The initial mass function and the surface density profile of NGC 6231

dc.contributor.authorSung, Hwangkyung
dc.contributor.authorSana, Hugues
dc.contributor.authorBessell, Michael
dc.date.accessioned2015-12-13T22:15:52Z
dc.date.issued2013
dc.date.updated2016-02-24T08:57:01Z
dc.description.abstractWe have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initial mass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical to mid-infrared color excess ratios, and found that the total-to-selective extinction ratio is RV = 3.2, which is very close to the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived the surface density profiles of four member groups, and found that they reach the surface density of field stars at about 10′, regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8-45 M . The slope of the IMF of NGC 6231 (Γ = -1.1 ± 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition, the mass function varies systematically, and is a strong function of radius - it is very shallow at the center, and very steep at the outer ring suggesting the cluster is mass segregated. We confirm the mass segregation for the massive stars (m ≳ 8 M) by a minimum spanning tree analysis. Using a Monte Carlo method, we estimate the total mass of NGC 6231 to be about 2.6 (± 0.6) × 103 M. We constrain the age of NGC 6231 by comparison with evolutionary isochrones. The age of the low-mass stars ranges from 1 to 7 Myr with a slight peak at 3 Myr. However, the age of the high-mass stars depends on the adopted models and is 3.5 ± 0.5 Myr from the non-rotating or moderately rotating models of Brott et al. as well as the non-rotating models of Ekström et al. But the age is 4.0-7.0 Myr if the rotating models of Ekström et al. are adopted. This latter age is in excellent agreement with the timescale of ejection of the high-mass runaway star HD 153919 from NGC 6231, albeit the younger age cannot be entirely excluded.
dc.identifier.issn0004-6256
dc.identifier.urihttp://hdl.handle.net/1885/70602
dc.publisherUniversity of Chicago Press
dc.rightsAuthor/s retain copyrighten_AU
dc.sourceAstronomical Journal
dc.subjectKeywords: open clusters and associations: individual (NGC 6231); stars: formation; stars: pre-main sequence Online-only material: color figures, machine-readable and VO tables
dc.titleThe initial mass function and the surface density profile of NGC 6231
dc.typeJournal article
dcterms.accessRightsOpen Accessen_AU
local.bibliographicCitation.issue2
local.bibliographicCitation.startpage15
local.contributor.affiliationSung, Hwangkyung, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationSana, Hugues, Amsterdam University
local.contributor.affiliationBessell, Michael, College of Physical and Mathematical Sciences, ANU
local.contributor.authoremailu6900904@anu.edu.au
local.contributor.authoruidSung, Hwangkyung, u3730936
local.contributor.authoruidBessell, Michael, u6900904
local.description.notesImported from ARIES
local.identifier.absfor020100 - ASTRONOMICAL AND SPACE SCIENCES
local.identifier.ariespublicationf5625xPUB2358
local.identifier.citationvolume145
local.identifier.doi10.1088/0004-6256/145/2/37
local.identifier.scopusID2-s2.0-84872694569
local.identifier.thomsonID000313571600011
local.identifier.uidSubmittedByf5625
local.type.statusPublished Version

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