2018A&A...614A.144S

Context. Leo A is an isolated gas-rich dwarf irregular galaxy of low stellar mass and metallicity residing at the outskirts of the Local Group. Ages of the stellar populations in Leo A range from ∼10 Myr to ∼10 Gyr. A large stellar halo (up to the deprojected distance of ∼1.7 kpc) was discovered based on Subaru wide-field photometry of red giant branch stars.
Aims. We aim to study stellar populations at the very outer region of the Leo A galaxy.
Methods. We analysed HST WFC3 archive observation data in the field that is partly located beyond the previously known limits of the Leo A galaxy. We performed photometry of star-like objects in the F475W and F814W passbands and studied the spatial distribution of the Leo A stars below the horizontal branch.
Results. We report a discovery of stellar halo populations (subgiants and faint red giants) in the Leo A galaxy extending up to ∼2.3 kpc deprojected distance from the galaxy centre. Analysis of the colour-magnitude diagram suggests old (>5 Gyr) stellar populations of very low metallicity (Z ∼ 0.0001).