Lithium and beryllium in the Gaia-Enceladus galaxy

Data from Gaia DR2 and The Apache Point Observatory Galactic Evolution Experiment surveys revealed a relatively new component in the inner Galactic halo, which is likely the dynamical remnant of a disrupted dwarf galaxy named Gaia-Enceladus that collided with the Milky Way about 10 Gyr ago. This merging event offers an extraordinary opportunity to study chemical abundances of elements in a dwarf galaxy, since they are generally hampered in external galaxies. Here, we focus on Li-7 and Be-9 in dwarf stars that are out of reach even in Local Group galaxies. Searching in GALAH, Gaia-ESO survey and in literature, we found several existing Li-7 abundance determinations of stars belonging to the Gaia-Enceladus galaxy. The Li-7 abundances of stars at the low metallicity end overlap with those of the Galactic halo. These are effective extragalactic Li-7 measurements, which suggest that the Li-7 Spite plateau is universal, as is the cosmological Li-7 problem. We found a Li-7-rich giant out of 101 stars, which suggests a small percentage similar to that of the Milky Way. We also collect Be-9 abundance for a subsample of 25 Gaia-Enceladus stars from literature. Their abundances share the Galactic [Be/H] values at the low metallicity end but grow slower with [Fe/H] and show a reduced dispersion. This suggests that the scatter observed in the Milky Way could reflect the different Be-9 evolution patterns of different stellar components that are mixed-up in the Galactic halo.