Astronomers are spying on the Milky Way’s neighbors, assessing the amount of light escaping from them and how this is connected to the physical properties of each galaxy.
This deep investigation of our local universe could help scientists better understand the first distant galaxies currently observed by the James Webb Space Telescope (JWST) and the Hubble Space Telescope.
Because the galaxies in the primitive universe are incredibly faint and therefore difficult to observe, a team of astronomers led by Jens Melinder of Stockholm University in Sweden set out to create a reference sample of galaxies in the neighborhood of our own. Milky Way.
Related: Galaxies: collisions, types and how they form
In particular, Melinder and his colleagues collected and collated data on a special wavelength of ultraviolet radiation from these local galaxies known as alpha Lyman light.
Lyman Alpha Light it is found in the light of the gas that surrounds the hottest stars, which means that it is found in particular in star-forming galaxies. The peak period of star formation in the universe occurred about 10 billion years ago, so Lyman’s alpha light is a great way to study galaxies that existed when the universe was only about four billion years old. (He big Bang that created our universe occurred about 13.8 billion years ago).
But decoding the information carried by this light can be difficult, since the path that leads to instruments like hubble and the JWST is complex.
Lyman alpha light takes the scenic route around the cosmos
The exact wavelength of alpha Lyman light and the direction from which it travels are factors influenced by the physical processes it encounters as it leaves its source. galaxy. The regions of these galaxies with different physical conditions through which Lyman alpha light travels can change the path of the individual photons that make up the light, change its wavelength, and even absorb a fraction of the light.
The fact that alpha Lyman light can find hot regions, dusty areas or sectors with clouds of strongly flowing gas in its home galaxy and during its journey means that, when it reaches us, the information it carries can be difficult to detect. interpret.
However, if an accurate interpretation of this light is possible after its complicated journey, it may reveal substantial amounts of information about the physical properties of the galaxies from which it originates.
To better understand these emissions and build their Lyman Alpha Reference Sample (LARS), the team selected 45 local galaxies that have extensive star formation and observed them across the entire electromagnetic spectrum. This allowed the team to deduce how much Lyman alpha light escapes from each galaxy and how this fraction correlates with the physical properties of that galaxy.
One of the most important findings reached by astronomers is the connection between the amount of gas, plasma (which is a superhot electrically charged gas), and dust envelopes surrounding the galaxies they studied and the amount of alpha Lyman light escaping from they.
“There is a clear correlation between the amount of cosmic dust a galaxy has and the amount of Lyman it lets out.” Melinder said in a statement. “This was to be expected, because dust absorbs light, but we have now quantified the effect.”
The scientists were also able to determine how this gas is distributed in galaxies and how it moves through them.
The team discovered a connection between the total mass of the stars in a galaxy with the amount of alpha Lyman light that can escape, although this connection is less clear than the link between gas and the escape of this light.
However, what does not appear to be related to the escape of alpha Lyman light in galaxies is the rate at which those galaxies are forming new stars.
Related: The early universe was packed with stars 10,000 times the size of our sun, a new study suggests
Lyman’s alpha light ‘shrinks’ galaxies
One thing the team found that could be particularly significant is the fact that when observed at other wavelengths of light, these galaxies suddenly appear considerably larger. This is an effect astronomers have seen before.
“We see the same effect in computer simulations of galaxies with calculations of how Lyman alpha travels through gaseous clouds in interstellar space,” team member Peter Laursen, a researcher at the Cosmic Dawn Center in Denmark, said in the same statement. “This confirms that we have a pretty good theoretical understanding of the physics at play.”
It is important to take this effect into account when observing early and distant galaxies, because the light from their surroundings may be too faint to detect or may fall beyond the limits of the detectors observing them. That means that examining and quantifying this effect as seen in LARS could help astronomers to better explain it, and therefore more precisely determine the size of the first galaxies.
“These results will help interpret observations of very distant but similar galaxies observed with the Hubble and James Webb Space Telescopes,” Melinder concluded. “Understanding the detailed astrophysics of this type of galaxy is crucial to developing theories about how the first galaxies formed and evolved.”
The team’s research was published earlier this month in the Astrophysical Journal Supplement Series.
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