Spectroscopy of globular clusters in the dwarf spheroidal galaxy IKN

Abstract

Moderate resolution spectra of four globular clusters in the dwarf spheroidal galaxy IKN obtained with the 6-m telescope of the Special Astrophysical Observatory have been used to determine the radial velocities, ages, and metallicities of the clusters, and also to derive the first approximate estimates of the abundances of Mg, Ca, and C. Cross-correlation with radial-velocity standards, fitting of the observed spectra with model spectra, diagnostic diagrams based on the Lick absorption indices, and comparison of the spectra and absorption indices with those of Galactic globular clusters are applied. The integrated-light (IL) spectrum of the two bright clusters IKN4 and IKN5, which are close to the center of the galaxy in projection on the celestial sphere, yields the heliocentric radial velocity $V_h=38\pm 30$ km/s, age $T=12.6\pm 2$ Gyr, metallicity $[Fe/H]=-2.1\pm 0.2$ dex and abundance of $\alpha$-process elements $[\alpha /Fe]\sim 0.5$ dex. The IL spectrum of the two weaker clusters IKN1 and IKN3, which are far from the center of the galaxy, yields the radial velocity $V_h=-39\pm 50$ km/s. Despite of the low signal to noise ratio in the summary spectrum of IKN1 and IKN3, one can conclude from the comparison of the results of different used methods, that IKN1 and IKN3 have seemingly the same age and metallicity as IKN4 and IKN5. According to the measured Lick indices H${}_{{\delta }_{\mathrm{F}}}$ and H${}_{\beta }$, the studied globular clusters in IKN have blue horizontal branches.

arXiv comment17 pages, 7 tables, 5 figures

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