Low Frequency Radio Observations Of Galaxy Clusters And Groups

Author : Thérèse Cantwell
Publisher : Springer
ISBN 13 : 3319979760
Total Pages : 134 pages
Book Rating : 4.62/5 ( download)

DOWNLOAD NOW!

Download or read book Low Frequency Radio Observations of Galaxy Clusters and Groups written by Thérèse Cantwell and published by Springer. This book was released on 2018-09-01 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Author : Alexander Drabent
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.87/5 ( download)

DOWNLOAD NOW!

Download or read book Diffuse Radio Emission at Low Frequencies in Merging Galaxy Clusters written by Alexander Drabent and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extended diffuse radio features so-called radio halos radio relics and radio mini-halos are found in about 100 galaxy clusters. The radio emission originates from relativistic electrons suffering synchrotron losses in the magnetized intra-cluster medium. Little is known about the mechanisms how electrons in the intra-cluster medium get accelerated to relativistic energies. Observations at low radio frequencies permit the analysis of the distribution of the population of aged relativistic electrons. In this work we analyzed in the context of the WSRT 346 MHz Legacy Survey ten galaxy clusters with already known diffuse radio sources and yet unclassified sources. We confirm radio relics in three clusters radio halos in five clusters and classified a radio relic candidate as a radio galaxy. Furthermore we revealed radio features with remarkable morphology in the galaxy cluster Abell 2069. Abell 2069 is a complex merging galaxy cluster which shows two distinct X-ray peaks. The main cluster component evidently possesses a radio halo and the subcomponent exhibits ultra-steep spectrum diffuse radio emission of uncertain nature. We conducted follow-up observations on Abell 2069 with LOFAR in the frequency range from 120 to 180 MHz. We complemented our investigation of Abell 2069 with GMRT observations at 322 MHz and 608 MHz as well as with archival Chandra X-ray data. Our analysis confirms the presence of a radio halo in the main cluster component. Furthermore we classify the diffuse radio emission in the subcluster as radio mini-halo. We detected signatures of fossil plasma ejected during a former active phase of an Active Galactic Nuclei in the subcluster. A cold front in the subcomponent suggests the presence of internal gas sloshing which could have induced bulk motions and turbulence in the subcluster. Both mechanisms together may have redistributed and re-accelerated the fossil plasma and caused the diffuse radio emission.

Author : Alex Clarke
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.49/5 ( download)

DOWNLOAD NOW!

Download or read book Extragalactic Radio Observations at Low Frequencies written by Alex Clarke and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : L. Feretti
Publisher : Springer Science & Business Media
ISBN 13 : 0306480964
Total Pages : 329 pages
Book Rating : 4.66/5 ( download)

DOWNLOAD NOW!

Download or read book Merging Processes in Galaxy Clusters written by L. Feretti and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mergers are the mechanisms by which galaxy clusters are assembled through the hierarchical growth of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Many of the observed properties of clusters depend on the physics of the merging process. These include substructure, shock, intra cluster plasma temperature and entropy structure, mixing of heavy elements within the intra cluster medium, acceleration of high-energy particles, formation of radio halos and the effects on the galaxy radio emission. This book reviews our current understanding of cluster merging from an observational and theoretical perspective, and is appropriate for both graduate students and researchers in the field.

Author : Willem Bijleveld
Publisher :
ISBN 13 :
Total Pages : 112 pages
Book Rating : 4.38/5 ( download)

DOWNLOAD NOW!

Download or read book Groups and Clusters of Galaxies written by Willem Bijleveld and published by . This book was released on 1984 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author :
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.64/5 ( download)

DOWNLOAD NOW!

Download or read book Directions for Space-Based Low Frequency Radio Astronomy. 1. Systems Considerations written by and published by . This book was released on 1997 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although observations at the low end of the radio astronomy spectrum were the pre- cursor of all work in radio astronomy, this portion of the spectrum has languished for decades while research at the upper radio frequencies has flourished. Previous work at low frequencies (below 30 MHz) has clearly shown that sensitive high-resolution ground-based observations are extremely difficult to make, if not impossible. Observation quality at low frequencies can leap forward using space-based interferometers. Radio telescopes such as these can be built principally from "off-the-shelf' components. A relatively low cost space program can make great strides in deploying arrays of antennas and receivers that would produce data contributing significantly to our understanding of galaxies and galactic nebulae. This paper discusses the various aspects of low-frequency telescopes such as past history and significant issues like sensitivity, interference, baseline calibration, wave scattering, and mapping. All aspects of the first stages of space-based, low-frequency radio telescopes can be accomplished with no dependencies on new types of hardware. The time has come to open the final electromagnetic frontier in astronomy.

Author :
Publisher :
ISBN 13 :
Total Pages : 658 pages
Book Rating : 4.62/5 ( download)

DOWNLOAD NOW!

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 658 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : Cosmos Dumba
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.74/5 ( download)

DOWNLOAD NOW!

Download or read book Extended Diffuse Radio Emission in Galaxy Clusters written by Cosmos Dumba and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxy clusters are the most massive gravitationally bound systems in the universe which grow through mergers with other clusters, galaxy groups, and accretion of gas. The mergers generate shocks and turbulence in the intra-cluster medium (ICM). Along the shock edges, particles are accelerated to relativistic energies through multiple crossings at the shock front. The extended diffuse emission sources formed as a result are commonly classified as radio halos and radio relics. The precise nature and origin of the relativistic particles is nevertheless not well understood. We study the nature of the radio relic candidate in Abell 115. We obtain it's spectral properties using radio continuum observations at 150\,MHz with LOFAR, 610\,MHz with the GMRT, and 1.5\,GHz with the VLA. We confirm it's nature as a radio relic. Polarization analyses suggest that part of the large scale synchrotron source is embedded in a region of high ICM density. We show that the galaxy cluster A1430 hosts a two-component radio halo using observations at 150\,MHz with LOFAR. We obtain the spectral index of the radio halo and derive estimates of the radio power at 1.4 GHz. We also show that a part of the radio halo could be produced via turbulence and the rest lies in a region compressed by the merger via adiabatic compression. Using a 100-m single dish radio telescope, we observe the galaxy clusters PSZ1-G108, Abell 746, 0809+39, and Abell 1367. We detected the polarised flux at 4.85 GHz in all the sources that were previously labelled as radio relics. The radio spectra of the integreted emission below 4.85 GHz can be well fitted with a single power law for all the radio relics. Polarisation observations of radio synchrotron sources offer a method of measuring the strength and geometry of the shock front. The observations of the galaxy clusters PSZ1-G108, Abell 746, 0809+39, and Abell 1367 show that radio relics' spectral properties are well represented by a single power-law below 5GHz.

Author : Siegfried Böhme
Publisher : Springer Science & Business Media
ISBN 13 : 366212310X
Total Pages : 796 pages
Book Rating : 4.02/5 ( download)

DOWNLOAD NOW!

Download or read book Literature 1977, Part 2 written by Siegfried Böhme and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts, which has appeared in semi-annual volumes since 1969, is de voted to the recording, summarizing and indexing of astronomical publications throughout the world. It is prepared under the auspices of the International Astronomical Union (according to a resolution adopted at the 14th General Assembly in 1970). Astronomy and Astrophysics Abstracts aims to present a comprehensive documentation of literature in all fields of astronomy and astrophysics. Every effort will be made to ensure that the average time interval between the date of receipt of the original literature and publication of the abstracts will not exceed eight months. This time interval is near to that achieved by monthly abstracting journals, com pared to which our system of accumulating abstracts for about six months offers the advantage of greater convenience for the user. Volume 20 contains literature published in 1977 and received before February 20, 1978; some older literature which was received late and which is not recorded in earlier volumes is also included. We acknowledge with thanks contributions to this volume by Dr. J. BouSka, Prague, who surveyed journals and publications in Czech and supplied us with abstracts in English, and by Prof. P. Brosche, Bonn, who supplied us with literature concerning some border fields of astronomy.

Author : Cosmos Dumba
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.66/5 ( download)

DOWNLOAD NOW!

Download or read book Extended Diffuse Radio Emission in Merging Galaxy Clusters written by Cosmos Dumba and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Galaxy clusters are the most massive gravitationally bound systems in the universe which grow through mergers with other clusters, galaxy groups, and accretion of gas. The mergers generate shocks and turbulence in the intra-cluster medium (ICM). Along the shock edges, particles are accelerated to relativistic energies through multiple crossings at the shock front. The extended diffuse emission sources formed as a result are commonly classified as radio halos and radio relics. The precise nature and origin of the relativistic particles is nevertheless not well understood. We study the nature of the radio relic candidate in Abell 115. We obtain it's spectral properties using radio continuum observations at 150\,MHz with LOFAR, 610\,MHz with the GMRT, and 1.5\,GHz with the VLA. We confirm it's nature as a radio relic. Polarization analyses suggest that part of the large scale synchrotron source is embedded in a region of high ICM density. We show that the galaxy cluster A1430 hosts a two-component radio halo using observations at 150\,MHz with LOFAR. We obtain the spectral index of the radio halo and derive estimates of the radio power at 1.4 GHz. We also show that a part of the radio halo could be produced via turbulence and the rest lies in a region compressed by the merger via adiabatic compression. Using a 100-m single dish radio telescope, we observe the galaxy clusters PSZ1-G108, Abell 746, 0809+39, and Abell 1367. We detected the polarised flux at 4.85 GHz in all the sources that were previously labelled as radio relics. The radio spectra of the integreted emission below 4.85 GHz can be well fitted with a single power law for all the radio relics. Polarisation observations of radio synchrotron sources offer a method of measuring the strength and geometry of the shock front. The observations of the galaxy clusters PSZ1-G108, Abell 746, 0809+39, and Abell 1367 show that radio relics' spectral properties are well represented by a single power-law below 5GHz.