Spectroscopic evidence for activity in the nuclei of normal spiral galaxies

Abstract

view Abstract Citations (324) References (75) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopic evidence for activity in the nuclei of normal spiral galaxies. Keel, W. C. Abstract The emission spectra of 29 spiral galaxies with low-ionization emission have been studied in detail, using synthetic galaxy spectra to correct the observed spectra for the contribution of starlight. The resulting emission-line intensities and ratios have been compared to published models of shock-heated and power-law photoionized plasmas. The observed spectra are best described by models in which a weak flat-spectrum (power-law) radiation field photoionizes the gas; this nonthermal continuum is generally too weak to be seen directly in the optical. Broad H-alpha emission, extending over a total velocity range as great as 4000 km/s, is identified in several 'normal' nuclei with strong low-ionization emission. The inferred nonthermal continuum and observed broad permitted lines indicate the presence of low-luminosity active nuclei in most, if not all, spiral galaxies. Publication: The Astrophysical Journal Pub Date: June 1983 DOI: 10.1086/161057 Bibcode: 1983ApJ...269..466K Keywords: Emission Spectra; Galactic Nuclei; H Alpha Line; Interstellar Gas; Photoionization; Spiral Galaxies; Abundance; Astronomical Models; Continuous Spectra; Data Simulation; Nonthermal Radiation; Shock Heating; Spectral Line Width; Spectrophotometry; Astrophysics full text sources ADS | data products SIMBAD (51) NED (34)