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Seeing and aperture effects on [O III]-based flux calibration of AGN spectra. NGC 3516: a case study
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1992 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 266, no 1, 72-7676 p.Article in journal (Refereed) Published
Abstract [en]

In variability studies of the broad emission lines in the spectra of active galactic nuclei, the narrow emission lines are generally used to flux calibrate spectra taken at different epochs to each other. In objects where the narrow-line region is resolved, seeing affects the ratio of narrow-line flux to broad-line and continuum flux entering the aperture since the broad-line region and the continuum source are unresolved. Thus observing under different seeing conditions introduces artificial correlated variations of the continuum and broad-line fluxes if one assumes the narrow lines to be constant in flux. The authors show that one can correct for this effect by simulating seeing variations using a narrow-band [O III] image, taken in good seeing conditions, of the nearby Seyfert 1 galaxy NGC 3516, in which the narrow-line region is clearly resolved and extends over more than 20". They also show that centring the aperture on the object consistently is very important and miscentring is also a source of artificial variability of the broad-line and continuum fluxes

Place, publisher, year, edition, pages
1992. Vol. 266, no 1, 72-7676 p.
Keyword [en]
Experimental/ astronomical spectra, oxygen, Seyfert galaxies, visible astronomical observations/ visible, forbidden line, O III, AD 1989 12 23, aperture effects, flux calibration, spectra, NGC 3516, broad emission lines, narrow emission lines, narrow-line region, seeing, continuum flux, nearby Seyfert 1 galaxy, 500.7 nm, O/ A9850R Active and peculiar galaxies A9850G Radiation and spectra of galaxies A9580J Photographic region astronomical observations/ wavelength 5.007E-07 m/ O/el
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-197173ISI: 4326131OAI: oai:DiVA.org:uu-197173DiVA: diva2:611955
Available from: 2013-03-19 Created: 2013-03-18 Last updated: 2017-12-06

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van Groningen, E.

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