EMISSION LINES

The Data

Table I

There are at least six other quasars which belong to the same spectral class (Varshni, 1976) as 0420-388. We summarize the available data on emission lines for all these quasars in Table I. There are a number of other quasars (Hewitt and Burbidge, 1987), which appear to belong to this spectral group but the available data are too poor to make a definite assignment. We give here a partial list of such quasars in two parts :

(a) 0045-036, 0114-089, 0132-197, 0143-015, 0143-010, 0334-204, 1206+119, 1251+367, 1306+294, 1512+132, 1607+183.
(b) 0116-288, 0242-301, 0937+118, 0938+450, 1424-118, 1657+265.

In the spectra of all of these quasars, the most important feature appears to be a line in the vicinity of 5020 Å. In the redshift hypothesis, some authors have interpreted this line as Lyman alpha 1216 Å, resulting in a `redshift' of about 3.13 for the quasars in the (a) list, while some others have interpeted it as Mg II 2798 resulting in a `redshift' of about 0.8 for the quasars in the (b) list. As a matter of fact, one need not stop at 3.13. In the redshift hypothesis, one can argue that the line in question is neither Mg II 2798, nor Lyman alpha 1216, but He II 304 (resonance line for this ion), since quasars have been found which do not show Lyman alpha 1216 (Wright et al., 1979. Shaver et al., 1982), and helium is the next most abundant element after hydrogen. Identification of 5020 Å with HeII 304 leads to a `redshift' of 15.5 ! After this brief diversion into the fantasy world of the redshift hypothesis, we must get back to reality. We may illustrate the difficulties in assigning a quasar to a spectral class by an example. For the quasar 1251+3644, Weedman (1985) reports a single medium strength emission line at 5020 Å. At first sight it would appear to be a good candidate for inclusion in Table I, but the uncertainty in the wavelength is ±75 Å. It goes to the credit of Weedman that he gives a realistic estimate of the uncertainty. Some comments on the data are given below.

0420-388. The wavelengths are from Osmer and Smith (1977) who observed this quasar with a SIT Vidicon Spectrometer on the 1.5 m and 4 m telescopes at CTIO. These authors gives the total equivalent width of line Nos. 2 and 3 to be 132 Å.
0140-306. The wavelengths were estimated from the `redshift' and a low-resolution spectrum given by Smith et al. (1981).
0244-3017 ( = Q1097.1). This quasar was observed by Wolstencroft et al. (1983) at low resolution (10.3 Å). The wavelength of the principal emission line was estimated from the spectrum given in Wolstencroft et al. (1983). These authors also give the wavelengths of 15 absorption lines.
0537-286. Spectroscopic observations of this quasar were made by Wright et al. (1978, 1979) at the Anglo-Australian Telescope at low resolution (approximately 10 Å). The values below the wavelengths (first set) in Table I are line-to-continuum ratio and deltalambda1/2. Many absorption features were noted in its spectrum and Wright et al. (1978) give wavelengths of 22 of these. The second set of data for this quasar in Table I is from Wilkes (1986). In the second line, below each wavelength, the first figure represents Wlambda (in Å) and the second, FWHM (in Å).
1244+1129. This quasar has been observed by Foltz et al. (1987). The wavelength of the principal emission line (Table I) has been estimated from the `redshift' given by these authors. Absorption lines are visible on the spectrum given by Foltz et al. (1987).
1320-106. Observed by Kunth et al. (1981). There is only one strong line in the spectrum whose wavelength in Table I has been estimated from the `redshift'.
2228.2-4033. This quasar has been observed by Osmer (1979, 1980) and by Vaucher et al. (1982) but neither gives wavelength(s) of the emission line(s). The two wavelengths listed in Table I have been estimated from the `redshifts'. Osmer (1979, 1980) notes the presence of absorption lines in the spectrum.

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