Orientation effects on the near-infrared broad-band emission of quasars. Issue 1 (17th February 2019)

• Record Type: Journal Article
• Authors: Bisogni, Susanna; Lusso, Elisabeta; Marconi, Alessandro; Risaliti, Guido
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 485:Issue 1(2019)
• Page Start: 1405
• Page End: 1411
• Publication Date: 2019-02-17
• Subjects: galaxies: active -- galaxies:nuclei -- quasars: general -- galaxies: Seyfert; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz495
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We recently proposed the equivalent width (EW) of the narrow [O iii ]5007 Å emission line as an orientation indicator for active galactic nuclei. We tested this method on about 12 300 optically selected broad-line quasars from the SDSS seventh Data Release at redshift z < 0.8 and with full width at half-maximum values of broad emission lines (H α, H β, and Mg ii ) larger than 2000 km s −1 . We now examine their spectral energy distributions (SEDs) using broad-band photometry from the near-infrared to the ultraviolet to look for variations in the overall shape as a function of the EW[O iii ]. We find that quasars with low EW[O iii ] values (close to face-on position) have flatter near-infrared SEDs with respect to sources with high EW[O iii ] values (almost edge-on). Moreover, quasars with high EW[O iii ] values show a factor of ∼2 lower emission in the UV to quasars with low EW[O iii ] values. Our findings indicate that the torus is clumpy and, on average, co-axial with the accretion disc and broad-line region, in agreement with the most recent theoretical models for the obscuring torus.