J/AJ/170/85 Abund. & age of clusters from different SPS models (Asa'd+, 2025)
Semiempirical versus theoretical stellar population models: A comparison with
star clusters.
Asa'd R., Coelho P.R.T., John J.M., Chilingarian I.V., Bruzual G.,
Charlot S.
<Astron. J., 170, 85 (2025)>
=2025AJ....170...85A 2025AJ....170...85A
ADC_Keywords: Clusters, globular; Abundances, [Fe/H]; Models; Spectra, optical;
Populations, stellar
Keywords: Star clusters
Abstract:
Stellar population synthesis (SPS) models are a key tool for deriving
the age, metallicity, radial velocity, and reddening of star clusters
from their integrated spectra. Using a sample of 129 star clusters
with high-quality spectra, we analyze the uncertainties associated
with selecting an empirical versus a theoretical stellar spectral
library in the SPS models. We find that the fits from the different
models agree on the goodness-of-fit metrics and inferred reddening.
However, the derived age and metallicity can be affected by the choice
of the stellar library, with synthetic libraries tending to give lower
age and metallicity, especially for spectra with low signal-to-noise
ratio. Ages and reddening values from SSP-equivalent fits are
consistent with the multipopulation fits; however, SSP-equivalent
metallicities are affected by the coarse coverage of the SPS grid in
[Fe/H]. When comparing the spectral fitting results with the
literature, we find that (1) all models underestimate age for old and
metal-poor systems, and (2) on average, SPS models based on synthetic
stellar libraries better match the isochrone ages and metallicities
from high-resolution stellar spectroscopy.
Description:
We analyze 129 star clusters in the Milky Way, LMC, and SMC, using
data from SOAR and WAGGS.
A sample of 44 integrated stellar spectra was obtained in two
different observing runs with the Goodman Spectrograph on the Southern
Astrophysical Research (SOAR) 4.1m telescope in Chile. During the
first run (2011 December; Asa'd+2013, 2013PASP..125.1304A 2013PASP..125.1304A) 11 clusters
were observed in the long-slit low-resolution mode (1.03" wide slit;
R=1500; 3600<λ<6250Å). The second data set was observed with
the long-slit 1" wide slit; R=2100; 3710<λ<5430Å) in January
2018.
We also include 85 star clusters from the Wide Field Spectrograph
(WiFeS) Atlas of Galactic Globular cluster Spectra (WAGGS), a
comprehensive library of Milky Way and Local Group globular cluster
integrated spectra (Usher+2017, 2017MNRAS.468.3828U 2017MNRAS.468.3828U). WiFeS is a
dual-beam image-slicing integral field spectrograph offering a broad
25x38" field of view. The WiFeS spectra were acquired with the Siding
Spring Observatory 2.3m telescope in Australia.
We use the CBC20 (Coelho+2020, J/MNRAS/491/2025) stellar population
synthesis (SPS) models. These models were built using the
Bruzual & Charlot (2003MNRAS.344.1000B 2003MNRAS.344.1000B) GALAXEV code with the PARSEC
(Bressan+, 2012MNRAS.427..127B 2012MNRAS.427..127B; Chen+, 2015MNRAS.452.1068C 2015MNRAS.452.1068C) stellar
evolutionary tracks, assuming the Chabrier (2003ApJ...586L.133C 2003ApJ...586L.133C)
initial mass function. The CBC20 models are available for three
distinct stellar spectral libraries:
- The empirical MILES library (Sanchez-Blazquez+2006,
J/MNRAS/371/703; Cenarro+2007, J/MNRAS/374/664)
- The theoretical SynCoMiL library, computed by CBC20
- The theoretical Coelho14ext library, a version of the Coelho
(2014MNRAS.440.1027C 2014MNRAS.440.1027C) library extended to cover chemical abundances
considered by CBC20
We use the Starlight spectral fitting code
(Cid Fernandes+, 2005MNRAS.358..363C 2005MNRAS.358..363C) to infer the stellar population
parameters of each cluster in our sample for each set of SPS models
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
fig1.dat 310 129 Age and metallicity of the star clusters used in
this work (Data behind Figure 1)
fig2/* . 49 Spectral fits to SED in JPG format (Figure 2)
--------------------------------------------------------------------------------
See also:
VI/120 : High-resolution synthetic stellar library (Coelho+, 2005)
VI/157 : Full-spectrum fitting of simple stellar pop. (Goudfrooij+, 2021)
J/A+A/333/231 : O-M stars model atmospheres (Bessell+ 1998)
J/A+A/442/281 : Late-type giants BVRIJHKL & Teff calibration (Kucinskas+, 2005)
J/MNRAS/371/703 : MILES library of empirical spectra (Sanchez-Blazquez+, 2006)
J/MNRAS/374/664 : Stellar atmosph. parameters in MILES library (Cenarro+, 2007)
J/MNRAS/404/1639 : MILES base models & new line index system (Vazdekis+, 2010)
J/A+A/547/A108 : Comparative modelling of cool giants spect. (Lebzelter+, 2012)
J/MNRAS/435/952 : Lick indices for 51 stars (Sansom+, 2013)
J/MNRAS/491/2025 : Synthetic stellar spectra in SPS models (Coelho+, 2020)
J/MNRAS/499/2327 : Ages and abundances from spectral fitting (Goncalves+, 2020)
J/MNRAS/505/979 : Model spectra for identifying age spreads (Asa'd +, 2021)
J/A+A/672/A161 : Photometry of 101 Magellanic Cloud clusters (Milone+, 2023)
J/ApJ/824/5 : Chemical abundances in NGC 5024 (M53) (Boberg+, 2016)
J/A+A/583/A69 : NGC 6139 BV photometry (Bragaglia+, 2015)
J/A+A/505/139 : Abund. of red giants in 17 globular clusters (Carretta+, 2009)
J/A+A/505/117 : Abund. of red giants in 15 globular clusters (Carretta+, 2009)
J/A+A/533/A69 : Spectroscopy of 124 RGB stars in NGC 1851 (Carretta+, 2011)
J/A+A/557/A138 : Detailed chemical abund. in the GlC NGC 362 (Carretta+ 2013)
J/A+A/578/A116 : Abund. of red giant stars in NGC6093 (M80) (Carretta+, 2015)
J/A+A/600/A118 : Abund. of red giant stars in NGC6093 (M80) (Carretta+, 2017)
J/AJ/129/1607 : Equivalent widths of 4 RGB in NGC 7492 (Cohen+, 2005)
J/ApJ/834/105 : High-resolution GC abundances. II. (Colucci+, 2017)
J/AJ/136/1703 : Ridgelines of six intermediate-age SMC clusters (Glatt+, 2008)
J/A+A/345/430 : Abundances of 6 cool supergiants in NGC 330 (Hill, 1999)
J/MNRAS/377/300 : CT1 photometry in 6 SMC star clusters (Piatti+, 2007)
J/A+A/672/A161 : Photometry of 101 Magellanic Cloud clusters (Milone+, 2023)
J/AJ/116/2395 : BV photometry in five SMC clusters (Mighell+, 1998)
J/ApJS/161/304 : Star clusters in the MW and satellites (McLaughlin+, 2005)
J/AJ/136/375 : Chemical composition of LMC red giants (Mucciarelli+, 2008)
J/ApJ/717/277 : Chemical composition of old LMC clusters (Mucciarelli+, 2010)
J/AJ/139/878 : RGB stars in 8 LMC clusters (Sharma+, 2010)
J/MNRAS/300/665 : HST VI phot. of Six LMC Old Globular Clusters (Olsen+ 1998)
J/ApJ/297/582 : NGC 2213 BR photometry (Da Costa+, 1985)
J/ApJ/663/296 : UBV(RI)c phot. of NGC5139 subgiants (Villanova+, 2007)
J/MNRAS/450/815 : Red giants in NGC 5286 (Marino+, 2015)
J/ApJ/813/97 : M62 (NGC 6266) giant branch stars abundances (Lapenna+, 2015)
J/ApJ/834/105 : High-resolution GC abundances. II. (Colucci+, 2017)
J/ApJ/846/23 : High-res. spectra of 9 RGB stars in NGC6681 (O'Malley+, 2017)
J/MNRAS/434/358 : 4 Galactic globular clusters Fe line depths (Sakari+, 2013)
Byte-by-byte Description of file: fig1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Cluster Cluster name
10- 15 A6 --- Galaxy Host galaxy (1)
17- 21 A5 --- Tel Telescope (2)
23- 28 F6.3 [-] [Fe/H]Lit [-2.38/0.03]? Log Fe/H abundance from
literature
30- 62 A33 --- r_[Fe/H]Lit Reference for [Fe/H]Lit
64- 102 A39 --- bib[Fe/H]Lit Reference bibcode for [Fe/H]Lit
(column added by CDS)
104- 108 F5.2 Gyr Age-Lit [0.01/13.6]? Age from literature
110- 134 A25 --- r_Age-Lit Reference for Age-Lit
136- 154 A19 --- bibAge-Lit Reference bibcode for Age-Lit
(column added by CDS)
156- 160 F5.2 mag AV-CBC [-0.1/3.5] Mean extinction from
Coelho14ext library
162- 164 F3.1 mag e_AV-CBC [0.1/0.3]? Uncertainty in AV-Coelho14ext
library
166- 170 F5.2 Gyr Age-CBC [0.01/13.25] Mean age from Coelho14ext
library
172- 176 F5.3 Gyr e_Age-CBC [0.002/0.4] Uncertainty in Age-CBC
178- 182 F5.2 [-] [Fe/H]CBC [-1.92/-0.09] Mean [Fe/H] from
Coelho14ext library
184- 187 F4.2 [-] e_[Fe/H]CBC [0.02/0.5] Uncertainty in [Fe/H]CBC
189- 193 F5.2 mag AV-CBC-SSP [-0.1/3.32] Simple Stellar Population
(SSP) extinction from Coelho14ext
library
195- 200 F6.3 Gyr Age-CBC-SSP [0.01/14] Simple Stellar Population
(SSP) age from Coelho14ext library
202- 206 F5.2 [-] [Fe/H]CBC-SSP [-1.92/0.25] Simple Stellar Population
(SSP) [Fe/H] from Coelho14ext library
208- 212 F5.2 mag AV-M [-0.1/3.5] Mean extinction from MILES
library
214- 216 F3.1 mag e_AV-M [0.1/0.3]? Uncertainty in AV-M
218- 222 F5.2 Gyr Age-M [0/11.91] Mean age from MILES library
224- 228 F5.3 Gyr e_Age-M [0.002/0.4] Uncertainty in Age-M
230- 234 F5.2 [-] [Fe/H]M [-1.8/0.03] Mean [Fe/H] from MILES
library
236- 239 F4.2 [-] e_[Fe/H]M [0.02/0.5] Uncertainty in [Fe/H]M
241- 245 F5.2 mag AV-M-SSP [-0.1/3.22] Simple Stellar Population
(SSP) extinction from MILES library
247- 252 F6.3 Gyr Age-M-SSP [0.001/14] Simple Stellar Population
(SSP) age from MILES library
254- 258 F5.2 [-] [Fe/H]M-SSP [-1.92/0.25] Simple Stellar Population
(SSP) [Fe/H] from MILES library
260- 264 F5.2 mag AV-Sy [-0.1/3.5] Mean extinction from SynCoMiL
library
266- 268 F3.1 mag e_AV-Sy [0.1/0.3]? Uncertainty in AV-Sy
270- 274 F5.2 Gyr Age-Sy [0/13.54] Mean age from SynCoMiL library
276- 280 F5.3 Gyr e_Age-Sy [0.002/0.4] Uncertainty in Age-Sy
282- 286 F5.2 [-] [Fe/H]Sy [-1.89/0.03] Mean [Fe/H] from SynCoMiL
library
288- 291 F4.2 [-] e_[Fe/H]Sy [0.02/0.5] Uncertainty in [Fe/H]Sy
293- 297 F5.2 mag AV-Sy-SSP [-0.1/3.34] Simple Stellar Population
(SSP) extinction from SynCoMiL library
299- 304 F6.3 Gyr Age-Sy-SSP [0.01/14] Simple Stellar Population
(SSP) age from SynCoMiL library
306- 310 F5.2 [-] [Fe/H]Sy-SSP [-1.92/0.25] Simple Stellar Population
(SSP) [Fe/H] from SynCoMiL library
--------------------------------------------------------------------------------
Note (1): Host galaxies as follows:
MW = Milky Way (59 occurrences)
LMC = Large Magellanic Cloud (54 occurrences)
SMC = Small Magellanic Cloud (14 occurrences)
FORNAX = Fornax galaxy (2 occurrences)
Note (2): Telescopes as follows:
SOAR = The Southern Astrophysical Research (SOAR) 4.1m telescope in Chile
(44 occurrences)
WAGGS = the Wide Field Spectrograph (WiFeS) Atlas of Galactic Globular cluster
Spectra (WAGGS), acquired with the Siding Spring Observatory
2.3m telescope in Australia (85 occurrences)
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History:
From electronic version of the journal
License: CC-BY-4.0
(End) Prepared by [AAS], Robin Leichtnam [CDS] 29-May-2026