Stellar population of the blue compact dwarf galaxy SBS 1415+437 |
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| Authors: | T N Yakobchuk |
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| Institution: | (1) Main Astronomical Observatory, National Academy of Sciences of Ukraine, vul. Akademika Zabolotnoho 27, Kyiv, 03680, Ukraine |
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| Abstract: | The stellar population of the blue compact dwarf galaxy SBS 1415+437 is investigated using the archive database of the Hubble space telescope. The color index-magnitude diagram for stars reaches a magnitude of 29 m in the V and I bands. It comprises young main-sequence stars, blue and red supergiants, and the old population of red giant branch and asymptotic giant branch. The tip of the red giant branch αTRGB) was used to calculate the distance modulus, which turned out to be m ? M = 30.65 ± 0.08 m . The corresponding distance to the galaxy is D = 13.5 ± 1.0 Mpc. The youngest stars are distributed irregularly near the bright H II region in the southwest part of SBS 1415+437. The old population occupies a larger area, it is distributed more evenly and forms the galactic halo. The spatial distribution of young stars shows that the star formation in the galaxy spread in the direction from northeast to southwest over the last 5 × 107 yr with an average rate of 60 km/s. The TRGB of SBS 1415+437 was found to be appreciably shifted to the blue range: (V ? I) TRGB ≈ 1.30. The galaxy age turns out to be not smaller than the age of Galactic globular clusters (about 1010 yr), provided that the galaxy originally had a very low metallicity (our photometric estimate is Fe/H] = ?2.4). If the metallicity of SBS 1415+437 changed almost not at all in the course of evolution and was equal to Fe/H] = ?1.3 (as estimated from the emission lines of ionized gas), the galaxy age is no more than 2 × 109 yr. |
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