MYStIX First Results: Spatial Structures of Massive Young Stellar Clusters

Abstract

Observations of the spatial distributions of young stars in star-forming regions can be linked to the theory of clustered star formation using spatial statistical methods. The MYStIX project provides rich samples of young stars from the nearest high-mass star-forming regions. Maps of stellar surface density reveal diverse structure and subclustering. Young stellar clusters and subclusters are fit with isothermal spheres and ellipsoids using the Bayesian Information Criterion to estimate the number of subclusters. Clustering is also investigated using Cartwright and Whitworth's Q statistic and the inhomogeneous two-point correlation function. Mass segregation is detected in several cases, in both centrally concentrated and fractally structured star clusters, but a few clusters are not mass segregated.

BAYESIAN MATCHING FOR X-RAY AND INFRARED SOURCES IN THE MYStIX PROJECT

“…A central goal of the Massive Young Star-Forming Complex Study in Infrared and X-rays (MYStIX; Feigelson et al 2013) is to obtain a rich and high-quality census of stars belonging to complex star formation regions within 4 kpc of the Sun. A first step is to obtain catalogs of X-ray, near-infrared and mid-infrared sources from single waveband surveys (see Kuhn et al 2013a;King et al 2013;Kuhn et al 2013b). The X-ray selection is effective in discriminating young stars from older Galactic field stars, while the infrared photometry is needed to characterize the properties of the young stars: luminosity, surface temperature, absorption, and infrared-excess from a circumstellar dusty disk.…”

“…Within the MYStIX data reduction pipeline (see Fig-ure 3 in Feigelson et al 2013) matching lies between the creation of the X-ray and IR catalogs (Kuhn et al 2013a;King et al 2013;Kuhn et al 2013b), and classification with the naive Bayes classifier (Broos et al 2013). It is worth emphasizing that there is a clear split between the observational information used in the matching process (the observed magnitude distributions of the IR counterparts and field stars) and the astrophysical understanding (colors and magnitudes for particular types classes of object) used in the Bayes classifier.…”

THE MYStIX WIDE-FIELD NEAR-INFRARED DATA: OPTIMAL PHOTOMETRY IN CROWDED FIELDS

“…Thus we never use the J H K data alone to search for disks. Its combination with our Spitzer data presented in Kuhn et al (2013b) makes the powerful tool for the identification of young stars with disks we describe in Povich et al (2013). Finally, once a young star is reliably identified, the J -band data combined with the measurement of the extinction which relies on the Spitzer data, gives a measure of the photospheric emission.…”