M. Brienza, R. Morganti, M. Murgia, N. Vilchez, B. Adebahr, E. Carretti, R. Concu, F. Govoni, J. Harwood, H. Intema, F. Loi, A. Melis, R. Paladino, S. Poppi, A.… 展开作者
M. Brienza, R. Morganti, M. Murgia, N. Vilchez, B. Adebahr, E. Carretti, R. Concu, F. Govoni, J. Harwood, H. Intema, F. Loi, A. Melis, R. Paladino, S. Poppi, A. Shulevski, V. Vacca, G. Valente
Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. In this work we investigate the duty cycle of the radio galaxy B2~0258+35, which was previously suggested to be a restarted radio galaxy based on its morphology. The radio source consists of a pair of kpc-scale jets embedded in two large-scale lobes (~240 kpc) with relaxed shape and very low surface brightness, which resemble remnants of a past AGN activity. We have combined new LOFAR data at 145 MHz and new SRT data at 6600 MHz with available WSRT data at 1400 MHz to investigate the spectral properties of the outer lobes and derive their age. Interestingly, the spectrum of both the outer Northern and Southern lobes is not ultra-steep as expected for an old ageing plasma with spectral index values equal to $\rm α_{1400}^{145}=0.48\pm0.11$ and $\rm α_{6600}^{1400}=0.69\pm0.20$ in the outer Northern lobe, and $\rm α_{1400}^{145}=0.73\pm0.07$ in the outer Southern lobe. Moreover, despite the wide frequency coverage available for the outer Northern lobe (145-6600~MHz), we do not identify a significant spectral curvature (SPC$\simeq$0.2$\pm0.2$). While mechanisms such as in-situ particle reacceleration, mixing or compression can temporarily play a role in preventing the spectrum from steepening, in no case seem the outer lobes to be compatible with being very old remnants of past activity as previously suggested (with age $\gtrsim$ 80 Myr). We conclude that either the large-scale lobes are still fuelled by the nuclear engine or the jets have switched off no more than a few tens of Myr ago. Our study shows the importance of combining morphological and spectral properties to reliably classify the evolutionary stage of low surface brightness, diffuse emission that low frequency observations are revealing around a growing number of radio sources.
University of Hertfordshire（赫特福德大学）；Amity University Uttar Pradesh（北方阿美蒂大学）；The Inter-University Institute for Data Intensive Astronomy (IDIA)（数据密集型天文学跨大学研究所）；University of Cape Town（开普敦大学）；National Centre for Radio Astrophysics - Tata Institute of Fundamental Research（国家射电天文中心 - 塔塔基础研究所）；UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai（孟买大学基础科学卓越中心）；NCU（尼古拉·哥白尼大学）；Catholic University of Lyon（里昂天主教大学）；University of Oslo（奥斯陆大学）；University of Tasmania（塔斯马尼亚大学）
Constraining the AGN duty cycle in the cool-core cluster MS 0735.6+7421 with LOFAR data
MS 0735.6+7421是一个星系团，它拥有一个光谱非常陡峭的中央射电星系，由已知最强大的喷射活动星系核（AGN）之一产生。射电等离子体以接近光速的速度从活动星系核中心喷出，取代了星系团内的介质，留下了两对在X射线中可观察到的空洞，与两个不同的爆发有关，并将能量分配给周围的介质。在这项工作中，我们第一次进行了详细的，高分辨率的频谱研究的来源在射频和调查其占空比与以前的X射线估计进行比较。我们已经使用了新的观测在144兆赫产生的低频阵列（LOFAR）与档案数据在更高的频率。在LOFAR频率下，源呈现出两个大的外射电瓣，比在更高的频率下更宽，以及一个位于核心西南部的较小的中间瓣。对X射线数据的新检查使我们能够确定与该叶相关的中间空腔，表明存在进一步的喷流活动阶段。即使在LOFAR频率下，射电瓣也具有陡峭的频谱，在外瓣中达到$α_{144}^{610}=2.9$，在中间瓣中达到$α_{144}^{610}=2.1$。拟合波瓣光谱使用一个单一的注入模型的粒子老化，我们得出了总年龄的源之间的170和106百万年，与来自X射线数据的浮力和声交叉的时间尺度。然后我们重建了源的占空比。喷流活动有三个阶段，活动星系核在大部分时间都是活跃的，只有短暂的静止阶段，确保了中心气体的重复加热。最后，能量估计显示，必须存在额外的压力支持源，以维持气泡对抗外部介质的压力。
Evolution in the Black Hole - Galaxy Scaling Relations and the Duty Cycle of Nuclear Activity in Star-Forming Galaxies
本文测量了69个Herschel探测到的宽线活动星系核（BLAGN）在M_BH-M_* 平面上的位置和演化矢量。BLAGN选自COSMOS和CDF-S场，并且跨越红移范围0.2< z<2.1。黑洞质量的计算使用档案光谱学和单历元维里质量估计，和星系总恒星质量的计算通过拟合光谱能量分布（减去BLAGN分量）。分别使用Chandra/XMM-牛顿X射线和Herschel远红外数据计算了黑洞和星系的质量增长率，这些数据是BLAGN吸积和星系恒星形成率的可靠测量。我们使用蒙特卡罗模拟来解释我们的样本中的偏差，由于选择限制和星系恒星质量分布的大质量末端的陡峭斜率。我们发现我们的样本与M_BH-M_* 关系从z~2到z~0没有演化是一致的。BLAGN和它们的宿主星系如果偏离了黑洞质量星系总恒星质量的关系，则它们的演化矢量往往与它们的质量比反相关：也就是说，具有超大质量（欠大质量）黑洞的星系往往具有低（高）的比吸积率与比恒星形成率之比。我们还使用测量的增长率来估计我们的星系的首选AGN占空比，以最一致地演变到本地M_BH-M_Bul关系。在恒星形成历史呈指数下降的合理假设下，数据表明恒星形成星系中的BLAGN占空比为10%（z 1时1 σ范围为1-42%<1 and 2-34% at z>）。
Probing AGN duty cycle and cluster-driven morphology in a giant episodic radio galaxy
Midnapore City College（金达布尔城市学院）；Manipal Centre for Natural Sciences, Manipal Academy of Higher Education（马纳帕尔高等教育局马纳帕尔自然科学中心）；Obserwatorium Astronomiczne, Uniwersytet Jagielloński（雅盖隆大学天文台）
Clustering of z~6.6 Quasars and [O III] Emitters Constrains Host Halo Masses and Duty Cycles in 25 ASPIRE Fields
University of California, Santa Barbara（加州大学圣塔芭芭拉分校）；Leiden University（莱顿大学）；Harvard University（哈佛大学）；University of Michigan（密歇根大学）；University of Arizona（亚利桑那大学）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；University of Copenhagen（哥本哈根大学）
MIGHTEE: The dark matter haloes, duty cycle and mechanical feedback from radio-AGN up to $z \sim 2.5$
University of Oxford（牛津大学）；School of Physics and Astronomy, Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理与天文学院天体物理研究所）；Department of Physics and Astronomy, University of the Western Cape（西开普大学物理与天文系）
