Pulling back the curtain on shocks and star-formation in NGC 1266 with Gemini-NIFS

TL;DR

This study uses Gemini NIFS K-band observations to analyze shock excitation and residual star formation in the central region of NGC 1266, revealing thermal H$_2$ emission and localized star formation activity.

Contribution

First spatially resolved observation of shock structures in NGC 1266 using bright H$_2$ lines, linking shocks to galaxy evolution processes.

Findings

Thermal H$_2$ emission indicates shock excitation at ~2000 K.

Star formation is confined to the nucleus with a rate of 0.7 M$_\\odot$/yr.

Cold molecular gas shows little ongoing star formation.

Abstract

We present Gemini near-infrared integral field spectrograph (NIFS) K-band observations of the central 400 pc of NGC 1266, a nearby (D$\approx$30 Mpc) post-starburst galaxy with a powerful multi-phase outflow and a shocked ISM. We detect 7 H$_2$ ro-vibrational emission lines excited thermally to $T$$\sim$2000 K, and weak Br$\gamma$ emission, consistent with a fast C-shock. With these bright H$_2$ lines, we observe the spatial structure of the shock with an unambiguous tracer for the first time. The Br$\gamma$ emission is concentrated in the central $\lesssim$100 pc, indicating that any remaining star-formation in NGC 1266 is in the nucleus while the surrounding cold molecular gas has little on-going star-formation. Though it is unclear what fraction of this Br$\gamma$ emission is from star-formation or the AGN, assuming it is entirely due to star-formation we measure an instantaneous star-formation rate of 0.7 M$_\odot$ yr$^{-1}$, though the star-formation rate may be significantly higher in the presence of additional extinction. NGC 1266 provides a unique laboratory to study the complex interactions between AGN, outflows, shocks, and star-formation, all of which are necessary to unravel the evolution of the post-starburst phase.