???? Detection of quasar host galaxies in the early Universe

2023-07-01 04:00:09

New images taken by the James Webb Space Telescope (JWST) have revealed, for the first time, light from two massive galaxies harboring actively growing black holes – quasars – observed less than a billion years after the Big Bang. Image of the host galaxy after substraction from light of quasar. Image of JWST NIRCam 3.6 μm from HSC J2236+0032
© Ding, Onoue, Silverman et al.

An international team, including CNRS-INSU scientists (see box), reveals that black holes have a mass close to one billion times that of Soleil, and that the mass of the host galaxies is almost a thousand times greater. This ratio between the mass of the black hole and that of the galaxy host is similar to that of nearby galaxies, suggesting that the relationship between black holes and their hosts was already in place 800 million years after the Big Bang.

Quasars are bright, while the galaxies that host them are dim, which made it difficult to detect the galaxy’s dim light in the quasar’s glare, especially at great distances. Before the JWST, the télescope spatial Hubble was able to detect host galaxies of bright quasars when theUniverse was just under 3 billion years old, but no more.

The JWST’s superb sensitivity and ultra-sharp images in infrared wavelengths finally allowed researchers to push these studies to the time when quasars and galaxies first formed. Some month only after the regular commissioning of the JWST, the team observed two quasars, HSC J2236+0032 and HSC J2255+0251, at offsets rouge of 6.40 and 6.34.

The zoomed-out image, the quasar image, and the image of the host galaxy after subtracting the light from the quasar (from left to right). The scale of the image in light years is indicated in each panel.
Image of JWST NIRCam 3.6 μm from HSC J2236+0032
© Ding, Onoue, Silverman et al.