Dynamical masses of YSOs with the VLBA: DYNAMO VLBA: Trigonometric parallaxes and proper motions of YSOs in Orion

TL;DR

This study uses VLBA radio observations to measure precise distances and motions of young stellar objects in Orion, refining the complex's 3D structure and calibrating Gaia data in obscured regions.

Contribution

It provides high-precision parallaxes and proper motions for YSOs in Orion, improving distance estimates and Gaia reference frame calibration.

Findings

Distances to Orion regions are between 380 and 440 pc.

VLBA astrometry achieves ~0.05 mas parallax precision.

Results show minimal Gaia parallax offsets and small proper motion differences.

Abstract

We present results from a multi-epoch Very Long Baseline Array (VLBA) survey of compact radio sources in the Orion complex, conducted within both the DYNAMO-VLBA and the GOBELINS projects. Our observations detected 216 compact radio sources, of which 58 yielded reliable multi-epoch astrometric solutions. For these sources, we derived trigonometric parallaxes and proper motions with typical precisions of about 0.05 mas and 0.10 mas yr$^{-1}$, respectively. The measured parallaxes range between 2.26 and 2.65 mas, corresponding to distances of 380 - 440 pc, and delineate the depth of the Orion star-forming complex. We determine mean distances of $405\pm16$ pc for NGC 2068, $403\pm5$ pc for NGC 2024, $407\pm12$ pc for the $\sigma$ Orionis region, $388.5\pm1.7$ pc for the Orion Nebula Cluster (ONC), and $438\pm12$ pc for L1641. A comparison with Gaia DR3 astrometry for 28 common sources reveals negligible mean parallax offsets ($\Delta\varpi=-0.02\pm0.01$ mas) and small systematic differences in proper motions ($\sim$0.07 mas yr$^{-1}$), likely due to residual rotation of the Gaia reference frame. Our results demonstrate the capability of high-precision radio astrometry to map embedded stellar populations and to provide an independent calibration of the Gaia reference system in obscured regions.