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Centro de Astrofísica da Universidade do Porto

GTC optical imaging of extremely red 5C radio galaxies at high redshift

A. Humphrey, M. Villar-Martín, P. Lagos

Abstract
Aims: We investigate the nature of seven unusual radio galaxies from the 5C catalogue that were previously known to have extremely red R-K colours, and for which emission lines were previously found to be weak or absent in their optical spectra.
Methods: We present and discuss u, g, or r images of these radio galaxies, obtained using the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) at the Gran Telescopio Canarias (GTC).
Results: We have detected all seven targets in our g-band imaging. Their optical emission is extended, and we tentatively detect a radio-optical alignment effect in this sample. A subset of our sample (three sources) shows broad-band spectral energy distributions that flatten out near the wavelength range of the g-band, implying a dominant contribution there due to young stars and/or scattered or reprocessed radiation from the active nucleus.

Keywords
galaxies: active, galaxies: evolution, galaxies: high-redshift, galaxies: jets, quasars: general, galaxies: star formation

Astronomy and Astrophysics
Volume 585
December 2015

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