Asymptotic giant branch stars in the Phoenix dwarf galaxy |
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| Authors: | John Menzies Michael Feast Patricia Whitelock Enrico Olivier Noriyuki Matsunaga Gary Da Costa |
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| Institution: | South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa;Astronomy Department, University of Cape Town, 7701 Rondebosch, South Africa;National Astrophysics and Space Science Programme, Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch, South Africa;Department of Physics, University of the Western Cape, Private Bag X17, 7535 Bellville, South Africa;Department of Astronomy, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Kyoto 606-8502, Japan;Research School of Astronomy and Astrophysics, Australian National University, Mount Stromlo Observatory, Weston Creek, ACT 2611, Australia |
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| Abstract: | JHK s near-infrared photometry of stars in the Phoenix dwarf galaxy is presented and discussed. Combining these data with the optical photometry of Massey et al. allows a rather clean separation of field stars from Phoenix members. The discovery of a Mira variable ( P = 425 d), which is almost certainly a carbon star, leads to an estimate of the distance modulus of 23.10 ± 0.18 that is consistent with other estimates and indicates the existence of a significant population of age ～2 Gyr. The two carbon stars of Da Costa have M bol=?3.8 and are consistent with belonging to a population of similar age; some other possible members of such a population are identified. A Da Costa non-carbon star is Δ K s～ 0.3 mag brighter than these two carbon stars. It may be an asymptotic giant branch star of the dominant old population. The nature of other stars lying close to it in the K s, ( J ? K s) diagram needs studying. |
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| Keywords: | stars: AGB and post-AGB stars: carbon galaxies: dwarf galaxies: stellar content |
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