부산대학교 도서관

Spitzer Space Telescope observations of a point-like source, L1014-IRS, close to the dust peak of the low-mass dense core L1014 have questioned its starless nature. The presence of an object with colors expected for an embedded protostar makes L1014-IRS the lowest luminosity isolated protostar known, and an ideal target with which to test star formation theories at the low mass end. In order to study its molecular content and to search for the presence of a molecular outflow, we mapped L1014 in at least one transition of 12CO, N2H+, HCO+, CS and of their isotopologues 13CO, C18O, C17O, N2D+ and H13CO+, using the FCRAO, the IRAM 30 meter and the CSO. The data show physical and chemical properties in L1014 typical of the less evolved starless cores: i.e. H2 central density of a few 10^5 molecules cm^-3, estimated mass of ~2M_sun, CO integrated depletion factor less than 10, N(N2H+)~6*10^12 cm^-2, N(N2D+)/N(N2H+) equal to 10% and relatively broad N2H+(1--0) lines (0.35 km/s). Infall signatures and significant velocity shifts between optically thick and optically thin tracers are not observed in the line profiles. No classical signatures of molecular outflow are found in the 12CO and 13CO observations. In particular, no high velocity wings are found, and no well-defined blue-red lobes of 12CO emission are seen in the channel maps. If sensitive, higher resolution observations confirm the absence of an outflow on a smaller scale than probed by our observations, L1014-IRS would be the only protostellar object known to be formed without driving an outflow.
Comment: 17 pages, 8 figures, 3 tables, Accepted for publication in Astronomy and Astrophysics