Some quasar host galaxies live in the early universe. This makes them especially interesting, since they had to have accumulated a lot of mass very quickly. Luckily for us, radio telescopes like ALMA can peer back in time and tell us more about these galaxies and their environments.
Finding Far-Off Quasars
Antennas of the ALMA observatory under the Magellanic Clouds. [ESO/C. Malin]Quasars are absurdly energetic objects. They are a version of the supermassive black holes at the centers of galaxies, and what makes them unique is the large amounts of energy they emit while actively accreting material. A significant portion of this energy is emitted as short-wavelength ultraviolet (UV) light, which is the key to studying quasars that live in the early universe.
The farther away an object is, the more its light becomes redshifted as it travels to us — that is, the wavelength at which light from the object was first emitted is shorter than the wavelength we observe when that light reaches us. So in the case of far-off quasars, their UV emission will be redshifted into radio wavelengths, where we can still observe it!
FIR (left) and [C II] (right) emission maps (distances shown in arcseconds) ...