The Interstellar Medium of IRAS 08572+3915 NW: H3+ and Warm High Velocity CO

TL;DR

This study reports the first extragalactic detection of H3+ and analyzes CO absorption in IRAS 08572+3915 NW, revealing complex molecular components likely linked to energetic nuclear activity.

Contribution

It provides the first detection of H3+ in an extragalactic galaxy and characterizes warm, high-velocity CO components near an active nucleus.

Findings

First extragalactic H3+ detection.

Identification of warm, high-velocity CO components.

Comparison with Galactic center molecular features.

Abstract

We confirm the first detection of the molecular ion H3+ in an extragalactic object, the highly obscured ultraluminous galaxy IRAS 08572+3915 NW. We also have detected absorption lines of the fundamental band of CO in this galaxy. The CO absorption consists of a cold component close to the systemic velocity and warm, highly blueshifted and redshifted components. The warm blueshifted component is remarkably strong and broad and extends at least to -350 km/s. Some analogies can be drawn between the H3+ and cold CO in IRAS08572+3915 NW and the same species seen toward the Galactic center. The profiles of the warm CO components are not those expected from a dusty torus of the type thought to obscure active galactic nuclei. They are probably formed close to the dust continuum surface near the buried and active nucleus and are probably associated with an unusual and energetic event there.