Suzaku observations of 'bare' active galactic nuclei

TL;DR

This study analyzes Suzaku X-ray data of 25 'bare' AGN to investigate relativistic disc reflection, black hole spin, and the radio loudness dichotomy, finding a preference for rapidly rotating black holes and challenging previous assumptions about their relation to radio loudness.

Contribution

It provides a systematic spectral analysis of a large AGN sample, demonstrating the role of disc reflection and black hole spin in X-ray spectral features, with implications for SMBH growth and AGN classification.

Findings

Disc reflection can reproduce the broadband spectra of all sources.

A general preference for rapidly rotating black holes was found.

The radio loudness dichotomy is not solely determined by black hole spin.

Abstract

We present a X-ray spectral analysis of a large sample of 25 'bare' active galactic nuclei, sources with little or no complicating intrinsic absorption, observed with Suzaku. Our work focuses on studying the potential contribution from relativistic disc reflection, and examining the implications of this interpretation for the intrinsic spectral complexities frequently displayed by AGN in the X-ray bandpass. During the analysis, we take the unique approach of attempting to simultaneously undertake a systematic analysis of the whole sample, as well as a detailed treatment of each individual source, and find that disc reflection has the required flexibility to successfully reproduce the broadband spectrum observed for all of the sources considered. Where possible, we use the reflected emission to place constraints on the black hole spin for this sample of sources. Our analysis suggests a general preference for rapidly rotating black holes, which if taken at face value is most consistent with the scenario in which SMBH growth is dominated by prolonged, ordered accretion. However, there may be observational biases towards AGN with high spin in the compiled sample, limiting our ability to draw strong conclusions for the general population at this stage. Finally, contrary to popular belief, our analysis also implies that the dichotomy between radio loud/radio quiet AGN is not solely related to black hole spin.