2004ApJS..154..328M

Examination of early, in-orbit checkout (IOC) images of a portion of the Galactic plane obtained by the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope revealed the presence of an extended emission nebula with internal structure. The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) data show this nebula, located at l∼42° and b∼0°.5, contains bright point sources and two nonstellar regions. Ancillary data sets were used to help reveal the nature of this nebula and its exciting objects. In particular, ¹³CO J=1⟶0 line emission mapped by the Galactic Ring Survey (GRS) shows molecular gas associated with the infrared nebula. The ¹³CO radial velocity yields a far-kinematic distance of 11.1 kpc to the nebula, since there is no evidence for H I self-absorption. At 11.1 kpc, the far-infrared luminosity of the nebula is 4.8x10⁴ L_☉, and the mass of its molecular cloud is 1.1x10⁴ M_☉. The spectral energy distribution rises steeply from 2.2 to 100 µm with an absorption feature at 10 µm, exhibiting the shape of a late Class 0 young stellar object (YSO). The radio continuum flux observed toward the nebula is consistent with the free-free emission from one or more massive YSOs (MYSOs) with spectral types in the range O9 to B0. This analysis demonstrates one technique the GLIMPSE team will use for revealing thousands of Galactic star formation regions.