New ‘Green Bean’ Galaxy Discovered Glowing Around a Central Black Hole

New 'Green Bean' Galaxy Discovered Glowing Around a Central Black Hole
(Photo: Wikimedia Commons/CFHT/ESO/M. Schirmer)

Researchers discovered a new galaxy from the rare class called "green bean."

New Rare Green Bean Galaxy Discovered

Kelly N. Sanderson of New Mexico State University and her team of astronomers have discovered another green bean galaxy. A new study identified RGZ J123300.2+060325 as an extended radio emission source they had seen in the sky using the VLA telescope. This source is located at a redshift of about 0.3. and previous research has suggested that it could be a green bean galaxy.

"Green beans" are extremely uncommon active galaxies. They glow green due to the strong radiation from the area surrounding a central black hole. The Sloan Digital Sky Survey (SDSS) has found only 17 of these galaxies thus far.

The newly discovered galaxy RGB1 was assigned to the recently discovered green bean galaxy. The measurements demonstrate an extended emission line region (EELR) in RGB1, which is most likely photoionized by an active galactic nucleus (AGN).

Astronomers discovered that the jet production phase of the AGN lasts for at least six million years by examining the spectral age of the jet-induced extended radio emission in RGB1. Sanderson's team is unable to verify, though, with the data gathered, whether the jet generation phase is still in progress.

The scientists concluded that it is unclear whether RGB1 was a HERG [high excitation radio galaxy] that evolved over the past ∼0.15 Myr into either a LERG [low excitation radio galaxy] or an inactive galaxy or whether the extended radio and optical emission trace different accretion phases that happened sequentially.

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What's a Green Bean Galaxy?

Green bean galaxies (GBGs) are extremely uncommon celestial objects believed to represent echoes of ionization from quarks. Mischa Schirmer and her colleagues R. Diaz, N.A. Levenson, C. Holhjem, and K. Winge were the first to discover it. At redshifts of z=0.2-0.6, the scientists report finding a sample of Seyfert-2 galaxies with ultra-luminous galaxy-wide narrow-line regions (NLRs).

Examining survey photos obtained atop 4200-meter Mauna Kea, Hawaii, with the 3.6-meter Canada-France-Hawaii Telescope (CFHT), Schirmer discovered a galaxy with peculiar colors-strongly peaking in the r filter, suggesting a spectral line. The color is very close to the compact star-forming galaxies known as Green Pea galaxies (GPs). However, the item that came to be called a GBG is substantially bigger.

Due to their extreme rarity, there is just one of these galaxies on average in a cube that is 1.3 billion light-years across. Because of their hue and the fact that they resemble GPs on the surface but are larger, they were given the moniker GBGs. Whereas harsh X-rays ionize the gas in GBGs from an active galactic nucleus (AGN), the interstellar gas in most GPs is ionized by UV radiation from vigorous star formation.

The dearth of GBGs suggests that this phenomenon is extremely uncommon and/or transient. The object known as Hanny's Voorwerp, another potential quasar ionization echo, is probably connected to GBGs.

However, GBGs vary significantly from other quasar ionization clouds, such as the 154 investigated in Keel et al. (2012) (dubbed "voorwerpjes"), in that they have luminosities, diameters, and gas masses that are 10-100 times greater. The expected duration of the dazzling stages of these "voorwerpjes" is ~20,000-200,000 years.