Astronomers discover a new radio source of unknown origin

Astronomers discover a new radio source of unknown origin

HST tri-color image of NGC 2082 overlaid with ASKAP and ATCA lines. The inset image at the bottom left provides a magnification of J054149.24–641813.7, which indicates the absence of any optical analog. Credit: Balzan et al., 2022.

During continuous radio observations of a spiral galaxy known as NGC 2082, Australian astronomers have discovered a mysterious, bright and compact radio source, which has the designation J054149.24–641813.7. The origin and nature of this source is unknown and needs further investigation. The result was reported in a research paper published May 23 in the preprint repository arXiv.

In general, radio sources are various objects in the universe that emit relatively large amounts of radio waves. Among the most powerful sources of this emission are pulsars, some nebulae, quasars, and Radio Galaxies.

Now, a team of astronomers led by Joel Balzan of the University of Western Sydney in Australia, has reported the discovery of a new radio source, the true nature of which remains uncertain. While observing NGC 2082 using the Australian Square Kilometer Pathfinder Array (ASKAP), the Australia Telescope Integrated Array (ATCA) and the Parks Radio Telescope, they identified a powerful radio source located 20 arcseconds from the galactic center. NGC 2082 is a G-type spiral galaxy in the constellation of Dorado, located about 60 million light-years from Earth, and about 33,000 light-years in diameter.

“We present continuous radio observations of NGC 2082 using the ASKAP, ATCA and Parkes telescopes from 888MHz to 9000MHz. About 20 arcs from the center of this nearby spiral galaxywe detected a bright, compact radio source, J054149.24–641813.7, of unknown origin,” the researchers wrote in the paper.

The study found that the radio luminosity of J054149.24-641813.7 at 888MHz is at a level of 129 EW/Hz and that it has a flat radio spectrum index (about 0.02). This, according to the astronomers, does not support a scenario in which J054149.24–641813.7 may be a supernova remnant (SNR) or pulsar, suggesting that the source may be of thermal origin.

The researchers note that the compact nature of J054149.24–641813.7 and its location in the outskirts of NGC 2082 are reminiscent of some fast radio blasts (FRBs). However, the results indicate that J054149.24–641813.7 is probably not bright enough to be a stable radio source with an embedded FRB predecessor.

The astronomers concluded that the most likely remaining possibility is that J054149.24–641813.7 is an extragalactic background source, such as a quasi-stellar object (QSO, a quasar), a radio galaxy or an active galactic nucleus (AGN). They added that the flat spectrum index along with the rather weak polarization at 5500 and 9000 MHz supports this hypothesis. However, there are currently no high-resolution adsorption data for neutral atomic hydrogen (HI) for NGC 2082, which could confirm this assumption.

“We found that the probability of finding such a source beyond NGC 2082 is P = 1.2 percent, and concluded that the likely origin of J054149.24–641813.7 is a background quasar or radio galaxy,” the research authors explained.

Astronomers discover a new circular radio source outside the galaxy

more information:
Joel CF Balzan et al., NGC 2082 Radio Connected Study. arXiv: 2205.11144v1 [astro-ph.GA]And the

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