Quasars are among the brightest objects in our sky. At first glance, they look like stars. Hence their name, moreover, which corresponds to a contraction of “quasi-stellar radio Source”. But that’s not the case. THE astronomersastronomers discovered that behind quasars there are actually luminous cores of distant galaxies hidden. Cores powered by supermassive black holes that appear insatiable. Real cosmic monsters. As a result, quasars tend to literally eclipse the rest of the galaxy that shelters them. Like a projectorprojector would eclipse a field of firefliesfireflies.
“A quasar outperforms its host galaxy by several orders of magnitude. And the previous images weren’t sharp enough to make out what the host galaxy looks like with all its stars.”confirms Minghao Yue, researcher at Massachusetts Institute of Technology (MIT, United States), in a press release. But thanks to sensitivity and resolutionresolution exceptional results from the James Webb Space Telescope (JWST), things have changed. In L’Astrophysical Journal, MIT astronomers report how they studied six ancient quasars – their age is estimated at 13 billion years – for several months. And accumulate more than 120 hours of observations. To finally observe for the first time, the lightlight emitted by the stars of the host galaxies of three of these quasars.
Draw the host galaxy behind the quasar
To achieve their goals, the researchers collected images of the six quasars in different wavelengthswavelengths. Then they integrated them into a model defining the amount of light likely coming from a compact “point Source”, such as a accretion diskaccretion disk center of a black hole, compared to a more diffuse Source, such as light from the surrounding scattered stars of the host galaxy.
This modelizationmodelization allowed astronomers, thanks to the finesse of the initial images sent back by the James-Webb space telescope, to separate the light of three quasars into two components: the light coming from the disk of the central black hole and the light of the more diffuse stars of its host galaxy. As the amount of light coming from these two sources reflects their massmass total, the researchers were able to estimate the mass of the galaxies in question in relation to that of their supermassive black holesupermassive black hole central. A ratio of around one in ten. Even though the mass balancemass balance current is more of the order of one in a thousand. Understand that more recently formed black holes are much less massive than their host galaxies.
Very massive black holes compared to their host galaxy
As the question arises about the chicken and its egg, researchers have long wondered whether supermassive black holessupermassive black holes grow first, leaving galaxies to catch up later or whether galaxies and their stars grow first, regulating the growth of black holes.
“The first black holes of our UniverseUniverse appear to be growing faster than their host galaxy”, explains Anna-Christina Eilers, physicist at MIT. But how can these black holes, which turn out to be billions of times more massive than ours? sunsun could they have become so big so quickly, at a time when our Universe was still in its infancy? Astronomers today interpret their latest results as a “provisional proof” that some sort of initial seeds of black holes could have been more massive at that time. Enough to allow black holes to acquire their mass earlier than their host galaxy during the first billion years of our Universe.
