Dr. J. Forbrich

University of Hertfordshire, UK

The Orion Radio All-Stars: new insights into YSO radio emission, using the VLA, VLBA, and ALMA

Abstract : With significant new observing capabilities, centimeter-wavelength radio astronomy is currently in a renaissance leading up to the advent of the Square Kilometre Array (SKA). The sensitivity upgrades of both the NRAO Very Large Array (VLA) and the Very Long Baseline Array (VLBA) have begun to provide us with a much improved perspective on stellar centimeter radio emission, particularly concerning young stellar objects (YSOs) and ultracool dwarfs. For the first time we now have systematic access to the radio time domain. I will mainly present a deep VLA and VLBA radio survey of the Orion Nebula Cluster (ONC), where we have found hundreds of compact radio sources, a sevenfold increase over previous studies, and intricate detail on the radio emission of proplyds. With simultaneous radio-X-ray time domain information (Chandra), this project is providing first constraints on YSO radio flares and their relation with X-ray flares, as well as improved constraints on the overall high-energy irradiation of their surroundings, including protoplanetary disks. Our astrometric follow-up of all identified VLA targets in Orion is the largest VLBA survey for YSO emission to date. Other than providing a nonthermal census, I will additionally discuss the use of the VLBA for precision stellar astrometry in the Gaia era, highlighting how VLBI astrometry is allowing us to extend the Gaia sample of YSOs and ultracool dwarfs by including embedded objects, distant obscured sources in the Galactic plane, and faint ultracool dwarfs, while providing important opportunities for astrometric cross-calibration. I will conclude with a first look at the millimeter continuum emission of the Orion radio stars in the inner ONC.