Spitzer mid-infrared spectra of type II quasars using infrared photometric observations

Authors

  • H. G. Shan,

    1. National Astronomical Observatories/Yunnan Observatory and Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China
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  • P. S. Chen

    Corresponding author
    1. National Astronomical Observatories/Yunnan Observatory and Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China
      E-mail: iraspsc@yahoo.com.cn
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E-mail: iraspsc@yahoo.com.cn

ABSTRACT

Type II quasars are luminous active galactic nuclei with the optical spectra of type II Seyfert galaxies, and their central regions are obscured by large amounts of gas and dust. In this paper, we present Spitzer spectra of eight type II quasars using infrared photometric observations. It is found that almost all the sources in this paper show features of polycyclic aromatic hydrocarbon and silicate in absorption, which indicate strong star formation activities. All the sources show significant highly ionized atomic emission features, such as [Ne v] and/or [S iv], in the mid-infrared, which indicate that their properties are similar to those of type I Seyfert galaxies. Furthermore, our results reveal that, similar to type II Seyfert galaxies, there might be two types of type II quasar: the ‘true’ type II quasars and those that have the properties of Seyfert I galaxies in the infrared. Therefore, the classifications of quasars that are based only on their optical spectra are not perfect if their infrared properties are considered.

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