UV (200 nm) observation of the A2111 galaxies cluster

An ultraviolet image of the Butcher-Oemler cluster A2111 (z=0.229) has been obtained with the FOCA balloon-borne telescope. In this UV magnitude-limited sample, 19 galaxies are found at the cluster redshift from a follow-up with the Norris spectroscope at the Palomar 5m telescope, some of them lie as far as ∼7 Mpc (H0=50, q0=0.1) from the cluster center. Comparison with the Coma cluster shows that UV-luminous A2111 galaxies are 0.7 mag brighter in UV, indicating that the star formation rate is twice as high in these galaxies.