VLBA13A-183

Probing Magnetic Fields in the Accretion Disks of Supermassive Black Holes

Abstract

We propose polarimetric observations of H2O megamasers at 22 GHz in the accretion disks of six supermassive black holes using the High Sensitivity Array (HSA) for the first time. Magnetic fields seem to play a crucial role for many aspects of the accretion process in Active Galactic Nuclei (AGNs). To date, there has been no direct observational evidence of magnetic fields around supermassive black holes. Sensitive HSA observations of the H2O megamasers will resolve the maser features in the disks and directly probe magnetic field strength and morphology for the numerous high velocity features and systemic features in accretion disks. The detection of magnetic fields even in one of the circumnuclear disks can make a big step toward addressing long standing mysteries in Astrophysics: How does magnetic field affect the jet formation in AGNs? How is the disk threaded by magnetic fields? We propose to measure polarizations down to 2% in fairly weak (40 mJy) lines, or 300 mG fields (observations will be sensitive to much smaller polarization fractions in the many brighter masers, making fields as weak as 2.5 mG detectable). This sensitivity to magnetic fields requires 12 hours per object (including overheads), or 72 hours total.

Investigators

Name	Institution
Jeremy Darling	Colorado at Boulder, University of
Nikta Amiri *	Colorado at Boulder, University of

* indicates the PI