Spatially Extended Brackett Gamma Emission in the Environments of Young Stars

TL;DR

This study uses K-band IFU spectroscopy to spatially resolve Brγ emission in eight young stars, revealing extended emission linked to outflows and Herbig-Haro objects, and comparing mass outflow and accretion rates.

Contribution

First spatially resolved study of Brγ emission in young stellar objects, linking emission structures to outflows and Herbig-Haro flows.

Findings

Extended Brγ emission often aligns with known outflows.

Extended emission can constitute over 20% of flux in certain velocities.

Total extended Brγ emission is usually less than 10% of the total flux.

Abstract

The majority of atomic hydrogen Br{\gamma} emission detected in the spectra of young stellar objects (YSOs) is believed to arise from the recombination regions associated with the magnetospheric accretion of circumstellar disk material onto the forming star. In this paper, we present the results of a K-band IFU spectroscopic study of Br{\gamma} emission in eight young protostars: CW Tau, DG Tau, Haro 6-10, HL Tau, HV Tau C, RW Aur, T Tau and XZ Tau. We spatially resolve Br{\gamma} emission structures in half of these young stars and find that most of the extended emission is consistent with the location and velocities of the known Herbig-Haro flows associated with these systems. At some velocities through the Br{\gamma} line profile, the spatially extended emission comprises 20% or more of the integrated flux in that spectral channel. However, the total spatially extended Br{\gamma} is typically less than ~10% of the flux integrated over the full emission profile. For DG Tau and Haro 6-10 S, we estimate the mass outflow rate using simple assumptions about the hydrogen emission region, and compare this to the derived mass accretion rate. We detect extended Br{\gamma} in the vicinity of the more obscured targets in our sample and conclude that spatially extended Br{\gamma} emission may exist toward other stars, but unattenuated photospheric flux probably limits its detectability.