The cores of most galaxies are thought to harbour supermassive black holes, which power galactic nuclei by converting the gravitational energy of accreting matter into radiation. Sagittarius A* (Sgr A*), the compact source of radio, infrared and X-ray emission at the centre of the Milky Way, is the closest example of this phenomenon, with an estimated black… (More)
We report sensitive spectrum measurements from 70 to 1500 MHz of the radio interference (RFI) environment at locations in Westford, Massachusetts and Hancock, New Hampshire. These measurements show that below 400 MHz the interference in bands allocated to passive services is often limited by unintentional signals from power lines and part 15 devices.
Approximately 10% of active galactic nuclei exhibit relativistic jets, which are powered by the accretion of matter onto supermassive black holes. Although the measured width profiles of such jets on large scales agree with theories of magnetic collimation, the predicted structure on accretion disk scales at the jet launch point has not been detected. We… (More)