HST/STIS observations of the RW Aurigae bipolar jet: mapping the physical parameters close to the source

TL;DR

This study uses high-resolution HST/STIS spectra to analyze the physical parameters of the RW Aurigae bipolar jet near its source, revealing similarities with other jets and symmetric mass outflow rates despite asymmetries.

Contribution

First detailed spectral diagnostic analysis of RW Aurigae jet showing symmetric mass outflow rates despite asymmetries in physical properties.

Findings

RW Aur jet is the second densest T Tauri outflow studied.

Physical parameters trend similar to HH 30 and DG Tau.

Mass outflow rates are similar in both lobes despite asymmetries.

Abstract

We present the results of new spectral diagnostic investigations applied to high-resolution long-slit spectra of the RW Aur bipolar jet obtained with HST/STIS. The spectra include the forbidden doublets [O I] 6300,6363 \AA, [S II] 6716,6731 \AA, and [N II] 6548, 6583 \AA that we utilized to determine electron density, electron temperature, hydrogen ionisation fraction, total hydrogen density, radial velocity and the mass outflow rate. We were able to extract the parameters as far as 3".9 in the red- and 2".1 in the blueshifted beam. The RW Aur jet appears to be the second densest outflow from a T Tauri star studied so far, but its other properties are quite similar to those found in other jets from young stars. The overall trend of the physical parameters along the first few arcseconds of the RW Aur jet is similar to that of HH 30 and DG Tau and this can reflect analogies in the mechanisms operating in that region, suggesting the same engine is accelerating the jets in the T Tauri stars with outflows. Our study of the RW Aur jet indicates for the first time that, despite the detected marked asymmetries in physical and kinematic properties between the two lobes, the mass outflow rates in the two lobes are similar. This appears to indicate that the central engine has constraining symmetries on both sides of the system, and that the observed asymmetries are probably due to different environmental conditions.