Sailing 1.5 million kilometers from Earth, revolving around the shadow of our planet and its great mirror riveted towards the depths of the cosmos, the James Webb Space Telescope (JWST) continues to see what had never been seen before. never been seen before.
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According to the standard cosmological model Lambda CDM, commonly accepted by astrophysicists, galaxies are originally formed in wells – or halos – of dark matter (or CDM for Cold Dark Matter). It is this which “traps” and gravitationally collects the gas of so-called ordinary matter. Around 20% of this gas then concentrates, and thereby increasing in temperature, effectively “lights up” into stars. So much for the classic scenario…
A trio of galaxies far too hungry for gas
Yes, but… The infrared “eye” of NASA and ESA's JWST telescope has detected certain galaxies whose properties show that it may not be exactly that way. In many ways, the enigma of “little red dot” galaxies, which we talked about several weeks ago, is reminiscent of the one presented here.
Indeed, the three galaxies identified by astronomers are far too massive and, above all, have too large a proportion of stars in relation to their quantity of gas! Here, they converted half of them (ordinary matter baryons) into suns, which is really a lot, two to three times what is expected for such galaxies…
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These results redefine our understanding of galaxy formation in the young Universe
The James-Webb infrared telescope sees so far – therefore into the past of the cosmos – and so easily pierces the large clouds of dust which surround the primitive galaxies that it allows us to observe and analyze things which completely escaped our understanding before. him.
Infrared is a wave in the electromagnetic spectrum, like visible light, but which has the property of passing through dust clouds. On one of the telescope's infrared cameras, the NIRCam, is attached a spectrograph, called NIRCam/Grism, which makes it possible to very finely measure the distances and stellar masses involved. It is also this famous dust that the infrared passes through , which give their red color to these very distant galaxies. It is precisely this instrument that was used to analyze our trio of overly massive and “starry” galaxies in their tender youth.
According to David Elbaz, research director at CEA Paris-Saclay, “the massive properties of these 'red monsters' had hardly been determined before JWST, because they are optically invisible due to dust attenuation”.
For Menguyen Xiao, lead author of the study presented in Naturethis discovery pushes us to a redefinition of the formation and evolution of the first galaxies. They do not invalidate the standard cosmological model, but rather point towards understanding why “These galaxies form stars with unexpected efficiency. We need to study these conditions of the early Universe more deeply”.
In summary, these three galaxies form “too many” stars compared to what we understand about their supposed growth. They are very massive too early in the Universe, and in certain aspects quite similar to the “small red dot galaxies” mentioned above. They also recall that the James-Webb telescope had recently made it possible to discover a primitive galaxy with stars that were much too hot compared to established models.
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