R. Ekers - Academia.edu (original) (raw)

Papers by R. Ekers

Highlights of Astronomy, 1989

An Introduction to Radio Astronomy

Five decades ago, astronomers finally broke free of the boundaries of light when a new science, r... more Five decades ago, astronomers finally broke free of the boundaries of light when a new science, radio astronomy, was born. This new way of "seeing" rapidly uncovered a range of unexpected objects in the cosmos. This was our first view of the non-thermal universe, and our first unobscured view of the universe. In its short life, radio astronomy has had an unequalled record of discovery, including four Nobel prizes: Big-Bang radiation, neutron stars, aperture synthesis and gravitational radiation. Radio telescopes have followed the pattern of exponential growth generally seen in flourishing areas of science and technology and there is no technical reason for this not to continue, but to do so will require a shift in technology that will set new challenges. New technologies have made it possible to construct an affordable radio telescope with collecting area of one square km the SKA. Such a telescope would be so powerful that we could expand our knowledge of the universe from the earliest stages of its formation through to planetary exploration with greatly enhanced spacecraft communications. The SKA will join the new generation of telescopes at other wavebands with the sensitivity and resolution to image the earliest phases of galaxy formation, as well as greatly extending the range of unique science accessible at radio wavelengths. We already know how to build an SKA, the issue is how to build the most cost effective SKA, and how to maximize the science we can do with it. The path we have chosen to achieve this vision is through international collaboration. Following the pattern of other successful international collaborations in science we have started this process early, and we are already benefiting from the level of innovation generated by our international interactions.

Proceedings of From Planets to Dark Energy: the Modern Radio Universe — PoS(MRU), Oct 14, 2008

We have made a radio survey-the Australia Telescope Low Brightness Survey (ATLBS)-of 8.4 square d... more We have made a radio survey-the Australia Telescope Low Brightness Survey (ATLBS)-of 8.4 square degrees sky area, using the Australia Telescope Compact Array in the 20-cm band, in an observing mode designed to provide wide-field images with exceptional sensitivity in surface brightness, and thereby explore a new parameter space in radio source populations. The goals of this survey are to quantify the distribution in angular sizes, particularly at weak surface brightness levels: this has implications for the confusion in deep surveys with the SKA. The survey is expected to lead to a census of the radio emission associated with low-power radio galaxies at redshifts 1-3, without any missing extended emission, and hence a study of the cosmic evolution of low-power radio galaxies to higher redshift and a comprehensive study of the AGN feedback during the intense black hole growth phase during this redshift range.

Proceedings of The 34th International Cosmic Ray Conference — PoS(ICRC2015), 2016

Monthly Notices of the Royal Astronomical Society, 1992

Monthly Notices of the Royal Astronomical Society, 2016

Pulsars are the only cosmic radio sources known to be sufficiently compact to show diffractive in... more Pulsars are the only cosmic radio sources known to be sufficiently compact to show diffractive interstellar scintillations. Images of the variance of radio signals in both time and frequency can be used to detect pulsars in large-scale continuum surveys using the next generation of synthesis radio telescopes. This technique allows a search over the full field of view while avoiding the need for expensive pixel-by-pixel high time resolution searches. We investigate the sensitivity of detecting pulsars in variance images. We show that variance images are most sensitive to pulsars whose scintillation timescales and bandwidths are close to the subintegration time and channel bandwidth. Therefore, in order to maximize the detection of pulsars for a given radio continuum survey, it is essential to retain a high time and frequency resolution, allowing us to make variance images sensitive to pulsars with different scintillation properties. We demonstrate the technique with Murchision Widefield Array data and show that variance images can indeed lead to the detection of pulsars by distinguishing them from other radio sources.

Proceedings of the International Astronomical Union, 2014

I present examples of radio AGN with binary nuclei which provide the direct radio evidence for bi... more I present examples of radio AGN with binary nuclei which provide the direct radio evidence for binary Super Massive Black Holes (SMBH) driving the AGN activity. There is also other evidence for distorted radio morphology and periodic variability which may indicate the presence of a second (inactive) SMBH. Finally I enumerate a number of possible radio tracers for the binary SMBH merger events.

The Large Scale Structure of the Universe, 1978

Structure and Properties of Nearby Galaxies, 1978

Extragalactic Radio Sources, 1982

Because of the relatively long wavelength of radio waves a conventional monolithic radio telescop... more Because of the relatively long wavelength of radio waves a conventional monolithic radio telescope with the angular resolution of an optical telescope would require an aperture many kilometers in diameter. It would be prohibitively expensive and probably impossible to construct. The development of the digital computer made it possible to achieve this resolution with "aperture synthesis" radio telescopes. These telescope

Currently the ATCA only has one reliable primary flux calibrator at 3- and 7-mm, Uranus. Unfortun... more Currently the ATCA only has one reliable primary flux calibrator at 3- and 7-mm, Uranus. Unfortunately, Uranus is not always visible during short 6-8 hour runs, and is not useful at all in the higher resolution arrays. We are proposing to search for new potential primary flux calibrators at these wavelengths, and then monitor these new sources for flux stability.

Astronomy and …, 1991

... 12, 187 Fomalont EB, Bridle AH, Willis AG., Perley RA, 1980, APJ 237, 419 Garrington ST., Lea... more ... 12, 187 Fomalont EB, Bridle AH, Willis AG., Perley RA, 1980, APJ 237, 419 Garrington ST., Leahy JP, Conway RG, Laing RA, 1988, Nat 331 ... 324, 198 Königl A., Choudhuri AR., 1985, APJ 289, 173 Laing RA, 1980, MNRAS 193, 439 Laing RA, 1988, Nat 331, 149 Lau JC, 1981, J ...

The Astrophysical Journal, 1969

Abstract : The complete polarization characteristics of a number of pulsating radio sources have ... more Abstract : The complete polarization characteristics of a number of pulsating radio sources have been determined at 13 cm. Both a stable average and a time varying component of the polarized radiation were found. A change in the position angle of the linear component during the course of the pulse is a common property; however the high degree of linear polarization and constant rotation of angle seen for PSR0833-45 is atypical. (Author)

Contents: 1. Introduction. 2. Diagnosing errors. 3. Examples. 4. Diagnostic tools.

… Perley, FR Schwab, AH …, 1986

Synthesis imaging. Course notes from an NRAO summer school, held at Socorro, New Mexico, USA, 5 -... more Synthesis imaging. Course notes from an NRAO summer school, held at Socorro, New Mexico, USA, 5 - 9 August 1985.. RA Perley, FR Schwab, AH Bridle (Editors) with opening remarks by RD Ekers.NRAO Workshop No. 13. National Radio Astronomy Observatory, POBox 2, ...

Proceedings of the IEEE, 1983

... NAPIER er af.: VLA MODERN SYNTHESIS RADIO TELESCOPE ... On the other hand, an array of nu ant... more ... NAPIER er af.: VLA MODERN SYNTHESIS RADIO TELESCOPE ... On the other hand, an array of nu antennas allows up to n a( na - 1)/2 pairs to be operated simultaneously, and in the case of the VLA, for which nu = 27, an image can be synthesized in a single transit of a source. ...