THE SPATIAL EXTENT OF (U)LIRGs IN THE MID-INFRARED. I. THE CONTINUUM EMISSION
THE SPATIAL EXTENT OF (U)LIRGs IN THE MID-INFRARED. I. THE CONTINUUM EMISSION
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DOI：
10.1088/0004-637x/723/2/993
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发表时间：
2010-08
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通讯作者：
T. Díaz-Santos;V. Charmandaris;L. Armus;A. Petric;J. Howell;E. Murphy;J. Mazzarella;S. Veilleux;G. Bothun;H. Inami;P. Appleton;A. Evans;S. Haan;J. Marshall;D. Sanders;S. Stierwalt;J. Crete;Forth Observatoire de Paris;Spitzer Science Center;Ipac;U. York;U. Oregon;Nasa Herschel Science Center;U. Virginia;University of Honolulu
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作者：
T. Díaz-Santos;V. Charmandaris;L. Armus;A. Petric;J. Howell;E. Murphy;J. Mazzarella;S. Veilleux;G. Bothun;H. Inami;P. Appleton;A. Evans;S. Haan;J. Marshall;D. Sanders;S. Stierwalt;J. Crete;Forth Observatoire de Paris;Spitzer Science Center;Ipac;U. York;U. Oregon;Nasa Herschel Science Center;U. Virginia;University of Honolulu
本文根据斯皮策红外光谱仪获得的5-15μm低分辨率光谱，分析了大观测站全天激光红外测绘样品的扩展中红外辐射。对于样本中的星系，我们计算扩展发射的比例(FEY)作为波长的函数，FEYλ定义为在给定距离处起源于源的未分辨分量之外的发射的比例。我们发现每个星系的Feeλ不同，但我们可以识别三种常见的Feeλ：一种是Feeλ恒定的，一种是发射线和多环芳烃的特征比连续体的特征更广泛，另一种是在9.7μm具有深度硅酸盐吸收的源的特征。超过30%的星系的Feeλ的中位数大于0.5，这意味着至少一半的MIR发射是扩展的。发光红外星系(LIRG)在其热尘埃连续体(0≲FEE 13.2μm≲0.85)中显示出很大范围的电荷。我们在许多LIRG中发现的FEE13.2kpm的大值表明，它们的MIR连续辐射的扩展分量起源于高达10kpc的尺度，并且可能与核区对它们的总MIR光度的贡献一样大。在13.2μm处，LIRG核心的平均尺寸为2.6kpc。然而，一旦系统的红外光度达到LIR∼1011.8 L☉的阈值，略低于超发光红外星系(ULIRG)的范围，所有的源显然变得更加致密，FEE13.2μm≲0.2，它们的核心是未分辨的。我们对未爆弹药核心大小的估计上限不到1.5千厘。此外，我们的分析表明，在相互作用的最后阶段被归类为合并的系统中，具有LIR≳1011.25 L☉的系统的紧致性显著增加。FEE13.2μm还与活动星系核对MIR发射的贡献有关。活动星系核占主导地位的星系的延展程度较小，与其LIR无关。最后，我们发现MIR连续发射的程度与远红外红外光谱测井(F60μm/F100μm)颜色相关。这使我们能够对银河系中可能产生冷尘埃的区域设定一个下限，这一预测很快就可以用赫歇尔太空望远镜进行验证。
We present an analysis of the extended mid-infrared (MIR) emission of the Great Observatories All-Sky LIRG Survey sample based on 5–15 μm low-resolution spectra obtained with the Infrared Spectrograph on Spitzer. We calculate the fraction of extended emission (FEE) as a function of wavelength for the galaxies in the sample, FEEλ, defined as the fraction of the emission which originates outside of the unresolved component of a source at a given distance. We find that the FEEλ varies from one galaxy to another, but we can identify three general types of FEEλ: one where FEEλ is constant, one where features due to emission lines and polycyclic aromatic hydrocarbons appear more extended than the continuum, and a third which is characteristic of sources with deep silicate absorption at 9.7 μm. More than 30% of the galaxies have a median FEEλ 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 ≲ FEE13.2 μm ≲ 0.85). The large values of FEE13.2 μm that we find in many LIRGs suggest that the extended component of their MIR continuum emission originates in scales up to 10 kpc and may contribute as much as the nuclear region to their total MIR luminosity. The mean size of the LIRG cores at 13.2 μm is 2.6 kpc. However, once the IR luminosity of the systems reaches the threshold of LIR ∼ 1011.8 L☉, slightly below the regime of Ultra-luminous Infrared Galaxies (ULIRGs), all sources become clearly more compact, with FEE13.2 μm ≲ 0.2, and their cores are unresolved. Our estimated upper limit for the core size of ULIRGs is less than 1.5 kpc. Furthermore, our analysis indicates that the compactness of systems with LIR ≳ 1011.25 L☉ strongly increases in those classified as mergers in their final stage of interaction. The FEE13.2 μm is also related to the contribution of an active galactic nucleus (AGN) to the MIR emission. 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(f60 μm/f100 μm) 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.