The Spectra of Discrete Radio Sources at Decametric Wavelengths--I

Braude, S. Ya.; Lebedeva, Olga; Megn, A. V.; Ryabov, B. P.; Zhouck, I. N.

doi:10.1093/mnras/143.3.289

Cited by 42 publications

(21 citation statements)

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“…To do that, we collected the total flux measurements available in the literature in the frequency range from 10 to 1400 MHz (Braude et al 1969;Bridle & Purton 1968;Roger et al 1969;Viner & Erickson 1975;Kellermann et al 1969;Wright & Otrupcek 1990). Each data-point was corrected to match the Roger et al (1973;RBC) flux scale with correction factors from Laing & Peacock (1980) and Scaife & Heald (2012).…”

Section: Absolute Flux Densitymentioning

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: Absolute Flux Densitymentioning

confidence: 99%

M 87 at metre wavelengths: the LOFAR picture

Gasperin

Orrù

Murgia

et al. 2012

A&A

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“…The average rest-frame break frequency from the sample of Liu et al (1992) is GHz. Second, in order to estimate the minimum n p 8.9 ‫ע‬ 7.0 b synchrotron frequency, we note that from Braude et al (1969) (even though the measurements are likely to be extremely inaccurate) it is clear that many FR II sources are very strong emitters down to frequencies at least as low as 12.6 MHz. Thus, we pick in the quasar rest frame.…”

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confidence: 99%

An Independent Derivation of the Oxford Jet Kinetic Luminosity Formula

Punsly

2005

ApJ

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This Letter presents a theoretical derivation of an estimate for a radio source jet kinetic luminosity. The expression yields jet powers that are quantitatively similar to a more sophisticated empirical relation published by C. Willott, K. Blundell, and S. Rawlings at Oxford. The formula allows one to estimate the jet kinetic luminosity from the measurement of the optically thin radio lobe emission in quasars and radio galaxies. Motivated by recent X-ray observations, the derivation assumes that most of the energy in the lobes is in plasma thermal energy with a negligible contribution from magnetic energy (not equipartition). The close agreement of the two independent expressions makes the veracity of these estimates seem very plausible.

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“…-The spectra of numerous discrete sources in the Northern sky were obtained in decameter range with the UTR-2 (Bazelyan et al 1965;Braude et al 1969;Braude et al 1970;Braude et al 1995;). -Decameter wavelength spectral lines (carbon radio recombination lines (RRL) with n > 600) were discovered; the LF RRL's as method for diagnostics of the cold ISM was developed, including for detection of extremely (n > 1000) high principal quantum numbers (Konovalenko & Sodin 1981;Stepkin et al 2007).…”

Section: Important Results Of Braude's Teammentioning

confidence: 99%

The beginnings of decameter radio astronomy: pioneering works of Semen Ya. Braude and his followers in Ukraine

2007

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Key words techniques: low-frequency astronomy -instrumentation: interferometers -history and philosophy of astronomy -obituaries, biographies S.Ya. Braude (1911 was the well-known radio astronomer, one of the founders of low-frequency astronomical research in the world, in particular in the former Soviet Union. He began to work in this field of science in 1957, in Kharkiv city (Ukraine), from the design and manufacturing small decameter interferometer ID-1 and ID-2. Since that time Braude and his team have developed more sophisticated radio decameter telescopes as UTR-1 and UTR-2 (the largest in the world till now) as well as the first decameter VLBI network URAN. They have obtained some important pioneering results about low-frequency radio emission of objects in our Solar system, Galaxy and Metagalaxy by means of these telescopes. In this paper the key events of early history of decameter radio astronomy research in the former USSR are mentioned with emphasizing the role of S. Braude. For the period of 1957-1962, the quotations of Braude's Personal Diary (2003) are first laying open to the public. The most important results obtained by S.Ya. Braude and his followers as well as perspectives of decameter radio astronomy in Ukraine and in the world are highlighted briefly.

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The Spectra of Discrete Radio Sources at Decametric Wavelengths--I

Cited by 42 publications

References 0 publications

M 87 at metre wavelengths: the LOFAR picture

M 87 at metre wavelengths: the LOFAR picture

An Independent Derivation of the Oxford Jet Kinetic Luminosity Formula

The beginnings of decameter radio astronomy: pioneering works of Semen Ya. Braude and his followers in Ukraine

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