Investigating the asymmetry of young stellar outflows: Combined MUSE-X-shooter study of the Th 28 jet

TL;DR

This study combines integral field and high-resolution spectroscopy to analyze the asymmetries in the bipolar jet of Th 28, revealing intrinsic differences close to the source and refining mass accretion rate estimates.

Contribution

It provides the first detailed diagnostic analysis of jet asymmetries in Th 28 using combined MUSE and X-shooter data, highlighting intrinsic asymmetries near the source.

Findings

Blue-shifted jet has higher electron temperature and ionisation fraction.

Densities in the blue-shifted jet are about twice those in the red-shifted jet.

Mass accretion rate is significantly higher than previous estimates.

Abstract

Characterising stellar jet asymmetries is key to setting robust constraints on jet launching models and improving our understanding of the underlying mechanisms behind jet launching. We aim to characterise the asymmetric properties of the bipolar jet coming from the Classical T Tauri Star Th 28. We combined data from integral field spectroscopy with VLT/MUSE and high-resolution spectra from VLT/X-shooter to map the optical emission line ratios in both jet lobes. We carried out a diagnostic analysis of these ratios to compare the density, electron temperature, and ionisation fraction within both lobes. The mass accretion rate was derived from the emission lines at the source and compared with the mass outflow rate derived for both lobes, using the estimated densities and measured [O I]6300 and [S II ]6731 luminosities. The blue-shifted jet exhibits a significantly higher electron temperature and moderately higher ionisation fraction than the red-shifted jet. In contrast to previous studies, we also estimated higher densities in the blue-shifted jet by a factor of ~2. These asymmetries are traced to within 160 au of the source in the line ratio maps. We estimate the mass accretion rate onto the central star and compare this with estimates of the mass outflow rates through each side of the jet. The emission line maps and diagnostic results suggest that the jet asymmetries originate close to the source and are likely to be intrinsic to the jet. Furthermore, the combined dataset offers access to a broad array of accretion tracers. In turn, this enables a more accurate estimation of the mass accretion rate, revealing a value of Macc that is higher by a factor >350 than would otherwise be determined. Supplementary figures and tables are available via a public Zenodo repository (doi:10.5281/zenodo.13373809).