The Distribution of Silicate Strength in Spitzer Spectra of AGNs and ULIRGs

By L. Hao, D. Weedman, H. Spoon, J. Marshall, N. Levenson, M. Elitzur, J. Houck. 2006

151 citations recorded by the source corpus.

A sample of 196 AGNs and ULIRGs observed by the Infrared Spectrograph (IRS) on Spitzer is analyzed to study the distribution of the strength of the 9.7 μm silicate feature. Average spectra are derived for quasars, Seyfert 1 and Seyfert 2 AGNs, and ULIRGs. We find that quasars are characterized by silicate features in emission and Seyfert 1s equally by emission or weak absorption. Seyfert 2s are dominated by weak silicate absorption, and ULIRGs are characterized by strong silicate absorption (mean apparent optical depth about 1.5). Luminosity distributions show that luminosities at rest frame 5.5 μm are similar for the most luminous quasars and ULIRGs and are almost 105 times more luminous than the least luminous AGN in the sample. The distributions of spectral characteristics and luminosities are compared to those of optically faint infrared sources at z ~ 2 being discovered by the IRS, which are also characterized by strong silicate absorption. It is found that local ULIRGs are a similar population, although they have lower luminosities and somewhat stronger absorption compared to the high-redshift sources.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/8361308d293dec8c4a33108dbdc44530444e2c56

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In Astronomy and Astrophysics

1. H. Netzer
2. D. M. Alexander
3. Sylvain Veilleux
4. D. Rupke
5. P. Hopkins
6. R. Maiolino
7. L. Hernquist
8. D. Lutz

In Instrumentation

1. Sylvain Veilleux
2. D. Rupke
3. H. Netzer
4. R. Maiolino
5. L. Tacconi
6. D. Lutz
7. R. Genzel
8. P. Hopkins

Citations in the corpus

• High-Resolution Mid-Infrared Spectroscopy of Ultraluminous Infrared Galaxies (2007, background): “This is supported by the fact that optical QSOs usually show silicates in emission (Hao et al. 2007), and that one of the two objects on the right-hand side of the lower panel of Figure 22 is IRAS 15206+3342, which, as previously mentioned, contains a BAL QSO.”
• AGN Dusty Tori. I. Handling of Clumpy Media (2008, background): “The 10µm feature In contrast with ultra-luminous infrared galaxies (ULIRGs), AGN observations do not provide any example of deep 10µm silicate absorption feature (Hao et al. 2007).”
• First X-ray-based statistical tests for clumpy-torus models: eclipse events from 230 years of monitoring of Seyfert AGN (2014, background): “However, samples of mid-IR spectra of type I Seyferts can exhibit silicate features spanning a range of emission and absorption (see Hao et al. 2007 for a sample obtained with Spitzer); type IIs generally show only weak absorption but a few can show emission (Sturm et al. 2005; Hao et al. 2007).”
• MID-INFRARED SPECTROSCOPY OF SUBMILLIMETER GALAXIES: EXTENDED STAR FORMATION IN MASSIVE HIGH-REDSHIFT GALAXIES (2009, unknown): “7µm >∼ 1.5; Shi et al. 2006; Hao et al. 2007).”
• Dust covering factor, silicate emission, and star formation in luminous QSOs (2007, background): “…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 al., 2006; Imanishi et al., 2007).”
• AGN Dusty Tori. II. Observational Implications of Clumpiness (2008, background): “Finally, the average spectra of Seyfert 1 and 2 galaxies derived by Hao et al. (2007) from Spitzer observations have nearly identical shapes, except for the 10 m silicate region.”
• SPITZER QUASAR AND ULIRG EVOLUTION STUDY (QUEST). IV. COMPARISON OF 1 Jy ULTRALUMINOUS INFRARED GALAXIES WITH PALOMAR-GREEN QUASARS (2009, methodology): “The broad distribution of silicate strength in ULIRGs is well known from previous studies (e.g., Hao et al. 2007; Spoon et al. 2007).”
• Stellar Evolutionary Effects on the Abundances of Polycyclic Aromatic Hydrocarbons and Supernova-Condensed Dust in Galaxies (2007, background): “…is dominated by the 6Y9 m PAH features, but in some cases, such as with low-metallicity galaxies or deeply embedded sources, the 8 m flux may be dominated by, respectively, the continuum (Madden et al. 2006; Wu et al. 2006) or the 9.7 m silicate feature (e.g., Spoon et al. 2004; Hao et al. 2007).”
• TORUS AND ACTIVE GALACTIC NUCLEUS PROPERTIES OF NEARBY SEYFERT GALAXIES: RESULTS FROM FITTING INFRARED SPECTRAL ENERGY DISTRIBUTIONS AND SPECTROSCOPY (2011, background): “7 < −1) (see Nenkova et al. 2008b; Elitzur 2008; Sirocky et al. 2008), while observations show that many Seyfert galaxies have relatively deep silicate features (see Shi et al. 2006; Hao et al. 2007; Deo et al. 2009).”
• Resolving the mid-infrared cores of local Seyferts (2009, methodology): “Their 6µm continuum luminosities have been converted to 12.3µm using mediank-corrections from Hao et al. (2007).”
• Star Formation in the Hosts of High-z QSOs: Evidence from Spitzer PAH Detections (2008, background): “…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 at…”