The Dusty Nuclear Torus in NGC 4151: Constraints from Gemini Near-Infrared Integral Field Spectrograph Observations
Abstract
We have used a near-infrared (near-IR) 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 0farcs3—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) × 10-4 M sun, 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) × 10-4 M sun 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2009
- DOI:
- 10.1088/0004-637X/698/2/1767
- arXiv:
- arXiv:0903.2798
- Bibcode:
- 2009ApJ...698.1767R
- Keywords:
-
- galaxies: active;
- galaxies: individual: NGC 4151;
- galaxies: ISM;
- galaxies: nuclei;
- Astrophysics - Cosmology and Extragalactic Astrophysics
- E-Print:
- 5 pages, 1 figure