Radio continuum emission from knots in the DG Tauri jet

¹ Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, A. P. 3-72, (Xangari), 58089 Morelia, Michoacán México
e-mail: l.rodriguez@crya.unam.mx
² Astronomy Department, Faculty of Science, King Abdulaziz University, PO Box 80203, 21589 Jeddah, Saudi Arabia
³ Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apdo. Postal 70-543, CP. 04510, D. F., México
⁴ Instituto de Astronomía, Universidad Nacional Autónoma de México, postbox. Postal 70-264, CP. 04510, D. F., México
⁵ Departament de Física i Enginyeria Nuclear, EUETIB, Universitat Politècnica de Catalunya, Compte d’Urgell 187, 08036 Barcelona, Spain
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 31 August 2011
Accepted: 4 November 2011

Abstract

Context. HH 158, the jet from the young star DG Tau, is one of the few sources of its type where jet knots have been detected at optical and X-ray wavelengths.

Aims. We aim to search for radio knots to compare them with the optical and X-ray knots. We also aim to model the emission from the radio knots.

Methods. We analyzed archive data and also obtained new Very Large Array observations of this source, as well as an optical image to measure the present position of the knots. We furthermore modeled the radio emission from the knots in terms of shocks in a jet with intrinsically time-dependent ejection velocities.

Results. We detected radio knots in the 1996.98 and 2009.62 VLA data. These radio knots are, within error, coincident with optical knots. We also modeled satisfactorily the observed radio flux densities as shock features from a jet with intrinsic variability. All observed radio, optical, and X-ray knot positions can be intepreted as four successive knots, ejected with a period of 4.80 years and traveling away from the source with a velocity of 198 km s^-1 in the plane of the sky.

Conclusions. The radio and optical knots are spatially correlated and our model can explain the observed radio flux densities. However, the X-ray knots do not appear to have optical or radio counterparts and their nature remains poorly understood.