Classification parameters for the emission-line spectra of extragalactic objects
1981/02/01 by J. A. Baldwin, M. M. Phillips, R. Terlevich · 107 citations
Chemistry · Engineering · #Spectroscopy and Laser Applications #Laser-induced spectroscopy and plasma #Advanced Measurement and Detection Methods
paper · pdf · doi:10.1086/130766
Abstract
An investigation is made of the merits of various emission-line intensity ratios for classifying the spectra of extragalactic objects. It is shown empirically that several combinations of easily-measured lines can be used to separate objects into one of four categories according to the principal excitation mechanism: normal H II regions, planetary nebulae, objects photoionized by a power-law continuum, and objects excited by shock-wave heating. A two-dimensional quantitative classification scheme is suggested.
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