Fig. 2.
Normalized spectra. NGC 5139−ROA542 and NGC 5139−ROA3596 are the unpublished spectra from Moehler et al. (1998). For NGC 6656−UVBS2 we show the results of both extraction methods (red marks the extraction within a narrow window, and cyan marks the corrected spectrum, offset by 0.1 along the y-axis). The emission lines for that spectrum are real and due to its planetary nebula.
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