Spectroscopic study of the [OIII]λ5007 profile in Seyfert 1 galaxies

Abstract

The spectra of active galactic nuclei usually exhibit wings in some emission lines, such as [OIII]λλ5007,4959, with these wings generally being blueshifted and related to strong winds and outflows. The aim of this work was to analyse the [OIII] emission lines in broad line Seyfert 1 (BLS1) galaxies in order to detect the presence of wings, and to study the [OIII] line properties and their possible connection with the central engine. In addition, we attempted to compare the black hole mass distribution in both BLS1 galaxies with symmetric and blue-asymmetric [OIII] profiles. For this purpose, we carried out a spectroscopic study of a sample of 45 nearby southern BLS1 galaxies from the 6 Degree Field Galaxy survey. The [OIII] emission lines were well fitted using a single Gaussian function in 23 galaxies, while 22 objects presented a wing component and required a double-Gaussian decomposition. By computing the radial velocity difference between the wing and core centroids (i.e. ∆v), we found 18 galaxies exhibiting blueshifted wings, 2 objects presenting red wings and 2 galaxies showing symmetric wings (∆v=0). Moreover, ∆v was slightly correlated with the black hole mass. In addition, we computed the radial velocity difference of the blue-side full extension of the wing relative to the centroid of the core component through the blue emission parameter, which revealed a correlation with black hole mass, in agreement with previous results reported for narrow line galaxies. Finally, in our sample, similar black hole mass distributions were observed in both BLS1 galaxies with symmetric and blueshifted asymmetric [OIII] profiles.