Extended stellar halo detected in the Fornax galaxy

Tomasz Nowakowski is a writer for Phys.org.

Astronomers have explored the Fornax dwarf spheroidal galaxy using the Gaia space observatory. They discovered that the galaxy has a stellar halo that spans more than 17,000 light years. The paper was published on the arXiv pre-print repository.

Fornax is the second-brightest dwarf spheroidal galaxy in the Milky Way halo. The universe is 460,000 light years away from the Earth and contains six clusters.

A team of astronomer led byYanbin Yang of Paris Observatory in France investigated the stellar structure of Fornax over a large area. This was possible because of the full coverage of proper motion measurement by the Gaia satellites. The main goal of the study was to explore the extent of the red giant branch.

In this paper, we present a case study on Fornax. We can explore the data over a large area because of its homogeneity. The researchers explained that both coverage and calibrations are difficult for ground-based and mosaic-type observations on dSphs.

A break in the density profile of Fornax was identified by the study as a significant component in the galaxy that resembled a stellar halo. It spans out to 17,600 light years and is estimated to have a mass of about 10 percent. The data shows that the Fornax galaxy may extend even farther.

The extended stellar halo may be due to the recent expansion of stars in Fornax. Detailed numerical modeling is required to confirm this hypothesis. The circumgalactic medium is a diffuse and ionized gas.

The researchers noted that their discovery may have implications for our understanding of other dwarf spheroidal galaxies. They want to study the breaks in density profiles.

Almost all dSphs, except Fornax, are reported to have a break in their density profiles. The authors of the paper wrote that if this second component of Fornax can be explained as the result of expanding stars, how about the other dSphs?

Further studies should focus on identifying the component responsible for the break in their density profile and whether they are consistent with tidal stripping or tidal shocking. In the future, this could be verified with proper motions by Gaia.

More information: Yanbin Yang et al, An extended stellar halo discovered in the Fornax dwarf spheroidal using Gaia EDR3. arXiv:2203.01953v1 [astro-ph.GA], arxiv.org/abs/2203.01953

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