Chronology of Episodic Accretion in Protostars -- an ALMA survey of the CO and H$_2$O snowlines
Tien-Hao Hsieh, Nadia M. Murillo, Arnaud Belloche, Naomi Hirano,, Catherine Walsh, Ewine F. van Dishoeck, Jes K., J{\o}rgensen, Shih-Ping Lai

TL;DR
This study uses ALMA observations of N$_2$H$^+$ and HCO$^+$ to trace snowline shifts caused by episodic accretion bursts in protostars, revealing insights into burst history and star formation evolution.
Contribution
First survey to connect snowline locations with episodic accretion history in a large sample of protostars, providing new constraints on burst frequency and star formation processes.
Findings
Episodic accretion bursts cause snowline shifts outward.
Most Class 0 and I sources show evidence of past bursts.
Burst intervals increase from 2400 yr in Class 0 to 8000 yr in Class I.
Abstract
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 NH () and HCO () toward 39 Class 0 and Class I sources in the Perseus molecular cloud. NH and HCO are destroyed via gas-phase reactions with CO and HO, respectively, thus tracing the CO and HO 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 NH, and 7/17 Class 0 and 1/8 Class I post-burst sources from HCO.The accretion luminosities during the past bursts are found to be . This result can…
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