Mexican astronomers recently have reported the discovery of seven new large extragalactic radio sources called giant radio galaxies (GRG). They were found by visual inspection of radio images provided by two astronomical radio surveys.
GRG are radio galaxies with an overall projected linear length exceeding at least 3.3 million light years. They are rare objects grown in low-density environments. They are important for astronomers to study the formation and the evolution of radio sources.
Jonatan Rentería Macario of the Autonomous University of Zacatecas and Heinz Andernach of the University of Guanajuato, lately analyzed images available in two recent radio surveys covering large areas of sky. The data provided by the Jansky Very Large Array (JVLA) 1-2 GHz Snapshot Survey of SDSS Stripe82 and the 150-MHz LOFAR Two-metre Sky Survey Preliminary Data Release (LoTSS-PDR) allowed the researchers to distinguish an impressive number of more than 2,000 extended features suggesting the presence of large radio galaxies. As a result, they confirmed the existence of seven new GRGs.
For the search, they selected two recent radio surveys that cover large areas of sky, the JVLA 1-2 GHz Snapshot Survey of SDSS Stripe82 and the 150-MHz LOFAR Two-metre Sky Survey Preliminary Data Release (LoTSS-PDR). Two of the seven new GRGs reported in the paper were detected by the JVLA Snapshot Survey, while the rest was found the data provided by LoTSS-PDR. The largest of the newly discovered GRGs, designated J1301+5105, has the projected linear size of about 8.44 million light years, making it one of the biggest giant radio galaxies known to date. Currently, with a projected size of approximately 16 million light years, the J1420-0545 holds the title of the largest giant radio galaxy discovered so far.
The J0152+0015 is the smallest GRG reported in the study. Its projected linear size is approximately 3.35 million light years. The rest of the giant radio galaxies reported in the paper have sizes ranging from 4.08 to 5.09 million light years. According to the study, other interesting radio sources found by the two surveys will be inspected in more detail in the future, which could reveal the presence of more GRGs, especially radio-faint and distant ones.
In concluding remarks, the researchers noted that their discovery proved that visual inspection of radio images is a successful method for finding new GRGs. Their results show that the current and forthcoming low-frequency surveys with excellent sensitivity to low surface brightness feature have a large potential to discover significant amounts of giant radio galaxies as well as sources of complex or currently unknown types of morphologies.
Click here to read the detailed findings.
