SIMBAD references

2010A&A...511A..64V - Astronomy and Astrophysics, volume 511, A64-64 (2010/2-2)

Dust tori in radio galaxies.

VAN DER WOLK G., BARTHEL P.D., PELETIER R.F. and PEL J.W.

Abstract (from CDS):

We investigate the quasar - radio galaxy unification scenario and detect dust tori within radio galaxies of various types. Using VISIR on the VLT, we acquired sub-arcsecond (∼0.40") resolution N-band images, at a wavelength of 11.85 µm, of the nuclei of a sample of 27 radio galaxies of four types in the redshift range z=0.006-0.156. The sample consists of 8 edge-darkened, low-power Fanaroff-Riley class I (FR-I) radio galaxies, 6 edge-brightened, class II (FR-II) radio galaxies displaying low-excitation optical emission, 7 FR-IIs displaying high-excitation optical emission, and 6 FR-II broad emission line radio galaxies. Out of the sample of 27 objects, 10 nuclei are detected and several have constraining non-detections at sensitivities of 7mJy, the limiting flux a point source has when detected with a signal-to-noise ratio of 10 in one hour of source integration. On the basis of the core spectral energy distributions of this sample we find clear indications that many FR-I and several low-excitation FR-II radio galaxies do not contain warm dust tori. At least 57±19 percent of the high-excitation FR-IIs and almost all of the broad line radio galaxies exhibit excess infrared emission, which must be attributed to warm dust reradiating accretion activity. The FR-I and low-excitation FR-II galaxies are all of low efficiency, which is calculated as the ratio of bolometric to Eddington luminosity Lbol/LEdd<10–3. This suggests that thick tori are absent at low accretion rates and/or low efficiencies. The high-excitation FR-II galaxies are a mixed population with three types of nuclei: 1) low efficiency with dust torus; 2) low efficiency with weakly emitting dust torus; and 3) high efficiency with weak dust torus. We argue that the unification viewing angle range 0-45 degrees of quasars should be increased to ∼60 degrees, at least at lower luminosities.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: jets - galaxies: nuclei - infrared: galaxies - radiation mechanisms: non-thermal - radiation mechanisms: thermal

Simbad objects: 28

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