Observational templates of star cluster disruption. The stellar group NGC 1901 in front of the Large Magellanic Cloud

Abstract

Observations indicate that present-day star formation in the Milky Way disk takes place in stellar ensembles or clusters rather than in isolation. Bound, long lived stellar groups are known as open clusters. They gradually lose stars and in their final evolutionary stages they are severely disrupted leaving an open cluster remnant made of a few stars. In this paper, we study in detail the stellar content and kinematics of the poorly populated star cluster NGC1901. This object appears projected against the Large Magellanic Cloud. The aim of the present work is to derive the current evolutionary status, binary fraction, age and mass of this stellar group. These are fundamental quantities to compare with those from N-body models in order to study the most general topic of star cluster evolution and dissolution.The analysis is performed using wide-field photometry in the UBVI pass-band, proper motions from the UCAC.2 catalog, and 3 epochs of high resolution spectroscopy, as well as results from extensive N-body calculations.The star group NGC1901 is found to be an ensemble of solar metallicity stars, 400+/-100 Myr old, with a core radius of 0.23 pc, a tidal radius of 1.0 pc, and located at 400+/-50 pc from the Sun. Out of 13 confirmed members, only 5 single stars have been found. Its estimated present-day binary fraction is at least 62%. The calculated heliocentric space motion of the cluster is not compatible with possible membership in the Hyades stream.Our results show that NGC1901 is a clear prototype of open cluster remnant characterized by a large value of the binary fraction and a significant depletion of low-mass stars. In the light of numerical simulations, this is compatible with NGC1901 being what remains of a larger system initially made of 500-750 stars.

arXiv comment13 pages, 12 eps figures (some of them degraded in resolution), accepted for publication in Astronomy and Astrophysics

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Cited by in corpus (16)

• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• Chemical abundance analysis of the Open Clusters Berkeley 32, NGC 752, Hyades and Praesepe
• On the metallicity of open clusters II. Spectroscopy
• The Gaia-ESO Survey: the present-day radial metallicity distribution of the Galactic disc probed by pre-main-sequence clusters
• On the alpha-element gradients of the Galactic thin disk using Cepheids
• Three Galactic globular cluster candidates
• The PLATO field selection process I. Identification and content of the long-pointing fields
• The velocity distribution of nearby stars from Hipparcos data II. The nature of the low-velocity moving groups
• The Gaia-ESO Survey: metallicity of the Chamaeleon I star forming region
• The GALAH Survey and Gaia DR2: (Non)existence of five sparse high-latitude open clusters
• Towards a photometric metallicity scale for open clusters
• Investigating dynamical properties of evolved Galactic open clusters
• Dependence of Kinematics on the Age of Stars in the Solar Neighborhood
• Not an open cluster after all: the NGC 6863 asterism in Aquila
• Young nearby open clusters and their luminosity functions
• NGC 1252: a high altitude, metal poor open cluster remnant