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

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 $8$m VLT UT2-Kueyen telescope equipped with the UVES spectrograph in FLAMES$+$UVES configuration. Spectroscopic parameters were derived through excitation and ionisation equilibrium of \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 $174.3\pm 1.6$ km\,s${}^{-1}$ and a mean metallicity of [Fe/H]$=-1.10\pm 0.09$ for the cluster. We found an enhancement of $\alpha$-elements (O, Mg, Si, and Ca) $0.29<$[X/Fe]$<0.38$ and the iron-peak element Ti of [Ti/Fe]$\sim +0.3$. The odd-Z elements (Na and Al) show a mild enhancement of [X/Fe]$\sim +0.25$. The abundances of both first- (Y and Zr) and second-peak (Ba and La) heavy elements are relatively high, with $+0.4<$[X/Fe]$<+0.60$ and $+0.4<$[X/Fe]$<+0.5$, respectively. The r-element Eu is also relatively high with [Eu/Fe]$\sim +0.6$. $\left[\mathbf{Truncated}\right]$

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

References in corpus (27)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The K2 Mission: Characterization and Early results
• galpy: A Python Library for Galactic Dynamics
• The mass distribution and gravitational potential of the Milky Way
• Gaia Early Data Release 3: Photometric content and validation
• Fast rotating massive stars and the origin of the abundance patterns in galactic globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• Gaia EDR3 view on Galactic globular clusters
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• Accurate distances to Galactic globular clusters through a combination of Gaia EDR3, HST and literature data
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• The elemental composition of the Sun III. The heavy elements Cu to Th
• Both accurate and precise gf-values for FeII lines
• The role of neutron star mergers in the chemical evolution of the Galactic halo
• Age as a Major Factor in the Onset of Multiple Populations in Stellar Clusters
• APOGEE Chemical Abundances of Globular Cluster Giants in the Inner Galaxy
• The State-of-the-Art HST Astro-Photometric Analysis of the core of ωCentauri. III. The Main Sequence's Multiple Populations Galore
• High-resolution abundance analysis of red giants in the globular cluster NGC 6522
• The search for multiple populations in Magellanic Clouds clusters - V. Correlation between cluster age and abundance spreads
• A Deep View of a Fossil Relic in the Galactic Bulge: The Globular Cluster HP1
• Homogeneous Analysis of Globular Clusters from the APOGEE Survey with the BACCHUS Code $-$ III. $\omega$ Cen
• Self-consistent analysis of stellar clusters: An application to HST data of the halo globular cluster NGC 6752
• VVV CL001: Likely the Most Metal-Poor Surviving Globular Cluster in the Inner Galaxy
• A new identity card for the bulge globular cluster NGC 6440 from resolved star counts
• Another relic bulge globular cluster: ESO 456-SC38 (Djorgovski~2)
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXII. Relative ages of multiple populations in five Globular Clusters
• Spectroscopic Observations of Obscured Populations in the Inner Galaxy: 2MASS-GC02, Terzan 4, and the 200 km/s stellar peak