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by Thaisa Storchi Bergmann

Feeding Versus Feedback in NGC 4151 NGC 4151 is the nearest bright Seyfert I galaxy to Earth and thus harbors one of the best-studied active galactic nuclei (AGN). At a distance of only about 13.3 Mpc (43.3 million light-years), the scale at the galaxy is 65 parsecs (pc) per arcsecond. Its relative closeness makes NGC 4151 an important laboratory for the detailed study of the feeding and feedback processes of its active nucleus. In optical wavelengths, the emitting gas of the narrowline region (NLR) has been found to have an approximate

Figure 1.

biconical morphology, as observed in a previous Hubble

Top: K-band image of the central 60 × 60 arcseconds of NGC 4151. The continuous line shows the orientation of the major axis of the galaxy, while the dashed line shows the orientation of the bicone. The rectangle shows the region covered by the NIFS observations. Bottom: narrowband [OIII] image of the NLR obtained with the Hubble Space Telescope shown in the field-ofview of our NIFS observations.

Space Telescope (HST) [OIII] λ 5007 narrow-band image, which is shown in the bottom of Figure 1. According to previous studies, our line of sight is outside of, but close to, the edge of the cones oriented along position angle (PA) ~ 60°. Optical spectroscopy reveals outflows along the cones with the approaching side to the southwest. In the radio, it presents a linear structure along PA = 77°, which is not aligned with the bicone. Although NGC 4151 has been the subject of many previous imaging and spectroscopic studies, we used the Near-infrared Integral Field Spectrometer (NIFS) at the Gemini North telescope to obtain an unprecedented “3-D view” of the galaxy’s NLR which allows us to map its excitation and kinematics. The high image quality of NIFS revealed details with a spatial resolution comparable to that of HST, and the spectral resolution provided by NIFS allowed the construction of channel maps along emission-line profiles providing a “kinematic tomography” of the NLR which challenges previous kinematic models of the source.



Issue 38 - June 2009  
Issue 38 - June 2009