Introduction to active galaxies
Introduction to active galaxies

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Introduction to active galaxies

2.3 Broadband spectra

The broadband spectrum is the spectrum over all the observed wavelength ranges. To plot the broadband spectrum of any object it is necessary to choose logarithmic axes.

  • Why is it necessary to use logarithmic axes?

  • Because both the spectral flux density, Fλ, and the wavelength vary by many powers of 10.

Figure 7 shows the broadband spectrum of the Sun: it has a strong peak at optical wavelengths with very small contributions at X-ray and radio wavelengths.

Figure 7
(Adapted from Nicolson, 1982)
Figure 7: The broadband spectrum of the Sun. The dashed lines indicate the maximum and minimum in regions where the flux density varies
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