Spectroscopy of Globular Clusters in the Spheroidal Dwarf Galaxy IKN

详细

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 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 ± 30 km/s, age T =12.6 ± 2 Gyr, metallicity [Fe/H] = −2.1 ± 0.2 dex, and abundance of α-process elements [α/Fe] ∼ 0.5 dex. The integrated spectrum of the two weaker clusters IKN1 and IKN3, which are far from the center of the galaxy, yielded the radial velocity V_h = −39 ± 50 km/s. Despite the low signal-to-noise ratio in the integrated spectrum for IKN1 and IKN3, all the analysis methods applied indicate that these two objects have approximately the same age and metallicity as IKN4 and IKN5. According to the measured Lick indices \({{\rm{H}}_{\delta {\rm{F}}}}\) and H_β, the studied globular clusters in IKN have blue horizontal branches.