📰 A completely isolated dwarf galaxy exposed to an exciting loss of gas


WLM galaxy. Yang et al

Isolated dwarf galaxies appear to be remnants of the early universe and are not meant to interact with their environment. Observing one of them, an international team led by scientists from CNRS (The National Center for Scientific Research, better known by its acronym CNRS, is the largest…) and offParis Observatory (The Paris Observatory was born from the project, in 1667, to create an astronomical observatory…) – PSL found it strong interaction (An interaction is an exchange of information, affect or energy between two agents within…) with the intergalactic medium, whereas the latter is assumed to be very sparse. Do itobject (In general, the word object (from the Latin objectum, 1361) denotes an entity defined in…) of a letter published in the journal Astronomy and Astrophysics, April 27, 2022, this discovery disrupts the understanding of the formation and evolution of dwarf galaxies and opens a new field (A field corresponds to a concept of defined space:) of questions.

Dwarf galaxies are affected by the same evolutionary processes that operate in large galaxies such as The Milky Way (The Milky Way (also called “our galaxy”, or sometimes…) or that galaxy (Galaxies is a French quarterly about science fiction. With…) of Andromeda. Less luminous and less massive than their big sisters, they are particularly sensitive to the environmental mechanisms caused by the presence of a galaxy (In cosmology, a galaxy is a collection of stars, gas, dust and…) giantess (A giant star is a star of luminosity class II or III. I…) in their quarter (The concept of neighborhood corresponds to an axiomatic approach similar to …). In this case, they may be exposed to the effects of gravitational tides or pressure (Pressure is a basic physical notion. You can think of it as a reported force…) dynamic (The word dynamic is often used to denote or qualify that which relates to movement. It…) caused by the surrounding gaseous medium. To determine the significance of these effects, astronomers can compare the differences between the populations of dwarf galaxies: on the one hand those called “satellites” and on the other hand those called “isolated”.

WLM is considered the archetype of a dwarf galaxy (A dwarf galaxy is a small galaxy consisting of on the order of 10 billion stars, a number…) isolated. It was discovered in 1909 by Max Wolf (Maximilian Franz Joseph Cornelius Wolf (21 June 1863 – 3 October 1932…), then confirmed by Knut Lundmark and Philibert Melotte (hence the name “WLM” after the initials of its co-discoverers). It is equidistant between the Milky Way and M31, almost 3 million light years away. She would have formed in isolation Total (Total is the quality of complete, without exception. From an accounting point of view, a…)without external disturbances. Thus his lot (The term mass is used to denote two quantities linked to a…) of fabric (Matter is the substance that makes up any body that has a tangible reality. Its…) dark is considered to be stable and determined, up to 90 times more massive than its baryonic matter, composed of stars and gas (A gas is a set of atoms or molecules very weakly bound and…).

Newer though comments (Observation is the act of attentively following phenomena, without the will to see them…) completed at radio telescope (A radio telescope is a specific telescope used in radio astronomy to…) MeerKAT by an international team led by a engineer (“The engineer’s basic job is to solve natural problems…) CNRS at the Observatory of Paris (Paris is a French city, capital of France and capital of the region…) – PSL revealed a strong interaction between the WLM and the intergalactic medium. L’hydrogen (Hydrogen is a chemical element with symbol H and atomic number 1.) The galaxy’s neutral repulsion is repelled by a dynamic pressure effect caused by its own motion through the intergalactic medium.

Indeed, from the deepest radio observations, scientists have identified in the WLM four gaseous clouds of neutral hydrogen that extend in the opposite direction of its motion in sky (The sky is Earth’s atmosphere as seen from the planet’s ground.)determined by data (In information technology (IT), data is an elementary description, often…) latest from Gaia satellite (The Gaia satellite is an astrometric mission of the European Space Agency (ESA) in front of…) by ESA.

“The four clouds represent 10% of the galaxy’s total neutral hydrogen mass. We also found that there is a spatial delay between the gas and the WLM stars,” explains Roger Ianjamasimanana, radio astronomer atUniversity (A university is an institution of higher education whose aim is…) Rhodes (Rhodes (in ancient Greek Ῥόδος / Rhodes, modern…)in Africa (With an area of ​​30,221,532 km2 including the islands,…) from South (South is a cardinal point, opposite north.). With the discovery of these four gaseous paths, the team of research (Scientific research initially refers to all measures undertaken with a view to…) conclude that the WLM gas is ejected from it due to the dynamic pressure exerted by the surrounding gaseous medium.


Composite image, in the optical and radio (To delete), of the WLM, an isolated dwarf galaxy, equidistant from the Milky Way and the Andromeda Galaxy. Observations by the MeerKAT radio telescope reveal four gaseous tracks of neutral hydrogen (blue transparent) in its wake move (In geometry, a displacement is an equality that preserves distances and angles…) (represented by the orange arrow): an oddity for this object, which is not thought to interact with the intergalactic medium surrounding it. Yang et al. / Paris Observatory – PSL / CNRS / ESO / NOAO / MeerKAT

This discovery is a complete surprise to the scientists: “The intergalactic medium in which the WLM resides is supposed to be almost empty (Void is usually defined as the absence of matter in a spatial region.), composed of a thin layer of gas. Until now, scientists assumed that such a thin medium could not cause such an effect on a galaxy,” explains Yanbin Yang, CNRS engineer at the Paris Observatory – PSL, and first author of the paper.

To study the effect in more detail, the team performed computer simulations. “In our simulations, we also found that the observations can only be explained if the intergalactic medium turns out to be much denser than expected. It appears that we have found a very large, unexpected reservoir of matter in regions that is among the least dense ofUniverse (The universe is the sum of everything that exists and the laws that govern it.)“, adds scientific (A scientist is a person who is dedicated to the study of a science or sciences and who…).

Another hypothesis would be that the mass of the WLM would be much lower and could even be devoid of dark matter. This would explain how the intergalactic medium, so weak density (The density or relative density of a body is the ratio between its density and…), may strip WLM by dynamic pressure. But it would also be a ground-breaking result, because so far it is believed that the mass of galaxies is dominated by this mysterious dark matter.

In summary, the team concludes two scenarios: either these nearly “empty” intergalactic regions are not really empty, or the WLM galaxy is deficient in dark matter.

In any case, this study revolutionizes the understanding of dwarf galaxies. In the future, for future (Futurs is a science fiction collection from Éditions de l’Aurore.) work, they can never again be considered completely isolated.

Also read the information on the same subject:
– on the website of the Max Plack Institute for Radioastronomy
– on the Rhodes University website

Reference:
The paper ‘Evidence of ram pressure stripping of the WLM, a dwarf galaxy far from any large host galaxy’ by Yanbin Yang et al. (2022) is published in a letter from the journal Astronomy & Astrophysics, 27 April 2022. DOI: https://www.aanda.org/10.1051/0004-6361/202243307

International cooperation:
The international team includes researchers from Observatoire de Paris – PSL and CNRS, as well as the Instituto de Astrofisica de Andalucia (Spain), Rhodes University (South Africa), University of Cape Town (The Town class of British light cruisers were produced just before and…) (South Africa), Victoria University (Canada),University of Montreal (The University of Montreal is one of four educational institutions…) (Canada), Ouaga University (Burkina Faso), Max-Planck-Institut für Radio astronomy (Radio astronomy is a branch of astronomy that deals with the observation of the sky in…) (Germany) and NRC Herzberg Astronomy and Astrophysics (Canada).

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