We fitted Spitzer/IRS ∼ 2 − 35µm spectra of 26 luminous QSOs in attempt to define the main emission components. Our model has three major components: a clumpy torus, dusty narrow line region (NLR) clouds and a blackbody-like dust. The models utilize the clumpy torus of and are the first to allow its consistent check in type-I AGNs. Single torus models and combined torus-NLR models fail to fit the spectra of most sources but three component models adequately fit the spectra of all sources. We present torus inclination, cloud distribution, covering factor and torus mass for all sources and compare them with bolometric luminosity, black hole mass and accretion rate. The torus covering factor and mass are found to be correlated with the bolometric luminosity of the sources. We find that a substantial amount of the ∼ 2 − 7µm radiation originates from a hot dust component, which likely situated in the innermost part of the torus. The luminosity radiated by this component and its covering factor are comparable to those of the torus. We quantify the emission by the NLR clouds and estimate their distance from the center. The distances are ∼ 700 times larger than the dust sublimation radius and the NLR covering factor is about 0.07. The total covering factor by all components is in good agreement with the known AGN type-I:type-II ratio.

We present a detailed investigation of the near‐infrared to far‐infrared (near‐IR to far‐IR) spectral energy distribution (SED) of a large sample of Spitzer‐observed active galactic nuclei (AGNs). 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 and hot pure‐graphite dust located in the outer part of the broad‐line region (BLR). The fitting was 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 is very similar, regardless of the AGN luminosity, with long‐wavelength downturn at around 20–25 μm. 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 Mg ii λ2798 and He i lines that are still contributing significantly to the total BLR spectrum. We calculate the covering factors (CFs) of all the AGN components and show that the CF of the hot‐dust clouds is about 0.15–0.35, similar to the CF of the torus, and is anticorrelated with the source luminosity and the normalized accretion rate.

We fitted the optical to mid-infrared (MIR) spectral energy distributions (SEDs) of ∼15000 type-I, 0.75 < z < 2, active galactic nuclei (AGNs) in an attempt to constrain the properties of the physical component responsible for the rest-frame near-infrared (NIR) emission. We combine optical spectra from the Sloan Digital Sky Survey (SDSS) and MIR photometry from the preliminary data release of the Wide Infrared Survey Explorer (WISE). The sample spans a large range of AGN properties: luminosity, black hole mass, and accretion rate. Our model has two components: a UV-optical continuum source and very hot, pure-graphite dust clouds. We present the luminosity of the hot-dust component and its covering factor, for all sources, and compare it with the intrinsic AGN properties. We find that the hot-dust component is essential to explain the (rest) NIR emission in almost all AGNs in our sample, and that it is consistent with clouds containing pure-graphite grains and located between the dust-free broad line region (BLR) and the "standard" torus. The covering factor of this component has a relatively narrow distribution around a peak value of ∼0.13, and it correlates with the AGN bolometric luminosity. We suggest that there is no significant correlation with either black hole mass or normalized accretion rate. The fraction of hot-dust-poor AGNs in our sample is ∼ 15 − 20%, consistent with previous studies. We do not find a dependence of this fraction on redshift or source luminosity.

We report Herschel/SPIRE Spitzer and WISE observations of 44 z ≃ 4.8 optically selected active galactic nuclei (AGNs). This flux limited sample contains the highest mass black holes (BHs) at this redshift. Ten of the objects were detected by Herschel and five show emission that is not clearly associated with the AGNs. The star formation (SF) luminosity (L SF ) obtained by fitting the spectral energy distribution (SED) with standard SF templates, taking into account AGN contribution, is in the range 10 46.62 − 10 47.21 erg s −1 corresponding to SF rates of 1090 − 4240M ⊙ yr −1 . Fitting with very luminous submillimeter galaxy SEDs gives SF rates that are smaller by 0.05 dex when using all bands and 0.1 dex when ignoring the 250µm band. A 40K gray-body fits to only the 500µm fluxes reduce L SF by about a factor two. Stacking analysis of 29 undetected sources give significant signals in all three bands. A SF template fit indicates L SF =10 46.19−46.23 erg s −1 depending on the assume AGN contribution. A 40K fit to the stacked 500µm flux gives L SF =10 45.95 erg s −1 . The mean BH mass (M BH ) and AGN luminosity (L AGN ) of the detected sources are significantly higher than those of the undetected ones. The spectral differences are seen all the way from UV to far infrared wavelengths. The mean optical-UV spectra are similar to the ones predicted for thin accretion disks around BHs with the measured masses and accretion rates. We suggest two alternative explanations to the correlation of L SF , L AGN and M BH , one involving no AGN feedback and the second a moderate feedback that affects, but not totally quench SF in 3/4 of the sources. We compare our L SF and L AGN to lower redshift samples and show a new correlation between L SF and M BH . We also examine several rather speculative ideas about the host galaxy properties including the -2possibility that the detected sources are above the SF mass sequence (MS) at z ≃ 4.8, perhaps in mergers, and most of the undetected sources are on the MS.

We report new Herschel a observations of 25 z ≃ 4.8 extremely luminous optically selected active galactic nuclei (AGNs). Five of the sources have extremely large star forming (SF) luminosities, L SF , corresponding to SF rates (SFRs) of 2800-5600 M ⊙ yr −1 assuming a Salpeter IMF. The remaining sources have only upper limits on their SFRs but stacking their Herschel images results in a mean SFR of 700 ± 150 M ⊙ yr −1 . The higher SFRs in our sample are comparable to the highest observed values so far, at any redshift. Our sample does not contain obscured AGNs, which enables us to investigate several evolutionary scenarios connecting super-massive black holes and SF activity in the early universe. The most probable scenario is that we are witnessing the peak of SF activity in some sources and the beginning of the post-starburst decline in others. We suggest that all 25 sources, which are at their peak AGN activity, are in large mergers. AGN feedback may be responsible for diminishing the SF activity in 20 of them but is not operating efficiently in 5 others.