The Mass Distribution And Lifetime Of Prestellar Cores In Perseus, Serpens, And Ophiuchus
Abstract
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 rho alpha 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 alpha = -2.3 +/- 0.4 for M > 0.8 M-circle dot. 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.
Department
Subject
infrared : ism
ism : clouds
ism : individual (ophiuchus, perseus,
serpens)
stars : formation
submillimeter
spitzer c2d survey
dust continuum emission
turbulent molecular clouds
pre-protostellar cores
young stellar objects
star-formation
interstellar clouds
legacy clouds
dense cores
infrared observations
astronomy & astrophysics
ism : clouds
ism : individual (ophiuchus, perseus,
serpens)
stars : formation
submillimeter
spitzer c2d survey
dust continuum emission
turbulent molecular clouds
pre-protostellar cores
young stellar objects
star-formation
interstellar clouds
legacy clouds
dense cores
infrared observations
astronomy & astrophysics