The family pictures of our neighbours: investigating the mass function and dynamical parameters of nearby open clusters

Abstract

We determine the mass functions (MFs) and the dynamical parameters of 15 nearby open clusters (OCs) using the unprecedented data set of the Gaia Early Data Release 3. We select the members of each cluster by combining the photometric (colour and magnitude) and astrometric (parallax and proper motions) parameters of stars, minimizing the contamination from Galactic field interlopers. By comparing the observed distribution of stars along the cluster main sequence with the best-fitting synthetic population, we find the present-day MF and the binary fraction of the OCs, along with their dynamical parameters like mass, half-mass radius, and half-mass relaxation time. We found that the global present-day MF of OCs are consistent with a single power-law function, $F(m)\propto m^{\alpha }$, with slopes $-3<\alpha <-0.6$ including both subsolar, $0.2<m/{\text{M}}_{\odot }<1$, and supersolar mass regimes. A significant correlation between the MF-slope and the ratio of age to half-mass relaxation time is evidenced, similarly to the same conclusion already observed among Galactic globular clusters. However, OCs evolve along different tracks in comparison with the globular clusters, possibly indicating primordial differences in their initial mass function (IMF). The comparison with Monte Carlo simulations suggests that all the analysed OCs could have been born with an IMF with slope ${\alpha }_{\text{IMF}}<-2.3$. We also show that the less evolved OCs have a MF consistent with that of the solar neighbourhood, indicating a possible connection between the dissolution of OCs and the formation of the Galactic disc.

20 pages, 14 figures, accepted for publication by MNRAS

References in corpus (27)

• Analytical theory for the initial mass function: CO clumps and prestellar cores
• The Stellar Populations of Praesepe and Coma Berenices
• Clusters and mirages: cataloguing stellar aggregates in the Milky Way
• Age determination for 269 $Gaia$ DR2 Open Clusters
• Hunting for open clusters in \textit{Gaia} DR2: $582$ new OCs in the Galactic disc
• The fraction of binary systems in the core of thirteen low-density Galactic globular clusters
• CCD BV survey of 42 open clusters
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Discovery of Tidal Tails in Disrupting Open Clusters: Coma Berenices and a Neighbor Stellar Group
• The Seven Sisters DANCe. I. Empirical isochrones, Luminosity and Mass Functions of the Pleiades cluster
• 3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3: its Relation to Cluster Dynamics
• The global mass functions of 35 Galactic globular clusters: I. Observational data and correlations with cluster parameters
• The bound fraction of young star clusters
• Completeness of the Gaia-verse II: what are the odds that a star is missing from Gaia DR2?
• The lower mass function of the young open cluster Blanco 1: from 30 Mjup to 3 Mo
• Exploring open cluster properties with Gaia and LAMOST
• Testing the universality of the IMF with Bayesian statistics: young clusters
• Diagnosing the Stellar Population and Tidal Structure of the Blanco1 Star Cluster
• The Global Mass Functions of 35 Galactic globular clusters: II. Clues on the Initial Mass Function and Black Hole Retention Fraction
• Mass functions and photometric binaries in nine open clusters
• Direct $N$-body simulations of globular clusters - II. Palomar 4
• A bottom-heavy initial mass function for the likely-accreted blue-halo stars of the Milky Way
• Radial Variation in the Stellar Mass Functions of Star Clusters
• Characterizing low contrast Galactic open clusters with GAIA DR2
• New Insight into the stellar mass function of Galactic globular clusters
• Treatment of realistic tidal field in Monte Carlo simulations of star clusters
• Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm

Cited by in corpus (9)

• Revisiting the mass of open clusters with \emph{Gaia} data
• Evidence for a bottom-light initial mass function in massive star clusters
• Photometric binaries, mass functions, and structural parameters of 78 Galactic open clusters
• The multiplicity fraction in 202 open clusters from Gaia
• The membership of stars, density profile and mass segregation in open clusters using a new machine learning-based method
• Mass-Dependent Radial Distribution of Single and Binary Stars in the Pleiades and their Dynamical Implications
• A new tool to derive simultaneously exponent and extremes of power-law distributions
• The Small Magellanic Cloud through the lens of the James Webb Space Telescope : binaries and mass function within the galaxy outskirts
• Stellar masses and mass ratios for Gaia open cluster members