On the 8th, the reporter learned from the University of Science and Technology of China that Associate Professors Cai Zhenyi and Wang Junxian of the Astronomy Department of the university, through studying the extreme ultraviolet radiation spectrum of the accretion of supermassive black holes at the center of quasars, found that it is not related to the intrinsic brightness of quasars, overturning traditional understanding in this field. Further research by researchers has found that the average extreme ultraviolet energy spectrum of quasars is much softer than expected by classical accretion disk theory, posing a serious challenge to classical accretion disk radiation models and strongly supporting accretion models with universal disk winds. The relevant results were recently published online in the form of a research article in Nature Astronomy. Quasars are a class of very bright extragalactic objects, with a supermassive black hole at their center continuously engulfing the gas in the core region of the galaxy. The enormous gravitational potential is released on the accretion disk formed by gas, converting it into thermal energy and electromagnetic radiation, making the galaxy core exceptionally bright. Quasars are also known as "super giants" in the universe due to their extremely high intrinsic brightness. The classical accretion disk theory indicates that accretion disks produce the famous "big blue envelope" radiation feature, with theoretical expected peaks in the extreme ultraviolet band. The larger the mass of the central black hole, the lower the theoretically expected temperature of the accretion disk, and the softer the extreme ultraviolet spectrum. Observations have found that brighter quasars have relatively weaker emission lines, and this Baldwin effect seems to be consistent with the classical accretion disk theory model. Researchers used observational data from ground based SDSS (Sloan Digital Sky Survey) and spatial GALEX (Galaxy Evolution Detector) to control the impact of incomplete extreme ultraviolet detection. They found that the average extreme ultraviolet energy spectrum of quasars does not depend on intrinsic brightness, which not only indicates that the difference in intrinsic brightness cannot explain the Baldwin effect, but also significantly challenges the predictions of classical accretion disk theory. The new study provides a possible new physical origin for the Baldwin effect: brighter quasars have smaller thermal fluctuations in their accretion disks, making it impossible to generate more emission line cloud clusters. By correcting the influence of interstellar medium absorption, the study also found that the extreme ultraviolet average energy spectrum of quasars is softer than all previous research results, posing further challenges to the classical accretion disk model. This ultra soft, independent of intrinsic brightness extreme ultraviolet energy spectrum well fits the predictions of the accretion disk model with disk winds, indicating the widespread presence of disk winds in quasars. (New News Agency)
Edit：Hou Wenzhe Responsible editor：WeiZe
Source：Science and Technology Daily
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