2021-06-10

Astronomers discover the “dying echo” of supermassive black holes

By yqqlm yqqlm

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Astronomers discover the “dying echo” of supermassive black holes

It is believed that supermassive black holes lurk in the centers of most galaxies. Some of these black holes are more active than others–for example, the black hole at the center of our Milky Way is quite calm. But other black holes “work overtime” and release a lot of light and radiation in the process of swallowing matter. These are called active galactic nuclei (AGN), and if they are particularly bright, they are called quasars.

The Arp 187 galaxy looks quite quiet now, but obviously this is not always the case. In fact, according to researchers at Northeastern University, it seems to be an AGN recently.

Astronomers discover the “dying echo” of supermassive black holes(1)

The research team uses two radio telescopes –Atacama Large Millimeter/Submillimeter Array (ALMA) and Very Large Antenna Array (VLA) – Observed Arp 187 and discovered a strange sight that did not belong to it – two huge jet lobes. They are similar to those emitted by AGN, but unlike garden-style AGN, the black hole in the center is silent.

Next, the research team carefully observed the data that captured radiation at multiple wavelengths, including radio, mid-infrared, and X-rays. This confirms that all the usual small-scale signs of AGN activity have ceased, but the large-scale signs, the jet lobes, are still visible. This shows that these activities have stopped sometime in the past few thousand years-from the point of view of the universe, they have only stopped recently.

Astronomers discover the “dying echo” of supermassive black holes(2)

This time delay is Because the jet lobes themselves span about 3000 light-years from beginning to end, this means that after the source stops, they will take so long to completely recede.

The lead researcher of this study, Kohei Ichikawa, said: “We used NASA’s NuSTAR X-ray satellite, which is the best tool for observing current AGN activities. It can achieve non-detection, so we can detect activities. The galactic nucleus is completely dead.”

Astronomers discover the “dying echo” of supermassive black holes(3)

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p >This research can help astronomers better understand the life and death cycles of these AGNs, as well as the time frame in which these transitions occur. Previous studies have seen that calm galaxies suddenly become active and become turbulent quasars at a speed much faster than imagined. Even the Milky Way seems to have gone through these extremely active stages in its life cycle.

This research was originally published in the Astrophysical Journal and was recently published at the 238th meeting of the American Astronomical Society.