J/A+A/507/1409 Models for dynamically dissolving star clusters (Kruijssen, 2009)
The evolution of the stellar mass function in star clusters.
Kruijssen J.M.D.
<Astron. Astrophys. 507, 1409 (2009)>
=2009A&A...507.1409K 2009A&A...507.1409K
ADC_Keywords: Models, evolutionary ; Associations, stellar
Keywords: stellar dynamics - stars: kinematics -
Galaxy: globular clusters: general -
Galaxy: open clusters and associations: general -
galaxies: star clusters - galaxies: stellar content -
Abstract:
The dynamical escape of stars from star clusters affects the shape of
the stellar mass function (MF) in these clusters, because the escape
probability of a star depends on its mass. This is found in N-body
simulations and has been approximated in analytical cluster models by
fitting the evolution of the MF. Both approaches are naturally
restricted to the set of boundary conditions for which the simulations
were performed. The objective of this paper is to provide and to apply
a simple physical model for the evolution of the MF in star clusters
for a large range of the parameter space. It should also offer a new
perspective on the results from N-body simulations.
A simple, physically self-contained model for the evolution of the
stellar MF in star clusters is derived from the basic principles of
two-body encounters and energy considerations. It is independent of
the adopted mass loss rate or initial mass function (IMF), and
contains stellar evolution, stellar remnant retention, dynamical
dissolution in a tidal field, and mass segregation.
The evolution of the MF affects the integrated properties of star
clusters. This data catalogue provides such quantities and also lists
the evolution of the MF slope in certain mass ranges.
Description:
Evolutionary models for dissolving star clusters, computed with
SPACEv3.0 (also see http://www.astro.uu.nl/~kruijs). The SPACE star
cluster models contain evolution data for clusters with seven
different metallicities. The set of data provided here contains models
for five different dissolution timescales, three sets of remnant kick
velocities, and two King profile parameters. 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 models are calculated for a Kroupa (2001MNRAS.322..231K 2001MNRAS.322..231K) IMF,
using the isochrones from the Padova group (Marigo et al.,
2008A&A...482..883M 2008A&A...482..883M). The initial-final mass relations for stellar
remnants and other details are listed in the main paper.
The model parameters of each data set are summarised in the filenames
of the data (K09_NNNN.dat). For example, a filename K09_5201.dat gives
the cluster evolution for a metallicity Z=0.02 ([Fe/H]=0.0), a
dissolution timescale t0=3Myr, kick velocities that are 0.5 times
the standard values {4,100,80} km/s for white dwarfs, neutron stars,
and black holes (so {2,50,40} km/s), and a King profile parameter
W0=7.
After the filename header "K09_", the meaning of the numbers is as follows.
The first number (0-6) indicates the metallicity:
0 - Z = 0.0001 ([Fe/H]=-2.3)
1 - Z = 0.0004 ([Fe/H]=-1.7)
2 - Z = 0.001 ([Fe/H]=-1.3)
3 - Z = 0.004 ([Fe/H]=-0.7)
4 - Z = 0.008 ([Fe/H]=-0.4)
5 - Z = 0.02 ([Fe/H]=0.0)
6 - Z = 0.03 ([Fe/H]=0.18)
The second number (0-4) indicates the dissolution timescale parameter t_0:
0 - t0= 0.3Myr (recommended for M51, Antennae)
1 - t0= 1Myr (recommended for the Galactic globular cluster system,
though individual t_0 values show substantial scatter)
2 - t0= 3Myr (recommended for the solar neighbourhood, M33)
3 - t0= 10Myr (recommended for gas-poor spiral galaxies)
4 - t0= 30Myr (recommended for the SMC, LMC)
The third number (0-2) indicates the factor by which the standard kick
velocities {4,100,80} km/s for white dwarfs, neutron stars, and black holes
(WDs, NSs, BHs) are multiplied:
0 - 0.5 (i.e. {2,50,40} km/s for WDs, NSs, and BHs)
1 - 1 (i.e. {4,100,80} km/s for WDs, NSs, and BHs) - RECOMMENDED
2 - 2.5 (i.e. {10,250,200} km/s for WDs, NSs, and BHs)
The fourth number (0-1) indicates the King profile parameter W_0:
0 - W0= 5 (recommended for open clusters)
1 - W0= 7 (recommended for globular clusters)
The models are computed for initial cluster masses between 102 and
107M☉. If a certain initial mass does not appear in the list,
this means that it was disrupted within 10Myr.
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
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ReadMe 80 . This file
models.dat 65 4242 Summary of models
models/* . 210 Model results
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See also:
J/A+A/490/151 : Photometric evolution of star cluster models (Kruijssen+ 2008)
http://www.astro.uu.nl/~kruijs : Models Website
Byte-by-byte Description of file: models.dat
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Bytes Format Units Label Explanations
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1- 6 F6.4 --- Z Initial metallicity (1)
8- 11 F4.1 Myr t0 Dissolution time (2)
13- 15 F3.1 --- Kick Kick velocity multiplier (3)
17 I1 --- W0 King profile parameter (4)
19- 23 F5.3 [solMass] logMo Initial mass
25- 29 F5.3 [solMass] logMf Final mass
31- 36 F6.3 [yr] logtf Final time
38- 43 A6 --- Dir Subdirectory name
46- 60 A15 --- File File name containing the model
62- 65 I4 --- Record Starting record number of the model in File
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Note (1): Metallicities are 0.0001, 0.0004, 0.001, 0.004, 0.008, 0.02 and 0.03.
Note (2): Dissolution timescale parameters are 0.3, 1, 3, 10 and 30Myr.
Note (3): Kick velocity multipliers are 0.5, 1 and 2.5.
Note (4): King profile parameters are 5 and 7.
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Byte-by-byte Description of file: models/*
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Bytes Format Units Label Explanations
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1- 10 F10.6 [yr] logt Age
14- 23 F10.6 [solMass] logMi Initial mass
27- 36 F10.6 [solMass] logM Present day mass
40- 49 F10.6 --- fracStar Mass fraction in stars
53- 62 F10.6 --- fracRemn Mass fraction in stellar remnants
66- 75 F10.6 --- fracWDs Mass fraction in white dwarfs
79- 88 F10.6 --- fracNSs Mass fraction in neutron stars
92-101 F10.6 --- fracBHs Mass fraction in black holes
105-114 F10.6 mag UMAG U-band absolute magnitude (1)
118-127 F10.6 mag BMAG B-band absolute magnitude (1)
131-140 F10.6 mag VMAG V-band absolute magnitude (1)
144-153 F10.6 mag RMAG R-band absolute magnitude (1)
157-166 F10.6 mag IMAG I-band absolute magnitude (1)
170-179 F10.6 mag JMAG J-band absolute magnitude (1)
183-192 F10.6 mag HMAG H-band absolute magnitude (1)
196-205 F10.6 mag KMAG K-band absolute magnitude (1)
209-218 F10.6 Sun M/L V-band mass-to-light ratio
(in solMass/solLum)
222-231 F10.6 --- slope1 ? Fitted MF slope in range 0.1-0.5M☉
232 A1 --- n_slope1 [in] i for -Infinity, n for NaN
235-244 F10.6 --- slope2 ? Fitted MF slope in range 0.3-0.8M☉
245 A1 --- n_slope2 [in] i for -Infinity, n for NaN
248-257 F10.6 --- slope3 ? Fitted MF slope in range 0.3*mmax-0.8*mmax
258 A1 --- n_slope3 [in] i for -Infinity, n for NaN
261-270 F10.6 solMass mmax Maximum stellar mass
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Note (1): in Vega system.
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Acknowledgements:
Diederik Kruijssen, kruijssen(at)astro.uu.nl
(End) D. Kruijssen [Utrecht, The Netherlands], P. Vannier [CDS] 02-Nov-2009