2017/01/30 by Anton F. Seleznev, A. F. Seleznev, Giovanni Carraro +7
Physics and Astronomy · #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Astrophysics and Star Formation Studies #Cluster (spacecraft) #Galaxy #Initial mass function #Luminosity #Luminosity function #Mass distribution #Mass segregation #Milky Way #Open cluster #Physics #Star cluster #Star formation #Stars #Stellar mass #Stellar, planetary, and galactic studies #Virial mass #Virial theorem #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stx177
openalex publication_date 2017/01/30 · arxiv created 2017/02/10 · arxiv updated 2017/03/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Only a small number of Galactic open clusters survive for longer than a few hundred million years. Longer lifetimes are routinely explained in term of larger initial masses, particularly quiet orbits and off-plane birthplaces. We derive in this work the actual mass of NGC 4337, one of the few open clusters in the Milky Way inner disc that has managed to survive for about 1.5 Gyr. We derive its mass in two different ways. First, we exploit an unpublished photometric data set in the UBVI passbands to estimate – using star counts – the cluster luminosity profile, luminosity and mass function and hence its actual mass from both the luminosity profile and mass function. This data set is also used to infer crucial cluster parameters, such as the cluster half-mass radius and distance. Secondly, we make use of a large survey of cluster star radial velocities to derive dynamical estimates for the cluster mass. Using the assumption of virial equilibrium and neglecting the external gravitational field leads to values for the mass significantly larger than those obtained by means of the observed density distribution or with the mass function, but still marginally compatible with the inferred values of invisible mass in the form of both low-mass stars and remnants of high-mass stars in the cluster. Finally, we derive the cluster initial mass by computing the mass loss experienced by the cluster during its lifetime and adopting the various estimates of the actual mass.