Euclid: Early Release Observations -- The extended stellar component of the IC10 dwarf galaxy

We present a detailed analysis of the old, extended stellar component of the Local Group dwarf galaxy IC, 10 using deep resolved-star photometry in the VIS and NISP bands of the Euclid Early Release Observations. Leveraging Euclid's unique combination of a wide field of view and high spatial resolution, we traced red giant branch (RGB) stars out to ∼, 8, kpc from the galaxy centre, reaching azimuthally averaged surface brightness levels as faint as ̋E ∼, 29, mag, arcsec-2. Our analysis reveals that IC, 10’s stellar distribution is significantly more extended than previously assumed. After correcting for foreground extinction and subtracting contamination from Milky Way stars and background galaxies, we derived a radial stellar density profile from the RGB star counts. The profile shows a marked flattening beyond ∼, 5, kpc and it is best fit by a two-component (Sérsic + exponential) model, yielding a total stellar mass in old (age ≳, 1, Gyr) stars of M_⋆= (6. 7--8. 1) times10⁸, gas in the outer regions of IC, 10; alternatively, it might represent an ancient `in situ' stellar halo. We tentatively detected two symmetric stellar overdensities at the edge of our imagery, which are roughly aligned with the direction of IC, 10's orbit around M31, suggesting that they could be signatures of tidal stripping. As part of our analysis, we derived a new distance to IC, 10 based on the tip of the RGB, finding D=762± 20, kpc with a distance modulus of (m-M) ₀=24. 41± 0. 05. The origin of the outer stellar component is unclear. It might have been accreted or even possibly associated with the counter-rotating H i