Max Planck Institute for Radio Astronomy | 2019 Jan 21
ALMA and the Global mm-VLBI Array team up and provide first scientific results
Including the powerful ALMA into an array of telescopes for the first time, astronomers have found that the emission from the supermassive black hole Sagittarius A* (Sgr A*) at the center of our Galaxy comes from a smaller region than previously thought. This may indicate that a radio jet from Sgr A* is pointed almost directly towards the Earth. ...
So far, a foggy cloud of hot gas has prevented astronomers from making sharp images of the supermassive black hole Sgr A* and causing doubt on its true nature. They have now included for the first time the powerful ALMA telescope in northern Chile into a global network of radio telescopes to peer through this fog, but the source keeps surprising them: its emission region is so small that the source may actually have to point directly at the direction of the Earth.
Observing at a frequency of 86 GHz with the technique of Very Long Baseline Interferometry (VLBI), which combines many telescopes to form a virtual telescope the size of the Earth, the team succeeded in mapping out the exact properties of the light scattering blocking our view of Sgr A*. The removal of most of the scattering effects has produced a first image of the surroundings of the black hole.
The high quality of the unscattered image has allowed the team to constrain theoretical models for the gas around Sgr A*. The bulk of the radio emission is coming from a mere 300 milllionth of a degree, and the source has a symmetrical morphology. ...
The Size, Shape, and Scattering of Sagittarius A* at 86 GHz: First VLBI with ALMA ~ S. Issaoun et al
- Astrophysical Journal 871(1):30 (20 Jan 2019) DOI: 10.3847/1538-4357/aaf732
arXiv.org > astro-ph > arXiv:1901.06226 > 18 Jan 2019