A 3.5-Gyr-old galaxy at redshift 1.55

James Dunlop, John Peacock, Hyron Spinrad, Arjun Dey, Raul Jimenez, Daniel Stern, Rogier Windhorst

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Abstract

One of the most direct methods of constraining the epoch at which the first galaxies formed - and thereby to constrain the age of the Universe - is to identify and date the oldest galaxies at high redshift. But most distant galaxies have been identified on the basis of their abnormal brightness in some spectral region1-4; such selection criteria are biased towards objects with pronounced nuclear activity or young star-forming systems, in which the spectral signature of older stellar populations will be concealed. Here we report the discovery of a weak and extremely red radio galaxy (53W091) at z = 1.55, and present spectroscopic evidence that its red colour results from a population of old stars. Comparing our spectral data with models of the evolution of stellar populations, we estimate that we are observing this galaxy at least 3.5 Gyr after star-formation activity ceased. This implies an extremely high formation redshift (z > 4) for 53W091 and, by inference, other elliptical galaxies. Moreover, the age of 53W091 is greater than the predicted age of the Universe at z = 1.55, under the assumption of a standard Einstein-de Sitter cosmology (for any Hubble constant greater than 50km s-1 Mpc-1), indicating that this cosmological model can be formally excluded.

Original languageEnglish (US)
Pages (from-to)581-584
Number of pages4
JournalNature
Volume381
Issue number6583
StatePublished - 1996

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galaxies
universe
stars
Hubble constant
spectral signatures
radio galaxies
elliptical galaxies
inference
cosmology
star formation
brightness
time measurement
color
estimates

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Cite this

Dunlop, J., Peacock, J., Spinrad, H., Dey, A., Jimenez, R., Stern, D., & Windhorst, R. (1996). A 3.5-Gyr-old galaxy at redshift 1.55. Nature, 381(6583), 581-584.

A 3.5-Gyr-old galaxy at redshift 1.55. / Dunlop, James; Peacock, John; Spinrad, Hyron; Dey, Arjun; Jimenez, Raul; Stern, Daniel; Windhorst, Rogier.

In: Nature, Vol. 381, No. 6583, 1996, p. 581-584.

Research output: Contribution to journalArticle

Dunlop, J, Peacock, J, Spinrad, H, Dey, A, Jimenez, R, Stern, D & Windhorst, R 1996, 'A 3.5-Gyr-old galaxy at redshift 1.55', Nature, vol. 381, no. 6583, pp. 581-584.
Dunlop J, Peacock J, Spinrad H, Dey A, Jimenez R, Stern D et al. A 3.5-Gyr-old galaxy at redshift 1.55. Nature. 1996;381(6583):581-584.
Dunlop, James ; Peacock, John ; Spinrad, Hyron ; Dey, Arjun ; Jimenez, Raul ; Stern, Daniel ; Windhorst, Rogier. / A 3.5-Gyr-old galaxy at redshift 1.55. In: Nature. 1996 ; Vol. 381, No. 6583. pp. 581-584.
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