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arXiv 2504.08067astro-ph.HEastro-ph.GA
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超大质量黑洞光谱跃迁过程中的盘-喷流耦合

Disk-jet coupling across the spectral transition in supermassive black holes

Jia-Lai Kang, Chris Done, Scott Hagen, Mai Liao, Matthew J. Temple, John D. Silverman, Junyao Li, Jun-Xian Wang

AI总结:

本研究通过叠加VLASS图像分析eROSITA选无遮挡AGN样本的光谱跃迁射电行为,发现其射电-X射线流量比符合基平面关系,喷流与X射线热流耦合模式与双星一致,核心差异为AGN冕状X射线在跃迁中持续存在。

摘要:

恒星质量黑洞和超大质量黑洞的吸积流均表现出明显的光谱跃迁。这一现象可在双星系统和“变脸”活动星系核(AGN)中直接观测到,近期在eROSITA X射线选的无遮挡AGN样本中也有体现:针对单一黑洞质量区间(log $M/M_{\text{odot}} =8-8.5$)的叠加光谱能量分布(SED)清晰显示,随着光度升高,明亮的紫外吸积盘逐渐显现。在双星系统中,该跃迁与射电喷流的变化相关:喷流从与X射线热流耦合(满足$L_R \propto L_X^{0.7}$的基平面关系),转变为当X射线热流坍缩成吸积盘时喷流也随之坍缩。我们通过叠加VLASS(甚大阵天空调查)图像,探究了AGN样本在跃迁过程中的射电行为。即使扣除宿主星系中恒星形成的贡献后,我们仍显著探测到了微弱的射电辐射。尽管平均吸积率变化了6倍,紫外流量变化了100倍,但剩余射电辐射在整个跃迁过程中保持相对稳定。然而,X射线仅变化了2倍,使得射电与X射线的流量比保持恒定,这与“基平面”的预测一致。我们的研究表明,这些AGN的致密射电喷流与X射线热流(而非吸积盘)耦合的模式,与双星系统中的情况一致。最显著的差异在于,AGN的冕状X射线在光谱跃迁过程中持续存在,而在双星系统的吸积盘主导态中,冕状X射线可能非常微弱。

英文摘要:

Accretion flows in both stellar and supermassive black holes show a distinct spectral transition. This is seen directly in binaries and changing look AGN, and also in a recent sample of eROSITA X-ray selected, unobscured AGN where the stacked spectral energy distributions (SEDs) for a single black hole mass bin (log $M/M_{\odot} =8-8.5$) clearly show the UV bright disk appearing as the luminosity increases. In binaries, this transition is associated with a change in radio jet, from coupling to the X-ray hot flow with $L_R \propto L_X^{0.7}$ (Fundamental Plane relation), to collapsing when the X-ray hot flow collapses into a disc. We explore the radio behaviour across the transition in our AGN sample by stacking VLASS images. We significantly detect weak radio emission even after subtracting the contribution from star formation in the host galaxy. The residual radio emission remains relatively constant across the transition, despite the mean mass accretion rate changing by a factor 6 and UV flux changing by a factor 100. However, the X-rays change by only a factor 2, giving a constant radio to X-ray flux ratio as predicted by the 'fundamental plane'. We show that this is consistent with these AGN having the same compact radio jet coupling to the X-ray hot flow (not the disc) as in the binaries. The most significant difference is the persistence of the coronal X-rays across the spectral transition in AGN, whereas in binaries the coronal X-rays can be very weak in the disc dominated state.

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