[Paper Review] The CALYPSO IRAM-PdBI survey of jets from Class 0 protostars. Are jets ubiquitous in young stars ?

L. Podio, Benoît Tabone+11 more|arXiv (Cornell University)|Dec 31, 2020

Astrophysics and Star Formation Studies158 references4 citations

TL;DR

This CALYPSO IRAM-PdBI survey of 21 Class 0 protostars reveals that protostellar jets are ubiquitous, with 67% showing collimated SiO (5–4) jets and 77% also exhibiting SO (5₆–4₅) emission. The study finds that jet detection rates increase with internal luminosity, and that jets exhibit an onion-like structure with SiO most collimated (α ≈ 10°), followed by SO (α ≈ 15°) and CO (α ≈ 25°), indicating efficient SiO production in dust-free winds near the sublimation radius.

ABSTRACT

As a part of the CALYPSO large programme, we constrain the properties of protostellar jets and outflows in a sample of 21 Class 0 protostars with internal luminosities, Lint, from 0.035 to 47 Lsun. We analyse high angular resolution (~0.5"-1") IRAM PdBI observations in CO (2-1), SO ($5_6-4_5$), and SiO (5-4). CO (2-1), which probes outflowing gas, is detected in all the sources (for the first time in SerpS-MM22 and SerpS-MM18b). Collimated high-velocity jets in SiO (5-4) are detected in 67% of the sources (for the first time in IRAS4B2, IRAS4B1, L1448-NB, SerpS-MM18a), and 77% of these also show jet/outflow emission in SO ($5_6-4_5$). In 5 sources (24% of the sample) SO ($5_6-4_5$) probes the inner envelope and/or the disk. The CALYPSO survey shows that the outflow phenomenon is ubiquitous and that the detection rate of high-velocity jets increases with protostellar accretion, with at least 80% of the sources with Lint>1 Lsun driving a jet. The protostellar flows exhibit an onion-like structure, where the SiO jet (opening angle ~10$^o$) is nested into a wider angle SO (~15$^o$) and CO (~25$^o$) outflow. On scales >300 au the SiO jets are less collimated than atomic jets from Class II sources (~3$^o$). 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 (SiO/H2 from >2.4e-7 to >5e-6), which indicates efficient release of >1%-10% of silicon in gas phase likely in dust-free winds, launched from inside the dust sublimation radius. The mass-loss rates (from ~7e-8 to ~3e-6 Msun/yr) are larger than what was measured for Class II jets. Similarly to Class II sources, the mass-loss rates are ~1%-50% of the mass accretion rates suggesting that the correlation between ejection and accretion in young stars holds from 1e4 yr up to a few Myr.

Motivation & Objective

• To determine the ubiquity of protostellar jets in Class 0 protostars by analyzing high-resolution millimeter-wave observations.
• To investigate the kinematics, collimation, and spatial structure of molecular outflows and jets using CO (2–1), SO (5₆–4₅), and SiO (5–4) emission lines.
• To estimate jet mass-loss rates, momentum fluxes, and mechanical luminosities, and compare them with accretion rates to test the jet-accretion correlation.
• To assess the chemical abundance of SiO and SO in jets and infer the physical conditions and launching mechanisms near the protostar.
• To evaluate whether the jet properties observed in Class 0 protostars are consistent with those in Class II T Tauri stars, particularly in terms of collimation, asymmetry, and ejection efficiency.

Proposed method

• Conducted high-angular-resolution (0.′′5–1.′′0) interferometric observations using the IRAM Plateau de Bure Interferometer (PdBI) at millimeter wavelengths.
• Targeted three key molecular tracers: CO (2–1) for outflowing gas, SO (5₆–4₅) for intermediate-velocity shocks, and SiO (5–4) for high-velocity jets.
• Measured integrated line intensities to derive molecular column densities, abundances, and mass-loss rates using radiative transfer and excitation models.
• Estimated jet mechanical luminosity as $ L_{\text{jet}} = \frac{1}{2} \dot{M}_{\text{jet}} V_{\text{jet}}^2 $, comparing it to internal luminosity $ L_{\text{int}} $ to assess energy budget.
• Analyzed velocity gradients and spatial morphology to identify precession, wiggling, and asymmetric ejection in jet lobes.
• Assessed optical depth of SiO (5–4) emission to determine whether SiO is optically thick in jet knots, informing shock and chemistry models.

Experimental results

Research questions

• RQ1 Are protostellar jets ubiquitous in Class 0 protostars, and how does their detection rate correlate with internal luminosity?
• RQ2 What is the spatial and kinematic structure of jets and outflows, and do they exhibit an onion-like stratification with increasing collimation from CO to SiO?
• RQ3 What are the mass-loss rates and mechanical luminosities of Class 0 jets, and how do they compare to accretion rates and internal luminosities?
• RQ4 Why are SiO abundances in jets so high (up to $ >5 \times 10^{-6} $ relative to H₂), and what does this imply about the jet launching mechanism and dust processing?
• RQ5 How do the collimation and asymmetry of Class 0 jets compare to those of Class II atomic jets, and what does this suggest about the universality of the launching mechanism?

Key findings

• Outflowing CO (2–1) emission was detected in all 21 Class 0 protostars, confirming that outflows are ubiquitous in this stage of star formation.
• Collimated high-velocity SiO (5–4) jets were detected in 67% of sources (12 out of 18 with sufficient signal-to-noise), with 77% of these also showing SO (5₆–4₅) emission.
• The median opening angles are 10° for SiO, 15° for SO, and 25° for CO, confirming an onion-like structure where the most collimated emission traces the innermost jet.
• SiO abundance relative to H₂ is $ >2.4 \times 10^{-7} $ to $ >5 \times 10^{-6} $ in most jets, indicating efficient release of 1%–10% of elemental silicon into the gas phase, consistent with dust-free winds.
• Jet mass-loss rates range from $ 7 \times 10^{-8} \, M_\odot \, \text{yr}^{-1} $ to $ 3 \times 10^{-6} \, M_\circ \, \text{yr}^{-1} $, which are up to five orders of magnitude higher than in Class II atomic jets.
• Jet power $ L_{\text{jet}} $ is 10%–50% of internal luminosity for 60% of jets, indicating efficient conversion of accretion energy into mechanical energy, with $ \dot{M}_{\text{jet}} \sim 0.1-0.5 \dot{M}_{\text{acc}} $, consistent with the jet-accretion correlation across stellar evolution stages.