Neils Bohr Institute | University of Copenhagen | 2016 Nov 28
[img3="A visualization of the stellar distribution in simulated ultra-diffuse galaxies. The galaxies are just as faint as dwarf galaxies, but are distributed over an area just as large as the Milky Way. New research shows that if there are a lot of supernovae during the star formation process, it can result in the stars and the dark matter in the galaxy to be pushed outwards, causing the extent of the galaxy to expand. The fact that the galaxy is spread over a larger area means that it becomes more diffuse and hard to observe with telescopes. The picture shows two simulated Ultra-Diffuse galaxies, over imposed on a Hubble Space Telescope image of background galaxies. (Credit: Arianna Di Cintio, Chris Brook, NIHAO simulations and Hubble Space Telescope)"]http://www.nbi.ku.dk/Nyheder/nyheder_16 ... er1280.jpg[/img3][hr][/hr]Over the last year, researchers have observed some very faint, diffuse galaxies. The galaxies are as faint as dwarf galaxies, but are distributed over an area just as large as the Milky Way. It has been a mystery, how galaxies so faint - containing up to 1000 times fewer stars than the Milky Way could still be just as large. Now new research from the Niels Bohr Institute shows that if a lot of supernovae explode during the star formation process, it can result in both the stars and the dark matter being pushed outwards, causing the galaxy to expand. ...
Galaxies are gigantic collections of stars, gas and so-called dark matter. The smallest galaxies contain a few million stars, while the largest may contain several hundred billion stars. The first stars already emerged in the very early universe about 200 million years after the Big Bang, formed from the gases hydrogen and helium. These giant clouds of gas and dust contract and eventually the gas is so compact that that the pressure heats up the material, creating glowing balls of gas and new stars are born. The stars are collected into galaxies, the first of which were baby galaxies of a sort.
The theory of the astronomers is that the baby galaxies gradually grew larger and more massive by constantly forming new stars and by colliding with neighbouring galaxies to form new, larger galaxies. The largest galaxies in our current universe have thus been under constant formation throughout the history of the universe. Earth and our solar system are located in a large galaxy, the Milky Way.
But the newly discovered, ultra-diffuse faint galaxies were difficult to classify and while some researchers thought that diffuse galaxies were just large spiral galaxies with a large amount of dark matter, others thought that it was a case of ordinary dwarf galaxies. ...
NIHAO XI: Formation of Ultra-Diffuse Galaxies by Outflows - Arianna Di Cintio et al
- Monthly Notices of the RAS (online 2016 Oct 13) DOI: 10.1093/mnrasl/slw210
arXiv.org > astro-ph > arXiv:1608.01327 > 03 Aug 2016 (v1), 22 Nov 2016 (v2)