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名稱Title
2020天文年會
中研院天文所 國際會議廳

論文摘要

ALMA Survey of Orion Planck Galactic Cold Clumps (ALMASOP): Evolution from the prestellar core to protostars

[ Oral ]

Somnath Dutta (ASIAA, Taiwan); Chin-Fei Lee (ASIAA, Taiwan); Tie Liu (SHAO, China); Naomi Hirano(ASIAA, Taiwan); Sheng-Yuan Liu( ASIAA, Taiwan); ALMASOP team

Planck Galactic Cold Clumps (PGCCs) are contemplated to be ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3mm (band 6) using three different configurations (resolutions ∼ 0.35, 1.0, and 7.0) to statistically investigate their evolutionary stages and sub-structures. We have obtained images of the 1.3 mm continuum and molecular line emission (e.g., 12CO, SiO) at an angular resolution of ~ 0.35 arcsec (140 au) with the combined arrays. We find 68 substructures within 48 detected dense cores where the dense substructures are clearly detected within the central 1000 au of four candidate prestellar cores. The envelope sizes and masses are found to be significantly reduced with protostellar evolution from Class 0 to Class I. Around 70% of the protostars exhibit bipolar CO outflows, whereas, more than 60% outflows are associated with high-velocity SiO jets. The outflow characteristics show an evolutionary change through the course of protostellar mass accretion. The CO velocity-dispersions (∆Vs) and the outflow cavity opening angle width at 400 au, [Θobs]400 (∼ 0. 6 to 3. 9 arcsec; corresponds to 33. 4 - 125.7 deg near the source) show an increasing correlation, suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostar envelope widens and the protostars generate more energetic outflows from a deeper gravitational potential well. Astrochemical diagnosis of the molecular species incorporates the chemical diversity from starless (abundant deuterated species like N2D+, DCO+) to the protostellar phases with a subset of line-reach "hot-corinos" (CH3OH, H2CO and their complex organic molecules).