Hubble Space Telescope scale 3D simulations of MHD disc winds: a rotating two-component jet structure

Staff, Jan E.; Koning, Nico; Ouyed, Rachid; Thompson, Andrew

doi:10.1093/mnras/stu2392

Cited by 32 publications

(46 citation statements)

References 48 publications

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“…Numerical simulations have shown that several disruptive effects, for instance shocks (Fendt 2011) or plasma instability (Staff et al 2015) can indeed affect the rotational signature from YSO jets. These effects should be mitigated in our case, as our rotation measurements also include Fig .…”

Section: Interpretation Of the Jet Rotationmentioning

confidence: 99%

Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii

Mertens

Lobanov

Walker

et al. 2016

A&A

217

243

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Context. Very long baseline interferometry (VLBI) imaging of radio emission from extragalactic jets provides a unique probe of physical mechanisms governing the launching, acceleration, and collimation of relativistic outflows. Aims. VLBI imaging of the jet in the nearby active galaxy M 87 enables morphological and kinematic studies to be done on linear scales down to ∼ 100 Schwarzschild radii (R s ). Methods. The two-dimensional structure and kinematics of the jet in M 87 (NGC 4486) have been studied by applying the Waveletbased Image Segmentation and Evaluation (WISE) method to 11 images obtained from multi-epoch Very Long Baseline Array (VLBA) observations made in January-August 2007 at 43 GHz (λ = 7 mm).Results. The WISE analysis recovers a detailed two-dimensional velocity field in the jet in M 87 at sub-parsec scales. The observed evolution of the flow velocity with distance from the jet base can be explained in the framework of MHD jet acceleration and Poynting flux conversion. A linear acceleration regime is observed up to z obs ∼ 2 mas. The acceleration is reduced at larger scales, which is consistent with saturation of Poynting flux conversion. Stacked cross correlation analysis of the images reveals a pronounced stratification of the flow. The flow consists of a slow, mildly relativistic layer (moving at β ∼ 0.5 c), associated either with instability pattern speed or an outer wind, and a fast, accelerating stream line (with β ∼ 0.92, corresponding to a bulk Lorentz factor γ ∼ 2.5). A systematic difference of the apparent speeds in the northern and southern limbs of the jet is detected, providing evidence for jet rotation. The angular velocity of the magnetic field line associated with this rotation suggests that the jet in M87 is launched in the inner part of the disk, at a distance r 0 ∼ 5 R s from the central engine.Conclusions. The combined results of the analysis imply that MHD acceleration and conversion of Poynting flux to kinetic energy play the dominant roles in collimation and acceleration of the flow in M 87.

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Section: Interpretation Of the Jet Rotationmentioning

confidence: 99%

Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii

Mertens

Lobanov

Walker

et al. 2016

A&A

217

243

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“…Note also the recollimation of the jet half way down the flow. From Staff et al [2015] reproduced with permission c OUP.…”

Section: Mhd Outflow Basicsmentioning

confidence: 99%

The Role of Magnetic Fields in Protostellar Outflows and Star Formation

Pudritz

Ray

2019

Front. Astron. Space Sci.

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The role of outflows in the formation of stars and the protostellar disks that generate them is a central question in astrophysics. Outflows are associated with star formation across the entire stellar mass spectrum. In this review, we describe the observational, theoretical, and computational advances on magnetized outflows, and their role in the formation of disks and stars of all masses in turbulent, magnetized clouds. The ability of torques exerted on disks by magnetized winds to efficiently extract and transport disk angular momentum was developed in early theoretical models and confirmed by a variety of numerical simulations. The recent high resolution Atacama Large Millimeter Array (ALMA) observations of disks and outflows now confirm several key aspects of these ideas, e.g. that jets rotate and originate from large regions of their underlying disks. New insights on accretion disk physics show that magneto-rotational instability (MRI) turbulence is strongly damped, leaving magnetized disk winds as the dominant mechanism for transporting disk angular momentum. This has major consequences for star formation, as well as planet formation. Outflows also play an important role in feedback processes particularly in the birth of low mass stars and cluster formation. Despite being almost certainly fundamental to their production and focusing, magnetic fields in outflows in protostellar systems, and even in the disks, are notoriously difficult to measure. Most methods are indirect and lack precision, as for example, when using optical/near-infrared line ratios. Moreover, in those rare cases where direct measurements are possible -where synchrotron radiation is observed, one has to be very careful in interpreting derived values. Here we also explore what is known about magnetic fields from observations, and take a forward look to the time when facilities such as SPIRou and the SKA are in routine operation.

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“…Indeed, shocks and/or nonstationary ejection may significantly alter the apparent rotation of the flow, either amplifying it (Fendt et al 2011) or even reversing it (Sauty et al 2012) owing to the exchange of angular momentum between the flow and the magnetic field. Also, Staff et al (2015) recently presented 3D magnetohydrodynamic simulations of disk winds where the less opened magnetic field configuration results in a wide, two-component jet. They show that kink mode creates a narrow corkscrew-like jet with regions in which jet rotation at ±2 au from its axis is opposite to the disk.…”

Section: Implications For Jet Rotation Studiesmentioning

confidence: 99%

ALMA observations of the Th 28 protostellar disk

Louvet

Dougados

Cabrit

et al. 2016

A&A

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Aims. Recently, differences in Doppler shifts across the base of four close classical T Tauri star jets have been detected with the HST in optical and near-ultraviolet (NUV) emission lines, and these Doppler shifts were interpreted as rotation signatures under the assumption of steady state flow. To support this interpretation, it is necessary that the underlying disks rotate in the same sense. Agreement between disk rotation and jet rotation determined from optical lines has been verified in two cases and rejected in one case. Meanwhile, the near-ultraviolet lines, which may trace faster and more collimated inner spines of the jet than optical lines, either agree or show no clear indication. We propose to perform this test on the fourth system, Th 28. Methods. We present ALMA high angular resolution Band 7 continuum, 12 CO(3−2) and 13 CO(2−1) observations of the circumstellar disk around the T Tauri star Th 28. Results. The sub-arcsecond angular resolution (0.46 × 0.37 ) and high sensitivity reached enable us to detect, in CO and continuum, clear signatures of a disk in Keplerian rotation around Th 28. The 12 CO emission is clearly resolved, allowing us to derive estimates of disk position angle and inclination. The large velocity separation of the peaks in 12 CO, combined with the resolved extent of the emission, indicate a central stellar mass in the range 1−2 M . The rotation sense of the disk is well detected in both 13 CO and 12 CO emission lines, and this direction is opposite to that implied by the transverse Doppler shifts measured in the optical lines of the jet. Conclusions. The Th 28 system is now the second system, among the four investigated so far, where counter-rotation between the disk and the optical jet is detected. These findings imply either that optical transverse velocity gradients detected with HST do not trace jet rotation or that modeling the flow with the steady assumption is not valid. In both cases jet rotation studies that rely solely on optical lines are not suitable to derive the launching radius of the jet.

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Hubble Space Telescope scale 3D simulations of MHD disc winds: a rotating two-component jet structure

Cited by 32 publications

References 48 publications

Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii

Kinematics of the jet in M 87 on scales of 100–1000 Schwarzschild radii

The Role of Magnetic Fields in Protostellar Outflows and Star Formation

ALMA observations of the Th 28 protostellar disk

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