HST far-ultraviolet imaging of DG Tauri

Fluorescent molecular hydrogen emission from the wide opening-angle outflow

¹ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: cschneider@hs.uni-hamburg.de
² Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
³ University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁴ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
⁵ The Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian Qu, 100871 Beijing, PR China

Received: 25 March 2013
Accepted: 1 July 2013

Abstract

One of the most thoroughly studied jets from all young stellar objects is the jet of DG Tau, which we imaged in the far-ultraviolet with the Hubble Space Telescope for the first time. These high spatial resolution images were obtained with long-pass filters and allow us to construct images tracing mainly H₂ 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 or 42 AU before their brightness strongly drops, and the opening angle is about 90°. Comparing our far-ultraviolet data with near-infrared data we find that the fluorescent H₂ emission probably 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.