Solis

Abstract

Context. 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 on the nature of the driving source. Aims. We 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. Methods. Using the NOrthern Extended Millimeter Array (NOEMA) interferometer, we have observed the emission of the CO 2–1 and SO NJ = 54–43 rotational transitions at an angular resolution of 1.0″ (820 au) and 0.4″ (330 au), respectively, toward the intermediate-mass class 0 protostellar system Cep E. Results. The CO high-velocity jet emission reveals a central component of ≤400 au diameter associated with high-velocity molecular knots that is also detected in SO, surrounded by a collimated layer of entrained gas. The gas layer appears to be accelerated along the main axis over a length scale δ0 ~ 700 au, while its diameter gradually increases up to several 1000 au at 2000 au from the protostar. The jet is fragmented into 18 knots of mass ~10−3 M⊙, unevenly distributed between the northern and southern lobes, with velocity variations up to 15 km s−1 close to the protostar. This is well below the jet terminal velocities in the northern (+ 65 km s−1) and southern (−125 km s−1) lobes. The knot interval distribution is approximately bimodal on a timescale of ~50–80 yr, which is close to the jet-driving protostar Cep E-A and ~150–20 yr at larger distances >12″. The mass-loss rates derived from knot masses are steady overall, with values of 2.7 × 10−5 M⊙ yr−1 and 8.9 × 10−6 M⊙ yr−1 in the northern and southern lobe, respectively. Conclusions. The interaction of the ambient protostellar material with high-velocity knots drives the formation of a molecular layer around the jet. This accounts for the higher mass-loss rate in the northern lobe. The jet dynamics are well accounted for by a simple precession model with a period of 2000 yr and a mass-ejection period of 55 yr.

An Extremely Young Protostellar Core, MMS 1/OMC-3: Episodic Mass Ejection History Traced by the Micro SiO Jet

“…Both models produce a garden-hose effect, resulting in jet wiggling (Raga et al 1993). The observed MMS 1 jet morphology allows us to distinguish the origin of the jet wiggling (Frank et al 2014;Schutzer et al 2022, and references therein). In the case of jet wiggling due to binary orbital motion, the jet is expected to bend in the direction opposite to the location of the secondary (binary) component.…”

Shedding Light on the Ejection History of Molecular Outflows: Multiple Velocity Modes and Precession

“…The physical processes in the molecular outflow of core MM1#8 could be different from those of the intermediatemass Cepheus E core, which was recently studied with CO observations and numerical simulations (de Schutzer et al 2022;Rivera-Ortiz et al 2023). Rivera-Ortiz et al (2023) showed that one-velocity ejection variations successfully reproduce the observed features, especially the bimodal distribution of the dynamical timescales of the knots.…”

“…A series of these velocity spurs composes a jagged PV profile sometimes called the "Hubble wedge" (Arce & Goodman 2001). These complex PV diagrams have been investigated in about a dozen low-mass Class 0 protostars so far, including HH111 (Cernicharo & Reipurth 1996), L1551 (Bachiller et al 1994), L1157 (Gueth et al 1998), HH212 (Lee et al 2006), HH46-47 (Arce et al 2013), and more recently Cepheus E (de Schutzer et al 2022).…”

“…Rabenanahary et al (2022) compared simulations of an outflow driven by a pulsed jet and observations in CARMA-7 by Plunkett et al (2015). Rivera-Ortiz et al (2023) carried out simulations of a jet aimed at reproducing the Cepheus E outflow observed by de Schutzer et al (2022).…”