标题： (U)LIRGs在中红外波段的空间范围I：连续谱发射 显示英文标题

标题： The Spatial Extent of (U)LIRGs in the mid-Infrared I: The Continuum Emission

摘要： 我们基于利用斯皮策望远镜上的IRS获取的5-15微米低分辨率光谱，对“大天文台全天亮红外星系巡天”(GOALS)样本的扩展中红外(MIR)辐射进行了分析。我们计算了样本中星系的波长相关的扩展辐射比例FEE_lambda。我们可以识别出三种一般的FEE_lambda类型：一种是常数；一种是由于发射线和PAHs的特征比连续谱更扩展；第三种是深硅吸收位于9.7微米处的源的特性。超过30%的星系具有大于0.5的中值FEE_lambda，这意味着它们至少一半的MIR辐射是扩展的。发光红外星系(LIRGs)在它们的温暖尘埃连续谱中显示出广泛的FEE（0≤FEE_13.2um≤0.85）。我们在许多LIRGs中发现的大FEE_13.2um值表明它们的扩展MIR连续谱辐射起源于高达10kpc的尺度上。LIRGs在13.2微米处的核心平均大小为2.6kpc。然而，一旦系统的LIR达到约10^11.8Lsun的阈值，所有源都明显变得更紧凑，FEE_13.2um≤0.2，并且它们的核心是未分辨的。我们估计的ULIRGs核心大小上限小于1.5kpc。分析表明，在那些被归类为相互作用最后阶段合并的系统中，LIR>~10^11.25Lsun系统的紧凑性显著增加。FEE_13.2um也与活动星系核(AGN)对MIR的贡献有关。无论LIR如何，更多由AGN主导的星系较少扩展。最后，我们发现MIR连续谱辐射的扩展程度与远红外IRAS log(f_60um/f_100um)颜色相关。这使得我们可以对星系中可能产生冷尘埃辐射的区域设定一个下限，这一预测很快可以用赫歇尔空间望远镜来验证。 显示英文摘要

摘要： We present an analysis of the extended mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey (GOALS) sample based on 5-15um low resolution spectra obtained with the IRS on Spitzer. We calculate the fraction of extended emission as a function of wavelength for the galaxies in the sample, FEE_lambda. We can identify 3 general types of FEE_lambda: one where it is constant, one where features due to emission lines and PAHs appear more extended than the continuum, and a third which is characteristic of sources with deep silicate absorption at 9.7um. More than 30% of the galaxies have a median FEE_lambda larger than 0.5 implying that at least half of their MIR emission is extended. Luminous Infrared Galaxies (LIRGs) display a wide range of FEE in their warm dust continuum (0<=FEE_13.2um<=0.85). The large values of FEE_13.2um that we find in many LIRGs suggest that their extended MIR continuum emission originates in scales up to 10kpc. The mean size of the LIRG cores at 13.2um is 2.6kpc. However, once the LIR of the systems reaches the threshold of ~10^11.8Lsun, all sources become clearly more compact, with FEE_13.2um<=0.2, and their cores are unresolved. Our estimated upper limit for the core size of ULIRGs is less than 1.5kpc. The analysis indicates that the compactness of systems with LIR>~10^11.25Lsun strongly increases in those classified as mergers in their final stage of interaction. The FEE_13.2um is also related to the contribution of an active galactic nucleus (AGN) to the MIR. Galaxies which are more AGN-dominated are less extended, independently of their LIR. We finally find that the extent of the MIR continuum emission is correlated with the far-IR IRAS log(f_60um/f_100um) color. This enables us to place a lower limit to the area in a galaxy from where the cold dust emission may originate, a prediction which can be tested soon with the Herschel Space Telescope.