Physical properties of the jet from DG Tauri on sub-arcsecond scales with HST/STIS

Maurri, L.; Bacciotti, F.; Podio, L.; Eislöffel, J.; Ray, T. P.; Mundt, R.; Locatelli, Ugo; Coffey, Deirdre

doi:10.1051/0004-6361/201117510

Cited by 42 publications

(90 citation statements)

References 44 publications

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“…In particular, we do not see evidence at our spectral resolution that high velocity material located close to the jet axis, has higher density than the jet streamlines at lower velocities on the border. This is in contrast with the onion-like structure predicted by the theoretical model and confirmed by high resolution observations of CTT jets (e.g., Maurri et al 2014), and may be due to the lack of angular resolution: in regions more distant from the driving source (like those probed here), shocks may have already destroyed the jet's onion-like structure. With regard to the spatial variations, all transitions peak at the same offsets from the source with the exception of the [S ii] and [Ca ii] lines, which -having critical densities <5 × 10 3 cm −3 -are probably quenched in the high density knots close to the star.…”

Section: Kinematics Vs Excitationsupporting

confidence: 57%

“…However, the total density could still be consistent with the predicted pattern if the ionization fraction in the LVC is smaller than in HVC. In this respect, we point out that a decrease in the fractional ionization with velocity has been observed in T Tauri stars (e.g., Maurri et al 2014). …”

Section: Origin Of the Lvcsupporting

confidence: 54%

“…Values in the range 10 4 −10 5 cm −3 are derived in DG Tau, HH30, and RW Aur (Maurri et al 2014;Hartigan & Morse 2007;Melnikov et al 2009), which are among the most active CTTs.…”

Section: Physical Parameters Mass Loss Rate and Comparison With Promentioning

confidence: 99%

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The small-scale HH34 IRS jet as seen by X-shooter

Nisini¹,

Giannini²,

Antoniucci³

et al. 2016

A&A

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Context. Atomic jets are a common phenomenon among young stars, being intimately related to disk accretion. Most studies have been performed on jets from pre-main sequence stars. However, to date very little detailed information has been gathered on jets from young embedded low mass sources (the so-called class I stars), especially in the inner jet region. Aims. We exploit a diagnostic analysis based on multiwave spectroscopic observations to infer kinematics and physical conditions of the inner region of the prototypical class I jet from HH34 IRS. Methods. We use a deep X-shooter spectrum covering the wavelength range 350−2300 nm at resolution between ∼8000 and ∼18 000 (i.e., ∆V ∼ 17−27 km s −1 ), which allows us to detect lines in a wide range of excitation conditions (from E up ∼ 8000 to ∼31 000 cm −1 ) and to study their kinematics. Statistical equilibrium and ionization models are adopted to derive the jet main physical parameters. Results. We separately derive the physical conditions for the extended high velocity jet (HVC, V r ∼ −100 km s −1 ) and for the low velocity and compact gas (LVC, V r ∼ −20−50 km s −1 ) located on-source. Close to the jet base (<200 AU from source) the HVC gas is mostly neutral (x e < 0.1) and very dense (n H > 5 × 10 5 cm −3 ). The LVC gas has the same density and A V as the HVC, but it is at least a factor of two colder. Iron abundance in the HVC is consistent with the solar value, while it is a factor of 3 subsolar in the LVC, suggesting an origin of the LVC gas from a dusty disk. From the derived total density we infer that the jet mass flux rate is >5 × 10 −7 M yr −1 . We find that the relationships between accretion luminosity and permitted line luminosity derived for T Tauri stars cannot be directly extended to class I sources embedded in reflection nebulae since the permitted lines are seen through scattered light. An accretion rate of ∼7 × 10 −6 M yr −1 is instead derived from an empirical relationship connectingṀ acc with L([O i])(HVC).Conclusions. The class I HH34 IRS jet at small scale shares many kinematical and physical properties with the jets from the most active classical T Tauri (CTT) stars. However, the HH34 IRS jet is denser as a consequence of the larger mass ejection rate with respect to typical values in CTTs jets. These findings suggests that the acceleration and excitation mechanisms in collimated jets are not influenced by evolution and are similar in CTTs and in still embedded sources with high accretion rates.

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Section: Kinematics Vs Excitationsupporting

confidence: 57%

Section: Origin Of the Lvcsupporting

confidence: 54%

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The small-scale HH34 IRS jet as seen by X-shooter

Nisini¹,

Giannini²,

Antoniucci³

et al. 2016

A&A

Self Cite

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“…The hydrogen density is calculated from nH = ne/χe, where χe is the ionization fraction of the gas. Although the ionization fraction of the jet appears to vary with position (Maurri et al 2014), an average ionization fraction of χe = 0.3 ± 0.1 is a reasonable approximation (Bacciotti et al 2000). This yields a hydrogen number density nH = 3.3 × 10 4 cm −3 .…”

Section: Jet Densitymentioning

confidence: 90%

Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

White

Bicknell

Sutherland

et al. 2015

Mon. Not. R. Astron. Soc.

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Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stages of their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellar jets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows driven by classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shockexcited mixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based on Reynolds decomposition of quantities measuring fundamental properties of the gas. In this model, the molecular wind from large disc radii provides a continual supply of material for entrainment. We calculate the total stress profile in the mixing layer, which allows us to estimate the dissipation of turbulent energy, and hence the luminosity of the layer. We utilize MAPPINGS IV shock models to determine the fraction of total emission that occurs in [Fe II] 1.644 µm line emission in order to facilitate comparison to previous observations of the young stellar object DG Tauri. Our model accurately estimates the luminosity and changes in mass outflow rate of the intermediate-velocity component of the DG Tau approaching outflow. Therefore, we propose that this component represents a turbulent mixing layer surrounding the well-collimated jet in this object. Finally, we compare and contrast our model to previous work in the field.

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“…Maurri et al 2014). If the jet is partially ionised, the atomic gas may further contribute to the mass-loss rate.…”

Section: Jet Physical and Dynamical Properties: H 2 Density And Mass-mentioning

confidence: 99%

The jet and the disk of the HH 212 low-mass protostar imaged by ALMA: SO and SO₂emission

Podio

Codella

Gueth

et al. 2015

A&A

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Context. The investigation of the disk formation and jet launching mechanism in protostars is crucial to understanding the earliest stages of star and planet formation. Aims. We aim to constrain the physical and dynamical properties of the molecular jet and disk of the HH 212 protostellar system at unprecedented angular scales, exploiting the capabilities of the Atacama Large Millimeter Array (ALMA). Methods. The ALMA observations of HH 212 in emission lines from sulfur-bearing molecules, SO 9 8 −8 7 , SO 10 11 −10 10 , SO 2 8 2,6 −7 1,7 , are compared with simultaneous CO 3−2, SiO 8−7 data. The molecules column density and abundance are estimated using simple radiative transfer models. Results. SO 9 8 −8 7 and SO 2 8 2,6 −7 1,7 show broad velocity profiles. At systemic velocity, they probe the circumstellar gas and the cavity walls. Going from low to high blue-and red-shifted velocities the emission traces the wide-angle outflow and the fast (∼100−200 km s −1 ), collimated (∼90 AU) molecular jet revealing the inner knots with timescales ≤50 yr. The jet transports a massloss rate ≥0.2−2×10 −6 M yr −1 , implying high ejection efficiency (≥0.03−0.3). The SO and SO 2 abundances in the jet are ∼10 −7 −10 −6 . SO 10 11 −10 10 emission is compact and shows small-scale velocity gradients, indicating that it originates partly from the rotating disk previously seen in HCO + and C 17 O, and partly from the base of the jet. The disk mass is ≥0.002−0.013 M and the SO abundance in the disk is ∼10 −8 −10 −7 . Conclusions. SO and SO 2 are effective tracers of the molecular jet in the inner few hundreds AU from the protostar. Their abundances indicate that 1−40% of sulfur is in SO and SO 2 due to shocks in the jet/outflow and/or to ambipolar diffusion at the wind base. The SO abundance in the disk is 3−4 orders of magnitude larger than in evolved protoplanetary disks. This may be due to an SO enhancement in the accretion shock at the envelope-disk interface or in spiral shocks if the disk is partly gravitationally unstable.

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Physical properties of the jet from DG Tauri on sub-arcsecond scales with HST/STIS

Cited by 42 publications

References 44 publications

The small-scale HH34 IRS jet as seen by X-shooter

The small-scale HH34 IRS jet as seen by X-shooter

Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

The jet and the disk of the HH 212 low-mass protostar imaged by ALMA: SO and SO₂emission

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Physical properties of the jet from DG Tauri on sub-arcsecond scales with HST/STIS

Cited by 42 publications

References 44 publications

The small-scale HH34 IRS jet as seen by X-shooter

The small-scale HH34 IRS jet as seen by X-shooter

Turbulent mixing layers in supersonic protostellar outflows, with application to DG Tauri

The jet and the disk of the HH 212 low-mass protostar imaged by ALMA: SO and SO2emission

Contact Info

Product

Resources

About

The jet and the disk of the HH 212 low-mass protostar imaged by ALMA: SO and SO₂emission