IGRINS Near-IR High-Resolution Spectroscopy of Multiple Jets around LkH$\alpha$ 234

TL;DR

This study uses high-resolution near-infrared spectroscopy to analyze multiple jets around the Herbig Be star LkHα 234, revealing new jets, complex kinematics, and shock-excited molecular hydrogen emission.

Contribution

First high-resolution IR spectroscopic analysis of multiple outflows around LkHα 234, discovering a new { extFeII} jet and detailed kinematic structures.

Findings

Detected a new { extFeII} jet driven by VLA 3B.

Revealed complex velocity structures consistent with bow shock models.

Found H$_{2}$ emission from shock-excited, thermally heated gas at 2500-3000 K.

Abstract

We present the results of high-resolution near-IR spectroscopy toward the multiple outflows around the Herbig Be star Lk{\Ha} 234 using the Immersion Grating Infrared Spectrograph (IGRINS). Previous studies indicate that the region around Lk{\Ha} 234 is complex, with several embedded YSOs and the outflows associated with them. In simultaneous H$-$ and K$-$band spectra from HH 167, we detected 5 {\FeII} and 14 H$_{2}$ emission lines. We revealed a new {\FeII} jet driven by radio continuum source VLA 3B. Position-velocity diagrams of H$_{2}$ 1$-$0 S(1) $\lambda$2.122 $\micron$ line show multiple velocity peaks. The kinematics may be explained by a geometrical bow shock model. We detected a component of H$_{2}$ emission at the systemic velocity (V$_{LSR}$ $=$ $-$10.2 {\kms}) along the whole slit in all slit positions, which may arise from the ambient photodissociation region. Low-velocity gas dominates the molecular hydrogen emission from knots A and B in HH 167, which is close to the systemic velocity, {\FeII} emission lines are detected at farther from the systemic velocity, at V$_{LSR}$ $=$ $-$100 $-$ $-$130 {\kms}. We infer that the H$_{2}$ emission arises from shocked gas entrained by a high-velocity outflow. Population diagrams of H$_{2}$ lines imply that the gas is thermalized at a temperature of 2,500 $-$ 3,000 K and the emission results from shock excitation.