VLBA determinations of the distances to nearby star-forming regions

TL;DR

This study uses VLBA observations to precisely measure distances to nearby star-forming regions, revealing complex structures and multiple star-formation sites within Ophiuchus.

Contribution

First precise parallax measurements of young stars in Taurus and Ophiuchus, showing complex spatial structures and multiple star-formation sites.

Findings

Taurus is about 140 pc away with a 20 pc depth.

Ophiuchus contains two separate star-forming sites at 120 and 160 pc.

Ophiuchus's depth is only a few parsecs, indicating multiple sites along the line of sight.

Abstract

Using phase-referenced multi-epoch Very Long Baseline Array observations, we have measured the trigonometric parallax of several young stars in the Taurus and Ophiuchus star-forming regions with unprecedented accuracy. The mean distance to the Taurus complex was found to be about 140 pc, and its depth around 20 pc, comparable to the linear extent of Taurus on the plane of the sky. In Ophiuchus, 4 sources were observed so far. Two of them were found to be at about 160 pc (the distance traditionally attributed to Ophiuchus), while the other 2 are at about 120 pc. Since the entire Ophiuchus complex is only a few parsecs across, this difference is unlikely to reflect the depth of the region. Instead, we argue that two physically unrelated sites of star-formation are located along the line of sight toward Ophiuchus.