Evidence that the z = 3.4 radio galaxy B2 0902+34 may be a protogalaxy

Eales, Stephen Anthony ORCID: https://orcid.org/0000-0002-7394-426X, Rawlings, S., Puxley, P., Rocca-Volmerange, B. and Kuntz, K. 1993. Evidence that the z = 3.4 radio galaxy B2 0902+34 may be a protogalaxy. Nature 363 (6425) , pp. 140-142. 10.1038/363140a0

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Abstract

THE monochromatic luminosities of high-redshift (z > 3) radio galaxies rise steeply between wavelengths of about 2,000 and 5,000 Å, to form a characteristic 'red bump'1–6. It is usually assumed that this bump arises from the photospheric emission of red, post-main-sequence stars. For a sufficient number of stars of this type to have evolved, however, these galaxies must be at least 0.4–2 Gyr old; yet z=3 corresponds to only 1.7 Gyr after the Big Bang (assuming a Hubble constant of 50 km s−1 Mpc−1 and that Ω0 = 1), bringing the larger age estimates uncomfortably close to the beginning of the Universe. Here we show that, at least in the case of the high-redshift radio galaxy B2 0902 + 34, the basic assumption is incorrect: the red bump is caused not by photospheric emission from post-main-sequence stars, but by the presence of bright emission lines from doubly ionized oxygen. Both the spec-trum and the luminosity of the underlying continuum suggest that B2 0902 + 34 is a galaxy observed during its initial burst of star formation.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Subjects:	Q Science > QB Astronomy
Publisher:	Nature Publishing Group
ISSN:	0028-0836
Last Modified:	24 Oct 2022 11:16
URI:	https://orca.cardiff.ac.uk/id/eprint/47532

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