J/A+A/602/A112 M31 PHAT star clusters (de Meulenaer+, 2017)
Deriving physical parameters of unresolved star clusters.
V. M31 PHAT star clusters.
de Meulenaer P., Stonkute R., Vansevicius V.
<Astron. Astrophys. 602, A112 (2017)>
=2017A&A...602A.112D 2017A&A...602A.112D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Associations, stellar ; Abundances, [Fe/H]
Keywords: galaxies: individual: M31 - galaxies: star clusters: general
Abstract:
This study is the fifth of a series that investigates the degeneracy
and stochasticity problems present in the determination of physical
parameters such as age, mass, extinction, and metallicity of partially
resolved or unresolved star cluster populations in external galaxies
when using HST broad-band photometry. In this work we aim to derive
parameters of star clusters using models with fixed and free
metallicity based on the HST WFC3+ACS photometric system. The method
is applied to derive parameters of a subsample of 1363 star clusters
in the Andromeda galaxy observed with the HST. Following Paper III (de
Meulenaer et al., 2015A&A...574A..66D 2015A&A...574A..66D), we derive the star cluster
parameters using a large grid of stochastic models that are compared
to the six observed integrated broad-band WFC3+ACS magnitudes of star
clusters. We show that the age, mass, and extinction of the M31 star
clusters, derived assuming fixed solar metallicity, are in agreement
with previous studies. We also demonstrate the ability of the WFC3+ACS
photometric system to derive metallicity of star clusters older than
∼1 Gyr. We show that the metallicity derived using broad-band
photometry of 36 massive M31 star clusters is in good agreement with
the metallicity derived using spectroscopy.
Description:
We first selected a sample of 402 clusters from the catalog of Johnson
et al. (2012, Cat. J/ApJ/752/95) with available magnitudes in all
photometric filters. Then from this sample we selected two cluster
groups.
In cluster group 1 (65 objects), the photometric accuracy of objects
is <0.15mag in F275W and F336W, <0.1mag in F475W and F814W, and
<0.2mag in F110W and F160W. In cluster group 2 (138 objects), the
photometric accuracy in each filter is <0.5mag. In total, we analyze
203 clusters.
We derived the parameters of both cluster groups 1 and 2 by firstly
fixing the metallicity of all clusters to the solar value, and a
second time by allowing a large range of metallicities in the model
grid with 13 values of [M=H]=+0.2 to -2.2, in steps of 0.2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 1363 Sample
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See also:
J/ApJ/752/95 : PHAT stellar cluster survey. I. Year 1 (Johnson+, 2012)
J/ApJ/802/127 : PHAT stellar cluster survey. II. AP catalog (Johnson+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- APID Cluster identification number in PHAT
(Johnson et al., 2015, Cat. J/ApJ/802/127)
6- 15 F10.6 deg RAdeg Right ascension (J2000)
16- 25 F10.6 deg DEdeg Declination (J2000)
26- 31 F6.2 mag F475W PHAT magnitude in the passband F475W
32- 37 F6.2 [yr] logTs Age, log10(t/yr), solar metallicity
38- 43 F6.2 [Msun] logMs Mass, log10(M/M☉), solar metallicity
44- 49 F6.2 mag E(B-V)s Colour excess, E(B-V), solar metallicity
50- 55 F6.2 [yr] logT ? Age, log10(t/yr), free metallicity
56- 61 F6.2 [Msun] logM ? Mass, log10(M/M☉), free metallicity
62- 67 F6.2 mag E(B-V) ? Colour excess, E(B-V), free metallicity
68- 73 F6.1 --- [M/H] ? Metallicity, [M/H]
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Acknowledgements:
Vladas Vansevicius, vladas.vansevicius(at)ff.vu.lt
References:
de Meulenaer et al., Paper I 2013A&A...550A..20D 2013A&A...550A..20D
de Meulenaer et al., Paper II 2014A&A...569A...4D 2014A&A...569A...4D
de Meulenaer et al., Paper III 2015A&A...574A..66D 2015A&A...574A..66D
de Meulenaer et al., Paper IV 2015A&A...581A.111D 2015A&A...581A.111D
(End) Patricia Vannier [CDS] 15-May-2017