2016ApJ...819..117X

We performed a multiwavelength study toward the infrared dark cloud (IRDC) G34.43+0.24. New maps of ¹³CO J = 1-0 and C¹⁸O J = 1-0 were obtained from the Purple Mountain Observatory (PMO) 13.7 m radio telescope. At 8 µm (Spitzer-IRAC), IRDC G34.43+0.24 appears to be a dark filament extended by 18' along the north-south direction. Based on the association with the 870 µm and C¹⁸O J = 1-0 emission, we suggest that IRDC G34.43+0.24 should not be 18' in length, but extend to 34'. IRDC G34.43+0.24 contains some massive protostars, UC H ii regions, and infrared bubbles. The spatial extend of IRDC G34.43+0.24 is about 37 pc, assuming a distance of 3.7 kpc. IRDC G34.43+0.24 has a linear mass density of ∼1.6x10³ M_☉/pc, which is roughly consistent with its critical mass to length ratio. The turbulent motion may help stabilize the filament against the radial collapse. Both infrared bubbles N61 and N62 show a ringlike structure at 8 µm. In particular, N61 has a double-shell structure that has expanded into IRDC G34.43+0.24. The outer shell is traced by 8 µm and ¹³CO J = 1-0 emission, while the inner shell is traced by 24 µm and 20 cm emission. We suggest that the outer shell (9.9x10⁵ years) is created by the expansion of H ii region G34.172+0.175, while the inner shell (4.1 ∼ 6.3x10⁵ years) may be produced by the energetic stellar wind of its central massive star. From the GLIMPSE I catalog, we selected some Class I sources with an age of ∼10⁵ years. These Class I sources are clustered along the filamentary molecular cloud.