English

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

Astrophysics of Galaxies 2021-12-10 v2 Solar and Stellar Astrophysics

Abstract

Palomar 6 (Pal~6) 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. 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 Pal~6 from Hubble Space Telescope (HST) photometric data, and an orbital analysis to determine the probable origin of the cluster. High-resolution spectra of six red giant stars in the direction of Palomar 6 were obtained at the 88m VLT UT2-Kueyen telescope equipped with the UVES spectrograph in FLAMES++UVES configuration. Spectroscopic parameters were derived through excitation and ionisation equilibrium of \ion{Fe}{I} and \ion{Fe}{II} 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. Four stars that are members of Pal~6 were identified in the sample, which gives a mean radial velocity of 174.3±1.6174.3\pm1.6 km\,s1^{-1} and a mean metallicity of [Fe/H]=1.10±0.09\,=-1.10\pm0.09 for the cluster. We found an enhancement of α\alpha-elements (O, Mg, Si, and Ca) 0.29<0.29<\,[X/Fe]<0.38\,<0.38 and the iron-peak element Ti of [Ti/Fe]+0.3\,\sim+0.3. The odd-Z elements (Na and Al) show a mild enhancement of [X/Fe]+0.25\,\sim +0.25. The abundances of both first- (Y and Zr) and second-peak (Ba and La) heavy elements are relatively high, with +0.4<+0.4<\,[X/Fe]<+0.60\,<+0.60 and +0.4<+0.4<\,[X/Fe]<+0.5\,<+0.5, respectively. The r-element Eu is also relatively high with [Eu/Fe]+0.6\,\sim +0.6. [Truncated]\mathbf{\left[Truncated\right]}

Keywords

Cite

@article{arxiv.2109.04483,
  title  = {Photo-chemo-dynamical analysis and the origin of the bulge globular cluster Palomar 6},
  author = {Stefano O. Souza and Marica Valentini and Beatriz Barbuy and Angeles Pérez-Villegas and Cristina Chiappini and Sergio Ortolani and Domenico Nardiello and Bruno Dias and Friedrich Anders and Eduardo Bica},
  journal= {arXiv preprint arXiv:2109.04483},
  year   = {2021}
}

Comments

23 pages, 26 figures, and 12 tables. References added, typos corrected, published version