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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 (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), 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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 73 1363 Sample
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
Bytes Format Units Label Explanations
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]
Acknowledgements: Vladas Vansevicius, vladas.vansevicius(at) References: de Meulenaer et al., Paper I 2013A&A...550A..20D de Meulenaer et al., Paper II 2014A&A...569A...4D de Meulenaer et al., Paper III 2015A&A...574A..66D de Meulenaer et al., Paper IV 2015A&A...581A.111D
(End) Patricia Vannier [CDS] 15-May-2017
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