SPECTROSCOPIC CONFIRMATION OF THE DWARF GALAXIES HYDRA II AND PISCES II AND THE GLOBULAR CLUSTER LAEVENS 1
SPECTROSCOPIC CONFIRMATION OF THE DWARF GALAXIES HYDRA II AND PISCES II AND THE GLOBULAR CLUSTER LAEVENS 1
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DOI：
10.1088/0004-637x/810/1/56
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发表时间：
2015-06
期刊：
影响因子：
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通讯作者：
E. Kirby;J. Simon;J. Cohen
中科院分区：
文献类型：
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作者：
E. Kirby;J. Simon;J. Cohen
我们目前凯克/DEIMOS光谱的恒星在最近发现的银河系卫星九头蛇II，双鱼座II，和Laevens 1。我们测得的速度色散为5.4 − 2.4 + 3.6？对于双鱼座II，我们的速度弥散为km s−1，但我们没有解决Hydra II或Laevens 1的速度弥散。我们勉强解决了Hydra II和Pisces II的金属丰度分散，但不是Laevens 1。此外，长蛇座II和双鱼座II符合银河系矮星系的光度-金属丰度关系（δ [ Fe / H ]=-2.02 ± 0.08？>和-2.45 ± 0.07？，而Laevens 1则没有（δ [ Fe / H ]=-1.68 ± 0.05？> ).运动学和化学性质表明，Hydra II和Pisces II是矮星系，而Laevens 1是一个球状星团。我们确定了之前观测到的两颗靠近Laevens 1中心的蓝色恒星不是该星团的成员。第三颗蓝色星星的成员身份不明确。Hydra II的径向速度为303.1 ± 1.4？km s−1，类似于麦哲伦流的主导臂。双鱼座II的质光比为370 − 240 + 310 M/ L。.它不是最暗物质主导的矮星系之一，但它仍然值得列入寻找暗物质自湮灭的伽马射线。
We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of 5.4 − 2.4 + 3.6 ?> km s−1 for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity–metallicity relation for Milky Way dwarf galaxies ( ⟨ [ Fe / H ] ⟩ = - 2.02 ± 0.08 ?> and - 2.45 ± 0.07 ?> , respectively), whereas Laevens 1 does not ( ⟨ [ Fe / H ] ⟩ = - 1.68 ± 0.05 ?> ). The kinematic and chemical properties suggest that Hydra II and Pisces II are dwarf galaxies, and Laevens 1 is a globular cluster. We determined that two of the previously observed blue stars near the center of Laevens 1 are not members of the cluster. A third blue star has ambiguous membership. Hydra II has a radial velocity ⟨ v helio ⟩ = 303.1 ± 1.4 ?> km s−1, similar to the leading arm of the Magellanic stream. The mass-to-light ratio for Pisces II is 370 − 240 + 310 M ☉ / L ☉ ?> . It is not among the most dark matter-dominated dwarf galaxies, but it is still worthy of inclusion in the search for gamma-rays from dark matter self-annihilation.