5 The spectral atlas

The calibrated spectra of the nuclei of all survey galaxies are presented in Fig. 4. The objects are ordered with increasing right ascension at the epoch 2000 ( $\alpha _{2000}$), as in Table 1. The spectra have all been normalized to the flux in a 50 Å wavelength interval centered on 5500 Å. The ordinate displays normalized flux, $F(\lambda)/F(5500)$, and the abscissa wavelength (Å) in the restframe of the galaxy, binned linearly to 2 Å. All spectra were plotted on a common wavelength scale of 3580-7600 Å.

The spectra are generally of high quality. The signal-to-noise ratios (SNRs) of the spectra, measured at 5500 Å over a region between 5475 and 5525 Å, are high. The SNRs of 89 sample galaxies are larger than 20, the average over the sample galaxies being $\sim$51. Columns 10-11 of Table 3 list the flux and signal-to-noise ratios in a 50 Å wavelength interval centered on 5500 Å.

Because the original BCGs sample of Haro (1956), Markarian et al. (1989), and Zwicky (1971) were identified on the basis of their high surface brightness on photographic plates and strong UV emission, they do not all have spectra similar to those of H  II regions. We find that some BCGs have broad H$\alpha$ spectral lines, such as Mrk 6, Mrk 335, and other objects. In fact, based on Véron-Cetty & Véron (2001), 10 sample galaxies are found to be Seyfert galaxies. 13 of 97 BCGs have no emission lines. The other 74 spectra are typical H  II region spectra, with strong narrow nebular emission lines.

The atlas and tables of measurements will be made available electronically.