J/MNRAS/499/1200 Leveraging HST with MUSE II (Martocchia+, 2020)
Leveraging HST with MUSE
II. Na-abundance variations in intermediate age star clusters.
Martocchia S., Kamann S., Saracino S., Usher C., Bastian N., Rejkuba M.,
Latour M., Lardo C., Cabrera-Ziri I., Dreizler S., Kacharov N.,
Kozhurina-Platais V., Larsen S., Mancino S., Platais I., Salaris M.
<Mon. Not. R. Astron. Soc., 499, 1200-1211 (2020)>
=2020MNRAS.499.1200M 2020MNRAS.499.1200M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Magellanic Clouds ; Abundances, [Fe/H] ;
Colors ; Radial velocities ; Photometry, HST ; Spectra, optical
Keywords: stars: abundances - galaxies: individual: SMC -
galaxies: star clusters: NGC 416 -
galaxies: star clusters: Lindsay 1 -
Hertzprung-Russell and colour-magnitude diagrams -
techniques: spectroscopy - techniques: photometry
Abstract:
Ancient (>10Gyr) globular clusters (GCs) show chemical abundance
variations in the form of patterns among certain elements, e.g. N
correlates with Na and anticorrelates with O. Recently, N abundance
spreads have also been observed in massive star clusters that are
significantly younger than old GCs, down to an age of ∼2Gyr. However,
so far N has been the only element found to vary in such young
objects. We report here the presence of Na abundance variations in the
intermediate age massive star clusters NGC 416 (∼6.5Gyr old) and
Lindsay 1 (∼7.5Gyr old) in the Small Magellanic Cloud, by combining
Hubble Space Telescope (HST) and European Southern Observatory Very
Large Telescope MUSE observations. Using HST photometry, we were able
to construct 'chromosome maps' and separate subpopulations with
different N content, in the red giant branch of each cluster. MUSE
spectra of individual stars belonging to each population were
combined, resulting in high signal-to-noise spectra representative of
each population, which were compared to search for mean differences in
Na. We find a mean abundance variation of
Δ[Na/Fe]=0.18±0.04dex for NGC 416 and
Δ[Na/Fe]=0.24±0.05dex for Lindsay 1. In both clusters, we find
that the population that is enhanced in N is also enhanced in Na,
which is the same pattern to the one observed in ancient GCs.
Furthermore, we detect a bimodal distribution of core-helium-burning
red clump (RC) giants in the UV colour-magnitude diagram of NGC 416. A
comparison of the stacked MUSE spectra of the two RCs shows the same
mean Na abundance difference between the two populations. The results
reported in this work are a crucial hint that star clusters of a large
age range share the same origin: they are the same types of objects,
but only separated in age.
Description:
The photometric observations of NGC 416 and Lindsay 1 from the HST are
composed of both proprietary and archival data. The F343N and F438W
filters are from the HST/WFC3/UVIS survey of MC star clusters
(proposal GO-14069, P.I. N. Bastian). These observations have been
recently complemented with new data in the UV filter F275W, from the
proposal GO-15630 (PI: N. Bastian). ACS/WFC observations in F555W and
F814W filters were added for our analysis (GO-10396, PI. J.
Gallagher). See details on Table 1 of the article.
MUSE observations of NGC 416 and Lindsay 1 were obtained between 2019
October and December in the course of program 0104.D-0257 (PI:
Kamann), using the wide field mode of the instrument without adaptive
optics support. Each observation consisted of four exposures and
derotator offsets of 90° were applied in between exposures. See
details on Table 2 of the article.
Objects:
------------------------------------------------------------------
RA (ICRS) DE Designation(s)
------------------------------------------------------------------
01 07 59.00 -72 21 19.9 NGC 416 = Cl Kron 59 = Cl Lindsay 83
00 03 54.00 -73 28 17.9 Lindsay 1 = Cl Lindsay 1 = ESO 28-8
------------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 97 145 Photometric and spectroscopic information of the
RGB MUSE targets used for the analysis of
NGC 416
table4.dat 140 25 Photometric and spectroscopic information of the
RGB MUSE targets used for the analysis of
Lindsay 1
table5.dat 106 149 Photometric and spectroscopic information of the
RC MUSE targets used for the analysis of NGC 416
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/145] Internal star identifier
5- 14 F10.7 deg RAdeg Right ascension (J2000)
16- 26 F11.7 deg DEdeg Declination (J2000)
28- 37 F10.7 mag DX F275W-F814W colour ΔF275W,F814W
39- 48 F10.7 mag DY (F275W-F343N)-(F343N-F438W) colour
ΔF275W,F343N,F438W
50- 55 F6.3 --- SNR Signal to noise ratio
57- 67 F11.8 [-] [Fe/H] Fe/H abundance ratio
69- 78 F10.8 [-] e_[Fe/H] Error on [Fe/H]
80- 86 F7.3 km/s RV Radial velocity
88- 92 F5.3 km/s e_RV Error on RV
94 I1 --- Nexp Number of spectra available
96- 97 A2 --- Pop Population tag based on the Chromosome map
selection (1)
--------------------------------------------------------------------------------
Note (1): Population as follows:
P1 = First generation (76/145)
P2 = Second generation, star enriched in N and Na but depleted in C and O
(69/145)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- ID [1/25] Internal star identifier
4- 12 F9.7 deg RAdeg Right ascension (J2000)
14- 24 F11.7 deg DEdeg Declination (J2000)
26- 46 F21.18 mag DX F275W-F814W colour ΔF275W,F814W
48- 68 F21.18 mag DY (F275W-F343N)-(F343N-F438W) colour
ΔF275W,F343N,F438W
70- 87 F18.15 --- SNR Signal to noise ratio
89- 99 F11.8 [-] [Fe/H] Fe/H abundance ratio
101- 110 F10.8 [-] e_[Fe/H] Error on [Fe/H]
112- 123 F12.8 km/s RV Radial velocity
125- 135 F11.8 km/s e_RV Error on RV
137 I1 --- Nexp Number of spectra available
139- 140 A2 --- Pop Population tag based on the Chromosome map
selection (1)
--------------------------------------------------------------------------------
Note (1): Population as follows:
P1 = First generation (19/25)
P2 = Second generation, star enriched in N and Na but depleted in C and O
(6/25)
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- ID [1/149] Internal star identifier
5- 14 F10.7 deg RAdeg Right ascension (J2000)
16- 26 F11.7 deg DEdeg Declination (J2000)
28- 37 F10.7 mag DX F275W-F814W colour ΔF275W,F814W
39- 48 F10.7 mag DY (F275W-F343N)-(F343N-F438W) colour
ΔF275W,F343N,F438W
50- 54 F5.2 --- SNR Signal to noise ratio
56- 66 F11.8 [-] [Fe/H] Fe/H abundance ratio
68- 77 F10.8 [-] e_[Fe/H] Error on [Fe/H]
79- 90 F12.8 km/s RV Radial velocity
92- 101 F10.8 km/s e_RV Error on RV
103 I1 --- Nexp Number of spectra available
105- 106 A2 --- Pop Population tag based on the Chromosome map
selection (1)
--------------------------------------------------------------------------------
Note (1): Population as follows:
P1 = First generation (90/149)
P2 = Second generation, star enriched in N and Na but depleted in C and O
(59/149)
--------------------------------------------------------------------------------
History:
From electronic version of the journal
References:
Saracino et al., Paper I 2020MNRAS.498.4472S 2020MNRAS.498.4472S
(End) Ana Fiallos [CDS] 17-Aug-2023