Kamali, Fateme: Radio Continuum of Galaxies with H2O-Megamaser-Disks. - Bonn, 2019. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5n-56481
@phdthesis{handle:20.500.11811/8108,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5n-56481,
author = {{Fateme Kamali}},
title = {Radio Continuum of Galaxies with H2O-Megamaser-Disks},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2019,
month = nov,

note = {Galaxies with H2O-megamaser-disks are low luminosity active galaxies where 22GHz H2O-maser emission is detected in their accretion disk surrounding the central supermassive black hole (SMBH). Furthermore, given that the geometry of the maser disk is known, they provide a unique view of the central region of active galaxies, allowing us to investigate the spatial relationship of the accretion disk with jets on the same physical scales. In this work, we attempt to study the alignment between the radio jet and the associated rotation axis of the sub-pc accretion disks which are traced by the 22GHz H2O-megamaser emission. This is an essential part of the paradigm describing active galactic nuclei.
Our observations were carried out using radio interferometer arrays with three different resolutions, corresponding to physical scales of ~145 pc, ~34 pc, and ~2 pc at a fiducial distance of 85 Mpc (mean of distances in our sample). Our observations provide a larger sample where morphology or geometry of both accretion disk and jets are observed on similar physical scales.
On kiloparsec scales, our observations were carried out using the Karl G. Jansky Very Large Array (VLA) at 33GHz. We detect radio emission in 87% of the sources in our sample. We find evidence for biconical extended jets on scales >300 pc for four sources. Seventeen other sources show only one component, often accompanied by extended emission. Among the sources with biconical structure where the maser disk orientation is known, we find that the jet-like 33GHz continuum feature in one source (NGC4388) appears to be perpendicular to the maser disk's orientation.
On scales of ~100 pc, we used the enhanced Multi-Element Radio Linked Interferometer Network (eMERLIN) at 5GHz to investigate the radio emission. We detected radio emission in 56% of the sources in our sample.
Four sources show biconical morphologies, three sources remain unresolved, and three other sources show extended emission. For four of the detected sources, the orientation of the maser disk is known. In all four, the radio continuum is misaligned with the rotation axis of the disk, but by not more than 37 degree relative to the disk's rotation axis.
On parsec-scales, using the Very Long Baseline Array (VLBA) at 5GHz, we detect 28% of the sources, where two sources show only one component, and three other sources show multiple components in the radio maps.
Among the five detections, four of them exhibit a maser disk with known orientation. For all four of these sources, the radio continuum is misaligned relative to the rotation axis of the maser disk, but with a 99.1% confidence level, the orientations are not random and are confined to a cone within 32 degree of the maser disk’s normal. Among the four sources the
misalignment of the radio continuum with respect to the normal vector to the maser disk is smaller when the inner radius of the maser disk is larger.
Furthermore, based on the spectral indices, brightness temperatures and multi-scale morphologies, we conclude that the radio emission in the majority of our sources is dominated by both outflow and star formation. Further observations, such as full polarization studies and kinematic studies of outflows, will help construct a more complete picture of the central region of active galaxies.},

url = {http://hdl.handle.net/20.500.11811/8108}
}

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