Frieswijk, W. F. and Spaans, M. and Shipman, R. F. and Teyssier, D. and Carey, S. J. and Tielens, A. G. G. M. (2008) Spitzer's Mid-Infrared View on an Outer-Galaxy Infrared Dark Cloud Candidate toward NGC 7538. Astrophysical Journal Letters, 685 (1). L51-L54. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:FRIapjl08
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Infrared dark clouds (IRDCs) represent the earliest observed stages of clustered star formation, characterized by large column densities of cold and dense molecular material observed in silhouette against a bright background of mid-IR emission. Up to now, IRDCs were predominantly known toward the inner Galaxy where background infrared emission levels are high. We present Spitzer observations with the Infrared Array Camera toward object G111.80+0.58 (G111) in the outer Galactic plane, located at a distance of ~3 kpc from us and ~10 kpc from the Galactic center. Earlier results show that G111 is a massive, cold molecular clump very similar to IRDCs. The mid-IR Spitzer observations unambiguously detect object G111 in absorption. We have identified for the first time an IRDC in the outer Galaxy, which confirms the suggestion that cluster-forming clumps are present throughout the Galactic plane. However, against a low mid-IR background such as the outer Galaxy it takes some effort to find them.
|Additional Information:||© 2008. The American Astronomical Society. Received 2008 February 7; accepted 2008 August 11; published 2008 September 20. Print publication: Issue 1 (2008 September 20). We thank the anonymous referee for his/her careful reading of the manuscript and his/her constructive remarks. Facilities: Spitzer (IRAC)|
|Subject Keywords:||dust, extinction; infrared: ISM; ISM: clouds; stars: formation|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Archive Administrator|
|Deposited On:||15 Jan 2009 07:59|
|Last Modified:||26 Dec 2012 10:43|
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