Classification parameters for the emission-line spectra of extragalactic objects
J. A. BaldwinObservatorio Interamericano de Cerro Tololo, La Serena, ChileM. M. PhillipsObservatorio Interamericano de Cerro Tololo, La Serena, ChileR. TerlevichCambridge University, Cambridge, England
1981en
ABI
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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Cited by 20 references