Extended emission-line regions in low-redshift quasars

Abstract

Aims: We searched for the presence of extended emission-line regions (EELRs) around low-redshift QSOs. Methods: We observed a sample of 20 mainly radio-quiet low-redshift quasars (z<0.3) by means of integral field spectroscopy. After decomposing the extended and nuclear emission components, we constructed [O III] λ5007 narrow-band images of the EELR to measure the total flux. From the same data we obtained high S/N (>50) nuclear spectra to measure properties such as [O III]/Hβ flux ratios, Fe II equivalent widths and Hβ line widths. Results: A significant fraction of the quasars (8/20) show a luminous EELR, with detected linear sizes of several kpc. Whether or not a QSO has a luminous EELR is strongly related with nuclear properties, in the sense that an EELR was detected in objects with low Fe II equivalent width and large Hβ {FWHM}. The EELRs were detected preferentially in QSOs with larger black hole masses. There is no discernible relation, however, between EELR detection and QSO luminosity and Eddington ratio. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max- Planck-Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC)