Mon. Not. R. Astron. Soc., 425, 709-719 (2012/September-1)
A unique isolated dwarf spheroidal galaxy at D=1.9Mpc.
MAKAROV D., MAKAROVA L., SHARINA M., UKLEIN R., TIKHONOV A., GUHATHAKURTA P., KIRBY E. and TEREKHOVA N.
Abstract (from CDS):
We present a photometric and spectroscopic study of the unique isolated nearby dwarf spheroidal (dSph) galaxy KKR25. The galaxy was resolved into stars with Hubble Space Telescope
/Wide Field Planetary Camera 2 including old red giant branch and red clump. We have constructed a model of the resolved stellar populations and measured the star formation rate and metallicity as a function of time. The main star formation activity period occurred about 12.6–13.7 Gyr ago. These stars are mostly metal poor, with a mean metallicity [Fe/H] ∼ -1 to -1.6 dex. About 60per cent of the total stellar mass was formed during this event. There are indications of intermediate-age star formation in KKR25 between 1 and 4 Gyr with no significant signs of metal enrichment for these stars. Long-slit spectroscopy was carried out using the Russian 6-m telescope of the integrated starlight and bright individual objects in the galaxy. We have discovered a planetary nebula (PN) in KKR25. This is the first known PN in a dSph galaxy outside the Local Group. We have measured its oxygen abundance 12 + log(O/H) = 7.60±0.07 dex and a radial velocity Vh
= -79 km/s. We have analysed the stellar density distribution in the galaxy body. The galaxy has an exponential surface brightness profile with a central light depression. We discuss the evolutionary status of KKR25, which belongs to a rare class of very isolated dwarf galaxies with spheroidal morphology.
2012 The Authors Monthly Notices of the Royal Astronomical Society 2012 RAS
galaxies: distances and redshifts - galaxies: dwarf - galaxies: individual: KKR25 - galaxies: stellar content
Fig. 2, Table 5: [MMS2012b] N (Nos 1-4).
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