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Context.Molecular outflows are believed to be a key ingredient in the process of star formation. The molecular outflow associated with DR21 Main in Cygnus-X is one of the most extreme molecular outflows in the Milky Way in terms of mass and size. The outflow is suggested to belong to a rare class of explosive outflows formed by the disintegration of protostellar systems. Aims.We aim to explore the morphology, kinematics, and energetics of the DR21 Main outflow, and to compare those properties to confirmed explosive outflows in order to unravel the underlying driving mechanism behind DR21. Methods.We studied line and continuum emission at a wavelength of 3.6 mm with IRAM 30 m and NOEMA telescopes as part of the Cygnus Allscale Survey of Chemistry and Dynamical Environments (CASCADE) program. The spectra include (J= 1−0) transitions of HCO⁺, HCN, HNC, N₂H⁺, H₂CO, and CCH, which trace different temperature and density regimes of the outflowing gas at high velocity resolution (~0.8 km s⁻¹). The map encompasses the entire DR21 Main outflow and covers all spatial scales down to a resolution of 3″ (~0.02 pc). Results.Integrated intensity maps of the HCO⁺emission reveal a strongly collimated bipolar outflow with significant overlap of the blueshifted and redshifted emission. The opening angles of both outflow lobes decrease with velocity, from ~80 to 20° for the velocity range from 5 to 45 km s⁻¹relative to the source velocity. No evidence is found for the presence of elongated, “filament-like” structures expected in explosive outflows. N₂H⁺emission near the western outflow lobe reveals the presence of a dense molecular structure, which appears to be interacting with the DR21 Main outflow. Conclusions.The overall morphology as well as the detailed kinematics of the DR21 Main outflow are more consistent with a typical bipolar outflow than with an explosive counterpart. 

Aims. We present high-sensitivity and high spectral-resolution NOEMA observations of the Class 0/I binary system SVS13A, composed of the low-mass protostars VLA4A and VLA4B, with a separation of ~90 au. VLA4A is undergoing an accretion burst that is enriching the chemistry of the surrounding gas, which provides an excellent opportunity to probe the chemical and physical conditions as well as the accretion process. Methods. We observe the (12 K –11 K ) lines of CH 3 CN and CH 3 13 CN, the DCN (3–2) line, and the C 18 O (2–1) line toward SVS13A using NOEMA. Results. We find complex line profiles at disk scales that cannot be explained by a single component or pure Keplerian motion. By adopting two velocity components to model the complex line profiles, we find that the temperatures and densities are significantly different among these two components. This suggests that the physical conditions of the emitting gas traced via CH 3 CN can change dramatically within the circumbinary disk. In addition, combining our observations of DCN (3–2) with previous ALMA observations at high angular resolution, we find that the binary system (or VLA4A) might be fed by an infalling streamer from envelope scales (~700 au). If this is the case, this streamer contributes to the accretion of material onto the system at a rate of at least 1.4 × 10 −6 M ⊙ yr −1 . Conclusions. We conclude that the CH 3 CN emission in SVS13A traces hot gas from a complex structure. This complexity might be affected by a streamer that is possibly infalling and funneling material into the central region. 

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. 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. Methods. We use new NOEMA 1.3 mm observations, including C 18 O, H 2 CO, and SO, in the context of the PRODIGE MPG – IRAM program, to probe the core and envelope structures toward Per-emb-50. 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 × 10 −6 M ⊙ yr− 1 , five to ten 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.