H I Studies of the Sculptor Group Galaxies. VIII. The Background Galaxies: NGC 24 and NGC 45
H I Studies of the Sculptor Group Galaxies. VIII. The Background Galaxies: NGC 24 and NGC 45
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H I 玉夫座星系研究。
DOI：
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发表时间：
1988
期刊：
影响因子：
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通讯作者：
K. Freeman
中科院分区：
文献类型：
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作者：
L. Chemin;C. Carignan;N. Drouin;K. Freeman
为了完成我们对玉夫座星系群的H I巡天，本文介绍了对NGC 24和NGC 45的甚大阵观测。这两个类似星等的星系MB <$-17.4位于玉夫座星系群的背景中，是低表面亮度星系，特别是NGC 45。NGC 24的H I分布和运动学是规则的，而NGC 45的长轴呈现运动学扭曲。倾斜环模型表明长轴的位置角改变了0.25 °。一个最佳拟合的质量分布模型给出了NGC 24和NGC 45的恒星盘的质光比分别为2.5和5.2。这些值高于恒星人口合成模型的预期。尽管暗物质的贡献很大，星系质量仍然主要由内部区域的恒星组成。这些高的质光比是低表面亮度星系的典型特征，可能表明在这些星系中，盘远离最大盘的情况。因此，从最佳拟合模型导出的晕圈参数是下限。
In order to complete our H I survey of galaxies in the Sculptor group area, Very Large Array observations of NGC 24 and NGC 45 are presented. These two galaxies of similar magnitude, MB ∼ -17.4, lie in the background of the Sculptor group and are low surface brightness galaxies, especially NGC 45. The H I distribution and kinematics are regular for NGC 24, while NGC 45 exhibits a kinematical twist of its major axis. A tilted-ring model shows that the position angle of the major axis changes by ∼25°. A best-fit model of their mass distributions gives mass-to-light ratios for the stellar disk of 2.5 and 5.2 for NGC 24 and NGC 45, respectively. These values are higher than those expected from stellar population synthesis models. Despite the large dark matter contribution, the galaxy mass is still dominated by the stellar component in their very inner regions. These high mass-to-light ratios are typical of what is seen in low surface brightness galaxies and may indicate that, in those galaxies, disks are far from the maximum disk case. The halo parameters derived from the best-fit models are thus lower limits.