2004/12/15 by Danilo Marchesini, D. Marchesini, A. Capetti +3 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Radio Astronomy Observations and Technology #astro-ph
paper · pdf · doi:10.1051/0004-6361:20042072
published as Astron.Astrophys. 433 (2005) 841-854 · Accepted for publication in A&A; high resolution version can be downloaded at http://www.astro.yale.edu/danilom/
arxiv created 2004/12/15 · openalex publication_date 2005/03/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present the first near-infrared (-band) homogeneous observations of a complete sub-sample of the 3CR radio catalogue comprising all High Excitation Galaxies (HEGs) at . After showing that the surface brightness decomposition technique to measure central point-like sources is affected by significant uncertainties for the objects in the studied sample, we present a new, more accurate method based on the color profile. Via this method we find a substantial nuclear -band excess in all but two HEGs – most likely directly associated with their nuclear emission – and we measure the corresponding 2.12 μm nuclear luminosities. Within the frame-work of the unification scheme for radio-loud active galactic nuclei, it appears that obscuration alone is not able to account for the different nuclear properties of the majority of the HEGs and Broad Line Radio Galaxies (BLRGs), and also scattering of the (optically) hidden nuclear light from a compact region must be invoked. More precisely, for ~70% of the HEGs the observed point-like optical emission is dominated by the scattered component, while in the -band both scattered and direct light passing through the torus contribute to the observed nuclear luminosity. The estimated fraction of scattered light ranges from a few tenths to a few percent, while the torus extinction is between mag with only a few exceptions with lower obscuration.