2025A&A...699A.382M

Context. During the early stages of star formation, accretion processes such as infall from the envelope and molecular streamers and ejection of matter through winds and jets take place simultaneously and distribute the angular momentum of the parent molecular cloud. The Class 0/I binary [BHB2007] 11 shows evidence for accretion and ejection at the scales of the circumbinary disk and the inner close binary. Recent observations of H₂CO, however, have shown two elongated structures with indications of outflowing motion almost perpendicular to the main CO outflow, which is launched from the circumbinary disk.
Aims. We study the kinematics of the molecular gas at intermediate scales of ∼50-3000 au around [BHB2007] 11 to verify the nature of these elongated structures.
Methods. We analyzed the line emission of H¹³CO⁺, CCH, c-C₃H₂, and SiO observed with the Atacama Large Millimeter/submillimeter Array (ALMA) within the large program called Fifty AU STudy of the chemistry in the disc/envelope system of Solar-like protostars (FAUST). These molecules trace the material that moves at velocities close to that of the ambient cloud, which could not be probed in previous observations of the self-absorbed emission of CO.
Results. The images of H¹³CO⁺, CCH, and c-C₃H₂ show clear elongated structures similar to those previously detected in H₂CO, whose gas kinematics are consistent with outflowing motions and with rotation in the opposite sense to the main CO outflow. The derived mass-loss rate from these large-scale structures is (1.7 ± 0.5) × 10^–6M_⊙ yr^–1, which agrees with the rates measured in outflows driven by Class 0/I protostars. The SiO image reveals compact emission close to the binary system, with a slight elongation that is aligned with the larger-scale structures. This suggests that SiO is released from the sputtering of dust grains in the shocked material at the base of the potential new outflow, with a relative abundance of ≥(0.11-2.0) × 10^–9. However, higher angular and spectral resolution observations are needed to accurately estimate the outflow-launching radius and its powering source. Based on the location and the abundance of the SiO emission, we propose that the second outflow may be launched from inside the circumbinary disk, likely by the less massive companion that actively accretes material from its surroundings.