The outermost cluster of M31

We report on the identification of a new cluster in the far halo of the M31 galaxy. The cluster, named Bologna 514 (B514) has an integrated magnitude M v = -8.5 ± 0.6, and a radial velocity, as estimated from two independent low-resolution spectra, V r = -456 ± 23 km s -1 , which fully confirms its membership to the M31 system. The observed integrated spectrum is very similar to those of classical globular clusters. Being located at ≃4° (=55 kpc in projected distance) from the center of the parent galaxy, B514 is by far the most remote M 31 cluster ever discovered. Its projected position, near the galaxy major axis, and M 31 -centric velocity, similar to that observed in the outermost regions of the HI rotation curve, may indicate that it belongs to the subsystem of M 31 clusters that has been recently proposed (Morrison et al. 2004 ) to be part of the dynamically-cold thin disc of the galaxy.