Two supermassive black holes hidden by dust and gas found

NGC 1448 in an image combining data from the Carnegie-Irvine Galaxy Survey in the optical range and NuSTAR in the X-ray range (Image NASA/JPL-Caltech/Carnegie-Irvine Galaxy Survey)
NGC 1448 in an image combining data from the Carnegie-Irvine Galaxy Survey in the optical range and NuSTAR in the X-ray range (Image NASA/JPL-Caltech/Carnegie-Irvine Galaxy Survey)

At the American Astronomical Society meeting the results of the study of galaxies NGC 1448 and IC 3639 were presented showing how they led to the identification of supermassive black holes at their centers. A team of researchers used NASA’s NuSTAR Space Telescope to detect the high energy X-ray emission from them and see beyond the dust and gas that hid those areas.

The galaxies NGC 1448 and IC 3639 are far respectively 38 and 170 million light years from Earth, relatively near in astronomical terms. Nevertheless, so far astronomers couldn’t examine the area around them because it’s surrounded by a considerable amount of dust and gas that absorbs most electromagnetic frequencies.

So far, astronomers could examine the activity in an area a bit more external, which is quite vast. In fact, the galaxies NGC 1448 and IC 3639 have what are called active galactic nuclei, a class of objects that includes quasars and blazars. The supermassive black holes at their centers generate huge amounts of energy and great amounts of dust and gas surrounding them are heated to the point of emitting electromagnetic radiation at all frequencies.

The NuSTAR space telescope was launched in June 2012 also to solve such problems. Thanks to its sensitivity at high energy X-rays it can detect the ones coming from the donut-shaped region of dust and gas surrounding the supermassive black holes instead of the many electromagnetic frequencies at which the whole active nuclei of the two galaxies shine.

The galaxy IC 3639 was already studied using NASA’s Chandra and JAXA’s Suzaku space telescopes but their sensitivity at high-energy X-rays was not enough. They allowed to identify its active nucleus but not to see the area around the supermassive black hole. Thanks to the NuSTAR space telescope it was also possible to measure the amount of materials obscuring that area and to understand how much energy is generated.

Interesting results also came from an exam of the core of galaxy NGC 1448. The observations made with the NuSTAR space telescope were combined with those of ESO’s New Technology Telescope (NTT) at La Silla. NuSTAR identified the precise position of the supermassive black hole at the center of the galaxy, allowing the astronomers to indirectly locate it in the images at visible light of NTT.

This combination of different telescopes also allowed to locate in the galaxy NGC 1448 a large population of young stars. This suggests that they are created at the same time in which the supermassive black hole swallows dust and gas. It’s a discovery that would deserve a separate study.

The use of the NuSTAR Space Telescope to study supermassive black holes hidden by dust and gas was described for the first time in a study published in July 2015 in “The Astrophysical Journal”. Its success led to more research on other galaxies such as NGC 1448 and IC 3639 with other positive results.

IC 3639 in an image combining data from the Hubble Space Telescope and from ESO (Image NASA/JPL-Caltech/ESO/STScI)
IC 3639 in an image combining data from the Hubble Space Telescope and from ESO (Image NASA/JPL-Caltech/ESO/STScI)

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