Low frequency radio observations of galaxy clusters and groups
This book uses new data from the very low radio frequency telescope LOFAR to analyse the magnetic structure in the giant radio galaxy NGC6251. This analysis reveals that the magnetic field strength in the locality of this giant radio galaxy is an order of magnitude lower than in other comparable sys...
| Main Author: | Cantwell, Thérèse, |
|---|---|
| Other Authors: | SpringerLink (Online Service) |
| Format: | eBook |
| Language: | English |
| Published: |
Cham, Switzerland :
Springer,
[2018]
|
| Physical Description: |
1 online resource : illustrations. |
| Series: |
Springer theses.
|
| Subjects: |
| Summary: |
This book uses new data from the very low radio frequency telescope LOFAR to analyse the magnetic structure in the giant radio galaxy NGC6251. This analysis reveals that the magnetic field strength in the locality of this giant radio galaxy is an order of magnitude lower than in other comparable systems. Due to the observational limitations associated with capturing such huge astrophysical structures, giant radio galaxies are historically a poorly sampled population of objects; however, their preferential placement in the more rarefied regions of the cosmic web makes them a uniquely important probe of large-scale structures. In particular, the polarisation of the radio emissions from giant radio galaxies is one of the few tools available to us that can be used to measure magnetic fields in regions where the strength of those fields is a key differentiator for competing models of the origin of cosmic magnetism. Low frequency polarisation data are crucial for detailed analyses of magnetic structure, but they are also the most challenging type of observational data to work with. This book presents a beautifully coupled description of the technical and scientific analysis required to extract valuable information from such data and, as the new generation of low frequency radio telescopes reveals the larger population of giant radio galaxies, it offers a significant resource for future analyses. |
|---|---|
| Item Description: |
Doctoral Thesis accepted by the University of Manchester, Manchester, UK. Includes bibliographical references and index. Intro; Supervisor's Foreword; Preface; Declaration; Acknowledgements; Contents; List of Figures; List of Tables; 1 Introduction; 1.1 Galaxy Clusters and Groups; 1.1.1 Cluster Dynamical State; 1.1.2 Diffuse Radio Emission in Galaxy Clusters; 1.1.3 Faraday Rotation in Galaxy Clusters; 1.1.4 Radio Halo Scaling Relationships; 1.1.5 Galaxy Groups; 1.2 Active Galactic Nuclei; 1.2.1 Radio Galaxies; 1.2.2 Quasars, Blazars, and Seyferts; 1.2.3 A Unified Model for AGN; 1.2.4 AGN and Feedback; 1.2.5 Particle Energetics; 1.2.6 Giant Radio Galaxies; 1.3 Astrophysical Processes; 1.3.1 Synchrotron Emission. 1.3.2 Bremsstrahlung Radiation1.3.3 Faraday Rotation; 1.4 Structure of Thesis; References; 2 Techniques and Data Calibration; 2.1 Radio Interferometry; 2.1.1 Why Is Interferometry Needed; 2.1.2 Basic Interferometry; 2.2 Calibrating Interferometric Data; 2.2.1 Ionospheric Effects; 2.3 Imaging Techniques; 2.3.1 Multiscale Imaging; 2.3.2 W-Projection; 2.4 Rotation Measure Synthesis; 2.5 QU Fitting; 2.6 Instruments; 2.6.1 GMRT; 2.6.2 LOFAR; 2.6.3 VLA; 2.6.4 KAT-7; References; 3 A Newly-Discovered Radio Halo in Merging Cluster MACS J2243.3-093; 3.1 Introduction; 3.2 Observations and Data Reduction. 3.2.1 KAT-73.2.2 GMRT; 3.3 Results; 3.3.1 MACS J2243.3-0935 at>1 GHz; 3.3.2 MACS J2243.3-0935 at <1 GHZ; 3.4 Discussion; 3.4.1 A Giant Radio Halo in MACS J2243.3-0935; 3.4.2 Possible Radio Relics in MACS J2243.3-0935; 3.5 Conclusion; References; 4 GMRT Observations of Three Highly Disturbed Clusters; 4.1 Introduction; 4.2 Observations and Data Reduction; 4.3 Results; 4.3.1 A07; 4.3.2 A1235; 4.3.3 A2055; 4.3.4 New Upper Limits; 4.4 Discussion; 4.5 Conclusion and Future Work; 4.5.1 Future Work; References; 5 LOFAR HBA Observations of NGC 6251; 5.1 Introduction. 5.2 Observations and Data Reduction5.2.1 HBA Observations; 5.2.2 Archival Data; 5.3 Results; 5.3.1 Total Intensity Maps; 5.3.2 Internal Pressure; 5.3.3 Polarisation in NGC 6251; 5.4 Discussion; 5.5 Conclusions; References; 6 Conclusions; Index. This book uses new data from the very low radio frequency telescope LOFAR to analyse the magnetic structure in the giant radio galaxy NGC6251. This analysis reveals that the magnetic field strength in the locality of this giant radio galaxy is an order of magnitude lower than in other comparable systems. Due to the observational limitations associated with capturing such huge astrophysical structures, giant radio galaxies are historically a poorly sampled population of objects; however, their preferential placement in the more rarefied regions of the cosmic web makes them a uniquely important probe of large-scale structures. In particular, the polarisation of the radio emissions from giant radio galaxies is one of the few tools available to us that can be used to measure magnetic fields in regions where the strength of those fields is a key differentiator for competing models of the origin of cosmic magnetism. Low frequency polarisation data are crucial for detailed analyses of magnetic structure, but they are also the most challenging type of observational data to work with. This book presents a beautifully coupled description of the technical and scientific analysis required to extract valuable information from such data and, as the new generation of low frequency radio telescopes reveals the larger population of giant radio galaxies, it offers a significant resource for future analyses. |
| Physical Description: |
1 online resource : illustrations. |
| Bibliography: |
Includes bibliographical references and index. |
| ISBN: |
9783319979762 3319979760 9783319979779 3319979779 |