演講資訊

摘要：

We present NOEMA and ALMA observations toward the Class 0/I protobinary system SVS13A as part of the PROtostars & DIsks: Global Evolution (PRODIGE) program. SVS13A is composed of two protostars VLA4A and VLA4B with a separation of ∼90 au, for which VLA4A is undergoing an accretion burst that enriches the chemistry of the surrounding gas. We study the kinematic structures of SVS13A via DCN (3–2) line, and the C18O (2–1) line at about hundred au scale. By combining our observations with previous ALMA high-angular-resolution observations, we find that the protobinary 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 with a rate of at least 1.4 × 10^−6 Msun/yr. We further analyzed line emission from six selected O-bearing Complex Organic Molecules (COMs): CH3OH, aGg’-(CH2OH)2, C2H5OH, CH2(OH)CHO, CH3CHO, and CH3OCHO. Interestingly, although the emission is not spatially resolved, the high-spectral-resolution data reveal complex line profiles with multiple peaks; the numbers of peaks (∼2−5), the velocities, and the linewidths of these six O-bearing COMs are different. The local thermodynamic equilibrium (LTE) fitting unveils decompose the line emission into up to six kinematic components with different excitation status. We further spatially resolve the system using ALMA observations targeting CH3CN and CH3-13-CN J=12-11 K-ladder line emission. We find the two-layer LTE radiative model including dust absorption is essential to interpret the CH3CN and CH3-13-CN line emission. We find a possible infalling signature toward the bursting secondary source VLA4A, which may be fed by an infalling streamer from the large-scale envelope. By accumulating mass from the streamer, the system might have experienced a gravitationally unstable phase before the accretion outburst. Finally, the CH3CN/CH3-13-CN ratio is lower than the canonical ratio in the local interstellar medium and is different between the binary components. We conclude that the large-scale infalling streamer is likely exist and contribute to the complexity of the COM emission. It can affect the accretion progress in the binary system, the chemistry and physical conditions during the formation of stellar binary system.