Seeing and aperture effects on [O III]-based flux calibration of AGN spectra. NGC 3516 : a case study

• 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

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

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

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)