New insights in the origin and evolution of the old, metal-rich open cluster NGC 6791

Abstract

NGC 6791 is one of the most studied open clusters, it is massive ($\sim 5000M_{\odot }$), located at the solar circle, old ($8$Gyr) and yet the most metal-rich cluster ($[Fe/H]\simeq 0.4$) known in the Milky Way. By performing an orbital analysis within a Galactic model including spiral arms and a bar, we found that it is plausible that NGC 6791 formed in the inner thin disc or in the bulge, and later displaced by radial migration to its current orbit. We apply different tools to simulate NGC 6791, including direct $N$-body summation in time-varying potentials, to test its survivability when going through different Galactic environments. In order to survive the 8 Gyr journey moving on a migrating orbit, NGC 6791 must have been more massive, $M_0\ge 5\times 10^4{M}_{\odot }$, when formed. We find independent confirmation of this initial mass in the stellar mass function, which is observed to be flat; this can only be explained if the average tidal field strength experienced by the cluster is stronger than what it is at its current orbit. Therefore, the birth place and journeys of NGC 6791 are imprinted in its chemical composition, in its mass loss, and in its flat stellar mass function, supporting its origin in the inner thin disc or in the bulge.

14 pages, 10 Figures, 3 Tables. Accepted for publication in MNRAS

References in corpus (20)

• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• Dynamical modelling of the Galactic bulge and bar: the Milky Way's bar pattern speed, stellar, and dark matter mass distribution
• Star cluster disruption by giant molecular clouds
• Black holes and core expansion in massive star clusters
• The life cycle of star cluster in a tidal field
• The orbits of open clusters in the Galaxy
• The effect of spiral arm passages on the evolution of stellar clusters
• Stellar Kinematic Constraints on Galactic Structure Models Revisited: Bar and Spiral Arm Resonances
• A stellar-mass black hole population in the globular cluster NGC 6101?
• A new standard: Age and distance for the open cluster NGC 6791 from the eclipsing binary member V20
• Sodium and Oxygen Abundances in the Open Cluster NGC 6791 from APOGEE H-Band Spectroscopy
• High resolution infrared spectroscopy of the old open cluster NGC6791
• A New Look at the Old Star Cluster NGC 6791
• Evidence of tidal distortions and mass loss from the old open cluster NGC 6791
• The origin and orbit of the old, metal-rich, open cluster NGC 6791: Insights from kinematics
• The absolute motion of the peculiar cluster NGC6791
• The Contribution of Spiral Arms to the Thick Disk along the Hubble Sequence
• Two Populations of Open Star Clusters in the Galaxy
• On the Survival of High-Altitude Open Clusters within the Milky Way Galaxy Tides
• Massive open star clusters using the VVV survey III: A young massive cluster at the far edge of the Galactic bar

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• Age dissection of the Milky Way discs: red giants in the Kepler field
• The (im)possibility of strong chemical tagging
• Exploring the s-process history in the Galactic disk: Cerium abundances and gradients in Open Clusters from the OCCAM/APOGEE sample
• Open Clusters as Tracers on Radial Migration of the Galactic Disk
• UVIT Open Cluster Study. X. Rich Collection of Post Mass Transfer Systems in NGC 6791
• The imprint of arms and bars on rotation curves: in-plane and off-plane
• Study of the Open Clusters in Kepler Prime Field
• Evidence for Dynamical Filtering: High Binary Fraction, Hard-binary Excess, and Unresolved Triples in the Surviving Core of NGC 6791