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arXiv 0805.0263astro-ph
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z~2 III红外发光星系的Spitzer中红外光谱:远红外-射电性质和光谱诊断

Spitzer Mid-Infrared Spectroscopy of Infrared Luminous Galaxies at z~2 III: Far-IR to Radio Properties and Optical Spectral Diagnostics

Anna Sajina, Lin Yan, Dieter Lutz, Aaron Steffen, George Helou, Minh Huynh, David Frayer, Philip Choi, Linda Tacconi, Kalliopi Dasyra

摘要:

本文给出了48个z~1-3 Spitzer选择的具有IRS中红外光谱的ULIRG样品的远红外、毫米波和射电测光以及光学和近红外光谱。我们的目标是计算它们的辐射热,并确定它们的活动星系核和星暴成分的存在和相对强度。我们发现,强PAH源往往有较高的160微米和1.2毫米通量比弱PAH源。9.7um硅酸盐特征的深度不影响MAMBO的可检测性。我们拟合了样品的远红外SED,发现< L_{IR} >z&gt;1.5的源的平均值约为7 × 10 ^{12}Lsun。光谱分解表明,强PAH源通常具有约20-30%的AGN分数。相比之下,弱多环芳烃源的活动星系核分数往往超过70%,少数源的活动星系核和星爆的贡献相当。光学线诊断支持活动星系核存在于大部分的弱PAH源。除了一个例外,我们的来源是窄线源,没有表现出明显的消光和硅酸盐特征深度之间的对应关系,并在两种情况下,显示流出的证据。射电活动星系核在强PAH源和弱PAH源中都存在。这是支持我们的样本的远红外无线电比(q)始终低于本地恒星形成星系的平均值2.34。我们使用生存分析来包括由无线电未检测到的源给出的下限,<q>对于我们的z&gt;1.5样本,达到=2.07+/-0.01。总的来说,无线电和光学线路诊断支持在57%的z&gt;1.5源中存在AGN,独立于基于IR的诊断。对于高z源,单独AGN的光度估计为&gt;10^{12}Lsun,这得到[OIII]光度的支持,这意味着我们的大部分源都有被遮蔽的类星体。

英文摘要:

We present the far-IR, millimeter, and radio photometry as well as optical and near-IR spectroscopy of a sample of 48 z~1-3 Spitzer-selected ULIRGs with IRS mid-IR spectra. Our goals are to compute their bolometric emission, and to determine both the presence and relative strength of their AGN and starburst components. We find that strong-PAH sources tend to have higher 160um and 1.2mm fluxes than weak-PAH sources. The depth of the 9.7um silicate feature does not affect MAMBO detectability. We fit the far-IR SEDs of our sample and find an average <L_{IR}>~7x10^{12}Lsun for our z>1.5 sources. Spectral decomposition suggests that strong-PAH sources typically have ~20-30% AGN fractions. Weak-PAH sources by contrast tend to have >~70% AGN fractions, with a few sources having comparable contributions of AGN and starbursts. The optical line diagnostics support the presence of AGN in the bulk of the weak-PAH sources. With one exception, our sources are narrow-line sources, show no obvious correspondence between the optical extinction and the silicate feature depth, and, in two cases, show evidence for outflows. Radio AGN are present in both strong-PAH and weak-PAH sources. This is supported by our sample's far-IR-to-radio ratios (q) being consistently below the average value of 2.34 for local star-forming galaxies. We use survival analysis to include the lower-limits given by the radio-undetected sources, arriving at <q>=2.07+/-0.01 for our z>1.5 sample. In total, radio and, where available, optical line diagnostics support the presence of AGN in 57% of the z>1.5 sources, independent of IR-based diagnostics. For higher-z sources, the AGN luminosities alone are estimated to be >10^{12}Lsun, which, supported by the [OIII] luminosities, implies that the bulk of our sources host obscured quasars.

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