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首页> 外文期刊>The Astrophysical journal >A HST STUDY OF THE STELLAR POPULATIONS IN THE COMETARY DWARF IRREGULAR GALAXY NGC 2366
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A HST STUDY OF THE STELLAR POPULATIONS IN THE COMETARY DWARF IRREGULAR GALAXY NGC 2366

机译：彗星矮人不规则星系NGC 2366中恒星种群的HST研究

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摘要

We present V and I photometry of the resolved stars in the cometary dwarf irregular galaxy NGC 2366, using Wide Field Planetary Camera 2 images obtained with the Hubble Space Telescope. The resulting color-magnitude diagram reaches down to I ～ 26.0 mag. It reveals not only a young population of blue main-sequence stars (age approx< 30 Myr) but also an intermediate-age population of blue and red supergiants (20 Myr approx< age approx < 100 Myr) and older evolved populations of asymptotic giant branch (AGB) stars (age approx> 100 Myr) and red giant branch (RGB) stars (age approx>1 Gyr). The measured magnitude I = 23.65 ± 0.10 mag of the RGB tip results in a distance modulus m - M = 27.67 ±0.10, which corresponds to a distance of 3.42 ±0.15 Mpc, in agreement with previous distance determinations. The youngest stars are associated with the bright complex of H Ⅱ regions NGC 2363 (=Mrk 71) in the southwest extremity of the galaxy. As a consequence of the diffusion and relaxation processes of stellar ensembles, the older the stellar population is, the smoother and more extended is its spatial distribution. An underlying population of older stars is found throughout the body of NGC 2366. The most notable feature of this older population is the presence of numerous relatively bright AGB stars. The number ratio of AGB to RGB stars and the average absolute brightness of AGB stars in NGC 2366 are appreciably higher than in the BCD Ⅶ Zw 403, indicating a younger age of the AGB stars in NGC 2366. In addition to the present burst of age approx< 100 Myr, there has been strong star formation activity in the past of NGC 2366, from ～ 100 Myr to approx< 3 Gyr ago.
机译：我们使用哈勃太空望远镜获得的广角行星相机2图像，提出了彗星矮星不规则星系NGC 2366中已分辨恒星的V和I光度法。生成的色度图下降到I〜26.0 mag。它不仅揭示了年轻的蓝色主序星群体（年龄约<30 Myr），而且还揭示了中年的蓝色和红色超巨星群体（20 Myr约100 Myr年龄）以及年龄较大的渐近巨星演化群体。分支（AGB）星（年龄约> 100迈尔）和红色巨型分支（RGB）星（年龄约> 1 Gyr）。 RGB笔尖的测量大小I = 23.65±0.10 mag，导致距离模数m-M = 27.67±0.10，对应于3.42±0.15 Mpc的距离，与先前的距离确定一致。最年轻的恒星与银河系西南端HⅡ区NGC 2363（= Mrk 71）的明亮复合体有关。由于恒星集合体的扩散和弛豫过程，恒星种群越老，其空间分布就越平滑和扩展。在NGC 2366的整个身体中发现了潜在的较老恒星群。这一较老群的最显着特征是存在大量相对明亮的AGB恒星。 NGC 2366中AGB与RGB恒星的数量比以及AGB恒星的平均绝对亮度明显高于BCDⅦZw 403，这表明NGC 2366中AGB恒星的年龄更年轻。大约<100 Myr，从〜100 Myr到大约<3 Gyr以前，NGC 2366一直有很强的恒星形成活动。

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