The O III 5007 and H-alpha structure of the radio galaxy 3C 120.
Abstract
Calibrated optical imaging was done to study the morphology of the radio galaxy 3C 120, using narrow-band interference filters with FWHM = 9.6A - 10.2A tuned to the redshifted (z = 0.033) Hα and [O III] 5007A respectively in front of the image photon counting system (IPCS) at the Canada-France-Hawaii telescope. Several emission features are resolved for the first time with the spatial resolution of 1". Both Hα and [O III] 5007A emission-line pictures obviously contrast with the previous imaging reports. The barred shape of the radio galaxy is outlined by the distribution of the giant H II regions detected around the bright core. The conspicuous surrounding emissions display a "Z" structure (at P.A. 27^deg^) within a 1' field of view, covering 40 kpc, if H_0_ = 75 km s^-1^ Mpc ^-1^. The elongated core would have two components roughly aligned with P.A. = -25^deg^. The earlier "edge-on" structure is definitely resolved in three components: the main double elliptical core extended by two N-S condensations of about 5" (3-4 kpc) in extent. These line emissions are superimposed on a much fainter component, more obvious in [O III] 5007A than in Hα, which could be attributed to the underlying galaxy with the N-S major axis. The radial westwards 4" extension (P.A. = -95^deg^) detected in two emission lines coincides with the 6 cm and 20 cm radio jets, supporting the line-emitting gas tendency to spread in the same direction as the radio ejecta. This structure is continued outwards by a faint emission which describes a "bow-shaped" feature (at P.A. = 70^deg^) again much more prominent in [O III] 5007A than in Hα. A "counter-jet" is likely present at the east side of the nucleus (roughly P. A. = 110^deg^). Absolute fluxes in erg s^-1^ cm^-2^ measured within 20% accuracy are given for several positions of interest as well as for the whole galaxy (55" x 60") with F_T_ (Hα) = 3.65 10^-12^, F_T_([O III] 5007) = 4.35 10^-13^. These quantitative results are discussed and compared to earlier spectrophotometric values available in the literature.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- June 1988
- Bibcode:
- 1988A&A...199..105H
- Keywords:
-
- Emission Spectra;
- Galactic Nuclei;
- Galactic Structure;
- H Alpha Line;
- Isophotes;
- Radio Galaxies;
- H Ii Regions;
- Interstellar Gas;
- Seyfert Galaxies;
- Astrophysics