The Spitzer c2d Survey of Large, Nearby, Interstellar Clouds. V. Chamaeleon II Observed with IRAC

Creators: Porras, Alicia; Jørgensen, Jes K.; Allen, Lori E.; Evans, Neal J., II; Bourke, Tyler L.; Alcalá, Juan M.; Dunham, Michael M.; Blake, Geoffrey A.; Chapman, Nicholas; Cieza, Lucas; Harvey, Paul M.; Huard, Tracy L.; Koerner, David W.; Mundy, Lee G.; Myers, Philip C.; Padgett, Deborah L.; Sargent, Anneila I.; Stapelfeldt, Karl R.; Teuben, Peter; van Dishoeck, Ewine F.; Wahhaj, Zahed; Young, Kaisa E.

Abstract

We present IRAC (3.6, 4.5, 5.8, and 8.0 μm) observations of the Chamaeleon II molecular cloud. The observed area covers about 1 deg^2 defined by A_V > 2. Analysis of the data in the 2005 c2d catalogs reveals a small number of sources (40) with properties similar to those of young stellar or substellar objects (YSOs). The surface density of these YSO candidates is low, and contamination by background galaxies appears to be substantial, especially for sources classified as Class I or flat spectral energy distribution (SED). We discuss this problem in some detail and conclude that very few of the candidate YSOs in early evolutionary stages are actually in the Cha II cloud. Using a refined set of criteria, we define a smaller, but more reliable, set of 24 YSO candidates.

Additional Information

© 2007 The American Astronomical Society. Received 2006 August 1; accepted 2006 October 25. We thank the referee for suggestions which led to a clearer presentation. We are grateful to the staff at the Lorentz Center at Leiden University for hospitality during a three week meeting in 2005 July where a large part of this work was pursued. Support for this work, part of the Spitzer Legacy Science Program, was also provided by NASA through contracts 1224608, 1230782, and 1230779 issued by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. The research of J. K. J. was supported by NASA Origins grant NAG5-13050. Astrochemistry in Leiden is supported by a NWO Spinoza grant and a NOVA grant. K. E. Y. was supported by NASA under grant NGT5-50401 issued through the Office of Space Science. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by NASA and NSF. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

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