Скачать или смотреть Teach Astronomy - Spectra of Quasars

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The spectra of quasars give important clues to their properties. The most notable feature of course is the huge redshift of the spectral lines, Doppler shifts of up to six hundred or seven hundred percent indicating extreme distances and large look back times in the universe. Strong lines are seen from the elements hydrogen, magnesium, carbon, nitrogen, and silicon along with others including even iron. This is indication that heavy elements were produced in the quasars, and since the same abundance of heavy elements is seen at redshifts of five or six it means that the heavy elements were produced in the first billion years or so after the big bang. The width of the lines is also important physical information. Most quasars have broad lines with velocity widths of up to ten thousand kilometers per second indicating extremely rapid gas motions in the central parsec of the source. Many AGN also have narrow lines. The narrow emission lines come from a larger region, perhaps a kiloparsec in size, and the velocity widths there are only a few hundred kilometers per second.