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arXiv 1003.0858astro-ph.CO
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核活动作为超亮红外星系动力源的作用

The role of nuclear activity as the power source of ultraluminous infrared galaxies

E. Nardini, G. Risaliti, Y. Watabe, M. Salvati, E. Sani

摘要:

我们提出了一个5-8微米的光谱分析的结果进行了最大的本地超亮红外星系(ULIRGs)的样本选择到目前为止,由164个对象的红移~0.35。斯皮策星载红外摄谱仪的空前灵敏度使我们能够开发出一种有效的诊断方法,以解开活动星系核(AGN)和星暴(SB)对这类天体的贡献。为了得到AGN/SB对每个源总光度的相对贡献,对这两个分量的内禀辐射热改正进行了估计。我们的主要结果如下:1)AGN在本地ULIRGs中的检测率高达70%,在我们的样本中有113/164的令人信服的检测,而全球AGN/SB功率平衡约为1/3。2)一个普遍的协议被发现与光学分类,然而,在没有光谱特征的核活动的对象,我们的红外诊断发现一个难以捉摸的,高度模糊AGN的子类。3)我们分析了核活动与红外光度之间的相关性,恢复了AGN重要性随系统总能量输出而增加的众所周知的趋势:在ULIRG光度范围内,AGN的平均贡献从~ 10%上升到~ 60%。4)我们证实,活动星系核的内容是在紧凑的系统,但活动和演化阶段之间的联系是相当松散的。5)通过分析z ~ 1附近的红外发光星系的控制样本,我们发现AGN和SB成分的大尺度光谱特性的红移只有微小的变化。这强调了我们的方法作为一个简单的和定量的AGN/SB诊断工具的ULIRG类系统在高红移的潜力。

英文摘要:

We present the results of a 5-8 micron spectral analysis performed on the largest sample of local ultraluminous infrared galaxies (ULIRGs) selected so far, consisting of 164 objects up to a redshift of ~0.35. The unprecedented sensitivity of the Infrared Spectrograph onboard Spitzer allowed us to develop an effective diagnostic method to disentangle the active galactic nucleus (AGN) and starburst (SB) contribution to this class of objects. The intrinsic bolometric corrections are estimated for both the components, in order to obtain the relative AGN/SB contribution to the total luminosity of each source. Our main results are the following: 1) The AGN detection rate among local ULIRGs amounts up to 70 per cent, with 113/164 convincing detections within our sample, while the global AGN/SB power balance is ~1/3. 2) A general agreement is found with optical classification; however, among the objects with no spectral signatures of nuclear activity, our IR diagnostics find a subclass of elusive, highly obscured AGN. 3) We analyse the correlation between nuclear activity and IR luminosity, recovering the well-known trend of growing AGN significance as a function of the overall energy output of the system: the average AGN contribution rises from ~10 to ~60 per cent across the ULIRG luminosity range. 4) We confirm that the AGN content is larger in compact systems, but the link between activity and evolutionary stage is rather loose. 5) By analysing a control sample of IR-luminous galaxies around z ~ 1, we find evidence for only minor changes with redshift of the large-scale spectral properties of the AGN and SB components. This underlines the potential of our method as a straightforward and quantitative AGN/SB diagnostic tool for ULIRG-like systems at high redshift as well.

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