Seyfert Galaxies at the IR: the ISO perspective

Perez Garcia, A. M.; Rodríguez Espinosa, J. M.
Bibliographical reference

"IX Latin American Regional IAU Meeting, "Focal Points in Latin American Astronomy", held in Tonantzintla, Mexico, Nov 9-13, 1998, Eds: Aguilar, A.; Carraminana, A.; to be printed in Revista Mexicana de Astronomia y Astrofisica Serie de Conferencias."

Advertised on:
11
1998
Number of authors
2
IAC number of authors
2
Citations
0
Refereed citations
0
Description
The study of the IR emission from Seyfert galaxies is of key importance for understanding the origin of the extraordinary nuclear activity seen in these objects as well as the differences between the various Seyfert types. Two important problems remain unresolved. For instance, whether the IR radiation from Seyfert galaxies is of mostly thermal or non-thermal origin has been a matter of debate. This work presents data from the Infrared Space Observatory (ISO) of a complete set of Seyfert galaxies in a wavelength range seldom explored so far. These data allow a detailed study of the far IR Spectral Energy Distribution of these sources. A Bayesian inversion method has been used to invert the Spectral Energy Distributions (SED) of these sources yielding two fundamental results, namely that the far IR SED of Seyfert Galaxies can be explained solely through thermal reradiation of high energy photons by dust. And, that this thermal emission is made up of two or three independent components, a warm, a cold, and a very cold dust component. These thermal components have been readily explained as produced by warm dust heated by either the active nucleus or by circumnuclear starbursts, cold dust heated by star forming region in the galaxy disk, and very cold dust heated by the general interstellar radiation field, respectively. Comparisons have been made between the parameters (fluxes, temperatures, luminosities, etc.) obtained from the analysis of the IR SEDs and the emission in other wavelength ranges (radio and X-rays). The host galaxies have proven once more to be key elements in the understanding of the Seyfert phenomenon. Besides, the nuclear properties seem to be adequately explained with the Unified Models of AGN, that state that the differences seen between the broad (Seyfert 1) and narrow (Seyfert 2) lines objects are due to geometrical orientation effects.