Types Of Radio Sources Research Articles

Low-Noise Amplifier for Next-Generation Radio Astronomy Telescopes: Review of the State-of-the-Art Cryogenic LNAs in the Most Challenging Applications

Radio astronomy is a subfield of astronomy that explores the universe via radio signals up to a few terahertz. Since the first detection of radio signals from the Milky Way by Karl G. Jansky in 1932, various types of radio sources have been identified from our solar system, the local universe, extragalactic space, and all of the way back to the beginning of the universe.

ІНФОРМАЦІЙНА СИСТЕМА ПІДТРИМКИ ПРИЙНЯТТЯ РІШЕНЬ АВТОМАТИЗОВАНОЇ СИСТЕМИ УПРАВЛІННЯ РАДІОМОНІТОРИНГОМ

Armed aggression of the Russian Federation against Ukraine, loss of important industrial potentials, as Topaz state-owned holding company, which specialized in the development and production of complex radio engineering systems and complexes, including unique long-range radio intelligence systems and early warning of air defense systems, Kolchuga radio intelligence has given a significant impetus to the development of new approaches to conducting radio monitoring of the situation, as one of the main tion method of obtaining information. Such a complex type of technical activity as radio monitoring requires considerable effort to maintain it in readiness. The continuous provision of radio monitoring by the required number of highly qualified specialists with extensive experience in determining the type of radio source requires considerable effort to find and train them. Training of a specialist in this class takes at least 1-1.5 years and significant financial costs. Solving the scientific task of automating the process of detection and recognition is one of the priority areas for the development of radio monitoring. Modern radio monitoring character of functioning is divided into 2 groups: active, which allows to identify and detect non-functioning sources of radio emission; passive, allowing you to identify and recognize functioning radio sources. The basis for the operation of passive radio monitoring is the detection of signal transmitting messages (such as air traffic control signal) and the recognition of the parameters of the powerful signals of onboard, ship and ground radar stations. The informative nature of the radio source signal for radio monitoring facilities depends on how reliably the signal is detected and how accurately (accurately) its parameters are determined, which are useful for the intelligence of the message or value. Since signal monitoring always occurs against a background of all sorts of obstacles, the fact of detecting a signal, as well as errors in measuring signal parameters and message selection are always random. The article deals with the actual scientific task of automating the process of detection and recognition of radio sources, by developing a decision support system for determining the type of sources of radio radiation by its signal parameters in the interests of the state monitoring system, which provides guidance to the MTS-Kolchuga RTR operators the choice of the most likely variant of the decision that will reduce the qualification requirements for the operators, which will significantly reduce the financial and time costs for their preparation.

Constraining magnetic fields in galaxy clusters

AbstractMagnetic fields originate small-scale instabilities in the plasma of the intra-cluster medium, and may have a key role to understand particle acceleration mechanisms. Recent observations at low radio frequencies have revealed that synchrotron emission from galaxy clusters is more various and complicated than previously thought, and new types of radio sources have been observed. In the last decade, big steps forward have been done to constrain the magnetic field properties in clusters thanks to a combined approach of polarisation observations and numerical simulations that aim to reproduce Faraday Rotation measures of sources observed through the intra-cluster medium. In this contribution, I will review the results on magnetic fields reached in the last years, and I will discuss the assumptions that have been done so far in light of new results obtained from cosmological simulations. I will also discuss how the next generation of radio instruments, as the SKA, will help improving our knowledge of the magnetic field in the intra-cluster medium.

Numerical modelling of the lobes of radio galaxies in cluster environments – III. Powerful relativistic and non-relativistic jets

We present results from two suites of simulations of powerful radio galaxies in poor cluster environments, with a focus on the formation and evolution of the radio lobes. One suite of models uses relativistic hydrodynamics and the other relativistic magnetohydrodynamics; both are set up to cover a range of jet powers and velocities. The dynamics of the lobes are shown to be in good agreement with analytical models and with previous numerical models, confirming in the relativistic regime that the observed widths of radio lobes may be explained if they are driven by very light jets. The ratio of energy stored in the radio lobes to that put into the intracluster gas is seen to be the same regardless of jet power, jet velocity or simulation type, suggesting that we have a robust understanding of the work done on the ambient gas by this type of radio source. For the most powerful jets, we at times find magnetic field amplification by up to a factor of 2 in energy, but mostly the magnetic energy in the lobes is consistent with the magnetic energy injected. We confirm our earlier result that for jets with a toroidally injected magnetic field, the field in the lobes is predominantly aligned with the jet axis once the lobes are well developed, and that this leads to radio flux anisotropies of up to a factor of about two for mature sources. We reproduce the relationship between 151 MHz luminosity and jet power determined analytically in the literature.

NEW DETECTIONS OF RADIO MINIHALOS IN COOL CORES OF GALAXY CLUSTERS

Cool cores of some galaxy clusters exhibit faint radio "minihalos." Their origin is unclear, and their study has been limited by their small number. We undertook a systematic search for minihalos in a large sample of X-ray luminous clusters with high-quality radio data. In this article, we report four new minihalos (A 478, ZwCl 3146, RXJ 1532.9+3021, and A 2204) and five candidates found in the reanalyzed archival Very Large Array observations. The radio luminosities of our minihalos and candidates are in the range of 1023–25 W Hz−1 at 1.4 GHz, which is consistent with these types of radio sources. Their sizes (40–160 kpc in radius) are somewhat smaller than those of previously known minihalos. We combine our new detections with previously known minihalos, obtaining a total sample of 21 objects, and briefly compare the cluster radio properties to the average X-ray temperature and the total masses estimated from Planck. We find that nearly all clusters hosting minihalos are hot and massive. Beyond that, there is no clear correlation between the minihalo radio power and cluster temperature or mass (in contrast with the giant radio halos found in cluster mergers, whose radio luminosity correlates with the cluster mass). Chandra X-ray images indicate gas sloshing in the cool cores of most of our clusters, with minihalos contained within the sloshing regions in many of them. This supports the hypothesis that radio-emitting electrons are reaccelerated by sloshing. Advection of relativistic electrons by the sloshing gas may also play a role in the formation of the less extended minihalos.

AN EXAMINATION OF THE OPTICAL SUBSTRUCTURE OF GALAXY CLUSTERS HOSTING RADIO SOURCES

Using radio sources from the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey, and optical counterparts in the Sloan Digital Sky Survey (SDSS), we have identified a large number of galaxy clusters. The radio sources within these clusters are driven by active galactic nuclei, and our cluster samples include clusters with bent, and straight, double-lobed radio sources. We also included a single-radio-component comparison sample. We examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. We use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. We found no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.

Cluster analyses of gigahertz-peaked spectrum sources with self-organising maps

Context. Gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are among the smallest of active galactic nuclei currently believed to represent the earliest phases in the evolution of extragalactic radio sources. Recently there has been evidence of contamination by other types of radio sources among the GPS and HFP samples, but the confirmed GPS sources or HFPs also seem to form a very heterogeneous population. Aims. We study the statistical clustering of the GPS sources and the HFPs by taking as many source parameters as possible to find homogeneous groups among the sources. We expect the clustering to give us insight into the physical parameters that play a role in different source populations. Methods. We have collected a sample of 206 GPS sources and HFPs from the literature and gathered a massive database of various source properties, such as the redshift, the size, the polarization, the magnitudes, and the properties of the radio continuum. To visualize and to cluster these multidimensional data we used self-organising maps (SOM), which are neural networks trained by an unsupervised algorithm. We have classified the sources with an auxiliary classification to trace the locations of different types of radio continuum spectra on the map. Results. The sources form distinctive clusters on the map, which is supported by the accordant organisation of the non-numerical parameters not used in the analysis, such as the radio morphology and the optical identification. Our results confirm that the blazars contaminating the GPS and the HFP samples are physically different from the genuine GPS sources and HFPs, and they should be excluded from the samples. The genuine GPS sources form various clusters, which indicates the existence of different subpopulations, besides the expected galaxy-quasar dualism.

Relationship between X-shaped radio sources and double-double radio galaxies

AbstractBoth the X-shaped radio galaxies and double-double radio galaxies (DDRGs) are suggested in the literature to be due to the binary-accretion disk interaction or to the coalescence of SMBBHs. These models suggest some relationship between the two types of radio sources. In this paper, we collected data from literatures for two samples of X-shaped and double-double radio galaxies together with a control sample of FRII radio galaxies and statistically investigate their properties.We find that the wings of X-shaped radio galaxies and the outer and inner lobes of DDRGs tend to be perpendicular to the major axis of the host galaxy (or dust structures), while the active lobes orient randomly. Both X-shaped and double-double radio galaxies are low luminous FRII or FRI/FRII transitional radio sources with the similar dimensionless accretion rate ṁ ∼ 0.01, which is about the transitional accretion rate given in the literature.All the statistic results can be reconciled if there is an evolutionary relationship between X-shaped and double-double radio galaxies, in the sense that X-shaped radio galaxies may be due to the interaction of active SMBBHs and accretion disk and DDRGs due to the removal of inner disk region and the coalescence of SMBBHs.

Discovery of a High-Redshift ([CLC][ITAL]z[/ITAL][/CLC] = 0.96) Cluster of Galaxies Using a FIRST Survey Wide-Angle–Tailed Radio Source

Using a combination of near-infrared and optical photometry, along with multiobject spectroscopy, we have confirmed the existence of a high-redshift cluster of galaxies at z = 0.96. The cluster was found using a wide-angle–tailed radio source selected from the VLA FIRST survey as a cluster signpost. These types of radio sources are often found in clusters and are thought to attain their C-shaped morphologies from the relative motion between the radio source host galaxy and the intracluster medium. We present optical/near-infrared color-magnitude diagrams that show a concentration of cluster galaxies in color space. We also include spectroscopic results obtained from the Keck II Low Resolution Imaging Spectrometer. Ten galaxies are confirmed at the cluster redshift, with a line-of-sight velocity dispersion of σ∥ = 530 km s-1, typical of an Abell richness class 0 cluster. Using data from the ROSAT public archive, we limit the X-ray luminosity for the cluster to LX,bol ≲ 3 × 1044 ergs s-1, consistent with the value expected from the LX-σ relation.

Radio Properties of GPS and CSS Sources: Galaxies versus Quasars

AbstractOn the basis of the different radio properties (especially different radio morphologies) between GPS galaxies and GPS quasars, I suggest that GPS galaxies are a more homogeneous class mainly consisting of compact symmetric objects, while the majority of GPS quasars are an intrinsically different type of radio source, similar to the common flat spectrum radio sources. For CSS radio sources the difference between galaxies and quasars is less evident. This is interpreted as a bias correlated with size: samples of smaller objects are more likely to be contaminated by unrelated objects. This is consistent also with the high percentage of blazar/quasar objects present in a sample of the even smaller HFP radio sources.

Correlation between the Directions of the Magnetic Fields and Major Axes of Extragalactic Radio Sources

The distribution of relative position angles between the integrated intrinsic polarization (perpendicular to the direction of the intrinsic magnetic field) and the major axis of an extragalactic radio source were studied for different types of radio sources. Data for 280 extragalactic radio sources were used and it was found that there are large differences in the relative orientation of different types of radio sources. The directions of the intrinsic integrated magnetic fields correlate with the major radio axes of more elongated radio sources (K > 2.5, where K is the ratio of lengths of the major and minor axes of the radio images) and for radio sources of type FR II, whereas for less elongated objects (K < 2.5) and for radio sources of type FR I the magnetic fields do not correlate at all with the radio axes. An alternative mechanism for the formation of a radio galaxy from relativistic plasma ejected from the central part of an optical galaxy and moving in its large-scale, dipole magnetic field may be a theoretical basis for classification with respect to the elongation parameter K of the radio image.

Different Types of Radio Sources and Possible Evolution of Radio Galaxies

Extragalactic radio sources have been studied for many years, but it is still unclear how they are formed and evolve. The sizes of the most powerful radio emitters in the Universe vary from less than one parsec to more than 1 Mpc. This large range of sizes has been interpreted as evidence for the evolution of the linear sizes of radio structure (e.g., O’Dea and Baum, 1997). A crucial element in the study of their evolution is the identification of the young compact counterparts of “old” FRI/FRII extended objects. Good candidates for young radio sources are those with peaked spectra (Gigahertz Peaked Spectrum - GPS and Compact Steep Spectrum - CSS, e.g., O’Dea 1998). Radio sources are presumably born in the very compact GPS phase, then they expand beyond 1 kpc into the CSS regime and finally, they reach a size of 20 kpc, and afterwards evolve into large-scale radio sources (young scenario, e.g., O’Dea 1998). Alternatively, GPS sources may be compact because a particularly dense environment prevents them from growing larger (old scenario, e.g., O’Dea 1998). In either scenario, the radio source host galaxy determines the time evolution of the radio structure. By studying the optical environments and host galaxies we hope to obtain clues to the evolution of the radio sources. Similarities or differences in host galaxy properties over a range of radio source types and sizes enable us to investigate possible differences or similarities of the radio size class as a whole.

On the orientation of magnetic fields in extragalactic radiosources

Abstract We studied the relative orientation of position angles of the integrated intrinsic radio polarization (perpendicular to the intrinsic direction of the magnetic field) and the major axes of extragalactic radiosources for different types of radiosources, classified by their elongation (Andreasyan and Sol, 1999) and also according to their Fanaroff–Riley (FR) type. We considered data for about 300 extragalactic radiosources and found that there are large differences in relative orientations for different types of radiosources. The directions of integrated intrinsic magnetic fields are correlated with major radio axes for the more elongated sources (with a ratio of major to minor radio axes larger than 2.5) and for FRII radiosources, while they appear not correlated with radio axes for stocky and for FRI-type radiosources.

Detection of prolonged, extremely faint decimeter bursts on the sun

We report the detection of long-lived sources of radio bursts accompanied by polarized background emission in solar active regions. Both types of radio sources were detected at several decimeter wavelengths in observations on the RATAN-600 radio telescope in one-dimensional scans in intensity and circular polarization with a sensitivity of about 5–10 Jy. The degree of polarization is from 70 to 100%. The microburst and background sources exist for several days and appear at sites of prolonged energy release. The typical duration of an individual microburst is about 1–2 s, and the time interval between microbursts is about 3–5 s. A negative microburst frequency drift of about 100 MHz/s or more is also observed. Some interpretations of the microburst and background sources are discussed. The most probable microburst model involves the generation of radio emission via the plasma mechanism, with the upward propagation of fast electrons above an active region. In this case, the required energy of the Langmuir waves is 2×10−8 of the heat energy of the background plasma. Microbursts appear in different places in an active region. New methods for determining the magnetic-field intensity in the regions of generation of the decimeter-wavelength emission are proposed.

The Detection of a Large, Powerful FR I Radio Galaxy in a Spiral Host

We report the detection of a FR I-like radio galaxy with a total extent of more than 200 kpc in a disk-dominated host. Traditional wisdom maintains that these types of radio sources are only found in elliptical hosts. We confirm the optical classification of this galaxy from deep, multicolor optical/NIR imaging and the detection of a spiral arm, an optical rotation curve, and line-ratios in the disk consistent with HII regions and star formation. At 20cm, we find a 36kpc knotty, jet extending into the southern lobe. At 3.6cm we detect a kpc-scale jet with the same position angle. With the exception of the radio source, this galaxy appears to be a fairly ordinary, dusty, star-forming spiral, with some evidence for a weak, obscured, AGN.

Interaction versus radio source generation - The properties of radio jet parent galaxies

This paper presents the first systematic survey at optical wavelengths of galaxies with detected radio jets using CCD imaging. About 50 percent of the sample of low-redshift galaxies with radio jets have a large nearby companion and/or show peculiar optical morphology not detected in isolated ellipticals. Forty-five percent of the objects have a companion galaxy at a distance shorter than 20 kpc. The multicomponent galaxies in the sample form a very homogeneous group with little gas and dust, while the isolated galaxies have more heterogeneous radio properties, with large amounts of gas and warm dust in a large fraction of these galaxies. Intrinsic differences between the multicomponent galaxies and the isolated ones are explained in terms of a different parent galaxy and interaction processes. It is concluded that, at least among galaxies with radio jets, the amount of gas available and the interactions could control the energy generation, producing a very well-defined type of radio source. 48 refs.

Pulsed Radio Sources May Be Neutron Stars

At least three radio observatories have recently reported an entirely new type of radio source that emits pulses with extremely stable repetition frequency and apparently random amplitude. It is tempting to identify these sources as neutron stars, postulated but not yet observed, or as white dwarf stars. Observations with optical telescopes are under way to look for visible radiation from these sources and to see whether the same pulsation occurs.