(ORDO NEWS) — Using NASA’s Chandra X-ray Observatory, astronomers from the Harvard-Smithsonian Center for Astrophysics (CfA) and other organizations have examined an active galaxy known as Markarian 78. They report that the source exhibits shock waves and strong X-rays.
Active galactic nuclei (AGNs) are accreting supermassive black holes located at the centers of some galaxies and emitting powerful high-energy radiation when they absorb gas and dust.
These cores can form jets that are mostly cylindrical, conical or parabolic in shape, which are observed even at megaparsec scales. In general, galaxies hosting AGNs are called active galaxies.
At a distance of about 521 million light years from Earth is the galaxy Markarian 78 (or Mrk 78 for short) – a Seyfert type II galaxy with a size of about 2400 light years.
The mid-infrared emission of this galaxy is dominated by AGN-heated dust, and the intrinsic luminosity of 2-10 keV of this source has been measured in the range from 8 to 12 tridecillion erg/s.
Previous observations of Mrk 78 have shown that its radio beam is deflected by the ionized gas it encounters and accelerates it. Moreover, it was found that the radio jet is disturbed by a compact cloud and expands into a leaky “bubble”, accelerating and burning the ionized gas seals.
To better understand the physical mechanisms behind the effects of the central AGN on the gas in Mrk 78, a team of astronomers led by CfA’s Francesca M.
Fornasini made X-ray observations of this galaxy using the Chandra Advanced CCD Imaging Spectrometer (ACIS). The results obtained were compared with previous radio studies of this source.
The researchers were able to image the interior of Mrk 78 with subarc X-ray resolution and detect complex morphology with spectral variations at scales from 650 to 6,500 light-years.
Although the observations found a compact (about 2,300 light-years in diameter) X-ray node on the eastern side of the source, coinciding with the radio node, its western side turned out to be quite different, since it is dominated by an extended X-ray loop (about 5,500 light-years from the nucleus and approximately 4,500 light-years in diameter).
In addition, in extended emission regions, astronomers have identified complex spectra requiring at least two components, either photoionized or thermal, and possible internal dimming. It has been noted that the spectral fit of this extended radiation favors models that include thermal models representing impact radiation.
According to scientists, the thermal energy that can be introduced into the interstellar medium by these final impacts is from 200 to 600 duodecillion erg/s.
From this, they calculated that the total power released by shock waves in these regions is in the range of 200 to 2,000 duodecillion erg/s.
Overall, the researchers noted that the tremors on the western side of Mrk 78 are about 3,260 light-years further away than those on the eastern side.
They suggest that soft X-ray shock radiation closer to the core is present but strongly absorbed, or that the shock gas closer to the core may be too hot to cool quickly.
These two hypotheses, in the opinion of the authors of the article, are the most plausible explanations for such a shift of the X-ray emission of the West from the outflow turnover radius.
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