The CALYPSO IRAM-PdBI survey of jets from Class 0 protostars. Exploring whether jets are ubiquitous in young stars

Aims: As a part of the CALYPSO Large Program, we aim to constrain the properties of protostellar jets and outflows by searching for corresponding emission in a sample of 21 Class 0 protostars covering a broad range of internal luminosities (L_int from 0.035 L_⊙ to 47 L_⊙).
Methods: We analyzed high angular (~0."5-1."0) resolution IRAM Plateau de Bure Interferometer (PdBI) observations in three typical outflow and jet tracers, namely: CO (2−1), SO (5₆−4₅), and SiO (5−4). We obtained the detection rate, spatial distribution, kinematics, and collimation of the outflow and jet emission in the three lines. Molecular column densities and abundances, the jet mass-loss and momentum rates, and mechanical luminosity are estimated from the integrated line intensities.
Results: Blue- and red-shifted emission in CO (2−1), which probes outflowing gas, was detected in all the sources in the sample and detected for the first time in the cases of SerpS-MM22 and SerpS-MM18b. Collimated high-velocity jets in SiO (5−4) were detected in 67% of the sources (for the first time in IRAS4B2, IRAS4B1, L1448-NB, SerpS-MM18a) and 77% of these also showed jet or outflow emission in SO (5₆−4₅). The detection rate of jets in SiO and SO increases with internal luminosity. In five sources (that is, 24% of the sample) SO (5₆−4₅) is elongated and reveals a velocity gradient perpendicular to the jet direction, hence, it probes the inner envelope or the disk, or both. The detected SiO jets are collimated (typical opening angle, α ~ 10°) and surrounded by wider angle SO (α ~ 15°) and CO (α ~ 25°) emission. The abundance of SO relative to H₂ ranges from <10⁻⁷ up to 10⁻⁶; whereas for SiO, the lower limits were found to range from >2.4 × 10⁻⁷ to >5 × 10⁻⁶, with the exception of the jets from IRAS4A1 and IRAS4A2, which show low SiO abundance (≤2−6 × 10⁻⁸). The mass-loss rates range from ~7 × 10⁻⁸ M_⊙ yr⁻¹ up to ~3 × 10⁻⁶ M_⊙ yr⁻¹ for L_int ~ 1−50 L_⊙.
Conclusions: The CALYPSO IRAM-PdBI survey shows that the outflow phenomenon is ubiquitous in our sample of protostars and that the detection rate of high-velocity collimated jets increases for increasing protostellar accretion, with at least 80% of the sources with L_int > 1 L_⊙ driving a jet. The detected protostellar flows exhibit an onion-like structure, where the SiO jet is nested into a wider angle SO and CO outflow. On scales > 300 au the SiO jets are less collimated (4°−12°) than atomic jets from Class II sources (~3°), possibly dueto projection effects and contamination by SiO emission from the bow-shocks. On the other hand, velocity asymmetry between the two jet lobes are detected in one third of the sources, similarly to Class II atomic jets, suggesting that the same launching mechanism is at work. Most of the jets are SiO rich, which indicates very efficient release of > 1− 10% of elemental silicon in gas phase likely in dust-free winds, launched from inside the dust sublimation radius. The estimated mass-loss rates are larger by up to five orders of magnitude than what was measured for Class II jets, indicating that the ejection decreases as the source evolves and accretion fades. Similarly to Class II sources, the mass-loss rates are ~ 1− 50% of the mass accretion rate, Ṁ_acc, suggesting that the correlation between mass ejection and mass accretion holds along the star-formation process from 10⁴ yr up to a few Myr.

The calibrated data and continuum and line maps analysed in the paper are part of the IRAM PdBI Large Program CALYPSO and are available on the IRAM webpage at the following link: https://www.iram.fr/ILPA/LP010/