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Register a new userDynamics of the Narrow-Line Region in the Seyfert 2 Galaxy NGC 1068
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We present dynamical models based on a study of high-resolution long-slit spectra of the narrow-line region (NLR) in NGC 1068 obtained with the Space Telescope Imaging Spectrograph (STIS) aboard The Hubble Space Telescope (HST). The dynamical models consider the radiative force due to the active galactic nucleus (AGN), gravitational forces from the supermassive black hole (SMBH), nuclear stellar cluster, and galactic bulge, and a drag force due to the NLR clouds interacting with a hot ambient medium. The derived velocity profile of the NLR gas is compared to that obtained from our previous kinematic models of the NLR using a simple biconical geometry for the outflowing NLR clouds. The results show that the acceleration profile due to radiative line driving is too steep to fit the data and that gravitational forces along cannot slow the clouds down, but with drag forces included, the clouds can slow down to the systemic velocity over the range 100--400 pc, as observed. However, we are not able to match the gradual acceleration of the NLR clouds from ~0 to ~100 pc, indicating the need for additional dynamical studies.
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We present a study of high-resolution long-slit spectra of the narrow-line region (NLR) in NGC 1068 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) obtained from two visits and seven orbits of HST time. We also obtained MERLIN radio maps of the center of NGC 1068 to examine the dependence of the NLR cloud velocities on the radio structure. The radial velocities and velocity dispersions of the bright NLR clouds appear to be unaffected by the radio knots, indicating that the radio jet is not the principal driving force on the outflowing NLR clouds. However, the velocities of the fainter NLR clouds are split near knots in the jet, indicating a possible interaction. 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 parsec similar to that seen in other Seyfert galaxies, indicating common acceleration/deceleration mechanisms.
We present measurements of radial velocities for the narrow-line region gas (NLR) in the Seyfert 2 galaxy Mrk 3 out to ~1 kpc from the nucleus. The observations consist of two datasets, both using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope: 1) An [O III] slitless spectrum with the G430M grating of the inner 3 around the nucleus, and 2) a long-slit observation centered on the nucleus (PA = 71 deg) using the G430L grating and the 52 x 0.1 aperture. Our results produce radial velocity maps of the emission-line gas. These maps indicate general trends in the gas motion, which include: blueshifts and redshifts on either side of the nucleus, steep velocity rises from systemic up to ~ +/-700 km/s taking place in the inner 0.3 (0.8 kpc) both east and west of the nucleus, gradual velocity descents back to near-systemic values from 0.3-1.0, slightly uneven velocity amplitudes on each side of the nucleus, and narrow velocity ranges over the entire observed region. When fitted to kinematic modeling programs for the NLR gas, the data clearly favor a model where the gas exists in a partially filled bicone, is accelerated radially away from the nucleus, and is followed by a constant deceleration. This geometry and general kinematic model is in agreement with previous work done on the NLR gas of NGC 1068 and NGC 4151. On scales of hundreds of parsecs, we conclude that radial outflow may be a common feature of Seyfert galaxies.
We present a study of the distribution of [O III] $lambda$5007 and [O II] $lambda$3727 emission in the Narrow Line Region (NLR) of the Seyfert 1 galaxy NGC 4151. While the NLR of NGC 4151 exhibits an overall structure consistent with the unified model of Seyfert galaxies, narrow-band [O III] and [O II] images obtained with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope reveal significant emission from outside the the emission-line bi-cone. The [O III]/[O II] ratios are lower in these regions, consistent with a weaker ionizing flux. We performed a photoionization modeling analysis of the emission-line gas within a series of annuli, centered on the the central continuum source, with inner radii from 13 to 90 pc. The gas is ionized by radiation that has been attenuated by a relatively highly-ionized absorber (HABS), which completely covers the central source, and a lower-ionization absorber (LABS), which has a covering factor ranging from 0 to 1. We found that the [O III]/[O II] ratios are well fit by assuming that, within each segment of an annulus, some fraction of the NLR gas is completely within the shadow of LABS, while the rest is irradiated by the continuum filtered only by HABS. This suggests that the structure of the NLR is due to filtering of the ionizing radiation by ionized gas, consistent with disk-wind models. One possible scenario is that the low-ionization absorbers are dense knots of gas swept up by a wind.
We use the full broad-band XMM-Newton EPIC data to examine the X-ray spectrum of the nearby Seyfert 2 galaxy NGC 1068, previously shown to be complex with the X-ray continuum being a sum of components reflected/scattered from cold (neutral) and warm (ionised) matter, together with associated emission line spectra. We quantify the neutral and ionised reflectors in terms of the luminosity of the hidden nucleus. Both are relatively weak, a result we interpret on the Unified Seyfert Model by a near side-on view to the putative torus, reducing the visibility of the illuminated inner surface of the torus (the cold reflector), and part of the ionised outflow. A high inclination in NGC 1068 also provides a natural explanation for the large (Compton-thick) absorbing column in the line-of-sight to the nucleus. The emission line fluxes are consistent with the strength of the neutral and ionised continuum components, supporting the robustness of the spectral model.
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