The Detection of Silicate Emission from Quasars at 10 and 18 Microns

By L. Hao, H. Spoon, G. Sloan, J. Marshall, Lee Armus, A. Tielens, B. Sargent, I. V. Bemmel, Vassilis Charmandaris, D. Weedman and 1 more. 2005

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We report the spectroscopic detection of silicate emission at 10 and 18 μm in five PG quasars, the first detection of these two features in galaxies outside the Local Group. This finding is consistent with the unification model for active galactic nuclei (AGNs), which predicts that an AGN torus seen pole-on should show a silicate emission feature in the mid-infrared. The strengths of the detected silicate emission features range from 0.12 to 1.25 times the continuum at 10 μm and from 0.20 to 0.79 times the continuum at 18 μm. The silicate grain temperatures inferred from the ratio of 18 μm to 10 μm silicate features under the assumption of optically thin emission range from 140 to 220 K.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8fc9d64b49a000188a8c89efe7db6137133c7a75

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Citations in the corpus

Dust covering factor, silicate emission, and star formation in luminous QSOs (2007, background): “…detection of PAHs in local PG QSOs (Schweitzer et al., 2006), the first detection of the Silicate feature in emission (Siebenmorgen et al., 2005; Hao et al., 2005), as well as detailed studies of the silicate strength in variouscla ses of sources (Spoon et al., 2007; Hao et al., 2007; Shi et…”
THE NEXT GENERATION ATLAS OF QUASAR SPECTRAL ENERGY DISTRIBUTIONS FROM RADIO TO X-RAYS (2011, methodology): “These features have been investigated in detail in previous studies (e.g., Hao et al. 2005; Weedman et al. 2005; Dale et al. 2009; Goulding & Alexander 2009; Diamond-Stanic et al. 2009; Pereira-Santaella et al. 2010; Tommasin et al. 2010), and have been kept in our analyses.”
Spitzer Observations of 3C Quasars and Radio Galaxies: Mid-Infrared Properties of Powerful Radio Sources (2006, background): “A rest wavelength of 15 m was chosen because it lies between the broad silicate features around 9.7 and 18 m (see, e.g., Siebenmorgen et al. 2005; Hao et al. 2005) and avoids the [Ne v] 14.3 m and [Ne iii] 15.5 m lines.”
Three-dimensional radiative transfer modeling of AGN dusty tori as a clumpy two-phase medium (2011, background): “Recent mid-infrared observations obtained with theSpitzer satellite confirm the silicate emission feature in AGNs (Siebenmorgen et al. 2005; Hao et al. 2005).”
Observations of Ultraluminous Infrared Galaxies with the Infrared Spectrograph on the Spitzer Space Telescope. II. The IRAS Bright Galaxy Sample (2006, methodology): “In both cases the fine structure line ratio is plotted against the 6.2µm PAH equivalent width (EQW) in microns, and a sample of AGN and starburst galaxies observed with the IRS are shown for comparison (Devost et al. 20006, Brandl et al. 2005, Weedman et al. 2005, Hao et al. 2005).”
Cool outflows in galaxies and their implications (2020, background): “Two broad silicate features from warm (∼ 200 K) dust have been detected in emission at 10 μm and 18 μm in several type 1 and 2 quasars and AGN, including a low-luminosity LINER (e.g., Siebenmorgen et al. 2005; Hao et al. 2005; Sturm et al. 2005, 2006; Teplitz et al. 2006; Schweitzer et al. 2008).”
Radiative transfer modeling of three-dimensional clumpy AGN tori and its application to NGC 1068 (2006, methodology): “They show that a torus consisting of clouds is capable of suppressing the strength of silicate emission and absorption, as has been observed (e.g., Jaffe et al. 2004; Siebenmorgen et al. 2005; Hao et al. 2005; Sturm et al. 2005).”
Mid-Infrared Spectra of Classical AGNs Observed with the Spitzer Space Telescope (2005, background): “…of Weingartner and Draine (2001) and Li and Draine (2001) predict silicate emission should first appear, and which is consistent with the observed beginning of the silicate emission profile in the two type 1 AGN with the strongest silicate emission (PG 1351 and I Zwicky 1 in Hao et al. (2005)).”
Spitzer Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies (2006, background): “Recently, strong silicate emission features were detected by Spitzer in several radio- loud (3C) and radio quiet (PG) quasars (Siebenmorgen et al. 2005; Hao et al. 2005).”
A Near-Infrared Spectral Template for Quasars (2005, background): “The detection of silicate emission at 10 and 18 m in Spitzer spectra of PG quasars also suggests dust, although at lower temperatures, ranging from 140 to 220 K (Hao et al. 2005).”
A TWO-PARAMETER MODEL FOR THE INFRARED/SUBMILLIMETER/RADIO SPECTRAL ENERGY DISTRIBUTIONS OF GALAXIES AND ACTIVE GALACTIC NUCLEI (2014, background): “Several features are evident in this median quasar spectrum of Shi et al. (2013), including the broad silicate emission features near 10 and 18 µm and the [O IV] 25.9 µm fine structure line that are seen in many AGN (Hao et al. 2005; Armus et al. 2007).”
The Mid-Infrared Spectrum of Star-forming Galaxies: Global Properties of Polycyclic Aromatic Hydrocarbon Emission (2006, background): “…factor regulating the PAH spectrum, since more luminous AGN either destroy all PAH grains (e.g. Voit 1992; Lutz et al. 1998), or produce mid-infrared continuum photons in such copious quantities that the PAH bands are diluted away (Siebenmorgen et al. 2005; Hao et al. 2005; Sturm et al. 2005).”
Star Formation in the Hosts of High-z QSOs: Evidence from Spitzer PAH Detections (2008, background): “The main spectral features are the ones also seen in the spectra of local PG QSOs (e.g. Siebenmorgen et al. 2005; Hao et al. 2005; Schweitzer et al. 2006; Hao et al. 2007; Netzer et al. 2007): A strong AGN continuum with superposed silicate emission at λ & 9µm, and aromatic ‘PAH’ emission features…”
The Distribution of Silicate Strength in Spitzer Spectra of AGNs and ULIRGs (2006, methodology): “The unambiguous detection of silicate emissions in quasars withSpitzer is a strong support for the unification model (Siebenmorgen et al. 2005; Hao et al. 2005), but there is a large variety of silicate features in AGNs.”
Three-dimensional radiative transfer models of clumpy tori in Seyfert galaxies (2008, methodology): “Meanwhile, silicate features in emission were found with the help of the Infrared Spectrograph (IRS) onboard the Spitzer space telescope (e. g. Siebenmorgen et al. 2005; Hao et al. 2005; Sturm et al. 2005; Weedman et al. 2005).”
Spitzer Quasar and ULIRG Evolution Study (QUEST). I. The Origin of the Far-Infrared Continuum of QSOs (2006, background): “The shortest wavelength continuum point at 6 m is shortward of the main PAH complex; the 15 m point is between the two silicate emission peaks at about 10 and 18 m (Siebenmorgen et al. 2005; Hao et al. 2005; Sturm et al. 2005), but still partly affected by silicate emission if present.”