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arXiv 1004.3760astro-ph.CO
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NGC 7252模型中的动力驱动恒星形成

Dynamically-Driven Star Formation In Models Of NGC 7252

Li-Hsin Chien, Joshua Edward Barnes

备注：
11 pages, 9 figures, to be published in MNRAS
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摘要：

我们提出了新的动力学模型的合并残留物NGC 7252，其中包括恒星形成模拟根据各种唯象规则。通过使用交互式软件将我们的模型与观测到的形态和气体速度场进行匹配，我们得到了一个一致的NGC 7252动力学模型。在我们的模型中，这个原椭圆星系是由两个类似的富含气体的盘状星系合并而成的，这两个星系在大约6.2亿年前以大约2个盘尺度长度的初始近心分离落在一起。两种不同的恒星形成规则-密度依赖和冲击诱导-的结果表明，在第一次通过期间和之后的恒星形成有显着差异。冲击引起的恒星形成在第一次通过时产生迅速和广泛的星爆，而密度依赖的恒星形成预测一个更缓慢的上升和集中的星爆。观测到的星系团的分布和年龄与我们的模拟结果的比较，有利于在NGC 7252的恒星形成的冲击诱导机制。我们还提出了我们的模型的NGC 7252，通过将人口合成与辐射转移和尘埃衰减构造模拟彩色图像。总的来说，模型预测的震级和颜色与观测结果一致，尽管模拟的尾巴比观测到的更暗更红。我们认为，缺乏恒星形成的尾巴，反映了红色的颜色，是由于我们的模型中恒星形成的描述不完整，而不是尾巴中的气体不足。

英文摘要：

We present new dynamical models of the merger remnant NGC 7252 which include star formation simulated according to various phenomenological rules. By using interactive software to match our model with the observed morphology and gas velocity field, we obtain a consistent dynamical model for NGC 7252. In our models, this proto-elliptical galaxy formed by the merger of two similar gas-rich disk galaxies which fell together with an initial pericentric separation of ~2 disk scale lengths approximately 620 Myr ago. Results from two different star formation rules--- density-dependent and shock-induced--- show significant differences in star formation during and after the first passage. Shock-induced star formation yields a prompt and wide-spread starburst at the time of first passage, while density-dependent star formation predicts a more slowly rising and centrally concentrated starburst. A comparison of the distributions and ages of observed clusters with results of our simulations favors shock-induced mechanism of star formation in NGC 7252. We also present simulated color images of our model of NGC 7252, constructed by incorporating population synthesis with radiative transfer and dust attenuation. Overall the predicted magnitudes and colors of the models are consistent with observations, although the simulated tails are fainter and redder than observed. We suggest that a lack of star formation in the tails, reflected by the redder colors, is due to an incomplete description of star formation in our models rather than insufficient gas in the tails.

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