17 February 2017
Venue: GO Jones Room 610
Series: Astronomy Unit Seminars
Speaker: Jan Forbrich
Host: Izaskun Jimenez-Serra
Abstract: The sensitivity upgrades of both the NRAO Very Large Array (VLA) and the NRAO 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. As such, these fantastic observatories also serve as precursor experiments for the Square Kilometre Array. I will mainly present a deep VLA and VLBA radio survey of the Orion Nebula Cluster (ONC), where we have found 556 compact radio sources, a sevenfold increase over previous studies, and intricate detail on the radio emission of proplyds. We can now better disentangle thermal and nonthermal radio emission by assessing spectral indices, polarization, variability, and brightness temperatures (VLBA). With simultaneous radio-X-ray time domain information (Chandra), this project is providing unprecedented constraints on the magnetospheric activity of YSOs across a wide mass range, including the massive Trapezium stars and their impact on the interstellar medium. Starting with Orion, 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.