This chart shows the spectrum of the ultra-luminous infrared galaxy UGC05101, obtained by the Near- and Mid-Infrared Camera (IRC) onboard AKARI. It indicates the presence of dust, molecules such as water ice and carbon monoxide, atoms and ions (charged particles).
UGC05101 is situated in the constellation Ursa Major, approximately 550 million light years away from the Earth. Termed an ‘ultraluminous infrared galaxy,’ the total energy it emits in the infrared alone is about one trillion times more than that of the Sun. However, the central region is covered by a thick interstellar medium and can only be observed in the infrared. Observations with AKARI have revealed evidence for active phenomena in the central part of this galaxy.
The feature seen around 4.5–5 micrometres is caused by absorption by carbon monoxide (CO) molecules in the gas phase. It is very broad, indicating that the temperature of this molecular gas is over 500 degrees Centigrade. It has been postulated that at the centre of UGC05101 is a giant black hole, of mass more than a million times that of our Sun. In this case, the material around it would be expected to radiate enormous amounts of energy as it slowly tumbles into the black hole. It is suspected that the detected molecular gas is heated by radiation from near the black hole.