VLBA15A-326

Sizing up Sgr A*: Accurate Measurement of Intrinsic Size and Shape at 3mm

Abstract

Knowledge of the intrinsic size and orientation of Sagittarius A*, the radio source associated with the supermassive BH at the center of our Galaxy, is important in constraining the spin and jet axis of the black hole and the nature of the emission region. At an observing frequency of 3mm, the expected intrinsic size of the emission region is $\sim$10 $R_S$, just outside the event horizon shadow region at $\sim$5 $R_S$ - it is thus the ideal frequency to observe the shape of accretion flows or jets. Previous observations at 3mm put clear constraints on the intrinsic size of the major axis of the emission but had limited success in measuring source shape and position angle. Using the VLBA in conjunction with the LMT and the GBT we propose high-sensitivity observations to retrieve the shape and position angle of Sgr A* with unprecedented accuracy at 3mm using closure quantities. The data will be compared to various numerical GRMHD simulations of disks and jets. Moreover, we expect to detect the magnetar close to the galactic center and aim to use it as phase reference for astrometry and core-shift measurements. The latter enables verification or rejection of jet models for Sgr A*.

Investigators

Name	Institution
GBT Operator	Green Bank Observatory
Adam Deller	Swinburne University of Technology
Ciriaco Goddi	Center for Astrophysics | Harvard & Smithsonian; European Southern Observatory; Joint Institute for Very Long Baseline Interferometry European Research Infrastructure Consortium; Nijmegen, Radboud Universiteit
Raquel Fraga-Encinas	Nijmegen, Radboud Universiteit
Remo Tilanus	Arizona, University of
Michael Kramer	Manchester, University of; Max-Planck-Institut für Radioastronomie
Heino Falcke *	Netherlands Institute for Radio Astronomy; Nijmegen, Radboud Universiteit
Monika Moscibrodzka	Nijmegen, Radboud Universiteit
Jonathan Len-Tavares	Astrofísica, Óptica y Electrónica, Instituto Nacional de
Grant Wilson	Massachusetts at Amherst, University of
Alfredo Montana	Astrofísica, Óptica y Electrónica, Instituto Nacional de
David Sanchez-Arguelles	Astrofísica, Óptica y Electrónica, Instituto Nacional de
Tony Zensus	National Radio Astronomy Observatory; Max-Planck-Institut für Radioastronomie
David Hughes	Astrofísica, Óptica y Electrónica, Instituto Nacional de
Laurent Loinard	México, Universidad Nacional Autónoma de
Christiaan Brinkerink	Nijmegen, Radboud Universiteit
Thomas Krichbaum	Max-Planck-Institut für Radioastronomie
vlbiobs vlbiobs	National Radio Astronomy Observatory
vlbaops vlbaops	National Radio Astronomy Observatory
Geoffrey Bower	Academia Sinica

* indicates the PI