Multi-wavelength observations of a nearby multi-phase interstellar cloud

TL;DR

This study uses high-resolution multi-wavelength spectroscopy to analyze the physical and velocity structure of a nearby multi-phase interstellar cloud, revealing complex temperature, ionization, and dynamical features influenced by a past supernova event.

Contribution

It provides a detailed characterization of the multi-phase interstellar medium near HD102065, linking observed gas properties to supernova impact from the Sco-Cen OB association.

Findings

Detection of gas components across a wide temperature range.

Identification of hot, highly-ionized gas at negative velocities.

Evidence linking the cloud's disturbance to a supernova from Sco-Cen.

Abstract

High-resolution spectroscopic observations (UV HST/STIS and optical) are used to characterize the physical state and velocity structure of the multiphase interstellar medium seen towards the nearby (170 pc) star HD102065, located behind the tail of a cometary-shaped, infrared cirrus-cloud, in the area of interaction between the Sco-Cen OB association and the Local Bubble. We analyze interstellar components present along the line of sight by fitting multiple transitions from CO, CH, CH+, C I, S I, Fe I, Mg I, Mg II, Mn II, P II, Ni II, C II, N I, O I, Si III, C IV, and Si IV. The absorption spectra are complemented by H I, CO and C II emission-line spectra, H$_2$ column-densities derived from FUSE spectra, and IRAS images. Gas components of a wide range of temperatures and ionization states are detected along the line of sight. Most of the hydrogen column-density is in cold, diffuse, molecular gas at low LSR velocity. This gas is mixed with traces of warmer molecular gas traced by H2 in the J>2 levels, in which the observed CH+ must be formed. We also identify three distinct components of warm gas at negative velocities down to -20 km/s. The temperature and gas excitation are shown to increase with increasing velocity shift from the bulk of the gas. Hot gas at temperatures of several 10^5 K is detected in the most negative velocity component in the highly-ionized species. This hot gas is also detected in very strong lines of less-ionized species (Mg II, Si II* and C II*) for which the bulk of the gas is cooler. We relate the observational results to evidence for dynamical impact of the Sco-Cen stellar association on the nearby ISM. We propose a scenario where the cirrus cloud has been hit a few 10^5 yr ago by a supernova blast wave originating from the Lower Centaurus Crux group of the Sco-Cen association.