The ALMA-PILS survey: Gas dynamics in IRAS 16293$-$2422 and the connection between its two protostars

Abstract

[Abridged] The majority of stars form in binary or higher order systems. The Class 0 protostellar system IRAS16293-2422 contains two protostars, 'A' and 'B', separated by ~600 au and embedded in a single, 10^4 au scale envelope. Their relative evolutionary stages have been debated. We aim to study the relation and interplay between the two protostars A and B at spatial scales of 60 to ~1000 au. We selected molecular gas line transitions of CO, H2CO, HCN, CS, SiO, and CCH from the ALMA-PILS spectral imaging survey (329-363 GHz) and used them as tracers of kinematics, density, and temperature in the IRAS16293-2422 system. The angular resolution of the PILS data set allows us to study these quantities at a resolution of 0.5 arcsec (60 au [..]). Line-of-sight velocity maps of both optically thick and optically thin molecular lines reveal: (i) new manifestations of previously known outflows emanating from protostar A; (ii) a kinematically quiescent bridge of dust and gas spanning between the two protostars, with an inferred density between 4 10^4 and 3 10^7 cm^-3; and (iii) a separate, straight filament seemingly connected to protostar B seen only in CCH, with a flat kinematic signature. Signs of various outflows, all emanating from source A, are evidence of high-density and warmer gas; none of them coincide spatially and kinematically with the bridge. We hypothesize that the bridge arc is a remnant of filamentary substructure in the protostellar envelope material from which protostellar sources A and B have formed. One particular morphological structure appears to be due to outflowing gas impacting the quiescent bridge material. The continuing lack of clear outflow signatures unambiguously associated to protostar B and the vertically extended shape derived for its disk-like structure lead us to conclude that source B may be in an earlier evolutionary stage than source A.

Accepted for publication in A&A. 27 pages, 24 figures

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Cited by in corpus (8)

• Orbital and mass constraints of the young binary system IRAS 16293-2422 A
• FAUST II. Discovery of a Secondary Outflow in IRAS 15398-3359: Variability in Outflow Direction during the Earliest Stage of Star Formation?
• The young protostellar disk in IRAS16293-2422 B is hot and shows signatures of gravitational instability
• Successive deuteration in low-mass star-forming regions: the case of D${}_2$-methanol (CHD${}_2$OH) in IRAS 16293-2422
• Linear dust polarization during the embedded phase of protostar formation
• Discovery of an M-type Companion to the Herbig Ae Star V1787 Ori
• Singly- and doubly-deuterated formaldehyde in massive star-forming regions
• Rotating Motion of the Outflow of IRAS 16293-2422 A1 at its Origin Point near the Protostar