New Rare “Green Bean Galaxy” Discovered Astronomers from New Mexico State University

Astronomers from New Mexico State University (NMSU) and other universities report the discovery of a rare class of new galaxies they call “green beans.” This discovery was made by Carl G. The Jansky Very Large Array (VLA) was featured in a research paper published May 29 on the preprint server arXiv.

The so-called “green beans” are very rare active galaxies that glow green due to strong radiation from the region around the central black hole. To date, only 17 such galaxies have been identified by the Sloan Digital Sky Survey (SDSS). Astronomers suspect that the rarity of these objects may be because they are going through a short-lived phase in their development. Now, a team of astronomers led by NMSU’s Kelly N. has discovered that these galaxies are extremely rare. Sanderson discovered another galaxy of this unusual type. They used the VLA to observe a widespread radio emission source in the sky called RGZ J123300.2+060325. Previous studies of this source, with a redshift of about 0.3, had suggested that it could be a Green Bean galaxy. “Here we present a new Green Bean galaxy at z = 0.304458 ± 0.000007 with extensive jet-induced radio emission,” the researchers wrote in their paper. The newly confirmed Green Bean galaxy has been named RGB1. The observations show that RGB1 has an extended emission line region (EELR) that was most likely photoionized by an active galactic nucleus (AGN). By analyzing the spectral age of the jet-induced extended radio emission in RGB1, the astronomers found that the duration of the jet-producing phase of the AGN is at least 6 million years. However, the collected data does not allow Sanderson’s team to confirm whether the jet-making phase is still ongoing. The observations also found several detached clouds surrounding RGB1, located up to about 123,000 light-years away from the center. The ionization profiles of these clouds suggest a decrease in the AGN’s ionizing photon production over the past 150,000 years. The researchers therefore assume that RGB1 was in a jet generation phase before the radiation-efficient accretion phase, which is reflected in the currently observed EELR emission. In summary, the authors of the paper stated that the origin of RGB1 remains unclear and further observations at multiple wavelengths are needed to draw a definitive conclusion. “It is unclear whether RGB1 was a HERG (highly excited radio galaxy) that changed into a LERG (lowly excited radio galaxy) or inactive galaxy during the past 150,000 years, or whether there was a ‘signature of extensive radio and optical emission’. Different accretion phases occurred one after the other,” the scientists concluded.

source:https://dx.doi.org/10.48550/arxiv.2405.19558