We explore the possibility to detect the continuum radio signal from direct collapse black holes (DCBHs) by upcoming radio telescopes such as the SKA and ngVLA, assuming that after formation they can launch and sustain powerful jets at the accretion stage. We assume that the high-z DCBHs have similar jet properties as the observed radio-loud AGNs, then use a jet model to predict their radio flux detectability. If the jet power Pjet ≳ 1042–1043 erg s−1, it can be detectable by SKA/ngVLA, depending on the jet inclination angle. Considering the relation between jet power and black hole mass and spin, generally, jetted DCBHs with mass $\gtrsim 10^5\, {\rm M}_\odot$ can be detected. For a total jetted DCBH number density of ∼2.5 × 10−3 Mpc−3 at z = 10, about 100 deg−2z−1 DCBHs are expected to be above the detection threshold of SKA1-mid (100-h integration). If the jet ‘blob’ emitting most of the radio signal is dense and highly relativistic, then the DCBH would only feebly emit in the SKA-low band, because of self-synchrotron absorption (SSA) and blueshift. Moreover, the free–free absorption in the DCBH envelope may further reduce the signal in the SKA-low band. Thus, combining SKA-low and SKA-mid observations might provide a potential tool to distinguish a DCBH from a normal star-forming galaxy.

中文翻译：

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来自早期直接坍缩黑洞的无线电信号

我们探索了通过即将到来的射电望远镜（如 SKA 和 ngVLA）探测直接坍缩黑洞 (DCBH) 的连续射电信号的可能性，假设它们在形成后可以在吸积阶段发射和维持强大的喷流。我们假设高 z DCBH 具有与观察到的无线电响亮 AGN 相似的射流特性，然后使用射流模型来预测它们的射电通量可探测性。如果射流功率 Pjet ≳ 1042–1043 erg s−1，则可以通过 SKA/ngVLA 检测到，具体取决于射流倾角。考虑到喷射功率与黑洞质量和自旋的关系，一般可以检测到质量为$\gtrsim 10^5\的喷射DCBH，{\rm M}_\odot$。在 z = 10 时，总喷射 DCBH 数密度约为 2.5 × 10-3 Mpc-3，预计约 100 deg-2z-1 DCBH 将高于 SKA1-mid 的检测阈值（100-h 积分）。如果发射大部分无线电信号的射流“斑点”是密集且高度相对论的，那么由于自同步加速器吸收 (SSA) 和蓝移，DCBH 只会在 SKA 低波段微弱地发射。此外，DCBH 包络中的自由吸收可能会进一步降低 SKA 低频带中的信号。因此，结合 SKA-low 和 SKA-mid 观测可能会提供一种潜在的工具来区分 DCBH 和正常的恒星形成星系。DCBH 包络中的自由吸收可能会进一步降低 SKA 低频带中的信号。因此，结合 SKA-low 和 SKA-mid 观测可能会提供一种潜在的工具来区分 DCBH 和正常的恒星形成星系。DCBH 包络中的自由吸收可能会进一步降低 SKA 低频带中的信号。因此，结合 SKA-low 和 SKA-mid 观测可能会提供一种潜在的工具来区分 DCBH 和正常的恒星形成星系。