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Galactic Pal-eontology: abundance analysis of the disrupted globular cluster Palomar 5

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Article numberA41
<mark>Journal publication date</mark>1/05/2017
<mark>Journal</mark>Astronomy and Astrophysics
Number of pages9
Publication StatusPublished
<mark>Original language</mark>English


We present a chemical abundance analysis of the tidally disrupted globular cluster (globular cluster) Palomar 5. By co-adding highresolution spectra of 15 member stars from the cluster’s main body, taken at low-signal-to-noise with the Keck/HIRES spectrograph, we were able to measure integrated abundance ratios of 24 species of 20 elements including all major nucleosynthetic channels (namely the light element Na; α-elements Mg, Si, Ca, Ti; Fe-peak and heavy elements Sc, V, Cr, Mn, Co, Ni, Cu, Zn; and the neutroncapture elements Y, Zr, Ba, La, Nd, Sm, Eu). The mean metallicity of −1.47±0.02±0.06 dex (statistical and systematic errors) agrees
well with the values from individual, low-resolution measurements of individual stars, but it is lower than previous high-resolution results of a small number of stars in the literature. Comparison with Galactic halo stars and other disrupted and unperturbed globular clusters renders Pal 5 a typical representative of the Milky Way halo population, as has been noted before, emphasizing that the early chemical evolution of such clusters is decoupled from their later dynamical history. We also performed a test as to the detectability of light element variations in this co-added abundance analysis technique and find that this approach is not sensitive even in the presence of a broad range in sodium of ∼0.6 dex, a value typically found in the old halo globular clusters. Thus, while methods of determining the global abundance patterns of such objects are well suited to study their overall enrichment histories, chemical distinctions of their
multiple stellar populations is still best obtained from measurements of individual stars.