The mineralogy of newly formed dust in active galactic nuclei
arXiv:1707.06694 · doi: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 micron 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.
24 pages, 9 figures, accepted for publication in Planetary and Space Science
References in corpus (15)
- Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
- Non-linear Least Squares Fitting in IDL with MPFIT
- Spitzer Quasar and ULIRG Evolution Study (QUEST): II. The Spectral Energy Distributions of Palomar-Green Quasars
- Radiative Transfer Modeling of Three-Dimensional Clumpy AGN Tori and its Application to NGC 1068
- Spitzer Quasar and ULIRG evolution study (QUEST): I. The origin of the far infrared continuum of QSOs
- The distribution of silicate strength in Spitzer spectra of AGNs and ULIRGs
- 9.7 um Silicate Features in AGNs: New Insights into Unification Models
- CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph Sources. II. High-resolution observations
- On the Crystallinity of Silicate Dust in the Interstellar Medium
- Infrared spectra and photometry of complete samples of PG and 2MASS quasars
- A complete census of silicate features in the mid-infrared spectra of active galaxies
- Dust in the wind: Crystalline silicates, corundum and periclase in PG 2112+059
- The underlying driver for the \civ Baldwin effect in QSOs with
- On the Anomalous Silicate Emission Features of AGNs: A Possible Interpretation Based on Porous Dust
- A Tale of Three Galaxies: Anomalous Dust Properties in IRASF10398+1455, IRASF21013-0739 and SDSSJ0808+3948