An extended stellar halo discovered in the Fornax dwarf spheroidal using Gaia EDR3. (2022)
Keywords :
proper motions - galaxies dwarf - galaxies: Local Group
Abstract:We have studied the extent of the Red Giant Branch stellar population in the Fornax dwarf spheroidal galaxy using the spatially extended and homogeneous data set from Gaia EDR3. Our pre-selection of stars belonging to Fornax is based on their proper motions, parallaxes, and colour-magnitude diagram. The latter criteria provide a Fornax star sample, which we further restrict by colour and magnitude to eliminate contaminations due to either Milky Way stars or QSOs. The precision of the data has been sufficient to reach extremely small contaminations (0.02-0.3 per cent), allowing us to reach to a background level 12 magnitudes deeper than the central surface brightness of Fornax. We discover a break in the density profile, which reveals the presence of
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In this paper, we present a case study on Fornax, using Gaia EDR3.
Thanks to its homogeneous coverage and data quality, we can explore
the data over a very large area. Both coverage and calibrations across
large field are difficulties for ground-based and mosaic-type
observations on dSphs. Our goal is to search possible faint structures
in the outskirts of Fornax using Gaia data.
The data is a chosen field of 20 by 20 degrees centred on Fornax. This
very large area, more than 30 times larger than Fornax in diameter
should be enough to reach and robustly determine the outskirts of
Fornax. We select Fornax candidate members by focusing our study on
RGB branch on CMDs , also we did a PM and a parallax selection (i.e
see section 4). These three selections give the S_BASE_ in which we
seperate it in 3 final samples by adding Gmag and BP-RP criteria. We
present these giving stars lists in tables s0cand.dat, s1cand.dat and
s2cand.dat.
Next, as explained in the section 5.2, We derive and analyse the
radial surface-density profile for each three member candidate samples
by applying the same algorithm. The surface-density profil are
presented in tables s0dens.dat, s1dens.dat and s2dens.dat.
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- J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
- J/A+A/649/A7 : MC structure and properties (Gaia Collaboration+, 2021)
- J/ApJ/789/147 : Star formation histories of LG dwarf galaxies (Weisz+, 2014)
- J/MNRAS/453/690 : Fornax VST ATLAS catalogue (Bate+, 2015)
- J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
- I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
