What makes a star like you in a place like this?


Figure: composite image of the Sextans-A galaxy, in which an image has been combined in the V-band optical range Local Group Survey and observations of Neutral Hydrogen from the Little Things Survey. The stars reported in this article have been marked with orange boxes. & Nbsp;

The Small Cloud of Magellan galaxy is the current reference for massive stars poor in metals. Now, researchers from the Center for Astrobiology are leading an international effort to establish the Sextans-A galaxy, with metallicity 5 times lower, as a new reference. In the framework of this project, very young and massive stars have been discovered in a totally unexpected area: its external part.

With ages less than 30 million years, massive stars are markers of star formation, so in astrophysics can be used to describe how and where stars are currently forming. On the other hand, metal-poor massive stars are key to understanding the processes of feedback occurring throughout the history of the Universe, such as the evolution of galaxies, the progenitors of gamma-ray bursts, supernovas luminous, gravitational waves, etc. Studying these stars therefore brings us closer to understanding the formation of the first stars of the Universe. & Nbsp;

A new study, carried out by a group of Spanish researchers and led by Miriam García, CAB researcher, reflects the discovery of very young and very massive stars on the outskirts of the Sextans-A galaxy. This finding "was quite unexpected because in the external parts the gas density is very low, and because the usual signs of star formation had not been detected in the area: intense UV emission and / or signs of ionized gas", says Miriam García.

The study, which has been published in Monthly Notices of the Royal Astronomical Society (MNRAS), also reflects that these stars would be isolated and not part of a cluster, in accordance with what would be expected according to one of the massive star formation mechanisms that are considered at present: the monolithic collapse. "The physics of the formation of massive stars is very complex, and the simulations are incapable of forming stars with as much mass as we observed in the Universe," declares GArcía.

The authors also point out that no molecular gas was detected in this area of ​​the galaxy, an ingredient that until now was considered essential to be able to form stars . However, recent theoretical simulations have found that, in poor metal environments, it is possible to form stars from the neutral gas phase. Understanding how stars form in gas clouds with few metals is a fundamental step to understand how the first stars of the Universe were formed, how much mass they had and what impact they had on primitive galaxies.

The study proposes" that the mechanisms of star formation can be different in different parts of galaxies, depending of local conditions and, in particular, of gas density ", as explained by CAB researcher Miriam García. & nbsp;

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This new article is part of a long-term research project in which galaxies are being explored beyond the Small Magellanic Cloud with the Gran Telescopio Canarias ( GTC) and the Very Large Telescope (VLT).

Scientific article in Monthly Notices of The Royal Astronomy Society: & nbsp;

'Ongoing star formation at the outskirts of Sextans-A: spectroscopic detection of early O-type stars', by Miriam García, Artemio Herrero, Francisco Najarro, Inés Camacho and Marta Lorenzo.


Fuente: UCC-CAB

Fecha: 2019-02-01


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