Astronomers take deep look into material around black holes

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Washington, December 9 (ANI): An international research team has taken a deep look into the shape and geometry of the accreting material around the black hole in nearby Active Galactic Nuclei (AGN).

The team, led by Makoto Kishimoto from the Max Planck Institute for Radio Astronomy in Bonn, combined infrared imaging from the United Kingdom Infrared Telescope (UKIRT) and some of the first ever infrared long-baseline interferometric measurements from the Keck Observatory to observe the nearby AGN.

The measurements show a ring-like emission from sublimating dust grains, and its radius yields insights into the shape and geometry of the accreting material around the black hole in these galactic centers.

In May 2009, Makoto Kishimoto and his team successfully observed four such AGN with the Keck Interferometer, and they followed the observations up with infrared imaging from the UK Infrared Telescope (UKIRT). oth observatories are on Mauna Kea in Hawaii.

The target sources included NGC 4151, a relatively nearby galaxy only 50 million light-years away, and a distant quasar at redshift 0.108 (corresponding to a distance of more than a billion light-years).

"The Keck measurements give us a uniquely high-resolution look at the innermost regions of the active nucleus, and the UKIRT images are very powerful in disentangling the contributions of the host galaxy and the accretion disk in the interferometry data," said Makoto Kishimoto, the research paper's leading author.

Until recently, only one AGN had been successfully observed with the called Keck interferometer (KI).

This galaxy, NGC 4151, is one of the brightest of these sources in the optical and infrared wavelengths.

The new, more sensitive observations of four galaxies have led to a much clearer picture of what is being resolved - a ring-like emission of dust grains, co-existing in the accreting gas, which are hot enough to be sublimating.

Using different, independent measurements of the radius of this dust sublimation region (which come from the analysis of the variabilities of the optical and infrared light), the team thinks that they have also possibly started to probe how the accreting material is distributed radially from the black hole - that is, how compact or how extended the material distribution is.

"While we have got the highest spatial resolution in the IR, this is still a relatively outer region of the central black hole system", said Makoto Kishimoto.

"We hope to achieve an even higher resolution using telescopes that are much further apart in order to get even closer to the center, and we also hope to observe many other supermassive black hole systems," he added. (ANI)

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