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Free–Free Absorption and the Unified Scheme

Published online by Cambridge University Press:  05 March 2013

Seiji Kameno ,
Makoto Inoue ,
Kiyoaki Wajima ,
Satoko Sawada-Satoh  and
Zhi-Qiang Shen
Seiji Kameno
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka Tokyo, Japan, 181-8588. kameno@hotaka.mtk.nao.ac.jp
Makoto Inoue
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka Tokyo, Japan, 181-8588. kameno@hotaka.mtk.nao.ac.jp
Kiyoaki Wajima
Affiliation:
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka Tokyo, Japan, 181-8588. kameno@hotaka.mtk.nao.ac.jp
Satoko Sawada-Satoh
Affiliation:
The Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara Kanagawa, Japan, 229-8510.
Zhi-Qiang Shen
Affiliation:
The Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Sagamihara Kanagawa, Japan, 229-8510.
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Abstract

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We report very long baseline array (VLBA) observations at 2.3, 8.4, and 15.4 GHz towards nine gigahertz peaked spectrum (GPS) sources. One Seyfert 1 galaxy, one Seyfert 2 galaxy, three radio galaxies, and four quasars were included in our survey. We obtained spatial distributions of the free–free absorption (FFA) opacity with milliarcsecond resolution for all sources. It is found that type 1 (Seyfert 1 and quasars) and type 2 (Seyfert 2 and radio galaxies) sources showed different distributions of the FFA opacities. The type 1 sources tend to show more asymmetric opacity distributions towards a double lobe, while those of the type 2 sources are rather symmetric. Our results imply that the different viewing angle of the jet causes the difference of FFA opacity along the external absorber. This idea supports the unified scheme between quasars and radio galaxies, proposed by Barthel (1989).

Keywords

galaxies: activegalaxies: nucleigalaxies: jetsradio continuum: galaxiestechniques: high angular resolution
Type
GPS/CSS Workshop
Information
Publications of the Astronomical Society of Australia , Volume 20 , Issue 1 , 2003 , pp. 213 - 221
Copyright
Copyright © Astronomical Society of Australia 2003

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