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Abstract:
Context. In the past few years, there has been a rise in the detection of streamers, asymmetric flows of material directed toward the protostellar disk with material from outside a star’s natal core. It is unclear how they affect the process of mass accretion, in particular beyond the Class 0 phase.<br>Aims. We investigate the gas kinematics around Per-emb-50, a Class I source in the crowded star-forming region NGC 1333. Our goal is to study how the mass infall proceeds from envelope to disk scales in this source.<br>Methods. We use new NOEMA 1.3 mm observations, including C<SUP>18</SUP>O, H<SUB>2</SUB>CO, and SO, in the context of the PRODIGE MPG – IRAM program, to probe the core and envelope structures toward Per-emb-50.<br>Results. We discover a streamer delivering material toward Per-emb-50 in H<SUB>2</SUB>CO and C<SUP>18</SUP>O emission. The streamer’s emission can be well described by the analytic solutions for an infalling parcel of gas along a streamline with conserved angular momentum, both in the image plane and along the line-of-sight velocities. The streamer has a mean infall rate of 1.3 × 10ysup>−6</sup> M<sub>⊙</sub> yr<sup>−1</sup>, five to ten times higher than the current accretion rate of the protostar. SO and SO<SUB>2</SUB> emission reveal asymmetric infall motions in the inner envelope, additional to the streamer around Per-emb-50. Furthermore, the presence of SO<SUB>2</SUB> could mark the impact zone of the infalling material.<br>Conclusions. The streamer delivers sufficient mass to sustain the protostellar accretion rate and might produce an accretion burst, which would explain the protostar’s high luminosity with respect to other Class I sources. Our results highlight the importance of late infall for protostellar evolution: streamers might provide a significant amount of mass for stellar accretion after the Class 0 phase.
