Identifying the Low-Luminosity Population of Embedded Protostars in the c2d Observations of Clouds and Cores

摘要: We present the results of a search for all embedded protostars with internal luminosities ≤1.0 L☉ in full sample nearby, low-mass star-forming regions surveyed by Spitzer Space Telescope Legacy Project From Molecular Cores to Planet Forming Disks (c2d). The luminosity source, Lint, is central source and excludes arising from external heating. On average, c2d data are sensitive -->Lint ≥ 4 × 10−3(d/140 pc)2 L☉, factor 25 better than sensitivity Infrared Astronomical Satellite (IRAS) such objects. set selection criteria used identify candidates examine complementary decide whether each candidate truly an protostar. find tight correlation between 70 μm flux protostar, empirical result based on both observations detailed two-dimensional radiative transfer models protostars. 50 ≤ 1.0 L☉; 15 have 0.1 L☉. intrinsic distribution increases lower luminosities. While we sources down above limit, indicating that may extend probed these observations, able rule out continued rise below = Between 75% 85% cores classified as starless prior being observed remain our sensitivity; remaining 15%-25% harbor low-luminosity, compile complete spectral energy distributions objects calculate standard evolutionary signatures (Lbol, Tbol, Lbol/Lsmm) argue inconsistent simplest picture star formation, wherein mass accretes core onto protostar at constant rate.