Researchers revolutionize understanding of supermassive black hole accretion radiation in quasars

By means of the research of the optical to excessive ultraviolet radiation generated by the accretion of supermassive black holes on the facilities of quasars, Affiliate Professor Cai Zhenyi and Professor Wang Junxian from the Division of Astronomy on the College of Science and Know-how of China (USTC) of the Chinese language Academy of Sciences (CAS) have found that their spectral vitality distribution is unbiased to the intrinsic brightness of quasars, overturning the normal understanding on this area.

Their research unveils a considerable departure of the common excessive ultraviolet spectral energy distribution of quasars from the predictions of the classical accretion disk principle. This discovery challenges the classical mannequin and supplies substantial assist for fashions that incorporate widespread accretion disk winds. The outcomes have been published on-line on October 5, 2023 in Nature Astronomy.

Quasars are a category of extraordinarily vivid extragalactic objects the place huge supermassive black holes at their facilities constantly devour the gasoline within the core areas of their host galaxies. The immense gravitational potential vitality is launched on the accretion disk fashioned by the gasoline, changing into thermal energy and electromagnetic radiation, leading to an abnormally vivid nucleus of the galaxy.

Quasars are additionally known as “cosmic behemoths” attributable to their exceptionally excessive intrinsic luminosity. In response to the usual accretion disk principle, accretion disks produce the well-known “large blue bump” within the spectral vitality distribution, with the height anticipated within the excessive ultraviolet. The bigger the central black hole’s mass, the decrease the anticipated temperature of the accretion disk, and the softer the intense ultraviolet spectrum.

Observations have revealed that extra luminous quasars (with bigger supermassive black hole lots) exhibit comparatively weaker emission traces (defined by softer excessive ultraviolet spectra), often known as the well-known Baldwin Impact, which seems to be in keeping with the classical accretion disk mannequin.

Affiliate Professor Cai Zhenyi and Professor Wang Junxian’s analysis focuses instantly on the optical-to-ultraviolet spectral vitality distribution of enormous pattern quasars. The research makes use of observational data from the ground-based SDSS and space-based GALEX, controlling for the incompleteness of the ultraviolet detection.

They discovered that the common ultraviolet spectral vitality distribution of quasars don’t rely upon their intrinsic brightness, which not solely means that variations in intrinsic brightness can not clarify the Baldwin impact but additionally challenges the predictions of ordinary accretion disk principle. On the identical time, the researchers suggest a potential new bodily origin for the Baldwin impact: extra luminous quasars have weaker accretion disk temperature fluctuations, thus unable to launch extra emission line clouds.

As well as, the research corrects for the results of intergalactic medium absorption and finds that the common excessive ultraviolet spectrum of quasars is softer than all earlier analysis outcomes. This discrepancy poses a big problem to the usual accretion disk mannequin however aligns effectively with predictions from the mannequin involving an accretion disk wind, suggesting the prevalence of disk winds in quasars.

The outcomes of this research have broad implications for a deeper understanding of assorted features of supermassive black hole accretion physics, black hole mass development, cosmic reionization, the origin of broad-line areas, excessive ultraviolet dust extinction, and extra.

Sooner or later, satellite initiatives with ultraviolet detection capabilities, such because the Chinese language House Station Telescope (CSST, http://nao.cas.cn/csst/), will vastly improve our understanding of the bodily properties of quasars and related celestial objects.