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arXiv 1004.3933astro-ph.CO
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发光和超亮红外星系II的VLT-VIMOS积分场光谱学。在相互作用和合并的LIRGs核外区域潮汐力引起的激波电离的证据

VLT-VIMOS integral field spectroscopy of luminous and ultraluminous infrared galaxies II. Evidence for shock ionization caused by tidal forces in the extra-nuclear regions of interacting and merging LIRGs

Ana Monreal-Ibero, Santiago Arribas, Luis Colina, Javier Rodriguez-Zaurin, Almudena Alonso-Herrero, Macarena Garcia-Marin

摘要:

LIRGs是低z宇宙中一类重要的天体,它介于正常的螺旋星系和强相互作用和恒星爆发的ULIRG之间。目前还缺乏对它们的二维物理性质的研究。我们的目标是理解的本质和起源的电离机制在LIRGs的双核区域作为一个功能的相互作用相和L_IR通过使用IFS数据获得的VIMOS。我们的分析基于32个LIRG的25300多个光谱,涵盖了所有类型的形态和整个10^11-10^12 L太阳范围。我们发现了强有力的证据,与系统的动力学状态的明显趋势。具体来说,我们量化的变化与相互作用的相位的几个线的比率表示的兴奋程度。虽然[NII]/Ha比率没有显示任何显著变化,但[SII]/Ha和[OI]/Ha比率在更高级的相互作用阶段更高。我们用诊断图约束了引起核外区电离的主要机制。孤立系主要与年轻恒星引起的电离相一致。在相互作用对和更先进的合并中,大部分核外区域与激波引起的电离一致。这是支持的激发度和电离气体的速度色散之间的关系,我们解释为证据的相互作用的星系和先进的合并,但不是在孤立的星系中的激波电离。这种关系与LIR没有任何依赖关系,说明引潮力在核外区电离激波的起源中起着关键作用。我们还显示了什么似乎是一个共同的[OI]/Ha-sigma关系的相互作用(U)LIRGs的双核电离气体。这需要用更大的ULIRG样本进一步研究。

英文摘要:

LIRGs are an important class of objects in the low-z universe bridging the gap between normal spirals and the strongly interacting and starbursting ULIRGs. Studies of their 2D physical properties are still lacking. We aim to understand the nature and origin of the ionization mechanisms operating in the extranuclear regions of LIRGs as a function of the interaction phase and L_IR by using IFS data obtained with VIMOS. Our analysis is based on over 25300 spectra of 32 LIRGs covering all types of morphologies and the entire 10^11-10^12 L_sun range. We found strong evidence for shock ionization, with a clear trend with the dynamical status of the system. Specifically, we quantified the variation with interaction phase of several line ratios indicative of the excitation degree. While the [NII]/Ha ratio does not show any significant change, the [SII]/Ha and [OI]/Ha ratios are higher for more advanced interaction stages. We constrained the main mechanisms causing the ionization in the extra-nuclear regions using diagnostic diagrams. Isolated systems are mainly consistent with ionization caused by young stars. Large fractions of the extra-nuclear regions in interacting pairs and more advanced mergers are consistent with ionization caused by shocks. This is supported by the relation between the excitation degree and the velocity dispersion of the ionized gas, which we interpret as evidence for shock ionization in interacting galaxies and advanced mergers but not in isolated galaxies. This relation does not show any dependence with L_IR. All this indicates that tidal forces play a key role in the origin of the ionizing shocks in the extra-nuclear regions. We also showed what appears to be a common [OI]/Ha-sigma relation for the extranuclear ionized gas in interacting (U)LIRGs. This needs to be investigated further with a larger sample of ULIRGs.

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