Optical emission-line spectrum of 3C 120
Spectrophotometric measurements are reported of the nuclear region of 3C 120. The relative intensities of the individual emission lines and the continuous spectrum were measured in the wavelength region lambda lambda 3346- 7065 (in the rest system of 3C 120). The Balmer decrement is quite steep and may be caused by interstellar extinction of an amount E/sub B--V/ = 0.50. However, it is more likely that the large decrement is the result of collisional or self- absorption effects. The observations by Wampler and Shields, Oke, and Sargent of strong He I and He II emission lines are confirmed. The relative strengths of the He I lines are inconsistent with pure recombination theory and suggest that collisional or radiative transfer processes are important. The [S II] ratio F(lambda 6717)/F(lambda 6731) = 0.91 corresponds to a mean electron density of N/ sub e/ (10$sup 4$/T)/sup $sup 1$$/$$sub 2$/ = 1.7 x 10$sup 3$ cm$sup -3$ in the region of [S II] emission. The [O III] ratio [F(lambda 5007) + F(4959)]/F(lambda 4363) = 23.1 (uncorrected for reddening) implies an electron temperature of 32,500$sup 0$K in the low-density limit N/sub e/ $Yields$ 0, and approximately 23,000$sup 0$K for a density of 10$sup 5$ cm$sup -3$. Broad emission features of Fe II are present in the spectrum. In particular, a weak emission line at lambda 6369 may be identified with an Fe II transition of multiplet (40). The profiles of the H I, He I, and He II lines are fairly symmetrical, with the full width at half maximum of the H I and He I lines approximately 2000 km s$sup -1$, while He II lambda 4686 appears to have somewhat wider wings. The narrower forbidden lines have widths of roughly 300 km s$sup -1$. A comparison of the relative forbidden line strengths to those of Cygnus A suggests the presence of a rather complicated distribution of density with degree of ionization in 3C 120. (auth)
- Research Organization:
- Univ. of California, Santa Cruz
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-33-027069
- OSTI ID:
- 4007640
- Journal Information:
- Publ. Astron. Soc. Pac., v. 87, no. 520, pp. 949-959, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
Similar Records
STRUCTURE AND FEEDBACK IN 30 DORADUS. I. OBSERVATIONS
A HYPERSPECTRAL VIEW OF THE CRAB NEBULA