A spiral galaxy swarms its nurseries of stars
A new image from the Hubble Space Telescope sheds light on the conditions under which a galaxy even stripped of its gas manages to form stars.
Although the intense blue of its disk contrasts with the black of the sky, it is not really what interests astronomers in this galaxy. It is rather these small grains, also blue, that it seems to leave behind...
In the constellation of the Whale, JO201 belongs to the category of “jellyfish galaxies”. These are galaxies with a tail, in the form of garlands of star nurseries — or “tentacles” — that extend behind them for tens or even hundreds of thousands of light-years.
JW100, another jellyfish galaxy pointed to by Hubble.
Gullieuxzic et al. (2023)The origin of this pattern is partly known. Jellyfish galaxies are actually galaxies subjected to an intense and very hot intergalactic wind. This strips them of their molecular gas, like the breath of a child stripping a dandelion flower. The effect only affects fast-moving galaxies, in the heart of clusters, where the intergalactic gas is particularly hot.
?The origin of globular clusters
Surprisingly, as evidenced by these two images taken using the Hubble Space Telescope by Marco Gulleiuszic (Padua Observatory) and his colleagues, the molecular gas torn from the jellyfish galaxies still manages to form stars. Observing these nurseries makes it possible to study the birth of stars under unusual conditions, in total immersion in hot intergalactic gas rather than sheltered in a galactic disc, their usual cradle. In other words, it helps to understand the conditions under which stars form or, on the contrary, can no longer form.
Some astrophysicists believe that some of the globular clusters and dwarf galaxies seen in nearby galaxy clusters were formed by this mechanism. It's possible, because we know that jellyfish galaxies can produce 100,000 to 100,000,000 solar masses in their wake!
Except that it is not certain that the stars of these clusters remain gravitationally linked. If they are not, they will disperse into the intergalactic medium.
To find out, it is necessary to be able to measure and weigh precisely each of these lumps where clusters of stars are formed. And therefore use a very sensitive and very precise telescope, like Hubble. These images are taken from a program intended to study in detail six jellyfish galaxies using the space telescope, from ultraviolet to infrared.
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