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Published September 10, 2008 | Published
Journal Article Open

The mass distribution and lifetime of prestellar cores in Perseus, Serpens, and Ophiuchus


We present an unbiased census of starless cores in Perseus, Serpens, and Ophiuchus, assembled by comparing large-scale Bolocam 1.1 mm continuum emission maps with Spitzer c2d surveys. We use the c2d catalogs to separate 108 starless from 92 protostellar cores in the 1.1 mm core samples from Enoch and Young and their coworkers. A comparison of these populations reveals the initial conditions of the starless cores. Starless cores in Perseus have similar masses but larger sizes and lower densities on average than protostellar cores, with sizes that suggest density profiles substantially flatter than ρ∝r^-2. By contrast, starless cores in Serpens are compact and have lower masses than protostellar cores; future star formation will likely result in lower mass objects than the currently forming protostars. Comparison to dynamical masses estimated from the NH3 survey of Perseus cores by Rosolowsky and coworkers suggests that most of the starless cores are likely to be gravitationally bound, and thus prestellar. The combined prestellar core mass distribution includes 108 cores and has a slope of α = -2.3 ± 0.4 for M > 0.8 M☉. This slope is consistent with recent measurements of the stellar initial mass function, providing further evidence that stellar masses are directly linked to the core formation process. We place a lower limit on the core-to-star efficiency of 25%. There are approximately equal numbers of prestellar and protostellar cores in each cloud; thus the dense prestellar core lifetime must be similar to the lifetime of embedded protostars, or 4.5 x 10^5 yr, with a total uncertainty of a factor of 2. Such a short lifetime suggests a dynamic, rather than quasi-static, core evolution scenario, at least at the relatively high mean densities (n > 2 x 10^4 cm^-3) to which we are sensitive.

Additional Information

© 2008. The American Astronomical Society. Received 2008 February 1; accepted 2008 May 7; published 2008 September 10. The authors are grateful to Jens Kauffman and Jason Kirk for their insightful comments and suggestions, and to the anonymous referee for raising questions and issues that helped to improve this work. Support for this work, part of the Spitzer Legacy Science Program, was provided by NASA through contracts 1224608 and 1230782 issued by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407. Additional support was provided by NASA through the Spitzer Space Telescope Fellowship Programand obtained from NASA Origins grant NNG04GG24G to the University of Texas at Austin. Support for the development of Bolocam was provided by NSF grants AST 99-80846 and AST 02-06158. M. L. E. acknowledges support of a Caltech Moore Fellowship and a Spitzer Space Telescope Postdoctoral Fellowship.

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