Green bean galaxy

The galaxy J0113+0106 with the Hyper Suprime-Cam
The galaxy J1155−0147 with the Hyper Suprime-Cam
These two images show the green bean galaxies J0113+0106 (top) and J1155−0147 (bottom) as seen by the Hyper Suprime-Cam on the Subaru Telescope.

Green bean galaxies (GBGs) are very rare astronomical objects that are thought to be quasar ionization echos.[1][2][3] They were discovered by Mischa Schirmer and colleagues R. Diaz, K. Holhjem, N.A. Levenson, and C. Winge.[1] The authors report the discovery of a sample of Seyfert-2 galaxies with ultra-luminous galaxy-wide narrow-line regions (NLRs) at redshifts z=0.2-0.6.[1]

While examining survey images taken with the 3.6-meter Canada–France–Hawaii Telescope (CFHT) atop 4200-m Mauna Kea, Hawaii, Schirmer noticed a galaxy with unusual colors—strongly peaking in the r filter, suggesting a spectral line.[1][4] In fact, the color is quite similar to the Green Pea galaxies (GPs), which are compact star-forming galaxies. However, the object which became known as a GBG is much larger.[1][5]

These galaxies are so rare that there is on average only one in a cube about 1.3 billion light-years across.[1] They were nicknamed GBGs because of their color and because they are superficially similar to, but larger than, GPs.[1] The interstellar gas in most GPs is ionized by UV-light from intense star formation, whereas the gas in GBGs is ionized by hard x-rays from an active galactic nucleus (AGN). The scarcity of GBGs indicates that this phenomenon is very rare, and/or very short-lived.[1]

GBGs are likely related to the object known as Hanny's Voorwerp, another possible quasar ionization echo.[6] GBGs are substantially different, though, as their luminosities, sizes and gas masses are 10-100 times higher than in other quasar ionisation clouds, for instance the 154 studied in Keel et al. 2012 (nicknamed 'voorwerpjes').[7] These 'voorwerpjes' are estimated to have bright phases that last between ~20,000 and 200,000 years.[7]

Possible formation mechanisms are currently under investigation. Likely, the giant gas outflows have been produced during the last stages in the life of super-luminous quasars, which subsequently experienced a rapid shut-down, e.g. due to a process known as AGN feedback.[8] The escaping X-rays from the former very active quasar state still ionize the gas, causing the ionization echo.

  1. ^ a b c d e f g h M. Schirmer; R. Diaz; K.Holhjem; N.A. Levenson; C. Winge (2013). "A Sample of Seyfert-2 Galaxies with Ultraluminous Galaxy-wide Narrow-line Regions: Quasar Light Echoes?". The Astrophysical Journal. 763 (1): 19. arXiv:1211.7098. Bibcode:2013ApJ...763...60S. doi:10.1088/0004-637X/763/1/60. S2CID 53386055.
  2. ^ "Galaxy-wide Echoes from the Past". 2012-12-05. Retrieved 2014-05-31.
  3. ^ ""Green-bean Galaxies" and the Demise of Quasars". 2012-12-05. Retrieved 2014-06-12.
  4. ^ "Galaxy-wide Echoes from the past". 2012-12-05. Retrieved 2014-06-12.
  5. ^ C. Cardamone; K. Schawinski; M. Sarzi; S.P. Bamford; N. Bennert; C.M. Urry; C. Lintott; W.C. Keel; J. Parejko; R.C. Nichol; D. Thomas; D. Andreescu; P. Murray; M.J. Raddick; A. Slosar; A. Szalay; J. Vandenberg (2009). "Galaxy Zoo Green Peas: Discovery of A Class of Compact Extremely Star-Forming Galaxies". Monthly Notices of the Royal Astronomical Society. 399 (3): 1191–1205. arXiv:0907.4155. Bibcode:2009MNRAS.399.1191C. doi:10.1111/j.1365-2966.2009.15383.x. S2CID 14663963.
  6. ^ C.J Lintott; K. Schawinski; W. Keel; H. van Arkel; N. Bennert; E. Edmondson; D. Thomas; D.J.B. Smith; P.D. Herbert; M.J. Jarvis; S. Virani; D. Andreescu; S.P. Bamford; K. Land; P. Murray; R.C. Nichol; M.J. Raddick; A. Slosar; A. Szalay; J. Vandenberg (2009). "Galaxy Zoo: 'Hanny's Voorwerp', a quasar light echo?". Monthly Notices of the Royal Astronomical Society. 399 (1): 129–140. arXiv:0906.5304. Bibcode:2009MNRAS.399..129L. doi:10.1111/j.1365-2966.2009.15299.x. S2CID 16752721.
  7. ^ a b W.C. Keel; S.D. Chojnowski; V.N. Bennert; K. Schawinski; C.J. Lintott; S. Lynn; A. Pancoast; C. Harris; A.M. Nierenberg; A. Sonnenfeld; R. Proctor (February 2012). "The Galaxy Zoo survey for giant AGN-ionized clouds: past and present black hole accretion events". Monthly Notices of the Royal Astronomical Society. 420 (1): 878–900. arXiv:1110.6921. Bibcode:2012MNRAS.420..878K. doi:10.1111/j.1365-2966.2011.20101.x. S2CID 13989196.
  8. ^ A.C. Fabian (2012). "Observational Evidence of Active Galactic Nuclei Feedback". Annual Review of Astronomy and Astrophysics. 50: 455–489. arXiv:1204.4114. Bibcode:2012ARA&A..50..455F. doi:10.1146/annurev-astro-081811-125521.