Massive Star Formation in the Cygnus-X Region
Résumé
Massive stars shape galaxy evolution and nearby star formation through feedback mechanisms, yet many aspects of how they form and how they evolve towards the zero-age-main-sequence are still a mystery. The Cygnus-X region contains many massive young stellar objects (YSOs), and at only a distance of 1.7 kpc, this complex is ideal for studying massive star formation. We have observed a list of 25 sources with the IRS, basing our source selection on candidates previously identified in the Cygnus-X Spitzer Legacy Survey using the MIPS and IRAC instruments, the IRAM 1.2 mm survey of the region, and combining these with some older infrared surveys. Common features in the spectra include molecular hydrogen lines tracing shocks at the HII region boundary, polycyclic aromatic hydrocarbon emission in the HII region, and carbon dioxide ice absorption in the envelope. Silicate absorption is also present, allowing us to determine interstellar extinction to the sources. Neon and sulfur forbidden emission lines from ionized gas were also detected. Using the objects' spectral energy distributions, along with line flux ratios derived from the new IRS spectra, we fit models of YSOs to derive stellar mass, age, and temperature, as well as total luminosity of the system, envelope accretion rate of mass onto the stars, and other physical parameters. This work is supported in part by the NSF REU and DOD ASSURE programs under NSF grant no. 0754568 and by the Smithsonian Institution.