Scientists have developed a technique to use quasars – powerful sources driven by supermassive black holes at the centre of galaxies – to study the Universe’s history and composition. To demonstrate the new method, based on a relation between a quasar’s luminosity at X-ray and ultraviolet wavelengths, they made extensive use of data from XMM-Newton X-ray observatory of the European Space Agency (ESA). This approach promises to become an important tool to constrain the properties of our Universe.
Quasars allow scientists to study gravity in the field of the supermassive black holes. In addition, comparing the properties of quasars with those of other galaxies that host either active or passive black holes can reveal interesting aspects about the evolution of galaxies over cosmic history.
But one other aspect piqued the interest of two scientists from the Arcetri Astrophysical Observatory in Firenze, Italy: they realised that quasars can be used as probes of the expansion history of the Universe. The results of their study are presented in a paper, published in the Astrophysical Journal.
“The history of cosmic expansion holds a wealth of information about the Universe, including its age and the relative abundance of its components, and to pin it down we need to observe astronomical sources at a wide range of distances from us”, explains Guido Risaliti, one of the scientists who led the study.
“But determining distances in the Universe is not at all trivial and can be best performed only with a few classes of sources. In this study, we show how it can be done with quasars”, he added.
Read their study here.