J/A+A/490/151 Photometric evolution of star clusters models (Kruijssen+, 2008)
The photometric evolution of star clusters and the preferential loss of low-mass
stars with an application to globular clusters.
Kruijssen J.M.D., Lamers H.J.G.L.M.
<Astron. Astrophys. 490, 151 (2008)>
=2008A&A...490..151K 2008A&A...490..151K
ADC_Keywords: Models, evolutionary ; Clusters, globular ; Clusters, open
Keywords: Galaxy: globular clusters: general -
Galaxy: open clusters and associations: general -
galaxies: star clusters - galaxies: stellar content -
methods: numerical
Abstract:
To obtain an accurate description of broad-band photometric star
cluster evolution, certain effects should be accounted for. Energy
equipartition leads to mass segregation and the preferential loss of
low-mass stars, while stellar remnants severely influence cluster
mass-to-light ratios. Moreover, the stellar initial mass function and
cluster metallicity affect photometry as well. Due to the continuous
production of stellar remnants, their impact on cluster photometry is
strongest for old systems like globular clusters. This, in combination
with their low metallicities, evidence for mass segregation, and a
possibly deviating stellar initial mass function, makes globular
clusters interesting test cases for cluster models.
In this paper we describe cluster models that include the effects of
the preferential loss of low-mass stars, stellar remnants, choice of
initial mass function and metallicity. The photometric evolution of
clusters is predicted, and the results are applied to Galactic
globular clusters.
The cluster models presented in this paper represent an analytical
description of the evolution of the underlying stellar mass function
due to stellar evolution and dynamical cluster dissolution. Stellar
remnants are included by using initial-remnant mass relations, while
cluster photometry is computed from the Padova 1999 isochrones.
Description:
The SPACE star cluster models contain evolution data for clusters with
five different metallicities, two stellar initial mass functions,
with/without stellar remnants, with/without the preferential loss of
low-mass stars, and three different dissolution timescales. Models for
a wider range of parameters and for other observables can be made on
request. Please send me an e-mail if you are interested.
The model parameters of each data set are indicated by the filename,
KNNNN_NN.dat, in five directories, Z0004, Z004, Z008, Z02 and Z05.
The first number (0-4) indicates metallicity:
0 = Z=0.0004 ([Fe/H]=-1.7)
1 = Z=0.004 ([Fe/H]=-0.7)
2 = Z=0.008 ([Fe/H]=-0.4)
3 = Z=0.02 ([Fe/H]=0.0)
4 = Z=0.05 ([Fe/H]=0.4)
The second number (0-1) indicates IMF:
0 = Salpeter
1 = Kroupa
The third number (0-1) indicates whether stellar remnants are included:
0 = no remnants
1 = including remnants
The fourth number (0-1) indicates whether the preferential loss of
low-mass stars is included:
0 = no preferential loss of low-mass stars
1 = including the preferential loss of low-mass stars
The last two numbers (after the underscore) indicate the dissolution
timescale t_0 in Myr:
01 = t_0=1Myr
03 = t_0=3Myr
10 = t_0=10Myr
For example, file Z02/K3101_10.dat gives cluster evolution for a
metallicity Z=0.02 ([Fe/H]=0.0), a Kroupa IMF, no stellar remnants,
including the preferential loss of low-mass stars and a dissolution
timescale t0=10Myr.
In the files, columns are plotted for initial cluster masses between
102 and 107M☉
The absolute magnitudes of the Sun that have been used to convert
luminosities to magnitudes are:
[M{U,B,V,R,I,J,H,K}]=[5.61,5.48,4.83,4.42,4.08,3.64,3.32,3.28]
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 58 10 *Fitting values for a, b and c for the luminous
fractional cluster mass decrease due to stellar
evolution.
models.dat 60 3140 Summary of models
Z0004/* . 24 Model results for Z=0.0004 ([Fe/H]=-1.7)
Z004/* . 24 Model results for Z=0.004 ([Fe/H]=-0.7)
Z008/* . 24 Model results for Z=0.008 ([Fe/H]=-0.4)
Z02/* . 24 Model results for Z=0.02 ([Fe/H]=0.0)
Z05/* . 24 Model results for Z=0.05 ([Fe/H]=0.4)
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Note on table1.dat: constants determined by the IMF and metallicity of
the cluster as follows: log(qevlum)=(logt-aev)bev+cev.
Models use the qevlum(t) from the Padova 1999 isochrones at five
different metallicities for Salpeter (0.1M☉<ms<mmax,i) and
Kroupa (0.08M☉<ms<mmax,i) IMFs.
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See also:
J/A+A/321/29 : Star cluster evolution (Olofsson 1997)
J/A+A/392/1 : Stellar Populations simulated spectrophotometry (Schulz+, 2002)
J/A+A/462/107 : Simulations of metal-poor star clusters (Fagiolini+, 2007)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 A1 --- Type [LT] (L)uminous cluster mass (qevlum) or
(T)otal cluster mass (qevtot)
3- 8 F6.4 --- Z Initial metallicity
10- 16 F7.4 solMass Mass Initial maximum stellar mass (1)
18- 21 F4.2 --- aS Salpeter IMF aev parameter
23- 27 F5.3 --- bS Salpeter IMF bev parameter
29- 34 F6.3 --- cS Salpeter IMF cev parameter
36- 39 F4.2 --- aK Kroupa IMF aev parameter
41- 45 F5.3 --- bK Kroupa IMF bev parameter
47- 52 F6.3 --- cK Kroupa IMF cev parameter
54- 58 A5 --- Dir Name of the subdirectory containing the
model files (2)
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Note (1): Correspond to the maximum masses at the youngest isochrones
(logt=6.6).
Note (2): Files names as KABCD_NN.dat, with
----------------------------------------------------------------------
A = [0/4] where 0 = > Z=0.0004 ([Fe/H]=-1.7)
1 = > Z=0.004 ([Fe/H]=-0.7)
2 = > Z=0.008 ([Fe/H]=-0.4)
3 = > Z=0.02 ([Fe/H]=0.0)
4 = > Z=0.05 ([Fe/H]=0.4)
----------------------------------------------------------------------
B = [0/1] where 0 = Salpeter IMF or 1 = Kroupa IMF
----------------------------------------------------------------------
C = [0/1] where 0 = no remnants or 1 = including remnants
----------------------------------------------------------------------
D = [0/1] where 0 = no preferential loss of low-mass stars or
1 = including the preferential loss of low-mass stars
----------------------------------------------------------------------
NN = dissolution timescale where
01 = > t_0=1Myr, 03 = > t_0=3Myr and 10 = > t_0=10Myr
--------------------------------------------------------------------------------
Byte-by-byte Description of file: models.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.4 --- Z Initial metallicity
8 A1 --- IMF [SK] Salpeter or Kroupa IMF
10 A1 --- r [r-] "r" if model includes remnants
12 A1 --- L [L-] "L" if model includes preferential loss
of low-mass stars
14- 15 I2 Myr tD Dissolution timescale
17- 21 F5.3 [solMass] logMo Initial mass of the cluster (log scale)
23- 27 F5.3 [solMass] logMf Final mass of the cluster (at tf)
29- 34 F6.3 [yr] logtf Final time (log scale)
37- 41 A5 --- Dir Subdirectory name
43- 54 A12 --- File File name containing the model
56- 60 I5 --- Record Starting record number of the model in File
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Byte-by-byte Description of file (#): Z0004/* Z004/* Z008/* Z02/* Z05/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.6 [yr] logt Age
14- 22 F9.6 [solMass] logM0 Initial mass
27- 35 F9.6 [solMass] logM Present day mass
39- 48 F10.6 mag UMAG U-band absolute magnitude
52- 61 F10.6 mag BMAG B-band absolute magnitude
65- 74 F10.6 mag VMAG V-band absolute magnitude
78- 87 F10.6 mag RMAG R-band absolute magnitude
91-100 F10.6 mag IMAG I-band absolute magnitude
104-113 F10.6 mag JMAG J-band absolute magnitude
117-126 F10.6 mag HMAG H-band absolute magnitude
130-139 F10.6 mag KMAG K-band absolute magnitude
144-152 F9.6 mag V-I V-I colour index
157-165 F9.6 Sun M/L V-band mass-to-light ratio (in M☉/L☉)
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History:
Copied at http://www.astro.uu.nl/~kruijs/
(End) Patricia Vannier [CDS] 09-Oct-2008