An article published in the journal “Astrophysical Journal Letters” reports the discovery of the brightest quasar in the early universe. A team of researchers used observations of the Hubble Space Telescope and some ground-based telescopes to identify the galaxy cataloged as J043947.08+163415.7 at a distance of about 12.8 billion light years from the Earth. The supermassive black hole at its center is surrounded by a lot of materials that emit the huge amount of light that allows it to be identified even at that enormous distance, but only thanks to a gravitational lensing effect. That activity dates back almost a billion years after the Big Bang.
The powerful gravity force of galaxies can bend the light that passes close to it, as predicted by Albert Einstein’s Theory of General Relativity, and act as a lens. This effect can be used by astronomers to obtain more detailed images of galaxies behind the ones that act as gravitational lenses, which in some cases wouldn’t even be detectable. This happened in the case of the galaxy J043947.08+163415.7, whose image was magnified about 50 times by a gravitational lensing effect generated by a closer galaxy.
Astronomers have been searching for early galaxies of that kind for several years, hoping to catch even from billions of light years the light coming from quasars, galactic nuclei in which a supermassive black hole is very active due to large amounts of materials that orbit it and are heated up to the point of generating very strong electromagnetic emissions. Quasars are extremely bright and yet at certain distances they’re visible only thanks to gravitational lenses and therefore thanks to a lucky alignment as in the case of the galaxy J043947.08+163415.7, also called just J0439+1634.
The team led by Xiaohui Fan of the University of Arizona in Tucson selected a quasar candidate that later turned out to be the galaxy J043947.08+163415.7 from the images captured by various telescopes such as the Hubble Space Telescope, the Pan-STARRS1, the United Kingdom Infra-Red Telescope Hemisphere Survey Survey and NASA’s WISE Space Telescope. They showed the distorted traces of that quasar, which has a brightness estimated at 500-600 trillion times the Sun’s, at various electromagnetic frequencies.
The emissions of the quasars J043947.08+163415.7 helped the follow-up observations, conducted with the Multi-Mirror Telescope (MMT) and then with the Gemini North and Keck telescopes. Gemini detected the chemical signature of magnesium, which is important to identify with certainty a galaxy 12.8 billion light years away. The Earth’s atmosphere is a disturbing factor for such delicate observations and the adaptive optics of the Large Binocular Telescope (LBT) were very useful to obtain precise data, but the Hubble Space Telescope still contributed to confirm the nature of the quasar magnified by a gravitational lens.
The top image (NASA, ESA, and X. Fan (University of Arizona)) shows the quasar J043947.08+163415.7 seen by the Hubble space telescope in red with the galaxy used as a gravitational lens in blue. The bottom image (Feige Wang (UCSB), Xiaohui Fan (University of Arizona)) shows how the visible and infrared frequencies appear on the MMT, Keck, Gemini and LBT telescopes.
This research was based on information collected with different instruments that provided detections at different electromagnetic frequencies but it’s not finished. The astronomers intend to continue its observations with the ALMA radio telescope, an excellent instrument to study distant quasars, and other telescopes, possibly even with the James Webb space telescope when it gets launched, at last.
