Studying dwarf galaxies to get the big picture

A surprising degree of variation in the mechanisms by which their stars were formed.

Calalog of the studied dwarf galaxies' haloes. © 2018 EPFL/LASTRO
Calalog of the studied dwarf galaxies' haloes. © 2018 EPFL/LASTRO

Dwarf galaxies don’t emit much light and are therefore hard to observe, but they have a lot to teach us about how the universe was created. EPFL researchers have finished the fussy task of investigating 27 predominate cosmic systems in detail, recognizing the conditions under which they were shaped and how they’ve since advanced. These small-scale galaxies are ideal for concentrate the components of new star development and the initial phases in the formation of the universe.

A team of scientists from EPFL’s Laboratory of Astrophysics (LASTRO) studied 27 such dwarf galaxies and found a surprising degree of variation in the mechanisms by which their stars were formed. While they might be called “dwarves,” they are in truth gigantic and can weigh anyplace between many thousands and a few million-fold the amount of as the sun. They are additionally the cosmic systems with the dimmest issue.

Thus, scientists developed highly sophisticated computer models to examine these galaxies’ properties, size, and temporality – all of which go well beyond our basic understanding. The models take into account each of the galaxies’ components – gases, stars and dark matter – as well as the relationship between dark matter and visible matter. They also factor in the conditions under which matter was shaped when the universe was first made somewhere in the range of 14 billion years back – conditions that are presently known on account of late space missions completed to find the marks of the Big Bang.

To examine the dwarf galaxies, the researchers initially made each model and went stride by advance through the systems’ key attributes like how much gas (predominantly hydrogen) they contain, the warming and cooling of their interstellar mediums, their pressure and extension forms, the progressive ages of their stars, those stars’ supernovae, and the subsequent arrival of a variety of chemicals.

The researchers at that point contrasted the aftereffects of their models and information that had been gotten by watching diminutive person systems – all the more particularly, those circling our cosmic system, the Milky Way, and its neighboring world, Andromeda (M31) – utilizing eight-meter optical telescopes, the greatest that are right now out there. These diminutive person cosmic systems frame some portion of what is known as the Local Group and are sufficiently close for astrophysicists to have the capacity to get precise data on the ages and compound segments of individual stars.

Ensuring that the models’ outcomes coordinate exact information is basic if the researchers need to utilize them to test their speculations about the dull issue, the sorts of articles in charge of the reionization of the universe, and the conditions and eras for new star arrangement.

This is the first occasion when that midget universes have been inspected in such detail and under cosmologic conditions – that is, not by thinking about them as detached frameworks yet rather by considering every one of the collaborations among the main galactical systems.

Pascale Jablonka, a LASTRO researcher specialized in spectroscopy and galaxies’ chemical development said, “The advantage of dwarf galaxies is that they respond very well to even minor changes in conditions, making them excellent guinea pigs for studying galaxies in general. For instance, by analyzing the light that stars emit, she was able to determine their chemical composition and how long it took them to form.”

Yves Revaz, a galaxy dynamics expert at LASTRO said, “Our models enabled us to create a database of many different types of stellar activity and gave us valuable insight into the factors that can cause star formation to speed up, slow down or even stop altogether.”

Based on the data they collected – which include an impressive number of different star-formation mechanisms given how “small” dwarf galaxies are – the LASTRO team found that the specific mechanism used depends on the density of the galaxy’s dark and baryonic matter.

That density determines whether a galaxy will keep on making stars or suddenly stop. If a dwarf galaxy’s matter is too dispersed, then its hydrogen will get too hot and evaporate, meaning it can no longer form stars. If on the other hand, a dwarf galaxy has a dense halo of dark matter protecting it, then star formation will continue apace.

The results of their painstaking work were published in Astronomy & Astrophysics.