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  1. Abstract Jets can facilitate the mass accretion onto the protostars in star formation. They are believed to be launched from accretion disks around the protostars by magnetocentrifugal force, as supported by the detections of rotation and magnetic fields in some of them. Here we report a radial flow of the textbook-case protostellar jet HH 212 at the base to further support this jet-launching scenario. This radial flow validates a central prediction of the magnetocentrifugal theory of jet formation and collimation, namely, the jet is the densest part of a wide-angle wind that flows radially outward at distances far from themore »(small, sub-au) launching region. Additional evidence for the radially flowing wide-angle component comes from its ability to reproduce the structure and kinematics of the shells detected around the HH 212 jet. This component, which can transport material from the inner to outer disk, could account for the chondrules and Ca–Al-rich inclusions detected in the solar system at large distances.« less
    Free, publicly-accessible full text available March 1, 2023
  2. Free, publicly-accessible full text available October 1, 2022
  3. Abstract The water snowline location in protostellar envelopes provides crucial information about the thermal structure and the mass accretion process as it can inform about the occurrence of recent (≲1000 yr) accretion bursts. In addition, the ability to image water emission makes these sources excellent laboratories to test indirect snowline tracers such as H 13 CO + . We study the water snowline in five protostellar envelopes in Perseus using a suite of molecular-line observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at ∼0.″2−0.″7 (60–210 au) resolution. B1-c provides a textbook example of compact H 2 18 O (3more »1,3 −2 2,0 ) and HDO (3 1,2 −2 2,1 ) emission surrounded by a ring of H 13 CO + ( J = 2−1) and HC 18 O + ( J = 3−2). Compact HDO surrounded by H 13 CO + is also detected toward B1-bS. The optically thick main isotopologue HCO + is not suited to trace the snowline, and HC 18 O + is a better tracer than H 13 CO + due to a lower contribution from the outer envelope. However, because a detailed analysis is needed to derive a snowline location from H 13 CO + or HC 18 O + emission, their true value as a snowline tracer will lie in the application in sources where water cannot be readily detected. For protostellar envelopes, the most straightforward way to locate the water snowline is through observations of H 2 18 O or HDO. Including all subarcsecond-resolution water observations from the literature, we derive an average burst interval of ∼10,000 yr, but high-resolution water observations of a larger number of protostars are required to better constrain the burst frequency.« less
    Free, publicly-accessible full text available January 1, 2023