Gas Cloud Kinematics near the Nucleus of NGC 4151

1998 ◽  
Vol 492 (2) ◽  
pp. L115-L119 ◽  
Author(s):  
J. B. Hutchings ◽  
D. M. Crenshaw ◽  
M. E. Kaiser ◽  
S. B. Kraemer ◽  
D. Weistrop ◽  
...  
Keyword(s):  
Ngc 4151 ◽  
Cloud Kinematics ◽  
Gas Cloud

scholarly journals Intelligent Mobile Wireless Network for Toxic Gas Cloud Monitoring and Tracking

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3625
Author(s):  
Mateusz Krzysztoń ◽  
Ewa Niewiadomska-Szynkiewicz
Keyword(s):  
Data Exchange ◽  
Mobility Model ◽  
Model Parameters ◽  
Toxic Substances ◽  
Cloud Detection ◽  
Gas Dispersion ◽  
Gas Concentration ◽  
Cloud Monitoring ◽  
Optimal Values ◽  
Gas Cloud

Intelligent wireless networks that comprise self-organizing autonomous vehicles equipped with punctual sensors and radio modules support many hostile and harsh environment monitoring systems. This work’s contribution shows the benefits of applying such networks to estimate clouds’ boundaries created by hazardous toxic substances heavier than air when accidentally released into the atmosphere. The paper addresses issues concerning sensing networks’ design, focussing on a computing scheme for online motion trajectory calculation and data exchange. A three-stage approach that incorporates three algorithms for sensing devices’ displacement calculation in a collaborative network according to the current task, namely exploration and gas cloud detection, boundary detection and estimation, and tracking the evolving cloud, is presented. A network connectivity-maintaining virtual force mobility model is used to calculate subsequent sensor positions, and multi-hop communication is used for data exchange. The main focus is on the efficient tracking of the cloud boundary. The proposed sensing scheme is sensitive to crucial mobility model parameters. The paper presents five procedures for calculating the optimal values of these parameters. In contrast to widely used techniques, the presented approach to gas cloud monitoring does not calculate sensors’ displacements based on exact values of gas concentration and concentration gradients. The sensor readings are reduced to two values: the gas concentration below or greater than the safe value. The utility and efficiency of the presented method were justified through extensive simulations, giving encouraging results. The test cases were carried out on several scenarios with regular and irregular shapes of clouds generated using a widely used box model that describes the heavy gas dispersion in the atmospheric air. The simulation results demonstrate that using only a rough measurement indicating that the threshold concentration value was exceeded can detect and efficiently track a gas cloud boundary. This makes the sensing system less sensitive to the quality of the gas concentration measurement. Thus, it can be easily used to detect real phenomena. Significant results are recommendations on selecting procedures for computing mobility model parameters while tracking clouds with different shapes and determining optimal values of these parameters in convex and nonconvex cloud boundaries.

scholarly journals Mass outflow of the X-ray emission line gas in NGC 4151

2020 ◽  
Vol 15 (S359) ◽  
pp. 131-135
Author(s):  
S. B. Kraemer ◽  
T. J. Turner ◽  
D. M. Crenshaw ◽  
H. R. Schmitt ◽  
M. Revalski ◽  
...  
Keyword(s):  
Emission Line ◽  
Total Mass ◽  
High Energy ◽  
Model Parameters ◽  
Zeroth Order ◽  
Space Telescope ◽  
X Ray ◽  
Ngc 4151 ◽  
Outflow Rate ◽  
Mass Outflow

AbstractWe have analyzed Chandra/High Energy Transmission Grating spectra of the X-ray emission line gas in the Seyfert galaxy NGC 4151. The zeroth-order spectral images show extended H- and He-like O and Ne, up to a distance r ˜ 200 pc from the nucleus. Using the 1st-order spectra, we measure an average line velocity ˜230 km s–1, suggesting significant outflow of X-ray gas. We generated Cloudy photoionization models to fit the 1st-order spectra; the fit required three distinct emission-line components. To estimate the total mass of ionized gas (M) and the mass outflow rates, we applied the model parameters to fit the zeroth-order emission-line profiles of Ne IX and Ne X. We determined an M ≍ 5.4 × 105Mʘ. Assuming the same kinematic profile as that for the [O III] gas, derived from our analysis of Hubble Space Telescope/Space Telescope Imaging Spectrograph spectra, the peak X-ray mass outflow rate is approximately 1.8 Mʘ yr–1, at r ˜ 150 pc. The total mass and mass outflow rates are similar to those determined using [O III], implying that the X-ray gas is a major outflow component. However, unlike the optical outflows, the X-ray emitting mass outflow rate does not drop off at r > 100pc, which suggests that it may have a greater impact on the host galaxy.

On the path toward a universal outflow mechanism in light of NGC 4151 and NGC 1068

2020 ◽  
Vol 15 (S359) ◽  
pp. 283-284
Author(s):  
D. May ◽  
J. E. Steiner ◽  
R. B. Menezes
Keyword(s):  
Near Infrared ◽  
Feedback Mechanism ◽  
Data Cube ◽  
Low Velocity ◽  
Ionized Gas ◽  
Ngc 4151 ◽  
Molecular Outflow ◽  
Ngc 1068 ◽  
Field Unit ◽  
First Time

AbstractWe use near-infrared Integral Field Unit (IFU) data to analyze the galaxies NGC 4151 and NGC 1068, which have very different Eddington ratios - ˜50 times lower for NGC 4151. Together with a detailed data cube treatment methodology, we reveal remarkable similarities between both AGN, such as the detection of the walls of an “hourglass” structure for the low-velocity [Fe ii] emission with the high-velocity emission within this hourglass; a molecular outflow - detected for the first time in NGC 4151; and the fragmentation of an expanding molecular bubble into bullets of ionized gas. Such observations suggest that NGC 4151 could represent a less powerful and more compact version of the outflow seen in NGC 1068, suggesting a universal feedback mechanism acting in quite different AGN.

scholarly journals The Balmer lines in the Seyfert Galaxies NGC 5548 and NGC 4151

1972 ◽  
Vol 44 ◽  
pp. 155-159
Author(s):  
R. Weymann ◽  
R. Cromwell
Keyword(s):  
Electron Scattering ◽  
Small Volume ◽  
Seyfert Galaxies ◽  
Ngc 4151 ◽  
Transient Nature ◽  
Balmer Lines ◽  
Ngc 5548

The profiles of the Balmer lines in NGC 5548 as reported by Dibai et al. (1968) were somewhat asymmetric, whereas those reported by Anderson (1970) are smooth and symmetric. We present profiles which are strongly asymmetric, resembling those of Dibai et al. Evidently electron scattering is not the sole principal broadening agent and we must deal with velocities ∼ 2500 km s−1 in a very small volume.The transient nature of the P-Cygni type profiles in the Balmer lines of NGC 4151 has previously been noted (Cromwell and Weymann, 1970). These lines have since disappeared, at the resolution available to us, in a time of 3 months. A model in which frequent outbursts of shells or filaments produce transient features in the Balmer lines, while the accumulated material from past outbursts produces the relatively stable HeI λ 3889 feature, seems the most plausible.

scholarly journals Is High-Velocity Cloud Complex C Associated with the Galactic Warp?

2003 ◽  
Vol 20 (3) ◽  
pp. 263-269 ◽  
Author(s):  
Daisuke Kawata ◽  
Christopher Thom ◽  
Brad K. Gibson
Keyword(s):  
High Latitude ◽  
High Velocity ◽  
Large Magellanic Cloud ◽  
Alternative Interpretation ◽  
North Polar ◽  
Gas Cloud ◽  
Cloud Complex ◽  
Galactic Warp ◽  
Velocity Cloud ◽  
Spiral Arm

AbstractWe test the hypothesis that high-velocity gas cloud Complex C is actually a high-latitude spiral arm extension in the direction of the Galactic warp, as opposed to the standard interpretation — that of a once extragalactic, but now infalling, gas cloud. A parallel Tree N-body code was employed to simulate the tidal interaction of a satellite perturber with the Milky Way. We find that a model incorporating a perturber of the mass of the Large Magellanic Cloud on a south to north polar orbit, crossing the disk at ˜15 kpc, does yield a high-velocity, high-latitude extension consistent with the spatial, kinematical, and column density properties of Complex C. Unless this massive satellite remains undiscovered because of either a fortuitous alignment with the Galactic bulge (feasible within the framework of the model), or the lack of any associated baryonic component, we conclude that this alternative interpretation appears unlikely.

Optical spectral variability of NGC 4151 during 1990

1997 ◽  
Vol 14 (2) ◽  
pp. 105-118 ◽  
Author(s):  
V. L. Oknyanskij ◽  
E. Van Groningen
Keyword(s):  
Spectral Variability ◽  
Ngc 4151

scholarly journals Optical monitoring of the Seyfert galaxy NGC 4151 and possible periodicities in its historical light curve

2014 ◽  
Vol 14 (8) ◽  
pp. 923-932 ◽  
Author(s):  
Di-Fu Guo ◽  
Shao-Ming Hu ◽  
Jun Tao ◽  
Hong-Xing Yin ◽  
Xu Chen ◽  
...  
Keyword(s):  
Light Curve ◽  
Seyfert Galaxy ◽  
Optical Monitoring ◽  
Ngc 4151

scholarly journals The Mass of the Central Black Hole in the Seyfert Galaxy NGC 4151

2006 ◽  
Vol 647 (2) ◽  
pp. 901-909 ◽  
Author(s):  
Kyle G. Metzroth ◽  
Christopher A. Onken ◽  
Bradley M. Peterson
Keyword(s):  
Black Hole ◽  
Seyfert Galaxy ◽  
Central Black Hole ◽  
Ngc 4151
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