Food for Thought

1. Most of the emission lines readily apparent in most of these spectra is due to hydrogen. What kind(s) of galactic objects produce hydrogen lines in emission?
2. The spectra of which galaxies show emission lines? (Look specifically around the wavelength regions of 6600, 4900, and 4200 Angstroms.)
3. The radiation from what kind(s) of objects is dominating the spectra of these galaxies?
4. We will be using the position of the calcium H and K absorption lines in our calculations of the velocities of these galaxies. What kinds of stars (specifically, what spectral types) have strong H and K lines?
5. The spectra of which galaxies show primarily absorption lines (no strong emission lines), including strong H and K lines? (Look specifically around the wavelength region of 4000 Angstroms.)
6. The radiation from what kind(s) of stars is dominating the spectra of these galaxies?
7. Which type(s) of galaxies do you expect would show only absorption lines?
8. Review your sketches of the galaxies showing primarily absorption lines and your classification of those galaxies. Are you going to include these galaxies in your data? Why or why not?

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