SPITZER QUASAR AND ULIRG EVOLUTION STUDY (QUEST). IV. COMPARISON OF 1 Jy ULTRALUMINOUS INFRARED GALAXIES WITH PALOMAR-GREEN QUASARS
SPITZER QUASAR AND ULIRG EVOLUTION STUDY (QUEST). IV. COMPARISON OF 1 Jy ULTRALUMINOUS INFRARED GALAXIES WITH PALOMAR-GREEN QUASARS
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DOI：
10.1088/0067-0049/182/2/628
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发表时间：
2009-05
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通讯作者：
S. Veilleux;D. Rupke;D. Rupke;D.-C. Kim;D.-C. Kim;R. Genzel;E. Sturm;D. Lutz;A. Contursi
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文献类型：
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作者：
S. Veilleux;D. Rupke;D. Rupke;D.-C. Kim;D.-C. Kim;R. Genzel;E. Sturm;D. Lutz;A. Contursi
本文报道了用Spitzer红外光谱仪（IRS）对z ≥ 0.3的74个超亮红外星系（ULIRGs）和34个Palomar-Green（PG）类星体的综合研究结果。在这些系统中，核活动对辐射热光度的贡献是使用六种独立的方法来量化的，这些方法跨越了一个波长范围，并给出了平均在±10%-15%范围内的一致结果。这种一致性表明，深埋的活动星系核（AGN）在斯皮策IRS中不可见，但在远红外线中很亮，在这个样本中并不常见。在ULIRGs中，AGN的平均贡献率为1.35%-40%，在光学分类为“冷”（f25/f60 = 0.2）的类H ii ULIRGs和LINER ULIRGs中，AGN的平均贡献率为1.15%-35%，在温暖的Seyfert 2 ULIRGs和Seyfert 1 ULIRGs中，AGN的平均贡献率分别为1.50%和1.75%。在PG类星体中，这个数字超过了80%。ULIRG可分为三类：（1）具有小折射率和大的多环芳烃（PAH）等效宽度的天体，其活动星系核贡献较大，但仍倾向于以星暴为主;（3）具有小半径和小PAH等效宽度的ULIRGs，其活动星系核的强度至少与星暴相当。活动星系核在第2类超红外星系中的贡献比其他天体更不确定，我们不能正式排除这些天体代表一种物理上不同类型的超红外星系的可能性。沿着序列（1）-（2）-（3）可以看到一种形态趋势，这与标准的ULIRG−类星体演化情景大体一致，并暗示在合并演化的中间阶段有一个广泛的灭绝高峰。然而，在这个序列中的分散，包括合并和星暴为主，但完全合并的系统之前，存在大量的活动星系核主导的系统，意味着黑洞吸积，除了取决于合并阶段，也有很强的混沌/随机成分，在本地活动星系核。
We report the results from a comprehensive study of 74 ultraluminous infrared galaxies (ULIRGs) and 34 Palomar-Green (PG) quasars within z ∼ 0.3 observed with the Spitzer Infrared Spectrograph (IRS). The contribution of nuclear activity to the bolometric luminosity in these systems is quantified using six independent methods that span a range in wavelength and give consistent results within ∼±10%–15% on average. This agreement suggests that deeply buried active galactic nuclei (AGNs) invisible to Spitzer IRS but bright in the far-infrared are not common in this sample. The average derived AGN contribution in ULIRGs is ∼35%–40%, ranging from ∼15%–35% among “cool” (f25/f60 ⩽ 0.2) optically classified H ii-like and LINER ULIRGs to ∼50 and ∼75% among warm Seyfert 2 and Seyfert 1 ULIRGs, respectively. This number exceeds ∼80% in PG QSOs. ULIRGs fall in one of three distinct AGN classes: (1) objects with small extinctions and large polycyclic aromatic hydrocarbon (PAH) equivalent widths are highly starburst-dominated; (2) systems with large extinctions and modest PAH equivalent widths have larger AGN contributions, but still tend to be starburst-dominated; and (3) ULIRGs with both small extinctions and small PAH equivalent widths host AGN that are at least as powerful as the starbursts. The AGN contributions in class 2 ULIRGs are more uncertain than in the other objects, and we cannot formally rule out the possibility that these objects represent a physically distinct type of ULIRGs. A morphological trend is seen along the sequence (1)–(2)–(3), in general agreement with the standard ULIRG−QSO evolution scenario and suggestive of a broad peak in extinction during the intermediate stages of merger evolution. However, the scatter in this sequence, including the presence of a significant number of AGN-dominated systems prior to coalescence and starburst-dominated but fully merged systems, implies that black hole accretion, in addition to depending on the merger phase, also has a strong chaotic/random component, as in local AGNs.