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arXiv 1209.0293astro-ph.HE
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孤立吸积黑洞的喷流和gamma-ray辐射

Jets and gamma-ray emission from isolated accreting black holes

M. V. Barkov, D. V. Khangulyan, S. B. Popov

摘要:

银河系中大量孤立的黑洞(IBH)的数量估计为10 ^8,这意味着密度非常高,达到10^-4 pc^-3,IBH之间的平均距离为10 pc。我们的研究表明,磁通量,积累在IBH的地平线上,因为星际物质的吸积,允许布兰德福德-Znajeck机制被激活。因此,电子-正电子喷流可以被发射。我们进行了二维数值模拟,使喷气功率进行估计。它们的推断属性使这样的射流成为可行的电子加速器,在分子云中,允许电子能量提高到1 PeV。对于分子云中预期的条件,辐射冷却时间应该与逃逸时间相当。因此,这些来源可以有助于人口的身份不明的点状源和当地的宇宙射线(CR)的电子光谱。产生的电子CRs的影响取决于分子云(MC)内的扩散速率。如果MC中的扩散机制类似于银河系的扩散,那么产生的电子应该会迅速逃离云,并在>100 TeV的非常高的能量下贡献给银河系CR人口。然而,由于中等的喷流光度(在10^35 erg s^-1的水平)和MC的低填充因子,这些源不能对较低能量的宇宙线电子谱做出显著贡献。另一方面,如果MC内的扩散以接近玻姆极限的速率操作,则从源逸出的CR电子应该被限制在云中,从而显著地有助于CR的局部密度。这些本地产生的CR的IC发射可以解释从附近的MC检测到的伽马射线谱的变化。

英文摘要:

The large number of isolated black holes (IBHs) in the Galaxy, estimated to be 10^8, implies a very high density of 10^-4 pc^-3 and an average distance between IBHs of 10 pc. Our study shows that the magnetic flux, accumulated on the horizon of an IBH because of accretion of interstellar matter, allows the Blandford-Znajeck mechanism to be activated. Thus, electron-positron jets can be launched. We have performed 2D numerical modelling which allowed the jet power to be estimated. Their inferred properties make such jets a feasible electron accelerator which, in molecular clouds, allows electron energy to be boosted up to 1 PeV. For the conditions expected in molecular clouds the radiative cooling time should be comparable to the escape time. Thus these sources can contribute both to the population of unidentified point-like sources and to the local cosmic ray (CR) electron spectrum. The impact of the generated electron CRs depends on the diffusion rate inside molecular clouds (MCs). If the diffusion regime in a MC is similar to Galactic diffusion, the produced electrons should rapidly escape the cloud and contribute to the Galactic CR population at very high energies >100 TeV. However, due to the modest jet luminosity (at the level of 10^35 erg s^-1) and low filling factor of MC, these sources cannot make a significant contribution to the spectrum of cosmic ray electrons at lower energies. On the other hand, if the diffusion within MCs operates at a rate close to the Bohm limit, the CR electrons escaping from the source should be confined in the cloud, significantly contributing to the local density of CRs. The IC emission of these locally-generated CRs may explain the variety of gamma ray spectra detected from nearby MCs.

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