The Orion fingers: Near-IR spectral imaging of an explosive outflow

TL;DR

This paper provides detailed near-infrared spectral imaging of the Orion BN/KL explosive outflow, revealing shock excitation and other features, with high spatial and spectral resolution to analyze outflow dynamics and excitation conditions.

Contribution

It offers the first high-resolution spectral imaging data of the Orion BN/KL outflow, including extinction measurements and excitation diagnostics, enhancing understanding of outflow mechanisms.

Findings

Shock excitation dominates H2 emission in the outflow.

Some features show signs of fluorescent excitation or J-shocks.

Detected tracers of PDR/ionization front near Trapezium stars.

Abstract

We present near-IR (1.1-2.4 micron) position-position-velocity cubes of the 500-year-old Orion BN/KL explosive outflow with spatial resolution 1" and spectral resolution 86 km/s. We construct integrated intensity maps free of continuum sources of 15 H2 and [Fe II] lines while preserving kinematic information of individual outflow features. Included in the detected H2 lines are the 1-0 S(1) and 1-0 Q(3) transitions, allowing extinction measurements across the outflow. Additionally, we present dereddened flux ratios for over two dozen outflow features to allow for the characterization of the true excitation conditions of the BN/KL outflow. All ratios show the dominance of shock excitation of the H2 emission, although some features exhibit signs of fluorescent excitation from stellar radiation or J-type shocks. We also detect tracers of the PDR/ionization front north of the Trapezium stars in [O I] and [Fe II] and analyze other observed outflows not associated with the BN/KL outflow.