J/MNRAS/465/L39 Lindsay 1 spectroscopy for 34 targets (Hollyhead+, 2017)
Evidence for multiple populations in the intermediate-age cluster
Lindsay 1 in the SMC.
Hollyhead K., Kacharov N., Lardo C., Bastian N., Hilker M., Rejkuba M.,
Koch A., Grebel E.K., Georgiev I.
<Mon. Not. R. Astron. Soc., 465, L39-43 (2017)>
=2017MNRAS.465L..39H 2017MNRAS.465L..39H (SIMBAD/NED BibCode)
ADC_Keywords: Magellanic Clouds ; Associations, stellar
Keywords: Magellanic Clouds - galaxies: star clusters: individual: Lindsay 1
Abstract:
Lindsay 1 is an intermediate-age (~=8Gyr) massive cluster in the
Small Magellanic Cloud. Using VLT FORS2 spectra of 16 probable cluster
members on the lower red giant branch of the cluster, we measure CN
and CH band strengths (at ~=3883 and 4300Å, respectively), along
with carbon and nitrogen abundances and find that a sub-population of
stars has significant nitrogen enrichment. A lack of spread in carbon
abundances excludes evolutionary mixing as the source of this
enrichment, so we conclude that this is evidence of multiple
populations. Therefore, Lindsay 1 is the youngest cluster to show such
variations, implying that the process triggering the onset of multiple
populations must operate until at least redshift ∼1.
Description:
Our spectroscopic data for L1 was obtained in one observing run on
2015 October 06 at the European Southern Observatory (ESO) VLT
telescope based in Paranal, Chile using the MXU mode on the FORS2
spectrograph. We took five science exposures along with bias frames,
flat-fields and an arc lamp spectrum for wavelength calibration. Our
instrument configuration consisted of the GRIS 600B+22 grism with two
2kx4k E2V CCDs (15um pixel size), mosaic-ed, which are sensitive in
the blue range below 600nm, a requirement to accurately measure CN and
CH bands at ~=3883 and 4300Å, respectively. We centred the cluster
on the master chip (hereafter chip 1), while the slave chip (chip 2)
sampled outer regions of the cluster. The resolution of our spectra is
R=λ/{delata}λ~=800 and the spectral range covered by
most stars was ∼3300-6600Å.
Archival pre-imaging in the V and I bands was already available for
this cluster (ESO-programme: 082.B-0505(A) PI D. Geisler), which was
used to select targets, with an aim to sampling primarily the lower
RGB. 34 targets were chosen across chips 1 and 2, though the 1-arcsec
slit width prevented us from selecting targets in the central regions
of the cluster due to crowding. Where it was impossible to image a
primary target due to slit positioning, a random star was chosen in
its place.
Objects:
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RA (2000) DE Designation(s)
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00 03 54 -73 28.3 Lindsay 1 = ESO 28-8
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 132 34 Derived properties of each of the targets in
our study
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See also:
J/A+A/407/919 : UBVI and JHK photometry in Lindsay 1 (Alcaino+, 2003)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Star Star identification number
5- 8 A4 --- n_Star [abcd ] Note on Star (1)
10- 17 F8.6 deg RAdeg Right ascension (J2000)
19- 28 F10.6 deg DEdeg Declination (J2000)
30- 34 F5.2 mag Vmag V magnitude
36- 40 F5.2 mag Imag I magnitude
42- 46 F5.2 --- S3883 CSλ3883 index quantifying the strength
of the UV CN band
48- 51 F4.2 --- e_S3883 rms uncertainty on S3883
53- 57 F5.2 --- CH4300 CHλ4300 index quantifying the strength
of the G band of CH
59- 62 F4.2 --- e_CH4300 rms uncertainty on CH4300
64- 68 F5.2 --- [C/Fe] ?=- Abundance [C/Fe]
70- 73 F4.2 --- e_[C/Fe] ? rms uncertainty on [C/Fe]
75- 79 F5.2 --- [N/Fe] ?=- Abundance [N/Fe]
81- 84 F4.2 --- e_[N/Fe] ? rms uncertainty on
86- 90 F5.2 --- Fe5270 ?=- Fe5270 line index
92- 95 F4.2 --- e_Fe5270 ? rms uncertainty on Fe5270
97-101 F5.2 --- CaIIHK CaII (H+K) line index
103-107 F5.2 --- e_CaIIHK rms uncertainty on CaIIHK
109-112 I4 K Teff Effective temperature
114-116 I3 K e_Teff rms uncertainty on Teff
118-121 F4.2 [cm/s2] logg Surface gravity
123-126 F4.2 [cm/s2] e_logg rms uncertainty on logg
128-132 F5.1 km/s RV Radial velocity
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Note (1): Flag for stars excluded from the final results as they were unlikely
to be cluster members as follows:
a = stars were removed from inspection of the colour magnitude diagram,
b = indicates that the star was an outlier on the radial velocity plot
c = CaII (H+K) outliers
d = Fe5270 outliers
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 08-Jun-2018