Large galaxies take molecular gas from their satellites Astronomy

A research team led by astronomers from the International Center for Radio Astronomy Research (ICRAR) studied the content of molecular gases in nearby massive galaxies in a cosmological simulation, focusing on how it depends on the galactic environment.

An artist’s impression showing the growing effect of ram-pressure removal when removing gas from the spiral galaxy NGC 4921 and its satellite galaxies. Image credit: ICRAR / NASA / ESA / Hubble Heritage Team / STScI / AURA.

“Our study provides new systematic evidence that small galaxies everywhere lose part of their molecular gas as they approach a larger galaxy and its hot gas halo,” said Dr. Adam Stevens, astrophysicist from ICRAR and the ARC Center of Excellence in All Celestial Astrophysics in 3 Dimensions (ASTRO 3D).

“Gas is the lifeblood of the galaxy. Continuing to acquire gas, galaxies grow and form stars. Without it, galaxies stagnate. “

“We have known for a long time that large galaxies remove atomic gas from the periphery of small galaxies. But so far it has not been tested with molecular gases with the same details. “

“Galaxies do not usually live in isolation. When a galaxy moves through a hot intergalactic medium or halo of a galaxy, part of the cold gas in the galaxy is removed. This process of rapid action is known as the removal of pressure in the ram “, said Dr. Barbara Catinella, also from ICRAR.

Using the cosmological, hydrodynamic simulation of the TNG100, astronomers made direct predictions of the amount of atomic and molecular gas to be observed by special research at the Arecibo Telescope in Puerto Rico and the IRAM 30 telescope in Spain.

They then took real observations from the telescope and compared them with their original predictions. The two were extremely close.

“The 30-meter IRAM telescope observed molecular gas in more than 500 galaxies,” said Dr. Catinella.

“These are the deepest observations and the largest sample of atomic and molecular gas in the local universe. Therefore, this was the best sample for this analysis. “

The finding fits in with previous evidence to suggest that satellite galaxies have lower star formation rates.

“The extracted gas initially goes into space around a larger galaxy,” said Dr. Stevens.

“It could end up raining on a larger galaxy, or it could just stay out of its environment.”

“But in most cases, a small galaxy is doomed to merge with a larger one anyway.”

“Often they survive only one to two billion years, and then they will eventually merge with the central one. So it affects how much gas they have as they connect, which will then affect the development of a large system as well. “

“Once galaxies get big enough, they start relying on getting more matter from the cannibalism of smaller galaxies.”

The study was published in Monthly notices of the Royal Astronomical Society.

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Adam RH Stevens and others. 2021. Molecular hydrogen in galaxies IllustrisTNG: a careful comparison of environmental signatures with local data on CO and SFR. MNRAS 502 (3): 3158-3178; doi: 10.1093 / mnras / staa3662

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