Mass ejection and time variability in protostellar outflows: Cep E. SOLIS XVI

Abstract

Protostellar jets are an important agent of star formation feedback, tightly connected with the mass-accretion process. The history of jet formation and mass-ejection provides constraints on the mass accretion history and the nature of the driving source. We want to characterize the time-variability of the mass-ejection phenomena at work in the Class 0 protostellar phase, in order to better understand the dynamics of the outflowing gas and bring more constraints on the origin of the jet chemical composition and the mass-accretion history. We have observed the emission of the CO 2-1 and SO N_J=5_4-4_3 rotational transitions with NOEMA, towards the intermediate-mass Class 0 protostellar system Cep E. The CO high-velocity jet emission reveals a central component associated with high-velocity molecular knots, also detected in SO, surrounded by a collimated layer of entrained gas. The gas layer appears to accelerate along the main axis over a length scale delta_0 ~700 au, while its diameter gradually increases up to several 1000au at 2000au from the protostar. The jet is fragmented into 18 knots of mass ~10^-3 Msun, unevenly distributed between the northern and southern lobes, with velocity variations up to 15 km/s close to the protostar, well below the jet terminal velocities. The knot interval distribution is approximately bimodal with a scale of ~50-80yr close to the protostar and ~150-200yr at larger distances >12". The mass-loss rates derived from knot masses are overall steady, with values of 2.7x10^-5 Msun/yr (8.9x10^-6 Msun/yr) in the northern (southern) lobe. The interaction of the ambient protostellar material with high-velocity knots drives the formation of a molecular layer around the jet, which accounts for the higher mass-loss rate in the north. The jet dynamics are well accounted for by a simple precession model with a period of 2000yr and a mass-ejection period of 55yr.

13 pages, 9 figures, 3 table. Accepted in A&A

References in corpus (11)

• Seeds Of Life In Space (SOLIS): The organic composition diversity at 300--1000 au scale in Solar-type star forming regions
• A highly-collimated SiO jet in the HH212 protostellar outflow
• The ALMA view of the protostellar system HH212 - The wind, the cavity, and the disk
• The CALYPSO IRAM-PdBI survey of jets from Class 0 protostars. Are jets ubiquitous in young stars ?
• First image of the L1157 molecular jet by the CALYPSO IRAM-PdBI survey
• Chemical and kinematic structure of extremely high-velocity molecular jets in the Serpens Main star-forming region
• CALYPSO view of SVS 13A with PdBI: Multiple jet sources
• Anatomy of HH 111 from CO observations : a bow shock driven molecular outflow
• An asymmetric jet launching model for the protoplanetary nebula CRL 618
• Molecules in the CepE-mm jet: evidence for shock-driven photochemistry?
• Proper Motions of Young Stellar Outflows in the Mid-Infrared with Spitzer. II. HH 377/Cep E

Cited by in corpus (5)

• JWST Peers into the Class I Protostar TMC1A: Atomic Jet and Spatially Resolved Dissociative Shock Region
• Modelling the early mass-ejection in jet driven protostellar outflows. Lessons from Cep E
• The SOFIA Massive (SOMA) Star Formation Q-band follow-up I. Carbon-chain chemistry of intermediate-mass protostars
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds
• Bowshocks driven by the pole-on molecular jet of outbursting protostar SVS 13