低z（U）LIRGs中的核外α发射复合物：潮汐矮星系的前兆？
Extranuclear Halpha-emitting complexes in low-z (U)LIRGs: Precursors of tidal dwarf galaxies?
摘要：
本文描述了（U）LIRGs外部大质量恒星形成区的物理和运动学性质。我们使用HST B和I波段的高角分辨率ACS图像，以及IFS获得的Halpha线发射图。我们在11个（U）LIRGs中发现了31个外部的α发射（年轻恒星形成）复合体。这些复合体一般具有类似的大小，光度和金属丰度的河外巨HII地区和TDG候选人中发现的亮度较低的合并和紧凑的星系群。我们评估的质量含量和生存的可能性，TDGs的22个复杂的HST图像中的简单结构的基础上，他们的光度，结构和运动学特性。所使用的动力学示踪剂（半径-西格玛和光度-西格玛图）表明，大多数复合物可能是自引力实体。通过考虑候选星系的潮汐质量及其相对于母星系的相对速度，研究了母星系对力的抵抗力。结合以前的研究结果TDG搜索ULIRGs的9个复合体满足大多数应用的标准，从而显示出高，中等或高的生存可能性，他们的总质量可能是兼容的矮星系。他们被定义为TDG候选人。我们建议，他们可能更经常形成的早期阶段的相互作用。将复合物的所有数据与IFS数据相结合，其中覆盖了系统的显著部分，我们推断出TDG生产率为0.3，每个系统的存活概率最高。然而，对于寿命较长的TDG来说，在（U）LIRG中的系统进化了10 Gyr之后，这个比率可能会下降到0.1，这意味着不超过5- 10%的侏儒种群可能是潮汐起源的。
英文摘要：
(Abridged)This paper characterizes the physical and kinematic properties of external massive star-forming regions in a sample of (U)LIRGs. We use high angular resolution ACS images from the HST B and I bands, as well as Halpha-line emission maps obtained with IFS. We find 31 external Halpha-emitting (young star-forming) complexes in 11 (U)LIRGs. These complexes have in general similar sizes, luminosities, and metallicities to extragalactic giant HII regions and TDG candidates found in less luminous mergers and compact groups of galaxies. We assess the mass content and the likelihood of survival as TDGs of the 22 complexes with simple structures in the HST images based on their photometric, structural, and kinematic properties. The dynamical tracers used (radius-sigma and luminosity-sigma diagrams) indicate that most of the complexes might be self-gravitating entities. The resistance to forces from the parent galaxy is studied by considering the tidal mass of the candidate and its relative velocity with respect to the parent galaxy. After combining the results of previous studies of TDG searches in ULIRGs a total of 9 complexes satisfy most of the applied criteria and thus show a high-medium or high likelihood of survival, their total mass likely being compatible with that of dwarf galaxies. They are defined as TDG candidates. We propose that they probably formed more often during the early phases of the interaction. Combining all data for complexes with IFS data where a significant fraction of the system is covered, we infer a TDG production rate of 0.3 candidates with the highest probabilities of survival per system for the (U)LIRGs class. This rate, though, might decrease to 0.1 after the systems in (U)LIRGs have evolved for 10 Gyr, for long-lived TDGs, which would imply that no more than 5-10 % of the overall dwarf population could be of tidal origin.
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