P-Cygni Profiles of Molecular Lines toward Arp 220 Nuclei

TL;DR

This study uses high-resolution (sub)millimeter observations to identify P-Cygni profiles in molecular lines in Arp 220, revealing outflows of molecular gas from the galaxy's nuclei.

Contribution

It presents the first detection of P-Cygni profiles in molecular lines toward Arp 220's nuclei, indicating molecular outflows at ~100 km/s.

Findings

Detection of P-Cygni profiles in HCO+ and CO lines.

Evidence of molecular outflows from the nuclei.

Outflows likely clear the nuclear regions.

Abstract

We report ~100 pc (0.3") resolution observations of (sub)millimeter HCO+ and CO lines in the ultraluminous infrared galaxy Arp 220. The lines peak at two merger nuclei, with HCO+ being more spatially concentrated than CO. Asymmetric line profiles with blueshifted absorption and redshifted emission are discovered in HCO+(3-2) and (4-3) toward the two nuclei and in CO(3-2) toward one nucleus. We suggest that these P-Cygni profiles are due to ~100 km/s outward motion of molecular gas from the nuclei. This gas is most likely outflowing from the inner regions of the two nuclear disks rotating around individual nuclei, clearing the shroud around the luminosity sources there.