EW[OIII] as an Orientation Indicator for Quasars: Implications for the Torus

Frontiers in Astronomy and Space Sciences

Lusso, Elisabeta²  Bisogni, Susanna³  Risaliti, Guido⁴  Marconi, Alessandro⁴ 

[1] degli Studi di Firenze, Italy;Dipartimento di Fisica e Astronomia, UniversitàHarvard-Smithsonian Center for Astrophysics, United States;Osservatorio Astrofisico di Arcetri, INAF, Italy

关键词: galaxies: active;    galaxies: nuclei;    galaxies: Seyfert;    quasars: emission lines;    quasars: general;   

DOI  :  10.3389/fspas.2017.00048

学科分类：空间科学

来源: Frontiers

【 摘 要 】

We present an analysis of the average spectral properties of 12,000 SDSS quasars as a function of accretion disc inclination, as measured from the equivalent width of the [O III] 5007Šline. The use of this indicator on a large sample of quasars from the SDSS DR7 has proven the presence of orientation effects on the features of UV/optical spectra, confirming the presence of outflows in the NLR gas and that the geometry of the BLR is disc-like. Relying on the goodness of this indicator, we are now using it to investigate other bands/components of AGN. Specifically, the study of the UV/optical/IR SED of the same sample provides information on the obscuring “torus”. The SED shows a decrease of the IR fraction moving from face-on to edge-on sources, in agreement with models where the torus is co-axial with the accretion disc. Moreover, the fact we are able to observe the broad emission lines also in sources in an edge-on position, suggests that the torus is rather clumpy than smooth as in the Unified Model. The behaviour of the SED as a function of EW[OIII] is in agreement with the predictions of the clumpy torus models as well.

【 授权许可】

CC BY