Extended stellar halo discovered in the Fornax galaxy

(ORDO NEWS) — Using ESA’s Gaia space observatory, astronomers have studied the dwarf spheroidal galaxy Fornax. They found in it an extended stellar halo spanning more than 17,000 light-years.

Fornax, discovered in 1938, is the second brightest dwarf spheroidal galaxy (dSph) in the Milky Way’s halo. The galaxy is located about 460,000 light-years from Earth and consists of six globular clusters.

Recently, a team of astronomers led by Yanbin Yang of the Paris Observatory in France examined the Fornax stellar structure over a relatively large area (400 square degrees).

This was made possible by the uniform quality of data from the Gaia satellites and the full coverage of proper motion measurements. The main goal of their study was to study the size of the stellar population of the red giant branch (RGB) in this galaxy.

The study found a gap in Fornax’s density profile, revealing a significant component in this galaxy that resembles a stellar halo due to its nearly symmetrical morphology. It spans 17,600 light-years and has a mass estimated at about 10% of that of the galaxy. The data also suggests that the Fornax galaxy may extend even further.

Astronomers speculate that the expanded stellar halo detected could be related to the recent expansion of stars in Fornax. Detailed numerical simulations will be required to confirm this hypothesis. Such a scenario assumes that the Milky Way’s halo is filled with a diffuse and ionized gas – the circumgalactic medium (CGM).

The researchers noted that their discovery could have implications for understanding other dwarf spheroidal galaxies in the Milky Way. They propose to study such discontinuities in the density profiles of these dwarf spheroidal galaxies.

“With Fornax, almost all dwarf spheroidal galaxies except Leo II are reported to show such a discontinuity in density profiles. If this second Fornax component can be explained as the result of stellar expansion, what about other dwarf spheroidal galaxies?” written by the authors of the article.


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