A Spitzer View of Star Formation in the Cyngus X North Complex

We present new images and photometry of the massive star forming complex Cygnus X obtained with the Infrared Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS) on board the Spitzer Space Telescope. A combination of IRAC, MIPS, UKIRT Deep Infrared Sky Survey (UKIDSS), and Two Micron All Sky Survey (2MASS) data are used to identify and classify young stellar objects. Of the 8,231 sources detected exhibiting infrared excess in Cygnus X North, 670 are classified as Class I and 7,249 are classified as Class II. Using spectra from the FAST spectrograph at the Fred L. Whipple Observatory and Hectospec on the MMT, we spectrally typed 536 sources in the Cygnus X complex to identify the massive stars. We find that YSOs tend to be grouped in the neighborhoods of massive B stars (spectral types B0 to B9). We present a minimal spanning tree analysis of clusters in two regions in Cygnus X North. The fraction of infrared excess sources that belong to clusters with greater or equal to 10 members is found to be 50-70%. Most Class II objects lie in dense clusters within blown out H II regions, while Class I sources tend to reside in more filamentary structures along the bright-rimmed clouds, indicating possible triggered star formation.
Accepted for publication in The Astrophysical Journal, v720 n1, Sep 2010. Sponsored in part by the National Science Foundation Research Experiences for Undergraduates (REU) and Department of Defense Awards to Stimulate and Support Undergraduate Research Experiences (ASSURE) programs under Grant no. 0754568 and by the Smithsonian Institution.