Deep Optical Observations of Compact Groups of Galaxies
Deep Optical Observations of Compact Groups of Galaxies
复制标题
致密星系群的深度光学观测
DOI：
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发表时间：
1995
期刊：
影响因子：
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通讯作者：
J. Schombert
中科院分区：
文献类型：
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作者：
R. Pildis;J. Bregman;J. Schombert
致密的星系群似乎极其密集，使它们很可能是星系强烈相互作用的场所，而它们的数量较少，使得它们的分析相对简单。为了寻找希克森致密群 (HCG) 中的漫射光和星系潮汐特征等光学相互作用示踪剂，我们对具有 $ROSAT$ 观测结果的 HCG 样本在三个滤光片中进行了深度光度测定。使用建模程序减去明亮的早期型星系的光，我们发现了许多（但不是全部）这些星系周围的外壳系统和扩展包络。我们的样本中只有一组，HCG 94，在组势中具有漫射光（光度为 7 L$^*$）；其他组在漫射光下不包含超过 1/3 L$^*$。除了 HCG 94（这是 X 射线发光的 HCG）之外，我们发现贝壳或其他潮汐特征的存在与群体的 X 射线发光度之间没有相关性。可检测的X射线群发射的更好预测因素是低螺旋分数并且属于较大的星系凝聚——这两者都与星系群中的光学扰动无关。两个椭圆星系在光学上极其明亮，但 X 射线微弱，被发现具有外壳和非常复杂的颜色结构。这可能是由于最近富含气体的物质进入星系，这会导致恒星轨道的破坏和大量恒星的形成。
Compact groups of galaxies appear to be extremely dense, making them likely sites of intense galaxy interaction, while their small populations make them relatively simple to analyze. In order to search for optical interaction tracers such as diffuse light and galaxy tidal features in Hickson compact groups (HCGs), we carried out deep photometry in three filters on a sample of HCGs with $ROSAT$ observations. Using a modeling procedure to subtract the light of bright early-type galaxies, we found shell systems and extended envelopes around many, but not all, of those galaxies. Only one group in our sample, HCG 94, has diffuse light in the group potential (with a luminosity of 7 L$^*$); the other groups do not contain more than 1/3 L$^*$ in diffuse light. With the exception of HCG 94 (which is the most X-ray--luminous HCG), we found no correlation between the presence of shells or other tidal features and the X-ray luminosity of a group. Better predictors of detectable group X-ray emission are a low spiral fraction and belonging to a larger galaxy condensation---neither of which are correlated with optical disturbances in the group galaxies. Two elliptical galaxies that are extremely optically luminous but X-ray--faint are found to have shells and very complex color structures. This is likely due to recent infall of gas-rich material into the galaxies, which would produce both the disruption of stellar orbits and a significant amount of star formation.