Faint blue galaxy

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The faint blue galaxy (F.B.G.) problem in astrophysics first arose with observations starting in 1978 that there were more galaxies with a bolometric magnitude > 22 than then-current theory predicted.[1][2][3] Galaxies can appear faint because they are small or because they are far away. Neither explanation, nor any combination, initially matched the observations. The distribution of these galaxies has since been found to be consistent with cosmic inflation, measurements of the cosmic microwave background, and a nonzero cosmological constant, that is, with the existence of the now-accepted dark energy.[4][5] It thus serves as a confirmation of supernova observations requiring dark energy.

A second problem arose in 1988, with even deeper observations showing a much greater excess of faint galaxies.[6] These are now interpreted as dwarf galaxies experiencing large bursts of stellar formation, resulting in blue light from young, massive stars.[7] Thus F.B.G.s are extremely bright for their size and distance.

Most F.B.G.s appear between red-shift 0.5 and 2. It is believed that they disappear as separate objects by merger with other galaxies.[8][9]


  1. ^ Kron R 1978 Ph.D. Thesis, University of California, Berkeley
  2. ^ Peterson, B.A.; Ellis, R.S.; Kibblewhite, E.J.; Bridgeland, M.T.; Hooley, T.; Horne, D. (Nov 1, 1979), "Number magnitude counts of faint galaxies", Astrophysical Journal Letters, 233: L109–L113, Bibcode:1979ApJ...233L.109P, doi:10.1086/183087
  3. ^ Tyson, J. A.; Jarvis, J. F. (June 15, 1979), "Evolution of galaxies - Automated faint object counts to 24th magnitude", Astrophysical Journal Letters, 230: L153–L156, Bibcode:1979ApJ...230L.153T, doi:10.1086/182982
  4. ^ Yoshii, Yuzuru; Takahara, Fumio (Nov 1, 1989), "On the redshift-volume measurement of the cosmological density parameter", Astrophysical Journal, 346: 28–33, Bibcode:1989ApJ...346...28Y, doi:10.1086/167983
  5. ^ David C., Koo (June 21–23, 1989). "The evolution of field galaxies - Is Omega = 1?". Evolution of the universe of galaxies; Proceedings of the Edwin Hubble Centennial Symposium. Berkeley, CA: Astronomical Society of the Pacific. pp. 268–285. Bibcode:1990ASPC...10..268K.
  6. ^ Broadhurst, T.J.; Ellis, R.S.; Shanks, T. (Dec 1, 1988), "The Durham/Anglo-Australian Telescope faint galaxy redshift survey", Monthly Notices of the Royal Astronomical Society, 235 (3): 827–856, Bibcode:1988MNRAS.235..827B, doi:10.1093/mnras/235.3.827
  7. ^ Colless, Matthew; Ellis, Richard S.; Broadhurst, T.J.; Taylor, Keith; Peterson, Bruce A. (March 1993), "Faint blue galaxies - High or low redshift?", Monthly Notices of the Royal Astronomical Society, 261: 19–38, Bibcode:1993MNRAS.261...19C, doi:10.1093/mnras/261.1.19
  8. ^ Carlberg, R. G. (November 1992), "Merging and fast galaxy evolution", Astrophysical Journal Letters, 399 (1): L31–L34, Bibcode:1992ApJ...399L..31C, doi:10.1086/186599
  9. ^ Carlberg, R. G.; Charlot, Stephane (September 1992), "Faint galaxy evolution via interactions", Astrophysical Journal, 397 (1): 5–13, Bibcode:1992ApJ...397....5C, doi:10.1086/171759