Type of Document Dissertation Author Das, Varendra Author's Email Address das@chara.gsu.edu,varendradas@hotmail.com URN etd-07272006-133559 Title Kinematics of the Narrow-Line Regions in the Seyfert Galaxies NGC 4151 and NGC 1068 Degree Ph.D. Department Physics and Astronomy Advisory Committee
Advisor Name Title Dr. D. Michael Crenshaw Committee Chair Dr. Douglas R. Gies Committee Member Dr. H. Richard Miller Committee Member Dr. Nikolaus Dietz Committee Member Dr. Paul J. Wiita Committee Member Dr. Steven B. Kraemer Committee Member Keywords
- Active Galactic Nuclei
- NGC 1068
- NGC 4151
- Seyfert Galaxies
- Narrow-Line Region
- Kinematics
- Dynamics
- Bicones
- Unified Models
Date of Defense 2006-07-12 Availability unrestricted Abstract We present a study of high-resolution long-slit spectra of theNarrow-Line Regions (NLRs) of NGC 4151 (a Seyfert 1 galaxy) and NGC
1068 (a Seyfert 2 galaxy) obtained with the Space Telescope Imaging
Spectrograph (STIS) aboard the Hubble Space Telescope (HST). The
spectra were retrieved from the Multimission Archive at Space
Telescope (MAST) and were obtained from five and seven orbits of HST
time resulting in five and seven parallel slit configurations at
position angles of 52 degrees and 38 degrees for NGC 4151 and NGC 1068
respectively. The spectra have a spatial resolution of 0.2 arcsecond
across and 0.1 arcsecond along each slit. Observations of [O III]
emission from the NLRs were made using the medium resolution G430M
grating aboard HST. The spectral resolving power of the grating, R~
9000, resulted in the detection of multiple kinematic components of
the [O III] emission line gas along each slit. Radial velocities of
the components were measured using a Gaussian fitting procedure.
Biconical outflow models were generated to match the data and for
comparison to previous models done with lower dispersion observations.
The general trend is an increase in radial velocity roughly
proportional to distance from the nucleus, followed by a linear
decrease after roughly 100 pc. This is similar to that seen in other
Seyfert galaxies, indicating common acceleration and deceleration
mechanisms. The full-width at half-maximum (FWHM) of the emission
lines reaches a maximum of 1000 km/s near the nucleus, and generally
decreases with increasing distance to about 100 km/s in the extended
narrow-line region (ENLR), starting at about 400 pc from the
nucleus. In addition to the bright emission knots, which generally fit
our model, there are faint high velocity clouds that do not fit the
biconical outflow pattern of our kinematic model.
A comparison of our observations with high-resolution radio maps shows
that the kinematics of the faint NLR clouds may be affected by the
radio lobes that comprise the inner jet. However, the bright NLR
clouds show a smooth transition across the radio knots in radial
velocity and velocity dispersion plots and remain essentially
undisturbed in their vicinity, indicating that the radio jet is not
the principal driving force on the outflowing NLR clouds.
A dynamical model was developed for NGC 1068; it includes forces of
radiation pressure, gravity, and drag due an ambient medium,
simultaneously acting on the NLR clouds. The velocity profile from
this model was too steep to fit the data, which show a more slowly
increasing velocity profile. Gravity alone was not able to slow down
the clouds but with the drag forces included, the clouds could slow
down, reaching systemic velocities at distances that depend on the
column densities of the NLR gas and density of the intercloud
medium. A biconical model using the geometric parameters from our
kinematic fit, and the velocity law from the dynamic fit, was used to
match the data. The resulting dynamic model represented a poor fit to
the data, indicating the need for additional dynamical considerations.
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