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Journal articles on the topic 'Radio sources (astronomy)'

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Author: Grafiati

Published: 4 June 2021

Last updated: 1 August 2024

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1

Fan, J. H., Y. Huang, Y. Liu, Y. Gao, T. X. Hua, and J. H. Yang. "Brightness temperature for radio sources." Proceedings of the International Astronomical Union 3, S245 (July 2007): 245–46. http://dx.doi.org/10.1017/s1743921308017791.

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AbstractIn this work, using the database of the university of Michigan Radio Astronomy Observatory (UMRAO), we determined the brightness temperatures, TB for a sample of 167 radio sources. The value of TB is in a range of log TB(K) = 10.46 to 20.08, which suggested that the boosting factors are in a range of δ = 0.41 to 41.26.

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2

Liu, Y., J. H. Fan, and H. G. Wang. "Radio variability properties for sources at multi-frequencies." Proceedings of the International Astronomical Union 3, S245 (July 2007): 251–52. http://dx.doi.org/10.1017/s1743921308017821.

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AbstractUsing three radio databases of the university of Michigan Radio Astronomy Observatory (UMRAO), the National Radio Astronomy Observatory (NRAO), and the Metsähovi Observatory, we analyzed the radio light curves by the power spectral analysis and CLEANest method in search for possible periodicity. Multiple periods are found in some sources at multi-frequencies. We adopted the wavelets for period analysis of unevenly sampled time series to search for the evolution of the parameters (period, amplitude) of possible periodicities. Some possible variation of these parameters are found.

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3

Periola, Ayodele Abiola, and Olabisi Emmanuel Falowo. "Intelligent Cognitive Radio Models for Enhancing Future Radio Astronomy Observations." Advances in Astronomy 2016 (2016): 1–15. http://dx.doi.org/10.1155/2016/5408403.

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Radio astronomy organisations desire to optimise the terrestrial radio astronomy observations by mitigating against interference and enhancing angular resolution. Ground telescopes (GTs) experience interference from intersatellite links (ISLs). Astronomy source radio signals received by GTs are analysed at the high performance computing (HPC) infrastructure. Furthermore, observation limitation conditions prevent GTs from conducting radio astronomy observations all the time, thereby causing low HPC utilisation. This paper proposes mechanisms that protect GTs from ISL interference without permanent prevention of ISL data transmission and enhance angular resolution. The ISL transmits data by taking advantage of similarities in the sequence of observed astronomy sources to increase ISL connection duration. In addition, the paper proposes a mechanism that enhances angular resolution by using reconfigurable earth stations. Furthermore, the paper presents the opportunistic computing scheme (OCS) to enhance HPC utilisation. OCS enables the underutilised HPC to be used to train learning algorithms of a cognitive base station. The performances of the three mechanisms are evaluated. Simulations show that the proposed mechanisms protect GTs from ISL interference, enhance angular resolution, and improve HPC utilisation.

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4

RYABOV, M. I., and L. I. SOBITNIAK. "Tidal phenomena in the Earth’s upper atmosphere." Astronomical and Astrophysical Transactions, Volume 33, Numéro 1 (July 1, 2022): 37–44. http://dx.doi.org/10.17184/eac.6468.

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From 1987 to the present, the radio flux of powerful galactic and extragalactic radio sources is monitored at decameter waves at the URAN-4 radio telescope of the Odessa Observatory of the Radio Astronomy Institute of the National Academy of Sciences of Ukraine. The work is based on revealing the nature of unusual records of radio sources that were not associated with the presence of interference in the decameter radio band. Changes of fluxes of radiation sources at decameter waves are determined by the condition of an ionosphere as a result of variation in space weather and tidal events. When radio sources are observed through a tidal wave, a “plasma lens” effect is realized in the ionosphere. Depending on the position of the radio source relative to the tidal wave, the radiation wave front is sought. As a result, various effects are realized: strong focusing, intense flickering or “blurred” recording of the radio source. This effect was originally reflected in earlier works [1]. In this paper the analog records of radio sources (1987-1990) and digital (1998-2004) are considered and various tidal effects were clarified. Based on the results of measurements, the angular dimensions of the tidal wave, reaching 60 degrees, were determined. Radio astronomy observations in the decameter range at the URAN-4 radio telescope are an effective method for studying tidal phenomena in the Earth's upper atmosphere.

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5

Jones, D. L., and K. W. Weiler. "Low Frequency Radio Astronomy from the Moon." Highlights of Astronomy 11, no. 2 (1998): 988–89. http://dx.doi.org/10.1017/s1539299600019389.

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AbstractThe radio sky at frequencies of several MHz and below is essentially unexplored with high angular resolution due to refraction and opacity in the Earth’s ionosphere. An interferometer array in space providing arcminute resolution images would allow a wide range of problems in solar, planetary, galactic, and extragalactic astronomy to be attacked. These include the evolution of solar and planetary radio bursts, interplanetary and interstellar scintillation, the distribution of low energy cosmic rays and diffuse ionized hydrogen in our galaxy, the determination of spectral turnover frequencies and magnetic field strengths in galactic and extragalactic radio sources, searches for “fossil” radio galaxies which are no longer detectable by high frequency surveys, and searches for new sources of coherent radio emission. In addition, it is likely that unexpected objects and emission processes will be discovered by such an instrument, as has often happened when high resolution observations first become possible in a new spectral region. The Moon can provide shielding from terrestrial interference (and from the Sun half of the time) and consequently the lunar farside surface offers an ideal site of a low frequency radio array.

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6

Blundell, K. M., N. E. Kassim, and R. A. Perley. "3C Radio Sources as They've Never Been Seen Before." Symposium - International Astronomical Union 199 (2002): 189–92. http://dx.doi.org/10.1017/s0074180900168846.

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Low-radio-frequency observations played a remarkable role in the early days of radio astronomy; however, in the subsequent three or four decades their usefulness has largely been in terms of the finding-frequency of surveys. Recent technical innovation at the VLA has meant that spatially well-resolved imaging at low frequencies is now possible. Such imaging is essential to understanding the relationship between the hotspot and lobe emission in classical double radio sources, for example. We here present new images of 3C radio sources at 74 MHz and 330 MHz and discuss their implications.

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7

Rieu, Nguyen Quang. "Simple Instruments in Radio Astronomy." Transactions of the International Astronomical Union 24, no. 3 (2001): 255–65. http://dx.doi.org/10.1017/s0251107x00000924.

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AbstractRadio astronomy has a major role in the study of the universe. The spiral structure of our Galaxy and the cosmic background radiation were first detected, and the dense component of interstellar gas is studied, at radio wavelengths. COBE revealed very weak temperature fluctuations in the microwave background, considered to be the seeds of galaxies and clusters of galaxies. Most electromagnetic radiation from outer space is absorbed or reflected by the Earth’s atmosphere, except in two narrow spectral windows: the visible-near-infrared and the radio, which are nearly transparent. Centimetre and longer radio waves propagate almost freely in space; observations of them are practically independent of weather. Turbulence in our atmosphere does not distort the wavefront, which simplifies the building of radio telescopes, because no devices are needed to correct for it. Observations at these wavelengths can be made in high atmospheric humidity, or where the sky is not clear enough for optical telescopes.Simple instruments operating at radio wavelengths can be built at low cost in tropical countries, to teach students and to familiarize them with radio astronomy. We describe a two-antennae radio interferometer and a single-dish radio telescope operating at centimetre wavelengths. The Sun and strong synchrotron radio-sources, like Cassiopeia A and Cygnus A, are potential targets.

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8

GRAHAM - SMITH, FRANCIS. "The big ears of radio astronomy." European Review 10, no. 2 (May 2002): 285–300. http://dx.doi.org/10.1017/s1062798702000200.

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The special value of radio astronomy lies in the probing of extreme conditions in the universe, including the highest energies and the lowest temperatures. Radio waves can penetrate clouds of gas and dust to reveal objects in the universe and, in particular, in our Galaxy that cannot be seen by visible light. To achieve the highest resolution, radio telescopes in widely separate parts of our globe combine their reception to produce a synthesized image. This is a splendid example of international collaboration. Among the images visualized are pulsars, derived from the remnants of supernovae explosions, and quasar sources powered by black holes.

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9

Herranz, Diego, Francisco Argüeso, and Pedro Carvalho. "Compact Source Detection in Multichannel Microwave Surveys: From SZ Clusters to Polarized Sources." Advances in Astronomy 2012 (2012): 1–14. http://dx.doi.org/10.1155/2012/410965.

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We describe the state-of-the art status of multifrequency detection techniques for compact sources in microwave astronomy. From the simplest cases where the spectral behaviour is well known (i.e., thermal SZ clusters) to the more complex cases where there is little a priori information (i.e., polarized radio sources) we will review the main advances and the most recent results in the detection problem.

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10

Jessner, A. "Industrial interference and radio astronomy." Advances in Radio Science 11 (July 4, 2013): 251–58. http://dx.doi.org/10.5194/ars-11-251-2013.

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Abstract. The interferer – victim scenario is described for the case of industrial interference affecting radio astronomical observatories. The sensitivity of radio astronomical receivers and their interference limits are outlined. EMC above 30 MHz is a serious problem for Radio Astronomy. Interferer (CISPR) and victim (ITU-R RA 769) standards are not harmonised. The emissions from the interferer and their spectral characteristics are not defined sufficiently well by CISPR standards. The required minimum coupling losses (MCL) between an industrial device and radio astronomical antenna depends on device properties but is shown to exceed 140 dB in most cases. Spatial separation of a few km is insufficient on its own, the terrain must shield > 30–40 dB, additional mitigations such as extra shielding or suppression of high frequency emissions may be necessary. A case by case compatibility analysis and tailored EMC measures are required for individual installations. Aggregation of many weak rfi emitters can become serious problem. If deployment densities are high enough, the emission constraints can even exceed those for a single interferer at a short distance from the radio observatory. Compatibility studies must account not only for the single interferer but also for many widely distributed interference sources.

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11

L Greenstein, Jesse. "The Early Years of Radio Astronomy at Caltech." Australian Journal of Physics 47, no. 5 (1994): 555. http://dx.doi.org/10.1071/ph940555.

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By the early 1950s astronomy in the United States was under pressure to embrace radio astronomy, which was being developed largely outside the USA. Much of the motivation derived from the need for accurate radio source positions, so that optical telescopes like the California Institute of Technology's giant Palomar Telescope and the nearby Mt Wilson Telescope could identify these sources with astronomical objects. To lead Caltech's move into radio astronomy its president, Lee DuB ridge, realised that he needed a leader from a country with more practical experience than the USA. He turned to his wartime friend E. G. 'Taffy' Bowen, chief of the CSIRO's Radiophysics Laboratory in Sydney, who 'loaned' him John Bolton. John stayed at Caltech for a bare five years, but it was a time of inspired guidance that helped to secure a place in radio astronomy, not only for Caltech, but for the USA.

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12

Orchiston, Wayne. "John Bolton, Discrete Sources, and the New Zealand Field-trip of 1948." Australian Journal of Physics 47, no. 5 (1994): 541. http://dx.doi.org/10.1071/ph940541.

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The field-trip to New. Zealand by John Bolton and Gordon Stanley in 1948 was a crucial step in discovering the nature of discrete radio sources. This paper describes the circumstances surrounding the field-trip and also looks at other investigations in radio astronomy in New Zealand at that time.

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13

Fan, J. H., Y. Liu, Y. H. Yuan, T. X. Hua, H. G. Wang, Y. X. Wang, J. H. Yang, et al. "Radio variability properties for radio sources." Astronomy & Astrophysics 462, no. 2 (November 13, 2006): 547–52. http://dx.doi.org/10.1051/0004-6361:20054775.

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14

Condon, J. J. "Radio Surveys." Symposium - International Astronomical Union 179 (1998): 19–25. http://dx.doi.org/10.1017/s0074180900128177.

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Radio surveys have an important role in astronomy, one that has changed with technology and scientific requirements. Most objects studied by radio astronomers today are the unexpected discoveries of early surveys. The survey “discovery” phase began with Jansky's detection of Galactic radio emission and Reber's 160 MHz maps showing that this emission is non-thermal. Surveys made just after World War II revealed strong discrete sources which were later identified with supernova remnants, radio galaxies, and quasars. Pulsars were discovered during a sky survey for scintillating sources. BL Lac objects were recognized in early high-frequency surveys. The first gravitationally lensed quasar appeared in the extensive Jodrell Bank 960 MHz survey, and the first measurement of gravitational radiation came from the binary pulsar serendipidously found in a pulsar survey.

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15

Longair, Malcolm S. "Antony Hewish. 11 May 1924—13 September 2021." Biographical Memoirs of Fellows of the Royal Society 72 (March 16, 2022): 173–96. http://dx.doi.org/10.1098/rsbm.2021.0045.

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Antony (Tony) Hewish was a pioneer radio astronomer who will always be remembered as the leader of the team in 1967 that discovered the pulsars, which proved to be rapidly rotating, magnetized neutron stars. The discovery resulted from Tony's programme of systematic all-sky surveys to detect the scintillation, or flickering, of small angular diameter radio sources due to electron density fluctuations in the solar wind flowing out from the Sun. The large low-frequency 4.5-acre array was designed by Tony to find radio quasars, which often display radio scintillations, to estimate the angular sizes of the sources and to study the physics of the interplanetary medium. In the course of commissioning the telescope, his research student, Jocelyn Bell (Jocelyn Bell Burnell, FRS 2003), noted a strange 100% scintillating source unlike anything seen before. Tony and the team soon established that this source was a pulsating radio source, Jocelyn first observing the pulsations with period 1.33 s in November 1967. The discovery paved the way for the rapid development of high energy astrophysics and an appreciation that general relativity plays a key role in the stability of neutron stars. Tony's contributions spanned a very wide range of pioneering studies in the new discipline of radio astronomy, including telescope and electronic design, cosmological studies of distant radio sources and the physics of the ionospheric, interplanetary and interstellar plasmas. He was awarded the 1974 Nobel Prize in physics for ‘his decisive role in the discovery of pulsars’.

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16

Swarup, G., and C. R. Subramanya. "Preserving Radio Astronomy in Developing Nations." Symposium - International Astronomical Union 196 (2001): 270. http://dx.doi.org/10.1017/s0074180900164198.

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Due to the very weak nature of signals from cosmic radio sources, the sensitivity of a radio telescope and receiver is about 40–60 dB higher than those of communications receivers. Hence, radio telescopes are generally located in relatively radio-quiet locations and operate in frequency bands that are protected against radio interference through frequency planning by national governments. Taking advantage of the much lower degree of radio interference in developing countries and the relatively labour-intensive nature of metre-wave radio telescopes, several such radio telescopes have been built and are planned in Argentina, Brazil, China, India, Mauritius and South Africa. Radio telescopes operating at cm-wavelengths are also planned in Egypt and Mexico.A particularly severe problem arises for the radio astronomy service and other passive services below 2 GHz from the possibility of unacceptable emissions from satellites in unwanted bands (out-of-band and spurious emissions), due to the specific modulation schemes used in satellite transmitters. It is noted that this can be circumvented within the existing technologies if the satellite transmitters employ suitable bit-shaping or filtering techniques or use modulation schemes like Gaussian-filtered Minimum-Shift Keying (GMSK) which produce very little out-of-band emission. Although radio astronomy started in the western world at low frequencies, much low frequency radio astronomy is now planned or operational in developing countries. In order to protect the interests of these and other passive services within developing nations, it is important that suitable regulations be recommended to UNISPACE-III to provide appropriate protection.

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17

Norris, Ray P. "Astroinformatics Challenges from Next-generation Radio Continuum Surveys." Proceedings of the International Astronomical Union 12, S325 (October 2016): 103–13. http://dx.doi.org/10.1017/s1743921316012825.

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AbstractThe tens of millions of radio sources to be detected with next-generation surveys pose new challenges, quite apart from the obvious ones of processing speed and data volumes. For example, existing algorithms are inadequate for source extraction or cross-matching radio and optical/IR sources, and a new generation of algorithms are needed using machine learning and other techniques. The large numbers of sources enable new ways of testing astrophysical models, using a variety of “large-n astronomy” techniques such as statistical redshifts. Furthermore, while unexpected discoveries account for some of the most significant discoveries in astronomy, it will be difficult to discover the unexpected in large volumes of data, unless specific software is developed to mine the data for the unexpected.

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18

Ellingson, S. W., and R. M. Buehrer. "Coherent Time-domain Canceling of Interference for Radio Astronomy." Publications of the Astronomical Society of the Pacific 134, no. 1041 (November 1, 2022): 114505. http://dx.doi.org/10.1088/1538-3873/ac9b92.

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Abstract Radio astronomy is vulnerable to interference from a variety of anthropogenic sources. Among the many strategies for mitigation of this interference is coherent time-domain canceling (CTC), which ideally allows one to “look through” interference, as opposed to avoiding the interference or deleting the afflicted data. However, CTC is difficult to implement, not well understood, and at present this strategy is not in regular use at any major radio telescope. This paper presents a review of CTC including a new comprehensive study of the capabilities and limitations of CTC using metrics relevant to radio astronomy, including fraction of interference power removed and increase in noise. This work is motivated by the emergence of a new generation of communications systems which pose a significantly increased threat to radio astronomy and which may overwhelm mitigation methods now in place.

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19

Batty, Michael J., John D. Bunton, David R. Brown, Julian B. Corben, and Graeme L. White. "Astronomy with the Fleurs Six-Dish Array." Publications of the Astronomical Society of Australia 6, no. 3 (1986): 346–51. http://dx.doi.org/10.1017/s1323358000027041.

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AbstractOperation of the six 13.7 m antennas of the Fleurs synthesis telescope as a sub-array has provided a new and surprisingly versatile astronomical tool. With enhanced reliability and fully automated operation, unattended observing over several days is possible. Interleaved ‘multiple-snapshot’ observations of many fields per day can be made.The array has shown itself to be particularly suitable for the measurement of precision (a few arcsecond) positions for the optical identification of a large number of radio sources, a survey of compact sources and the monitoring of the activity of several radio stars over periods of weeks. At present a program of recalibration is under way to improve the positional accuracy and dynamic range of the instrument.

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Sadler, Elaine M., V. J. McIntyre, C. A. Jackson, and R. D. Cannon. "Radio Sources in the 2dF Galaxy Redshift Survey I. Radio Source Populations." Publications of the Astronomical Society of Australia 16, no. 3 (1999): 247–56. http://dx.doi.org/10.1071/as99247.

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AbstractWe present the first results from a study of the radio continuum properties of galaxies in the 2dF Galaxy Redshift Survey, (2dFGRS) based on thirty 2dF fields covering a total area of about 100 deg2. About 1·5% of galaxies with bJ < 19·4 mag. are detected as radio continuum sources in the NRAO VLA Sky Survey (NVSS). Of these, roughly 40% are star-forming galaxies and 60% are active galaxies (mostly low-power radio galaxies and a few Seyferts). The combination of 2dFGRS and NVSS will eventually yield a homogeneous set of around 4000 radio-galaxy spectra, which will be a powerful tool for studying the distribution and evolution of both AGN and starburst galaxies out to z ∼ 0·3.

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21

Zhang, Lixia, Junhui Fan, and Jingtian Zhu. "Radio loudness and classification for radio sources." Publications of the Astronomical Society of Japan 73, no. 2 (January 30, 2021): 313–25. http://dx.doi.org/10.1093/pasj/psaa122.

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Abstract The extragalactic radio sources are divided into two subclasses (radio-loud and radio-quiet sources) in the literature using radio loudness (R), which is defined as the ratio of radio emission to optical emission, but the boundary R-value separating the two classes is different in various sources. In this work, a sample of 2419 objects from the 13th catalog of quasars and active nuclei is used to build a boundary for the two subclasses. To do so, we compiled the radio and optical data, calculated their radio and optical indexes, made K-correction, obtained the radio loudness, and adopted a Bayesian analysis method to the logarithm of radio loudness for classification. We also investigated the correlations of radio loudness with radio/optical luminosities. Our main conclusions are summarized as follows: (1) The distribution of the logarithm of radio loudness (log R) is bimodal, the sources with log R < 1.26 are classified as radio-quiet sources, and those with log R > 1.26 are classified as radio-loud ones from the Bayesian analysis method. (2) The average radio-optical effective spectral index of radio-quiet sources is 〈αRO〉 = 0.05, while that of radio-loud sources is 〈αRO〉 = 0.55. (3) There are positive correlations between radio luminosity and radio loudness for both radio-loud sources and radio-quiet sources. (4) A dividing line of separating the distribution of the clusters on the diagram of radio loudness against radio luminosity was obtained statistically to set the boundary between radio-loud sources and radio-quiet sources, with an accuracy of $99.73\%$ based on the classification result from the Bayesian analysis method.

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22

Afanasiev, V. L., S. N. Dodonov, A. V. Moiseev, V. Chavushyan, R. Mujica, Y. Juarez, A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev. "Optical and radio studies of radio sources." Astronomy Letters 29, no. 9 (September 2003): 579–86. http://dx.doi.org/10.1134/1.1607495.

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23

Kalinichenko, M. M., N. V. Kuhai, O. O. Konovalenko, A. I. Brazhenko, I. M. Bubnov, S. M. Yerin, H. O. Rucker, et al. "INVESTIGATIONS OF COSMIC SOURCES RADIOEMISSION SCINTILLATIONS DUE TO INTERPLANETARY PLASMA IRREGULARITIES AT THE INSTITUTE OF RADIO ASTRONOMY, NAS UKRAINE." Radio physics and radio astronomy 26, no. 2 (June 23, 2021): 148–64. http://dx.doi.org/10.15407/rpra26.02.148.

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Purpose: Review of investigations of cosmic sources radioemission scintillations due to interplanetary plasma irregularities made at the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, from the first observations in the mid-70s until now. Design/methodology/approach: In the course of preparation of this paper, the authors have reviewed, analyzed and summarized the information being published in the home and foreign publications, and reported at scientific conferences. Findings: The investigations of the interplanetary scintillations carried out at the Institute of Radio Astronomy, NAS Ukraine have been reviewed. A retrospective discussion has been made on how in the course of these researches the knowledge about the basic parameters of interplanetary scintillations in the decameter wavelength range, as well as that on the important parameters of the solar wind and its structure, have been obtained. Also, various methods of processing and analysis of experimental data were offered, and new means for receiving cosmic radiation were created. The place and importance of the discussed researches for the world science are shown. Conclusions: Over the years since the beginning of the research, the think tank of the Department of Low-Frequency Radio Astronomy of the Institute of Radio Astronomy, NAS Ukraine has obtained a number of new relevant results, which bring Ukraine into the cohort of world centers of interplanetary scintillation researches. The construction of a new GURT radio telescope, among other things, creates new prospects for the development of this relevant line of investigation. Key words: interplanetary scintillations; decameter wavelength range; solar wind; solar wind stream structure; coronal mass ejection

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24

Mills, B. Y. "Astronomy at the Molonglo Radio Observatory." Publications of the Astronomical Society of Australia 6, no. 1 (1985): 72–78. http://dx.doi.org/10.1017/s1323358000026722.

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AbstractSince its commissioning in 1981 the Molonglo Observatory Synthesis Telescope has been used by the Astrophysics Department in the University of Sydney for many astronomical programs. These include completed surveys of both Magellanic Clouds made to study their SNR and HII content. The SNR work is essentially complete with 55 remnants identified and firm indications that the previously assumed evolution of a typical SNR (if such exists!) is incompatible with observation. The cataloguing and analysis of the HII regions and planetary nebulae data is complete in the SMC but barely started in the LMC. Other observing programs include the mapping of southern radio and ‘normal’, galaxies, the study of variable sources, ‘deep mapping’ of a selection of far southern fields for cosmological studies, studies of mass loss stars, the Galactic centre and a general survey of a strip along the Galactic plane as a long term program. In addition, advantage has been taken of the ‘real-time’ beams for pulsar studies and for the development of a ‘transient event recorder’ to permit a search for pulsed or other rapidly varying phenomena during normal map synthesis. Some of these programs have been completed but the majority are still in progress.

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25

Westerlund, S., C. Harris, and T. Westmeier. "Assessing the Accuracy of Radio Astronomy Source-Finding Algorithms." Publications of the Astronomical Society of Australia 29, no. 3 (2012): 301–8. http://dx.doi.org/10.1071/as11049.

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AbstractThis work presents a method for determining the accuracy of a source finder algorithm for spectral line radio astronomy data and the Source Finder Accuracy Evaluator (SFAE), a program that implements this method. The accuracy of a source finder is defined in terms of its completeness, reliability, and accuracy of the parameterisation of the sources that were found. These values are calculated by executing the source finder on an image with a known source catalogue, then comparing the output of the source finder to the known catalogue. The intended uses of SFAE include determining the most accurate source finders for use in a survey, determining the types of radio sources a particular source finder is capable of accurately locating, and identifying optimum parameters and areas of improvement for these algorithms. This paper demonstrates a sample of accuracy information that can be obtained through this method, using a simulated ASKAP data cube and the duchamp source finder.

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26

Cassaro, Pietro. "Hints of radio sources evolution." Proceedings of the International Astronomical Union 14, S342 (May 2018): 237–38. http://dx.doi.org/10.1017/s1743921318007196.

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AbstractAn understanding of the mechanisms that regulate the Active Galactic Nuclei passes through the study of their early life stages, observable in Compact Symmetric Objects. To this purpose, a study was carried out on two compact radio sources, based on data from the VLBA archive at different times and frequencies. The results are compatible with an intermediate scenario between the two main theories about these objects: frustration and youth.

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27

Malumian, V. H. "GPS and CSS radio sources." Astrophysics 52, no. 4 (October 2009): 494–500. http://dx.doi.org/10.1007/s10511-009-9084-2.

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28

Ovcharova, I. N., and R. B. Shatsova. "Infrared sources in radio loops." Astrophysics 43, no. 2 (April 2000): 182–90. http://dx.doi.org/10.1007/bf02683982.

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29

Wall, JV. "Populations of Extragalactic Radio Sources." Australian Journal of Physics 47, no. 5 (1994): 625. http://dx.doi.org/10.1071/ph940625.

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In the late 1950s and early 1960s, radio sky surveys were the centre of an intense and public debate-Big-Bang versus Steady-State cosmology-the arguments revolving about source counts and statistical interpretations in the face of instrumental complications. The 1965 discovery of the microwave background took the fire from the debate, but left the momentum in place for large-area radio surveys at different frequencies, and for extensive identification/redshift-measurement programs. By the 1970s the data enabled us to start disentangling the different populations of extragalactic radio sources. We could refine our taxonomy, and we could view the possibility of delineating individual cosmic histories and evolutions. We could at least describe a goal to elucidate the birth-life-death cycles of the objects involved [quasi-stellar objects (QSOs) and radio galaxies: together the 'active galactic nuclei' (AGNs)] whose unaccountably prodigious energies somehow produce the beautifully aligned radio structures with which we are now familiar. One part of John Bolton's vision to see how distorted a view of the AGN universe the original long-wavelength surveys provided. One legacy is thus the 'short-wavelength survey' for extragalactic radio sources, which has done so much to balance our picture of the radio sky. And indeed the legacy continues in the form of the immense sky surveys at present under way, complete with their sub-industries of radio-positioning and identification. From these, yet further results are emerging on spatial distribution and the skeleton structure of the universe. It is the purpose of this paper to outline something of this current view of the populations, their differences, similarities and unifying concepts.

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30

Sturrock, P. A. "Extragalactic variable radio sources." Astrophysical Journal 293 (June 1985): 52. http://dx.doi.org/10.1086/163213.

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31

Kovalev, Y. Y., A. P. Lobanov, A. B. Pushkarev, and J. A. Zensus. "Opacity in compact extragalactic radio sources and its effect on radio-optical reference frame alignment." Proceedings of the International Astronomical Union 3, S248 (October 2007): 348–51. http://dx.doi.org/10.1017/s1743921308019546.

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AbstractAccurate alignment of the radio and optical celestial reference frames requires detailed understanding of physical factors that may cause offsets between the positions of the same object measured in different spectral bands. Opacity in compact extragalactic jets (due to synchrotron self-absorption and external free-free absorption) is one of the key physical phenomena producing such an offset, and this effect is well-known in radio astronomy (“core shift”). We have measured the core shifts in a sample of 29 bright compact extragalactic radio sources observed by Very Long Baseline Interferometry (VLBI) at 2.3 and 8.6 GHz. We report the results of these measurements and estimate that the average shift between radio and optical positions of distant quasars could be of the order of 0.1--0.2 mas. This shift exceeds the expected positional accuracy of Gaia and SIM. We suggest two possible approaches to carefully investigate and correct for this effect in order to align accurately the radio and optical positions. Both approaches involve determining a Primary Reference Sample of objects to be used for tying the radio and optical reference frames together.

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32

Middelberg, E., R. P. Norris, C. A. Hales, N. Seymour, M. Johnston-Hollitt, M. T. Huynh, E. Lenc, and M. Y. Mao. "The radio properties of infrared-faint radio sources." Astronomy & Astrophysics 526 (December 13, 2010): A8. http://dx.doi.org/10.1051/0004-6361/201014926.

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33

Contigiani, O., F. de Gasperin, G. K. Miley, L. Rudnick, H. Andernach, J. K. Banfield, A. D. Kapińska, S. S. Shabala, and O. I. Wong. "Radio Galaxy Zoo: cosmological alignment of radio sources." Monthly Notices of the Royal Astronomical Society 472, no. 1 (August 2, 2017): 636–46. http://dx.doi.org/10.1093/mnras/stx1977.

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34

Afanas’ev, V. L., S. N. Dodonov, A. V. Moiseev, A. G. Gorshkov, V. K. Konnikova, and M. G. Mingaliev. "Radio and optical spectral studies of radio sources." Astronomy Reports 47, no. 6 (June 2003): 458–66. http://dx.doi.org/10.1134/1.1583772.

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35

Zovaro, Henry R. M., Nicole P. H. Nesvadba, Robert Sharp, Geoffrey V. Bicknell, Brent Groves, Dipanjan Mukherjee, and Alexander Y. Wagner. "Searching for signs of jet-driven negative feedback in the nearby radio galaxy UGC 05771." Monthly Notices of the Royal Astronomical Society 489, no. 4 (September 5, 2019): 4944–61. http://dx.doi.org/10.1093/mnras/stz2459.

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ABSTRACT Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and [Fe ii] emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a ‘stalling wind’. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source’s total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources.

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36

Todarello, Elisa, Andre Scaffidi, Marco Regis, and Marco Taoso. "Constraining below-threshold radio source counts with machine learning." Journal of Cosmology and Astroparticle Physics 2024, no. 01 (January 1, 2024): 062. http://dx.doi.org/10.1088/1475-7516/2024/01/062.

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Abstract We propose a machine-learning-based technique to determine the number density of radio sources as a function of their flux density, for use in next-generation radio surveys. The method uses a convolutional neural network trained on simulations of the radio sky to predict the number of sources in several flux bins. To train the network, we adopt a supervised approach wherein we simulate training data stemming from a large domain of possible number count models going down to fluxes a factor of 100 below the threshold for source detection. We test the model reconstruction capabilities as well as benchmark the expected uncertainties in the model predictions, observing good performance for fluxes down to a factor of ten below the threshold. This work demonstrates that the capabilities of simple deep learning models for radio astronomy can be useful tools for future surveys.

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37

Missaglia, V., F. Massaro, A. Capetti, M. Paolillo, R. P. Kraft, R. D. Baldi, and A. Paggi. "WATCAT: a tale of wide-angle tailed radio galaxies." Astronomy & Astrophysics 626 (May 30, 2019): A8. http://dx.doi.org/10.1051/0004-6361/201935058.

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We present a catalog of 47 wide-angle tailed radio galaxies (WATs), the WATCAT, mainly built including a radio morphological classification; WATs were selected by combining observations from the National Radio Astronomy Observatory/Very Large Array Sky Survey (NVSS), the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST), and the Sloan Digital Sky Survey (SDSS). We included in the catalog only radio sources showing two-sided jets with two clear “warmspots” (i.e., jet knots as bright as 20% of the nucleus) lying on the opposite side of the radio core, and having classical extended emission resembling a plume beyond them. The catalog is limited to redshifts z ≤ 0.15, and lists only sources with radio emission extended beyond 30 kpc from the host galaxy. We found that host galaxies of WATCAT sources are all luminous (−20.5 ≳ Mr ≳ −23.7), red early-type galaxies with black hole masses in the range 108 ≲ MBH ≲ 109 M⊙. The spectroscopic classification indicates that they are all low-excitation galaxies (LEGs). Comparing WAT multifrequency properties with those of FR I and FR II radio galaxies at the same redshifts, we conclude that WATs show multifrequency properties remarkably similar to FR I radio galaxies, having radio power of typical FR IIs.

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O’Dea, Christopher P., and Stefi A. Baum. "Wide-Angle-Tail (WAT) Radio Sources." Galaxies 11, no. 3 (May 12, 2023): 67. http://dx.doi.org/10.3390/galaxies11030067.

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We review the properties of Wide-Angle-Tail (WAT) radio sources. The WAT radio sources are powerful, bent radio sources typically associated with the dominant galaxy in a cluster or group. For the purpose of this review, we define the radio morphology properties of WATs as (1) a sudden jet-tail transition, (2) overall bending of the tails to one side, and (3) non-parallel tails. The mechanism for the rapid jet-tail transition is uncertain but it seems to occur near the transition from the host ISM to ICM. The jet-tail transition may make the jets easier to bend. The narrow range in radio luminosity can be understood if there is a minimum luminosity required to allow the jets to propagate undisturbed for tens of kpc and a maximum luminosity required to allow the jet disruption mechanism to act. WATs are typically hosted by the brightest cluster galaxies in clusters which are currently merging. Thus, WATs can be used as tracers of merging clusters. The merging produces large-scale bulk motions in the ICM which can provide sufficient ram pressure to bend the jets. We suggest that although the Lorentz force may not bend the jets in WATs, it may be relevant in other sources, e.g., protostellar jets.

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39

Matsumura, Nobuo, Masaya Kuniyoshi, Kazuhiro Takefuji, Kotaro Niinuma, Sumiko Kida, Akihiko Takeuchi, Kuniyuki Asuma, and Tsuneaki Daishido. "Nasu 1.4 GHz Interferometer Transient Radio Source Survey and Improvement in Detection of Radio Sources." Journal of Physics: Conference Series 31 (March 21, 2006): 193–94. http://dx.doi.org/10.1088/1742-6596/31/1/049.

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40

Shmeld, Ivar, Artis Aberfelds, and Oleksey Patoka. "Observations of Possibly New OH Excited Rotational State Masers." Proceedings of the International Astronomical Union 18, S380 (December 2022): 240–42. http://dx.doi.org/10.1017/s1743921323003125.

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AbstractIn order to search for new 6.035 GHz excited OH masers 272 star-forming regions visible from the northern hemisphere with known active methanol masers were observed with the 32 m and 16 m radio telescopes of the Ventspils International Radio Astronomy Center (VIRAC). Three possibly new excited OH maser sources at 6.035 GHz were seen.

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41

Gancio, G., C. O. Lousto, L. Combi, S. del Palacio, F. G. López Armengol, J. A. Combi, F. García, et al. "Upgraded antennas for pulsar observations in the Argentine Institute of Radio astronomy." Astronomy & Astrophysics 633 (January 2020): A84. http://dx.doi.org/10.1051/0004-6361/201936525.

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Context. The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30 m radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. Aims. We aim to introduce to the international community the upgrades performed and to show that the IAR observatory has become suitable for investigations in numerous areas of pulsar radio astronomy, such as pulsar timing arrays, targeted searches of continuous gravitational waves sources, monitoring of magnetars and glitching pulsars, and studies of a short time scale interstellar scintillation. Methods. We refurbished the two antennas at IAR to achieve high-quality timing observations. We gathered more than 1000 h of observations with both antennas in order to study the timing precision and sensitivity they can achieve. Results. We introduce the new developments for both radio telescopes at IAR. We present daily observations of the millisecond pulsar J0437−4715 with timing precision better than 1 μs. We also present a follow-up of the reactivation of the magnetar XTE J1810–197 and the measurement and monitoring of the latest (Feb. 1, 2019) glitch of the Vela pulsar (J0835–4510). Conclusions. We show that IAR is capable of performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. This opens up the possibility of pursuing several goals in pulsar science, including coordinated multi-wavelength observations with other observatories. In particular, daily observations of the millisecond pulsar J0437−4715 would increase the sensitivity of pulsar timing arrays. We also show IAR’s great potential for studying targets of opportunity and transient phenomena, such as magnetars, glitches, and fast-radio-burst sources.

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42

Curran, S. J., J. R. Allison, M. Glowacki, M. T. Whiting, and E. M. Sadler. "On the H i column density–radio source size anticorrelation in compact radio sources." Monthly Notices of the Royal Astronomical Society 431, no. 4 (April 4, 2013): 3408–13. http://dx.doi.org/10.1093/mnras/stt438.

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43

Schilizzi, RT. "Compact Structure in Continuum Radio Sources." Australian Journal of Physics 44, no. 6 (1991): 771. http://dx.doi.org/10.1071/ph910771.

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Present-day VLBI networks make observations of compact structure in a wide variety of radio sources. Examples are shown of milli-arcsecond scale structures in radio galaxies, quasars, stars and supernova remnants.

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44

Chen, Xian, and Fukun Liu. "Relationship between X-shaped radio sources and double-double radio galaxies." Proceedings of the International Astronomical Union 2, S238 (August 2006): 341–42. http://dx.doi.org/10.1017/s1743921307005352.

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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.

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45

Hollitt, C., and M. Johnston-Hollitt. "Feature Detection in Radio Astronomy using the Circle Hough Transform." Publications of the Astronomical Society of Australia 29, no. 3 (2012): 309–17. http://dx.doi.org/10.1071/as11051.

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AbstractWhile automatic detection of point sources in astronomical images has experienced a great degree of success, less effort has been directed towards the detection of extended and low-surface-brightness features. At present, existing telescopes still rely on human expertise to reduce the raw data to usable images and then to analyse the images for non-pointlike objects. However, the next generation of radio telescopes will generate unprecedented volumes of data making manual data reduction and object extraction infeasible. Without developing new methods of automatic detection for extended and diffuse objects such as supernova remnants, bent-tailed galaxies, radio relics and halos, a wealth of scientifically important results will not be uncovered. In this paper we explore the response of the Circle Hough Transform to a representative sample of different extended circular or arc-like astronomical objects. We also examine the response of the Circle Hough Transform to input images containing noise alone and inputs including point sources.

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46

Rodríguez, Luis F., Ricardo F. González, Gabriela Montes, Hassan M. Asiri, Alejandro C. Raga, and Jorge Cantó. "COMPACT RADIO SOURCES IN M17." Astrophysical Journal 755, no. 2 (August 6, 2012): 152. http://dx.doi.org/10.1088/0004-637x/755/2/152.

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47

Dwarakanath, K. S., and Ruta Kale. "RELICS OF DOUBLE RADIO SOURCES." Astrophysical Journal 698, no. 2 (June 4, 2009): L163—L168. http://dx.doi.org/10.1088/0004-637x/698/2/l163.

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48

Bjoernsson, C. I. "Polarization of Compact Radio Sources." Astrophysical Journal 416 (October 1993): 104. http://dx.doi.org/10.1086/173217.

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49

Marlow, D. R., D. Rusin, N. Jackson, P. N. Wilkinson, I. W. A. Browne, and L. Koopmans. "Redshifts of CLASS Radio Sources." Astronomical Journal 119, no. 6 (June 2000): 2629–33. http://dx.doi.org/10.1086/301375.

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50

Menon, T. K., and P. Hickson. "Radio sources in dense groups." Astrophysical Journal 296 (September 1985): 60. http://dx.doi.org/10.1086/163419.

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