Fading AGN Candidates: AGN Histories and Outflow Signatures
Fading AGN Candidates: AGN Histories and Outflow Signatures
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DOI：
10.3847/1538-4357/835/2/256
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发表时间：
2016-12
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通讯作者：
W. Keel;C. Lintott;W. Maksym;V. Bennert;S. Chojnowski;A. Moiseev;A. Smirnova;K. Schawinski;L. Sartori;C. Urry;A. Pancoast;M. Schirmer;B. Scott;Charles Showley;K. Flatland
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作者：
W. Keel;C. Lintott;W. Maksym;V. Bennert;S. Chojnowski;A. Moiseev;A. Smirnova;K. Schawinski;L. Sartori;C. Urry;A. Pancoast;M. Schirmer;B. Scott;Charles Showley;K. Flatland
我们考虑的能量预算和辐射历史的八个衰落的活动星系核（AGN），确定从能量短缺的要求，非常广泛的（半径> 10千秒差距）电离云和光度的核，因为我们直接查看它。所有这些都显示出在150，000年的时间尺度上显着衰落的证据。我们探讨了使用最小电离亮度Qion从光电离平衡Hα在每个投影半径的最亮像素。测试使用假定恒定的Palomar-Green类星体，我们的目标之一，详细的光电离建模，表明我们可以得到有用的历史的个人活动星系核，与警告的最小电离光度总是被低估，并受到电离物质的精细结构的不确定性。这些一致性测试表明，从重建Qion值的上包络的低估程度对于给定的对象是大致恒定的，因此不会阻止这样的推导。在我们的样本中，活动星系核表现出一系列的行为，有快速下降和静止;共同的特征是在直接观察到原子核之前的最后102 × 104年中快速下降。电离光度的e-折叠时间尺度大多在数千年内，少数短至400年。在很大程度上模糊AGN的限制，我们发现更多的证据，甚至从重组平衡的下限和来自远红外通量的最大光度之间的差距褪色。我们比较这些长期的光变曲线，并在所有光学识别的活动星系核中发生这些衰落的物体，活动星系核吸积的模拟，在这些时间跨度的最强变化被认为是在模型中具有强大的和本地（秒差距尺度）的反馈。我们提出了双子积分场光学光谱，这表明在这些电离结构的外流非常有限的作用。虽然环和环的发射，形态暗示外流，是常见的，他们的运动学结构显示，一些是在定期旋转。UGC 7342显示出小于300 km s−1的外流特征，主要与非常弥散的发射有关，可能在哈勃太空望远镜图像中看到的其中一个云中夹带气体。只有在茶杯活动星系核中，我们才能看到1000 km s-1量级的外流特征。与许多射电强活动星系核周围的扩展发射区相反，这些衰落活动星系核周围的云主要由潮汐碎片组成，这些碎片被外部照射，但不被活动星系核外流所取代。
We consider the energy budgets and radiative history of eight fading active galactic nuclei (AGNs), identified from an energy shortfall between the requirements to ionize very extended (radius > 10 kpc) ionized clouds and the luminosity of the nucleus as we view it directly. All show evidence of significant fading on timescales of ≈50,000 yr. We explore the use of minimum ionizing luminosity Qion derived from photoionization balance in the brightest pixels in Hα at each projected radius. Tests using presumably constant Palomar–Green QSOs, and one of our targets with detailed photoionization modeling, suggest that we can derive useful histories of individual AGNs, with the caveat that the minimum ionizing luminosity is always an underestimate and subject to uncertainties about fine structure in the ionized material. These consistency tests suggest that the degree of underestimation from the upper envelope of reconstructed Qion values is roughly constant for a given object and therefore does not prevent such derivation. The AGNs in our sample show a range of behaviors, with rapid drops and standstills; the common feature is a rapid drop in the last ≈2 × 104 yr before the direct view of the nucleus. The e-folding timescales for ionizing luminosity are mostly in the thousands of years, with a few episodes as short as 400 yr. In the limit of largely obscured AGNs, we find additional evidence for fading from the shortfall between even the lower limits from recombination balance and the maximum luminosities derived from far-infrared fluxes. We compare these long-term light curves, and the occurrence of these fading objects among all optically identified AGNs, to simulations of AGN accretion; the strongest variations over these timespans are seen in models with strong and local (parsec-scale) feedback. We present Gemini integral-field optical spectroscopy, which shows a very limited role for outflows in these ionized structures. While rings and loops of emission, morphologically suggestive of outflow, are common, their kinematic structure shows some to be in regular rotation. UGC 7342 exhibits local signatures of outflows <300 km s−1, largely associated with very diffuse emission, and possibly entraining gas in one of the clouds seen in Hubble Space Telescope images. Only in the Teacup AGN do we see outflow signatures of the order of 1000 km s−1. In contrast to the extended emission regions around many radio-loud AGNs, the clouds around these fading AGNs consist largely of tidal debris being externally illuminated but not displaced by AGN outflows.