The [Ne III] Jet of DG Tau and its Ionization Scenarios

Abstract

Forbidden neon emission from jets of low-mass young stars can be used to probe the underlying high-energy processes in these systems. We analyze spectra of the jet of DG Tau obtained with the Very Large Telescope/X-Shooter spectrograph in 2010. [Ne III] $\lambda$3869 is clearly detected in the innermost 3" microjet and the outer knot located at $\sim$6".5. The velocity structure of the inner microjet can be decomposed into the low-velocity component (LVC) at $\sim -70$ km/s and the high-velocity component (HVC) at $\sim -180$ km/s. Based on the observed [Ne III] flux and its spatial extent, we suggest the origins of the [Ne III] emission regions and their relation with known X-ray sources along the jet. The flares from the hard X-ray source close to the star may be the main ionization source of the innermost microjet. The fainter soft X-ray source at 0".2 from the star may provide sufficient heating to help to sustain the ionization fraction against the recombination in the flow. The outer knot may be reionized by shocks faster than 100 km/s such that [Ne III] emission reappears and that the soft X-ray emission at 5".5 is produced. Velocity decomposition of the archival Hubble Space Telescope spectra obtained in 1999 shows that the HVC had been faster, with a velocity centroid of $\sim -260$ km/s. Such a decrease in velocity may potentially be explained by the expansion of the stellar magnetosphere, changing the truncation radius and thus the launching speed of the jet. The energy released by magnetic reconnections during relaxation of the transition can heat the gas up to several tens of megakelvin and provide the explanation for on-source keV X-ray flares that ionize the neon microjet.

References in corpus (17)

• An Optical Spectroscopic Study of T Tauri Stars. I. Photospheric Properties
• X-ray Emission from T Tauri Stars and the Role of Accretion: Inferences from the XMM-Newton Extended Survey of the Taurus Molecular Cloud
• X-ray flares in Orion young stars. I. Flare characteristics
• Neon Fine-Structure Line Emission By X-ray Irradiated Protoplanetary Disks
• Discovery of a bipolar X-ray jet from the T Tauri star DG Tau
• T Tauri Jet Physics Resolved Near The Launching Region with the Hubble Space Telescope
• X-Ray flares in Orion Young Stars. II. Flares, Magnetospheres, and Protoplanetary Disks
• The nature of the soft X-ray source in DG Tau
• An outflow origin of the [NeII] emission in the T Tau triplet
• A Micro Molecular Bipolar Outflow From HL Tau
• Revealing the fastest component of the DG Tau outflow through X-rays
• Multi-epoch Sub-arcsecond [Fe II] Spectroimaging of the DG Tau Outflows with NIFS. I. First data epoch
• ESO-H$\alpha$~574 and Par-Lup3-4 Jets: Exploring the spectral, kinematical and physical properties
• Fine-Structure Line Emission from the Outflows of Young Stellar Objects
• Recollimation boundary layers as X-ray sources in young stellar jets
• Velocity-Resolved [Ne III] from X-Ray Irradiated Sz 102 Microjets
• Numerical simulations of stellar jets and comparison between synthetic and observed maps: clues to the launch mechanism

Cited by in corpus (7)

• X-ray Super-Flares From Pre-Main Sequence Stars: Flare Energetics And Frequency
• A Unified Model for Bipolar Outflows from Young Stars: Kinematic Signatures of Jets, Winds, and Their Magnetic Interplay with the Ambient Toroids
• Hydrogen Emission from Accretion and Outflow in T Tauri Stars
• Time-Variable Jet Ejections from RW Aur A, RY Tau and DG Tau
• Revealing Ionization Conditions of Sz 102 with Spatially Resolved [Ne III] Microjets
• JOYS: JWST MIRI/MRS spectra of the inner 500 au region of the L1527 IRS bipolar outflow
• Variability of the DG Tau Forbidden Emission Line Low Velocity Component