H2O maser motions and the distance of the star forming region G192.16-3.84

TL;DR

This study uses VLBI astrometry to measure the distance to the star-forming region G192.16-3.84 via H2O maser motions, revealing a closer distance than previous estimates and insights into its stellar and galactic dynamics.

Contribution

First precise parallax measurement of G192.16-3.84 using H2O masers, providing accurate distance and motion data for the region.

Findings

Distance to G192.16-3.84 is 1.52 kpc, shorter than previous estimates.

Detected bipolar outflow aligned NE-SW in the maser features.

Estimated mass of the circumstellar disk is approximately 10 solar masses.

Abstract

We present the results of astrometic observations of H2O masers associated with the star forming region G192.16-3.84 with the VLBI Exploration of Radio Astrometry (VERA). The H2O masers seem to be associated with two young stellar objects (YSOs) separated by \sim1200 AU as reported in previous observations. In the present observations, we successfully detected an annual parallax of 0.66 \pm 0.04 mas for the H2 O masers, which corresponds to a distance to G192.16-3.84 of D = 1.52 \pm 0.08 kpc from the Sun. The determined distance is shorter than the estimated kinematic distance. Using the annual parallax distance and the estimated parameters of the millimeter continuum emission, we estimate the mass of the disk plus circumstellar cloud in the southern young stellar object to be 10.0+4.3M\cdot. We also estimate the galactocentric distance and the peculiar motion -3.6 of G192.16-3.84, relative to a circular Galactic rotation: R\star = 9.99 \pm 0.08 kpc, Z\star = -0.10 \pm 0.01 kpc, and (U\star,V\star,W\star)=(-2.8\pm1.0,-10.5\pm0.3,4.9\pm2.7)[kms-1]respectively. The peculiar motion of G192.16-3.84 is within that typically found in recent VLBI astrometric results. The angular distribution and three-dimensional velocity field of H2O maser features associated with the northern YSO indicate the existence of a bipolar outflow with a major axis along the northeast-southwest direction.