Emission-line outflows in PKS1549−79: the effects of the early stages of radio-source evolution? |
| |
| Authors: | C Tadhunter K Wills R Morganti T Oosterloo R Dickson |
| |
| Institution: | 1Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH;2Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA Dwingeloo, the Netherlands;3Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire SK11 9DL |
| |
| Abstract: | We present new spectroscopic observations of the southern radio galaxy   . Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including O iii ] λλ 5007, 4959, are unusually broad for a narrow-line radio galaxy  , and are blueshifted by 600 km s?1 relative to the low-ionization lines such as O ii ] λλ 3726,3729. The O ii ] lines are also considerably narrower  than the O iii ] lines, and have a redshift consistent with that of the recently detected H i 21-cm absorption-line system. Whereas the kinematics of the O iii ] emission lines are consistent with outflow in an inner narrow-line region, the properties of the O ii ] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H i absorption-line system. The unusually broad O iii ] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that  is a radio source in an early stage of evolution. |
| |
| Keywords: | galaxies: active galaxies: individual: " target="_blank"> quasars: emission lines quasars: general |
|
|
