2008A&A...490..625M

Query : 2008A&A...490..625M

2008A&A...490..625M - Astronomy and Astrophysics, volume 490625-640 (2008/11-1)

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. and MEDLING A.M.

Abstract (from CDS):

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). Our aim is to study its star population in the context of the multi-population phenomenon recently discovered to affect some Globular Clusters. The data have been collected with FLAMES+UVES, the multi-fiber high resolution facility at the ESO/VLTT2 telescope. Analysis was performed under LTE approximation for the following elements: O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Ba, and NLTE corrections were applied to those (Na, Mg) strongly affected by departure from LTE. Spectroscopic data were coupled with high-precision wide-field UBVIC photometry from WFI.2 m telescope and infrared JHK photometry from 2MASS. We derived an average [Fe/H]=-1.07±0.01 (internal error), and an α enhancement of [α/Fe]=+0.39±0.05dex (internal error). 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. The Na-rich group defines a narrow sequence on the red side of the RGB, while the Na-poor sample populate a bluer, more spread portion of 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.

Abstract Copyright: ∼

Journal keyword(s): Galaxy: globular clusters: individual: NGC 6121 - stars: abundances

VizieR on-line data: <Available at CDS (J/A+A/490/625): table8.dat table9.dat>

Nomenclature: Table 8: Cl* NGC 6121 MVP NNNNN N=105 among (Nos 5359-48895).

Simbad objects: 121

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Number of rows : 121
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 NGC 104 GlC 00 24 05.359 -72 04 53.20     4.09     ~ 4158 0
2 NGC 1851 GlC 05 14 06.76 -40 02 47.6           ~ 1529 0
3 NGC 2808 GlC 09 12 03.10 -64 51 48.6           ~ 1540 0
4 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3677 0
5 M 3 GlC 13 42 11.62 +28 22 38.2     6.39     ~ 2593 0
6 M 5 GlC 15 18 33.22 +02 04 51.7     5.95     ~ 2095 0
7 NGC 6121 474 RG* 16 23 13.9484472072 -26 33 24.539562864 14.89 13.556 12.055   10.286 ~ 33 0
8 2MASS J16231442-2636055 RG* 16 23 14.4181955592 -26 36 05.547999564 14.64 12.73 10.88 9.80 9.04 ~ 46 0
9 Cl* NGC 6121 LEE 2422 RG* 16 23 14.5990497360 -26 30 46.990708560 15.05 13.901 12.482   10.813 ~ 22 0
10 NGC 6121 471 RG* 16 23 16.5623721744 -26 32 09.733929072 14.79 13.236 11.661   9.896 ~ 37 0
11 NGC 6121 424 RG* 16 23 16.9017005856 -26 29 47.955475500 15.28 14.389 13.100   11.559 ~ 22 0
12 Cl* NGC 6121 MVP 32151 RG* 16 23 20.9015267688 -26 31 36.885552960 15.41 14.59 13.307   11.722 ~ 9 0
13 Cl* NGC 6121 MVP 32121 RG* 16 23 21.1518974424 -26 31 37.769578860 15.49 14.67 13.403   11.816 ~ 12 0
14 NGC 6121 80 RG* 16 23 21.1603540392 -26 30 44.093082780 15.77 15.06 13.855   12.320 ~ 14 0
15 2MASS J16232139-2631093 RG* 16 23 21.3967742952 -26 31 09.453054504 14.54 13.281 11.801   10.099 ~ 29 0
16 NGC 6121 352 RG* 16 23 21.6956365512 -26 26 46.944146328 15.61 14.821 13.565   12.031 ~ 21 0
17 Cl* NGC 6121 MVP 33946 RG* 16 23 21.9541703184 -26 30 32.055462756 15.63 14.878 13.643   12.148 ~ 17 0
18 2MASS J16232209-2630520 RG* 16 23 22.1000184168 -26 30 52.107477768 15.51 14.84 13.621   12.063 ~ 7 0
19 NGC 6121 353 RG* 16 23 22.6533747336 -26 26 22.202991384 15.02 14.032 12.651   11.014 ~ 21 0
20 Cl* NGC 6121 S 1753 RG* 16 23 23.0205576120 -26 30 33.673417092 15.48 14.661 13.459   11.906 ~ 11 0
21 NGC 6121 240 RG* 16 23 23.0552864928 -26 33 32.339018160 15.28 14.413 13.112   11.546 ~ 16 0
22 NGC 6121 241 RG* 16 23 23.5445994696 -26 33 41.335025544 15.18 14.40 13.109   11.463 ~ 17 0
23 CD-26 11312 RG* 16 23 23.8093956576 -26 34 29.821786140 14.75 12.63 10.76   8.51 ~ 38 0
24 NGC 6121 35 RG* 16 23 24.0238740192 -26 30 00.551004264 15.17 14.128 12.776   11.162 ~ 20 0
25 NGC 6121 209 RG* 16 23 24.3734062920 -26 32 28.498772292 15.04 13.866 12.437   10.755 ~ 34 0
26 2MASS J16232465-2631114 RG* 16 23 24.6537603408 -26 31 11.501504652 15.65 14.893 13.630   12.089 ~ 12 0
27 Cl* NGC 6121 MVP 31845 RG* 16 23 24.8890788486 -26 31 47.412103302 15.23 14.319 13.019   11.451 ~ 12 0
28 NGC 6121 2 RG* 16 23 24.9961632504 -26 29 25.029889944 15.66 14.937 13.725   12.239 ~ 17 0
29 NGC 6121 243 RG* 16 23 25.3052755200 -26 33 29.260116612 15.17 14.157 12.815   11.201 ~ 15 0
30 NGC 6121 211 RG* 16 23 26.7463955208 -26 32 38.855793840 15.44 14.588 13.290   11.716 ~ 20 0
31 NGC 6121 154 RG* 16 23 26.9462895216 -26 31 31.372012704 15.06 13.898 12.485   10.788 ~ 37 0
32 NGC 6121 89 RG* 16 23 27.0069390312 -26 30 44.470825020 15.38 14.555 13.291   11.764 ~ 15 0
33 NGC 6121 244 RG* 16 23 27.0867816384 -26 33 29.744986932 15.32 14.630 13.361   11.786 ~ 19 0
34 NGC 6121 90 RG* 16 23 27.4228316424 -26 30 59.620969476 15.30 14.39 13.073   11.427 ~ 15 0
35 NGC 6121 45 RG* 16 23 29.1248946984 -26 30 29.805818400 14.92 13.354 11.781   9.988 ~ 48 0
36 NGC 6121 6 RG* 16 23 29.5109139504 -26 29 11.711659776 14.88 13.678 12.246   10.565 ~ 35 0
37 NGC 6121 248 RG* 16 23 30.2119878648 -26 33 24.202101456 14.60 13.519 12.156   10.47 ~ 24 0
38 Cl* NGC 6121 LEE 1619 RG* 16 23 31.4246685816 -26 33 11.109816900 14.67 13.259 11.744   9.982 ~ 20 0
39 NGC 6121 47 RG* 16 23 31.4508993312 -26 30 24.792840288 14.98 13.864 12.471   10.834 ~ 21 0
40 NGC 6121 592 RG* 16 23 31.5128188008 -26 36 18.512950140 15.38 14.708 13.456   11.910 ~ 17 0
41 2MASS J16233236-2629222 RG* 16 23 32.3636738232 -26 29 22.281240948 15.66 14.992 13.880   12.368 ~ 18 0
42 NGC 6121 361 RG* 16 23 32.3708260704 -26 26 20.601330540 15.23 14.364 13.061   11.489 ~ 23 0
43 2MASS J16233304-2632388 RG* 16 23 33.0442826328 -26 32 38.824073988 15.72 15.07 13.88   12.26 ~ 4 0
44 Cl* NGC 6121 MVP 30653 RG* 16 23 33.1031047080 -26 32 30.656495904 15.23 14.377 13.082   11.515 ~ 9 0
45 2MASS J16233315-2632345 RG* 16 23 33.1562353296 -26 32 34.625022612 15.52 14.86 13.66   12.05 ~ 4 0
46 Cl* NGC 6121 LEE 1621 RG* 16 23 33.3816269160 -26 33 14.945612796 15.65 14.864 13.612   12.079 ~ 19 0
47 2MASS J16233380-2627497 RG* 16 23 33.8060898888 -26 27 49.766327352 15.61 14.90 13.677   12.128 ~ 14 0
48 Cl* NGC 6121 MVP 32782 RG* 16 23 33.850 -26 31 14.30 15.81 15.10 13.94   12.38 ~ 4 0
49 Cl* NGC 6121 SAW V17 RG* 16 23 34.0238324712 -26 31 07.863637404 15.06 14.188 12.891   11.331 ~ 12 0
50 NGC 6121 254 RG* 16 23 34.1256590760 -26 33 03.928892112 15.48 14.75 13.470   11.847 ~ 14 0
51 2MASS J16233418-2632485 RG* 16 23 34.1844165672 -26 32 48.545869452 15.52 14.832 13.595   12.063 ~ 10 0
52 2MASS J16233493-2631584 RG* 16 23 34.9485563544 -26 31 58.471652964 15.28 14.53 13.33   11.76 ~ 4 0
53 2MASS J16233510-2632199 RG* 16 23 35.1001124043 -26 32 19.824840777 15.48 14.79 13.61   12.03 ~ 4 0
54 Cl* NGC 6121 MVP 30598 RG* 16 23 35.1876213168 -26 32 32.502462396 14.72 13.49 11.999   10.208 ~ 15 0
55 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1978 0
56 2MASS J16233530-2632166 RG* 16 23 35.3071573536 -26 32 16.645342848 14.91 14.211 12.997   11.359 ~ 8 0
57 NGC 6121 116 RG* 16 23 35.7940031520 -26 30 42.366021552 15.29 14.66 13.435   11.889 ~ 14 0
58 NGC 6121 256 RG* 16 23 35.9270965968 -26 33 34.525803132 15.72 14.95 13.685   12.067 ~ 15 0
59 2MASS J16233596-2631215 RG* 16 23 35.962 -26 31 21.57 15.46 14.80 13.61   12.03 ~ 4 0
60 Cl* NGC 6121 MVP 30675 RG* 16 23 36.5688109061 -26 32 29.700401407 15.52 14.77 13.58   12.00 ~ 9 0
61 NGC 6121 60 RG* 16 23 36.5811712320 -26 30 20.101500180 14.86 13.74 12.322   10.613 ~ 20 0
62 Cl* NGC 6121 MVP 30719 RG* 16 23 36.742 -26 32 28.17 15.79 15.13 13.925   12.405 ~ 6 0
63 2MASS J16233700-2630229 RG* 16 23 37.0066584768 -26 30 22.987248516 15.63 15.08 13.95   12.44 ~ 4 0
64 2MASS J16233712-2633500 RG* 16 23 37.1349921744 -26 33 50.091976332 15.43 14.76 13.489   11.856 ~ 10 0
65 Cl* NGC 6121 MVP 36356 RG* 16 23 37.9512411456 -26 28 41.365716744 15.52 14.759 13.521   12.010 ~ 13 0
66 2MASS J16233821-2631488 RG* 16 23 38.2233472922 -26 31 48.868038721 15.77 15.14 13.943   12.437 ~ 9 0
67 NGC 6121 545 RG* 16 23 38.2590071376 -26 35 55.199209632 15.69 14.94 13.668   12.055 ~ 18 0
68 NGC 6121 127 RG* 16 23 38.2953264850 -26 31 07.189002365 15.43 14.88 13.700 13.445 12.195 ~ 13 0
69 2MASS J16233857-2630380 RG* 16 23 38.5699184424 -26 30 38.182346892 15.15 14.227 12.930   11.389 F0 14 0
70 NGC 6121 23 RG* 16 23 38.6102366832 -26 29 15.996407460 15.32 14.48 13.223   11.657 ~ 15 0
71 NGC 6121 370 RG* 16 23 38.8582043016 -26 25 42.784867632 15.26 14.362 13.071   11.528 ~ 26 0
72 NGC 6121 187 RG* 16 23 38.9271321168 -26 32 03.588004932 15.37 14.52 13.29   11.68 ~ 11 0
73 Cl* NGC 6121 LEE 3218 RG* 16 23 38.9433422448 -26 22 09.505604856 15.60 14.78 13.592   12.033 ~ 15 0
74 NGC 6121 132 RG* 16 23 39.4862873136 -26 31 11.471910204 14.82 13.931 12.635   11.070 ~ 18 0
75 NGC 6121 27 RG* 16 23 39.9822671376 -26 28 49.036544760 14.74 13.304 11.743   9.938 ~ 50 0
76 Cl* NGC 6121 ALC 163 RG* 16 23 40.0065763152 -26 39 03.171895452 16.89 14.668 13.443   11.916 ~ 14 0
77 2MASS J16234010-2631397 RG* 16 23 40.1048966976 -26 31 39.881417484 14.71 13.308 11.804   10.063 ~ 11 0
78 2MASS J16234011-2631171 RG* 16 23 40.1155268640 -26 31 17.273029548 14.88 13.86 12.473   10.781 ~ 14 0
79 NGC 6121 71 RG* 16 23 40.9146947328 -26 30 09.401896656 15.49 14.78 13.570   12.072 ~ 16 0
80 NGC 6121 600 RG* 16 23 40.9203645192 -26 37 23.519488260 15.11 14.234 12.934   11.362 ~ 23 0
81 2MASS J16234098-2631301 RG* 16 23 40.9905392328 -26 31 30.249339708   14.072 12.755   11.117 ~ 14 0
82 2MASS J16234174-2631166 RG* 16 23 41.7520601112 -26 31 16.625136864 15.53 14.82 13.568   12.017 ~ 6 0
83 NGC 6121 72 RG* 16 23 41.7586076760 -26 29 46.773230316 15.68 15.02 13.807   12.284 ~ 18 0
84 2MASS J16234225-2632061 RG* 16 23 42.2604992832 -26 32 06.243594216 15.79 15.12 13.927   12.414 ~ 13 0
85 2MASS J16234260-2633174 RG* 16 23 42.6021374304 -26 33 17.495740584 15.53 14.961 13.793   12.23 ~ 9 0
86 Cl* NGC 6121 SAW V54 RG* 16 23 42.8012546448 -26 29 27.609257292 17.79 13.98 12.66 11.86 11.06 ~ 23 0
87 Cl* NGC 6121 ALC 318 RG* 16 23 43.0923509424 -26 28 07.468793256 15.50 14.75 13.548   12.047 ~ 21 0
88 Cl* NGC 6121 MVP 31665 RG* 16 23 43.2191756904 -26 31 53.948322912 14.94 14.12 12.797   11.159 ~ 10 0
89 2MASS J16234405-2630061 RG* 16 23 44.0648699088 -26 30 06.152203764 14.67 13.262 11.771   10.079 ~ 32 0
90 Cl* NGC 6121 SAW V60 RG* 16 23 45.2128635960 -26 33 56.900805768 15.54 14.82 13.56 12.79 12.02 ~ 23 0
91 Cl* NGC 6121 SAW V56 RG* 16 23 45.9300539040 -26 33 38.946380148 15.02 14.24 12.93 12.13 11.35 ~ 22 0
92 NGC 6121 237 RG* 16 23 46.3293066912 -26 32 27.251725560 14.83 13.586 12.145   10.480 ~ 27 0
93 Cl* NGC 6121 SAW V57 RG* 16 23 46.9279043904 -26 33 43.899680520 15.22 14.256 12.980   11.341 ~ 23 0
94 NGC 6121 144 RG* 16 23 47.6473765008 -26 31 04.240658316 15.45 14.704 13.484   12.007 ~ 16 0
95 NGC 6121 78 RG* 16 23 47.8825228152 -26 29 48.285234744 15.50 14.783 13.575   12.106 ~ 26 0
96 2MASS J16234798-2632428 RG* 16 23 47.9909896704 -26 32 42.908457516 15.64 15.00 13.789   12.288 ~ 13 0
97 Cl* NGC 6121 MVP 27448 RG* 16 23 48.7977828528 -26 35 09.179191752   13.219 11.691   9.909 ~ 18 0
98 Cl* NGC 6121 LEE 3508 RG* 16 23 48.992 -26 29 19.17 15.48 14.94 13.798   12.311 ~ 16 0
99 NGC 6121 478 RG* 16 23 50.1548234376 -26 32 19.496693760 15.46 14.70 13.440   11.902 ~ 16 0
100 NGC 6121 431 RG* 16 23 50.2613060976 -26 29 25.894920300 15.33 14.610 13.408   11.957 ~ 14 0
101 NGC 6121 385 RG* 16 23 53.0053327056 -26 28 06.600361584 15.43 14.744 13.520   12.033 ~ 20 0
102 2MASS J16235358-2634151 RG* 16 23 53.5834359408 -26 34 15.161300760 14.93 13.892 12.534   10.908 ~ 29 0
103 2MASS J16235384-2633525 RG* 16 23 53.8477290288 -26 33 52.539302124 15.13 14.193 12.892   11.327 ~ 19 0
104 2MASS J16235482-2631199 RG* 16 23 54.8223806664 -26 31 19.949551500 15.01 14.34 13.14   11.59 ~ 10 0
105 Cl* NGC 6121 LEE 4421 RG* 16 23 57.4695205632 -26 32 24.861086484 14.99 13.980 12.642   11.055 ~ 22 0
106 NGC 6121 560 RG* 16 23 58.3527495504 -26 35 39.042865968 14.84 13.918 12.609   11.034 ~ 21 0
107 2MASS J16240090-2635531 RG* 16 24 00.9074418912 -26 35 53.138995080 14.95 13.954 12.592   10.948 ~ 10 0
108 Cl* NGC 6121 LEE 3401 RG* 16 24 01.2087134664 -26 31 32.698914276 15.27 14.592 13.401   11.951 ~ 15 0
109 NGC 6121 446 RG* 16 24 04.2921836568 -26 30 27.980605692 14.93 14.231 12.995   11.493 ~ 16 0
110 Cl* NGC 6121 ALC 123 RG* 16 24 05.7182452968 -26 33 01.081766484 15.51 14.91 13.795   12.259 ~ 13 0
111 Cl* NGC 6121 ALC 125 RG* 16 24 07.6713313608 -26 34 25.176038376 15.63 15.03 13.896   12.333 ~ 14 0
112 Cl* NGC 6121 ALC 119 RG* 16 24 15.8913534552 -26 32 27.471227316 15.02 14.278 13.033   11.540 ~ 16 0
113 M 13 GlC 16 41 41.634 +36 27 40.75     5.8     ~ 2291 0
114 NGC 6388 GlC 17 36 17.461 -44 44 08.34           ~ 988 1
115 NGC 6397 GlC 17 40 42.09 -53 40 27.6     5.17     ~ 2103 0
116 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 16269 0
117 NGC 6528 GlC 18 04 49.61 -30 03 20.8   12.12 10.65     ~ 561 0
118 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 1164 0
119 NAME SDG G 18 55 19.0 -30 32 43   4.5 3.6     ~ 2438 2
120 NGC 6752 GlC 19 10 52.11 -59 59 04.4           ~ 2121 0
121 M 71 GlC 19 53 46.49 +18 46 45.1           ~ 1190 0

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