Journal Article

Morphology and surface brightness evolution of <i>z</i>∼1.1 radio galaxies

Nathan Roche, Stephen Eales and Steve Rawlings

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 297, issue 2, pages 405-418
Published in print June 1998 | ISSN: 0035-8711
Published online June 1998 | e-ISSN: 1365-2966 | DOI:
Morphology and surface brightness evolution of z∼1.1 radio galaxies

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We use K′-band (2.1-µm) imaging to investigate the angular size and morphology of 10 6C radio galaxies, at redshifts 1≤z≤1.4. Two radio galaxies appear to be undergoing mergers, another contains, within a single envelope, two intensity peaks aligned with the radio jets, while the other seven appear consistent with being normal ellipticals in the K band.

Intrinsic half-light radii are estimated from the areas of each radio galaxy image above a series of thresholds. The 6C galaxy radii are found to be significantly smaller than those of the more radio-luminous 3CR galaxies at similar redshifts. This would indicate that the higher mean K-band luminosity of the 3CR galaxies reflects a difference in the size of the host galaxies, and not solely a difference in the power of the active nuclei.

The size-luminosity relation of the z∼1.1 6C galaxies indicates a 1.0–1.6 mag enhancement of their rest frame R-band surface brightness relative to either local ellipticals of the same size or FRII radio galaxies at z<0.2. The 3CR galaxies at z∼1.1 show a comparable enhancement in surface brightness. The mean radius of the 6C galaxies suggests that they evolve into ellipticals of LL* luminosity, and is consistent with their low-redshift counterparts being relatively small FRII galaxies ∼25 times lower in radio luminosity, or small FRI galaxies ∼1000 times lower in radio luminosity. Hence the 6C radio galaxies appear to undergo as much optical and radio evolution as the 3CR galaxies.

Keywords: galaxies: active; galaxies: evolution; galaxies: photometry; radio continuum: galaxies.

Journal Article.  0 words. 

Subjects: Astronomy and Astrophysics

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