LXXV. The low frequency spectrum of the cygnus (19N4A) and cassiopeia (23N5A) radio sources

AbstractLow-frequency radio emission allows powerful active galactic nuclei (AGN) to be selected in a way that is unaffected by dust obscuration and orientation of the jet axis. It also reveals past activity (e.g. radio lobes) that may not be evident at higher frequencies. Currently, there are too few “radio-loud” galaxies for robust studies in terms of redshift-evolution and/or environment. Hence our use of new observations from the Murchison Widefield Array (the SKA-Low precursor), over the southern sky, to construct the GLEAM 4-Jy Sample (1,860 sources at S151MHz > 4 Jy). This sample is dominated by AGN and is 10 times larger than the heavily relied-upon 3CRR sample (173 sources at S178MHz > 10 Jy) of the northern hemisphere. In order to understand how AGN influence their surroundings and the way galaxies evolve, we first need to correctly identify the galaxy hosting the radio emission. This has now been completed for the GLEAM 4-Jy Sample – through repeated visual inspection and extensive checks against the literature – forming a valuable, legacy dataset for investigating relativistic jets and their interplay with the environment.

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Low-Frequency Spectrum Asymptotics as a Measure of Nonstationarity of Some Geophysical Processes

Computational Seismology and Geodynamics - Selected Papers from Volumes 26 and 27 of Vychislitel'naya Seysmologiya ◽

10.1029/cs003p0097 ◽

2013 ◽

pp. 97-105

Author(s):

V. B. Lysenko ◽

V. F. Pisarenko

Keyword(s):

Frequency Spectrum ◽

Low Frequency ◽

Geophysical Processes

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Extragalactic Radio Sources with Steep Low Frequency Spectra

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/165.3.259 ◽

1973 ◽

Vol 165 (3) ◽

pp. 259-269 ◽

Cited By ~ 28

Author(s):

J. E. Baldwin ◽

P. F. Scott

Keyword(s):

Low Frequency ◽

Radio Sources ◽

Frequency Spectra ◽

Extragalactic Radio Sources

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Preferential acceleration of heavy ions from thermal velocities

Canadian Journal of Physics ◽

10.1139/p68-314 ◽

1968 ◽

Vol 46 (10) ◽

pp. S638-S641 ◽

Cited By ~ 1

Author(s):

D. B. Melrose

Keyword(s):

Frequency Spectrum ◽

High Frequency ◽

Heavy Ions ◽

Crab Nebula ◽

Low Frequency ◽

High Frequency Waves ◽

Hydromagnetic Waves ◽

The Crab Nebula ◽

Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

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Spatially resolved studies of extragalactic jets in high redshift radio galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315002239 ◽

2014 ◽

Vol 10 (S313) ◽

pp. 231-235

Author(s):

Leah K. Morabito ◽

Adam Deller ◽

J. B. R. Oonk ◽

Huub Röttgering ◽

George Miley

Keyword(s):

High Redshift ◽

Low Frequency ◽

Radio Galaxies ◽

Radio Sources ◽

Spatially Resolved ◽

Long Baseline ◽

Early Results ◽

Spectrum Radio ◽

Extragalactic Jets ◽

Frequency Survey

AbstractThe correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

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ASSESSMENT OF THE ELECTROMAGNETIC ENVIRONMENT AND RADIO MONITORING OF SIGNAL PROPAGATION AND RECEPTION CONDITIONS

Электросвязь ◽

10.34832/elsv.2020.8.7.006 ◽

2020 ◽

Author(s):

С.В. КИЗИМА ◽

Е.Г. РУДЕНКОВА

Keyword(s):

Frequency Spectrum ◽

Electromagnetic Compatibility ◽

Measurement Data ◽

Signal Propagation ◽

Radio Sources ◽

Electromagnetic Environment ◽

Radio Monitoring ◽

Radio Frequency Spectrum ◽

Radio Signals ◽

Problematic Situations

Рассматривается технология комплексного радиомониторинга излучений в заданной географической точке. Полученные результаты сопоставляются с разрешенными уровнями излучений. Технология направлена на решение задач оценки условий распространения и приема радиосигналов, планирования использования радиочастотного спектра (РЧС), выявления помех и других проблемных ситуаций, связанных с обеспечением электромагнитной совместимости ( ЭМС) действующих и перспективных радиосредств. The article describes the technology of complex radio monitoring of emissions from multiple radio sources. The measurement data are compared with the permitted emission levels. The application of the technology helps to assess the conditions for the propagation and reception of radio signals, planning the use of the radio frequency spectrum, identifying interference and other problematic situations related to electromagnetic compatibility of existing and promising radio facilities.

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ENVIRONMENT DENSITY OF A GIANT RADIO STRUCTURE FOR GALAXIES AND QUASARS WITH STEEP RADIO SPECTRA

Radio physics and radio astronomy ◽

10.15407/rpra26.02.165 ◽

2021 ◽

Vol 26 (2) ◽

pp. 165-172

Author(s):

A. P. Miroshnichenko ◽

Keyword(s):

Low Frequency ◽

Radio Spectrum ◽

Power Relation ◽

Cosmological Evolution ◽

Inverse Power ◽

Radio Sources ◽

Frequency Spectra ◽

Radio Structure ◽

Mean Values ◽

Index Value

Purpose: Estimate of the environment density of giant (with the linear size of about megaparsec) radio structures for galaxies and quasars with steep low-frequency spectra taken from the UTR-2 catalogue. Study of the cosmological evolution of environment density of giant radio sources. Determination of dependence of contribution of radio lobes into the emission of giant sources with respect to their environment density. Design/methodology/approach: We use the sample of sources from the UTR-2 catalogue of extragalactic sources to estimate the environment density for giant sources with steep low-frequency spectra. The selection criteria for the examined objects are the following: 1) the spectral index value is equal or larger than 1; 2) the fl ux density of emission at the frequency of 25 MHz is larger than 10 Jy; 3) the sample sources are optically identifi ed. The value of environment density of examined sources is obtained with the assumption of equality of source jet luminosity (at the synchrotron mechanism of radio emission) and its corresponding kinetic luminosity. The analysis of the estimates of environment densities is made for different classes of the sample objects (for galaxies and quasars with linear steep spectra and with break steep spectra). Findings: The estimates of environment density have been derived for giant radio structures formed by the jets of sources with steep spectrum from the UTR-2 catalogue. On the average, the environment density for the quasar structure (~ 10-28 g/sm3) is lesser than the one for the galaxies (~ 10-27 g/sm3 to ~ 10-26 g/sm3). The larger jet environment density is typical for the galaxies and quasars with the break steep spectra than for those with the linear steep spectra. The inverse power relation of the jet environment density and the source redshift (the cosmological evolution of the jet environment density) has been derived. The contribution of jet-related radio lobes into the emission of sources displays the inverse power relation for the environment density of the corresponding radio structures. Conclusions: The mean values of obtained estimates of environment density of giant jets of radio sources with steep low-frequency spectra indicate the lesser environment density of quasar jets than that for the galaxy jets. Giant radio sources with steep low-frequency spectrum (especially, with break steep spectrum) reveal considerable evolution of environment density of jets. The larger contribution of radio lobes (jets) into the emission of sources corresponds to the lesser environment density of sources taken from the UTR-2 catalogue. It can be due to propagation of jets (surrounded by radio lobes) from powerful radio sources to distances of about megaparsec, until the balance of source’s environment density and extragalactic environment density is reached. Key words: steep low-frequency radio spectrum; giant radio structure; jets; radio lobes; galaxies; quasars; environment density

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