with IRAC on Spitzer. The plot shows a three-band false color image of the cluster, where the mosaic at each wavelength was created from the four epochs of data combined using the Montage mosaicing software. The field shows the overlap region of the four IRAC bands. Blue is 3.6μm, green is 4.5μm, and red is 8.0μm. The reddish hue at 8.0μm is due mainly to diffuse PAH emission. Emission from shocked hydrogen is visible in green. The outline of the Chandra ACIS-I field of view is overlaid as a white square.

"The RCW 38 region observed with IRAC on Spitzer. The plot shows a three-band false color image of the cluster, where the mosaic at each wavelength was created from the four epochs of data combined using the Montage mosaicing software. The field shows the overlap region of the four IRAC bands. Blue is 3.6μm, green is 4.5μm, and red is 8.0μm. The reddish hue at 8.0μm is due mainly to diffuse PAH emission. Emission from shocked hydrogen is visible in green. The outline of the Chandra ACIS-I field of view is overlaid as a white square." From Winston et al (2011)

They found: “..624 YSOs: 23 class 0/I and 90 flat spectrum protostars, 437 Class II stars, and 74 Class III stars. We also identify 29 (27 new) O star candidates over the IRAC field. Seventy-two stars exhibit IR-variability, including seven class 0/I and 12 flat spectrum YSOs. A further 177 tentative candidates are identified by their location in the IRAC [3.6] vs. [3.6]-[5.8] cmd. We find strong evidence of subclustering in the region. Three subclusters were identified surrounding the central cluster, with massive and variable stars in each subcluster. The central region shows evidence of distinct spatial distributions of the protostars and pre-main sequence stars. A previously detected IR cluster, DB2001 Obj36, has been established as a subcluster of RCW 38. This suggests that star formation in RCW 38 occurs over a more extended area than previously thought. The gas to dust ratio is examined using the X-ray derived hydrogen column density, NH and the K-band extinction, and found to be consistent with the diffuse ISM, in contrast with Serpens & NGC1333. We posit that the high photoionising flux of massive stars in RCW 38 affects the agglomeration of the dust grains.”

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