Brown dwarfs and very low mass stars in the Praesepe open cluster: a dynamically unevolved mass function?

Abstract

[Abridged] In this paper, we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age of 590[+150][-120]Myr and distance of 190[+6.0][-5.8]pc) and use this to infer its mass function which we compare with that of other clusters. We have performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe with a spatial coverage of 3.1deg^2. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is sensitive to objects with masses from about 0.6 to 0.05Msol. The mass function of Praesepe rises from 0.6Msol down to 0.1Msol and then turns-over at ~0.1Msol. The rise observed is in agreement with the mass function derived by previous studies, including a survey based on proper motion and photometry. Comparing our mass function with that for another open cluster with a similar age, the Hyades (age ~ 600Myr), we see a significant difference. Possible reasons are that dynamical evaporation has not influenced the Hyades and Praesepe in the same way, or that the clusters did not have the same initial mass function, or that dynamical interactions have modified the evolution of one or both clusters. Although a difference in the binary fractions of the clusters could cause the observed (i.e. system) mass functions to differ, measurements in the literature give no evidence for a significant difference in the binary fractions of the two clusters. Of our cluster candidates, six have masses predicted to be equal to or below the stellar/substellar boundary at 0.072Msol.

11 pages, 11 figures, accepted for publication in A&A. Higher resolution of Figures 2-3-4-5 in A&A published version. Revised version corrected for English

References in corpus (11)

• Empirical Color Transformations Between SDSS Photometry and Other Photometric Systems
• The Solar Neighborhood XVII: Parallax Results from the CTIOPI 0.9m Program -- Twenty New Members of the RECONS 10 Parsec Sample
• The Stellar Populations of Praesepe and Coma Berenices
• The Distances to Open Clusters from Main-Sequence Fitting. III. Improved Accuracy with Empirically Calibrated Isochrones
• The effect of rotation on the abundances of the chemical elements of the A-type stars in the Praesepe cluster
• Abundances of four open clusters from solar stars
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Contamination by field late-M, L and T dwarfs in deep surveys
• A search for substellar members in the Praesepe and sigma Orionis clusters
• The spatial distribution of substellar objects in IC348 and the Orion Trapezium Cluster
• A Constraint on brown dwarf formation via ejection: radial variation of the stellar and substellar mass function of the young open cluster IC2391

Cited by in corpus (18)

• A Universal Stellar Initial Mass Function? A Critical Look at Variations
• Inverse dynamical population synthesis: Constraining the initial conditions of young stellar clusters by studying their binary populations
• A deep all-sky census of the Hyades
• A 5D view of the Alpha Per, Pleiades, and Praesepe clusters
• Astrometric and photometric initial mass functions from the UKIDSS Galactic Clusters Survey: I The Pleiades
• Testing the universality of the IMF with Bayesian statistics: young clusters
• The stellar mass function, binary content and radial structure of the open cluster Praesepe derived from PPMXL and SDSS data
• Astrometric and photometric initial mass functions from the UKIDSS Galactic Clusters Survey: III Praesepe
• Characterization of the Praesepe Star Cluster by Photometry and Proper Motions with 2MASS, PPMXL, and Pan-STARRS
• Spectral library of age-benchmark low-mass stars and brown dwarfs
• The evolution of luminosity, colour and the mass-to-luminosity ratio of Galactic open clusters: comparison of discrete vs. continuous IMF models
• The family pictures of our neighbours: investigating the mass function and dynamical parameters of nearby open clusters
• The Factory and the Beehive. IV. A Comprehensive Study of the Rotation X-ray Activity Relation in Praesepe and the Hyades
• Measuring the Initial Mass Function of Low Mass Stars and Brown Dwarfs
• Low Mass Stars and Brown Dwarfs in Praesepe
• The substellar mass function in the central region of the open cluster Praesepe from deep LBT observations
• Goodness-of-fit test for isochrone fitting in the Gaia era. Statistical assessment of the error distribution
• Two close binaries across the hydrogen-burning limit in the Praesepe open cluster