PRODIGE -- Envelope to disk with NOEMA I. A 3000 au streamer feeding a Class I protostar

TL;DR

This study observes a streamer feeding a Class I protostar, Per-emb-50, demonstrating how late-stage infall from envelope to disk can significantly influence protostellar growth and potentially trigger accretion bursts.

Contribution

It provides the first detailed analysis of a streamer feeding a Class I protostar, quantifying the infall rate and its impact on protostellar evolution beyond the Class 0 phase.

Findings

Streamer delivers material at a rate 5-10 times higher than current accretion.

Infall motions are asymmetric and may cause accretion bursts.

Streamer can sustain the protostar's high luminosity.

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 the star's natal core. It is unclear how they affect the process of mass accretion, in particular beyond the Class 0 phase. 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. Results. We discover a streamer delivering material toward Per-emb-50 in H$_2$CO and C$^{18}$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 $1.3 \times 10^{ -6}$ M$_{ \odot}$ yr$^{ -1}$, $5 -10$ times higher than the current accretion rate of the protostar. SO and SO$_2$ emission reveal asymmetric infall motions in the inner envelope, additional to the streamer around Per-emb-50. Furthermore, the presence of SO$_2$ could mark the impact zone of the infalling material. 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.