Lynx-Cancer空星系的研究--V.极端孤立星系UGC4722
Study of the Lynx-Cancer void galaxies-V. The extremely isolated galaxy UGC4722
摘要：
本文详细研究了位于Lynx-Cancer空洞附近的Sdm星系UGC 4722（M_B = -17.4）。UGC 4722是孤立星系目录中的一员，也被认为是本超星系团中最孤立的星系之一。然而，该星系的光学图像显示，它有一个独特的形态，具有一个细长的~ 14 kpc长的羽状物。俄罗斯6米望远镜（BTA）和巨型米波射电望远镜（GMRT）对UGC 4722中电离和中性气体的新观测揭示了该系统扰动形态的第二个组成部分。这是一颗小的、几乎完全被破坏的、富含气体的矮星（M_B =-15.2，M_HI/L_B ~4.3）。我们估计这两个星系的氧丰度为12+log（O/H）~ 7.5-7.6，这比在致密环境中类似星系的光度-金属丰度关系所预期的要低2-3倍。从斯隆数字巡天（SDSS）图像中获得的羽状物的ugr颜色与星暴后年龄为0.45-0.5 Gyr的简单恒星星族一致。因此，这个系统似乎是第一个已知的情况下，一个突出的潮汐特征组成的年轻恒星星族的小合并。
英文摘要：
We present a detailed study of the extremely isolated Sdm galaxy UGC4722 (M_B = -17.4) located in the nearby Lynx-Cancer void. UGC4722 is a member of the catalogue of isolated galaxies, and has also been identified as one of the most isolated galaxies in the Local Supercluster. Optical images of the galaxy however show that it has a peculiar morphology with an elongated ~ 14 kpc long plume. New observations with the Russian 6-m telescope (BTA) and the Giant Metrewave Radio Telescope (GMRT) of the ionised and neutral gas in UGC4722 reveal the second component responsible for the disturbed morphology of the system. This is a small, almost completely destroyed, very gas-rich dwarf (M_B = -15.2, M_HI/L_B ~4.3). We estimate the oxygen abundance for both galaxies to be 12+log(O/H) ~ 7.5-7.6, which is 2-3 times lower than what is expected from the luminosity-metallicity relation for similar galaxies in denser environments. The ugr colours of the plume derived from Sloan Digital Sky Survey (SDSS) images are consistent with a simple stellar population with a post starburst age of 0.45-0.5 Gyr. This system hence appears to be the first known case of a minor merger with a prominent tidal feature consisting of a young stellar population.
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