Info

4400 4600 4800 5000 5200 5400 5600 Wavelength (A)

Figure 5.3. Optical spectra of a Seyfert 2 galaxy (top), a narrow-line Seyfert 1 galaxy (middle), and a Seyfert 1 galaxy (bottom). The most-prominent lines in each spectrum are Hp A4861 and [O Ill] AA4959, 5007. From Pogge (2000), with permission from Elsevier.

4400 4600 4800 5000 5200 5400 5600 Wavelength (A)

Figure 5.3. Optical spectra of a Seyfert 2 galaxy (top), a narrow-line Seyfert 1 galaxy (middle), and a Seyfert 1 galaxy (bottom). The most-prominent lines in each spectrum are Hp A4861 and [O Ill] AA4959, 5007. From Pogge (2000), with permission from Elsevier.

In the years following the identification of the first quasars, an increasingly wide variety of AGN activity was identified, as discussed below. By the 1980s, however, it had become clear that the single best indicator of AGN activity is hard X-ray emission, since this is not subject to internal extinction in AGNs,t which often turn out to have fairly large columns of gas and dust along our sight lines to their centers, as we will see shortly.

Was this article helpful?

0 0

Post a comment