Quantitative spectroscopy of supergiants in the Local Group dwarf galaxy IC 1613: metallicity and distance.
BERGER T.A., KUDRITZKI R.-P., URBANEJA M.A., BRESOLIN F., GIEREN W., PIETRZYNSKI G. and PRZYBILLA N.
Abstract (from CDS):
We present a spectral analysis of 21 blue supergiant stars of spectral types late B to early A within the Local Group dwarf galaxy IC 1613, based on VLT Focal Reducer and Low Dispersion Spectrograph 2 low-resolution spectra. Combining our results with studies of early B-type blue supergiants, we report a wide bimodal distribution of metallicities with two peaks around [Z] ∼ -0.50 dex and [Z] ∼ -0.85 dex. The bimodal distribution correlates with spatial location, when compared with column densities of neutral hydrogen in IC 1613. While the low [Z] objects appear in regions of relatively high ISM H I column densities or close to them, the high [Z] supergiants are found in the central H I hole that is almost devoid of hydrogen. This suggests there are varied chemical evolution histories for the young stellar populations in IC 1613. Utilizing the flux-weighted gravity-luminosity relation, we determine IC 1613's distance modulus as m - M = 24.39 ± 0.11 mag. This value is in agreement within previous distance measurements using the near-infrared period-luminosity relationship of Cepheids and the tip of the red giant branch.