High-Mass Starless Cores

We report the identification of a sample of potential high-mass starless cores (HMSCs). The cores were discovered by comparing images of fields containing candidate high-mass protostellar objects (HMPOs) at 1.2 mm and mid-infrared (MIR; 8.3 (mu)m) wavelengths. While the HMPOs are detected at both wavelengths, several cores emitting at 1.2 mm in the same fields show absorption or no emission at the MIR wavelength. We argue that the absorption is caused by cold dust. The estimated masses of a few times 102-103 M(circled dot operator) and the lack of IR emission suggest that they may be massive cold cores in a prestellar phase, which could form massive stars. Ammonia observations indicate smaller velocity dispersions and lower rotation temperatures compared with HMPOs and ultracompact H II regions, suggesting a quiescent prestellar stage. We propose that these newly discovered cores are good candidates for the HMSC stage in highmass star formation. This sample of cores will allow us to study the high-mass star and cluster formation processes at the earliest evolutionary stages.