How well do we know the age and mass distributions of the star cluster system in the Large Magellanic Cloud?

被引:90
作者
de Grijs, R
Anders, P
机构
[1] Univ Sheffield, Dept Phys & Astron, Sheffield S3 7RH, S Yorkshire, England
[2] Univ Gottingen, Inst Astrophys, D-37077 Gottingen, Germany
关键词
methods : data analysis; Magellanic Clouds; galaxies : star clusters; galaxies : stellar content;
D O I
10.1111/j.1365-2966.2005.09856.x
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The Large Magellanic Cloud (LMC) star cluster system offers the unique opportunity to independently check the accuracy of age (and the corresponding mass) determinations based on a number of complementary techniques. Using our sophisticated tool for star cluster analysis based on broad-band spectral energy distributions (SEDs), 'AnalySED', we re-analyse the Hunter et al. LMC cluster photometry. Our main aim is to set the tightest limits yet on the accuracy of absolute age determinations based on broad-band SEDs, and therefore on the usefulness of such an approach. Our broad-band SED fits yield reliable ages, with statistical absolute uncertainties within Delta log(Age/yr) similar or equal to 0.4 overall. The systematic differences we find with respect to previous age determinations are caused by conversions of the observational photometry to a different filter system, thus leading to systematically inaccurate results. The LMC's cluster formation rate (CFR) has been roughly constant outside of the well-known age gap between similar to 3 and 13 Gyr, when the CFR was a factor of similar to 5 lower. Using a simple approach to derive the characteristic cluster disruption time-scale, we find that log(t(4)(dis)/yr) = 9.9 +/- 0.1, where t(dis)=t(4)(dis)(M-cl/10(4) M-circle dot)(0.62). This long characteristic disruption time-scale implies that we are observing the initial cluster mass function (CMF). We conclude that while the older cluster (sub)samples show CMF slopes that are fully consistent with the alpha similar or equal to-2 slopes generally observed in young star cluster systems, the youngest mass and luminosity-limited LMC cluster subsets show shallower slopes (at least below masses of a few x10(3) M-circle dot), which is contrary to dynamical expectations. This may imply that the initial CMF slope of the LMC cluster system as a whole is not well represented by a power law, although we cannot disentangle the unbound from the bound clusters at the youngest ages.
引用
收藏
页码:295 / 307
页数:13
相关论文
共 70 条
[1]   Analysing observed star cluster SEDs with evolutionary synthesis models: systematic uncertainties [J].
Anders, P ;
Bissantz, N ;
Alvensleben, UFV ;
de Grijs, R .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2004, 347 (01) :196-212
[2]   Spectral and photometric evolution of young stellar populations: The impact of gaseous emission at various metallicities [J].
Anders, P ;
von Alvensleben, UF .
ASTRONOMY & ASTROPHYSICS, 2003, 401 (03) :1063-1070
[3]  
ANDERS P, 2005, UNPUB APJL
[4]   ANALYSIS OF THE UV SPECTRA OF YOUNG CLUSTERS OF THE LARGE MAGELLANIC CLOUD [J].
BARBARO, G ;
OLIVI, FM .
ASTRONOMICAL JOURNAL, 1991, 101 (03) :922-932
[5]   The star cluster population of M51 - II. Age distribution and relations among the derived parameters [J].
Bastian, N ;
Gieles, M ;
Lamers, HJGLM ;
Scheepmaker, RA ;
de Grijs, R .
ASTRONOMY & ASTROPHYSICS, 2005, 431 (03) :905-924
[6]   Testing stellar population models with star clusters in the Large Magellanic Cloud [J].
Beasley, MA ;
Hoyle, F ;
Sharples, RM .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2002, 336 (01) :168-188
[7]   Explaining the mysterious age gap of globular clusters in the Large Magellanic Cloud [J].
Bekki, K ;
Couch, WJ ;
Beasley, MA ;
Forbes, DA ;
Chiba, M ;
Da Costa, GS .
ASTROPHYSICAL JOURNAL, 2004, 610 (02) :L93-L96
[8]  
BICA E, 1990, ASTRON ASTROPHYS, V235, P103
[9]  
BICA E, 1986, ASTRON ASTROPHYS, V156, P261
[10]   Integrated UBV photometry of 624 star clusters and associations in the Large Magellanic Cloud [J].
Bica, E ;
Claria, JJ ;
Dottori, H ;
Santos, JFC ;
Piatti, AE .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1996, 102 (01) :57-73