2012A&A...539A..19G


C.D.S. - SIMBAD4 rel 1.7 - 2020.10.25CET10:00:59

2012A&A...539A..19G - Astronomy and Astrophysics, volume 539A, 19-19 (2012/3-1)

The Na-O anticorrelation in horizontal branch stars. II. NGC 1851.

GRATTON R.G., LUCATELLO S., CARRETTA E., BRAGAGLIA A., D'ORAZI V., AL MOMANY Y., SOLLIMA A., SALARIS M. and CASSISI S.

Abstract (from CDS):

The chemical composition of horizontal branch (HB) stars might help to clarify the formation history of individual globular clusters (GCs). We studied the Na-O anti-correlation from moderately high resolution spectra for 91 stars on the bimodal HB of NGC 1851; in addition we observed 13 stars on the lower red giant branch (RGB). In our HB sample, 35 stars are on the blue HB (BHB), one is an RR Lyrae, and 55 stars are on the red HB (RHB). The ratio of BHB to RHB stars is close to the total in the cluster (35 and 54%, respectively), while RR Lyrae variables are under-represented, (they are ∼12% of the NGC 1851 stars). We also derived abundances for He and N in BHB stars. For RHB stars we derived Ba abundances and a few interesting upper limits for N. The RHB stars clearly separate into two groups: the vast majority are O-rich and Na-poor, while about 10-15% are Na-rich and moderately O-poor. Most (but not all) Na-rich RHB stars are also Ba-rich and there is an overall correlation between Na and Ba abundances within the RHB. The group of Ba-rich RHB stars resides on the warmer edge and includes ∼10% of the RHB stars. We propose that they are the descendant of the stars on the RGB sequence with very red v-y colour. This sequence is known also to consist of Ba and perhaps CNO-rich stars and consistently includes ∼5-10% of the RGB stars of NGC 1851. However, the upper limit we obtain for N ([N/Fe]<1.55) for one of the Ba-rich stars coupled with the low C-abundances for RGB Ba-rich stars from the literature suggests that the total CNO might not be particularly high ([(C+N+O)/Fe]≤0.15). The other Na-rich RHB stars are also at the warm edge of the RHB and the only RR Lyrae is Na-rich and moderately O-poor. We also find a Na-O anticorrelation among BHB stars, partially overlapping that found among RHB stars, though generally BHB stars are more Na-rich and O-poor. However, there is no clear correlation between temperature and Na and O abundances within the BHB. The average He abundance in BHB stars is Y=0.29±0.05, which excludes a large population of extremely He-rich stars from our sample. N abundances are quite uniform at [N/Fe]=1.16±0.14 among BHB stars, with a small trend with temperature. This value is consistent with normal CNO abundance and excludes that BHB stars are very CNO-rich: this leaves an age spread of ∼1.5Gyr as the only viable explanation for the split of the SGB. To help clarifying the formation history of NGC 1851, we computed synthetic HB's trying to identify which HB stars are the descendant of the bright and faint subgiant branch (b-SGB and f-SGB) stars identified by Milone et al. (2008ApJ...673..241M), with respectively 2/3 and 1/3 of the stars of NGC 1851. While most BHB stars likely descend from f-SGB stars and are older, and most RHB stars from b-SGB ones and are younger, the correspondence is probably not one-to-one. In particular, the Ba-rich RHB stars should be less massive than the remaining RHB stars, and the location of their progenitors on the SGB is uncertain. If they descend from f-SGB stars, number counts then require that RR Lyrae variables and possibly some mild BHB stars descend from b-SGB stars; this suggestion is supported by a few circumstantial facts. An investigation of the composition of a large enough sample of SGB stars is required to firmly establish these relations.

Abstract Copyright:

Journal keyword(s): stars: evolution - stars: abundances - stars: Population II - globular clusters: general - globular clusters: individual: NGC 1851

VizieR on-line data: <Available at CDS (J/A+A/539/A19): table1.dat table2.dat table3.dat>

Nomenclature: Table 1: [GLC2012] NNNNN N=103 among (Nos 3515-54362).

Errata: + corrigendum vol. 547, p. C2

Simbad objects: 111

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Number of rows : 111

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NGC 362 GlC 01 03 14.26 -70 50 55.6     6.58     ~ 945 0
2 [GLC2012] 13627 HB* 05 13 31.9813836459 -40 10 16.855116333   16.750 16.120     ~ 1 0
3 GES J05134234-4009166 HB* 05 13 42.3553260768 -40 09 16.765896261   16.512 16.538     ~ 3 0
4 GES J05134403-4008483 HB* 05 13 44.0385868718 -40 08 48.467275215   16.312 16.276     ~ 2 0
5 GES J05134784-4005317 HB* 05 13 47.8581090270 -40 05 31.919431817   16.902 16.210     ~ 2 0
6 GES J05134971-4001466 HB* 05 13 49.7226459673 -40 01 46.767748234   16.833 16.229     ~ 2 0
7 [CLG2011] 34604 RG* 05 13 50.776 -40 02 36.82   17.487 16.701     ~ 3 0
8 GES J05135122-4004203 HB* 05 13 51.2331987054 -40 04 20.486527256   16.781 16.173     ~ 2 0
9 Cl* NGC 1851 PML 14 HB* 05 13 54.2426893983 -40 03 53.642766383   16.750 16.776     ~ 2 0
10 GES J05135428-4005369 HB* 05 13 54.2956024684 -40 05 37.104221690   16.911 16.241     ~ 2 0
11 GES J05135428-4002387 HB* 05 13 54.2967265286 -40 02 38.855945547   16.746 16.084     ~ 2 0
12 [GLC2012] 25504 HB* 05 13 54.5010197727 -40 04 24.478249958   16.842 16.221     ~ 1 0
13 GES J05135462-4001242 HB* 05 13 54.6270522985 -40 01 24.399053967   16.820 16.214     ~ 2 0
14 2MASS J05135471-4002458 HB* 05 13 54.713 -40 02 45.85   16.507 16.526     ~ 3 0
15 GES J05135514-4004213 HB* 05 13 55.1544675156 -40 04 21.482730663   16.845 16.182     ~ 2 0
16 Cl* NGC 1851 PML 27 HB* 05 13 55.740 -40 02 32.45   17.005 17.093     ~ 2 0
17 GES J05135593-3958236 HB* 05 13 55.9476212198 -39 58 23.756672972   16.832 16.214     ~ 2 0
18 [GLC2012] 28175 HB* 05 13 56.128 -40 03 48.96   16.895 16.198     ~ 2 0
19 GES J05135629-4006237 HB* 05 13 56.2960670866 -40 06 23.945477383   16.859 16.203     ~ 2 0
20 GES J05135631-4001412 HB* 05 13 56.3218825761 -40 01 41.486867270   16.859 16.245     ~ 2 0
21 [GLC2012] 31903 HB* 05 13 56.3781272684 -40 03 06.292447538   16.717 16.159     ~ 1 0
22 2MASS J05135695-4003454 RG* 05 13 56.9622960399 -40 03 45.618867722   17.567 16.753     ~ 1 0
23 Cl* NGC 1851 PML 20 HB* 05 13 57.151 -40 03 30.37   17.025 17.104     ~ 2 0
24 [GLC2012] 31496 HB* 05 13 57.3211529396 -40 03 11.124339431   16.802 16.188     ~ 1 0
25 GES J05135746-4001345 HB* 05 13 57.4762254058 -40 01 34.771486961   16.830 16.215     ~ 2 0
26 [GLC2012] 31651 HB* 05 13 57.827 -40 03 09.35   16.860 16.210     ~ 2 0
27 Cl* NGC 1851 PML 30 HB* 05 13 58.666 -40 02 18.30   17.175 17.282     ~ 3 0
28 GES J05135892-4001072 HB* 05 13 58.9322865399 -40 01 07.487886658   16.258 16.211     ~ 2 0
29 [CLG2011] 25497 RG* 05 13 59.2279281007 -40 04 24.405044575   17.452 16.608     ~ 5 0
30 [GLC2012] 39832 HB* 05 13 59.3979037248 -40 01 36.749988381   16.748 16.118     ~ 1 0
31 GES J05135955-3957526 HB* 05 13 59.5643986735 -39 57 52.738733128   16.822 16.199     ~ 2 0
32 GES J05135961-3954211 HB* 05 13 59.6212819198 -39 54 21.264606033   16.342 16.342     ~ 2 0
33 GES J05135970-4005203 HB* 05 13 59.7136357503 -40 05 20.481051254   16.864 16.912     ~ 2 0
34 GES J05135983-4003417 RR* 05 13 59.8461707723 -40 03 41.926850211   16.488 16.122     ~ 3 0
35 GES J05135989-4004382 HB* 05 13 59.8978783074 -40 04 38.430637871   16.851 16.193     ~ 2 0
36 [GLC2012] 42849 HB* 05 14 00.460 -40 00 53.24   16.755 16.169     ~ 2 0
37 2MASS J05140083-4001343 RG* 05 14 00.8471276525 -40 01 34.561056066   17.303 16.490     ~ 2 0
38 [GLC2012] 35868 HB* 05 14 00.891 -40 02 22.26   16.075 16.057     ~ 1 0
39 2MASS J05140113-4004075 HB* 05 14 01.135 -40 04 07.59   16.461 16.458     ~ 2 0
40 [GLC2012] 28746 HB* 05 14 01.579 -40 03 41.84   16.828 16.195     ~ 2 0
41 GES J05140201-4001283 HB* 05 14 02.0200630469 -40 01 28.498998470   16.790 16.187     ~ 2 0
42 [GLC2012] 38250 RG* 05 14 02.111 -40 01 55.53   17.441 16.628     ~ 1 0
43 Cl* NGC 1851 PML 11 HB* 05 14 02.175 -40 03 53.79   16.945 16.979     ~ 2 0
44 GES J05140257-4000185 HB* 05 14 02.5878417318 -40 00 18.682548850   16.825 16.227     ~ 2 0
45 [GLC2012] 29078 HB* 05 14 02.880 -40 03 37.87   16.771 16.111     ~ 1 0
46 GES J05140328-4005069 HB* 05 14 03.2918370644 -40 05 07.086017488   16.831 16.169     ~ 2 0
47 GES J05140344-4001327 HB* 05 14 03.4584786316 -40 01 32.868744120   16.815 16.212     ~ 2 0
48 GES J05140391-3956569 HB* 05 14 03.9226122911 -39 56 57.057454289   16.284 16.160     ~ 3 0
49 [GLC2012] 27604 HB* 05 14 04.042 -40 03 55.74   16.849 16.217     ~ 2 0
50 2MASS J05140473-4007017 RG* 05 14 04.7383507265 -40 07 01.938528534   17.339 16.521     ~ 7 0
51 [GLC2012] 39317 HB* 05 14 05.012 -40 01 42.74   16.646 16.091     ~ 1 0
52 [GLC2012] 28346 HB* 05 14 05.052 -40 03 46.82   16.267 16.187     ~ 2 0
53 Cl* NGC 1851 PML 42 HB* 05 14 05.087 -40 01 09.76   16.436 16.491     ~ 3 0
54 [GLC2012] 40897 HB* 05 14 05.974 -40 01 22.55   16.778 16.183     ~ 1 0
55 GES J05140601-4001303 HB* 05 14 06.0295095394 -40 01 30.497254317   16.824 16.214     ~ 2 0
56 2MASS J05140647-4005417 RG* 05 14 06.4785255419 -40 05 41.893542064   17.344 16.515     ~ 6 0
57 NGC 1851 GlC 05 14 06.76 -40 02 47.6   8.80 7.23     ~ 1252 0
58 [GLC2012] 40227 HB* 05 14 07.034 -40 01 31.43   16.826 16.902     ~ 1 0
59 GES J05140739-4005247 HB* 05 14 07.4028940208 -40 05 24.843411788   16.851 16.188     ~ 2 0
60 2MASS J05140757-3959055 HB* 05 14 07.575 -39 59 05.58   16.708 16.787     ~ 2 0
61 [GLC2012] 27085 RG* 05 14 08.5719134785 -40 04 02.414544719   17.306 16.528     ~ 1 0
62 GES J05140879-4000336 HB* 05 14 08.8129227132 -40 00 33.729139519   16.636 16.715     ~ 3 0
63 [GLC2012] 23344 HB* 05 14 09.550 -40 05 01.09   16.847 16.211     ~ 2 0
64 GES J05140956-4000030 RG* 05 14 09.5768666317 -40 00 03.120079701   17.487 16.720     ~ 2 0
65 Cl* NGC 1851 PML 10 HB* 05 14 09.589 -40 03 50.38   16.433 16.456     ~ 3 0
66 [GLC2012] 38202 HB* 05 14 09.724 -40 01 55.85   16.824 16.191     ~ 2 0
67 2MASS J05141002-3959035 RG* 05 14 10.0378838511 -39 59 03.647601355   17.316 16.521     ~ 6 0
68 GES J05141017-4004275 HB* 05 14 10.1872377244 -40 04 27.619494924   16.797 16.149     ~ 2 0
69 [GLC2012] 41381 HB* 05 14 10.3984537504 -40 01 15.781249481   16.792 16.222     ~ 1 0
70 2MASS J05141133-4004092 RG* 05 14 11.3377866696 -40 04 09.403210248   17.293 16.472     ~ 7 0
71 GES J05141154-4004221 HB* 05 14 11.5485850773 -40 04 22.222753254   16.825 16.207     ~ 2 0
72 GES J05141165-4001110 HB* 05 14 11.6637990142 -40 01 11.199106693   16.792 16.886     ~ 3 0
73 GES J05141212-4004118 HB* 05 14 12.1278174637 -40 04 11.930209053   16.196 16.131     ~ 2 0
74 [GLC2012] 46902 HB* 05 14 12.3352668214 -39 58 48.145453350   16.202 16.098     ~ 1 0
75 GES J05141276-4001428 HB* 05 14 12.7786246686 -40 01 42.971926527   16.476 16.529     ~ 3 0
76 [GLC2012] 33196 HB* 05 14 12.798 -40 02 50.98   16.808 16.185     ~ 2 0
77 Cl* NGC 1851 PML 36 HB* 05 14 13.145 -40 01 28.07   16.737 16.801     ~ 3 0
78 [GLC2012] 37121 HB* 05 14 13.327 -40 02 07.68   16.754 16.124     ~ 2 0
79 GES J05141341-4003177 HB* 05 14 13.4276690912 -40 03 17.849634573   16.801 16.179     ~ 2 0
80 GES J05141342-4003017 HB* 05 14 13.4329997328 -40 03 01.836790141   16.815 16.204     ~ 2 0
81 GES J05141367-4002390 HB* 05 14 13.6860335348 -40 02 39.099247335   16.824 16.183     ~ 2 0
82 GES J05141410-4003273 HB* 05 14 14.1053824303 -40 03 27.401189302   16.819 16.181     ~ 2 0
83 [GLC2012] 35789 HB* 05 14 14.3258559149 -40 02 22.544251895   16.756 16.111     ~ 1 0
84 Cl* NGC 1851 PML 8 HB* 05 14 14.8074893935 -40 03 49.777372991   16.766 16.817     ~ 2 0
85 Cl* NGC 1851 PML 1 HB* 05 14 15.2402022593 -40 06 28.916489253   16.501 16.497     ~ 2 0
86 [GLC2012] 31469 HB* 05 14 15.514 -40 03 10.79   16.832 16.189     ~ 2 0
87 GES J05141556-4005199 HB* 05 14 15.5727632528 -40 05 20.040701644   16.855 16.196     ~ 2 0
88 GES J05141580-4002225 HB* 05 14 15.8206680003 -40 02 22.677028171   16.471 16.468     ~ 3 0
89 GES J05141581-4006110 HB* 05 14 15.8269511167 -40 06 11.202334992   16.430 16.394     ~ 4 0
90 GES J05141607-4002074 HB* 05 14 16.0872398804 -40 02 07.540319078   16.781 16.177     ~ 2 0
91 GES J05141660-4004259 HB* 05 14 16.6191918588 -40 04 26.031544666   16.812 16.191     ~ 2 0
92 GES J05141720-4004113 HB* 05 14 17.2167145347 -40 04 11.426547876   16.871 16.917     ~ 3 0
93 Cl* NGC 1851 PML 19 HB* 05 14 19.417 -40 03 06.26   16.765 16.824     ~ 3 0
94 GES J05142016-4001308 HB* 05 14 20.1780028388 -40 01 30.885669192   16.795 16.859     ~ 4 0
95 2MASS J05142070-4004195 RG* 05 14 20.7103021146 -40 04 19.521726666   17.344 16.493     ~ 7 0
96 2MASS J05142185-4006005 HB* 05 14 21.859 -40 06 00.60   16.723 16.737     ~ 3 0
97 GES J05142280-4001177 HB* 05 14 22.8258285189 -40 01 17.799045018   16.772 16.157     ~ 2 0
98 GES J05142749-4002128 HB* 05 14 27.5067716453 -40 02 12.892942171   16.822 16.199     ~ 2 0
99 GES J05143307-4003069 HB* 05 14 33.0847579571 -40 03 06.976288018   16.650 16.665     ~ 3 0
100 GES J05143502-4003190 HB* 05 14 35.0344245378 -40 03 19.029502996   16.850 16.195     ~ 2 0
101 2MASS J05143598-4005532 RG* 05 14 35.9989323769 -40 05 53.046434139   17.512 16.680     ~ 6 0
102 GES J05143697-4004163 HB* 05 14 36.9839567414 -40 04 16.348942849   16.829 16.162     ~ 2 0
103 GES J05144144-4005437 HB* 05 14 41.4481573336 -40 05 43.681880841   16.699 16.129     ~ 2 0
104 GES J05144219-3956593 HB* 05 14 42.2049080371 -39 56 59.317731541   16.687 16.144     ~ 2 0
105 [GLC2012] 52576 HB* 05 14 53.2205370647 -40 01 53.010242728   16.767 16.818     ~ 1 0
106 NGC 2808 GlC 09 12 03.10 -64 51 48.6   7.77 5.69     ~ 1254 0
107 NGC 5139 GlC 13 26 47.28 -47 28 46.1   6.12 5.33     ~ 3032 0
108 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1685 0
109 M 22 GlC 18 36 23.94 -23 54 17.1   7.16 6.17     ~ 1228 0
110 M 54 GlC 18 55 03.33 -30 28 47.5           ~ 914 0
111 NGC 6752 GlC 19 10 52.11 -59 59 04.4   6.96 6.28     ~ 1817 0

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2020.10.25-10:00:59

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