科研之友
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摘要
We present Spitzer infrared (IR) spectra and ultraviolet (UV) to mid-IR spectral energy distributions (SEDs) of 25 luminous type 1 quasars at z similar to 2. In general, the spectra show a bump peaking around 3 mu m and the 10 mu m silicate emission feature. The 3 mu m 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 mu m emission. In the first case, a parameter search of similar to 1.25 million CLUMPY models shows that (1) if we ignore the UV-to-near-IR SED, models fit the 2-8 mu m region well, but not the 10 mu m feature; (2) if we include the UV-to-near-IR SED in the fit, models do not fit the 2-8 mu m region. The observed 10 mu m 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 mu m feature is better reproduced by the CLUMPY models. The additional blackbody contribution in the 2-8 mu m range allows CLUMPY models dominated by cooler temperatures (T < 800 K) to better fit the 8-12 mu m 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 similar to 1200 K as expected for graphite grains.
- 出版日期2011-3-10
