New observations from ESA’s Herschel Space Observatory using the U.K. led SPIRE instrument have pinned down what could be the the most luminous object in the local Universe.
The galaxy, known as IRAS 08572+3915, was previously observed by the Infrared Astronomical Satellite (IRAS) in 1983 at infrared (60-100 micrometres) wavelengths and was already known to be a peculiar object consisting of two galaxy nuclei in the process of merging together. However, the new observations have shown that it is much more luminous than previously thought.
The galaxy was recently observed by Herschel, as part of the HERUS programme at longer submillimetre wavelengths (200-700 microns) with the SPIRE photometer and spectrometer, allowing a much more accurate model of the galaxys’ spectrum to be constructed. The SPIRE data itself was analysed by Dr Chris Pearson at The Rutherford Appleton Laboratory. The new model for the galaxy was then constructed by Prof. Andreas Efstathiou of the European University, Cyprus who then published the teams’ results as a letter to the journal Monthly Notices of the Royal Astronomical Society.
The combined 3 colour Herschel SPIRE image of the galaxy IRAS 08572+3915 with the Hubble Space Telescope image shown as an inset.
IRAS 08572+3915 is thought to be powered by a colossal central black hole (known as an AGN – Active Galactic Nucleus) which violently heats an enormous surrounding dust torus (like a giant doughnut). The team calculated that this galaxy is about 5 times more luminous than what has been thought so far. This revision of its luminosity makes IRAS 08572+3915 the nearest hyperluminous infrared galaxy with luminosity of more than 10 trillion times that of the sun and the most luminous object within a radius of about 2 billion light years.
The SPIRE instrument was assembled and tested at the Rutherford Appleton Laboratory (RAL), in Oxfordshire. The RAL team were heavily involved in the operations and support of the SPIRE instrument, as well as helping other scientists get the best science out of it.
The HERUS programme is led by Dr Duncan Farrah of Virginia Tech. The work on IRAS 08572+3915 was made by an international team of astrophysicists, led by Prof. Andreas Efstathiou of European University Cyprus, with scientists from 18 universities and research centers around the world including Dr Chris Pearson and Dr Dimitra Rigopoulou of The Rutherford Appleton Laboratory / Oxford University / The Open University in collaboration with Imperial College London, Cornell University, Max-Planck Institute Germany, Heidelberg University, Virginia Tech, Sussex University, CEA-Saclay, University of Lisbon, Naval Research Laboratory, University of California-Irvine)
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