Dwarf irregular galaxy Leo A extends even farther, according to HST WFC3 photometry⋆
Center for Physical Sciences and Technology, Saulėtekio av. 3, 10257 Vilnius, Lithuania
2 Vilnius University Observatory, Čiurlionio 29, 03100 Vilnius, Lithuania
Accepted: 18 January 2018
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).
Key words: galaxies dwarf / galaxies stellar content / galaxies: individual: Leo A (DDO 69)
Photometric data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A144
© ESO 2018