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

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 $405\pm 16$ pc for NGC 2068, $403\pm 5$ pc for NGC 2024, $407\pm 12$ pc for the $\ddot{I}ƒ$ Orionis region, $388.5\pm 1.7$ pc for the Orion Nebula Cluster (ONC), and $438\pm 12$ pc for L1641. A comparison with Gaia DR3 astrometry for 28 common sources reveals negligible mean parallax offsets ($\hat{I}”\varpi =-0.02\pm 0.01$ 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.

Accepeted for publication in A&A, 12 pages, 5 figures, 8 tables