碰撞碎片中的恒星形成：从它们的光谱能量分布模型中获得的启示
Star Formation in Collision Debris: Insights from the modeling of their Spectral Energy Distribution
摘要：
在星系与星系的相互作用过程中，大量的气体云可以注入星系际介质，而星系际介质又会受到引力的束缚，坍缩并形成恒星、星团甚至矮星系。从这个过程中产生的物体都是“原始的”，因为它们正在形成它们的第一代恒星，并且化学进化，因为从它们的母星系继承的金属丰度很高。这些特性使它们成为研究恒星形成的特别有趣的实验室。在研究了它们的恒星形成特性之后，我们使用光球，星云和尘埃模型来分析它们的光谱能量分布（SED），从远紫外到中红外区域的7个恒星形成区域的样本。我们的分析证实，斯蒂芬五重星系中的星系际恒星形成区，在Arp 105和NGC 5291周围，似乎没有年龄超过10^9年的恒星星族。我们还发现了过量的光在近红外区（从2到4.5微米），这不能归因于恒星光球或星云的贡献。这种过量与恒星形成率强度相关，这表明它可能是由于温度波动的非常小的颗粒以及3.3微米处的多环芳烃（PAH）线的排放。将通过巴耳末衰减的衰减与中红外发射进行比较允许我们检查衰减估计的可靠性。这表明在NGC 5291和NGC 7252中存在嵌入式恒星形成区。总的来说，碰撞碎片（和潮汐矮星系）中恒星形成区的SED更像是星系盘中尘埃恒星形成区，而不是典型的恒星形成矮星系。
英文摘要：
During galaxy-galaxy interactions, massive gas clouds can be injected into the intergalactic medium which in turn become gravitationally bound, collapse and form stars, star clusters or even dwarf galaxies. The objects resulting from this process are both "pristine", as they are forming their first generation of stars, and chemically evolved because the metallicity inherited from their parent galaxies is high. Such characteristics make them particularly interesting laboratories to study star formation. After having investigated their star-forming properties, we use photospheric, nebular and dust modeling to analyze here their spectral energy distribution (SED) from the far-ultraviolet to the mid-infrared regime for a sample of 7 star-forming regions. Our analysis confirms that the intergalactic star forming regions in Stephan's Quintet, around Arp 105, and NGC 5291, appear devoid of stellar populations older than 10^9 years. We also find an excess of light in the near-infrared regime (from 2 to 4.5 microns) which cannot be attributed to stellar photospheric or nebular contributions. This excess is correlated with the star formation rate intensity suggesting that it is probably due to emission by very small grains fluctuating in temperature as well as the polycyclic aromatic hydrocarbons (PAH) line at 3.3 micron. Comparing the attenuation via the Balmer decrement to the mid-infrared emission allows us to check the reliability of the attenuation estimate. It suggests the presence of embedded star forming regions in NGC 5291 and NGC 7252. Overall the SED of star-forming regions in collision debris (and Tidal Dwarf Galaxies) resemble more that of dusty star-forming regions in galactic disks than to that of typical star-forming dwarf galaxies.
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