A Multi-Wavelength Investigation of Seyfert 1.8 and 1.9 Galaxies

• Main Author: Trippe, Margaret
• Format: Others
• Published: Digital Archive @ GSU 2009
• Subjects: Seyfert galaxies; optical spectroscopy; X-ray spectroscopy; active galactic nuclei; astronomy; active galaxies; Astrophysics and Astronomy; Physics
• Online Access: http://digitalarchive.gsu.edu/phy_astr_diss/35; http://digitalarchive.gsu.edu/cgi/viewcontent.cgi?article=1034&context=phy_astr_diss

We focus on determining the underlying physical cause of a Seyfert galaxy's appearance as type a 1.8 or 1.9. Are these "intermediate" Seyfert types typical Seyfert 1 nuclei reddened by central dusty tori or by nuclear dust lanes/spirals in the narrow-line region? Or, are they similar to NGC 2992, objects that have intrinsically weak continua and weak broad emission lines? Our study compares measurements of the reddenings of the narrow and broad-line regions with each other and with the X-ray column derived from XMM Newton 0.5-10 keV spectra to determine the presence and location of dust in the line of sight for a sample of 35 Seyfert 1.8s and 1.9s. From this, we find that Seyfert 1.9s are an almost equal mix of low-flux objects with unreddened broad line regions, and objects with broad line regions reddened by an internal dust source, either the torus or dust structures on the same size scale as the narrow line region. The 1.9s that recieved this designation due to a low continuum flux state showed variable type classifications. All three of the Seyfert 1.8s in our study are probably in low continuum states. Many objects have been misclassified as Seyfert 1.8/1.9s in the past, probably due to improper [N II]/H-alpha deconvolution leading to a false detection of weak broad H-alpha.