We present Spitzer infrared (IR) spectra and ultraviolet (UV) to mid-IR spectral energy distributions (SEDs) of 25 luminous type 1 quasars at z ~ 2. In general, the spectra show a bump peaking around 3 μm and the 10 μm silicate emission feature. The 3 μm emission is identified with hot dust emission at its sublimation temperature. We explore two approaches to modeling the SED: (1) using the CLUMPY model SED from Nenkova et al. and (2) the CLUMPY model SED and an additional blackbody component to represent the 3 μm emission. In the first case, a parameter search of ~1.25 million CLUMPY models shows that (1) if we ignore the UV-to-near-IR SED, models fit the 2-8 μm region well, but not the 10 μm feature; (2) if we include the UV-to-near-IR SED in the fit, models do not fit the 2-8 μm region. The observed 10 μm features are broader and shallower than those in the best-fit models in the first approach. In the second case, the shape of the 10 μm feature is better reproduced by the CLUMPY models. The additional blackbody contribution in the 2-8 μm range allows CLUMPY models dominated by cooler temperatures (T < 800 K) to better fit the 8-12 μm SED. A centrally concentrated distribution of a small number of torus clouds is required in the first case, while in the second case the clouds are more spread out radially. The temperature of the blackbody component is ~1200 K as expected for graphite grains.
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Support for this work was provided by NASA through awards (RSA's 1353801 and 1365236) issued by JPL/Caltech. G.T.R. was supported in part by an Alfred P. Sloan Research Fellowship. S.C.G. thanks the National Science and Engineering Research Council of Canada for support. The IRS was a collaborative venture between Cornell University and Ball Aerospace Corporation funded by NASA through the Jet Propulsion Laboratory and Ames Research Center.
Deo, Rajesh P.; Richards, Gordon T.; Nikutta, Robert; Elitzur, Moshe; Gallagher, Sarah C.; Ivezić, Željko; and Hines, Dean, "Dusty Tori of Luminous Type 1 Quasars at z ~ 2" (2011). Physics and Astronomy Faculty Publications. 193.