Publication Date:
2020-01-08
Description:
We present a statistical analysis of the optical properties of an X-ray-selected Type 1 active galactic nucleus (AGN) sample, using high signal-to-noise ratio (S/N>20) spectra of the counterparts of the ROSAT/2RXS sources in the footprint of the SDSS-IV/SPIDERS (Spectroscopic IDentification of eROSITA Sources) programme. The final sample contains 2100 sources. It significantly extends the redshift and luminosity ranges (z? ∼? 0.01–0.80 and $L_{
m 0.1!-!2.4 , keV} sim
m 2.0 imes 10^{41}!-!1.0 imes 10^{46} , , erg , s^{-1}$) used so far in this kind of analysis. By means of a principal component analysis, we derive eigenvector (EV) 1 and 2 in an eleven-dimensional optical and X-ray parameter space, which are consistent with previous results. The validity of the correlations of the Eddington ratio L/LEdd with EV1 and the black hole mass with EV2 is strongly confirmed. These results imply that L/LEdd and black hole mass are related to the diversity of the optical properties of Type 1 AGNs. Investigating the relation of the width and asymmetry of H β and the relative strength of the iron emission $r_{
m Fe, small{II}}$, we show that our analysis supports the presence of a distinct kinematic region: the very broad line region. Furthermore, comparing sources with a red-asymmetric broad H β emission line to sources for which it is blue asymmetric, we find an intriguing difference in the correlation of the $
m Fe, small{II}$ and the continuum emission strengths. We show that this contrasting behaviour is consistent with a flattened, stratified model of the broad-line region, in which the $
m Fe, small{II}$-emitting region is shielded from the central source.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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