Visit ASIAA Homepage Registration Deadline: August 15, 2019 (Taiwan Time)
Science with the Submillimeter Array: Present and Future
November 4(Mon)-5(Tue), 2019
ASIAA, Taipei, Taiwan

Oral Presentation

Chemistry in the episodic accretion process

Author(s): Tien-Hao Hsieh (ASIAA) Nadia Murillo (Leiden) Naomi Hirano (ASIAA)

Presenter: Tien-Hao Hsieh (ASIAA)

Episodic accretion has been used to explain the wide range of protostellar luminosities, but its origin and influence on the star forming process are not yet fully understood. We present an ALMA survey of N2H+ (1 − 0) and HCO+ (3 − 2) toward 39 Class 0 and Class I sources in the Perseus molecular cloud. N2H+ and HCO+ are destroyed via gas-phase reactions with CO and H2O, respectively, thus tracing the CO and H2O snowline locations. A snowline location at a much larger radius than that expected from the current luminosity suggests that an accretion burst has occurred in the past which has shifted the snowline outward. We identified 18/18 Class 0 and 9/10 Class I post-burst sources from N2H+, and 7/17 Class 0 and 1/8 Class I post-burst sources from HCO+. This result can be interpreted as the evolution of burst frequency, suggesting that fagmentation is more likely to occur at the earlier stages where the young stellar object is more prone to instabilities. SMA observations in C18O emission had been used to probe the past burst. We will further discuss the feasibility of using DCO+/N2H+ observation from SMA to identify sources that do not undergoing or have not yet start episodic accretion. For a target with a similar depletion region in both DCO+ and N2H+, we speculate that its chemical property is similar to a starless core, which is likely a source not undergoing episodic accretion.

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