Caramazza, M. and Micela, G. and Prisinzano, L. and Rebull, L. and Sciortino, S. and Stauffer, J. R. (2008) Circumstellar disks in the outer galaxy : the star-forming region NGC 1893. Astronomy and astrophysics, 488 (1). pp. 211-218. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:20090414-110928763
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Context. It is still debated whether star formation process depends on environment. In particular it is yet unclear whether star formation in the outer Galaxy, where the environmental conditions are, theoretically, less conducive, occurs in the same way as in the inner Galaxy. Aims. We investigate the population of NGC 1893 , a young cluster (~3-4 Myr) in the outer part of the Galaxy (RG ≥ 11 kpc), to explore the effects of environmental conditions on star forming regions. Methods. We present infrared observations acquired using the IRAC camera onboard the Spitzer Space Telescope and analyze the color-color diagrams to establish the membership of stars with excesses. We also merge this information with that obtained from Chandra ACIS-I observations, to identify the Class III population. Results. We find that the cluster is very rich, with 242 PMS Classical T Tauri stars and 7 Class 0/I stars. We identify 110 Class III candidate cluster members in the ACIS-I field of view. We estimate a disk fraction for NGC 1893 of about 67% , similar to fractions calculated for nearby star forming regions of the same age. Conclusions. Although environmental conditions are unfavorable, star formation can clearly be very successful in the outer Galaxy, allowing creation of a very rich cluster like NGC 1893 .
|Additional Information:||© ESO 2008.Received 5 May 2008 / Accepted 30 May 2008. We acknowledge financial contribution from contract ASIINAF I/023/05/0 and from European Commission (contract N. MRTN-CT-2006- 035890). This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech.|
|Subject Keywords:||stars : pre-main sequence; stars : circumstellar matter; Galaxy : open cluster and association : individual : NGC 1893; stars : formation|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||25 Jun 2009 17:18|
|Last Modified:||26 Dec 2012 10:57|
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