Old galaxies at high redshift and the cosmological constant

Lawrence M. Krauss

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


In a recent striking discovery, Dunlop et al. (1996) observed a galaxy at redshift z = 1.55 with an estimated age of 3.5 Gyr. This is incompatible with age estimates for a flat matter-dominated universe unless the Hubble constant is less than 45 km s-1 Mpc-1. While both an open universe and a universe with a cosmological constant alleviate this problem, I argue here that this result favors a nonzero cosmological constant, especially when it is considered in light of other cosmological constraints: (1) for the favored range of matter densities, the constraint is more stringent than the globular cluster age constraint, which already favors a nonzero cosmological constant; (2) the age-redshift relation for redshifts of order unity implies that the ratio between the age associated with redshift 1.55 and the present age is also generally larger for a cosmological constant-dominated universe than for an open universe; (3) structure formation is generally suppressed in low-density cosmologies, arguing against early galaxy formation. The additional constraints imposed by the new observation on the parameter space of h versus Ωmatter (where H = 100 h km s-1 Mpc-1) are derived for both cosmologies.

Original languageEnglish (US)
Pages (from-to)466-469
Number of pages4
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1997
Externally publishedYes


  • Cosmology: theory
  • Dark matter
  • Distance scale
  • Galaxies: evolution
  • Large-scale structure of universe

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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