标题： 星系合并中的恒星形成历史 显示英文标题

标题： Star Formation History In Merging Galaxies

摘要： 星系相互作用被认为会触发恒星爆发。在相互作用星系和合并星系中形成的年轻大质量星团可能成为年轻的球状星团。这些星团的年龄可以提供关于由相互作用触发事件的时间线索，从而提供一种重建合并星系恒星形成历史的重要方法。星系合并的数值模拟可以采用不同的恒星形成规则。例如，依赖于气体密度的恒星形成或由冲击波触发的恒星形成，预测出显著不同的恒星形成历史。为了验证这些模型的有效性，多目标光谱学被用来绘制一系列处于不同阶段（Arp 256、NGC 7469、NGC 4676、Arp 299、IC 883 和 NGC 2623）的星系合并中星团的年龄。我们发现，随着合并阶段的推进，年龄累积分布变得越来越浅。这一结果表明星团年龄与合并阶段之间存在趋势关系。在 NGC 4676 中，我们发现了两个大约 170 Myr 的星团，这表明它们很可能是在第一次通过时形成的。它们在潮汐尾中的位置与冲击诱导模型所预测的恒星形成空间分布一致。当我们将 NGC 7252 中星团的年龄和空间分布与我们的模型进行比较时，我们发现一些星团可能是在第一次通过时由冲击诱导的恒星爆发形成的，正如冲击诱导恒星形成模拟所预测的那样。这些模拟表明，冲击诱导机制是恒星形成的重要触发因素，并且使用爆发中形成的星团的年龄可以有效地确定合并星系的恒星形成历史。 显示英文摘要

摘要： Galaxy interactions are known to trigger starbursts. Young massive star clusters formed in interacting galaxies and mergers may become young globular clusters. The ages of these clusters can provide clues about the timing of interaction-triggered events, and thus provide an important way to reconstruct the star formation history of merging galaxies. Numerical simulations of galaxy mergers can implement different star formation rules. For instance, star formation dependent on gas density or triggered by shocks, predicts significantly different star formation histories. To test the validity of these models, multi-object spectroscopy was used to map the ages of young star clusters throughout the bodies and tails of a series of galaxy mergers at different stages (Arp 256, NGC 7469, NGC 4676, Arp 299, IC 883 and NGC 2623). We found that the cumulative distribution of ages becomes shallower as the stage of merger advances. This result suggests a trend of cluster ages as a function of merger stage. In NGC 4676 we found that two clusters have ages of about 170 Myr, suggesting that they likely formed during its first passage. Their locations in the tidal tails are consistent with the spatial distribution of star formation predicted by shock-induced models. When comparing the ages and spatial distribution of clusters in NGC 7252 to our model, we found that some clusters are likely to form during the prompt starburst at first passage, as predicted by simulations with shock-induced star formation. These simulations show that the shock-induced mechanism is an important trigger of star formation and that using the ages of clusters formed in the starbursts can effectively determine the star formation history of merging galaxies.