2006/10/30 by W. H. T. Vlemmings, Hayley Bignall, H. E. Bignall +1 · 1 citation
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Cosmic Phenomena #Circular polarization #Galaxy #Gamma-ray bursts and supernovae #Green Bank Telescope #Magnetic field #Maser #Optics #Physics #Polarization (electrochemistry) #Scintillation #Telescope #Zeeman effect #astro-ph
paper · pdf · doi:10.1086/510515
published as Astrophys.J.656:198-205,2007 · 8 pages, 7 figures; accepted for publication in ApJ
arxiv created 2006/10/30 · openalex publication_date 2007/02/03 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present observations of the 22 GHz H 2 O megamasers in the circumnuclear disk of NGC 3079 obtained with the Green Bank Telescope. The data are analyzed for circular polarization due to the Zeeman-induced splitting of the H 2 O maser lines. No circular polarization is detected, and we derive a 1 σ upper limit of 11 mG for the toroidal magnetic field at ~0.64 pc from the central black hole. This is the tightest upper limit for the magnetic field around a black hole to date. We use the magnetic field limit to derive an estimate of the mass accretion onto the central black hole. In addition to the polarimetric results, we present an observation of rapid variability in the maser lines, which we explain as weak interstellar scintillation. From the scintillation parameters, we estimate an intrinsic size of the mostly saturated maser features of ~12 μas. This is consistent with models assuming a thick, clumpy accretion disk.