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NGC 4151
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Title: The Dusty Nuclear Torus in NGC 4151: Constraints from Gemini Near-Infrared Integral Field Spectrograph Observations
Authors: Rogemar A. Riffel, Thaisa Storchi-Bergmann, Peter J. Mcgregor
(Version v2)

We have used a near-infrared nuclear spectrum (covering the Z, J, H and K bands) of the nucleus of NGC 4151 obtained with the Gemini Near-infrared Integral Field Spectrograph (NIFS) and adaptive optics, to isolate and constrain the properties of a near-IR unresolved nuclear source whose spectral signature is clearly present in our data. The near-IR spectrum was combined with an optical spectrum obtained with the Space Telescope Imaging Spectrograph which was used to constrain the contribution of a power-law component. After subtraction of the power-law component, the near-IR continuum is well fitted by a blackbody function, with T=1285 ±50 K, which dominates the nuclear spectrum -- within an aperture of radius 0\farcs3 -- in the near-IR. We attribute the blackbody component to emission by a dusty structure, with hot dust mass M_HD =(6.9 ±1.5) x10^{-4} solar masses, not resolved by our observations, which provide only an upper limit for its distance from the nucleus of 4 pc. If the reddening derived for the narrow-line region also applies to the near-IR source, we obtain a temperature T=1360 ±50 K and a mass M_HD=(3.1 ±0.7) x10^{-4} solar masses for the hot dust. This structure may be the inner wall of the dusty torus postulated by the Unified Model or the inner part of a dusty wind originating in the accretion disk.

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Title: The Black Hole Mass of NGC 4151: Comparison of Reverberation Mapping and Stellar Dynamical Measurements
Authors: Christopher A. Onken, Monica Valluri, Bradley M. Peterson, Richard W. Pogge, Misty C. Bentz, Laura Ferrarese, Marianne Vestergaard, D. Michael Crenshaw, Sergey G. Sergeev, Ian M. McHardy, David Merritt, Gary A. Bower, Timothy M. Heckman, Amri Wandel

We present a stellar dynamical estimate of the black hole (BH) mass in the Seyfert 1 galaxy, NGC 4151. We analyse ground-based spectroscopy as well as imaging data from the ground and space, and we construct 3-integral axisymmetric models in order to constrain the BH mass and mass-to-light ratio. The dynamical models depend on the assumed inclination of the kinematic symmetry axis of the stellar bulge. In the case where the bulge is assumed to be viewed edge-on, the kinematical data give only an upper limit to the mass of the BH of ~4e7 M_sun (1 sigma). If the bulge kinematic axis is assumed to have the same inclination as the symmetry axis of the large-scale galaxy disk (i.e., 23 degrees relative to the line of sight), a best-fit dynamical mass between 4-5e7 M_sun is obtained. However, because of the poor quality of the fit when the bulge is assumed to be inclined (as determined by the noisiness of the chiČ surface and its minimum value), and because we lack spectroscopic data that clearly resolves the BH sphere of influence, we consider our measurements to be tentative estimates of the dynamical BH mass. With this preliminary result, NGC 4151 is now among the small sample of galaxies in which the BH mass has been constrained from two independent techniques, and the mass values we find for both bulge inclinations are in reasonable agreement with the recent estimate from reverberation mapping (4.57[+0.57/-0.47]e7 M_sun) published by Bentz et al.

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