Classification of Spectra

Depending on the shape of the spectra and the discuss above, we have made following classes of the spectra which also relates to certain characteristics of the source structure, e.g, extended sources tend to show steep spectrum, compact sources or sources having small diameter tend to show flat spectrum etc.

Based on the shape of the spectra in the $log$ - $log$ plots of the flux density versus frequency, we have classified the sources as having steep (class S) spectra, peaked (class P) spectra, flat (class F) spectra and composite (class C) spectra. Sources that do not fall into the above categories are put under Class U as unclassified spectra.

It must be noted that given the uncertainties in the spectrum, there is an element of subjectiveness in the classification, which must be kept in the mind.