Surveys of Clumps, Cores, and Condensations in Cygnus X. I. A New Catalog of ∼0.1 pc Massive Dense Cores

Abstract

Using infrared to (sub)millimeter data from Spitzer, Herschel, the James Clerk Maxwell Telescope, and the IRAM 30 m telescope, we conducted an unbiased survey of the massive dense cores (MDCs) in the Cygnus X molecular cloud complex, aimed at characterizing the physical conditions of high-mass star formation (HMSF) at ∼0.1 pc scales. We created 5° × 6° images of the 70-1200 μm dust continuum, gas column density, and dust temperature of Cygnus X. A spatial relation between the dense regions (A _v ≥ 15) and the developed H II regions was found, indicating the impact of the latter on the global structures of Cygnus X. With a 35 M _⊙ mass threshold implied by HMSF signposts, we identified 151 MDCs with sizes of ∼0.1 pc, masses of 35-1762 M _⊙, and temperatures of 8-35 K. Our MDC sample is statistically complete in Cygnus X and is three times larger than that in Motte et al. The MDCs were classified into IR-bright/IR-quiet ones based on their midinfrared fluxes, and a large “IR-quiet” proportion (90%) was found in our sample. Two possible scenarios were proposed to interpret accelerated HMSF and the incapability of HMSF of the IR-quiet MDCs. We also found 26 starless MDCs by their lack of compact emissions at 21-70 μm wavelengths, of which the most massive ones are probably the best candidates of initial HMSF sites in Cygnus X.