Strong [Fe II] emission from NGC 1275

Richard J. Rudy, Ross D. Cohen, George S. Rossano, Peter Erwin, R. C. Puetter, Matthew A. Greenhouse, Charles E. Woodward

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Infrared spectroscopy of the central region of NGC 1275 has revealed an unusually strong [Fe II] λ12567 feature Although the redshift of this line matches those of the lines of the active nucleus, its much narrower profile signifies its origin in a different volume of gas. The strength of the [Fe II] feature compared to the other emission lines from the central region indicates that iron remains relatively undepleted from the interstellar medium of NGC 1275. While other agents may contribute to the [Fe II] emission, we propose that the bulk of the emission is excited by wide-spread shocks. These shocks enrich the iron content of the interstellar medium excite the extensive low-ionization regions which produce the [Fe II] flux, and contribute to the other low-excitation features which are so distinctive in the spectrum of NGC 1275. These shocks could result from supernova explosions, the accretion on intracluster material, galaxy-galaxy interactions, or some process associated with the active nucleus, but our observations do not distinguish among these phenomena. However, if supernovae generate the shocks, then a very high, and observable, supernovae rate of ∼3 yr-1 is implied by the [Fe II] luminosity. The presence of an [Fe II] feature comparable in brightness to the nuclear Paβ emission, but exhibiting a very different profile, makes NGC 1275 an unambiguous example of a luminous active galaxy where the [Fe II] emission does not originate in the active nucleus, and probably is not powered by the nuclear continuum source While this observation of NGC 1275 does not exclude the active nucleus as the principal source of the strong [Fe II] emission detected in other active galaxies, it does indicate that other agents (e.g., shocks) can compete favorably in the production of the [Fe II] lines.

Original languageEnglish (US)
Pages (from-to)527-534
Number of pages8
JournalAstrophysical Journal
Issue number2
StatePublished - Sep 10 1993
Externally publishedYes


  • Galaxies: ISM
  • Galaxies: Seyfert
  • Galaxies: individual (NGC 1275)
  • Galaxies: nuclei
  • Infrared: galaxies
  • Shock waves

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