Hamburger Sternwarte - Research|
Narrow-Line Seyfert 1 Galaxien im ROSAT All-Sky Survey
Narrow-Line Seyfert 1 galaxies (NLSy1) are a subgroup of Seyfert 1 galaxies,
in which the emission lines are relatively narrow. Seyfert 1 galaxies are
classified as NLSy1 if their emisson line have a full-width-half-maximum
FWHM < 2000 km/s. It was claimed that X-ray surveys select them
preferentially. We tested this statement by determining the fraction of NLSy1
in X-ray and optically selected AGN samples. We measured the linewidth of
Hβ in 473 Spectra of X-ray selected and in 235 Spectra of
optically selected AGN, which were obtained by
ROSAC and by HQS.
Fraction of NLSy1-Galaxies in Rass and optical (HQS) selected
The following results were obtained:
- In the mean the line widths increase with luminosity. Typical values are
<v> = 3000 km/s for Seyfert galaxies and <v> = 4300 km/s for
- NLSy1 are as frequent in optically as in X-ray selected samples (see
figure). At low luminosities (MB > -21) they make up 25-30% of
the whole Seyfert 1 population.
- There are no AGNs with FWHM < 2000 and quasar luminosities
(MB < -24), e.g. there are no NLQSO among quasars.
Collaborators: D.Engels, R.Keil
Last changed Wednesday, 31-March-2004 |