The ISOPHOT - MAMBO survey of 3CR radio sources: Further evidence for the unified schemes

Abstract

Abstract. We present the complete set of ISOPHOT observations of 3CR radio galaxies and quasars, which are contained in the ISO Data Archive, providing 75 mid-and far-infrared spectral energy distributions (SEDs) between 5 and 200 µm. For 28 sources they are supplemented with MAMBO 1.2 mm observations and for 15 sources with new submillimetre data from the SCUBA archive. The sample includes flat and steep spectrum quasars, broad and narrow line radio galaxies, as well as Fanaroff-Riley FR 1 and FR 2 types. The SED shapes exhibit a diversity in the infrared (IR), ranging from a smooth dominating synchrotron component in flat spectrum sources to a thermal dust bump around 60−100 µm in steep spectrum sources. The detection rate of a thermal bump in more than 50% of the cases suggests that dust emission may be a general phenomenon in these sources. We check the orientation-dependent unified scheme, in which the powerful FR 2 narrow line galaxies are quasars viewed at high inclination, so that their nuclei are hidden behind a dust torus intercepting the optical-ultraviolet AGN radiation and reemitting it in the infrared. We find that (1) both the quasars and the galaxies show a high mid-to far-infrared luminosity ratio typical for powerful AGNs and (2) -when matched in 178 MHz luminosity -both show the same ratio of isotropic farinfrared to isotropic 178 MHz lobe power. Therefore, from our large sample investigated here we find strong evidence for the orientation-dependent unification of the powerful FR 2 galaxies with the quasars. The distribution of the dust-to-lobe luminosity ratio shows a dispersion which we suggest to be most likely due to the additional influence of evolution and environment superposed on the orientation-dependent unification. We discuss our data also in the frame of the receding torus model. At the high 178 MHz luminosities of our sources above 10 26.5 W/Hz we do not find any support for this model in its original formulation and therefore we propose a refinement: The scale height of the torus might not be independent of luminosity, rather it may increase at high luminosities due to the impact of supernovae from starbursts accompanying the AGN phenomena.

The asymmetric radio structure and record jet of giant quasar 4C 34.47

“…Consistency with aspect-dependent unification was also found in optical and infrared studies of the AGN and their host galaxies (e.g., Ogle et al 1997;Dunlop et al 2003;Haas et al 2004Haas et al , 2005. Open issues obviously remain, such as the torus opening angle (e.g., Grimes et al 2004), the nature of the class of broad line radio galaxies (e.g., Dennett-Thorpe et al 2000;van Bemmel & Barthel 2001), and the nature of low excitation radio galaxies, LERGs (e.g., Hardcastle 2004) as well as mid-infrared weak radio galaxies (e.g., Ogle et al 2006;van der Wolk et al 2010).…”

ChandraandXMM‐NewtonObservations of a Sample of Low‐Redshift FR I and FR II Radio Galaxy Nuclei

“…If FR I-type radio galaxies do indeed harbor luminous accretion flows surrounded by very dusty structures, one would expect to detect significant infrared emission in the centers of these sources. Such a scenario can be ruled out from Infrared Space Observatory (ISO) observations of a sample of 3CR FR I-and FR II-type radio galaxies ( Müller et al 2004;Haas et al 2004). None of the FR I sources exhibit any high midinfrared (MIR) or far-infrared ( FIR) dust luminosity, which would be expected for an intrinsically powerful, but highly obscured, AGN (cf.…”

Star formation inz> 1 3CR host galaxies as seen byHerschel

“…constraining the cold dust temperature) requires sampling the full rest-frame infrared-submm spectral energy distribution (SED) of the studied objects. Earlier far-infrared (FIR) studies failed to provide strong constraints on the FIR properties for relatively large samples of powerful radio-loud AGN because of their small detection fractions and only limited rest-frame FIR wavelength coverage (Heckman et al 1992;Hes et al 1995;Meisenheimer et al 2001;Siebenmorgen et al 2004;Haas et al 2004;Cleary et al 2007). …”