The mass function of IC4665 revisited by the UKIDSS Galactic Clusters Survey

Abstract

Knowledge of the mass function in open clusters constitutes one way to constrain the formation of low-mass stars and brown dwarfs as does the knowledge of the frequency of multiple systems and the properties of disks. The aim of the project is to determine the shape of the mass function in the low-mass and substellar regimes in the pre-main sequence (27 Myr) cluster IC4665, which is located at 350 pc from the Sun. We have cross-matched the near-infrared photometric data from the Eighth Data Release of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey with previous optical data obtained with the Canada-France-Hawaii wide-field camera to improve the determination of the luminosity and mass functions in the low-mass and substellar regimes. The availability of i and z photometry taken with the CFH12K camera on the Canada France Hawaii Telescope added strong constraints to the UKIDSS photometric selection in this cluster, which is located in a dense region of our Galaxy. We have derived the luminosity and mass functions of the cluster down to J=18.5 mag, corresponding to masses of ~0.025 Msun at the distance and age of IC4665 according to theoretical models. In addition, we have extracted new candidate members down to ~20 Jupiter masses in a previously unstudied region of the cluster. We have derived the mass function over the 0.6-0.04 Msun mass range and found that it is best represented by a log-normal function with a peak at 0.25-0.16 Msun, consistent with the determination in the Pleiades.

11 pages, 8 figures, 4 tables in main text, 3 electronic tables in Appendices available from CDS. Accepted by A&A

References in corpus (13)

• The UKIRT Infrared Deep Sky Survey (UKIDSS)
• The WFCAM Science Archive
• Near-infrared cross-dispersed spectroscopy of brown dwarf candidates in the Upper Sco association
• New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs in Upper Sco
• The lower mass function of the young open cluster Blanco 1: from 30 Mjup to 3 Mo
• Near-infrared low-resolution spectroscopy of Pleiades L-type brown dwarfs
• Pleiades low-mass brown dwarfs: the cluster L dwarf sequence
• Detection of the lithium depletion boundary in the young open cluster IC 4665
• New members in the Upper Sco association from the UKIDSS Early Data Release
• Employing a New BVIc Photometric Survey of IC 4665 to Investigate the Age of this Young Open Cluster
• Low Mass Stars and Brown Dwarfs in Praesepe

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• Spectroscopy of new brown dwarf members of rho Ophiuchi and an updated initial mass function
• Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?
• Photometry Transformation from RGB Bayer Filter System to Johnson-Cousins BVR Filter System
• IC 4665 DANCe I. Members, empirical isochrones, magnitude distributions, present-day system mass function, and spatial distribution
• Searching for debris discs in the 30 Myr open cluster IC 4665