The X-ray nuclei of intermediate-redshift radio sources

By M. Hardcastle, D. Evans, Judith Croston. 2006

171 citations recorded by the source corpus.

We present a Chandra and XMM-Newtonspectral analysis of the nuclei of the radio galaxies and radio-loud quasars from the 3CRR sample in the redshift range 0.1 < z < 0.5. In the range of radio luminosity sampled by these objects, mostly FRIIs, it has been clear for some time that a population of radio galaxies (‘low-excitation radio galaxies’) cannot easily participate in models that unify narrow-line radio galaxie s and broad-line objects. We show that low-excitation and narrow-line radio galaxies have systematically different nuclear Xray properties: while narrow-line radio galaxies universa lly show a heavily absorbed nuclear X-ray component, such a heavily absorbed component is rarely found in sources classed as low-excitation objects. Combining our data with the results of our earlier work on the z < 0.1 3CRR sources, we discuss the implications of this result for unified models, for the origins of mid-infrared emission from radio sources, and for the nature of the apparent FRI/FRII dichotomy in the X-ray. The lack of direct evidence for accretion-related X-ray emission in FRII LERGs leads us to argue that there is a strong possibility that some, or most, FRII LERGs accrete in a radiatively inefficient mode. However, our result s are also consistent with a model in which the accretion mode is the same for low- and high-excitation FRIIs, with the lower accretion luminosities in FRII LERGs attributed instead to more efficient radio luminosity production in those objects.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/cf958919dfc21675bcd79dca19c0e9ae17b7f3be

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Citations in the corpus

BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog (2017, background): “This has been found to be the case for radio galaxies (Hardcastle et al. 2006, 2009), which very often show additional unobscured power-law emission.”
What drives the growth of black holes (2011, background): “…classifications) are typically hosted in less massive gas-rich galaxies (e.g., Willott et al., 2001; Chiaberge et al., 2005; Evans et al., 2006; Hardcastle et al., 2006, 2007; Baldi & Capetti, 2008; Kauffmann et al., 2008; Smolčić, 2009; Smolčić et al., 2009; Herbert et al., 2010;…”
EMU: Evolutionary Map of the Universe (2011, background): “They also lack the expected infrared emission from a dusty torus (see e.g. Whysong & Antonucci 2004; Ogle et al. 2006) and do not show accretion-related X-ray emission (Hardcastle et al. 2006; Evans et al. 2006).”
Radio galaxies and feedback from AGN jets (2020, background): “…boosted CMB from jets with Γ ∼ 10 (Tavecchio et al., 2000; Celotti et al., 2001), while attractive, has a number of problems (Stawarz et al., 2004; Hardcastle, 2006; Cara et al., 2013; Meyer et al., 2015) and it seems likely that at least some of these powerful jets have a synchrotron…”