The mineralogy of newly formed dust in active galactic nuclei

Authors

Sundar Srinivasan, Academia Sinica, Institute of Astronomy and Astrophysics
F. Kemper, Academia Sinica, Institute of Astronomy and Astrophysics
Yeyan Zhou, Shanghai Astronomical Observatory Chinese Academy of Sciences
Lei Hao, Shanghai Astronomical Observatory Chinese Academy of Sciences
Sarah C. Gallagher, Western University
Jinyi Shangguan, Peking University
Luis C. Ho, Peking University
Yanxia Xie, Peking University
Peter Scicluna, Academia Sinica, Institute of Astronomy and Astrophysics
Sebastien Foucaud, Academia Sinica, Institute of Astronomy and Astrophysics
Rita H.T. Peng, Academia Sinica, Institute of Astronomy and Astrophysics

Document Type

Article

Publication Date

12-1-2017

Journal

Planetary and Space Science

Volume

149

First Page

56

Last Page

63

URL with Digital Object Identifier

10.1016/j.pss.2017.08.012

Abstract

The tori around active galactic nuclei (AGN) are potential formation sites for large amounts of dust, and they may help resolve the so-called dust budget crisis at high redshift. We investigate the dust composition in 53 of the 87 Palomar Green (PG) quasars showing the 9.7 μm silicate feature in emission. By simultaneously fitting the mid-infrared spectroscopic features and the underlying continuum, we estimate the mass fraction in various amorphous and crystalline dust species. We find that the dust consists predominantly of alumina and amorphous silicates, with a small fraction in crystalline form. The mean crystallinity is 8±6%, with more than half of the crystallinities greater than 5%, well above the upper limit determined for the Galaxy. Higher values of crystallinity are found for higher oxide fractions and for more luminous sources.