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arXiv · 1609.06705

Orientation effects on spectral emission features of quasars

Susanna Bisogni·Alessandro Marconi·Guido Risaliti
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Abstract

We present an analysis of the orientation effects in SDSS quasar composite spectra. In a previous work we have shown that the equivalent width EW of the [OIII] λ5008Å line is a reliable indicator of the inclination of the accretion disk. Here, we have selected a sample of ~15,000 quasars from the SDSS 7th Data Release and divided it in sub-samples with different values of EW([OIII]). We find inclination effects both on broad and narrow quasars emission lines, among which an increasing broadening from low to high EW for the broad lines and a decreasing importance of the blue component for the narrow lines. These effects are naturally explained with a variation of source inclination from nearly face-on to edge-on, confirming the goodness of EW([OIII]) as an orientation indicator. Moreover, we suggest that orientation effects could explain, at least partially, the origin of the anticorrelation between [OIII] and FeII intensities, i.e. the well known Eigenvector 1.

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Susanna Bisogni, Alessandro Marconi, Guido Risaliti. 2016-09-21. Orientation effects on spectral emission features of quasars. https://doi.org/10.1093/mnras%2Fstw2324

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