The formation epoch of massive ellipticals, as traced by radio galaxies

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

I review the current status of an on-going investigation into the stellar and dynamical ages of the oldest known galaxies at z > 1. The spectroscopic data, when compared with the predictions of a range of recent evolutionary synthesis models, continue to indicate that the oldest galaxies at z similar or equal to 1.5 are already > 3 Gyr old. Moreover, comparison with new models which incorporate chemical evolution, suggests that this result may be less sensitive to the assumed metallicity than was previously suspected. Such ages should therefore be taken seriously as constraints both on theories of galaxy formation and on cosmological models. Dynamically these objects also appear well evolved; they display de Vaucouleurs surface brightness profiles, and I demonstrate that their HST-derived morphological parameters place them on the same Kormendy relation as the z similar or equal to 1 3CR galaxies. Finally I consider the ages of these intermediate redshift objects in the context of our recently completed SCUBA sub-mm survey of radio galaxies spanning the redshift range z = 1 --> 4. These data indicate that the main epoch of star-formation in radio galaxies lies at z similar or equal to 4, a result which fits naturally with the ages of the oldest galaxies at z = 1.5 within an open Universe.

Original languageEnglish
Title of host publicationHY-REDSHIFT UNIVERSE: GALAXY FORMATION AND EVOLUTION AT HIGH REDSHIFT
EditorsAJ Bunker, WJM VanBreugel
Place of PublicationSAN FRANCISCO
PublisherASTRONOMICAL SOC PACIFIC
Pages133-144
Number of pages4
ISBN (Print)1-58381-019-6
Publication statusPublished - 1999
EventInternational Meeting on the Hy-Redshift Universe - Galaxy Formation and Evolution at High Redshift - BERKELEY
Duration: 21 Jun 199924 Jun 1999

Conference

ConferenceInternational Meeting on the Hy-Redshift Universe - Galaxy Formation and Evolution at High Redshift
CityBERKELEY
Period21/06/9924/06/99

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