中文摘要：

类星体与赛弗特Ⅰ型星系中观测到很陡的巴尔末减缩，与传统的理论预言相矛盾．这是一个长期没有解决的困惑．如果活动星系核的宽的氢线是产生于“Cerenkov线状辐射”机制，这一难题就可解决．搜集了过去已发表的近百个有巴尔末减缩观测结果的类星体与赛弗特星系源，并采用“Cerenkov线状辐射”这一新型辐射机制的线强比公式完成了对观测的巴尔末减缩的理论计算．理论与观测符合很好，这是活动星系核宽的氢发射线主要起源于“Cerenkov线状辐射”机制的一个重要证据．如果这一结论最终获得肯定，将大大改变人们对活动星系核物理的认识．

英文摘要：

Observations of QSOs and Seyfert Is show an anomalously steep Balmer Decrement, which is in contradiction to the prediction of the traditional recombination theory. This is a long standing puzzle in past three decades in the studies of AGNs. In this paper, we provide an alternative way to solve this puzzle by using a newly recognized line emission mechanism, i.e., the ‘Cerenkov line-like radiation＇. For this purpose, we collect a number of AGNs samples, including the QSOs and Seyfert Is, for which the intensities of hydrogen Balmer lines were measured and given out in past thirty years. We complete the calculations of the Balmer decrement by use of the improved formula describing the Cerenkov line intensity, to fit the observations. The coincidence between theory and observations is excellent. We therefore argue that the broad hydrogen lines of QSOs and Seyfert Is predominantly arise from the Cerenkov line-like radiation of the relativistic electrons. If this suggestion is further confirmed in future, the scenario of the environment around the central supermassive black hole will be markedly changed.