2021A&A...656A..78S


Query : 2021A&A...656A..78S

2021A&A...656A..78S - Astronomy and Astrophysics, volume 656A, 78-78 (2021/12-1)

Photo-chemo-dynamical analysis and the origin of the bulge globular cluster Palomar 6.

SOUZA S.O., VALENTINI M., BARBUY B., PEREZ-VILLEGAS A., CHIAPPINI C., ORTOLANI S., NARDIELLO D., DIAS B., ANDERS F. and BICA E.

Abstract (from CDS):


Context. Palomar 6 (Pal6) is a moderately metal-poor globular cluster projected towards the Galactic bulge. A full analysis of the cluster can give hints on the early chemical enrichment of the Galaxy and a plausible origin of the cluster.
Aims. The aim of this study is threefold: a detailed analysis of high-resolution spectroscopic data obtained with the UVES spectrograph at the Very Large Telescope (VLT) at ESO, the derivation of the age and distance of Pal6 from Hubble Space Telescope (HST) photometric data, and an orbital analysis to determine the probable origin of the cluster.
Methods. High-resolution spectra of six red giant stars in the direction of Pal6 were obtained at the 8 m VLT UT2-Kueyen telescope equipped with the UVES spectrograph in FLAMES+UVES configuration. Spectroscopic parameters were derived through excitation and ionisation equilibrium of FeI and FeII lines, and the abundances were obtained from spectrum synthesis. From HST photometric data, the age and distance were derived through a statistical isochrone fitting. Finally, a dynamical analysis was carried out for the cluster assuming two different Galactic potentials.
Results. Four stars that are members of Pal 6 were identified in the sample, which gives a mean radial velocity of 174.3 ± 1.6 km s–1 and a mean metallicity of [Fe/H] = -1.10 ± 0.09 for the cluster. We found an enhancement of α-elements (O, Mg, Si, and Ca) of 0.29< [X/Fe] < 0.38 and the iron-peak element Ti of [Ti/Fe] ∼ +0.3. The odd-Z elements (Na and Al) show a mild enhancement of [X/Fe] ∼ +0.25. The abundances of both first- (Y and Zr) and second-peak (Ba and La) heavy elements are relatively high, with +0.4 < [X/Fe] < +0.60 and +0.4 < [X/Fe] < +0.5, respectively. The r-element Eu is also relatively high with [Eu/Fe] ∼ +0.6. One member star presents enhancements in N and Al, with [Al/Fe] > +0.30, this being evidence of a second stellar population, further confirmed with the NaON-Al (anti)correlations. For the first time, we derived the age of Pal 6, which resulted to be 12.4 ± 0.9 Gyr. We also found a low extinction coefficient RV = 2.6 for the Pal 6 projection, which is compatible with the latest results for the highly extincted bulge populations. The derived extinction law results in a distance of 7.67 ± 0.19 kpc from the Sun with an AV = 4.21 ± 0.05. The chemical and photometric analyses combined with the orbital-dynamical analyses point out that Pal 6 belongs to the bulge component probably formed in the main-bulge progenitor.Conculsions. The present analysis indicates that the globular cluster Pal 6 is located in the bulge volume and that it was probably formed in the bulge in the early stages of the Milky Way formation, sharing the chemical properties with the family of intermediate metallicity very old clusters M 62, NGC 6522, NGC 6558, and HP 1.

Abstract Copyright: © ESO 2021

Journal keyword(s): Galaxy: bulge - globular clusters: individual: Palomar 6 - stars: abundances - Hertzsprung-Russell and C-M diagrams - Galaxy: kinematics and dynamics

Simbad objects: 19

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Number of rows : 19
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 NGC 5139 GlC 13 26 47.28 -47 28 46.1           ~ 3299 0
2 * alf Boo RG* 14 15 39.67207 +19 10 56.6730 2.46 1.18 -0.05 -1.03 -1.68 K1.5IIIFe-0.5 2257 0
3 M 62 GlC 17 01 12.60 -30 06 44.5           ~ 579 0
4 ESO 455-11 GlC 17 31 05.20 -29 58 54.0           ~ 156 0
5 Liller 1 Cl* 17 33 24.50 -33 23 20.0           ~ 240 0
6 2MASS J17433806-2613426 * 17 43 38.06784 -26 13 42.6000           ~ 2 0
7 2MASS J17433862-2615013 * 17 43 38.62200 -26 15 01.3680           ~ 1 0
8 2MASS J17433876-2612551 * 17 43 38.76216 -26 12 55.1736           ~ 1 0
9 2MASS J17433889-2614359 * 17 43 38.89272 -26 14 35.9484           ~ 1 0
10 ESO 520-21 GlC 17 43 42.20 -26 13 21.0           ~ 167 0
11 2MASS J17434250-2614101 * 17 43 42.50928 -26 14 10.1688           ~ 1 0
12 2MASS J17434440-2612418 * 17 43 44.40120 -26 12 41.8680           ~ 1 0
13 NAME Galactic Center reg 17 45 39.60213 -29 00 22.0000           ~ 13433 0
14 NGC 6552 Sy2 18 00 07.2518347776 +66 36 54.360343188   14.6 13.74     ~ 149 2
15 NGC 6522 GlC 18 03 34.08 -30 02 02.3           ~ 502 0
16 NGC 6558 GlC 18 10 17.6 -31 45 50           ~ 211 0
17 Cl Terzan 7 GlC 19 17 43.92 -34 39 27.8           ~ 407 0
18 NAME Galactic Bulge reg ~ ~           ~ 4012 0
19 NAME Gaia Enceladus-Sausage St* ~ ~           ~ 352 0

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2023.01.31-02:13:54

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