ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. IV. DISTANCE MEASUREMENT FROM LBT OPTICAL IMAGING
ALFALFA DISCOVERY OF THE NEARBY GAS-RICH DWARF GALAXY LEO P. IV. DISTANCE MEASUREMENT FROM LBT OPTICAL IMAGING
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DOI：
10.1088/0004-6256/146/6/145
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发表时间：
2013-12-01
影响因子：
5.3
通讯作者：
Rhode, Katherine L.
中科院分区：
文献类型：
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作者：
McQuinn, Kristen B. W.;Skillman, Evan D.;Rhode, Katherine L.
Leo P 是通过盲目的 H I Arecibo Legacy Fast ALFA 巡天发现的低光度矮星系。 H I 和后续光学观测表明，Leo P 是一个富含气体的矮星系，具有活跃的恒星形成和潜在的老年群体，以及极低的氧丰度。在这里，我们通过应用红巨星分支尖端 (TRGB) 距离方法来测量新大型双目望远镜 V 和 I 波段成像中已分辨恒星群的光度，从而测量到 Leo P 的距离。我们测量的距离模数为 26.19(-0.50)(+0.17) mag，对应于 1.72(-0.40)(+0.14) Mpc 的距离。尽管我们的测光达到比 TRGB 低 3 星等，但红巨星分支的稀疏性在距离下限上产生了更高的不确定性。 Leo P 位于本地群之外，其距离和速度与本地哈勃流一致。虽然位于密度非常低的环境中，Leo P 位于矮星系松散关联的约 0.5 Mpc 范围内，其中包括 NGC 3109、Antlia、Sextans A 和 Sextans B，并且距其下一个最近的邻居 Leo A 1.1 Mpc。Leo P 是附近宇宙中已知金属丰度最低的恒星形成星系之一，其金属丰度可与 I Zw 18 和 DDO 相媲美 68，但具有与本地体积中的矮球状体 (dSphs) 类似的恒星特征，例如船底座、六分仪和狮子座二号。鉴于其物理特性和隔离性，Leo P 可能提供富含气体的矮不规则星系和落入本星系群环境并被剥离气体的 dSph 之间的演化联系。
Leo P is a low-luminosity dwarf galaxy discovered through the blind H I Arecibo Legacy Fast ALFA survey. The H I and follow-up optical observations have shown that Leo P is a gas-rich dwarf galaxy with both active star formation and an underlying older population, as well as an extremely low oxygen abundance. Here, we measure the distance to Leo P by applying the tip of the red giant branch (TRGB) distance method to photometry of the resolved stellar population from new Large Binocular Telescope V and I band imaging. We measure a distance modulus of 26.19(-0.50)(+0.17) mag corresponding to a distance of 1.72(-0.40)(+0.14) Mpc. Although our photometry reaches 3 mag below the TRGB, the sparseness of the red giant branch yields higher uncertainties on the lower limit of the distance. Leo P is outside the Local Group with a distance and velocity consistent with the local Hubble flow. While located in a very low-density environment, Leo P lies within similar to 0.5 Mpc of a loose association of dwarf galaxies which include NGC 3109, Antlia, Sextans A, and Sextans B, and 1.1 Mpc away from its next nearest neighbor, Leo A. Leo P is one of the lowest metallicity star-forming galaxies known in the nearby universe, comparable in metallicity to I Zw 18 and DDO 68, but with stellar characteristics similar to dwarf spheriodals (dSphs) in the Local Volume such as Carina, Sextans, and Leo II. Given its physical properties and isolation, Leo P may provide an evolutionary link between gas-rich dwarf irregular galaxies and dSphs that have fallen into a Local Group environment and been stripped of their gas.