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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
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:
FileName Lrecl Records Explanations
ReadMe 80 . This file table8.dat 88 105 Identification, equatorial coordinates, atmospheric parameters and photometry table9.dat 70 105 Chemical abundances
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
Bytes Format Units Label Explanations
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
Byte-by-byte Description of file: table9.dat
Bytes Format Units Label Explanations
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]
Acknowledgements: Anna Marino, anna.marino(at)unipd.it
(End) Anna Marino [Univ. Padova], Patricia Vannier [CDS] 02-Sep-2008
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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