We report the results of the first detection of Lyα in a narrow-line radio galaxy. Nearly simultaneous optical and UV observations of 3C 192 and 3C 223 allow the measurement of both Balmer and Lyman decrements. These line ratios are approximate functions of the interstellar reddening and of a parameter which is proportional to the amount of H I collisional excitation present. The reddening of 3C 192 is slightly larger than that due to our Galaxy, although 3C 223 may have a larger value. Both galaxies have intrinsic Balmer and Lyman decrements which are significantly steeper than case B, suggesting that the gas is photoionized by a fairly hard X-ray continuum. The deduced values of Lα/Hβ and Hα/Hβ compare favorably with predictions of recent models.
Digital Object Identifier (DOI)
Ferland, Gary J. and Osterbrock, Donald E., "The Hydrogen Line Spectra of Narrow-Line Radio Galaxies" (1985). Physics and Astronomy Faculty Publications. 176.