Detailed Chemical Abundances of Four Stars in the Unusual Globular Cluster, Palomar 1

Abstract

Detailed chemical abundances for twenty one elements are presented for four red giants in the anomalous outer halo globular cluster Palomar 1 ($R_{\mathrm{GC}}=17.2$ kpc, $Z=3.6$ kpc) using high-resolution (R=36000) spectra from the High Dispersion Spectrograph (HDS) on the Subaru Telescope. Pal 1 has long been considered unusual because of its low surface brightness, sparse red giant branch, young age, and its possible association with two extragalactic streams of stars---this paper shows that its chemistry further confirms its unusual nature. The mean metallicity of the four stars, $[Fe/H]=-0.60\pm 0.01$, is high for a globular cluster so far from the Galactic center, but is low for a typical open cluster. The [$\alpha$/Fe] ratios, though in agreement with the Galactic stars within the $1\sigma$ errors, agree best with the lower values in dwarf galaxies. No signs of the Na/O anticorrelation are detected in Pal 1, though Na appears to be marginally high in all four stars. Pal 1's neutron capture elements are also unusual: its high [Ba/Y] ratio agrees best with dwarf galaxies, implying an excess of second-peak over first-peak s-process elements, while its [Eu/$\alpha$] and [Ba/Eu] ratios show that Pal 1's contributions from the r-process must have differed in some way from normal Galactic stars. Therefore, Pal 1 is chemically unusual, as well in its other properties. Pal 1 shares some of its unusual abundance characteristics with the young clusters associated with the Sagittarius dwarf galaxy remnant and the intermediate-age LMC clusters, and could be chemically associated with the Canis Majoris overdensity; however it does not seem to be similar to the Monoceros/Galactic Anticenter Stellar Stream.

24 pages, 25 figures; to appear in the Astrophysical Journal

References in corpus (27)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• The Dartmouth Stellar Evolution Database
• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• Non-LTE calculations for neutral Na in late-type stars using improved atomic data
• An Orphan in the "Field of Streams"
• DAOSPEC: an automatic code for measuring equivalent widths in high-resolution stellar spectra
• Assessing the Milky Way Satellites Associated with the Sagittarius Dwarf Spheroidal Galaxy
• The exotic chemical composition of the Sagittarius dwarf Spheroidal galaxy
• A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy
• Analysis and calibration of CaII triplet spectroscopy of Red Giant Branch stars from VLT/FLAMES observations
• Chromium: NLTE abundances in metal-poor stars and nucleosynthesis in the Galaxy
• Improved Laboratory Transition Probabilities for Neutral Chromium and Re-determination of the Chromium Abundance for the Sun and Three Stars
• Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor and Sextans
• The chemical composition of red giant stars in four intermediate-age clusters of the Large Magellanic Cloud
• New Extremely Metal-Poor Stars in the Galactic Halo
• Revisiting the influence of unidentified binaries on velocity dispersion measurements in ultra-faint stellar systems
• M67-1194, an unusually Sun-like solar twin in M67
• High-resolution spectroscopy of RGB stars in the Sagittarius Streams. I. Radial velocities and chemical abundances
• The chemical evolution of Manganese in different stellar systems
• Heavy element abundances in giant stars of the globular clusters M4 and M5
• Whiting 1: the youngest globular cluster associated with the Sgr dSph
• Search and analysis of blue straggler stars in open clusters
• The Tidal Tails of the Ultra-Faint Globular Cluster Palomar 1
• The Chemical Evolution of the Monoceros Ring/Galactic Anticenter Stellar Structure
• Formation of MnI lines in the solar atmosphere
• A deep view of the Monoceros ring in the Anticenter direction: clues of its extra-Galactic origin
• High Resolution HDS/SUBARU chemical abundances of the young stellar cluster Palomar 1

Cited by in corpus (21)

• Target Selection for the Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• Evidence from the H3 Survey that the Stellar Halo is Entirely Comprised of Substructure
• What is a globular cluster? An observational perspective
• Homogeneous photometry VII. Globular clusters in the Gaia era
• The Chemo-Dynamical Groups of Galactic Globular Clusters
• VLT/FLAMES spectroscopy of red giant branch stars in the Fornax dwarf spheroidal galaxy
• NGC 6535: the lowest mass Milky Way globular cluster with a Na-O anti-correlation? Cluster mass and age in the multiple population context
• GRACES observations of young [alpha/Fe]-rich stars
• The OCCASO survey: Presentation and radial velocities of twelve Milky Way Open Clusters
• Kim 3: an Ultra-faint Star Cluster in the Constellation of Centaurus
• Integrated Light Chemical Tagging Analyses of Seven M31 Outer Halo Globular Clusters from the Pan-Andromeda Archaeological Survey
• Spectrum Syntheses of High Resolution Integrated Light Spectra of Galactic Globular Clusters
• G2C2 II: Integrated colour-metallicity relations for Galactic Globular Clusters in SDSS passbands
• Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters
• Optimal Integrated Abundances for Chemical Tagging of Extragalactic Globular Clusters
• The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy
• The in situ origin of the globular cluster NGC 6388 from abundances of Sc, V, and Zn of a large sample of stars
• The Peculiar Globular Cluster Palomar 1 and Persistence in the SDSS-APOGEE Database
• A Multi-Wavelength Study of the Segue 3 Cluster
• A Dwarf Galaxy Debris Stream Associated with Palomar 1 and the Anticenter Stream
• Astrophysical Origins for the Unusual Chemical Abundance of the Globular Cluster Palomar 1