# Orientation effects on the near-infrared broad band emission of quasars

## TL;DR

This study uses the EW of the [OIII] emission line as an orientation indicator for quasars, revealing how their spectral energy distributions vary with orientation, supporting models of a clumpy, co-axial torus.

## Contribution

It demonstrates the effectiveness of EW[OIII] as an orientation indicator and links spectral energy distribution variations to quasar orientation, supporting clumpy torus models.

## Key findings

- Face-on quasars have flatter near-infrared SEDs.
- Edge-on quasars show about half the UV emission.
- Results support a clumpy, co-axial torus model.

## Abstract

We recently proposed the equivalent width (EW) of the narrow [OIII]5007{\AA} 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 7th Data Release at redshift $z < 0.8$ and with full width at half-maximum values of broad emission lines (H$\alpha$, H$\beta$, and MgII) larger than $2000$ km/s. 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[OIII]. We find that quasars with low EW[OIII] values (close to face-on position) have flatter near-infrared SEDs with respect to sources with high EW[OIII] values (almost edge-on). Moreover, quasars with high EW[OIII] values show a factor of $\sim 2$ lower emission in the UV to quasars with low EW[OIII] 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.