HST FUV imaging of DG Tau: Fluorescent molecular hydrogen emission from the wide angle outflow

Abstract

One of the best-studied jets from all young stellar objects is the jet of DG Tau, which we imaged in the FUV with HST for the first time. These high spatial resolution images were obtained with long-pass filters and allow us to construct images tracing mainly molecular hydrogen and C IV emission. We find that the H2 emission appears as a limb-brightened cone with additional emission close to the jet axis. The length of the rims is about 0.3 arcsec or 42 AU (proj.) before their brightness strongly drops, and the opening angle is about 90 deg. Comparing our FUV data with near-IR data we find that the fluorescent H2 emission likely traces the outer, cooler part of the disk wind while an origin of the H2 emission in the surface layers (atmosphere) of the (flared) disk is unlikely. Furthermore, the spatial shape of the H2 emission shows little variation over six years which suggests that the outer part of the disk wind is rather stable and probably not associated with the formation of individual knots. The C IV image shows that the emission is concentrated towards the jet axis. We find no indications for additional C IV emission at larger distances, which strengthens the association with the X-ray emission observed to originate within the DG Tau jet.

9 pages, 5 figures, accepted for publication in A&A

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• The UV Perspective of Low-Mass Star Formation
• Recollimation boundary layers as X-ray sources in young stellar jets
• The [Ne III] Jet of DG Tau and its Ionization Scenarios
• HST UV Spectroscopy of the Planet-Hosting T Tauri Star PDS 70
• UV Fluorescence Traces Gas and LyA Evolution in Protoplanetary Disks
• Velocity-Resolved [Ne III] from X-Ray Irradiated Sz 102 Microjets
• A Theoretical Model of X-ray Jets from Young Stellar Objects
• Revealing Ionization Conditions of Sz 102 with Spatially Resolved [Ne III] Microjets
• Photoevaporation Can Reproduce Extended ${\mathrm{H}}_2$ Emission from Protoplanetary Disks Imaged by JWST MIRI
• Evidence of a Disk-wind Origin for Fluorescent H${}_2$ in Classical T Tauri Stars