J/MNRAS/504/4160 Results for 26 star clusters in the Mag. Clouds (Song+, 2021)
Dynamical masses and mass-to-light ratios of resolved massive star clusters.
II. Results for 26 star clusters in the Magellanic Clouds.
Song Y.-Y., Mateo M., Bailey J.I., Walker M.G., Roederer I.U.,
Olszewski E.W., Reiter M., Kremin A.
<Mon. Not. R. Astron. Soc. 504, 4160-4191 (2021)>
=2021MNRAS.504.4160S 2021MNRAS.504.4160S (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Photometry ; Abundances, [Fe/H] ;
Associations, stellar ; Optical
Keywords: techniques: radial velocities - techniques: spectroscopic -
stars: abundances - stars: kinematics and dynamics -
Magellanic Clouds - galaxies: star clusters: general
Abstract:
We present spectroscopy of individual stars in 26 Magellanic Cloud
(MC) star clusters with the aim of estimating dynamical masses and
V-band mass-to-light (M/LV) ratios over a wide range in age and
metallicity. We obtained 3137 high-resolution stellar spectra with
M2FS on the Magellan/Clay Telescope. Combined with 239 published
spectroscopic results of comparable quality, we produced a final
sample of 2787 stars with good quality spectra for kinematic analysis
in the target clusters. Line-of-sight velocities measured from these
spectra and stellar positions within each cluster were used in a
customized expectation-maximization (EM) technique to estimate cluster
membership probabilities. Using appropriate cluster structural
parameters and corresponding single-mass dynamical models, this
technique ultimately provides self-consistent total mass and M/LV
estimates for each cluster. Mean metallicities for the clusters were
also obtained and tied to a scale based on calcium IR triplet
metallicities. We present trends of the cluster M/LV values with
cluster age, mass, and metallicity, and find that our results run
about 40 per cent on average lower than the predictions of a set of
simple stellar population (SSP) models. Modified SSP models that
account for internal and external dynamical effects greatly improve
agreement with our results, as can models that adopt a strongly
bottom-light IMF. To the extent that dynamical evolution must occur, a
modified IMF is not required to match data and models. In contrast, a
bottom-heavy IMF is ruled out for our cluster sample as this would
lead to higher predicted M/LV values, significantly increasing the
discrepancy with our observations.
Description:
We selected cluster candidates from catalogues of MC clusters with
good-quality age and metallicity estimates and for which we could
expect to obtain samples of a few dozen stellar members. The table1.dat
lists the general properties of the star clusters in our final sample and
specifies all the literature sources used to select our spectroscopic
targets.
Secondly, the table2.dat lists the positions and structural parameters
of the clusters in our sample. These parameters are essential for the
background/sky subtraction processes (see Section 2.4.2) and to
establish the central velocity dispersions of the clusters (see
Section 4).
Finally, the spectral data used in this study were obtained with the
M2FS (Mateo et al. 2012, Proc. SPIE Conf. Ser. Vol. 8446, Ground-based
and Airborne Instrumentation for Astronomy IV. SPIE, Bellingham, p.
84464Y) on the Magellan/Clay Telescope over 26 nights during a
campaign lasting from 2016 September to 2019 March. The detailed
spectral configuration parameters are the same as described in the
paper (Song Y.-Y. et al. 2019MNRAS.490..385S 2019MNRAS.490..385S). After data reduction,
backgroung correction, the final sample table5.dat is produced
regrouping stars from previous known clusters in SMC and LMC galaxies.
Ensuring a high quality sample, membership probabilities of those
stars are computed with a expectation-maximization (EM) technique.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 71 26 General properties of star clusters
in our sample
table2.dat 108 26 Positions and structural parameters of star
clusters in our sample
table5.dat 159 3095 Final sample of all stars
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AJ/123/855 : Magellanic Clouds Photometric Survey: the SMC (Zaritsky+, 2002)
J/AJ/128/1606 : Magellanic Clouds Photometric Survey: the LMC (Zaritsky+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Galaxy Galaxy name host (Galaxy)
5- 13 A9 --- Cluster Cluster name host (Cluster)
15- 19 F5.2 mag Vmag Apparent magnitude in V band (Vap)
21- 24 F4.2 mag e_Vmag Mean error on Vmag (e_Vmag)
26- 29 F4.1 arcsec Aper Aperture radius used for measuring the
Vap magnitude (Aper)
31 I1 --- n_Vmag References on Vmag (Ref.) (1)
33- 37 F5.2 Gyr Age Age (Age)
39- 42 F4.2 Gyr e_Age Mean error on Age(e_Age)
44- 48 F5.2 mag (m-M)0 Gap between apparent and absolute magnitude
50- 53 F4.2 mag e_(m-M)0 Mean error on (m-M)0 (m-M0error)
55- 58 F4.2 mag Av Extinction in V band (Av)
60- 63 F4.2 mag e_Av Mean error on Av (e_Av)
65- 66 I2 --- n_Av Note on Av (Ref) (1)
68- 71 F4.1 --- [Fe/H] Abundance [Fe/H] ([Fe/H]) (2)
-------------------------------------------------------------------------------
Note (1): References as follows:
1 = Goudfrooij et al. 2006MNRAS.369..697G 2006MNRAS.369..697G
2 = Alcaino et al. 1978A&AS...34..431A 1978A&AS...34..431A)
3 = Bica et al. 1996ApJS..102...57B 1996ApJS..102...57B
4 = van den Bergh et al. 1981A&AS...46...79V 1981A&AS...46...79V
5 = Bernard 1975A&A...40..199B
6 = McLaughlin & van der Marel 2005ApJS..161..304M 2005ApJS..161..304M
7 = Glatt et al. 2008AJ....136.1703G 2008AJ....136.1703G
8 = Crowl et al. 2001AJ....122..220C 2001AJ....122..220C
9 = Milone et al. 2018MNRAS.477.2640M 2018MNRAS.477.2640M
10 = Goudfrooij et al. 2014ApJ...797...35G 2014ApJ...797...35G
11 = Alcaino et al. 2003A&A...400..917A 2003A&A...400..917A
12 = Grocholski et al. 2007AJ....134..680G 2007AJ....134..680G
13 = Wagner-Kaiser et al. 2017MNRAS.471.3347W 2017MNRAS.471.3347W
14 = Kerber, Santiago & Brocato 2007A&A...462..139K 2007A&A...462..139K
15 = Correnti et al. 2017MNRAS.467.3628C 2017MNRAS.467.3628C
16 = Martocchia et al. 2018MNRAS.477.4696M 2018MNRAS.477.4696M
17 = Correnti et al. 2014ApJ...793..121C 2014ApJ...793..121C
Note (2): The adopted [Fe/H] values were estimated from the age-metallicity
relations for the LMC and SMC clusters, respectively. For the LMC
clusters, we assumed that [Fe/H] = -0.4 if 0-2 Gyr, [Fe/H] = -0.5
if 2-4 Gyr, [Fe/H] = -1.7 for NGC 1466 and NGC 2257, and [Fe/H] = -2.0
for NGC 1841; while for the SMC clusters, we assumed that [Fe/H] = -0.9
if 0-4 Gyr, and [Fe/H] = -1.3 if 6-9 Gyr.
These age-metallicity relations were averaged from multiple papers
that fitted cluster CMDs with the Padova isochrones in these
references as follows:
1 = Grocholski et al. 2007AJ....134..680G 2007AJ....134..680G for LMC
2 = Kerber et al. 2007A&A...462..139K 2007A&A...462..139K for LMC
3 = Milone et al. 2009A&A...497..755M 2009A&A...497..755M for LMC
4 = Goudfrooij et al. 2014ApJ...797...35G 2014ApJ...797...35G for LMC
5 = Milone et al. 2018MNRAS.477.2640M 2018MNRAS.477.2640M for LMC
6 = Crowl et al. 2001AJ....122..220C 2001AJ....122..220C for SMC
7 = Glatt et al. 2008AJ....136.1703G 2008AJ....136.1703G for SMC
8 = Goudfrooij et al. 2014ApJ...797...35G 2014ApJ...797...35G for SMC
9 = Milone et al. 2018MNRAS.477.2640M 2018MNRAS.477.2640M for SMC
The final cluster metallicities from this study are listed in Table 6.
SL 663 has no V-band aperture photometry in the literature. We have
adopted the best-fitting V-band extinction-corrected central surface
brightness from McLaughlin & van der Marel 2005ApJS..161..304M 2005ApJS..161..304M.
The value listed here is in unit of mag/arcsec2.
-------------------------------------------------------------------------------
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Galaxy Galaxy name host (Galaxy)
5- 13 A9 --- Cluster Cluster name host (Cluster)
15- 16 I2 h RAh Right ascension (J2000)
18- 19 I2 min RAm Right ascension (J2000)
21- 25 F5.2 s RAs Right ascension (J2000)
27 A1 --- DE- Sign of declination (J2000)
28- 29 I2 deg DEd Declination (J2000)
31- 32 I2 arcmin DEm Declination (J2000)
34- 37 F4.1 arcsec DEs Declination (J2000)
39- 42 F4.2 --- cK62 Concentration parameter(1)
44- 47 F4.2 --- E_cK62 Upper limit of cK62 (E_cK62)
49- 52 F4.2 --- e_cK62 Lower limit of cK62 (e_cK62)
54- 58 F5.2 arcsec r0K62 King radius (r0,K62) (2)
60- 64 F5.2 arcsec E_r0K62 Upper limit of r0,K62 (E_r0,K62)
66- 69 F4.2 arcsec e_r0K62 Lower limit of r0,K62 (e_r0,K62)
71- 73 A3 --- n_r0K62 References of r0,K62 (3)
75- 78 F4.2 --- cK66 Concentration parameter (cK66) (1)
80- 83 F4.2 --- E_cK66 Upper limit of cK66 (E_cK66)
85- 88 F4.2 --- e_cK66 Lower limit of cK66 (e_cK66)
90- 94 F5.2 arcsec r0K66 King radius (r0,K66) (4)
96-100 F5.2 arcsec E_r0K66 Upper limit of r0,K66 (E_r0,K66)
102-106 F5.2 arcsec e_r0K66 Lower limit of r0,K66 (e_r0,K66)
108 I1 --- n_r0K66 ? References of r0,K66 (3)
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Note (1): Concentration parameter c = log10(rt/r0), where r0 and rt are the
King radius and truncation radius, respectively.
Note (2): Originate from King 1962AJ.....67..471K 1962AJ.....67..471K
Note (3): References as follows:
1 = Glatt et al. 2009AJ....138.1403G 2009AJ....138.1403G
2 = Goudfrooij et al. 2014ApJ...797...35G 2014ApJ...797...35G
3 = Goudfrooij et al. 2011ApJ...737....3G 2011ApJ...737....3G
4 = Goudfrooij et al. 2009AJ....137.4988G 2009AJ....137.4988G
5 = Correnti et al. 2017MNRAS.467.3628C 2017MNRAS.467.3628C
6 = Correnti et al. 2014ApJ...793..121C 2014ApJ...793..121C
7 = McLaughlin & van der Marel 2005ApJS..161..304M 2005ApJS..161..304M
8 = Fischer et al. 1992AJ....104.1086F 1992AJ....104.1086F
Note (4): Originate from King 1966AJ.....71...64K 1966AJ.....71...64K
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Galaxy Galaxy name host (Galaxy)
5- 13 A9 --- Cluster Cluster name host (Cluster)
15- 26 A12 --- ID Name ID (ID)
28- 36 F9.6 deg RAdeg Right ascension expressed (J2000)
38- 47 F10.6 deg DEdeg Declination expressed (J2000)
49- 53 F5.2 mag Gmag ? Apparent magnitude in G band (G)
55- 59 F5.2 mag BP-RP ? Apparent magnitude gap (GBP-GRP)
61- 64 I4 K Teff ? Effective temperature (Teff)
66- 84 I19 --- GaiaDR2 ? GaiaDR2 ID (GaiaDR2_ID)
86- 89 F4.1 --- S/N ? Signal to noise ratio (S/N) (1)
91- 96 F6.2 km/s Vlos LOS velocity (vlos)
98-103 F6.2 km/s e_Vlos Mean error on Vlos (e_Vlos)
105-108 F4.2 [cm/s2] logg ? Log (Surface gravity) (log(g))
110-113 F4.2 [cm/s2] e_logg ? Mean error on log(g) (e_log)
115-119 F5.2 --- [Fe/H] ? Abundance [Fe/H] ([Fe/H])
121-124 F4.2 --- e_[Fe/H] ? Mean error on [Fe/H] (e_[Fe/H])
126-130 F5.2 --- PM The preliminary membership probability (PM)
132-136 F5.2 --- P'M The preliminary membership probability where
significant contamination by a single
unflagged non-member appears to be present
(P'M)
138-144 I7 --- Flag Seven digits flags (Flag) (2)
146-159 A14 --- Refs Reference sources (Source) (3)
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Note (1): Median S/N per pixel of M2FS spectrum.
Note (2): Details about how these flags are set can be found in Section 3.4.1,
Section 3.4.2, Section 3.4.3, Section 4.1, and Section 4.2.
These seven-digit flags denote with a '1' as follows:
Digit 1 = Rejection due to poor skew/kurtosis values in
the Bayesian spectra fits
Digit 2 = Excessive velocity error
Digit 3 = Carbon star
Digit 4 = Foreground dwarf
Digit 5 = Member of a non-cluster/non-MC population
Digit 6 = Has a large colour offset for Teff determination
Digit 7 = Likely metallicity non-member
Note (3): Sources for the LOS velocities. M2FS denotes this work.
Other codes are listed as follows:
Fi92 = Fischer et al. 1992AJ....104.1086F 1992AJ....104.1086F
Fi93 = Fischer et al. 1993AJ....105..938F 1993AJ....105..938F
Ma13 = Mackey et al. 2013ApJ...762...65M 2013ApJ...762...65M
Mu08 = Mucciarelli et al. 2008AJ....136..375M 2008AJ....136..375M
Mu10 = Mucciarelli et al. 2010ApJ...717..277M 2010ApJ...717..277M
Mu14 = Mucciarelli et al. 2014ApJ...793L...6M 2014ApJ...793L...6M
Pa20 = Patrick et al. 2020A&A...635A..29P 2020A&A...635A..29P
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 14-May-2024