The optical properties of low redshift radio galaxies

Govoni, F.; Falomo, R.; Fasano, G.; Scarpa, R.
Referencia bibliográfica

Astronomy and Astrophysics, v.353, p.507-527 (2000)

Fecha de publicación:
1
2000
Número de autores
4
Número de autores del IAC
0
Número de citas
63
Número de citas referidas
56
Descripción
We present morphological and photometric properties of 79 low redshift (z<=0.12) radio galaxies extracted from two radio flux limited samples of radio sources. All objects are imaged in the R band and for a subsample we have also obtained B band images. The sample includes sources of both FRI and FRII radio morphological type. Through the decomposition of the luminosity profiles and the analysis of the structural profiles (ellipticity, PA, c4) of the galaxies we are able to characterize in detail the optical properties of the radio galaxies. It is found that most of host galaxies are luminous bulge dominated systems similar to normal giant ellipticals. Some cases of additional disk components are found whose spheroid-to-disk luminosity ratio is similar to that found in S0 galaxies. The average absolute magnitude is < MHOST(tot) >=-24.0 with a clear trend for FRI sources to be ~ 0.5 mag brighter than FRII galaxies. In about 40% of the objects observed we find an excess of light in the nucleus that is attributed to the presence of a nuclear point source whose luminosity is on average ~ 1-2% of the total flux of the host galaxy. The luminosity of these nuclear point sources appears correlated with the core radio power of the galaxies. Radio galaxies follow the same mu_e - R_e relationship as normal elliptical galaxies. The distribution of ellipticity, the amount of twisting and shape of isophotes (boxy, disky) do not differ significantly from other ellipticals. The evidence for recent interactions is therefore rather modest. Finally on average radio galaxies are bluer and have a color dispersion larger than normal elliptical galaxies, and the average color gradient in radio galaxies appears slightly steeper than in normal ellipticals. These results support a scenario where radio emission is weakly related with the overall properties and/or the activity have negligible effects on the global characteristics of the host galaxy. Based on observations collected at the European Southern Observatory, La Silla, Chile. Based on observations collected at the Nordic Optical Telescope, La Palma.