[论文解读] Study of LINER sources with broad H(alpha) emission. Spectral energy distribution and multiwavelength correlations

George Younes, D. Porquet+3 more|arXiv (Cornell University)|Jan 26, 2012

Astrophysical Phenomena and Observations参考文献 140被引用 26

一句话总结

本研究利用同时获取的紫外和X射线数据，分析了六例具有宽H𝛼发射线的LINER 1s的谱谱能量分布（SEDs）及多波段相关性。结果发现，其SED在射电波段与有喷流的类星体相似，紫外波段的过量较弱（⟨αox⟩ ≈ −1.17 ± 0.02），X射线谱与无喷流类星体相似，且总辐射光度比活动星系核（AGN）低两个数量级。结果表明其吸积机制复杂，X射线发射中存在RIAF与喷流主导的相互矛盾证据。

ABSTRACT

(Abridged) We attempt to infer the accretion mechanism and radiative processes giving rise to the SEDs of a well-defined optically-selected sample of LINERs showing a definite detection of broad Halpha emission (LINER 1s). We construct SEDs for six LINER~1s with simultaneous UV and X-ray fluxes, and we looked for multiwavelength, radio to X-ray and UV to X-ray, correlations. At a given X-ray luminosity, the average SED of the six LINER 1s in our sample: (1) resembles the SED of radio-loud quasars in the radio band, ~-2.7, (2) exhibits a weak UV bump, ~-1.17+-0.02 with a dispersion sigma=0.01, and (3) displays a X-ray spectrum similar to radio-quiet quasars. The bolometric luminosities inferred from the SEDs are extremely faint, at least two orders of magnitude lower than AGN. The X-ray bolometric correction, kappa_(2-10 keV), of our sample is lower than in the case of AGN, with a mean value of 16. We find a strong anticorrelation between the radio loudness parameter, R_X, and the Eddington ratio for our sample, confirming previous results. Moreover, we find a positive correlation between the radio luminosity and the X-ray luminosity which places AGN-powered LINERs, on a radio-power scale, right between low luminosity Seyferts and low luminosity radio galaxies. We complement our alpha_ox list with values derived on a well defined sample of UV-variable LINERs, and establish a strong positive correlation between alpha_ox (considering negative values) and the Eddington ratio, in contrast to the correlation found for luminous AGN. Lastly, we tested two different fundamental planes existing in the literature on our sample, in an attempt to put constraints on the debated origin of the X-ray emission, "RIAF versus jet". The results came contradictory with one pointing toward a RIAF-dominated X-ray emission process and the other pointing toward a jet domination.

研究动机与目标

• 利用多波段SED研究具有宽H𝛼发射线的LINER 1s中的吸积机制与辐射过程。
• 解决LINER 1s中X射线发射是否源于辐射效率低的吸积流（RIAF）或喷流主导过程的争议。
• 研究低光度AGN中射电噪度、X射线光度与爱丁顿比之间的关系。
• 检验LINER 1s与已确立的黑洞活动基本平面的一致性。
• 确定LINER 1s中紫外至X射线谱型（αox）是否与爱丁顿比相关，与明亮AGN进行对比。

提出的方法

• 利用XMM-Newton OM的紫外（UV）和XMM-Newton EPIC的X射线通量，构建六例LINER 1s的SED。
• 获取5 GHz波段的高分辨率射电数据（VLA或VLBI），计算射电噪度参数RX = νLν(5 GHz)/L2–10 keV。
• 计算紫外至X射线谱指数αox = 0.383 log(fX / fν)，以量化紫外发射相对于X射线的过量程度。
• 分析αox、RX、X射线光度与爱丁顿比之间的相关性，以推断吸积物理机制。
• 应用两个黑洞活动基本平面——Yuan等（2009）与Plotkin等（2011）——以检验LINER 1s中X射线发射是RIAF主导还是喷流主导。
• 结合现有紫外变光源LINER样本的αox值，强化统计趋势。

实验结果

研究问题

• RQ1 在射电、紫外和X射线波段，LINER 1s的SED与有喷流和无喷流类星体的SED相比如何？
• RQ2 LINER 1s中αox与爱丁顿比的关系如何？与明亮AGN相比有何不同？
• RQ3 LINER 1s中射电噪度（RX）与爱丁顿比之间是否存在相关性？这对吸积模式有何启示？
• RQ4 黑洞活动的基本平面是否支持LINER 1s中X射线发射为RIAF主导或喷流主导？
• RQ5 在射电光度与X射线光度平面中，LINER 1s相对于低光度赛弗特星系和低光度射电星系位于何处？

主要发现

• 在相同X射线光度下，六例LINER 1s的平均SED与有喷流类星体相似，⟨log RX⟩ ≈ −2.7。
• 紫外至X射线谱指数的平均值为αox ≈ −1.17 ± 0.02，表明紫外过量较弱，且分散度小（σ = 0.01）。
• LINER 1s的X射线谱型与无喷流类星体一致，暗示其X射线发射机制相似。
• 由SED推算出的总辐射光度极低，至少比典型AGN低两个数量级。
• 发现RX与爱丁顿比之间存在强烈的负相关性，证实了此前对低光度AGN（LLAGN）的研究结果，并将其扩展至LINER 1s。
• 射电与X射线光度之间存在正相关性，表明LINER 1s位于低光度赛弗特星系与低光度射电星系之间的射电功率尺度上。