Positions of Three Discrete Sources of Galactic Radio-Frequency Radiation

Bolton, J. G.; Stanley, G. J.; Slee, O. B.

doi:10.1038/164101b0

Cited by 172 publications

(90 citation statements)

References 3 publications

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“…The emission generated directly and indirectly by the AGN has been widely observed at radio (Bolton et al 1949;Mills 1952;Baade & Minkowski 1954;Owen et al 2000), infrared (Shi et al 2007), optical (Biretta et al 1999) and X-ray (Fabricant et al 1980;Feigelson et al 1987;Böhringer et al 1995;Young et al 2002;Forman et al 2007;Million et al 2010) wavelengths. Theoretical and numerical models to interpret these observations have also been developed by e.g.…”

Section: Introductionmentioning

confidence: 99%

M 87 at metre wavelengths: the LOFAR picture

Gasperin

Orrù

Murgia

et al. 2012

A&A

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Context. M 87 is a giant elliptical galaxy located in the centre of the Virgo cluster, which harbours a supermassive black hole of mass 6.4 × 10 9 M , whose activity is responsible for the extended (80 kpc) radio lobes that surround the galaxy. The energy generated by matter falling onto the central black hole is ejected and transferred to the intra-cluster medium via a relativistic jet and morphologically complex systems of buoyant bubbles, which rise towards the edges of the extended halo. Aims. To place constraints on past activity cycles of the active nucleus, images of M 87 were produced at low radio frequencies never explored before at these high spatial resolution and dynamic range. To disentangle different synchrotron models and place constraints on source magnetic field, age and energetics, we also performed a detailed spectral analysis of M 87 extended radio-halo. Methods. We present the first observations made with the new Low-Frequency Array (LOFAR) of M 87 at frequencies down to 20 MHz. Three observations were conducted, at 15−30 MHz, 30−77 MHz and 116−162 MHz. We used these observations together with archival data to produce a low-frequency spectral index map and to perform a spectral analysis in the wide frequency range 30 MHz-10 GHz. Results. We do not find any sign of new extended emissions; on the contrary the source appears well confined by the high pressure of the intracluster medium. A continuous injection of relativistic electrons is the model that best fits our data, and provides a scenario in which the lobes are still supplied by fresh relativistic particles from the active galactic nuclei. We suggest that the discrepancy between the low-frequency radiospectral slope in the core and in the halo implies a strong adiabatic expansion of the plasma as soon as it leaves the core area. The extended halo has an equipartition magnetic field strength of 10 μG, which increases to 13 μG in the zones where the particle flows are more active. The continuous injection model for synchrotron ageing provides an age for the halo of 40 Myr, which in turn provides a jet kinetic power of 6−10 × 10 44 erg s −1 .

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Section: Introductionmentioning

confidence: 99%

M 87 at metre wavelengths: the LOFAR picture

Gasperin

Orrù

Murgia

et al. 2012

A&A

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“…Between early June and late September in 1948, Bolton and Stanley were at Leigh and then Piha, often under appalling weather conditions, but the observations and subsequent reductions (summarised by Slee 1994) resulted in positions for Cygnus A, Taurus A, Virgo A, and Centaurus A that were accurate to a few minutes of arc. This was precise enough to allow tentative optical identifications for the last three sources with bright optical objects (Bolton, Stanley, & Slee 1949). One of these (Taurus A) was the remarkable remnant of the supernova from 1054, known as the Crab Nebula.…”

Section: The Radiophysics Yearsmentioning

confidence: 99%

Gordon James Stanley and the Early Development of Radio Astronomy in Australia and the United States

Kellermann

Orchiston

Slee

2005

Publ. Astron. Soc. Aust

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Abstract:Following the end of the Second World War, the CSIRO Radiophysics Laboratory applied the expertise and surplus radar equipment acquired during the war to problems of astronomy. Gordon Stanley was among the first group of scientists and engineers to work in the exciting new field of radio astronomy. Like many of his contemporaries, he had a strong background in radio and electronics but none in astronomy. At the Radiophysics Laboratory, and later at Caltech, Stanley developed innovative new radio telescopes and sophisticated instrumentation which resulted in important new discoveries that changed, in a fundamental way, our understanding of the Universe. He was one of those who played a key role in the early development of radio astronomy both in Australia and the United States.

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“…The ray is brightest at the inner end, which is 11 "from the nucleus." Early observations around 1947 by the Sydney group found the radio position [5], and the identification with M87 was established, along with that of Centaurus A, though their extragalactic nature was uncertain at the time. However, it soon became clear that they must be extragalactic.…”

Section: The Early Discoveriesmentioning

confidence: 99%

An Old Fogey’s History of Radio Jets

Spencer

2017

Galaxies

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This paper describes a personal view of the discovery of radio jets in celestial radio sources. The existence of narrow, collimated optical features in distant objects has been known about since the early 20th century; however, the advent of radio astronomy in the 1940s and 1950s revealed the existence of a large number of discrete radio sources. The realization that many of these objects were not primarily stellar or local to our own galaxy, but rather extragalactic, followed the determination of accurate radio positions, enabling identifications with optical objects. High-resolution radio interferometers found that they were often compact, and with a double lobed structure, implying outflow from a central object. Shortly afterwards, accurate techniques for the measurement of polarization were developed. However it was not until the advent of synthesis instruments in the 1970s that radio images of the sources were produced, and the existence of radio jets firmly established and their polarization characteristics found.

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Positions of Three Discrete Sources of Galactic Radio-Frequency Radiation

Cited by 172 publications

References 3 publications

M 87 at metre wavelengths: the LOFAR picture

M 87 at metre wavelengths: the LOFAR picture

Gordon James Stanley and the Early Development of Radio Astronomy in Australia and the United States

An Old Fogey’s History of Radio Jets

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