Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2011-10-24
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
13 figures and 1 table; MNRAS in press
Scientific paper
We present a detailed investigation of the near-to-far infrared (IR) spectral energy distribution (SED) of a large sample of Spitzer-observed active galactic nuclei (AGN). We fitted the spectra of 51 narrow line Seyfert 1 galaxies (NLS1s) and 64 broad line Seyfert 1 galaxies (BLS1s) using a three component model: a clumpy torus, a dusty narrow line region (NLR) and hot pure-graphite dust located in the outer part of the broad line region (BLR). The fitting is performed on star formation (SF) subtracted SEDs using SF templates that take into account the entire range of possible host galaxy properties. We find that the mid-IR intrinsic emission of NLS1s and BLS1s are very similar, regardless of the AGN luminosity, with long wavelength downturn at around 20-25 um. We present a detailed model of the hot dust component that takes into account the distribution of dust temperature within the clouds and their emission line spectrum. The hot dust continuum provides a very good fit to the observed near-IR continuum spectrum. Most line emission in this component is dramatically suppressed, except MgII(2798A) and HeI lines that are still contributing significantly to the total BLR spectrum. We calculate the covering factors of all the AGN components and show that the covering factor of the hot-dust clouds is about 0.15-0.35, similar to the covering factor of the torus, and is anti-correlated with the source luminosity and the normalized accretion rate.
Mor Rivay
Netzer Hagai
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