Overthrow traditional understanding! Latest Discovery by Chinese Scientists

Source: [Love Jinan News Client]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

Source: [Love Jinan News Client]

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.

Schematic diagram of a black hole accretion disk. Image source: University of Science and Technology of China

Revealing new laws of the energy spectrum of the accretion radiation of supermassive black holes

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 standard accretion disk theory indicates that accretion disks produce the famous "big blue envelope" radiation feature, and the theoretical expected peak is 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, known as the Baldwin effect, which 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 Probe) 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 standard accretion disk theory. At the same time, the author provides a possible new physical origin of the Baldwin effect: the brighter the quasar, the smaller the thermal fluctuations in its accretion disk, and thus unable to generate more emission line area clouds. 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 serious challenges to the standard 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.

The results of this study have broad implications for a deeper understanding of the accretion physics of massive black holes, black hole mass growth, cosmic re ionization, the origin of wide line physics, and extreme ultraviolet dust extinction. (Source: WeChat official account of Science and Technology Daily)

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