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Published July 10, 2006 | Published
Journal Article Open

The Spitzer c2d survey of large, nearby, interstellar clouds. III. Perseus observed with IRAC


We present observations of 3.86 deg to the 2nd of the Perseus molecular cloud complex with the Spitzer Space Telescope Infrared Array Camera (IRAC). The maps show strong extended emission arising from shocked H2 in outflows and from polycyclic aromatic hydrocarbon features. More than 120,000 sources are extracted toward the cloud. Based on their IRAC colors and comparison to off-cloud and extragalactic fields, we identify 400 candidate young stellar objects. About two-thirds of these are associated with the young clusters IC 348 and NGC 1333, while the last third is distributed over the remaining cloud. The young stellar objects are classified according to the slope of their spectral energy distributions. Significant differences are found between the numbers of embedded Class I objects and more evolved Class II objects in IC 348, NGC 1333 and the remaining cloud, with the embedded Class I and "flat-spectrum" YSOs constituting 14%, 36% and 47% of the total number of YSOs identified in each of these regions. The high number of Class I objects in the extended cloud (61% of the Class I objects in the entire cloud) suggests that a significant fraction of the current star formation occurs outside the two main clusters. Finally, we discuss a number of outflows and identify their driving sources, including the deeply embedded Class 0 sources outside the two main clusters. The Class 0 objects are detected by Spitzer and have very red [3.6] - [4.5] colors, but they do not show similarly red [5.8] - [8.0] colors. The Class 0 objects are easily identifiable in color-color diagrams but are problematic to extract automatically due to the extended emission from shocked gas or scattered light in cavities related to the associated outflows.

Additional Information

© 2006 The American Astronomical Society. Received 2006 January 27; accepted 2006 March 17. 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. We thank Mike Dunham for supplying the SHARC II image of the L1455 region. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. The research of J.K.J. was supported by NASA Origins Grant NAG5-13050. Support for this work, part of the Spitzer Legacy Science Program, was also provided by NASA through contract 1224608, 1230782, and 1230779 issued by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. 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 ussed through the Office of Space Science. The SHARC II data were obtained with support from NASA Origins grant NNG04GG24G to N.J.E.

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