Naslov
Characterising the physical and chemical properties of a young Class 0 protostellar core embedded in the Orion B9 filament

Autori
Miettinen, O.

Izvornik
Astrophysics and space science (0004-640X) 361 (2016), 8; 248, 21

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
Astrochemistry ; Stars: formation ; Stars: protostars ; ISM: individual objects: Orion B9-SMM3

Sažetak
Deeply embedded low-mass protostars can be used as testbeds to study the early formation stages of solar-type stars, and the prevailing chemistry before the formation of a planetary system. The present study aims to characterise further the physical and chemical properties of the protostellar core Orion B9–SMM3. The Atacama Pathfinder EXperiment (APEX) telescope was used to perform a follow-up molecular line survey of SMM3. The observations were done using the single pointing (frequency range 218.2–222.2 GHz) and on-the-fly mapping methods (215.1–219.1 GHz). These new data were used in conjunction with our previous data taken by the APEX and Effelsberg 100 m telescopes. The following species were identified from the frequency range 218.2–222.2 GHz: 13CO, C18O, SO, para-H2CO, and E1-type CH3OH. The mapping observations revealed that SMM3 is associated with a dense gas core as traced by DCO+ and p-H2CO. Altogether three different p-H2CO transitions were detected with clearly broadened linewidths (v ∼ 8.2–11 km s−1 in FWHM). The derived p-H2CO rotational temperature, 64 ± 15 K, indicates the presence of warm gas. We also detected a narrow p-H2CO line (v = 0.42 km s−1) at the systemic velocity. The p-H2CO abundance for the broad component appears to be enhanced by two orders of magnitude with respect to the narrow line value (∼3 × 10−9 versus ∼2 × 10−11). The detected methanol line shows a linewidth similar to those of the broad p-H2CO lines, which indicates their coexistence. The CO isotopologue data suggest that the CO depletion factor decreases from ∼27 ± 2 towards the core centre to a value of ∼8 ± 1 towards the core edge. In the latter position, the N2D+/N2H+ ratio is revised down to 0.14±0.06. The origin of the subfragments inside the SMM3 core we found previously can be understood in terms of the Jeans instability if non-thermal motions are taken into account. The estimated fragmentation timescale, and the derived chemical abundances suggest that SMM3 is a few times 105 yr old, in good agreement with its Class 0 classification inferred from the spectral energy distribution analysis. The broad p-H2CO and CH3OH lines, and the associated warm gas provide the first clear evidence of a molecular outflow driven by SMM3.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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