Pa-beta measurements and reddening in Seyfert 1. 8 and 1. 9 galaxies

Journal Article · Tue May 01 04:00:00 EDT 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168743· OSTI ID:6643418

Goodrich, R W ^[1]

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1. McDonald Observatory, Austin, TX (USA)

The class of AGN known as Seyfert 1.8 and Seyfert 1.9 galaxies exhibit weak broad-Balmer emission lines and large Balmer decrements. One theory proposed to explain these characteristics is that the broad-line regions (BLRs) are reddened by dust along the line-of-sight. An alternative theory points out that BLR clouds with low optical depths and low ionization parameters can reproduce the observed line ratios. These two theories predict very different fluxes of the IR hydrogen lines. In order to test the theories this paper presents measurements of the Pa-beta emission lines of 10 intermediate Seyferts. Three objects known to have exhibited extreme spectral variability, NGC 2622, NGC 7603, and Mrk 1018, now all in Seyfert 1 states, are consistent with the reddening theory, as is IRAS 1958-183. Two other objects, Mrk 609 (a Seyfert 1.5) and UGC 7064, are more consistent with the optical-depth/ionization-parameter theory. Hence the Seyfert 1.8/1.9 class is evidently a heterogeneous one. 23 refs.

• OSTI ID: 6643418
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 355; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABSORPTION
BALMER LINES
COSMIC DUST
COSMIC GASES
COSMIC RADIO SOURCES
DUSTS
EMISSION SPECTRA
FLUIDS
GALAXIES
GALAXY NUCLEI
GASES
INFRARED SPECTRA
INTERSTELLAR SPACE
MARKARIAN GALAXIES
MATHEMATICAL MODELS
PASCHEN LINES
SEYFERT GALAXIES
SPACE
SPECTRA
VARIATIONS