The interstellar medium towards the Ara OB1 region

TL;DR

This study uses high-resolution absorption line measurements of NaI and CaII towards stars in the Ara OB1 region to map interstellar gas structures and their distances, revealing associations with local cavities and expanding shells.

Contribution

It provides detailed velocity and distance mapping of interstellar medium components in the Ara OB1 region using high-resolution spectroscopy.

Findings

Identified local gas associated with the Lupus-Norma cavity at 100-485 pc.

Detected interstellar features at 570-800 pc.

Linked a wide-spread feature to the GSH 337+00-05 HI shell at ~530 pc.

Abstract

We present high resolution (R ~ 4 km/s) absorption measurements of the interstellar NaI and CaII lines measured towards 14 early-type stars of distance 123 pc - 1650 pc, located in the direction of the Ara OB1 stellar cluster. The line profiles can broadly be split into four distinct groupings of absorption component velocity, and we have attempted to identify an origin and distance to each of these interstellar features. For gas with absorption covering the velocity range -10 km/s < V_helio < +10 km/s, we can identify the absorbing medium with local gas belonging to the Lupus-Norma interstellar cavity located between 100 and 485 pc in this galactic direction. Gas with velocities spanning the range -20 km/s < V_helio < +20 km/s is detected towards stars with distances of 570-800 pc. We identify a wide-spread interstellar feature at V_helio ~ -15 km/s with the expanding HI shell called GSH 337+00-05, which is now placed at a distance of ~530 pc.