GMVA24B-054
Precision astrometry of Sgr A* with 3mm VLBI observations of SiO stellar masers
Abstract
The Galactic center contains a massive black hole, Sgr A*, and is also the densest stellar environment in the Galaxy. Evolved stars that harbor SiO masers in their circumstellar shells offer unique options for very precise astrometric measurements, aligning the spectacular IR stellar motion studies and event horizon radio imaging. So far, most of these approaches have used connected element interferometry, but orders of magnitude improvements are in principle possible with millimeter VLBI. With the new option of phased ALMA participating in spectral line observations, we propose a pilot experiment to do VLBI phase referencing between the GCIRS7 SiO maser and Sgr A* at 86 GHz. This will facilitate a refined alignment of the IR and radio frames, which in turn will enable improved measurements of our Galaxy's rotation curve as well as more stringent tests of General Relativity. Furthermore, astrometric measurements of hot-spot motions can be made and the position of IR polarization loops relative to the black hole shadow can be inferred with planned upgrades of the EHT and VLTI-GRAVITY instruments. In the future we could also map angular broadening on lines of sight offset from SgrA* to maser-bearing evolved stars in the nuclear star cluster.
Investigators
| Name | Institution |
|---|---|
| Arturo Gomez-Ruiz | Astrofísica, Óptica y Electrónica, Instituto Nacional de |
| Geoffrey Crew | Massachusetts Institute of Technology |
| Lynn Matthews | Haystack Observatory; Center for Astrophysics | Harvard & Smithsonian |
| Eduardo Ros | Max-Planck-Institut für Radioastronomie; València, Universitat de |
| Ciriaco Goddi | Center for Astrophysics | Harvard & Smithsonian; European Southern Observatory; Joint Institute for Very Long Baseline Interferometry European Research Infrastructure Consortium; Nijmegen, Radboud Universiteit |
| Sebastiano von Fellenberg | Max-Planck-Institut für Radioastronomie |
| Huib van Langevelde | Joint Institute for Very Long Baseline Interferometry European Research Infrastructure Consortium; Leiden, University of |
| Kazi Rygl | Istituto Nazionale di Astrofisica |
| Michael Janssen * | Max-Planck-Institut für Radioastronomie; Nijmegen, Radboud Universiteit |
| GBT Operator | Green Bank Observatory |
* indicates the PI