J/A+A/490/625 Abundances of NGC 6121 red giants (Marino+, 2008)
Spectroscopic and photometric evidence of two stellar populations in the
Galactic globular cluster NGC 6121 (M4).
Marino A.F., Villanova S., Piotto G., Milone A.P., Momany Y., Bedin L.R.,
Medling A.M.
<Astron. Astrophys. 490, 625 (2008)>
=2008A&A...490..625M 2008A&A...490..625M
ADC_Keywords: Clusters, globular ; Spectroscopy ; Abundances
Keywords: star: abundances - Galaxy: globular cluster: individual: NGC 6121
Abstract:
We present abundance analysis based on high resolution spectra of 105
isolated red giant branch (RGB) stars in the Galactic Globular Cluster
NGC 6121 (M4). The data have been collected with FLAMES+UVES, at the
ESO/VLT@UT2 telescope. Spectroscopic data were coupled with high
precision wide-field UBVI_C photometry from WFI@2.2m telescope and
infrared JHK photometry from 2MASS. We derived an average
[Fe/H]=-1.07±0.01, and an α enhancement of
[α/Fe]=+0.39±0.05dex (internal errors). We confirm the
presence of an extended Na-O anticorrelation, and find two distinct
groups of stars with significantly different Na and O content. We find
no evidence of a Mg-Al anticorrelation. By coupling our results with
previous studies on the CN band strength, we find that the CN strong
stars have higher Na and Al content and are more O depleted than the
CN weak ones. The two groups of Na-rich, CN-strong and Na-poor,
CN-weak stars populate two different regions along the RGB. In the U
vs. U-B color magnitude diagram the RGB spread is present from the
base of the RGB to the RGB-tip. Apparently, both spectroscopic and
photometric results imply the presence of two stellar populations
in M4. We briefly discuss the possible origin of these populations.
Description:
Table 8 contains the equatorial coordinates, the atmospheric
parameters measured on UVES spectra, UBVI_C photometry from WFI@2.2m
telescope and infrared JHK photometry from 2MASS for the analysed
stars.
Table 9 contains the measured chemical abundances.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table8.dat 88 105 Identification, equatorial coordinates,
atmospheric parameters and photometry
table9.dat 70 105 Chemical abundances
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See also:
J/ApJ/443/124 : Radial Velocities of Stars in M4 (Peterson+ 1995)
J/PAZh/22/847 : Identification and coordinates in M4 (Shokin+, 1996)
J/AJ/114/189 : M 4 CCD photometry (Alcaino+, 1997)
J/ApJS/120/265 : HST photometry of M4 (Ibata+, 1999)
J/AJ/127/2771 : HST proper-motions of M4 main-sequence stars (Richer+, 2004)
Byte-by-byte Description of file: table8.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star [5359/45895] Star identification number
7- 18 F12.8 deg RAdeg Right ascension in decimal degrees (J2000)
20- 31 F12.8 deg DEdeg Declination in decimal degrees (J2000)
33- 36 I4 K Teff Effective temperature
38- 41 F4.2 [cm/s2] logg Surface gravity
43- 46 F4.2 km/s Vt Microturbulent velocity
48- 52 F5.2 mag Umag ?=- Johnson U magnitude
54- 58 F5.2 mag Bmag ?=- Johnson B magnitude
60- 64 F5.2 mag Vmag ?=- Johnson V magnitude
66- 70 F5.2 mag Icmag ?=- Cousisn I magnitude
72- 76 F5.2 mag Jmag ?=- 2MASS J magnitude
78- 82 F5.2 mag Hmag ?=- 2MASS H magnitude
84- 88 F5.2 mag Kmag ?=- 2MASS K magnitude
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Byte-by-byte Description of file: table9.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Star [5359/45895] Star identification number
7- 11 F5.2 [Sun] [Fe/HI] Abundance ratio [Fe/HI]
13- 16 F4.2 [Sun] [O/Fe] ?=- Abundance ratio [O/Fe]
18- 22 F5.2 [Sun] [Na/Fe] Abundance ratio [Na/Fe]
24- 27 F4.2 [Sun] [Mg/Fe] Abundance ratio [Mg/Fe]
29- 33 F5.2 [Sun] [Al/Fe] ?=- Abundance ratio [Al/Fe]
35- 38 F4.2 [Sun] [Si/Fe] Abundance ratio [Si/Fe]
40- 43 F4.2 [Sun] [Ca/Fe] Abundance ratio [Ca/Fe]
45- 48 F4.2 [Sun] [Ti/FeI] Abundance ratio [Ti/FeI]
50- 53 F4.2 [Sun] [Ti/FeII] Abundance ratio [Ti/FeII]
55- 59 F5.2 [Sun] [Cr/Fe] Abundance ratio [Cr/Fe]
61- 65 F5.2 [Sun] [Ni/Fe] Abundance ratio [Ni/Fe]
67- 70 F4.2 [Sun] [Ba/FeII] ?=- Abundance ratio [Ba/FeII]
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Acknowledgements:
Anna Marino, anna.marino(at)unipd.it
(End) Anna Marino [Univ. Padova], Patricia Vannier [CDS] 02-Sep-2008