狮子座环的碰撞起源
A collisional origin for the Leo ring
摘要：
星系周围的扩展HI结构对于探测星系形成的情况是非常重要的。狮子座群中的巨大HI环是附近宇宙中最大和最有趣的HI结构之一。它是否由原始气体组成，如明显缺乏任何光学对应物和缺乏与附近星系的明显物理联系所暗示的那样，或者是在碰撞中从星系中排出的气体，这是一个积极的争论。我们提出了深宽视场的CFHT上的MegaCam获得的环区域的光学图像。它们揭示了沿着环的几个HI和UV凝聚的光学对应物，在g '，r'和i'波段，这可能对应于气体环内形成的恒星协会。分析这些恒星形成区之一的光谱能量分布，我们发现它是典型的恒星形成区在前富集潮汐碎片。然后，我们使用模拟来测试的假设，狮子座环的结果从狮子座集团成员NGC 3384和M96之间的正面碰撞。根据我们的模型，这是能够解释，至少定性地说，该系统的主要观测特性，狮子座环是一致的碰撞环。因此，这可能是另一个由预富集的碰撞碎片组成的扩展星系际气体的例子。
英文摘要：
Extended HI structures around galaxies are of prime importance to probe galaxy formation scenarios. The giant HI ring in the Leo group is one of the largest and most intriguing HI structures in the nearby Universe. Whether it consists of primordial gas, as suggested by the apparent absence of any optical counterpart and the absence of an obvious physical connection to nearby galaxies, or of gas expelled from a galaxy in a collision is actively debated. We present deep wide field-of-view optical images of the ring region obtained with MegaCam on the CFHT. They reveal optical counterparts to several HI and UV condensations along the ring, in the g', r', and i' bands, which likely correspond to stellar associations formed within the gaseous ring. Analyzing the spectral energy distribution of one of these star-forming regions, we found it to be typical for a star-forming region in pre-enriched tidal debris. We then use simulations to test the hypothesis that the Leo ring results from a head-on collision between Leo group members NGC 3384 and M96. According to our model which is able to explain, at least qualitatively, the main observational properties of the system, the Leo ring is consistent with being a collisional ring. It is thus likely another example of extended intergalactic gas made-up of pre-enriched collisional debris.
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