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Globular clusters in low mass galaxies

机译：球形簇在低质量星系中

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We study properties of globular cluster candidates (GCCs) and the diffuse stellar populations in nearby low surface brightness dwarf galaxies, using HST WFPC2 photometry in the V and I bands. Our sample consists of 18 dwarf spheroidal (dSph), 36 dwarf irregular (dlrr), and 3 transition-type galaxies, with projected linear diameters less than 3.5 kpc and mean blue surface brightness > 23 mag/arcsec~2 situated at the distance 2-6 Mpc in the field and in nearby groups. Our sample dwarf spheroidal galaxies were not detected in HI and are located at the distances of up to Mpc away from a nearby bright galaxy. Transition-type galaxies, which are distributed like dSph galaxies, form a very rare class of galaxies. dlrr galaxies show a weaker concentration to the nearest massive neighbors than dSph and transition-type galaxies. At a given surface brightness and luminosity, they exhibit lower mean metallicities than dSphs. In contrast to dlrr galaxies, the majority of dSph galaxies at a similar mean surface brightness contains GCCs. The percentage of GCCs located near the centers of dSph galaxies is much higher than that for dlrr galaxies. The composite population of GCCs in dSphs is spatially more concentrated than in dlrr galaxies. The color distributions of GCCs in dSph and dlrr galaxies show major differences. While the latter shows obvious bimodality with the peaks near (V-I)0.5 and~1.0mag, the GCC color distribution in dSph galaxies shows only one peak with a mean color (V - I)_o~1.0 mag. There is a tendency of increasing half-light radii with increasing projected galactocentric distances for a large number of GCCs in dSph galaxies, which is also observed in the Galactic globular cluster system. We embarked on a spectroscopic survey of GCCs in low-mass galaxies to obtain their chemical compositions and relative ages.
机译：我们在VST WFPC2测光法中研究了附近的低表面亮度矮化星系中球状候选人（GCC）和漫射恒星种群的属性，在V和I带中使用HST WFPC2测光。我们的样品由18个矮小的球形（DSPH），36个矮小不规则（DLRR）和3个过渡型星系组成，具有小于3.5 kPc的投影线性直径，平均蓝色表面亮度> 23 mag / arcsec〜2位于距离2 -6 MPC在现场和附近的群体中。我们的样品矮小的球形星系未在嗨检测到，并且位于高达MPC的距离远离附近的明亮星系。过渡型星系，分布式DSPH星系，形成一个非常罕见的星系类。 DLRR星系表现出比DSPH和过渡型星系最近的巨大邻居较弱的浓度。在给定的表面亮度和发光度下，它们表现出低于DSPH的平均金属。与DLR星系相比，类似平均表面亮度的大多数DSPH星系包含GCC。位于DSPH星系中心附近的GCC百分比远高于DLRR星系的中心。在DSPH中的GCCS的复合人群在空间上比DLR星系更集中。在DSPH和DLR星系中的GCCS的颜色分布显示出主要的差异。虽然后者与靠近（V-1）的峰值显示出明显的双极性，但DSPH星系中的GCC颜色分布仅显示一个具有平均颜色（V - I）_O〜1.0 mag的一个峰。随着在DSPH星系中的大量GCC的增加，增加了半光线半径的趋势，在DSPH星系中也观察到在半乳液球状群体系统中也观察到的大量GCC。我们踏上了对低质量星系中GCCs的光谱调查，以获得其化学成分和相对年龄。

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