Tidal tails in the disintegrating open cluster NGC 752

Abstract

We utilize the robust membership determination algorithm, ML-MOC, on the precise astrometric and deep photometric data from Gaia Early Data Release 3 within a region of radius 5° around the centre of the intermediate-age Galactic open cluster NGC 752 to identify its member stars. We report the discovery of the tidal tails of NGC 752, extending out to ~35 pc on either side of its denser central region and following the cluster orbit. From comparison with PARSEC stellar isochrones, we obtain the mass function of the cluster with a slope, χ = -1.26 ± 0.07. The high negative value of χ is indicative of a disintegrating cluster undergoing mass segregation. χ is more negative in the intra-tidal regions as compared to the outskirts of NGC 752. We estimate a present day mass of the cluster, $M\rm _{C} = 297\pm 10$ M_⊙. Through mass-loss due to stellar evolution and tidal interactions, we further estimate that NGC 752 has lost nearly 95.2-98.5 per cent of its initial mass, M_i = 0.64-2 × 10⁴ M_⊙.