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Sample records for infrared-faint radio sources

  1. Are the infrared-faint radio sources pulsars?

    Science.gov (United States)

    Cameron, A. D.; Keith, M.; Hobbs, G.; Norris, R. P.; Mao, M. Y.; Middelberg, E.

    2011-07-01

    Infrared-faint radio sources (IFRS) are objects which are strong at radio wavelengths but undetected in sensitive Spitzer observations at infrared wavelengths. Their nature is uncertain and most have not yet been associated with any known astrophysical object. One possibility is that they are radio pulsars. To test this hypothesis we undertook observations of 16 of these sources with the Parkes Radio Telescope. Our results limit the radio emission to a pulsed flux density of less than 0.21 mJy (assuming a 50 per cent duty cycle). This is well below the flux density of the IFRS. We therefore conclude that these IFRS are not radio pulsars.

  2. The radio properties of infrared-faint radio sources

    Science.gov (United States)

    Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

    2011-02-01

    Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

  3. X-ray Counterparts of Infrared Faint Radio Sources

    Science.gov (United States)

    Schartel, Norbert

    2011-10-01

    Infrared Faint Radio Sources (IFRS) are radio sources with extremely faint or even absent infrared emission in deep Spitzer Surveys. Models of their spectral energy distributions, the ratios of radio to infrared flux densities and their steep radio spectra strongly suggest that IFRS are AGN at high redshifts (2IFRS, but if confirmed, the increased AGN numbers at these redshifts will account for the unresolved part of the X-ray background. The identification of X-ray counterparts of IFRS is considered to be the smoking gun for this hypothesis. We propose to observe 8 IFRS using 30ks pointed observations. X-ray detections of IFRS with different ratios of radio-to-infrared fluxes, will constrain the class-specific SED.

  4. Morphology and astrometry of Infrared-Faint Radio Sources

    Science.gov (United States)

    Middelberg, Enno; Norris, Ray; Randall, Kate; Mao, Minnie; Hales, Christopher

    2008-10-01

    Infrared-Faint Radio Sources, or IFRS, are an unexpected class of object discovered in the Australia Telescope Large Area Survey, ATLAS. They are compact 1.4GHz radio sources with no visible counterparts in co-located (relatively shallow) Spitzer infrared and optical images. We have detected two of these objects with VLBI, indicating the presence of an AGN. These observations and our ATLAS data indicate that IFRS are extended on scales of arcseconds, and we wish to image their morphologies to obtain clues about their nature. These observations will also help us to select optical counterparts from very deep, and hence crowded, optical images which we have proposed. With these data in hand, we will be able to compare IFRS to known object types and to apply for spectroscopy to obtain their redshifts.

  5. Do the enigmatic ``Infrared-Faint Radio Sources'' include pulsars?

    Science.gov (United States)

    Hobbs, George; Middelberg, Enno; Norris, Ray; Keith, Michael; Mao, Minnie; Champion, David

    2009-04-01

    The Australia Telescope Large Area Survey (ATLAS) team have surveyed seven square degrees of sky at 1.4GHz. During processing some unexpected infrared-faint radio sources (IFRS sources) were discovered. The nature of these sources is not understood, but it is possible that some of these sources may be pulsars within our own galaxy. We propose to observe the IFRS sources with steep spectral indices using standard search techniques to determine whether or not they are pulsars. A pulsar detection would 1) remove a subset of the IFRS sources from the ATLAS sample so they would not need to be observed with large optical/IR telescopes to find their hosts and 2) be intrinsically interesting as the pulsar would be a millisecond pulsar and/or have an extreme spatial velocity.

  6. VLBI observations of Infrared-Faint Radio Sources

    Science.gov (United States)

    Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

    2006-10-01

    We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

  7. Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

    NARCIS (Netherlands)

    Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

    2016-01-01

    Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence

  8. Evidence for Infrared-faint Radio Sources as z > 1 Radio-loud Active Galactic Nuclei

    Science.gov (United States)

    Huynh, Minh T.; Norris, Ray P.; Siana, Brian; Middelberg, Enno

    2010-02-01

    Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 μm) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z >~ 1) active galactic nuclei.

  9. The radio spectral energy distribution of infrared-faint radio sources

    Science.gov (United States)

    Herzog, A.; Norris, R. P.; Middelberg, E.; Seymour, N.; Spitler, L. R.; Emonts, B. H. C.; Franzen, T. M. O.; Hunstead, R.; Intema, H. T.; Marvil, J.; Parker, Q. A.; Sirothia, S. K.; Hurley-Walker, N.; Bell, M.; Bernardi, G.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Callingham, J. R.; Deshpande, A. A.; Dwarakanath, K. S.; For, B.-Q.; Greenhill, L. J.; Hancock, P.; Hazelton, B. J.; Hindson, L.; Johnston-Hollitt, M.; Kapińska, A. D.; Kaplan, D. L.; Lenc, E.; Lonsdale, C. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Morgan, J.; Oberoi, D.; Offringa, A.; Ord, S. M.; Prabu, T.; Procopio, P.; Udaya Shankar, N.; Srivani, K. S.; Staveley-Smith, L.; Subrahmanyan, R.; Tingay, S. J.; Wayth, R. B.; Webster, R. L.; Williams, A.; Williams, C. L.; Wu, C.; Zheng, Q.; Bannister, K. W.; Chippendale, A. P.; Harvey-Smith, L.; Heywood, I.; Indermuehle, B.; Popping, A.; Sault, R. J.; Whiting, M. T.

    2016-10-01

    Context. Infrared-faint radio sources (IFRS) are a class of radio-loud (RL) active galactic nuclei (AGN) at high redshifts (z ≥ 1.7) that are characterised by their relative infrared faintness, resulting in enormous radio-to-infrared flux density ratios of up to several thousand. Aims: Because of their optical and infrared faintness, it is very challenging to study IFRS at these wavelengths. However, IFRS are relatively bright in the radio regime with 1.4 GHz flux densities of a few to a few tens of mJy. Therefore, the radio regime is the most promising wavelength regime in which to constrain their nature. We aim to test the hypothesis that IFRS are young AGN, particularly GHz peaked-spectrum (GPS) and compact steep-spectrum (CSS) sources that have a low frequency turnover. Methods: We use the rich radio data set available for the Australia Telescope Large Area Survey fields, covering the frequency range between 150 MHz and 34 GHz with up to 19 wavebands from different telescopes, and build radio spectral energy distributions (SEDs) for 34 IFRS. We then study the radio properties of this class of object with respect to turnover, spectral index, and behaviour towards higher frequencies. We also present the highest-frequency radio observations of an IFRS, observed with the Plateau de Bure Interferometer at 105 GHz, and model the multi-wavelength and radio-far-infrared SED of this source. Results: We find IFRS usually follow single power laws down to observed frequencies of around 150 MHz. Mostly, the radio SEDs are steep (α IFRS show statistically significantly steeper radio SEDs than the broader RL AGN population. Our analysis reveals that the fractions of GPS and CSS sources in the population of IFRS are consistent with the fractions in the broader RL AGN population. We find that at least % of IFRS contain young AGN, although the fraction might be significantly higher as suggested by the steep SEDs and the compact morphology of IFRS. The detailed multi

  10. Infrared Faint Radio Sources in the Extended Chandra Deep Field South

    Science.gov (United States)

    Huynh, Minh T.

    2009-01-01

    Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey (ATLAS) which have no observable counterpart in the Spitzer Wide-area Infrared Extragalactic Survey (SWIRE). The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6 to 70 micron) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the SED of these objects shows that they are consistent with high redshift AGN (z > 2).

  11. Infrared-faint radio sources are at high redshifts. Spectroscopic redshift determination of infrared-faint radio sources using the Very Large Telescope

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Sharp, R.; Spitler, L. R.; Parker, Q. A.

    2014-07-01

    Context. Infrared-faint radio sources (IFRS) are characterised by relatively high radio flux densities and associated faint or even absent infrared and optical counterparts. The resulting extremely high radio-to-infrared flux density ratios up to several thousands were previously known only for high-redshift radio galaxies (HzRGs), suggesting a link between the two classes of object. However, the optical and infrared faintness of IFRS makes their study difficult. Prior to this work, no redshift was known for any IFRS in the Australia Telescope Large Area Survey (ATLAS) fields which would help to put IFRS in the context of other classes of object, especially of HzRGs. Aims: This work aims at measuring the first redshifts of IFRS in the ATLAS fields. Furthermore, we test the hypothesis that IFRS are similar to HzRGs, that they are higher-redshift or dust-obscured versions of these massive galaxies. Methods: A sample of IFRS was spectroscopically observed using the Focal Reducer and Low Dispersion Spectrograph 2 (FORS2) at the Very Large Telescope (VLT). The data were calibrated based on the Image Reduction and Analysis Facility (IRAF) and redshifts extracted from the final spectra, where possible. This information was then used to calculate rest-frame luminosities, and to perform the first spectral energy distribution modelling of IFRS based on redshifts. Results: We found redshifts of 1.84, 2.13, and 2.76, for three IFRS, confirming the suggested high-redshift character of this class of object. These redshifts and the resulting luminosities show IFRS to be similar to HzRGs, supporting our hypothesis. We found further evidence that fainter IFRS are at even higher redshifts. Conclusions: Considering the similarities between IFRS and HzRGs substantiated in this work, the detection of IFRS, which have a significantly higher sky density than HzRGs, increases the number of active galactic nuclei in the early universe and adds to the problems of explaining the formation of

  12. Infrared-faint radio sources in the SERVS deep fields. Pinpointing AGNs at high redshift

    Science.gov (United States)

    Maini, A.; Prandoni, I.; Norris, R. P.; Spitler, L. R.; Mignano, A.; Lacy, M.; Morganti, R.

    2016-12-01

    Context. Infrared-faint radio sources (IFRS) represent an unexpected class of objects which are relatively bright at radio wavelength, but unusually faint at infrared (IR) and optical wavelengths. A recent and extensive campaign on the radio-brightest IFRSs (S1.4 GHz≳ 10 mJy) has provided evidence that most of them (if not all) contain an active galactic nuclei (AGN). Still uncertain is the nature of the radio-faintest IFRSs (S1.4 GHz≲ 1 mJy). Aims: The scope of this paper is to assess the nature of the radio-faintest IFRSs, testing their classification and improving the knowledge of their IR properties by making use of the most sensitive IR survey available so far: the Spitzer Extragalactic Representative Volume Survey (SERVS). We also explore how the criteria of IFRSs can be fine-tuned to pinpoint radio-loud AGNs at very high redshift (z > 4). Methods: We analysed a number of IFRS samples identified in SERVS fields, including a new sample (21 sources) extracted from the Lockman Hole. 3.6 and 4.5 μm IR counterparts of the 64 sources located in the SERVS fields were searched for and, when detected, their IR properties were studied. Results: We compared the radio/IR properties of the IR-detected IFRSs with those expected for a number of known classes of objects. We found that IR-detected IFRSs are mostly consistent with a mixture of high-redshift (z ≳ 3) radio-loud AGNs. The faintest ones (S1.4 GHz 100 μJy), however, could be also associated with nearer (z 2) dust-enshrouded star-burst galaxies. We also argue that, while IFRSs with radio-to-IR ratios >500 can very efficiently pinpoint radio-loud AGNs at redshift 2 < z < 4, lower radio-to-IR ratios ( 100-200) are expected for higher redshift radio-loud AGNs.

  13. The first VLBI image of an infrared-faint radio source

    Science.gov (United States)

    Middelberg, E.; Norris, R. P.; Tingay, S.; Mao, M. Y.; Phillips, C. J.; Hotan, A. W.

    2008-11-01

    Context: We investigate the joint evolution of active galactic nuclei and star formation in the Universe. Aims: In the 1.4 GHz survey with the Australia Telescope Compact Array of the Chandra Deep Field South and the European Large Area ISO Survey - S1 we have identified a class of objects which are strong in the radio but have no detectable infrared and optical counterparts. This class has been called Infrared-Faint Radio Sources, or IFRS. 53 sources out of 2002 have been classified as IFRS. It is not known what these objects are. Methods: To address the many possible explanations as to what the nature of these objects is we have observed four sources with the Australian Long Baseline Array. Results: We have detected and imaged one of the four sources observed. Assuming that the source is at a high redshift, we find its properties in agreement with properties of Compact Steep Spectrum sources. However, due to the lack of optical and infrared data the constraints are not particularly strong.

  14. A search for AGN activity in Infrared-Faint Radio Sources (IFRS)

    Science.gov (United States)

    Lenc, Emil; Middelberg, Enno; Norris, Ray; Mao, Minnie

    2010-04-01

    We propose to observe a large sample of radio sources from the ATLAS (Australia Telescope Large Area Survey) source catalogue with the LBA, to determine their compactness. The sample consists of 36 sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubber Infrared-Faint Radio Sources (IFRS), is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations. We will measure the flux densities on long baselines to determine their compactness. Only five IFRS have been previously targeted with VLBI observations (resulting in two detections). We propose using single baseline (Parkes-ATCA) eVLBI observations with the LBA at 1 Gbps to maximise sensitivity. With the observations proposed here we will increase the number of VLBI-observed IFRS from 5 to 36, allowing us to draw statistical conclusions about this intriguing new class of objects.

  15. DEEP SPITZER OBSERVATIONS OF INFRARED-FAINT RADIO SOURCES: HIGH-REDSHIFT RADIO-LOUD ACTIVE GALACTIC NUCLEI?

    International Nuclear Information System (INIS)

    Norris, Ray P.; Mao, Minnie; Afonso, Jose; Cava, Antonio; Farrah, Duncan; Oliver, Seb; Huynh, Minh T.; Mauduit, Jean-Christophe; Surace, Jason; Ivison, R. J.; Jarvis, Matt; Lacy, Mark; Maraston, Claudia; Middelberg, Enno; Seymour, Nick

    2011-01-01

    Infrared-faint radio sources (IFRSs) are a rare class of objects which are relatively bright at radio wavelengths but very faint at infrared and optical wavelengths. Here we present sensitive near-infrared observations of a sample of these sources taken as part of the Spitzer Extragalactic Representative Volume Survey. Nearly all the IFRSs are undetected at a level of ∼1 μJy in these new deep observations, and even the detections are consistent with confusion with unrelated galaxies. A stacked image implies that the median flux density is S 3.6μm ∼ 0.2 μJy or less, giving extreme values of the radio-infrared flux density ratio. Comparison of these objects with known classes of object suggests that the majority are probably high-redshift radio-loud galaxies, possibly suffering from significant dust extinction.

  16. VizieR Online Data Catalog: Infrared-faint radio sources catalog (Collier+, 2014)

    Science.gov (United States)

    Collier, J. D.; Banfield, J. K.; Norris, R. P.; Schnitzeler, D. H. F. M.; Kimball, A. E.; Filipovic, M. D.; Jarrett, T. H.; Lonsdale, C. J.; Tothill, N. F. H.

    2014-11-01

    The 20cm radio data come from the Unified Radio Catalog (URC) compiled by Kimball & Ivezic (2008AJ....136..684K). This radio catalogue combines data from the National Radio Astronomy Observatory (NRAO) VLA Sky Survey (NVSS; Condon et al., 1998, Cat. VIII/65), Faint Images of the Radio Sky at Twenty Centimeters (FIRST; Becker, White & Helfand, 1995, cat. VIII/92), Green Bank 6cm survey (GB6; Gregory et al., 1996, Cat. VIII/40), the Westerbork Northern Sky Survey (WENSS; Rengelink et al. 1997; de Bruyn et al. 2000, Cat. VIII/62) and the Sloan Digital Sky Survey Data Release 6 (SDSS DR6; Adelman-McCarthy et al., 2008, Cat. II/282). We use updated NVSS and FIRST data from the URC version 2.0 (Kimball & Ivezic, in preparation), which includes a number of new sources as well as updated positions and flux densities. The IR data come from WISE (Wright et al. (WISE Team) 2009, Cat. II/311), which is an all-sky survey centred at 3.4, 4.6, 12 and 22um (referred to as bands W1, W2, W3 and W4), with respective angular resolutions of 6.1, 6.4, 6.5 and 12.0-arcsec (full width at half-maximum, FWHM), and typical 5σ sensitivity levels of 0.08, 0.11, 1 and 6mJy, with sensitivity increasing towards the ecliptic poles. (1 data file).

  17. Infrared-faint radio sources: a cosmological view. AGN number counts, the cosmic X-ray background and SMBH formation

    Science.gov (United States)

    Zinn, P.-C.; Middelberg, E.; Ibar, E.

    2011-07-01

    Context. Infrared-faint radio sources (IFRS) are extragalactic emitters clearly detected at radio wavelengths but barely detected or undetected at optical and infrared wavelengths, with 5σ sensitivities as low as 1 μJy. Aims: Spectral energy distribution (hereafter SED) modelling and analyses of their radio properties indicate that IFRS are consistent with a population of (potentially extremely obscured) high-redshift AGN at 3 ≤ z ≤ 6. We demonstrate some astrophysical implications of this population and compare them to predictions from models of galaxy evolution and structure formation. Methods: We compiled a list of IFRS from four deep extragalactic surveys and extrapolated the IFRS number density to a survey-independent value of (30.8 ± 15.0) deg-2. We computed the IFRS contribution to the total number of AGN in the Universe to account for the cosmic X-ray background. By estimating the black hole mass contained in IFRS, we present conclusions for the SMBH mass density in the early universe and compare it to relevant simulations of structure formation after the Big Bang. Results: The number density of AGN derived from the IFRS density was found to be ~310 deg-2, which is equivalent to a SMBH mass density of the order of 103 M⊙ Mpc-3 in the redshift range 3 ≤ z ≤ 6. This produces an X-ray flux of 9 × 10-16 W m-2 deg-2 in the 0.5-2.0 keV band and 3 × 10-15 W m-2 deg-2 in the 2.0-10 keV band, in agreement with the missing unresolved components of the Cosmic X-ray Background. To address SMBH formation after the Big Bang we invoke a scenario involving both halo gas accretion and major mergers.

  18. Infrared-faint radio sources remain undetected at far-infrared wavelengths. Deep photometric observations using the Herschel Space Observatory

    Science.gov (United States)

    Herzog, A.; Norris, R. P.; Middelberg, E.; Spitler, L. R.; Leipski, C.; Parker, Q. A.

    2015-08-01

    Context. Showing 1.4 GHz flux densities in the range of a few to a few tens of mJy, infrared-faint radio sources (IFRS) are a type of galaxy characterised by faint or absent near-infrared counterparts and consequently extreme radio-to-infrared flux density ratios up to several thousand. Recent studies showed that IFRS are radio-loud active galactic nuclei (AGNs) at redshifts ≳2, potentially linked to high-redshift radio galaxies (HzRGs). Aims: This work explores the far-infrared emission of IFRS, providing crucial information on the star forming and AGN activity of IFRS. Furthermore, the data enable examining the putative relationship between IFRS and HzRGs and testing whether IFRS are more distant or fainter siblings of these massive galaxies. Methods: A sample of six IFRS was observed with the Herschel Space Observatory between 100 μm and 500 μm. Using these results, we constrained the nature of IFRS by modelling their broad-band spectral energy distribution (SED). Furthermore, we set an upper limit on their infrared SED and decomposed their emission into contributions from an AGN and from star forming activity. Results: All six observed IFRS were undetected in all five Herschel far-infrared channels (stacking limits: σ = 0.74 mJy at 100 μm, σ = 3.45 mJy at 500 μm). Based on our SED modelling, we ruled out the following objects to explain the photometric characteristics of IFRS: (a) known radio-loud quasars and compact steep-spectrum sources at any redshift; (b) starburst galaxies with and without an AGN and Seyfert galaxies at any redshift, even if the templates were modified; and (c) known HzRGs at z ≲ 10.5. We find that the IFRS analysed in this work can only be explained by objects that fulfil the selection criteria of HzRGs. More precisely, IFRS could be (a) known HzRGs at very high redshifts (z ≳ 10.5); (b) low-luminosity siblings of HzRGs with additional dust obscuration at lower redshifts; (c) scaled or unscaled versions of Cygnus A at any

  19. Active galactic nuclei cores in infrared-faint radio sources. Very long baseline interferometry observations using the Very Long Baseline Array

    Science.gov (United States)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

    2015-06-01

    Context. Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z ≳ 2). Aims: Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. Methods: We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Results: Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginally higher VLBI detection fraction than randomly selected sources with mJy flux densities at arcsec-scales. Moreover, our data provide a positive correlation between compactness - defined as the ratio of milliarcsec- to arcsec-scale flux density - and redshift for IFRS, but suggest a decreasing mean compactness with increasing arcsec-scale radio flux density. Based on these findings, we suggest that IFRS tend to contain young AGNs whose jets have not formed yet or have not expanded, equivalent to very compact objects. We found two IFRS that are resolved into two components. The two components are spatially separated by a few hundred milliarcseconds in both cases. They might be components of one AGN, a binary black hole, or the result of gravitational lensing.

  20. Compact radio sources

    International Nuclear Information System (INIS)

    Altschuler, D.R.

    1975-01-01

    Eighty-seven compact radio sources were monitored between 1971 and 1974 with the National Radio Astronomy Observatory interferometer. Both flux density and polarization were measured at intervals of about one month at wavelengths of 3.7 and 11.1 cms. Forty-four sources showed definite variability in their total and/or polarized flux density. The variations in polarization were of a shorter time scale than the corresponding flux density variations. Some of the qualitative features of an expanding source model were observed. The data suggest that some form of injection of relativistic electrons is taking place. The absence of significant depolarization in the variable sources indicates that only a small fraction of the mass of the radio outburst is in the form of non-relativistic plasma. Some of the objects observed belong to the BL-Lacertal class. It is shown that this class is very inhomogeneous in its radio properties. For the violently variable BL-Lacertal type objects the spectrum, flux variations and polarization data strongly suggest that these are very young objects

  1. Central radio sources

    International Nuclear Information System (INIS)

    Phinney, E.S.

    1985-01-01

    The compact radio sources in the nuclei of most active galaxies lie closer to their centers of activity than any other region accessible to observation, excepting only the broad emission line region. They provide uniquely strong evidence for bulk motion of matter at relativistic velocities, encouraging the belief that the activity originates in a gravitational potential well whose escape velocity is of the order of the speed of light. The observational facts are reviewed as well as several theoretical pictures of them. Those places where systematic observations could help to distinguish the true theoretical picture from the many competing forgeries are emphasized. 76 references

  2. The History and Evolution of Young and Distant Radio Sources

    Science.gov (United States)

    Collier, Jordan

    We study two classes of object to gain a better understanding of the evolution of Active Galactic Nuclei (AGN): Infrared-Faint Radio Sources (IFRSs) and Gigahertz Peaked Spectrum (GPS) / Compact Steep Spectrum (CSS) sources. IFRSs are a recently discovered rare class of object, which were found to be strong in the radio but undetectable in extremely sensitive infrared observations from the Spitzer Space Telescope, even in stacked images with sigma 3. Therefore, IFRSs may significantly increase the number of known high-redshift galaxies. However, their non-detections in the optical and infrared prevented confirmation of their nature. Previous studies of IFRSs focused on very sensitive observations of a few small regions of the sky, and the largest sample consisted of 55 IFRSs. However, we follow the strategy of combining radio data with IR and optical data for a large region of the sky. Using these data, we discover a population of >1300 brighter IFRSs which are, for the first time, reliably detected in the infrared and optical. We present the first spectroscopic redshifts of IFRSs and show that the brightest IFRSs are at z > 2. Furthermore, we rule out that IFRSs are Star Forming Galaxies, hotspots, lobes or misidentifications. We find the first X-ray counterparts of IFRSs, and increase the number of known polarised IFRSs five-fold. We present an analysis of their radio spectra and show that IFRSs consist of GPS, CSS and ultra-steep-spectrum sources. We follow up >50 of these using VLBI observations, and confirm the AGN status of IFRSs. GPS and CSS sources are compact radio sources with a convex radio spectrum. They are widely thought to represent young and evolving radio galaxies that have recently launched their jets. However, good evidence exists in individual cases that GPS and CSS sources are one of the following: 1) frustrated by interactions with dense gas and dust in their environment; 2) prematurely dying radio sources; 3) recurrent radio galaxies. Their

  3. Magnetogasdynamics of double radio sources

    International Nuclear Information System (INIS)

    Nepveu, M.

    1979-01-01

    The magnetogasdynamical behaviour of plasmoids moving through an ambient gas is investigated numerically with a two-dimensional code, based on the SHASTA scheme. The astrophysical importance of this study lies in the observed extended extragalactic radio sources. It is assumed that plasma clouds with cylinder symmetry are ejected from the nucleus of a galaxy. Their large-scale evolution in the intergalactic medium (IGM) is followed. The gas dynamics of an ejected cloud, the magnetogasdynamics of ejected clouds, the Christiansen-Pacholczyk-Scott picture for radio galaxies and the shear layers in double radio sources are studied. (Auth.)

  4. Radio outbursts in extragalactic sources

    International Nuclear Information System (INIS)

    Kinzel, W.M.

    1989-01-01

    Three aspects of the flux density variability of extragalactic radio sources were examined: millimeter wavelength short timescale variability, the spectral evolution of outbursts, and whether the outbursts are periodically spaced. Observations of extragalactic radio sources were conducted using the Five College Radio Astronomy Observatory between January and June 1985 at 88.2 GHz and during June and July 1985 at 40.0 GHz. Many of the sources exhibited significant flux density variations during the observing span. In addition, the most rapid variations observed were comparable with those reported in previous works. Two sources, 0355+50 and OJ287, both exhibited outbursts whose rise and fall timescales were less than a month. An anomalous flux density dropout was observed in 3C446 and was interpreted as an occultation event. Data at five frequencies between 2.7 and 89.6 GHz from the Dent-Balonek monitoring program were used to investigate the spectral evolution of eight outbursts. Outburst profile fitting was used to deconvolve the individual outbursts from one another at each frequency. The fit profiles were used to generate multiple epoch spectra to investigate the evolution of the outbursts. A phase residual minimization method was used to examine four sources for periodic behavior

  5. Identification of southern radio sources

    International Nuclear Information System (INIS)

    Savage, A.; Bolton, J.G.; Wright, A.E.

    1976-01-01

    Identifications are suggested for 36 radio sources from the southern zones of the Parkes 2700 MHz survey, 28 with galaxies, six with confirmed and two with suggested quasi-stellar objects. The identifications were made from the ESO quick blue survey plates, the SRC IIIa-J deep survey plates and the Palomar sky survey prints. Accurate optical positions have also been measured for nine of the objects and for five previously suggested identifications. (author)

  6. Identification of southern radio sources

    International Nuclear Information System (INIS)

    Savage, A.; Bolton, J.G.; Wright, A.E.

    1977-01-01

    Identifications are suggested for 53 radio sources from the southern zones of the Parkes 2700-MHz survey, 32 with galaxies, 11 with suggested QSOs and 10 with confirmed QSOs. The identifications were made from the ESO quick blue survey plates, the SRC IIIa-J deep survey plates and the Palomar Sky Survey prints. Accurate optical positions have been measured for four of the new identifications and for two previously suggested identifications. A further nine previously suggested QSO identifications have also been confirmed by two-colour photography or spectroscopy. (author)

  7. Identification of southern radio sources

    International Nuclear Information System (INIS)

    Savage, A.

    1976-01-01

    Identifications are suggested for 32 radio sources from the southern zones of the Parkes 2700 MHz survey, 18 with galaxies, one with a confirmed and 12 with possible quasistellar objects, and one with a supernova remnant in the Large Magellanic Cloud. The identifications were made from the ESO IIa-O quick blue survey plates, the SRC IIIa-J deep survey plates and the Palomar sky survey prints. Accurate optical positions have also been measured for 10 of the objects and for five previously suggested QSOs. (author)

  8. Radio halo sources in clusters of galaxies

    International Nuclear Information System (INIS)

    Hanisch, R.J.

    1986-01-01

    Radio halo sources remain one of the most enigmatic of all phenomena related to radio emission from galaxies in clusters. The morphology, extent, and spectral structure of these sources are not well known, and the models proposed to explain them suffer from this lack of observational detail. However, recent observations suggest that radio halo sources may be a composite of relic radio galaxies. The validity of this model could be tested using current and planned high resolutions, low-frequency radio telescopes. 31 references

  9. Radio Frequency Energy Harvesting Sources

    Directory of Open Access Journals (Sweden)

    Action NECHIBVUTE

    2017-12-01

    Full Text Available This radio frequency (RF energy harvesting is an emerging technology and research area that promises to produce energy to run low-power wireless devices. The great interest that has recently been paid to RF harvesting is predominantly driven by the great progress in both wireless communication systems and broadcasting technologies that have availed a lot of freely propagating ambient RF energy. The principle aim of an RF energy harvesting system is to convert the received ambient RF energy into usable DC power. This paper presents a state of the art concise review of RF energy harvesting sources for low power applications, and also discusses open research questions and future research directions on ambient RF energy harvesting.

  10. Sources of the Radio Background Considered

    Energy Technology Data Exchange (ETDEWEB)

    Singal, J.; /KIPAC, Menlo Park /Stanford U.; Stawarz, L.; /KIPAC, Menlo Park /Stanford U. /Jagiellonian U., Astron. Observ.; Lawrence, A.; /Edinburgh U., Inst. Astron. /KIPAC, Menlo Park /Stanford U.; Petrosian, V.; /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., Appl. Phys. Dept.

    2011-08-22

    We investigate possible origins of the extragalactic radio background reported by the ARCADE 2 collaboration. The surface brightness of the background is several times higher than that which would result from currently observed radio sources. We consider contributions to the background from diffuse synchrotron emission from clusters and the intergalactic medium, previously unrecognized flux from low surface brightness regions of radio sources, and faint point sources below the flux limit of existing surveys. By examining radio source counts available in the literature, we conclude that most of the radio background is produced by radio point sources that dominate at sub {mu}Jy fluxes. We show that a truly diffuse background produced by elections far from galaxies is ruled out because such energetic electrons would overproduce the observed X-ray/{gamma}-ray background through inverse Compton scattering of the other photon fields. Unrecognized flux from low surface brightness regions of extended radio sources, or moderate flux sources missed entirely by radio source count surveys, cannot explain the bulk of the observed background, but may contribute as much as 10%. We consider both radio supernovae and radio quiet quasars as candidate sources for the background, and show that both fail to produce it at the observed level because of insufficient number of objects and total flux, although radio quiet quasars contribute at the level of at least a few percent. We conclude that the most important population for production of the background is likely ordinary starforming galaxies above redshift 1 characterized by an evolving radio far-infrared correlation, which increases toward the radio loud with redshift.

  11. Observations of radio sources or 'What happened to radio stars?'

    International Nuclear Information System (INIS)

    Conway, R.G.

    1988-01-01

    A review is given of the early history of the interpretation of the radiation mechanisms following the discovery of the discrete radio sources, both galactic and extragalactic. The conflicting views which prevailed in the early fifties are discussed in some detail: some advocated thermal radiation from stars relatively close by, and others proposed the alternative that synchrotron radiation was responsible for the majority of the radio sources. Attention is drawn to the importance of high-resolution interferometry, whereby the structure of many of the sources could be obtained. Red-shift measurements and spectral distributions also played a part in determining distances and flux strengths at the sources. (U.K.)

  12. A radio and optical study of Molonglo radio sources

    Science.gov (United States)

    Ishwara-Chandra, C. H.; Saikia, D. J.; McCarthy, P. J.; van Breugel, W. J. M.

    2001-05-01

    We present multi-wavelength radio observations with the Very Large Array, and narrow- and broad-band optical observations with the 2.5-m telescope at the Las Campanas Observatory, of a well-defined sample of high-luminosity Fanaroff-Riley class II radio galaxies and quasars, selected from the Molonglo Reference Catalogue 1-Jy sample. These observations were carried out as part of a programme to investigate the effects of orientation and environment on some of the observed properties of these sources. We examine the dependence of the Liu-Pooley relationship, which shows that radio lobes with flatter radio spectra are less depolarized, on size, identification and redshift, and show that it is significantly stronger for smaller sources, with the strength of the relationship being similar for both radio galaxies and quasars. In addition to Doppler effects, there appear to be intrinsic differences between the lobes on opposite sides. We discuss the asymmetry in brightness and location of the hotspots, and present estimates of the ages and velocities from matched-resolution observations in the L and C bands. Narrow- and broad-band optical images of some of these sources were made to study their environments and correlate with the symmetry parameters. An extended emission-line region is seen in a quasar, and in four of the objects possible companion galaxies are seen close to the radio axis.

  13. Particle reacceleration and apparent radio source structure

    International Nuclear Information System (INIS)

    Eilek, J.A.

    1982-01-01

    The radio galaxy model which uses magnetohydrodynamic turbulence generated by surface instabilities to reaccelerate the radiating electrons has striking consequences for apparent source structure. Strong wave damping in the plasma results in a narrow turbulent edge. Particles accelerated in this edge must diffuse across field lines into the radio source; this predicts strong limb brightening in some cases. The structure of this edge and diffusion into the source are described. The relevance of this model to jets, radio tails, and standard double sources is discussed

  14. Extended radio sources in the cluster environment

    International Nuclear Information System (INIS)

    Burns, J.O. Jr.

    1979-01-01

    Extended radio galaxies that lie in rich and poor clusters were studied. A sample of 3CR and 4C radio sources that spatially coincide with poor Zwicky clusters of galaxies was observed to obtain accurate positions and flux densities. Then interferometer observations at a resolution of approx. = 10 arcsec were performed on the sample. The resulting maps were used to determine the nature of the extended source structure, to make secure optical identifications, and to eliminate possible background sources. The results suggest that the environments around both classical double and head-tail radio sources are similar in rich and poor clusters. The majority of the poor cluster sources exhibit some signs of morphological distortion (i.e., head-tails) indicative of dynamic interaction with a relatively dense intracluster medium. A large fraction (60 to 100%) of all radio sources appear to be members of clusters of galaxies if one includes both poor and rich cluster sources. Detailed total intensity and polarization observations for a more restricted sample of two classical double sources and nine head-tail galaxies were also performed. The purpose was to examine the spatial distributions of spectral index and polarization. Thin streams of radio emission appear to connect the nuclear radio-point components to the more extended structures in the head-tail galaxies. It is suggested that a non-relativistic plasma beam can explain both the appearance of the thin streams and larger-scale structure as well as the energy needed to generate the observed radio emission. The rich and poor radio cluster samples are combined to investigate the relationship between source morphology and the scale sizes of clustering. There is some indication that a large fraction of radio sources, including those in these samples, are in superclusters of galaxies

  15. The Origin of Powerful Radio Sources

    Science.gov (United States)

    Wilson, A. S.; Colbert, E. J. M.

    1995-05-01

    Radio-loud active galaxies are associated with elliptical or elliptical-like galaxies, many of which appear to be the result of a recent merger. In contrast, radio-quiet active galaxies prefer spiral hosts. Despite the very large difference in radio luminosities between the two classes, their continua and line spectra from infrared through X-ray frequencies are very similar. In this paper, we describe recent developments of our model (Ap. J. 438, 62 1995) in which the radio-loud phenomenon is the result of a merger of two galaxies, with each galaxy nucleus containing a slowly (or non-) rotating supermassive black hole. It is envisaged that the two black holes eventually coalesce. For the small fraction of mergers in which the two holes are both massive and of comparable mass, a rapidly-spinning, high-mass hole results. The spin energy of a rapidly rotating 10(8-9) solar mass hole suffices to provide the ~ 10(60) ergs in relativistic particles and magnetic fields in the most energetic radio sources. Luminous radio-quiet active galaxies contain high-mass, slowly-rotating holes, with the infrared through X-ray emission of both classes being fuelled by accretion as commonly assumed. We discuss constraints on the model from the luminosity functions of radio-loud and radio-quiet galaxies and from the known cosmological evolution of the radio source population; this evolution is assumed to reflect higher galaxy merger rates in the past.

  16. Radio Source Morphology: 'nature or nuture'?

    Science.gov (United States)

    Banfield, Julie; Emonts, Bjorn; O'Sullivan, Shane

    2012-10-01

    Radio sources, emanating from supermassive black-holes in the centres of active galaxies, display a large variety of morphological properties. It is a long-standing debate to what extent the differences between various types of radio sources are due to intrinsic properties of the central engine (`nature') or due to the properties of the interstellar medium that surrounds the central engine and host galaxy (`nurture'). Settling this `nature vs. nurture' debate for nearby radio galaxies, which can be studied in great detail, is vital for understanding the properties and evolution of radio galaxies throughout the Universe. We propose to observe the radio galaxy NGC 612 where previous observations have detected the presence of a large-scale HI bridge between the host galaxy and a nearby galaxy NGC 619. We request a total of 13 hrs in the 750m array-configuration to determine whether or not the 100 kpc-scale radio source morphology is directly related to the intergalactic distribution of neutral hydrogen gas.

  17. Evolutionary tracks of extended radio sources

    International Nuclear Information System (INIS)

    Baldwin, J.E.

    1982-01-01

    We know almost nothing about the evolutionary tracks of extragalactic radio sources but those tracks are, however, strongly constrained by the distribution of sources in the radio luminosity, P, overall physical size, D, diagram. The P-D diagram for the 3CR 166 source sample of Jenkins et al. (1977) is presented with later additions. Most of the sources are identified and have known redshifts. Because of doubts about the completeness of the sample in this region, the author has made searches in the 6C 151MHz survey for sources with specific surface brightnesses. The numbers found to a limiting flux density of 1-2 Jy suggest that there is no serious underestimate of the numbers in 166 source sample. (Auth.)

  18. Reflection jets and collimation of radio sources

    International Nuclear Information System (INIS)

    Pacholczyk, A.G.

    1983-01-01

    A discussion of the hydrodynamics of jets formed by discrete portions of materials ejected from the parent galaxy through a channel, and reflected back to it as a result of an encounter with the material accumulated at the end of the channel, is the basis of the present descriptive hypothesis for a class of jets in extended radio sources. The model encompasses the view of extended radio sources as the multiple ejection of plasmoids through a channel, as well as the formation of retrojets through the interaction of a plasmon with the dense relic material at the end of a channel, and the collimation of plasmon material in channels. 14 references

  19. Surveys of radio sources at 5 GHz

    International Nuclear Information System (INIS)

    Pauliny-Toth, I.I.K.

    1977-01-01

    A number of surveys have been carried out at a frequency of 5 GHz at the National Radio Astronomy Observatory (NRAO) and at the Max-Planck-Institut fuer Radioastronomy (MPIFR) with the aim of determining the number-flux density relation for the sources detected and also of obtaining their radio spectra and optical identifications. The surveys fall into two categories: first, the strong source (S) surveys which are intended in due course to cover the whole northern sky and to be complete above a flux density of about 0.6 Jy; second, surveys of limited areas of sky down to lower levels of the flux density. (Auth.)

  20. RADIO SOURCE FEEDBACK IN GALAXY EVOLUTION

    International Nuclear Information System (INIS)

    Shabala, Stanislav; Alexander, Paul

    2009-01-01

    We present a galaxy evolution model which incorporates a physically motivated implementation of active galactic nucleus feedback. Intermittent jets inflate cocoons of radio plasma which then expand supersonically, shock heating the ambient gas. The model reproduces observed star formation histories to the highest redshifts for which reliable data exist, as well as the observed galaxy color bimodality. Intermittent radio source feedback also naturally provides a way of keeping the black hole and spheroid growth in step. We find possible evidence for a top-heavy initial mass function for z > 2, consistent with observations of element abundances, and submillimeter and Lyman break galaxy counts.

  1. Rapid variability of extragalactic radio sources

    Energy Technology Data Exchange (ETDEWEB)

    Quirrenbach, A.; Witzel, A.; Krichbaum, T.; Hummel, C.A.; Alberdi, A.; Schalinski, C.

    1989-02-02

    Since its discovery more than 20 years ago, variability of extragalactic radio sources on timescales of weeks to years has been the subject of many investigations. We have examined the variability of these sources on timescales of hours at wavelengths of 6 and 11 cm using the 100-m telescope of the Max-Planck-Institut fuer Radioastronomie and report the results for two sources. The quasar QSO0917 + 62 showed variations with amplitudes of up to 23% in /similar to/ 24 hours, which were correlated at the two wavelengths; in the BL Lac object 0716 + 71 we found variations with amplitudes of 7-11%. We discuss intrinsic effects, gravitational lensing and scattering in the interstellar medium as possible explanations for rapid radio variability.

  2. Rapid variability of extragalactic radio sources

    International Nuclear Information System (INIS)

    Quirrenbach, A.; Witzel, A.; Krichbaum, T.; Hummel, C.A.; Alberdi, A.; Schalinski, C.

    1989-01-01

    Since its discovery more than 20 years ago, variability of extragalactic radio sources on timescales of weeks to years has been the subject of many investigations. We have examined the variability of these sources on timescales of hours at wavelengths of 6 and 11 cm using the 100-m telescope of the Max-Planck-Institut fuer Radioastronomie and report the results for two sources. The quasar QSO0917 + 62 showed variations with amplitudes of up to 23% in ∼ 24 hours, which were correlated at the two wavelengths; in the BL Lac object 0716 + 71 we found variations with amplitudes of 7-11%. We discuss intrinsic effects, gravitational lensing and scattering in the interstellar medium as possible explanations for rapid radio variability. (author)

  3. Statistical studies of powerful extragalactic radio sources

    Energy Technology Data Exchange (ETDEWEB)

    Macklin, J T

    1981-01-01

    This dissertation is mainly about the use of efficient statistical tests to study the properties of powerful extragalactic radio sources. Most of the analysis is based on subsets of a sample of 166 bright (3CR) sources selected at 178 MHz. The first chapter is introductory and it is followed by three on the misalignment and symmetry of double radio sources. The properties of nuclear components in extragalactic sources are discussed in the next chapter, using statistical tests which make efficient use of upper limits, often the only available information on the flux density from the nuclear component. Multifrequency observations of four 3CR sources are presented in the next chapter. The penultimate chapter is about the analysis of correlations involving more than two variables. The Spearman partial rank correlation coefficient is shown to be the most powerful test available which is based on non-parametric statistics. It is therefore used to study the dependences of the properties of sources on their size at constant redshift, and the results are interpreted in terms of source evolution. Correlations of source properties with luminosity and redshift are then examined.

  4. Fine structure of 25 extragalactic radio sources

    International Nuclear Information System (INIS)

    Wittels, J.J.; Knight, C.A.; Shapiro, I.I.; Hinteregger, H.F.; Rogers, A.E.E.; Whitney, A.R.; Clark, T.A.; Hutton, L.K.; Marandino, G.E.; Neill, A.E.; Ronnang, B.G.; Rydbeck, O.E.H.; Klemperer, W.K.; Warnock, W.W.

    1975-01-01

    Between 1972 April and 1973 May, 25 extragalactic radio sources were observed interferometrically at 7.8 GHz(lambdaapprox. =3.8 cm) with five pairings of antennas. These sources exhibit a broad variety of fine structures from very simple to complex. Although the structure and the total power of some of these sources have remained unchanged within the sensitivity of our measurements during the year of observations, both the total flux and the correlated flux of others have undergone large changes in a few weeks

  5. Reflection jets and collimation of radio sources

    International Nuclear Information System (INIS)

    Pacholczyk, A.G.

    1983-01-01

    The author proposes a description of only a certain class of jets in extended radio sources by discussing hydrodynamics of jets formed by discrete portions of material ejected from the parent galaxy through a channel and reflected back into it as a result of an encounter with the material accumulated at the end of the channel. The picture presented here combines some older ideas with recent ones. The older ideas consist of modeling of extended radio sources in terms of multiple ejection of plasmons through a channel ploughed by the first few plasmons in the ambient medium with a resupply of energy in plasmons through the conversion of bulk kinetic energy into relativistic electron energy through instability driven turbulence. The recent ideas concern the formation of retro-jets as the result of interaction of a plasmon with the dense relic material at the end of a channel and the collimation of plasmon material in channels. (Auth.)

  6. Morphology and power of radio sources

    International Nuclear Information System (INIS)

    Scheuer, P.A.G.

    1982-01-01

    The author discusses two points: 1. Observations suggest that the hot-spots move about either because the beam precesses or more discontinuously, as in sources like 3C351 that have multiple hot-spots. The natural interpretation is that the hot-spot at the end of the beam slides over the inner surface of a 'cavity' filled with very hot dilute ex-hot-spot material, extending the cavity at various places at different times. 2. Most of the radio emission of most really powerful radio sources comes from their hot spots. Contrariwise, straightforward equipartition calculations on models lead to at least as much emission from the 'cavity' as from the hot-spots. (Auth.)

  7. A model for superliminal radio sources

    International Nuclear Information System (INIS)

    Milgrom, M.; Bahcall, J.N.

    1977-01-01

    A geometrical model for superluminal radio sources is described. Six predictions that can be tested by observations are summarized. The results are in agreement with all the available observations. In this model, the Hubble constant is the only numerical parameter that is important in interpreting the observed rates of change of angular separations for small redshifts. The available observations imply that H 0 is less than 55 km/s/Mpc if the model is correct. (author)

  8. Asymmetries in four powerful radio sources

    International Nuclear Information System (INIS)

    Lonsdale, C.J.; Morison, I.

    1983-01-01

    The extragalactic radio sources 3C 153, 196, 249.1 and 268.4 have been observed at frequencies of 408 and 1666 MHz with the new MERLIN array operated by Jodrell Bank, giving resolutions of approx. 0.9 and 0.25 arcsec respectively. The sources show marked asymmetries about the central object in spectral index, flux and morphology, which we believe are most naturally accounted for by the effects of a time-dependent asymmetry in the central powerhouse. In the case of 3C 249.1 the observations suggest that energy is being supplied alternately to the two sides of the source. The 1666-MHz observations also show that each of the other three sources contains one extremely compact hotspot. The minimum internal energy densities in these hotspots are such that confinement by ram pressure of motion through the intergalactic medium may not be possible, indicating that such features are transient phenomena in free expansion, or that some other confinement mechanism is operating. (author)

  9. Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources

    DEFF Research Database (Denmark)

    Aatrokoski, J.; Lähteenmäki, A.; Lavonen, N.

    2011-01-01

    Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30 to 857 GHz......, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase...... of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data...

  10. Brightness distribution data on 2918 radio sources at 365 MHz

    International Nuclear Information System (INIS)

    Cotton, W.D.; Owen, F.N.; Ghigo, F.D.

    1975-01-01

    This paper is the second in a series describing the results of a program attempting to fit models of the brightness distribution to radio sources observed at 365 MHz with the Bandwidth Synthesis Interferometer (BSI) operated by the University of Texas Radio Astronomy Observatory. Results for a further 2918 radio sources are given. An unresolved model and three symmetric extended models with angular sizes in the range 10--70 arcsec were attempted for each radio source. In addition, for 348 sources for which other observations of brightness distribution are published, the reference to the observations and a brief description are included

  11. Physical processes in extragalactic radio sources

    NARCIS (Netherlands)

    Carilli, CL; Perley, R; Harris, DE; Barthel, PD

    This paper summarizes extensive observational studies of the closest ultraluminous radio galaxy Cygnus A. These data are used to test jet theory for powering the double-lobed radio emitting structures. Issues addressed include: (i) jet stability, confinement, composition, and velocity, (ii) the

  12. The importance of source positions during radio fine structure observations

    International Nuclear Information System (INIS)

    Chernov, Guennadi P.; Yan Yi-Hua; Fu Qi-Jun

    2014-01-01

    The measurement of positions and sizes of radio sources in the observations of the fine structure of solar radio bursts is a determining factor for the selection of the radio emission mechanism. The identical parameters describing the radio sources for zebra structures (ZSs) and fiber bursts confirm there is a common mechanism for both structures. It is very important to measure the size of the source in the corona to determine if it is distributed along the height or if it is point-like. In both models of ZSs (the double plasma resonance (DPR) and the whistler model) the source must be distributed along the height, but by contrast to the stationary source in the DPR model, in the whistler model the source should be moving. Moreover, the direction of the space drift of the radio source must correlate with the frequency drift of stripes in the dynamic spectrum. Some models of ZSs require a local source, for example, the models based on the Bernstein modes, or on explosive instability. The selection of the radio emission mechanism for fast broadband pulsations with millisecond duration also depends on the parameters of their radio sources. (mini-volume: solar radiophysics — recent results on observations and theories)

  13. Observational constraints on the cosmological evolution of extragalactic radio sources

    International Nuclear Information System (INIS)

    Perryman, M.A.C.

    1979-11-01

    The thesis discusses statistical studies of the remote radio sources, taking into account the various parameters for such sources, based on data from the various Cambridge Catalogues. Some of the sources have optical counterparts which yield distances from their redshifts. Combining optical and radio observations, an attempt is made to investigate whether large-scale evolution of galaxies occurs as one looks backwards in time to early epochs. Special attention is paid to ensuring that the optical identifications of the selected radio sources are sound and that the selection procedures do not distort the inferences obtained. (U.K.)

  14. H- radio frequency source development at the Spallation Neutron Source.

    Science.gov (United States)

    Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

    2012-02-01

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability of ∼90%. H(-) beam pulses (∼1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ∼60 kW) of a copper antenna that has been encased with a thickness of ∼0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ∼99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ∼75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance∕installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ∼100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

  15. A CLUSTER OF COMPACT RADIO SOURCES IN W40

    International Nuclear Information System (INIS)

    RodrIguez, Luis F.; Rodney, Steven A.; Reipurth, Bo

    2010-01-01

    We present deep 3.6 cm radio continuum observations of the H II region W40 obtained using the Very Large Array (VLA) in its A and B configurations. We detect a total of 20 compact radio sources in a region of 4' x 4', with 11 of them concentrated in a band with 30'' of extent. We also present JHK photometry of the W40 cluster taken with the QUIRC instrument on the University of Hawaii 2.2 m telescope. These data reveal that 15 of the 20 VLA sources have infrared counterparts, and 10 show radio variability with periods less than 20 days. Based on these combined radio and IR data, we propose that eight of the radio sources are candidate ultracompact H II regions, seven are likely to be young stellar objects, and two may be shocked interstellar gas.

  16. Planck Early Results. XV. Spectral Energy Distributions and Radio Continuum Spectra of Northern Extragalactic Radio Sources

    Science.gov (United States)

    Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; hide

    2011-01-01

    Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources. based on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multi frequency data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed, with an emphasis on proper. physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shock. Furthermore in many cases the Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission.

  17. THE DYNAMIC EVOLUTION OF YOUNG EXTRAGALACTIC RADIO SOURCES

    International Nuclear Information System (INIS)

    An Tao; Baan, Willem A.

    2012-01-01

    The evolution of symmetric extragalactic radio sources can be characterized by four distinct growth stages of the radio luminosity versus size of the source. The interaction of the jet with the ambient medium results in the formation and evolution of sources with non-standard (flaring) morphology. In addition, cessation or restarting of the jet power and obstruction of the jet will also result in distinct morphological structures. The radio source population may thus be classified in morphological types that indicate the prevailing physical processes. Compact symmetric objects (CSOs) occupy the earliest evolutionary phase of symmetric radio sources and their dynamical behavior is fundamental for any further evolution. Analysis of CSO dynamics is presented for a sample of 24 CSOs with known redshift and hotspot separation velocity and with a large range of radio power. Observables such as radio power, separation between two hotspots, hotspot separation velocity, and kinematic age of the source are found to be generally consistent with the self-similar predictions for individual sources that reflect the varying density structure of the ambient interstellar medium. Individual sources behave different from the group as a whole. The age and size statistics confirm that a large fraction of CSOs does not evolve into extended doubles.

  18. THE DYNAMIC EVOLUTION OF YOUNG EXTRAGALACTIC RADIO SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    An Tao [Shanghai Astronomical Observatory, Chinese Academy of Sciences, 200030 Shanghai (China); Baan, Willem A., E-mail: antao@shao.ac.cn, E-mail: baan@astron.nl [ASTRON, P.O. Box 2, 7990-AA Dwingeloo (Netherlands)

    2012-11-20

    The evolution of symmetric extragalactic radio sources can be characterized by four distinct growth stages of the radio luminosity versus size of the source. The interaction of the jet with the ambient medium results in the formation and evolution of sources with non-standard (flaring) morphology. In addition, cessation or restarting of the jet power and obstruction of the jet will also result in distinct morphological structures. The radio source population may thus be classified in morphological types that indicate the prevailing physical processes. Compact symmetric objects (CSOs) occupy the earliest evolutionary phase of symmetric radio sources and their dynamical behavior is fundamental for any further evolution. Analysis of CSO dynamics is presented for a sample of 24 CSOs with known redshift and hotspot separation velocity and with a large range of radio power. Observables such as radio power, separation between two hotspots, hotspot separation velocity, and kinematic age of the source are found to be generally consistent with the self-similar predictions for individual sources that reflect the varying density structure of the ambient interstellar medium. Individual sources behave different from the group as a whole. The age and size statistics confirm that a large fraction of CSOs does not evolve into extended doubles.

  19. Nasu 1.4 GHz Interferometer Transient Radio Source Survey and Improvement in Detection of Radio Sources

    International Nuclear Information System (INIS)

    Matsumura, Nobuo; Kuniyoshi, Masaya; Takefuji, Kazuhiro; Niinuma, Kotaro; Kida, Sumiko; Takeuchi, Akihiko; Asuma, Kuniyuki; Daishido, Tsuneaki

    2006-01-01

    We have surveyed 1.4GHz transient radio sources in Nasu Pulsar Observatory. To investigate such sources, both immediacy and accuracy are severely maintained. We have developed Data Transfer System and improved antenna control system. Now we have received the fringe data from transient radio source candidates. To get reliable information, we carefully analyze with Fringe Band Pass Filter software and Fringe Fitting method

  20. Optical identifications of flat-spectrum radio sources

    International Nuclear Information System (INIS)

    Condon, J.J.; Condon, M.A.; Broderick, J.J.; Davis, M.M.

    1983-01-01

    A complete sample of radio sources with S> or =0.3 Jy at 1400 MHz, +24 0 0 , and low-frequency spectral indices α(408, 1400) or =+0.5 are usually in empty fields. The lower limits that can be assigned to the radio-optical spectral indices α/sub RO/ of these sources are significantly higher than the median α/sub RO/ of the sources with flat high-frequency spectra, so the optical characteristics of the two classes of radio source are intrinsically different. The radio and optical fluxes of flat-spectrum QSO's appear to be correlated, at least when averaged over 10 2 --10 3 yr

  1. A new sample of faint Gigahertz Peaked Spectrum radio sources

    NARCIS (Netherlands)

    Snellen, IAG; Schilizzi, RT; de Bruyn, AG; Miley, GK; Rengelink, RB; Rottgering, HJ

    The Westerbork Northern Sky Survey (WENSS) has been used to select a sample of Gigahertz Peaked Spectrum (GPS) radio sources at flux densities one to two orders of magnitude lower than bright GPS sources investigated in earlier studies. Sources with inverted spectra at frequencies above 325 MHz have

  2. Polarimetry of the Fast Radio Burst Source FRB121102

    Science.gov (United States)

    Michilli, Daniele; Seymour, Andrew; Hessels, Jason W. T.; Spitler, Laura; Gajjar, Vishal; Archibald, Anne; Bower, Geoffrey C.; Chatterjee, Shami; Cordes, Jim; Gourdji, Kelly; Heald, George; Kaspi, Victoria; Law, Casey; Sobey, Charlotte

    2018-01-01

    Fast radio bursts (FRBs) are millisecond-duration radio flashes of presumably extragalactic origin. FRB121102 is the only FRB known to repeat and the only one with a precise localization. It is co-located with a persistent radio source inside a star-forming region in a dwarf galaxy at z=0.2. While the persistent source is compatible with either a low-luminosity accreting black hole or a very energetic nebula and supernova remnant, the source of the bursts is still a mystery. We present new bursts from FRB121102 detected at relatively high radio frequencies of ~5GHz. These observations allow us to investigate the polarization properties of the bursts, placing new constraints on the environment of FRB121102.

  3. 4C radio sources in clusters of galaxies

    International Nuclear Information System (INIS)

    McHardy, I.M.

    1979-01-01

    Observations of a complete sample of 4C and 4CT radio sources in Abell clusters with the Cambridge One-Mile telescope are analysed. It is concluded that radio sources are strongly concentrated towards the cluster centres and are equally likely to be found in clusters of any richness. The probability of a galaxy of a given absolute magnitude producing a source above a given luminosity does not depend on cluster membership. 4C and 4CT radio sources in clusters, selected at 178 MHz, occur preferentially in Bautz-Morgan (BM) class 1 clusters, whereas those selected at 1.4 GHz do not. The most powerful radio source in the cluster is almost always associated with the optically brightest galaxy. The average spectrum of 4C sources in the range 408 to 1407 MHz is steeper in BM class 1 than in other classes. Spectra also steepen with cluster richness. the morphology of 4C sources in clusters depends strongly on BM class and, in particular, radio-trail sources occur only in BM classes II, II-III and III. (author)

  4. Hot-spots of radio sources in clusters of galaxies

    International Nuclear Information System (INIS)

    Saikia, D.J.

    1979-01-01

    A sample of extragalactic double radio sources is examined to test for a correlation between the prominence of compact hot-spots located at their outer edges and membership of clusters of galaxies. To minimize the effects of incompleteness in published catalogues of clusters, cluster classification is based on the number of galaxies in the neighbourhood of each source. After eliminating possible selection effects, it is found that sources in regions of high galactic density tend to have less prominent hot-spots. It is argued that the result is consistent with the 'continuous-flow' models of radio sources, but poses problems for the gravitational slingshot model. (author)

  5. Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

    Science.gov (United States)

    Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

    2018-04-01

    We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

  6. Compact continuum radio sources in the Orion Nebula

    International Nuclear Information System (INIS)

    Garay, G.; Moran, J.M.; Reid, M.J.; European Southern Observatory, Garching, West Germany)

    1987-01-01

    The Orion Nebula was observed with the VLA in order to search for radio emission from compact H II regions indicative of embedded OB stars or from winds associated with pre-main sequence, low-mass stars. Fourteen of the 21 detected radio sources are within 30 arcsec of Omega 1 Orionis C; 13 of these objects are probably neutral condensations surrounded by ionized envelopes that are excited by the star. If the temperature of the ionized envelopes is 10,000 K and their electron densities decrease as the square of the distance from the core center, then a typical neutral condensation has a radius of 10 to the 15th cm and a peak electron density of 400,000/cu cm. Seven sources are in or near the Orion molecular cloud. Four of the sources have optical counterparts. Two are highly variable radio sources associated with X-ray sources, and two have radio spectra indicative of thermal emission. Two of the three optically invisible sources have radio emission likely to arise in a dense ionized envelope surrounding and excited by an early B-type star. 46 references

  7. Bending of electromagnetic beams and head-tail radio sources

    Energy Technology Data Exchange (ETDEWEB)

    Bodo, G; Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Ist. di Fisica)

    1981-08-01

    An interpretation is presented of bridge bending in head-tail radio sources in the framework of an electromagnetic beam model. The physical effect responsible for the structural distortion is proposed to be the refraction of a large-amplitude wave in a medium with a density gradient perpendicular to the wave propagation vector; this gradient is consistently produced by the relative motion of the beam source in the surrounding medium with a velocity higher than the speed of sound. These effects are calculated in some detail and a quantitative fit of model parameters to the typical radio source associated with NGC 1265 is discussed.

  8. Bending of electromagnetic beams and head-tail radio sources

    International Nuclear Information System (INIS)

    Bodo, G.; Ferrari, A.; Massaglia, S.; Turin Univ.

    1981-01-01

    An interpretation is presented of bridge bending in head-tail radio sources in the framework of an electromagnetic beam model. The physical effect responsible for the structural distortion is proposed to be the refraction of a large-amplitude wave in a medium with a density gradient perpendicular to the wave propagation vector; this gradient is consistently produced by the relative motion of the beam source in the surrounding medium with a velocity higher than the speed of sound. These effects are calculated in some detail and a quantitative fit of model parameters to the typical radio source associated with NGC 1265 is discussed. (author)

  9. Comparison of VLBI radio core and X-ray flux densities of extragalactic radio sources

    International Nuclear Information System (INIS)

    Bloom, S.D.; Marscher, A.P.

    1990-01-01

    The Einstein Observatory revealed that most quasars, selected in a variety of ways, are strong x-ray emitters. Radio bright quasars are statistically more luminous in the x-ray than their radio-quiet counterparts. It was also found that the 90 GHz to soft x-ray spectral index has a very small dispersion for sources selected by their strong millimeter emission. This implies a close relationship between compact radio flux density and x-ray emission. Strong correlations have been found between the arcsecond scale flux densities and soft x-ray fluxes. It is suggested that the correlation can be explained if the soft x-rays were produced by the synchrotron self-Compton (SSC) process within the compact radio emitting region. (author)

  10. Spectral Index Properties of millijansky Radio Sources in ATLAS

    Science.gov (United States)

    Randall, Kate; Hopkins, A. M.; Norris, R. P.; Zinn, P.; Middelberg, E.; Mao, M. Y.; Sharp, R. G.

    2012-01-01

    At the faintest radio flux densities (S1.4GHz 10 mJy) is well studied and is predominantly comprised of AGN. At fainter flux densities, particularly into the microJansky regime, star-forming galaxies begin to dominate the radio source population. Understanding these faint radio source populations is essential for understanding galaxy evolution, and the link between AGN and star formation. Conflicting results have recently arisen regarding whether there is a flattening of the average spectral index between a low radio frequency (325 or 610 MHz) and 1.4 GHz at these faint flux densities. To explore this issue, we have investigated the spectral index properties of a new catalogue of 843 MHz radio sources in the ELAIS-S1 (the European Large Area ISO Survey - South 1 Region) field. Our results support previous work showing a tendency towards flatter radio spectra at fainter flux densities. This catalogue is cross-matched to the Australia Telescope Large Area Survey (ATLAS), the widest deep radio survey to date at 1.4 GHz, with complementary 2.3 GHz, optical and infrared Spitzer Wide-area Infra-Red Extragalactic data. The variation of spectral index properties have been explored as a function of redshift, luminosity and flux density. [These new measurements have been used to identify a population of faint Compact Steep Spectrum sources, thought to be one of the earliest stages of the AGN life-cycle. Exploring this population will aid us in understanding the evolution of AGN as a whole.

  11. Radio-isotope powered light source

    International Nuclear Information System (INIS)

    Spottiswoode, N.L.; Ryden, D.J.

    1979-01-01

    The light source described comprises a radioisotope fuel source, thermal insulation against heat loss, a biological shield against the escape of ionizing radiation and a material having a surface which attains incandescence when subject to isotope decay heat. There is then a means for transferring this heat to produce incandescence of the surface and thus emit light. A filter associated with the surface permits a relatively high transmission of visible radiation but has a relatively high reflectance in the infra red spectrum. Such light sources require the minimum of attention and servicing and are therefore suitable for use in navigational aids such as lighthouses and lighted buoys. The isotope fuel sources and thus the insulation and shielding and the incandescent material can be chosen for the use required and several sources, materials, means of housing etc. are detailed. Operation and efficiency are discussed. (U.K.)

  12. Earth as a radio source: terrestrial kilometric radiation. Progress report

    International Nuclear Information System (INIS)

    Gurnett, D.A.

    1974-02-01

    Radio wave experiments on the IMP-6 and 8 satellites have shown that the earth emits very intense electromagnetic radiation in the frequency range from about 50 kHz to 500 kHz. A peak intensity the total power emitted in this frequency range is about 1 billion watts. The earth is, therefore, a very intense planetary radio source, with a total power output comparable to the decametric radio emission from Jupiter. This radio emission from the earth is referred to as terrestrial kilometric radiation. Terrestrial kilometric radiation appears to originate from low altitudes (less than 3.0 Re) in the auroral region. Possible mechanisms which can explain the generation and propagation of the terrestrial kilometric radiation are discussed. (U.S.)

  13. Changing-Look AGNs or Short-Lived Radio Sources?

    Energy Technology Data Exchange (ETDEWEB)

    Wołowska, Aleksandra [Toruń Centre for Astronomy, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń (Poland); Kunert-Bajraszewska, Magdalena; Mooley, Kunal [Centre for Astrophysical Surveys, University of Oxford, Oxford (United Kingdom); Hallinan, Gregg, E-mail: ola@astro.umk.pl [Cahill Center for Astronomy, California Institute of Technology, Pasadena, CA (United States)

    2017-11-17

    The evolution of extragalactic radio sources has been a fundamental problem in the study of active galactic nuclei for many years. A standard evolutionary model has been created based on observations of a wide range of radio sources. In the general scenario of the evolution, the younger and smaller Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources become large-scale FRI and FRII objects. However, a growing number of observations of low power radio sources suggests that the model cannot explain all their properties and there are still some aspects of the evolutionary path that remain unclear. There are indications, that some sources may be short-lived objects on timescales of 10{sup 4}–10{sup 5} years. Those objects represent a new population of active galaxies. Here, we present the discovery of several radio transient sources on timescales of 5–20 yrs, largely associated with renewed AGN (Active Galactic Nucleus) activity. These changing-look AGNs possibly represent behavior typical for many active galaxies.

  14. Rotationally symmetric structure in two extragalactic radio sources

    International Nuclear Information System (INIS)

    Lonsdale, C.J.; Morison, I.

    1980-01-01

    The new multi-telescope radio-linked interferometer (MTRLI) at Jodrell Bank was used during January and February 1980 at a frequency of 408 MHz to map the extragalactic radio sources 3C196 and 3C305 with a resolution of approximately 1 arc s. It is shown here that both the markedly symmetric structures observed and the spectral index distributions inferred from comparisons with previously published 5 GHz maps provide evidence for the source axes having rotated during the lifetime of the emitting regions. (U.K.)

  15. The psisub(IPS)-LAS relation for extragalactic radio sources

    International Nuclear Information System (INIS)

    Banhatti, D.G.

    1984-01-01

    Metre-wavelength interplanetary scintillation (IPS) observations give the overall angular sizes psi of scintillating compact structures in radio sources. From 326.5-MHz IPS data for a sample of faint (Ooty) radio sources, log psi versus log (largest angular size) is seen, on average, to have a slope 0.2, significantly less than one. A similar trend is seen from 81.5-MHz IPS data for a sample of strong, powerful (3CR) double sources, although the slope is 0.4 and the mean psi about four times larger. The difference in slopes is due mainly to the large spread in the redshifts of the 3CR sources compared to the expected narrow range for the Ooty sources, while the difference in mean psi values is due to the different methods of determining psi for the two samples, the different frequencies used for the IPS observations and the different mean LAS values. (author)

  16. Planck intermediate results: XLV. Radio spectra of northern extragalactic radio sources

    DEFF Research Database (Denmark)

    Ade, P. A R; Aghanim, N.; Aller, H. D.

    2016-01-01

    Continuum spectra covering centimetre to submillimetre wavelengths are presented for a northern sample of 104 extragalactic radio sources, mainly active galactic nuclei, based on four-epoch Planck data. The nine Planck frequencies, from 30 to 857 GHz, are complemented by a set of simultaneous gro...

  17. Plasma phenomenology in astrophysical systems: Radio-sources and jets

    International Nuclear Information System (INIS)

    Montani, Giovanni; Petitta, Jacopo

    2014-01-01

    We review the plasma phenomenology in the astrophysical sources which show appreciable radio emissions, namely Radio-Jets from Pulsars, Microquasars, Quasars, and Radio-Active Galaxies. A description of their basic features is presented, then we discuss in some details the links between their morphology and the mechanisms that lead to the different radio-emissions, investigating especially the role played by the plasma configurations surrounding compact objects (Neutron Stars, Black Holes). For the sake of completeness, we briefly mention observational techniques and detectors, whose structure set them apart from other astrophysical instruments. The fundamental ideas concerning angular momentum transport across plasma accretion disks—together with the disk-source-jet coupling problem—are discussed, by stressing their successes and their shortcomings. An alternative scenario is then inferred, based on a parallelism between astrophysical and laboratory plasma configurations, where small-scale structures can be found. We will focus our attention on the morphology of the radio-jets, on their coupling with the accretion disks and on the possible triggering phenomena, viewed as profiles of plasma instabilities

  18. BROADBAND RADIO POLARIMETRY AND FARADAY ROTATION OF 563 EXTRAGALACTIC RADIO SOURCES

    International Nuclear Information System (INIS)

    Anderson, C. S.; Gaensler, B. M.; Feain, I. J.; Franzen, T. M. O.

    2015-01-01

    We present a broadband spectropolarimetric survey of 563 discrete, mostly unresolved radio sources between 1.3 and 2.0 GHz using data taken with the Australia Telescope Compact Array. We have used rotation-measure synthesis to identify Faraday-complex polarized sources, those objects whose frequency-dependent polarization behavior indicates the presence of material possessing complicated magnetoionic structure along the line of sight (LOS). For sources classified as Faraday-complex, we have analyzed a number of their radio and multiwavelength properties to determine whether they differ from Faraday-simple polarized sources (sources for which LOS magnetoionic structures are comparatively simple) in these properties. We use this information to constrain the physical nature of the magnetoionic structures responsible for generating the observed complexity. We detect Faraday complexity in 12% of polarized sources at ∼1′ resolution, but we demonstrate that underlying signal-to-noise limitations mean the true percentage is likely to be significantly higher in the polarized radio source population. We find that the properties of Faraday-complex objects are diverse, but that complexity is most often associated with depolarization of extended radio sources possessing a relatively steep total intensity spectrum. We find an association between Faraday complexity and LOS structure in the Galactic interstellar medium (ISM) and claim that a significant proportion of the Faraday complexity we observe may be generated at interfaces of the ISM associated with ionization fronts near neutral hydrogen structures. Galaxy cluster environments and internally generated Faraday complexity provide possible alternative explanations in some cases

  19. Variability of GPS Radio Sources at 5 GHz

    Indian Academy of Sciences (India)

    GPS) radio sources at 5 GHz and find that about one-third of them show considerable Inter-Month Variability (IMV), and these IMV phenomena are likely to be caused by interstellar scintillation (ISS). Furthermore, we find that those showing IMV ...

  20. Where does particle acceleration occur in extended extragalactic radio sources

    International Nuclear Information System (INIS)

    Hughes, P.A.

    1980-01-01

    It is suggested that particle acceleration does not occur in the extended lobes of extragalactic radio sources, but only in the compact heads. Away from these, waves capable of accelerating particles may not propagate. Although wave generation within the lobes would allow acceleration there, it is not obvious that the plasma is sufficiently disturbed for this to occur. (author)

  1. Planck early results. XIV. ERCSC validation and extreme radio sources

    DEFF Research Database (Denmark)

    Lähteenmäki, A.; Lavonen, N.; León-Tavares, J.

    2011-01-01

    Planck's all-sky surveys at 30-857 GHz provide an unprecedented opportunity to follow the radio spectra of a large sample of extragalactic sources to frequencies 2-20 times higher than allowed by past, large-area, ground-based surveys. We combine the results of the Planck Early Release Compact So...

  2. Probing the bias of radio sources at high redshift

    CSIR Research Space (South Africa)

    Passmoor, S

    2012-11-01

    Full Text Available The relationship between the clustering of dark matter and that of luminous matter is often described using the bias parameter. Here, we provide a new method to probe the bias of intermediate-to-high-redshift radio continuum sources for which...

  3. Fundamental limits of radio interferometers: calibration and source parameter estimation

    OpenAIRE

    Trott, Cathryn M.; Wayth, Randall B.; Tingay, Steven J.

    2012-01-01

    We use information theory to derive fundamental limits on the capacity to calibrate next-generation radio interferometers, and measure parameters of point sources for instrument calibration, point source subtraction, and data deconvolution. We demonstrate the implications of these fundamental limits, with particular reference to estimation of the 21cm Epoch of Reionization power spectrum with next-generation low-frequency instruments (e.g., the Murchison Widefield Array -- MWA, Precision Arra...

  4. Radio Galaxy Zoo: Machine learning for radio source host galaxy cross-identification

    Science.gov (United States)

    Alger, M. J.; Banfield, J. K.; Ong, C. S.; Rudnick, L.; Wong, O. I.; Wolf, C.; Andernach, H.; Norris, R. P.; Shabala, S. S.

    2018-05-01

    We consider the problem of determining the host galaxies of radio sources by cross-identification. This has traditionally been done manually, which will be intractable for wide-area radio surveys like the Evolutionary Map of the Universe (EMU). Automated cross-identification will be critical for these future surveys, and machine learning may provide the tools to develop such methods. We apply a standard approach from computer vision to cross-identification, introducing one possible way of automating this problem, and explore the pros and cons of this approach. We apply our method to the 1.4 GHz Australian Telescope Large Area Survey (ATLAS) observations of the Chandra Deep Field South (CDFS) and the ESO Large Area ISO Survey South 1 (ELAIS-S1) fields by cross-identifying them with the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. We train our method with two sets of data: expert cross-identifications of CDFS from the initial ATLAS data release and crowdsourced cross-identifications of CDFS from Radio Galaxy Zoo. We found that a simple strategy of cross-identifying a radio component with the nearest galaxy performs comparably to our more complex methods, though our estimated best-case performance is near 100 per cent. ATLAS contains 87 complex radio sources that have been cross-identified by experts, so there are not enough complex examples to learn how to cross-identify them accurately. Much larger datasets are therefore required for training methods like ours. We also show that training our method on Radio Galaxy Zoo cross-identifications gives comparable results to training on expert cross-identifications, demonstrating the value of crowdsourced training data.

  5. Properties of Radio Sources in the FRB 121102 Field

    Science.gov (United States)

    Bower, Geoffrey C.; Chatterjee, Shami; Wharton, Robert; Law, Casey J.; Hessels, Jason; Spolaor, Sarah; Abruzzo, Matthew W.; Bassa, Cees; Butler, Bryan J.; Cordes, James M.; Demorest, Paul; Kaspi, Victoria M.; McLaughlin, Maura; Ransom, Scott M.; Scholz, Paul; Seymour, Andrew; Spitler, Laura; Tendulkar, Shriharsh P.; PALFA Survey; VLA+AO FRB121102 Simultaneous Campaign Team; EVN FRB121102 Campaign Team; Realfast Team

    2017-01-01

    Fast radio bursts are millisecond duration radio pulses of unknown origin. With dispersion measures substantially in excess of expected Galactic contributions, FRBs are inferred to originate extragalactically, implying very high luminosities. Models include a wide range of high energy systems such as magnetars, merging neutron star binaries, black holes, and strong stellar magnetic fields driving coherent radio emission. Central to the mystery of FRB origins are the absence of confirmed host objects at any wavelength. This is primarily the result of the poor localization from single dish detection of FRBs. Of the approximately 20 known examples, only one, FRB 121102, has been observed to repeat. This repetition presents an opportunity for detailed follow-up if interferometric localization to arcsecond accuracy can be obtained. The Very Large Array has previously been used to localize individual pulses from pulsars and rotating radio transients to arcsecond localizaiton. We present here the results of radio observations of the field of FRB 121102 that permit us to constrain models of possible progenitors of this bursting source. These observations can characterize active galactic nuclei, stars, and other progenitor objects.

  6. Giant Double Radio Source DA 240: Purveyor of Galaxies

    Science.gov (United States)

    Chen, Ru-Rong; Strom, Richard; Peng, Bo

    2018-05-01

    Galaxies of stars are building blocks of the baryonic universe. Their composition, structure, and kinematics have been well studied, but details of their origins remain sketchy. The collapse of gas clouds, induced by external forces whereby gravity overcomes internal pressure to form stars, is the likely starting point. Among the perturbing initiators of galaxy formation, radio source beams (jets) are quite effective. Typically, a beam may spawn one galaxy, though instances of several aligned with the radio axis are known. Recently, we found an impressive 14 companions in the lobes of the giant radio galaxy DA 240, which we argue formed as the result of jet instigation. This conclusion is bolstered by the fact that the galaxy groups display Z-shaped symmetry with respect to the radio axis. There is some evidence for star formation among the aligned companions. We also conclude that galaxy alignments at low redshift may derive from line-emitting gas observed in radio components of high-redshift galaxies.

  7. Problem of spiral galaxies and satellite radio sources

    International Nuclear Information System (INIS)

    Arp, H.; Carpenter, R.; Gulkis, S.; Klein, M.

    1976-01-01

    A detailed comparison is made between the results of this program and the results of previous investigators. In particular, attention is called to the potentially important implications of an investigation by Tovmasyan, who searched a large number of spirals and found evidence that a small percentage of them apparently have radio satellites located up to 20' from the central galaxy. 15 sources were measured selected from Tovmasyan's list of 43 satellite sources. Results confirm his positions and relative flux densities for each of the sources

  8. Radio identifications of IRAS point sources with b greater than 30 deg

    International Nuclear Information System (INIS)

    Condon, J.J.; Broderick, J.J.; Virginia Polytechnic Institute and State Univ., Blacksburg)

    1986-01-01

    The present radio identifications of IRAS point sources on the basis of Green Bank 1400 MHz survey maps notes that 365 hot IR sources are not detectable radio sources, and that nearly all cool high latitude IRAS sources are extragalactic. The fainter IR-source identifications encompass optically bright quasars, BL Lac objects, Seyfert galaxies, and elliptical galaxies. No IRAS sources could be identified with distant elliptical radio galaxies, so that although the radio and IR fluxes of most IRAS extragalactic sources are tightly correlated, complete samples of strong radio and IR sources are almost completely disjoint; no more than 1 percent of the IR sources are radio sources and less than 1 percent of the radio sources are IR ones. 35 references

  9. Cosmology from angular size counts of extragalactic radio sources

    International Nuclear Information System (INIS)

    Kapahi, V.K.

    1975-01-01

    The cosmological implications of the observed angular sizes of extragalactic radio sources are investigated using (i) the log N-log theta relation, where N is the number of sources with an angular size greater than a value theta, for the complete sample of 3CR sources, and (ii) the thetasub(median) vs flux density (S) relation derived from the 3CR, the All-sky, and the Ooty occulation surveys, spanning a flux density range of about 300:1. The method of estimating the expected N(theta) and thetasub(m)(S) relations for a uniform distribution of sources in space is outlined. Since values of theta>approximately 100second arc in the 3C sample arise from sources of small z, the slope of the N(theta) relation in this range is practically independent of the world model and the distribution of source sizes, but depends strongly on the radio luminosity function (RLF). From the observed slope the RLF is derived in the luminosity range of about 10 23 178 26 W Hz -1 sr -1 to be of the form rho(P)dP proportional to Psup(-2.1)dP. It is shown that the angular size data provide independent evidence of evolution in source properties with epoch. It is difficult to explain the data with the simple steady-state theory even if identified QSOs are excluded from ths source samples and a local deficiency of strong source is postulated. The simplest evolutionary scheme that fits the data in the Einstein-de Sitter cosmology indicates that (a) the local RLF steepens considerably at high luminosities, (b) the comoving density of high luminosity sources increases with z in a manner similar to that implied by the log N-log S data and by the V/Vsub(m) test for QSOs, and (c) the mean physical sizes of radio sources evolve with z approximately as (1+z) -1 . Similar evolutionary effects appear to be present for QSOs as well as radio galaxies. (author)

  10. PySE: Software for extracting sources from radio images

    Science.gov (United States)

    Carbone, D.; Garsden, H.; Spreeuw, H.; Swinbank, J. D.; van der Horst, A. J.; Rowlinson, A.; Broderick, J. W.; Rol, E.; Law, C.; Molenaar, G.; Wijers, R. A. M. J.

    2018-04-01

    PySE is a Python software package for finding and measuring sources in radio telescope images. The software was designed to detect sources in the LOFAR telescope images, but can be used with images from other radio telescopes as well. We introduce the LOFAR Telescope, the context within which PySE was developed, the design of PySE, and describe how it is used. Detailed experiments on the validation and testing of PySE are then presented, along with results of performance testing. We discuss some of the current issues with the algorithms implemented in PySE and their interaction with LOFAR images, concluding with the current status of PySE and its future development.

  11. The rotation measures of radio sources and their interpretation

    International Nuclear Information System (INIS)

    Vallee, J.P.; Kronberg, P.P.

    1975-01-01

    Rotation measures of 251 discrete radio sources have been determined after incorporating new polarization data at short wavelenghts. These have been applied to a 'slab' model-fitting technique to determine the most likely spiral arm magnetic field structure. The best agreement is obtained for a longitudinal spiral arm magnetic field, directed toward (lII approximately 90 0 , bII approximately 0 0 ), but perturbed by an anomaly towards the North Galactic Spur. (orig.) [de

  12. Degree of polarization and source counts of faint radio sources from Stacking Polarized intensity

    International Nuclear Information System (INIS)

    Stil, J. M.; George, S. J.; Keller, B. W.; Taylor, A. R.

    2014-01-01

    We present stacking polarized intensity as a means to study the polarization of sources that are too faint to be detected individually in surveys of polarized radio sources. Stacking offers not only high sensitivity to the median signal of a class of radio sources, but also avoids a detection threshold in polarized intensity, and therefore an arbitrary exclusion of sources with a low percentage of polarization. Correction for polarization bias is done through a Monte Carlo analysis and tested on a simulated survey. We show that the nonlinear relation between the real polarized signal and the detected signal requires knowledge of the shape of the distribution of fractional polarization, which we constrain using the ratio of the upper quartile to the lower quartile of the distribution of stacked polarized intensities. Stacking polarized intensity for NRAO VLA Sky Survey (NVSS) sources down to the detection limit in Stokes I, we find a gradual increase in median fractional polarization that is consistent with a trend that was noticed before for bright NVSS sources, but is much more gradual than found by previous deep surveys of radio polarization. Consequently, the polarized radio source counts derived from our stacking experiment predict fewer polarized radio sources for future surveys with the Square Kilometre Array and its pathfinders.

  13. The Compact Radio Sources in the Nucleus of NGC 1068

    Science.gov (United States)

    Roy, A. L.; Colbert, E. J. M.; Wilson, A. S.; Ulvestad, J. S.

    1998-09-01

    We report VLBA images of the nucleus of the Seyfert galaxy NGC 1068 at 1.7, 5, and 15 GHz, with resolutions between 3 and 10 mas (0.2-0.7 pc) and a sensitivity of ~106 K at all three frequencies. Our goals are to study the morphology of the radio emission at subparsec resolution and to investigate thermal gas in the putative obscuring disk or torus and in the narrow-line region clouds through free-free absorption of the radio emission. All four known radio components in the central arcsecond (S2, S1, C, and NE, from south to north) have been detected at either 1.7 or 5 GHz, or both. No radio emission was detected at 15 GHz. Component S1 is probably associated with the active nucleus, with radio emission originating from the inner edge of the obscuring torus according to Gallimore et al. Our observed flux densities at 1.7 and 5 GHz are in agreement with their thermal bremsstrahlung emission model, and we find that the nuclear radiation may be strong enough to heat the gas in S1 to the required temperature of ~4 × 106 K. The bremsstrahlung power would be 0.15(frefl/0.01) times the bolometric luminosity of the nucleus between 1014.6 and 1018.4 Hz (where frefl is the fraction of radiation reflected into our line of sight by the electron-scattering mirror) and so the model is energetically reasonable. We also discuss two other models for S1 that also match the observed radio spectrum: electron scattering by the torus of radio emission from a compact synchrotron self-absorbed source and synchrotron radiation from the torus itself. Components NE and S2 have spectra consistent with optically thin synchrotron emission, without significant absorption. Both of these components are elongated roughly perpendicular to the larger scale radio jet, suggesting that their synchrotron emission is related to transverse shocks in the jet or to bow shocks in the external medium. Component C has a nonthermal spectrum absorbed at low frequency. This absorption is consistent with free

  14. A young source of optical emission from distant radio galaxies.

    Science.gov (United States)

    Hammer, F; Fèvre, O Le; Angonin, M C

    1993-03-25

    DISTANT radio galaxies provide valuable insights into the properties of the young Universe-they are the only known extended optical sources at high redshift and might represent an early stage in the formation and evolution of galaxies in general. This extended optical emission often has very complex morphologies, but the origin of the light is still unclear. Here we report spectroscopic observations for several distant radio galaxies (0.75≤ z ≤ 1.1) in which the rest-frame spectra exhibit featureless continua between 2,500 Å and 5,000 Å. We see no evidence for the break in the spectrum at 4,000 Å expected for an old stellar population 1-3 , and suggest that young stars or scattered emissions from the active nuclei are responsible for most of the observed light. In either case, this implies that the source of the optical emission is com-parable in age to the associated radio source, namely 10 7 years or less.

  15. Extragalactic Peaked-spectrum Radio Sources at Low Frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Callingham, J. R.; Gaensler, B. M.; Sadler, E. M.; Lenc, E. [Sydney Institute for Astronomy (SIfA), School of Physics, The University of Sydney, NSW 2006 (Australia); Ekers, R. D.; Bell, M. E. [CSIRO Astronomy and Space Science (CASS), Marsfield, NSW 2122 (Australia); Line, J. L. B.; Hancock, P. J.; Kapińska, A. D.; McKinley, B.; Procopio, P. [ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO) (Australia); Hurley-Walker, N.; Tingay, S. J.; Franzen, T. M. O.; Morgan, J. [International Centre for Radio Astronomy Research (ICRAR), Curtin University, Bentley, WA 6102 (Australia); Dwarakanath, K. S. [Raman Research Institute (RRI), Bangalore 560080 (India); For, B.-Q. [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia); Hindson, L.; Johnston-Hollitt, M. [School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140 (New Zealand); Offringa, A. R., E-mail: joseph.callingham@sydney.edu.au [Netherlands Institute for Radio Astronomy (ASTRON), Dwingeloo (Netherlands); and others

    2017-02-20

    We present a sample of 1483 sources that display spectral peaks between 72 MHz and 1.4 GHz, selected from the GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey. The GLEAM survey is the widest fractional bandwidth all-sky survey to date, ideal for identifying peaked-spectrum sources at low radio frequencies. Our peaked-spectrum sources are the low-frequency analogs of gigahertz-peaked spectrum (GPS) and compact-steep spectrum (CSS) sources, which have been hypothesized to be the precursors to massive radio galaxies. Our sample more than doubles the number of known peaked-spectrum candidates, and 95% of our sample have a newly characterized spectral peak. We highlight that some GPS sources peaking above 5 GHz have had multiple epochs of nuclear activity, and we demonstrate the possibility of identifying high-redshift ( z > 2) galaxies via steep optically thin spectral indices and low observed peak frequencies. The distribution of the optically thick spectral indices of our sample is consistent with past GPS/CSS samples but with a large dispersion, suggesting that the spectral peak is a product of an inhomogeneous environment that is individualistic. We find no dependence of observed peak frequency with redshift, consistent with the peaked-spectrum sample comprising both local CSS sources and high-redshift GPS sources. The 5 GHz luminosity distribution lacks the brightest GPS and CSS sources of previous samples, implying that a convolution of source evolution and redshift influences the type of peaked-spectrum sources identified below 1 GHz. Finally, we discuss sources with optically thick spectral indices that exceed the synchrotron self-absorption limit.

  16. Determination of the properties of magnetic turbulence in radio sources

    International Nuclear Information System (INIS)

    Spangler, S.R.

    1983-01-01

    We have considered the transport of polarized synchrotron radiation in a source possessing a highly irregular magnetic field, as proposed by Laing. The transport equation has been solved in a special case, relating the observable correlation functions in the Stokes parameters Q and U to the correlation functions of magnetic field and plasma density in the source. A rough application of our results to observations of the radio galaxy 3C 166 indicates that the turbulent scale length may be a few percent of the lobe size

  17. Associating Fast Radio Bursts with Extragalactic Radio Sources: General Methodology and a Search for a Counterpart to FRB 170107

    Science.gov (United States)

    Eftekhari, T.; Berger, E.; Williams, P. K. G.; Blanchard, P. K.

    2018-06-01

    The discovery of a repeating fast radio burst (FRB) has led to the first precise localization, an association with a dwarf galaxy, and the identification of a coincident persistent radio source. However, further localizations are required to determine the nature of FRBs, the sources powering them, and the possibility of multiple populations. Here we investigate the use of associated persistent radio sources to establish FRB counterparts, taking into account the localization area and the source flux density. Due to the lower areal number density of radio sources compared to faint optical sources, robust associations can be achieved for less precise localizations as compared to direct optical host galaxy associations. For generally larger localizations that preclude robust associations, the number of candidate hosts can be reduced based on the ratio of radio-to-optical brightness. We find that confident associations with sources having a flux density of ∼0.01–1 mJy, comparable to the luminosity of the persistent source associated with FRB 121102 over the redshift range z ≈ 0.1–1, require FRB localizations of ≲20″. We demonstrate that even in the absence of a robust association, constraints can be placed on the luminosity of an associated radio source as a function of localization and dispersion measure (DM). For DM ≈1000 pc cm‑3, an upper limit comparable to the luminosity of the FRB 121102 persistent source can be placed if the localization is ≲10″. We apply our analysis to the case of the ASKAP FRB 170107, using optical and radio observations of the localization region. We identify two candidate hosts based on a radio-to-optical brightness ratio of ≳100. We find that if one of these is indeed associated with FRB 170107, the resulting radio luminosity (1029‑ 4 × 1030 erg s‑1 Hz‑1, as constrained from the DM value) is comparable to the luminosity of the FRB 121102 persistent source.

  18. The symmetry, misalignment and kinematic evolution of double radio sources

    International Nuclear Information System (INIS)

    Macklin, J.T.

    1981-01-01

    The symmetry properties of a carefully selected sample of 76 double radio sources have been examined. It is found that: (1) The average intrinsic misalignment (the ratio of the displacement of the optical object to the source size, before projection) of these sources is 0.038, independent of the intrinsic size; (2) sources which are most misaligned tend to have the highest values of D, the ratio of hot-spot separations from the nucleus; (3) hot spots are more asymmetric in brightness than are tails; and (4) the relative brightness of hot spots is not correlated with D, but the relation between D and F, the ratio of total flux densities in components, implies that most of the diffuse structure tends to be associated with the hot spot closer to the optical identification. Computer simulations have been used to examine (2); this is best explained if the major contribution to the D distribution is independent of orientation and is correlated with the intrinsic misalignment. It is shown that (2) is in conflict with the hypothesis that motion of the parent galaxy relative to the intergalactic medium makes the dominant contribution to the observed misalignment. (3) and (4) can be explained in terms of a beam model of double radio sources which includes the effects of the external environment. (author)

  19. Scorpius X-1 - an evolving double radio source

    International Nuclear Information System (INIS)

    Geldzahler, B.J.; Fomalont, E.B.; National Radio Astronomy Observatory, Charlottesville, VA)

    1986-01-01

    The radio emission from Sco X-1 has been monitored with the VLA over a 5 yr period with 0.4 arcsec resolution at 4.85 GHz. The source contains three components: an unresolved radio core coincident with the stellar binary system; an unresolved lobe northeast of the core; and an extended lobe southwest of the core. All radio components are approximately comoving with the binary system and are thus undoubtedly associated with it. The northeast lobe is moving away from the core at a rate of 0.013-0.017 arcsec/yr, which corresponds to a velocity of 31-41 km/sec, assuming a distance of 500 pc to Sco X-1. The relative velocity of a hot spot in the southwest lobe with respect to the core is less than 70 km/sec. The flux density in the lobes appears to vary by about 20 percent over time scales of 1 yr, and the variations between the lobes may be correlated. The twin-exhaust beam model where energy is transported from the core to the lobes in narrow beams is the most acceptable model for the evolution of the source. However, interstellar density (greater than 0.6/cu cm) is needed to restrain the velocity of the northeast lobe (presumably the working surface of the beam). 16 references

  20. Turblence-related morphology in extragalactic radio sources

    International Nuclear Information System (INIS)

    Benford, G.; Ferrari, A.; Trussoni, E.

    1980-01-01

    As particle beams propagate through the intergalactic medium, unavoidable instabilities from shear flows produce turbulent magnetic waves. Rather than disrupting beams, this wave energy may enhance luminosity and alter morphology. For reasonable parameters the dominant nonlinear process is an energy cascade from long wavelengths ( 21 cm) to short wavelengths ( 14 cm), where particles are reaccelerated in quasi-linear fachion. We construct a phenomenological turbulence theory to describe this. In an ambient magnetic field, wave-particle scatterings which cause reacceleration can also lead to spatial cross-field diffusion, broadening the beam. Thus beams can flare rapidly as they propagate. This relates luminosity to morphology in a new way. The broadening is wholly intrinsic, unrelated to the beam environment. A variety of radio source types may be related to his effect. Protons do not scatter strongly, remaining collimated and depositing most of the beam energy in hot spots, which are generally weak in the radio but strong in the X-ray

  1. Compact radio sources as a plasma turbulent reactor

    International Nuclear Information System (INIS)

    Atoyan, A.M.; Nagapetyan, A.

    1987-01-01

    The electromagnetic raiation spectra of a homogeneous cosmic radio source (CRS) wherein the relativistic electron acceleration on the langmuir waves leads to the formation of Maxwell-like spectra with characteristic value of the Lorentz-factor γ 0 ∼ 10 3 are considered. It has been shown that due to synchrotron radiation of relativistic electrons, usually observed from CRSs flat radiosepctra, gradually steepening at submillimeter wavelengths are naturally formed in the optically thin range of frequencies. The electromagnetic radiation at the scattering of the electron on the turbulence produces significant nonthermal infrared radiation. Inverse compton scattering of the relativistic electrons on the radio-infrared photons leads the production of X-rays. The characteristic of the electromagnetic radiation spectra obtained in the model are compared with the observational ones

  2. Magnetic field structures in active compact radio sources

    International Nuclear Information System (INIS)

    Jones, T.W.; Rudnick, L.; Fiedler, R.L.; Aller, H.D.; Aller, M.F.; Hodge, P.E.

    1985-01-01

    The analysis of simultaneous multifrequency linear polarimetry data between 1.4 GHz and 90 GHz for about 20 active, compact radio sources at six epochs from 1977 December 10 1980 July is presented. In addition, monthly 8 Ghz polarization data on the same sources were examined. The general polarization characteristics of these sources can be well described in terms of magnetic fields which are largely turbulent and slightly anisotropic. The magnetic field symmetry axes are generally aligned with the source structural axes on the milli-arcsecond scale (OJ 287 is a notable exception.) Monte Carlo calculations indicate that observed polarization variations and in particular rotator polarization events can be produced in this model as a consequence of random walks generated through evolution of the turbulent magnetic field. 43 references

  3. RESOLUTION OF THE COMPACT RADIO CONTINUUM SOURCES IN Arp220

    International Nuclear Information System (INIS)

    Batejat, Fabien; Conway, John E.; Hurley, Rossa; Parra, Rodrigo; Diamond, Philip J.; Lonsdale, Colin J.; Lonsdale, Carol J.

    2011-01-01

    We present 2 cm and 3.6 cm wavelength very long baseline interferometry images of the compact radio continuum sources in the nearby ultra-luminous infrared galaxy Arp220. Based on their radio spectra and variability properties, we confirm these sources to be a mixture of supernovae (SNe) and supernova remnants (SNRs). Of the 17 detected sources we resolve 7 at both wavelengths. The SNe generally only have upper size limits. In contrast all the SNRs are resolved with diameters ≥0.27 pc. This size limit is consistent with them having just entered their Sedov phase while embedded in an interstellar medium (ISM) of density 10 4 cm -3 . These objects lie on the diameter-luminosity correlation for SNRs (and so also on the diameter-surface brightness relation) and extend these correlations to very small sources. The data are consistent with the relation L∝D -9/4 . Revised equipartition arguments adjusted to a magnetic field to a relativistic particle energy density ratio of 1% combined with a reasonable synchrotron-emitting volume filling factor of 10% give estimated magnetic field strengths in the SNR shells of ∼15-50 mG. The SNR shell magnetic fields are unlikely to come from compression of ambient ISM fields and must instead be internally generated. We set an upper limit of 7 mG for the ISM magnetic field. The estimated energy in relativistic particles, 2%-20% of the explosion kinetic energy, is consistent with estimates from models that fit the IR-radio correlation in compact starburst galaxies.

  4. PySE: Python Source Extractor for radio astronomical images

    Science.gov (United States)

    Spreeuw, Hanno; Swinbank, John; Molenaar, Gijs; Staley, Tim; Rol, Evert; Sanders, John; Scheers, Bart; Kuiack, Mark

    2018-05-01

    PySE finds and measures sources in radio telescope images. It is run with several options, such as the detection threshold (a multiple of the local noise), grid size, and the forced clean beam fit, followed by a list of input image files in standard FITS or CASA format. From these, PySe provides a list of found sources; information such as the calculated background image, source list in different formats (e.g. text, region files importable in DS9), and other data may be saved. PySe can be integrated into a pipeline; it was originally written as part of the LOFAR Transient Detection Pipeline (TraP, ascl:1412.011).

  5. Radio News Source Preference by Residents of UYO Urban, Nigeria

    Directory of Open Access Journals (Sweden)

    CHARLES OBOT

    2013-09-01

    Full Text Available Exposure to broadcast news by audience members is part of human information processing.  Radio is believed to be a major source of news on many local and national issues for many people in many countries. But it was uncertain whether the assumption was tenable in Nigeria. Selectivity plays significant role in audience members’ exposure to broadcast news.  The study set out to investigate which radio station(s residents of Uyo residents tune to for news on important local and national issues. It also studied what factors influence their choice of radio station for news on socio-political crises in Nigeria. The findings showed that majority of the respondents prefer foreign radio stations – Voice of America (VOA and British Broadcasting Corporation (BBC for news on socio-political crises in Nigeria. The survey also revealed that media credibility exerted great influence on audience exposure to broadcast news and choice of broadcast medium for news. It is the submission of this work that the continuous presentation of one-sided point of view, whether in government-controlled media or privately-owned ones not only makes the audience hold their news content suspect but also makes such mass medium to rank low in terms of perceived credibility. One of the implications of that situation is that mass mobilization through such media would be difficult to achieve.  Consequently, it is the submission of this research that if broadcast media in Nigeria are to be reckoned trustworthy and reliable, diverse and balanced views on all issues in the news should always be presented.

  6. Interstellar scattering of the compact radio source 2005 + 403

    International Nuclear Information System (INIS)

    Mutel, R.L.; Lestrade, J.

    1990-01-01

    Analysis of Mk III VLBI visibility amplitudes of the compact radio source 2005 + 403 shows an excess at baselines greater than a few diffractive scale lengths compared with that expected from formulas using ensemble-averaged quantities and power-law turbulence with quasi-Kolmogorov spectral indices. The data are in good agreement with the 1989 analysis of Goodman and Narayan, who find that measured visibility amplitudes correspond to the average visibility regime, which differs significantly from the ensemble-averaged results for baselines much longer than one diffractive scale length. 20 refs

  7. Multifrequency VLA observations of PKS 0745-191: the archetypal 'cooling flow' radio source?

    International Nuclear Information System (INIS)

    Baum, S.A.; O'Dea, C.P.

    1991-01-01

    We present 90-, 20-, 6- and 2-cm VLA observations of the high radio luminosity, cooling flow radio source PKS 0745-191. We find that the radio source has a core with a very steep spectrum and diffuse emission with an even steeper spectrum without clear indications of the jets, hotspots or double lobes found in other radio sources of comparable luminosity. The appearance of the source is highly dependent on frequency and resolution. This dependence reflects both the diffuse nature of the extended emission and the steep, but position-dependent, spectrum of the radio emission. (author)

  8. Radio Galaxy Zoo: compact and extended radio source classification with deep learning

    Science.gov (United States)

    Lukic, V.; Brüggen, M.; Banfield, J. K.; Wong, O. I.; Rudnick, L.; Norris, R. P.; Simmons, B.

    2018-05-01

    Machine learning techniques have been increasingly useful in astronomical applications over the last few years, for example in the morphological classification of galaxies. Convolutional neural networks have proven to be highly effective in classifying objects in image data. In the context of radio-interferometric imaging in astronomy, we looked for ways to identify multiple components of individual sources. To this effect, we design a convolutional neural network to differentiate between different morphology classes using sources from the Radio Galaxy Zoo (RGZ) citizen science project. In this first step, we focus on exploring the factors that affect the performance of such neural networks, such as the amount of training data, number and nature of layers, and the hyperparameters. We begin with a simple experiment in which we only differentiate between two extreme morphologies, using compact and multiple-component extended sources. We found that a three-convolutional layer architecture yielded very good results, achieving a classification accuracy of 97.4 per cent on a test data set. The same architecture was then tested on a four-class problem where we let the network classify sources into compact and three classes of extended sources, achieving a test accuracy of 93.5 per cent. The best-performing convolutional neural network set-up has been verified against RGZ Data Release 1 where a final test accuracy of 94.8 per cent was obtained, using both original and augmented images. The use of sigma clipping does not offer a significant benefit overall, except in cases with a small number of training images.

  9. Searching for Compact Radio Sources Associated with UCH ii Regions

    Energy Technology Data Exchange (ETDEWEB)

    Masqué, Josep M.; Trinidad, Miguel A.; Rodríguez-Rico, Carlos A. [Departamento de Astronomía, Universidad de Guanajuato, Apdo. Postal 144, 36000 Guanajuato, México (Mexico); Rodríguez, Luis F.; Kurtz, Stan; Loinard, Laurent [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Morelia 58089, México (Mexico); Dzib, Sergio A. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany)

    2017-02-10

    Ultra-compact (UC)H ii regions represent a very early stage of massive star formation. The structure and evolution of these regions are not yet fully understood. Interferometric observations showed in recent years that compact sources of uncertain nature are associated with some UCH ii regions. To examine this, we carried out VLA 1.3 cm observations in the A configuration of selected UCH ii regions in order to report additional cases of compact sources embedded in UCH ii regions. With these observations, we find 13 compact sources that are associated with 9 UCH ii regions. Although we cannot establish an unambiguous nature for the newly detected sources, we assess some of their observational properties. According to the results, we can distinguish between two types of compact sources. One type corresponds to sources that are probably deeply embedded in the dense ionized gas of the UCH ii region. These sources are photoevaporated by the exciting star of the region and will last for 10{sup 4}–10{sup 5} years. They may play a crucial role in the evolution of the UCH ii region as the photoevaporated material could replenish the expanding plasma and might provide a solution to the so-called lifetime problem of these regions. The second type of compact sources is not associated with the densest ionized gas of the region. A few of these sources appear resolved and may be photoevaporating objects such as those of the first type, but with significantly lower mass depletion rates. The remaining sources of this second type appear unresolved, and their properties are varied. We speculate on the similarity between the sources of the second type and those of the Orion population of radio sources.

  10. The Bologna complete sample of nearby radio sources. II. Phase referenced observations of faint nuclear sources

    Science.gov (United States)

    Liuzzo, E.; Giovannini, G.; Giroletti, M.; Taylor, G. B.

    2009-10-01

    Aims: To study statistical properties of different classes of sources, it is necessary to observe a sample that is free of selection effects. To do this, we initiated a project to observe a complete sample of radio galaxies selected from the B2 Catalogue of Radio Sources and the Third Cambridge Revised Catalogue (3CR), with no selection constraint on the nuclear properties. We named this sample “the Bologna Complete Sample” (BCS). Methods: We present new VLBI observations at 5 and 1.6 GHz for 33 sources drawn from a sample not biased toward orientation. By combining these data with those in the literature, information on the parsec-scale morphology is available for a total of 76 of 94 radio sources with a range in radio power and kiloparsec-scale morphologies. Results: The fraction of two-sided sources at milliarcsecond resolution is high (30%), compared to the fraction found in VLBI surveys selected at centimeter wavelengths, as expected from the predictions of unified models. The parsec-scale jets are generally found to be straight and to line up with the kiloparsec-scale jets. A few peculiar sources are discussed in detail. Tables 1-4 are only available in electronic form at http://www.aanda.org

  11. Model of the Sgr B2 radio source

    International Nuclear Information System (INIS)

    Gosachinskij, I.V.; Khersonskij, V.K.

    1981-01-01

    The dynamical model of the gas cloud around the radio source Sagittarius B2 is suggested. This model describes the kinematic features of the gas in this source: contraction of the core and rotation of the envelope. The stability of the cloud at the initial stage is supported by the turbulent motion of the gas, turbulence energy dissipates due to magnetic viscosity. This process is occurring more rapidly in the dense core and the core begins to collapse but the envelope remains stable. The parameters of the primary cloud and some parameters (mass, density and size) of the collapse are calculated. The conditions in the core at the moment of its fragmentation into masses of stellar order are established [ru

  12. Optical Spectra of Candidate International Celestial Reference Frame (ICRF) Flat-spectrum Radio Sources. III

    Energy Technology Data Exchange (ETDEWEB)

    Titov, O.; Stanford, Laura M. [Geoscience Australia, P.O. Box 378, Canberra, ACT 2601 (Australia); Pursimo, T. [Nordic Optical Telescope, Nordic Optical Telescope Apartado 474E-38700 Santa Cruz de La Palma, Santa Cruz de Tenerife (Spain); Johnston, Helen M.; Hunstead, Richard W. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Jauncey, David L. [CSIRO Astronomy and Space Science, ATNF and Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia); Zenere, Katrina A., E-mail: oleg.titov@ga.gov.au [School of Physics, University of Sydney, NSW 2006 (Australia)

    2017-04-01

    In extending our spectroscopic program, which targets sources drawn from the International Celestial Reference Frame (ICRF) Catalog, we have obtained spectra for ∼160 compact, flat-spectrum radio sources and determined redshifts for 112 quasars and radio galaxies. A further 14 sources with featureless spectra have been classified as BL Lac objects. Spectra were obtained at three telescopes: the 3.58 m European Southern Observatory New Technology Telescope, and the two 8.2 m Gemini telescopes in Hawaii and Chile. While most of the sources are powerful quasars, a significant fraction of radio galaxies is also included from the list of non-defining ICRF radio sources.

  13. Do Unification Models Explain the X-ray Properties of Radio Sources?

    NARCIS (Netherlands)

    Wilkes, Belinda J.; Kuraszkiewicz, J.; Haas, M.; Barthel, P.; Willner, S. P.; Leipski, C.; Worrall, D.; Birkinshaw, M.; Antonucci, R. R.; Ashby, M.; Chini, R.; Fazio, G. G.; Lawrence, C. R.; Ogle, P. M.; Schulz, B.

    Chandra observations of a complete, flux-limited sample of 38 high-redshift (1 radio selected (and so relatively unbiased in orientation), 3CRR radio sources (21 quasars, 17 narrow line radio galaxies, NLRGs) support Unification models and lead to estimates of the covering

  14. Dispersion Measure Variation of Repeating Fast Radio Burst Sources

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Yuan-Pei; Zhang, Bing, E-mail: yypspore@gmail.com, E-mail: zhang@physics.unlv.edu [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

    2017-09-20

    The repeating fast radio burst (FRB) 121102 was recently localized in a dwarf galaxy at a cosmological distance. The dispersion measure (DM) derived for each burst from FRB 121102 so far has not shown significant evolution, even though an apparent increase was recently seen with newly detected VLA bursts. It is expected that more repeating FRB sources may be detected in the future. In this work, we investigate a list of possible astrophysical processes that might cause DM variation of a particular FRB source. The processes include (1) cosmological scale effects such as Hubble expansion and large-scale structure fluctuations; (2) FRB local effects such as gas density fluctuation, expansion of a supernova remnant (SNR), a pulsar wind nebula, and an H ii region; and (3) the propagation effect due to plasma lensing. We find that the DM variations contributed by the large-scale structure are extremely small, and any observable DM variation is likely caused by the plasma local to the FRB source. In addition to mechanisms that decrease DM over time, we suggest that an FRB source in an expanding SNR around a nearly neutral ambient medium during the deceleration (Sedov–Taylor and snowplow) phases or in a growing H ii region can increase DM. Some effects (e.g., an FRB source moving in an H ii region or plasma lensing) can produce either positive or negative DM variations. Future observations of DM variations of FRB 121102 and other repeating FRB sources can provide important clues regarding the physical origin of these sources.

  15. Dispersion Measure Variation of Repeating Fast Radio Burst Sources

    International Nuclear Information System (INIS)

    Yang, Yuan-Pei; Zhang, Bing

    2017-01-01

    The repeating fast radio burst (FRB) 121102 was recently localized in a dwarf galaxy at a cosmological distance. The dispersion measure (DM) derived for each burst from FRB 121102 so far has not shown significant evolution, even though an apparent increase was recently seen with newly detected VLA bursts. It is expected that more repeating FRB sources may be detected in the future. In this work, we investigate a list of possible astrophysical processes that might cause DM variation of a particular FRB source. The processes include (1) cosmological scale effects such as Hubble expansion and large-scale structure fluctuations; (2) FRB local effects such as gas density fluctuation, expansion of a supernova remnant (SNR), a pulsar wind nebula, and an H ii region; and (3) the propagation effect due to plasma lensing. We find that the DM variations contributed by the large-scale structure are extremely small, and any observable DM variation is likely caused by the plasma local to the FRB source. In addition to mechanisms that decrease DM over time, we suggest that an FRB source in an expanding SNR around a nearly neutral ambient medium during the deceleration (Sedov–Taylor and snowplow) phases or in a growing H ii region can increase DM. Some effects (e.g., an FRB source moving in an H ii region or plasma lensing) can produce either positive or negative DM variations. Future observations of DM variations of FRB 121102 and other repeating FRB sources can provide important clues regarding the physical origin of these sources.

  16. FR-type radio sources in COSMOS: relation of radio structure to size, accretion modes and large-scale environment

    Science.gov (United States)

    Vardoulaki, Eleni; Faustino Jimenez Andrade, Eric; Delvecchio, Ivan; Karim, Alexander; Smolčić, Vernesa; Magnelli, Benjamin; Bertoldi, Frank; Schinnener, Eva; Sargent, Mark; Finoguenov, Alexis; VLA COSMOS Team

    2018-01-01

    The radio sources associated with active galactic nuclei (AGN) can exhibit a variety of radio structures, from simple to more complex, giving rise to a variety of classification schemes. The question which still remains open, given deeper surveys revealing new populations of radio sources, is whether this plethora of radio structures can be attributed to the physical properties of the host or to the environment. Here we present an analysis on the radio structure of radio-selected AGN from the VLA-COSMOS Large Project at 3 GHz (JVLA-COSMOS; Smolčić et al.) in relation to: 1) their linear projected size, 2) the Eddington ratio, and 3) the environment their hosts lie within. We classify these as FRI (jet-like) and FRII (lobe-like) based on the FR-type classification scheme, and compare them to a sample of jet-less radio AGN in JVLA-COSMOS. We measure their linear projected sizes using a semi-automatic machine learning technique. Their Eddington ratios are calculated from X-ray data available for COSMOS. As environmental probes we take the X-ray groups (hundreds kpc) and the density fields (~Mpc-scale) in COSMOS. We find that FRII radio sources are on average larger than FRIs, which agrees with literature. But contrary to past studies, we find no dichotomy in FR objects in JVLA-COSMOS given their Eddington ratios, as on average they exhibit similar values. Furthermore our results show that the large-scale environment does not explain the observed dichotomy in lobe- and jet-like FR-type objects as both types are found on similar environments, but it does affect the shape of the radio structure introducing bents for objects closer to the centre of an X-ray group.

  17. Jets and beams in powerful extragalatic radio sources

    International Nuclear Information System (INIS)

    Pelletier, G.; Roland, J.; Asseo, E.

    1989-01-01

    The simplest, but the most constraining assumption for jet modeling powerfull extragalatic radio sources is to consider a single relativistic plasma with relativistic motion from short distances (few pc) to large distances (few 100 kpc) from the nucleus. We argue that it is worth introducing more ingredients in the model. Besides the interest in developing plasma physics motivated by these objects, there are two reasons for enriching the physics. First, the interpretation of hot spots as resulting from shocks with diffusive acceleration in a thermal classical plasma with a tenuous relativistic component is consistent with data and constrain the parameters. Second, the interpretation of relativistic motions on parsec scales as resulting from a core beam relaxing in a collimated wind is consistent with data and avoid several difficulties. (author). 14 refs

  18. Outer heliospheric radio emissions. II - Foreshock source models

    Science.gov (United States)

    Cairns, Iver H.; Kurth, William S.; Gurnett, Donald A.

    1992-01-01

    Observations of LF radio emissions in the range 2-3 kHz by the Voyager spacecraft during the intervals 1983-1987 and 1989 to the present while at heliocentric distances greater than 11 AU are reported. New analyses of the wave data are presented, and the characteristics of the radiation are reviewed and discussed. Two classes of events are distinguished: transient events with varying starting frequencies that drift upward in frequency and a relatively continuous component that remains near 2 kHz. Evidence for multiple transient sources and for extension of the 2-kHz component above the 2.4-kHz interference signal is presented. The transient emissions are interpreted in terms of radiation generated at multiples of the plasma frequency when solar wind density enhancements enter one or more regions of a foreshock sunward of the inner heliospheric shock. Solar wind density enhancements by factors of 4-10 are observed. Propagation effects, the number of radiation sources, and the time variability, frequency drift, and varying starting frequencies of the transient events are discussed in terms of foreshock sources.

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

    International Nuclear Information System (INIS)

    Wing, Joshua D.; Blanton, Elizabeth L.

    2013-01-01

    Using radio sources from the Faint Images of the Radio Sky at Twenty-cm survey, and optical counterparts in the Sloan Digital Sky Survey, 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.

  20. ULTRA STEEP SPECTRUM RADIO SOURCES IN THE LOCKMAN HOLE: SERVS IDENTIFICATIONS AND REDSHIFT DISTRIBUTION AT THE FAINTEST RADIO FLUXES

    Energy Technology Data Exchange (ETDEWEB)

    Afonso, J.; Bizzocchi, L.; Grossi, M.; Messias, H.; Fernandes, C. A. C. [Observatorio Astronomico de Lisboa, Faculdade de Ciencias, Universidade de Lisboa, Tapada da Ajuda, 1349-018 Lisbon (Portugal); Ibar, E.; Ivison, R. J. [UK Astronomy Technology Centre, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom); Simpson, C. [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD (United Kingdom); Chapman, S.; Gonzalez-Solares, E. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Jarvis, M. J. [Centre for Astrophysics, Science and Technology Research Institute, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Rottgering, H. [Leiden Observatory, Leiden University, Oort Gebouw, P.O. Box 9513, 2300 RA Leiden (Netherlands); Norris, R. P. [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia); Dunlop, J.; Best, P. [SUPA, Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Pforr, J. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Vaccari, M. [Department of Astronomy, University of Padova, vicolo Osservatorio 3, 35122 Padova (Italy); Seymour, N. [Mullard Space Science Laboratory, UCL, Holmbury St Mary, Dorking, Surrey RH5 6NT (United Kingdom); Farrah, D. [Astronomy Centre, Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom); Huang, J.-S., E-mail: jafonso@oal.ul.pt [Department of Astrophysics, Oxford University, Keble Road, Oxford OX1 3RH (United Kingdom); and others

    2011-12-20

    Ultra steep spectrum (USS) radio sources have been successfully used to select powerful radio sources at high redshifts (z {approx}> 2). Typically restricted to large-sky surveys and relatively bright radio flux densities, it has gradually become possible to extend the USS search to sub-mJy levels, thanks to the recent appearance of sensitive low-frequency radio facilities. Here a first detailed analysis of the nature of the faintest USS sources is presented. By using Giant Metrewave Radio Telescope and Very Large Array radio observations of the Lockman Hole at 610 MHz and 1.4 GHz, a sample of 58 USS sources, with 610 MHz integrated fluxes above 100 {mu}Jy, is assembled. Deep infrared data at 3.6 and 4.5 {mu}m from the Spitzer Extragalactic Representative Volume Survey (SERVS) are used to reliably identify counterparts for 48 (83%) of these sources, showing an average total magnitude of [3.6]{sub AB} = 19.8 mag. Spectroscopic redshifts for 14 USS sources, together with photometric redshift estimates, improved by the use of the deep SERVS data, for a further 19 objects, show redshifts ranging from z = 0.1 to z = 2.8, peaking at z {approx} 0.6 and tailing off at high redshifts. The remaining 25 USS sources, with no redshift estimate, include the faintest [3.6] magnitudes, with 10 sources undetected at 3.6 and 4.5 {mu}m (typically [3.6] {approx}> 22-23 mag from local measurements), which suggests the likely existence of higher redshifts among the sub-mJy USS population. The comparison with the Square Kilometre Array Design Studies Simulated Skies models indicates that Fanaroff-Riley type I radio sources and radio-quiet active galactic nuclei may constitute the bulk of the faintest USS population, and raises the possibility that the high efficiency of the USS technique for the selection of high-redshift sources remains even at the sub-mJy level.

  1. The peculiar radio source M17 JVLA 35

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, L. F.; Carrasco-González, C. [Centro de Radioastronomía y Astrofísica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Montes, G. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Tapia, M. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 877, Ensenada, BC, CP 22830 (Mexico)

    2014-07-01

    M17 JVLA 35 is a radio source detected in projection against the M17 H II region. In recent observations, its spectrum between 4.96 and 8.46 GHz was found to be positive and very steep, with α ≥ 2.9 ± 0.6 (S {sub ν}∝ν{sup α}). Here we present Very Large Array observations made in the 18.5 to 36.5 GHz region that indicate a spectral turnover at ∼13 GHz and a negative spectral index (α ≅ –2.0) at higher frequencies. The spectrum is consistent with that of an extragalactic high frequency peaker (HFP). However, M17 JVLA 35 has an angular size of ∼0.''5 at 8.46 GHz, while HFPs have extremely compact, milliarcsecond dimensions. We discuss other possible models for the spectrum of the source and do not find them feasible. Finally, we propose that M17 JVLA 35 is indeed an HFP but that its angular size becomes broadened by plasma scattering as its radiation travels across M17. If our interpretation is correct, accurate measurements of the angular size of M17 JVLA 35 across the centimeter range should reveal the expected ν{sup –2} dependence.

  2. A radio monitoring survey of ultra-luminous X-ray sources

    Science.gov (United States)

    Körding, E.; Colbert, E.; Falcke, H.

    2005-06-01

    We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg s-1. A well-defined sample of the 9 nearest ULXs has been monitored eight times over 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is ≈0.15 mJy (4σ) for radio flares and ≈60 μJy for continuous emission. In M 82 two ULXs seem to have coincident compact radio sources, which are probably supernova remnants. No continuous or flaring radio emission has been detected from any other ULX. Thus, ULXs do not generally emit steady-state radio emission above radio powers of 1.5 × 1017 W/Hz. The non-detections of the continuous emission are consistent with beamed or unbeamed radio emission from accreting black holes of ≤ 103 M⊙ based on the radio/X-ray correlation. Other published radio detections (M 82, NGC 5408) are also discussed in this context. Both detections are significantly above our detection limit. If ULXs have flaring radio emission above 4 × 1017 W/Hz we can give an upper limit on the duty cycle of the flares of 6%. This upper limit is in agreement with the observed number of flares in Galactic radio transients. Additionally we present a yet unreported radio double structure in the nearby low-luminosity AGN NGC 4736.

  3. TEMPORAL SMEARING OF TRANSIENT RADIO SOURCES BY THE INTERGALACTIC MEDIUM

    International Nuclear Information System (INIS)

    Macquart, Jean-Pierre; Koay, Jun Yi

    2013-01-01

    The temporal smearing of impulsive radio events at cosmological redshifts probes the properties of the ionized intergalactic medium (IGM). We relate the degree of temporal smearing and the profile of a scattered source to the evolution of a turbulent structure in the IGM as a function of redshift. We estimate the degree of scattering expected by analyzing the contributions to the scattering measure of the various components of baryonic matter embedded in the IGM, including the diffuse IGM, intervening galaxies, and intracluster gas. These estimates predict that the amount of temporal smearing expected at 300 MHz is typically as low as ∼1 ms and suggests that these bursts may be detectable with low-frequency widefield arrays. A generalization of the dispersion-measure-scattering-measure relation observed for Galactic scattering to the densities and turbulent conditions relevant to the IGM suggests that scattering measures on the order of 10 –6 kpc m –20/3 would be expected at z ∼ 1. This scattering is sufficiently low enough that its effects would not, for most lines of sight, be manifested in existing observations of the scatter broadening in images of extragalactic compact sources. The redshift dependence on the temporal smearing discriminates between scattering that occurs in the host galaxy of the burst and the IGM, with τ host ∝(1 + z) –3 if the scattering probes length scales below the inner scale of the turbulence or τ host ∝(1 + z) –17/5 if the turbulence follows a Kolmogorov spectrum. This differs strongly from the expected IGM scaling τ IGM ∼ z 2 for z ∼ 0.2–0.5 for z ∼> 1

  4. JVLA observations of IC 348 SW: Compact radio sources and their nature

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina, E-mail: l.rodriguez@crya.unam.mx, E-mail: l.zapata@crya.unam.mx, E-mail: a.palau@crya.unam.mx [Centro de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico)

    2014-07-20

    We present sensitive 2.1 and 3.3 cm Jansky Very Large Array radio continuum observations of the region IC 348 SW. We detect a total of 10 compact radio sources in the region, 7 of which are first reported here. One of the sources is associated with the remarkable periodic time-variable infrared source LRLL 54361, opening the possibility of monitoring this object at radio wavelengths. Four of the sources appear to be powering outflows in the region, including HH 211 and HH 797. In the case of the rotating outflow HH 797, we detect a double radio source at its center, separated by ∼3''. Two of the sources are associated with infrared stars that possibly have gyrosynchrotron emission produced in active magnetospheres. Finally, three of the sources are interpreted as background objects.

  5. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    International Nuclear Information System (INIS)

    Giroletti, M.; Massaro, F.; D’Abrusco, R.; Lico, R.; Burlon, D.

    2016-01-01

    Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. In this paper, we characterize the spectral properties of the blazar population at low radio frequency, compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. We cross-correlated the 6100 deg"2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120–180 MHz) blazar spectral index is (α_l_o_w) = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Finally, upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population.

  6. Crowd-Sourced Radio Science at Marshall Space Flight Center

    Science.gov (United States)

    Fry, C. D.; McTernan, J. K.; Suggs, R. M.; Rawlins, L.; Krause, L. H.; Gallagher, D. L.; Adams, M. L.

    2018-01-01

    August 21, 2017 provided a unique opportunity to investigate the effects of the total solar eclipse on high frequency (HF) radio propagation and ionospheric variability. In Marshall Space Flight Center's partnership with the US Space and Rocket Center (USSRC) and Austin Peay State University (APSU), we engaged citizen scientists and students in an investigation of the effects of an eclipse on the mid-latitude ionosphere. Activities included fieldwork and station-based data collection of HF Amateur Radio frequency bands and VLF radio waves before, during, and after the eclipse to build a continuous record of changing propagation conditions as the moon's shadow marched across the United States. Post-eclipse radio propagation analysis provided insights into ionospheric variability due to the eclipse.

  7. RADIO MONITORING OF THE PERIODICALLY VARIABLE IR SOURCE LRLL 54361: NO DIRECT CORRELATION BETWEEN THE RADIO AND IR EMISSIONS

    Energy Technology Data Exchange (ETDEWEB)

    Forbrich, Jan, E-mail: jan.forbrich@univie.ac.at [University of Vienna, Department of Astrophysics, Türkenschanzstraße 17, A-1180 Vienna (Austria); Rodríguez, Luis F.; Palau, Aina; Zapata, Luis A. [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Muzerolle, James [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Gutermuth, Robert A. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

    2015-11-20

    LRLL 54361 is an infrared source located in the star-forming region IC 348 SW. Remarkably, its infrared luminosity increases by a factor of 10 over roughly one week every 25.34 days. To understand the origin of these remarkable periodic variations, we obtained sensitive 3.3 cm JVLA radio continuum observations of LRLL 54361 and its surroundings in six different epochs: three of them during the IR-on state and three during the IR-off state. The radio source associated with LRLL 54361 remained steady and did not show a correlation with the IR variations. We suggest that the IR is tracing the results of fast (with a timescale of days) pulsed accretion from an unseen binary companion, while the radio traces an ionized outflow with an extent of ∼100 AU that smooths out the variability over a period of the order of a year. The average flux density measured in these 2014 observations, 27 ± 5 μJy, is about a factor of two less than that measured about 1.5 years before, 53 ± 11 μJy, suggesting that variability in the radio is present, but over larger timescales than in the IR. We discuss other sources in the field, in particular two infrared/X-ray stars that show rapidly varying gyrosynchrotron emission.

  8. How Fred Hoyle Reconciled Radio Source Counts and the Steady State Cosmology

    Science.gov (United States)

    Ekers, Ron

    2012-09-01

    In 1969 Fred Hoyle invited me to his Institute of Theoretical Astronomy (IOTA) in Cambridge to work with him on the interpretation of the radio source counts. This was a period of extreme tension with Ryle just across the road using the steep slope of the radio source counts to argue that the radio source population was evolving and Hoyle maintaining that the counts were consistent with the steady state cosmology. Both of these great men had made some correct deductions but they had also both made mistakes. The universe was evolving, but the source counts alone could tell us very little about cosmology. I will try to give some indication of the atmosphere and the issues at the time and look at what we can learn from this saga. I will conclude by briefly summarising the exponential growth of the size of the radio source counts since the early days and ask whether our understanding has grown at the same rate.

  9. About the Modeling of Radio Source Time Series as Linear Splines

    Science.gov (United States)

    Karbon, Maria; Heinkelmann, Robert; Mora-Diaz, Julian; Xu, Minghui; Nilsson, Tobias; Schuh, Harald

    2016-12-01

    Many of the time series of radio sources observed in geodetic VLBI show variations, caused mainly by changes in source structure. However, until now it has been common practice to consider source positions as invariant, or to exclude known misbehaving sources from the datum conditions. This may lead to a degradation of the estimated parameters, as unmodeled apparent source position variations can propagate to the other parameters through the least squares adjustment. In this paper we will introduce an automated algorithm capable of parameterizing the radio source coordinates as linear splines.

  10. Relativistic jets and the most powerful radio sources in the universe

    International Nuclear Information System (INIS)

    Bridle, A.

    1987-01-01

    Relativistic jets, which are beams of particles and magnetic fields emitting synchrotron radiation that emanate from black holes at the centers of galaxies and quasars, have been one of the most exciting discoveries made at the Very Large Array (VLA) operated by the National Radio Astronomy Observatory (NRAO). The VLA is an array of 27 antennas, each 25 meters in diameter, distributed in a Y-formation with two branches 21 kilometers long and one branch 19 kilometers long. Astronomers can use it to study relativistic jets that generate intense natural radio sources (or transmitters). These sources, associated with regions hundreds of thousands of light years across, are the most powerful in the universe in energy output. In his lecture, Bridle describes how consecutive advances in imaging techniques for radio astronomy have uncovered the properties of the powerful radio sources, culminating in the discovery at the VLA that many of these sources contain radio emitting jets. He then describes some of the NRAO's research on these jets, and discusses the jets' physical properties. He concludes with an outlook for the future: the NRAO's Very Long Baseline Array (VLBA) is to be completed in the early 1990's. The VLBA is an array of ten radio telescopes distributed from Hawaii to St. Croix, from the Canadian border to Texas. With the VLBA, astronomers plan to look more deeply into these radio sources. 15 figs

  11. FIRST 'WINGED' AND X-SHAPED RADIO SOURCE CANDIDATES. II. NEW REDSHIFTS

    International Nuclear Information System (INIS)

    Cheung, C. C.; Healey, Stephen E.; Landt, Hermine; Jordan, Andres; Verdoes Kleijn, Gijs

    2009-01-01

    We report optical spectroscopic observations of X-shaped radio sources with the Hobby-Eberly Telescope and Multiple-Mirror Telescope, focused on the sample of candidates from the FIRST survey presented in a previous paper. A total of 27 redshifts were successfully obtained, 21 of which are new, including a newly identified candidate source of this type which is presented here. With these observations, the sample of candidates from the previous paper is over 50% spectroscopically identified. Two new broad emission-lined X-shaped radio sources are revealed, while no emission lines were detected in about one-third of the observed sources; a detailed study of the line properties is deferred to a future paper. Finally, to explore their relation to the Fanaroff-Riley division, the radio luminosities and host galaxy absolute magnitudes of a spectroscopically identified sample of 50 X-shaped radio galaxies are calculated to determine their placement in the Owen-Ledlow plane.

  12. EGRET Unidentified Source Radio Observations and Performance of Receiver Gain Calibration

    International Nuclear Information System (INIS)

    Niinuma, Kotaro; Asuma, Kuniyuki; Kuniyoshi, Masaya; Matsumura, Nobuo; Takefuji, Kazuhiro; Kida, Sumiko; Takeuchi, Akihiko; Ichikawa, Hajime; Sawano, Akihiro; Yoshimura, Naoya; Suzuki, Shigehiro; Nakamura, Ryosuke; Nakayama, Yu; Daishido, Tsuneaki

    2006-01-01

    Last year, we have developed the receiver gain calibration system by using Johnson-Nyquist noise, for accuracy flux measurement, because we have been starting radio identification program of transient radio sources, blazars and radio counterpart of The Energetic Gamma Ray Experiment Telescope (EGRET) unidentified γ-ray sources in Waseda Nasu Pulsar Observatory. It is shown that there are a few low correlation data between receiver gain and ambient temperature around receiver for anything troubles of receiver, because we can detect gain and ambient temperature through a day by developed system. Estimated fluctuations of daily data of steady sources decrease by removing low correlation data before analysing. As the result of our analysis by using above system, radio counterpart of EGRET identified source showed fading light-curve for a week

  13. Determination of plasma parameters in solar zebra radio sources

    Czech Academy of Sciences Publication Activity Database

    Karlický, Marian; Yasnov, L. V.

    2015-01-01

    Roč. 581, September (2015), A115/1-A115/6 ISSN 0004-6361 R&D Projects: GA ČR GAP209/12/0103 Grant - others:EC(XE) 606862 Program:FP7 Institutional support: RVO:67985815 Keywords : Sun * flares * radio radiation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  14. (WAT) Radio Source Associated with the Galaxy PGC 1519010 NG

    Indian Academy of Sciences (India)

    2009-03-13

    Mar 13, 2009 ... 2Raman Research Institute, Sadashivnagar, Bangalore 560 080, India. ∗ e-mail: ... Radio galaxies—cluster of galaxies—ram pressure—intra- ... In this paper, we report the GMRT detection of a WAT associated with the galaxy.

  15. The gaseous haloes of evolving galaxies: a probe using the linear sizes of radio sources

    International Nuclear Information System (INIS)

    Subramanian, K.; Swarup, G.

    1990-01-01

    As galaxies form and evolve, their gaseous haloes are expected to undergo corresponding evolution. We examine here whether observations of the linear sizes of radio sources can be used to probe such evolution. For this purpose we first represent the gas density at various stages of galaxy formation and evolution by means of simple model density profiles, and then work out the expected linear sizes (l) of radio sources in these models. (author)

  16. A statistical study of faint radio sources at 81.5 MHz

    International Nuclear Information System (INIS)

    Duffett-Smith, P.J.; Purvis, A.; Hewish, A.

    1980-01-01

    The method of interplanetary scintillations (IPS) together with the technique of background deflection analysis (P(D)) have been used to determine the mean angular size and the sky density of scintillating radio sources in the range 2 to 3 Jy at 81.5 MHz. It is found that the radio power from a high proportion of the sources in this range comes from one or two components of angular diameter about 0.7 arcsec. (author)

  17. Superconducting cosmic string loops as sources for fast radio bursts

    Science.gov (United States)

    Cao, Xiao-Feng; Yu, Yun-Wei

    2018-01-01

    The cusp burst radiation of superconducting cosmic string (SCS) loops is thought to be a possible origin of observed fast radio bursts with the model-predicted radiation spectrum and the redshift- and energy-dependent event rate, we fit the observational redshift and energy distributions of 21 Parkes fast radio bursts and constrain the model parameters. It is found that the model can basically be consistent with the observations, if the current on the SCS loops has a present value of ˜1016μ179 /10 esu s-1 and evolves with redshift as an empirical power law ˜(1 +z )-1.3 , where μ17=μ /1017 g cm-1 is the string tension. This current evolution may provide a clue to probe the evolution of the cosmic magnetic fields and the gathering of the SCS loops to galaxy clusters.

  18. Spectroscopy of radio sources from the Parkes 2700 MHz survey

    International Nuclear Information System (INIS)

    Thompson, D.J.; Djorgovski, S.; De Carvalho, R.

    1990-01-01

    The results of long-slit CCD spectroscopy on 37 objects from the Parkes 2700 MHz survey are presented, with data for an additional two companion objects. Eight of the objects are quasars, six more are AGNs, and five more are radio galaxies. Seventeen of the objects observed are stars and, thus, probable misidentifications. Three objects show featureless spectra and are identified as possible BL Lac objects. Spectra are presented for a total of 20 objects. 20 refs

  19. H{sup -} radio frequency source development at the Spallation Neutron Source

    Energy Technology Data Exchange (ETDEWEB)

    Welton, R. F.; Gawne, K. R.; Han, B. X.; Murray, S. N.; Pennisi, T. R.; Roseberry, R. T.; Santana, M.; Stockli, M. P. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37830-6471 (United States); Dudnikov, V. G. [Muons, Inc., 552 N. Batavia Avenue, Batavia, Illinois 60510 (United States); Turvey, M. W. [Villanova University, 800E. Lancaster Ave, Villanova, Pennsylvania 19085 (United States)

    2012-02-15

    The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent {approx}38 mA peak current in the linac and an availability of {approx}90%. H{sup -} beam pulses ({approx}1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, {approx}60 kW) of a copper antenna that has been encased with a thickness of {approx}0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of {approx}99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of {approx}75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance/installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to {approx}100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

  20. Superconducting cosmic strings as sources of cosmological fast radio bursts

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Jiani [University of Science and Technology of China, CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, Hefei, Anhui (China); Chinese Academy of Sciences, Shanghai Astronomical Observatory, Shanghai (China); Stony Brook University, Department of Physics and Astronomy, Stony Brook, NY (United States); University of Chinese Academy of Sciences, Beijing (China); Wang, Kai; Cai, Yi-Fu [University of Science and Technology of China, CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, Hefei, Anhui (China); University of Science and Technology of China, School of Astronomy and Space Science, Hefei, Anhui (China)

    2017-11-15

    In this paper we calculate the radio burst signals from three kinds of structures of superconducting cosmic strings. By taking into account the observational factors including scattering and relativistic effects, we derive the event rate of radio bursts as a function of redshift with the theoretical parameters Gμ and I of superconducting strings. Our analyses show that cusps and kinks may have noticeable contributions to the event rate and in most cases cusps would dominate the contribution, while the kink-kink collisions tend to have secondary effects. By fitting theoretical predictions with the normalized data of fast radio bursts, we for the first time constrain the parameter space of superconducting strings and report that the parameter space of Gμ ∝ [10{sup -14}, 10{sup -12}] and I ∝ [10{sup -1}, 10{sup 2}] GeV fit the observation well although the statistic significance is low due to the lack of observational data. Moreover, we derive two types of best fittings, with one being dominated by cusps with a redshift z = 1.3, and the other dominated by kinks at the range of the maximal event rate. (orig.)

  1. Superconducting cosmic strings as sources of cosmological fast radio bursts

    Science.gov (United States)

    Ye, Jiani; Wang, Kai; Cai, Yi-Fu

    2017-11-01

    In this paper we calculate the radio burst signals from three kinds of structures of superconducting cosmic strings. By taking into account the observational factors including scattering and relativistic effects, we derive the event rate of radio bursts as a function of redshift with the theoretical parameters Gμ and I of superconducting strings. Our analyses show that cusps and kinks may have noticeable contributions to the event rate and in most cases cusps would dominate the contribution, while the kink-kink collisions tend to have secondary effects. By fitting theoretical predictions with the normalized data of fast radio bursts, we for the first time constrain the parameter space of superconducting strings and report that the parameter space of Gμ ˜ [10^{-14}, 10^{-12}] and I ˜ [10^{-1}, 102] GeV fit the observation well although the statistic significance is low due to the lack of observational data. Moreover, we derive two types of best fittings, with one being dominated by cusps with a redshift z = 1.3, and the other dominated by kinks at the range of the maximal event rate.

  2. The faint radio source population at 15.7 GHz - II. Multi-wavelength properties

    Science.gov (United States)

    Whittam, I. H.; Riley, J. M.; Green, D. A.; Jarvis, M. J.; Vaccari, M.

    2015-11-01

    A complete, flux density limited sample of 96 faint (>0.5 mJy) radio sources is selected from the 10C survey at 15.7 GHz in the Lockman Hole. We have matched this sample to a range of multi-wavelength catalogues, including Spitzer Extragalactic Representative Volume Survey, Spitzer Wide-area Infrared Extragalactic survey, United Kingdom Infrared Telescope Infrared Deep Sky Survey and optical data; multi-wavelength counterparts are found for 80 of the 96 sources and spectroscopic redshifts are available for 24 sources. Photometric redshifts are estimated for the sources with multi-wavelength data available; the median redshift of the sample is 0.91 with an interquartile range of 0.84. Radio-to-optical ratios show that at least 94 per cent of the sample are radio loud, indicating that the 10C sample is dominated by radio galaxies. This is in contrast to samples selected at lower frequencies, where radio-quiet AGN and star-forming galaxies are present in significant numbers at these flux density levels. All six radio-quiet sources have rising radio spectra, suggesting that they are dominated by AGN emission. These results confirm the conclusions of Paper I that the faint, flat-spectrum sources which are found to dominate the 10C sample below ˜1 mJy are the cores of radio galaxies. The properties of the 10C sample are compared to the Square Kilometre Array Design Studies Simulated Skies; a population of low-redshift star-forming galaxies predicted by the simulation is not found in the observed sample.

  3. The effects of variability on the number-flux-density relationship for radio sources

    International Nuclear Information System (INIS)

    Schuch, N.J.

    1981-01-01

    It has been known for some time that the number-flux-density relationship for radio sources requires a population of sources whose properties evolve with cosmological epoch, at least in models where the redshifts are all taken to be cosmological. In particular, the surveys made at metre wavelengths show, for bright sources, a slope of the log N -log S curve which is steeper than the value -1.5 expected in a static, non-evolving Euclidean universe. Here, N is the number of radio sources brighter than flux density S. Expansion without evolution in conventional geometrical models predicts slopes flatter than -1.5. If the radio survey is carried out at higher frequencies (typically 2.7 or 5 GHz - 11 or 6 cm wavelength), the slope of the log N -log S curve is steeper than -1.5 but not so steep as the slopes found for the low-frequency surveys. Many of the sources found in high-frequency surveys have radio spectra with relatively higher flux-densities in the centimetre range; these sources are frequently variable at high frequencies, with time-scales from a month or two upwards. Some possible effects of the variations on the observed counts of radio sources are considered. (author)

  4. Planck early results. XIII. Statistical properties of extragalactic radio sources in the Planck Early Release Compact Source Catalogue

    DEFF Research Database (Denmark)

    Lähteenmäki, A.; Poutanen, T.; Natoli, P.

    2011-01-01

    The data reported in Planck's Early Release Compact Source Catalogue (ERCSC) are exploited to measure the number counts (dN/dS) of extragalactic radio sources at 30, 44, 70, 100, 143 and 217 GHz. Due to the full-sky nature of the catalogue, this measurement extends to the rarest and brightest sou...

  5. On the redshift cut-off for flat-spectrum radio sources

    OpenAIRE

    Jarvis, Matt J.; Rawlings, Steve

    2000-01-01

    We use data from the Parkes Half-Jansky Flat-Spectrum (PHJFS) sample (Drinkwater et al. 1997) to constrain the cosmic evolution in the co-moving space density of radio sources in the top decade of the flat-spectrum radio luminosity function (RLF). A consistent picture for the high-redshift evolution is achieved using both simple parametric models, which are the first to allow for distributions in both radio luminosity and spectral index, and variants of the V / V_max test, some of which incor...

  6. Radio Follow-up on All Unassociated Gamma-Ray Sources from the Third Fermi Large Area Telescope Source Catalog

    Energy Technology Data Exchange (ETDEWEB)

    Schinzel, Frank K. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Petrov, Leonid [Astrogeo Center, Falls Church, VA 22043 (United States); Taylor, Gregory B. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States); Edwards, Philip G., E-mail: fschinze@nrao.edu [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, 1710 NSW (Australia)

    2017-04-01

    The third Fermi Large Area Telescope γ -ray source catalog (3FGL) contains over 1000 objects for which there is no known counterpart at other wavelengths. The physical origin of the γ -ray emission from those objects is unknown. Such objects are commonly referred to as unassociated and mostly do not exhibit significant γ -ray flux variability. We performed a survey of all unassociated γ -ray sources found in 3FGL using the Australia Telescope Compact Array and Very Large Array in the range 4.0–10.0 GHz. We found 2097 radio candidates for association with γ -ray sources. The follow-up with very long baseline interferometry for a subset of those candidates yielded 142 new associations with active galactic nuclei that are γ -ray sources, provided alternative associations for seven objects, and improved positions for another 144 known associations to the milliarcsecond level of accuracy. In addition, for 245 unassociated γ -ray sources we did not find a single compact radio source above 2 mJy within 3 σ of their γ -ray localization. A significant fraction of these empty fields, 39%, are located away from the Galactic plane. We also found 36 extended radio sources that are candidates for association with a corresponding γ -ray object, 19 of which are most likely supernova remnants or H ii regions, whereas 17 could be radio galaxies.

  7. Radio and x-ray observations of compact sources in or near supernova remnants

    International Nuclear Information System (INIS)

    Seaquist, E.R.; Gilmore, W.S.

    1982-01-01

    We present VLA multifrequency radio observations of six compact radio sources from the list of nine objects proposed by Ryle et al. [Nature 276, 571 (1978)] as a new class of radio star, possibly the stellar remnants of supernovae. We also present the results of a search for x-ray emission from four of these objects with the Einstein observatory. The radio observations provide information on spectra, polarization, time variability, angular structure, and positions for these sources. The bearing of these new data on the nature of the sources is discussed. One particularly interesting result is that the polarization and angular-size measurements are combined in an astrophysical argument to conclude that one of the sources (2013+370) is extragalactic. No x-ray emission was detected from any of the four objects observed, but an extended x-ray source was found coincident with the supernova remnant G 33.6+0.1 near 1849+005. Our measurements provide no compelling arguments to consider any of the six objects studied as radio stars

  8. A study of faint radio sources near the North Galactic Pole

    International Nuclear Information System (INIS)

    Benn, C.R.

    1981-09-01

    A large amount of observational data has been obtained on faint radio sources in a small area of sky near the North Galactic Pole (the 5C 12 area). This provides a new perspective (3 decades in flux density from the 3CR catalogue) on the physical properties and cosmological evolution of extragalactic radio sources. Chapter 1 introduces the problem and concludes that faint-object cosmology is best served by intensive investigation of sources in a small area of sky. An optimum area is chosen, at right ascension 12sup(h) 58sup(m) 43sup(s) and declination 35 0 14' 00'' (1950.0). Chapter 2 describes the 5C12 radio survey (complete to 9mJy apparent flux density at 408MHz) conducted with the One Mile Telescope at Cambridge. Chapter 4 describes a 4.85GHz survey to 20mJy of the area, conducted at Effelsberg. In chapter 5, a program of optical identification for the sources is described, using deep (msub(g) = 22.5, msub(y) = 20.7) Schmidt plates taken at Hale Observatories. A statistical algorithm is developed to cope with the problems of optical confusion due to radio positional errors. Chapter 6 draws on data from the previous 4, and presents results concerning radio source counts, spectral index distributions, optical identifications and clustering. (author)

  9. On the radio source scintillations caused by plasma inhomogeneities behind a shock wave

    International Nuclear Information System (INIS)

    Pimenov, S.F.

    1984-01-01

    The turbulence in the interplanetary and interstellar medium is shown to become anisotropic and statistically inhomogeneous after a shock wave passing. Scintillation intensity spectra of radio sources are estimated. The possibilities to derive the inhomogeneity spectra and source brightness distribution from scintillation changes are discussed

  10. THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    Padovani, P.; Mainieri, V.; Rosati, P.; Miller, N.; Kellermann, K. I.; Tozzi, P.

    2011-01-01

    We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 μJy at the field center and redshift ∼5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P ∼> 3 x 10 24 W Hz -1 ) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for ∼30% of the sample and ∼60% of all AGNs, and outnumbering radio-loud AGNs at ∼< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

  11. Radio Observations of Ultra-Luminous X-Ray Sources and their Implication for Models

    Science.gov (United States)

    Koerding, E. G.; Colbert, E. J. M.; Falcke, H.

    2004-05-01

    We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These intriguing sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg/sec. Assuming isotropic emission the Eddington Limit suggests that they harbor intermediate mass black holes. Due to the problems of this explanation also other possibilities are currently discussed, among them are anisotropic emission, super-Eddington accretion flows or relativistically beamed emission from microquasars. Detections of compact radio cores at the positions of ULXs would be a direct hint to jet-emission. However, as the ULX phenomenom is connected to star formation we have to assume that they are strongly accreting objects. Thus, similar to their nearest Galactic cousins, the very high state X-ray binaries (see e.g., GRS 1915), ULXs may show radio flares. A well-defined sample of the 9 nearest ULXs has been monitored eight times during 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is 0.15 mJy (4 σ ) for flares and 68 μ Jy for continuous emission. In M82 some ULXs seem to be connected to radio supernova remnants. Besides that no flare or continuous emission has been detected. As the timescales of radio flares in ULXs are highly uncertain, it could well be that we have undersampled the lightcurve. However, upper bounds for the probability to detect a flare can be given. The upper limits for the continuous emission are compared with the emission found in NGC 5408 X-1 and with quasars and microquasars. We show that these limits are well in agreement with the microblazar model using the Radio/X-ray correlation of XRBs and AGN. Thus, it could well be that ULXs are microblazers which may be radio loud.

  12. Radio astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Nagnibeda, V.G.

    1981-01-01

    The history of radio astronomical observations at the Astronomical Observatory of Leningrad State University is reviewed. Various facilities are described, and methods and instruments used are discussed. Some results are summarized for radio observations of the sun, including observations of local sources of solar radio emission, the absolute solar radio flux, and radio emission from filaments and prominences.

  13. 3D relativistic MHD numerical simulations of X-shaped radio sources

    Science.gov (United States)

    Rossi, P.; Bodo, G.; Capetti, A.; Massaglia, S.

    2017-10-01

    Context. A significant fraction of extended radio sources presents a peculiar X-shaped radio morphology: in addition to the classical double lobed structure, radio emission is also observed along a second axis of symmetry in the form of diffuse wings or tails. In a previous investigation we showed the existence of a connection between the radio morphology and the properties of the host galaxies. Motivated by this connection we performed two-dimensional numerical simulations showing that X-shaped radio sources may naturally form as a jet propagates along the major axis a highly elliptical density distribution, because of the fast expansion of the cocoon along the minor axis of the distribution. Aims: We intend to extend our analysis by performing three-dimensional numerical simulations and investigating the role of different parameters in determining the formation of the X-shaped morphology. Methods: The problem is addressed by numerical means, carrying out three-dimensional relativistic magnetohydrodynamic simulations of bidirectional jets propagating in a triaxial density distribution. Results: We show that only jets with power ≲ 1044 erg s-1 can give origin to an X-shaped morphology and that a misalignment of 30° between the jet axis and the major axis of the density distribution is still favourable to the formation of this kind of morphology. In addition we compute synthetic radio emission maps and polarization maps. Conclusions: In our scenario for the formation of X-shaped radio sources only low power FRII can give origin to such kind of morphology. Our synthetic emission maps show that the different observed morphologies of X-shaped sources can be the result of similar structures viewed under different perspectives.

  14. OPTICAL SPECTRA OF CANDIDATE INTERNATIONAL CELESTIAL REFERENCE FRAME (ICRF) FLAT-SPECTRUM RADIO SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Titov, O.; Stanford, Laura M. [Geoscience Australia, P.O. Box 378, Canberra, ACT 2601 (Australia); Johnston, Helen M.; Hunstead, Richard W. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Pursimo, T. [Nordic Optical Telescope, Nordic Optical Telescope Apartado 474E-38700 Santa Cruz de La Palma, Santa Cruz de Tenerife (Spain); Jauncey, David L. [CSIRO Astronomy and Space Science, ATNF and Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Maslennikov, K. [Central Astronomical Observatory at Pulkovo, Pulkovskoye Shosse, 65/1, 196140, St. Petersburg (Russian Federation); Boldycheva, A., E-mail: oleg.titov@ga.gov.au [Ioffe Physical Technical Institute, 26 Polytekhnicheskaya, St. Petersburg, 194021 (Russian Federation)

    2013-07-01

    Continuing our program of spectroscopic observations of International Celestial Reference Frame (ICRF) sources, we present redshifts for 120 quasars and radio galaxies. Data were obtained with five telescopes: the 3.58 m European Southern Observatory New Technology Telescope, the two 8.2 m Gemini telescopes, the 2.5 m Nordic Optical Telescope (NOT), and the 6.0 m Big Azimuthal Telescope of the Special Astrophysical Observatory in Russia. The targets were selected from the International VLBI Service for Geodesy and Astrometry candidate International Celestial Reference Catalog which forms part of an observational very long baseline interferometry (VLBI) program to strengthen the celestial reference frame. We obtained spectra of the potential optical counterparts of more than 150 compact flat-spectrum radio sources, and measured redshifts of 120 emission-line objects, together with 19 BL Lac objects. These identifications add significantly to the precise radio-optical frame tie to be undertaken by Gaia, due to be launched in 2013, and to the existing data available for analyzing source proper motions over the celestial sphere. We show that the distribution of redshifts for ICRF sources is consistent with the much larger sample drawn from Faint Images of the Radio Sky at Twenty cm (FIRST) and Sloan Digital Sky Survey, implying that the ultra-compact VLBI sources are not distinguished from the overall radio-loud quasar population. In addition, we obtained NOT spectra for five radio sources from the FIRST and NRAO VLA Sky Survey catalogs, selected on the basis of their red colors, which yielded three quasars with z > 4.

  15. Automated detection of extended sources in radio maps: progress from the SCORPIO survey

    Science.gov (United States)

    Riggi, S.; Ingallinera, A.; Leto, P.; Cavallaro, F.; Bufano, F.; Schillirò, F.; Trigilio, C.; Umana, G.; Buemi, C. S.; Norris, R. P.

    2016-08-01

    Automated source extraction and parametrization represents a crucial challenge for the next-generation radio interferometer surveys, such as those performed with the Square Kilometre Array (SKA) and its precursors. In this paper, we present a new algorithm, called CAESAR (Compact And Extended Source Automated Recognition), to detect and parametrize extended sources in radio interferometric maps. It is based on a pre-filtering stage, allowing image denoising, compact source suppression and enhancement of diffuse emission, followed by an adaptive superpixel clustering stage for final source segmentation. A parametrization stage provides source flux information and a wide range of morphology estimators for post-processing analysis. We developed CAESAR in a modular software library, also including different methods for local background estimation and image filtering, along with alternative algorithms for both compact and diffuse source extraction. The method was applied to real radio continuum data collected at the Australian Telescope Compact Array (ATCA) within the SCORPIO project, a pathfinder of the Evolutionary Map of the Universe (EMU) survey at the Australian Square Kilometre Array Pathfinder (ASKAP). The source reconstruction capabilities were studied over different test fields in the presence of compact sources, imaging artefacts and diffuse emission from the Galactic plane and compared with existing algorithms. When compared to a human-driven analysis, the designed algorithm was found capable of detecting known target sources and regions of diffuse emission, outperforming alternative approaches over the considered fields.

  16. A VLA SURVEY FOR FAINT COMPACT RADIO SOURCES IN THE ORION NEBULA CLUSTER

    Energy Technology Data Exchange (ETDEWEB)

    Sheehan, Patrick D.; Eisner, Josh A. [Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Mann, Rita K. [National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Williams, Jonathan P., E-mail: psheehan@email.arizona.edu [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States)

    2016-11-10

    We present Karl G. Jansky Very Large Array 1.3, 3.6, and 6 cm continuum maps of compact radio sources in the Orion Nebular Cluster (ONC). We mosaicked 34 arcmin{sup 2} at 1.3 cm, 70 arcmin{sup 2} at 3.6 cm and 109 arcmin{sup 2} at 6 cm, containing 778 near-infrared detected young stellar objects and 190 Hubble Space Telescope -identified proplyds (with significant overlap between those characterizations). We detected radio emission from 175 compact radio sources in the ONC, including 26 sources that were detected for the first time at these wavelengths. For each detected source, we fitted a simple free–free and dust emission model to characterize the radio emission. We extrapolate the free–free emission spectrum model for each source to ALMA bands to illustrate how these measurements could be used to correctly measure protoplanetary disk dust masses from submillimeter flux measurements. Finally, we compare the fluxes measured in this survey with previously measured fluxes for our targets, as well as four separate epochs of 1.3 cm data, to search for and quantify the variability of our sources.

  17. The radio and optical counterpart of the new Fermi LAT flaring source J0109+6134

    Science.gov (United States)

    Paredes, J. M.; Martí, J.; Peracaula, M.

    2010-02-01

    Following the recent ATELs #2414, #2416 and #2420 concerning the Fermi-LAT, AGILE and Swift/XRT consistent detections of the new gamma-ray flaring source J0109+6134, we wish to remind that the proposed radio counterpart (VCS2 J0109+6133/GT 0106+613) was extensively observed nearly two decades ago by different authors in the context of the GT catalogue of Galactic Plane radio sources (Taylor and Gregory 1983, AJ, 88, 1784; Gregory and Taylor 1986, AJ 92, 371).

  18. Surface plasma source with saddle antenna radio frequency plasma generator.

    Science.gov (United States)

    Dudnikov, V; Johnson, R P; Murray, S; Pennisi, T; Piller, C; Santana, M; Stockli, M; Welton, R

    2012-02-01

    A prototype RF H(-) surface plasma source (SPS) with saddle (SA) RF antenna is developed which will provide better power efficiency for high pulsed and average current, higher brightness with longer lifetime and higher reliability. Several versions of new plasma generators with small AlN discharge chambers and different antennas and magnetic field configurations were tested in the plasma source test stand. A prototype SA SPS was installed in the Spallation Neutron Source (SNS) ion source test stand with a larger, normal-sized SNS AlN chamber that achieved unanalyzed peak currents of up to 67 mA with an apparent efficiency up to 1.6 mA∕kW. Control experiments with H(-) beam produced by SNS SPS with internal and external antennas were conducted. A new version of the RF triggering plasma gun has been designed. A saddle antenna SPS with water cooling is fabricated for high duty factor testing.

  19. Radio measurements in the fields of gamma-ray sources. Pt. 1

    International Nuclear Information System (INIS)

    Sieber, W.; Schlickeiser, R.

    1982-01-01

    The γ-ray source CG 195+04 has been searched for radio counterparts at wavelengths between 2.8 cm and 18 cm with the 100-m telescope of the Max-Planck-Institut fuer Radioastronomie, Bonn. We have detected a number of sources and measured their spectra. Our positions may form the basis for future surveys in other frequency ranges. Different physical emission models suggest compactness of the γ-ray source. (orig.)

  20. Toward Understanding the Fanaroff-Riley Dichotomy in Radio Source Morphology and Power

    Science.gov (United States)

    Baum, Stefi A.; Zirbel, Esther L.; O'Dea, Christopher P.

    1995-09-01

    In Paper I we presented the results of a study of the interrelationships between host galaxy magnitude, optical line luminosity, and radio luminosity in a large sample of Fanaroff-Riley classes 1 and 2 (FR 1 and FR 2) radio galaxies. We report several important differences between the FR 1 and FR 2 radio galaxies. At the same host galaxy magnitude or radio luminosity, the FR 2's produce substantially more optical line emission (by roughly an order of magnitude or more) than do FR 1's. Similarly, FR 2 sources produce orders of magnitude more line luminosity than do radio-quiet galaxies of the same optical magnitude, while FR 1 sources and radio-quiet galaxies of the same optical magnitude produce similar line luminosities. Combining these results with previous results from the literature, we conclude that while the emission-line gas in the FR 2's is indeed photoionized by a nuclear UV continuum source from the AGN, the emission-line gas in the FR 1's may be energized predominantly by processes associated with the host galaxy itself. The apparent lack of a strong UV continuum source from the central engine in FR 1 sources can be understood in two different ways. In the first scenario, FR l's are much more efficient at covering jet bulk kinetic energy into radio luminosity than FR 2's, such that an FR 1 has a much lower bolometric AGN luminosity (hence nuclear UV continuum source) than does an FR 2 of the same radio luminosity. We discuss the pros and cons of this model and conclude that the efficiency differences needed between FR 2 and FR 1 radio galaxies are quite large and may lead to difficulties with the interpretation since it would suggest that FR 2 radio source deposit very large amounts of kinetic energy into the ISM Intracluster Medium. However, this interpretation remains viable. Alternatively, it may be that the AGNs in FR 1 sources simply produce far less radiant UV energy than do those in FR 2 sources. That is, FR 1 sources may funnel a higher fraction

  1. Astronomers Detect Powerful Bursting Radio Source Discovery Points to New Class of Astronomical Objects

    Science.gov (United States)

    2005-03-01

    Astronomers at Sweet Briar College and the Naval Research Laboratory (NRL) have detected a powerful new bursting radio source whose unique properties suggest the discovery of a new class of astronomical objects. The researchers have monitored the center of the Milky Way Galaxy for several years and reveal their findings in the March 3, 2005 edition of the journal, “Nature”. This radio image of the central region of the Milky Way Galaxy holds a new radio source, GCRT J1745-3009. The arrow points to an expanding ring of debris expelled by a supernova. CREDIT: N.E. Kassim et al., Naval Research Laboratory, NRAO/AUI/NSF Principal investigator, Dr. Scott Hyman, professor of physics at Sweet Briar College, said the discovery came after analyzing some additional observations from 2002 provided by researchers at Northwestern University. “"We hit the jackpot!” Hyman said referring to the observations. “An image of the Galactic center, made by collecting radio waves of about 1-meter in wavelength, revealed multiple bursts from the source during a seven-hour period from Sept. 30 to Oct. 1, 2002 — five bursts in fact, and repeating at remarkably constant intervals.” Hyman, four Sweet Briar students, and his NRL collaborators, Drs. Namir Kassim and Joseph Lazio, happened upon transient emission from two radio sources while studying the Galactic center in 1998. This prompted the team to propose an ongoing monitoring program using the National Science Foundation’s Very Large Array (VLA) radio telescope in New Mexico. The National Radio Astronomy Observatory, which operates the VLA, approved the program. The data collected, laid the groundwork for the detection of the new radio source. “Amazingly, even though the sky is known to be full of transient objects emitting at X- and gamma-ray wavelengths,” NRL astronomer Dr. Joseph Lazio pointed out, “very little has been done to look for radio bursts, which are often easier for astronomical objects to produce

  2. Particle acceleration in radio sources with internal turbulence

    International Nuclear Information System (INIS)

    Eilek, J.A.; Henriksen, R.N.

    1982-01-01

    In this paper the authors propose that the flowing plasma displays vortical hydrodynamic turbulence, and that this turbulence drives MHD waves throughout a large portion of the source. They discuss whether the strength and spectrum of the MHD waves generated in this process are sufficient to reaccelerate the particles in the face of synchrotron and expansion losses and the effect that this reacceleration has on the particle spectrum. (Auth.)

  3. Information Sources on U. S. Radio Regulations in the Law Library.

    Science.gov (United States)

    Lockwood, James D.

    An annotated bibliography gives the radio regulations in the U.S., using sources available in the University of Michigan Law Library as well as the University of Michigan Libraries. Information is applicable to other law, university and public libraries. Relevant material on television regulations is included. Listings cover federal agencies, card…

  4. An unusually strong Einstein ring in the radio source PKS1830-211

    International Nuclear Information System (INIS)

    Jauncey, D.L.

    1991-01-01

    RADIO observations of the strong, flat-spectrum radio source PKS1830-211 revealed a double structure, with a separation of 1 arcsec, suggesting that it might be a gravitationally lensed object. We have now obtained high-resolution radio images of PKS1830-211 from several interferometric radiotelescope networks, which show an unusual elliptical ring-like structure connecting the two brighter components. The presence of the ring, and the similarity of the two brighter spots, argue strongly that this is indeed a gravitationally lensed system, specifically an Einstein ring in which lens and lensed object are closely aligned. Although the source is close to the galactic plane, it seems that both the lens and background (lensed) object are extragalactic. This object is one hundred times brighter than either of the two previously discovered radio Einstein rings, and is among the six brightest flat-spectrum sources in the sky. Its brightness makes it a peculiar object: it must involve either a chance alignment of a lensing object with an unusually bright background source, or an alignment with a less bright object but amplified to an unusual degree. (author)

  5. Variability of GPS Radio Sources at 5 GHz Lang Cui , Xiang Liu ...

    Indian Academy of Sciences (India)

    2010-02-07

    Feb 7, 2010 ... Abstract. We carry out flux monitoring on a sample of 169 Gigahertz. Peaked Spectrum (GPS) radio sources at 5 GHz and find that about one- third of them show considerable Inter-Month Variability (IMV), and these. IMV phenomena are likely to be caused by interstellar scintillation (ISS). Furthermore, we ...

  6. A redshift survey of very faint (B <= 22.5) field galaxies, radio sources, and quasars

    International Nuclear Information System (INIS)

    Koo, D.C.

    1983-01-01

    As part of a three year program to study the evolution of quasars, radio sources and galaxies, a 10 night redshift survey has been carried out. A few preliminary results are presented (a magnitude-redshift plot of 54 galaxies). (Auth.)

  7. The use of radio and television as sources of agricultural information ...

    African Journals Online (AJOL)

    This study examined the use of radio and television as sources of agricultural information among poultry farmers in Egbeda Local Government area of Oyo State. Sixty farmers from 4 villages namely: Egbeda, Erunmu, Olode and Owobale were selected for this study. Primary data were collected from the respondents by ...

  8. Multiband Study of Radio Sources of the RCR Catalogue with Virtual Observatory Tools

    Directory of Open Access Journals (Sweden)

    Zhelenkova O. P.

    2012-09-01

    Full Text Available We present early results of our multiband study of the RATAN Cold Revised (RCR catalogue obtained from seven cycles of the “Cold” survey carried with the RATAN-600 radio telescope at 7.6 cm in 1980-1999, at the declination of the SS 433 source. We used the 2MASS and LAS UKIDSS infrared surveys, the DSS-II and SDSS DR7 optical surveys, as well as the USNO-B1 and GSC-II catalogues, the VLSS, TXS, NVSS, FIRST and GB6 radio surveys to accumulate information about the sources. For radio sources that have no detectable optical candidate in optical or infrared catalogues, we additionally looked through images in several bands from the SDSS, LAS UKIDSS, DPOSS, 2MASS surveys and also used co-added frames in different bands. We reliably identified 76% of radio sources of the RCR catalogue. We used the ALADIN and SAOImage DS9 scripting capabilities, interoperability services of ALADIN and TOPCAT, and also other Virtual Observatory (VO tools and resources, such as CASJobs, NED, Vizier, and WSA, for effective data access, visualization and analysis. Without VO tools it would have been problematic to perform our study.

  9. A new non-thermal galactic radio source with a possible binary system

    International Nuclear Information System (INIS)

    Fuerst, E.; Reich, W.; Reich, P.; Sofue, Y.; Handa, T.

    1985-01-01

    A galactic object [G18.95-1.1], detected recently in a galactic plane survey, may belong to a new class of non-thermal radio sources that originate in accreting binary systems. The data on integrated flux density spectral index and the polarization, proves the non-thermal nature of the source. The morphology defies any classification as a supernova remnant. The authors suggest that the object is a binary system containing a compact component. (U.K.)

  10. HIGH-RESOLUTION IMAGING OF THE ATLBS REGIONS: THE RADIO SOURCE COUNTS

    Energy Technology Data Exchange (ETDEWEB)

    Thorat, K.; Subrahmanyan, R.; Saripalli, L.; Ekers, R. D., E-mail: kshitij@rri.res.in [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560080 (India)

    2013-01-01

    The Australia Telescope Low-brightness Survey (ATLBS) regions have been mosaic imaged at a radio frequency of 1.4 GHz with 6'' angular resolution and 72 {mu}Jy beam{sup -1} rms noise. The images (centered at R.A. 00{sup h}35{sup m}00{sup s}, decl. -67 Degree-Sign 00'00'' and R.A. 00{sup h}59{sup m}17{sup s}, decl. -67 Degree-Sign 00'00'', J2000 epoch) cover 8.42 deg{sup 2} sky area and have no artifacts or imaging errors above the image thermal noise. Multi-resolution radio and optical r-band images (made using the 4 m CTIO Blanco telescope) were used to recognize multi-component sources and prepare a source list; the detection threshold was 0.38 mJy in a low-resolution radio image made with beam FWHM of 50''. Radio source counts in the flux density range 0.4-8.7 mJy are estimated, with corrections applied for noise bias, effective area correction, and resolution bias. The resolution bias is mitigated using low-resolution radio images, while effects of source confusion are removed by using high-resolution images for identifying blended sources. Below 1 mJy the ATLBS counts are systematically lower than the previous estimates. Showing no evidence for an upturn down to 0.4 mJy, they do not require any changes in the radio source population down to the limit of the survey. The work suggests that automated image analysis for counts may be dependent on the ability of the imaging to reproduce connecting emission with low surface brightness and on the ability of the algorithm to recognize sources, which may require that source finding algorithms effectively work with multi-resolution and multi-wavelength data. The work underscores the importance of using source lists-as opposed to component lists-and correcting for the noise bias in order to precisely estimate counts close to the image noise and determine the upturn at sub-mJy flux density.

  11. FAINT RADIO-SOURCES WITH PEAKED SPECTRA .1. VLA OBSERVATIONS OF A NEW SAMPLE WITH INTERMEDIATE FLUX-DENSITIES

    NARCIS (Netherlands)

    SNELLEN, IAG; ZHANG, M; SCHILIZZI, RT; ROTTGERING, HJA; DEBRUYN, AG; MILEY, GK

    We present 2 and 20 cm observations with the VLA of 25 candidate peaked spectrum radio sources. These data combined with those from earlier surveys have allowed us to construct radio spectra spanning a range of frequency from 0.3 to 15 GHz. Ten of the 25 sources are found to be variable with no

  12. A search for HI in elliptical galaxies with nuclear radio sources

    International Nuclear Information System (INIS)

    Dressel, L.L.; Bania, T.M.; O'Connell, R.W.

    1982-01-01

    Two of the galaxies with large HI mass, NGC 1052 and 4278, are known to have powerful nuclear continuum radio sources (P 2380 approximately 10 22 WHz -1 ). Since both of these attributes are fairly rare among elliptical galaxies, their coexistence in these galaxies is not likely to have occurred by chance. The authors have therefore observed twelve other elliptical galaxies with nuclear radio power P 2380 > 10 22 WHz -1 at Arecibo Observatory, to determine whether a large mass of HI is a necessary auxillary to nuclear continuum emission. (Auth.)

  13. A radio/optical reference frame. 5: Additional source positions in the mid-latitude southern hemisphere

    Science.gov (United States)

    Russell, J. L.; Reynolds, J. E.; Jauncey, D. L.; de Vegt, C.; Zacharias, N.; Ma, C.; Fey, A. L.; Johnston, K. J.; Hindsley, R.; Hughes, J. A.; Malin, D. F.; White, G. L.; Kawaguchi, N.; Takahashi, Y.

    1994-01-01

    We report new accurate radio position measurements for 30 sources, preliminary positions for two sources, improved radio postions for nine additional sources which had limited previous observations, and optical positions and optical-radio differences for six of the radio sources. The Very Long Baseline Interferometry (VLBI) observations are part of the continuing effort to establish a global radio reference frame of about 400 compact, flat spectrum sources, which are evenly distributed across the sky. The observations were made using Mark III data format in four separate sessions in 1988-89 with radio telescopes at Tidbinbilla, Australia, Kauai, USA, and Kashima, Japan. We observed a total of 54 sources, including ten calibrators and three which were undetected. The 32 new source positions bring the total number in the radio reference frame catalog to 319 (172 northern and 147 southern) and fill in the zone -25 deg greater than delta greater than -45 deg which, prior to this list, had the lowest source density. The VLBI positions have an average formal precision of less than 1 mas, although unknown radio structure effects of about 1-2 mas may be present. The six new optical postion measurements are part of the program to obtain positions of the optical counterparts of the radio reference frame source and to map accurately the optical on to the radio reference frames. The optical measurements were obtained from United States Naval Observatory (USNO) Black Birch astrograph plates and source plates from the AAT, and Kitt Peak National Observatory (KPNO) 4 m, and the European Southern Observatory (ESO) Schmidt. The optical positions have an average precision of 0.07 sec, mostly due to the zero point error when adjusted to the FK5 optical frame using the IRS catalog. To date we have measured optical positions for 46 sources.

  14. New complete sample of identified radio sources. Part 2. Statistical study

    International Nuclear Information System (INIS)

    Soltan, A.

    1978-01-01

    Complete sample of radio sources with known redshifts selected in Paper I is studied. Source counts in the sample and the luminosity - volume test show that both quasars and galaxies are subject to the evolution. Luminosity functions for different ranges of redshifts are obtained. Due to many uncertainties only simplified models of the evolution are tested. Exponential decline of the liminosity with time of all the bright sources is in a good agreement both with the luminosity- volume test and N(S) realtion in the entire range of observed flux densities. It is shown that sources in the sample are randomly distributed in scales greater than about 17 Mpc. (author)

  15. An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102

    Science.gov (United States)

    Michilli, D.; Seymour, A.; Hessels, J. W. T.; Spitler, L. G.; Gajjar, V.; Archibald, A. M.; Bower, G. C.; Chatterjee, S.; Cordes, J. M.; Gourdji, K.; Heald, G. H.; Kaspi, V. M.; Law, C. J.; Sobey, C.; Adams, E. A. K.; Bassa, C. G.; Bogdanov, S.; Brinkman, C.; Demorest, P.; Fernandez, F.; Hellbourg, G.; Lazio, T. J. W.; Lynch, R. S.; Maddox, N.; Marcote, B.; McLaughlin, M. A.; Paragi, Z.; Ransom, S. M.; Scholz, P.; Siemion, A. P. V.; Tendulkar, S. P.; van Rooy, P.; Wharton, R. S.; Whitlow, D.

    2018-01-01

    Fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. The only known repeating fast radio burst source—FRB 121102—has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46 × 105 radians per square metre to +1.33 × 105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.

  16. INVESTIGATING PARTICLE ACCELERATION IN PROTOSTELLAR JETS: THE TRIPLE RADIO CONTINUUM SOURCE IN SERPENS

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez-Kamenetzky, Adriana; Valotto, Carlos [Instituto de Astronomía Teórica y Experimental, (IATE-UNC), X5000BGR Córdoba (Argentina); Carrasco-González, Carlos; Rodríguez, Luis F. [Instituto de Radioastronomía y Astrofísica (IRyA-UNAM), 58089 Morelia, México (Mexico); Araudo, Anabella [University of Oxford, Astrophysics, Keble Road, Oxford OX1 3RH (United Kingdom); Torrelles, José M. [Institut de Ciències de l’Espai (CSIC-IEEC) and Institut de Ciències del Cosmos (UB-IEEC), Martí i Franquès 1, E-08028 Barcelona (Spain); Anglada, Guillem [Instituto de Astrofísica de Andalucía, CSIC, Camino Bajo de Huétor 50, E-18008 Granada (Spain); Martí, Josep [Dept. de Física, EPS de Jaén, Universidad de Jaén, Campus Las Lagunillas s/n, A3-402, E-23071 Jaén (Spain)

    2016-02-10

    While most protostellar jets present free–free emission at radio wavelengths, synchrotron emission has also been proposed to be present in a handful of these objects. The presence of nonthermal emission has been inferred by negative spectral indices at centimeter wavelengths. In one case (the HH 80-81 jet arising from a massive protostar), its synchrotron nature was confirmed by the detection of linearly polarized radio emission. One of the main consequences of these results is that synchrotron emission implies the presence of relativistic particles among the nonrelativistic material of these jets. Therefore, an acceleration mechanism should be taking place. The most probable scenario is that particles are accelerated when the jets strongly impact against the dense envelope surrounding the protostar. Here we present an analysis of radio observations obtained with the Very Large Array of the triple radio source in the Serpens star-forming region. This object is known to be a radio jet arising from an intermediate-mass protostar. It is also one of the first protostellar jets where the presence of nonthermal emission was proposed. We analyze the dynamics of the jet and the nature of the emission and discuss these issues in the context of the physical parameters of the jet and the particle acceleration phenomenon.

  17. Electron energy spectrum produced in radio sources by turbulent, resonant acceleration

    International Nuclear Information System (INIS)

    Eilek, J.A.; Henriksen, R.N.

    1984-01-01

    We consider relativistic particle acceleration by resonant Alfven waves which are driven internally in a radio source from fully developed fluid turbulence. We find that self-similar behavior as described by Lacombe, f(p)proportionalp - /sup s/ but with sroughly-equal4.5, arises self-consistently when this turbulent wave driving coexists with synchrotron losses. The coupling of the wave and particle distributions provides feedback which drives an arbitrary initial distribution to the form-stable, self-similar form. The model predicts that turbulent plasma in a radio source should evolve toward a synchrotron spectral index, 0.5< or approx. =α< or approx. =1.0 in one particle lifetime, and that the average spectrum of most sources should also be in this range. The theory may also be applicable to other turbulent sites, such as cosmic-ray reaccelertion in the interstellar medium

  18. Evolution in linear sizes and the Faraday effects in radio sources

    International Nuclear Information System (INIS)

    Anene, G.; Ugwoke, A.C.

    2001-05-01

    It is still a matter of conjecture whether the observed depolarization in radio sources originate from an external Faraday screen lying in our line of sight, or is largely due to internal processes occurring within these sources. This paper argues for an external origin. By applying recent evidences from the evolution of linear sizes while allowing for selection effects, it is shown that the density parameters within radio sources do not depend on redshift, implying that the observed depolarizations is epoch independent and may therefore, be largely external in origin. We also show that the observed low correlation between λ 1/2 and linear size(D) cannot be improved much even when allowance is made for evolution in D. (author)

  19. Exploring three faint source detections methods for aperture synthesis radio images

    Science.gov (United States)

    Peracaula, M.; Torrent, A.; Masias, M.; Lladó, X.; Freixenet, J.; Martí, J.; Sánchez-Sutil, J. R.; Muñoz-Arjonilla, A. J.; Paredes, J. M.

    2015-04-01

    Wide-field radio interferometric images often contain a large population of faint compact sources. Due to their low intensity/noise ratio, these objects can be easily missed by automated detection methods, which have been classically based on thresholding techniques after local noise estimation. The aim of this paper is to present and analyse the performance of several alternative or complementary techniques to thresholding. We compare three different algorithms to increase the detection rate of faint objects. The first technique consists of combining wavelet decomposition with local thresholding. The second technique is based on the structural behaviour of the neighbourhood of each pixel. Finally, the third algorithm uses local features extracted from a bank of filters and a boosting classifier to perform the detections. The methods' performances are evaluated using simulations and radio mosaics from the Giant Metrewave Radio Telescope and the Australia Telescope Compact Array. We show that the new methods perform better than well-known state of the art methods such as SEXTRACTOR, SAD and DUCHAMP at detecting faint sources of radio interferometric images.

  20. SOURCE REGIONS OF THE TYPE II RADIO BURST OBSERVED DURING A CME–CME INTERACTION ON 2013 MAY 22

    International Nuclear Information System (INIS)

    Mäkelä, P.; Reiner, M. J.; Akiyama, S.; Gopalswamy, N.; Krupar, V.

    2016-01-01

    We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind /WAVES and STEREO /WAVES (SWAVES) radio observations at decameter–hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source, indicating that the spatial location of the dominant source of the type II emission varies during the CME–CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME–CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.

  1. Interstellar scattering, the North Polar Spur, and a possible new class of compact galactic radio sources

    International Nuclear Information System (INIS)

    Rickard, J.J.; Cronyn, W.M.

    1979-01-01

    A reanalysis of the Cambridge interplanetary scintillation (IPS) catalog of angular sizes of radio sources reveals that there is no statistically significant evidence for increased interstellar angular broadening in the galactic plane, in conflict with previous studies. There is a significant contribution to the decrease in the ratios of scintillators/nonscintillators and strong/weak scintillators near the plane from galactic supernova remnants which were included in previous studies of source counts. Using the catalog angular sizes, we show there is no lack of small sources of any size in the plane. However, we do find a 500 deg 2 region near the North Polar Spur (NPS) radio feature, a suspected supernova remnant, where there seems to be a true deficit of small sources. This deficit may be caused by enhanced broadening associated with the NPS. Our conclusion about the apparent absence of angular broadening in the plane conflicts with estimates of broadening based upon the geometrical relationship between time delay and angular size applied to pulsar coherence bandwidths and pulse decay times. To explain this discrepancy, we suggest two alternatives: (1) Large angular broadening of extragalactic sources in the plane may indeed exist so that sources exhibiting IPS (i.e., of small angular diameter) must be galactic in nature. Properties of this possible new class of sources--called scintars--are discussed, and 42 scintar candidates are identified. (2) There is little angular broadening of extragalactic sources, and the pulsar data are being misinterpreted

  2. MERLIN observations of steep-spectrum radio sources at 6 cm

    International Nuclear Information System (INIS)

    Akujor, C.E.; Zhang, F.J.; Fanti, C.

    1991-01-01

    We present high-resolution observations of steep-spectrum radio sources made with MERLIN at 5 GHz. Thirty-one objects, comprising 11 quasars and 20 galaxies, most of them being 'Compact Steep-Spectrum' sources (CSSs), have been mapped with resolutions from 80 to 150 mas. This completes the current series of observations of CSS sources made with MERLIN at 5 GHz. We find that the majority of the quasars have complex structures, while galaxies tend to have double or triple structures, consistent with other recent studies of CSSs. (author)

  3. Double radio sources and the new approach to cosmic plasma physics

    International Nuclear Information System (INIS)

    Alfven, H.

    1977-08-01

    The methodology of cosmic plasma physics is discussed. A summary is given of laboratory investigations of electric double layers, a phenomenon which is known to be very important in laboratory discharges. The importance of electric double layers in the Earth's surrounding is established. The scaling laws between laboratory and magnetospheric double layers are studied. A further extrapolation to galactic phenomena leads to a theory of double radio sources. From analogy with laboratory and magnetospheric current systems it is argued that the galactic current might produce double layers where a large energy dissipation takes place. This leads to a theory of the double radio sources which within the necessary wide limits of uncertainty is quantitatively reconcilable with observations. (author)

  4. Star Formation Rates in Lyman Break Galaxies: Radio Stacking of LBGs in the COSMOS Field and the Sub-μJy Radio Source Population

    Science.gov (United States)

    Carilli, C. L.; Lee, Nicholas; Capak, P.; Schinnerer, E.; Lee, K.-S.; McCraken, H.; Yun, M. S.; Scoville, N.; Smolčić, V.; Giavalisco, M.; Datta, A.; Taniguchi, Y.; Urry, C. Megan

    2008-12-01

    We present an analysis of the radio properties of large samples of Lyman break galaxies (LBGs) at z ~ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ~ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 +/- 0.21 μJy. The stacked emission is unresolved, with a size = 3 is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are (1) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift or (2) cosmic-ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a "submillimeter galaxy"). Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4 m, CTIO 4 m, and CFHT 3.6 m. The Very Large Array of the National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  5. Mechanical design of SXLS [Superconducting X-ray Lithography Source] radio-frequency cavity

    International Nuclear Information System (INIS)

    Mortazavi, P.; Sharma, S.; Keane, J.; Thomas, M.

    1989-01-01

    This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs

  6. Mechanical design of SXLS (Superconducting X-ray Lithography Source) radio-frequency cavity

    Energy Technology Data Exchange (ETDEWEB)

    Mortazavi, P.; Sharma, S.; Keane, J.; Thomas, M.

    1989-01-01

    This paper presents the mechanical design of a Radio-Frequency (RF) cavity to be used on a compact storage ring for Superconducting X-ray Lithography Source (SXLS). Various design features of this cavity are discussed, including basic geometrical configuration, structural design, initial and operational tuning, vacuum multipactoring, power window, and damping of higher order modes. A second application of this cavity design for beam life extension in an existing storage ring is also described. 2 refs., 6 figs.

  7. An analysis of interplanetary scintillation as a method of measuring the angular sizes of radio sources

    International Nuclear Information System (INIS)

    Hajivassiliou, C.A.; Duffett-Smith, P.J.

    1990-01-01

    Interplanetary scintillation has been widely used at metre wavelengths for estimating the angular sizes of radio sources in the range 0.1-2.0 arcsec. The estimates are based on observations of either the width of the temporal power spectrum or the shape of the scintillation index-elongation curve. We present a mathematical model of the latter procedure which reveals the biases introduced into an IPS survey as a result of the estimation process. (author)

  8. Relativistic jet with shock waves like model of superluminal radio source. Jet relativista con ondas de choque como modelo de radio fuentes superluminales

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, A.; Gomez, J.L.; Marcaide, J.M.

    1993-01-01

    The structure of the compact radio sources at milliarcsecond angular resolution can be explained in terms of shock waves propagating along bent jets. These jets consist of narrow-angle cones of plasma flowing at bulk relativistic velocities, within tangled magnetic fields, emitting synchrotron radiation. We have developed a numerical code which solves the synchrotron radiation transfer equations to compute the total and polarized emission of bent shocked relativistic jets, and we have applied it to reproduce the compact structure, kenimatic evolution and time flux density evolution of the superluminal radio source 4C 39.25 and to obtain its jet physical parameters. (Author) 23 ref.

  9. Two-Component Structure of the Radio Source 0014+813 from VLBI Observations within the CONT14 Program

    Science.gov (United States)

    Titov, O. A.; Lopez, Yu. R.

    2018-03-01

    We consider a method of reconstructing the structure delay of extended radio sources without constructing their radio images. The residuals derived after the adjustment of geodetic VLBI observations are used for this purpose. We show that the simplest model of a radio source consisting of two point components can be represented by four parameters (the angular separation of the components, the mutual orientation relative to the poleward direction, the flux-density ratio, and the spectral index difference) that are determined for each baseline of a multi-baseline VLBI network. The efficiency of this approach is demonstrated by estimating the coordinates of the radio source 0014+813 observed during the two-week CONT14 program organized by the International VLBI Service (IVS) in May 2014. Large systematic deviations have been detected in the residuals of the observations for the radio source 0014+813. The averaged characteristics of the radio structure of 0014+813 at a frequency of 8.4 GHz can be calculated from these deviations. Our modeling using four parameters has confirmed that the source consists of two components at an angular separation of 0.5 mas in the north-south direction. Using the structure delay when adjusting the CONT14 observations leads to a correction of the average declination estimate for the radio source 0014+813 by 0.070 mas.

  10. THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

    International Nuclear Information System (INIS)

    Rodríguez, Luis F.; Loinard, Laurent; Zapata, Luis; Lizano, Susana; Dzib, Sergio A.; Menten, Karl M.; Gómez, Laura

    2017-01-01

    We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of kilometers per second from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free–free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475 ± 6, when they were within ∼100 au or less from each other in the plane of the sky.

  11. THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Luis F.; Loinard, Laurent; Zapata, Luis; Lizano, Susana [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Dzib, Sergio A.; Menten, Karl M. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Gómez, Laura, E-mail: l.rodriguez@crya.unam.mx [Joint ALMA Observatory, Alonso de Córdoba 3107, Vitacura, Santiago (Chile)

    2017-01-10

    We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of kilometers per second from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free–free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475 ± 6, when they were within ∼100 au or less from each other in the plane of the sky.

  12. THE Q/U IMAGING EXPERIMENT: POLARIZATION MEASUREMENTS OF RADIO SOURCES AT 43 AND 95 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Huffenberger, K. M. [Department of Physics, Florida State University, P.O. Box 3064350, Tallahassee, FL 32306-4350 (United States); Araujo, D.; Zwart, J. T. L. [Department of Physics and Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Bischoff, C.; Buder, I. [Kavli Institute for Cosmological Physics, Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637 (United States); Chinone, Y.; Hasegawa, M. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Cleary, K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, 1200 E. California Blvd M/C 249-17, Pasadena, CA 91125 (United States); Kusaka, A. [Physics Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Monsalve, R. [School of Earth and Space Exploration, Arizona State University, 781 E. Terrace Road, Tempe, AZ 85287 (United States); Næss, S. K. [Department of Astrophysics, University of Oxford, Keble Road, Oxford, OX1 3RH (United Kingdom); Newburgh, L. B. [Dunlap Institute, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Reeves, R. [CePIA, Departamento de Astronomía, Universidad de Concepción (Chile); Ruud, T. M.; Eriksen, H. K. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway); Wehus, I. K.; Gaier, T. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Dickinson, C. [Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Gundersen, J. O., E-mail: huffenbe@physics.fsu.edu [Department of Physics, University of Miami, 1320 Campo Sano Drive, Coral Gables, FL 33146 (United States); Collaboration: QUIET Collaboration; and others

    2015-06-10

    We present polarization measurements of extragalactic radio sources observed during the cosmic microwave background polarization survey of the Q/U Imaging Experiment (QUIET), operating at 43 GHz (Q-band) and 95 GHz (W-band). We examine sources selected at 20 GHz from the public, >40 mJy catalog of the Australia Telescope (AT20G) survey. There are ∼480 such sources within QUIET’s four low-foreground survey patches, including the nearby radio galaxies Centaurus A and Pictor A. The median error on our polarized flux density measurements is 30–40 mJy per Stokes parameter. At signal-to-noise ratio > 3 significance, we detect linear polarization for seven sources in Q-band and six in W-band; only 1.3 ± 1.1 detections per frequency band are expected by chance. For sources without a detection of polarized emission, we find that half of the sources have polarization amplitudes below 90 mJy (Q-band) and 106 mJy (W-band), at 95% confidence. Finally, we compare our polarization measurements to intensity and polarization measurements of the same sources from the literature. For the four sources with WMAP and Planck intensity measurements >1 Jy, the polarization fractions are above 1% in both QUIET bands. At high significance, we compute polarization fractions as much as 10%–20% for some sources, but the effects of source variability may cut that level in half for contemporaneous comparisons. Our results indicate that simple models—ones that scale a fixed polarization fraction with frequency—are inadequate to model the behavior of these sources and their contributions to polarization maps.

  13. Note: A versatile radio-frequency source for cold atom experiments

    Energy Technology Data Exchange (ETDEWEB)

    Li, Na; Wu, Yu-Ping; Min, Hao; Yang, Tao; Jiang, Xiao, E-mail: jiangx@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2016-08-15

    A radio-frequency (RF) source designed for cold atom experiments is presented. The source uses AD9858, a direct digital synthesizer, to generate the sine wave directly, up to 400 MHz, with sub-Hz resolution. An amplitude control circuit consisting of wideband variable gain amplifier and high speed digital to analog converter is integrated into the source, capable of 70 dB off isolation and 4 ns on-off keying. A field programmable gate array is used to implement a versatile frequency and amplitude co-sweep logic. Owing to modular design, the RF sources have been used on many cold atom experiments to generate various complicated RF sequences, enriching the operation schemes of cold atoms, which cannot be done by standard RF source instruments.

  14. Operating experience of upgraded radio frequency source at 76 MHz coupled to heavy ion RFQ

    International Nuclear Information System (INIS)

    Pande, Manjiri; Shiju, A.; Patel, N.R.; Shrotriya, S.D.; Bhagwat, P.V.

    2015-01-01

    A heavy ion radio frequency quadrupole (RFQ) accelerator has been developed at BARC (BARC). A RF source which was designed and developed at 76 MHz earlier, has been upgraded and coupled to heavy ion RFQ successfully. The DC bias supplies of this source have been replaced with new supplies having high efficiency and well filteration against RF interference (RFI). The driver of main power amplifier has been replaced with indigenously designed and developed unit. The earlier introduced microcontroller based interlock experienced RF noise issues. So, this circuit has been modified with the new circuit. With these modifications, the performance of the RF source was improved. Additionally, a separate low power RF source of around 100 + Watt was designed, developed and integrated with RFQ for its RF conditioning. This paper describes the details of up gradation of technologies implemented and coupling experience of this RF source with heavy ion RFQ. (author)

  15. 318-MHz variability of complete samples of extragalactic radio sources. II

    International Nuclear Information System (INIS)

    Dennison, B.; Broderick, J.J.; Ledden, J.E.; O'Dell, S.L.; Condon, J.J.

    1981-01-01

    We report the remainder of two- and three-epoch 318-MHz observations of extragalactic sources in samples complete to 3 Jy at 1400 MHz and 1 Jy at 5000 MHz. From analysis of this low-frequency variability survey, we find that steep-spectrum (α> or =0.5) sources do not appear to vary, but about 40% of all flat-spectrum (α<0.5) sources exhibit low-frequency variability exceeding 8% over approx.5 yr. Among the flat-spectrum sources, those with inverted spectra show the largest fractional variations. We also find that the incidence of low-frequency variability is strongly correlated with the determination that a source is an optically violent variable. These statistical properties are consistent with models invoking relativistic beaming of radio and optical emission

  16. Stabilized operation of the Spallation Neutron Source radio-frequency quadrupole

    Directory of Open Access Journals (Sweden)

    Sang-ho Kim

    2010-07-01

    Full Text Available The Spallation Neutron Source (SNS radio-frequency quadrupole (RFQ had resonance control instabilities at duty factors higher than approximately 4%. Systematic investigations have been carried out to understand the cause of the instability and to ensure the operational stability of the RFQ. The most critical source of the instability is revealed to be an interaction between hydrogen released by beam bombardments and the RFQ rf field resulting in a discharge, which consumes additional rf power and could cause the RFQ to operate in an unstable region. This paper reports improvement of the SNS RFQ operational stability based on the findings during the SNS operation.

  17. 10C survey of radio sources at 15.7 GHz - II. First results

    Science.gov (United States)

    AMI Consortium; Davies, Mathhew L.; Franzen, Thomas M. O.; Waldram, Elizabeth M.; Grainge, Keith J. B.; Hobson, Michael P.; Hurley-Walker, Natasha; Lasenby, Anthony; Olamaie, Malak; Pooley, Guy G.; Riley, Julia M.; Rodríguez-Gonzálvez, Carmen; Saunders, Richard D. E.; Scaife, Anna M. M.; Schammel, Michel P.; Scott, Paul F.; Shimwell, Timothy W.; Titterington, David J.; Zwart, Jonathan T. L.

    2011-08-01

    In a previous paper (Paper I), the observational, mapping and source-extraction techniques used for the Tenth Cambridge (10C) Survey of Radio Sources were described. Here, the first results from the survey, carried out using the Arcminute Microkelvin Imager Large Array (LA) at an observing frequency of 15.7 GHz, are presented. The survey fields cover an area of ≈27 deg2 to a flux-density completeness of 1 mJy. Results for some deeper areas, covering ≈12 deg2, wholly contained within the total areas and complete to 0.5 mJy, are also presented. The completeness for both areas is estimated to be at least 93 per cent. The 10C survey is the deepest radio survey of any significant extent (≳0.2 deg2) above 1.4 GHz. The 10C source catalogue contains 1897 entries and is available online. The source catalogue has been combined with that of the Ninth Cambridge Survey to calculate the 15.7-GHz source counts. A broken power law is found to provide a good parametrization of the differential count between 0.5 mJy and 1 Jy. The measured source count has been compared with that predicted by de Zotti et al. - the model is found to display good agreement with the data at the highest flux densities. However, over the entire flux-density range of the measured count (0.5 mJy to 1 Jy), the model is found to underpredict the integrated count by ≈30 per cent. Entries from the source catalogue have been matched with those contained in the catalogues of the NRAO VLA Sky Survey and the Faint Images of the Radio Sky at Twenty-cm survey (both of which have observing frequencies of 1.4 GHz). This matching provides evidence for a shift in the typical 1.4-GHz spectral index to 15.7-GHz spectral index of the 15.7-GHz-selected source population with decreasing flux density towards sub-mJy levels - the spectra tend to become less steep. Automated methods for detecting extended sources, developed in Paper I, have been applied to the data; ≈5 per cent of the sources are found to be extended

  18. CHANDRA OBSERVATIONS OF 3C RADIO SOURCES WITH z < 0.3. II. COMPLETING THE SNAPSHOT SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Tremblay, G. R. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei Muenchen (Germany); Harris, D. E.; O' Dea, C. P. [Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Kharb, P.; Axon, D. [Department of Physics, Rochester Institute of Technology, Carlson Center for Imaging Science 76-3144, 84 Lomb Memorial Dr., Rochester, NY 14623 (United States); Balmaverde, B.; Capetti, A. [INAF-Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (Italy); Baum, S. A. [Carlson Center for Imaging Science 76-3144, 84 Lomb Memorial Dr., Rochester, NY 14623 (United States); Chiaberge, M.; Macchetto, F. D.; Sparks, W. [Space Telescope Science Institute, 3700 San Martine Drive, Baltimore, MD 21218 (United States); Gilli, R. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Giovannini, G. [INAF-Istituto di Radioastronomia di Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Grandi, P.; Torresi, E. [INAF-IASF-Istituto di Astrofisica Spaziale e fisica Cosmica di Bologna, Via P. Gobetti 101, I-40129 Bologna (Italy); Risaliti, G. [INAF-Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy)

    2012-12-15

    We report on the second round of Chandra observations of the 3C snapshot survey developed to observe the complete sample of 3C radio sources with z < 0.3 for 8 ks each. In the first paper, we illustrated the basic data reduction and analysis procedures performed for the 30 sources of the 3C sample observed during Chandra Cycle 9, while here we present the data for the remaining 27 sources observed during Cycle 12. We measured the X-ray intensity of the nuclei and of any radio hot spots and jet features with associated X-ray emission. X-ray fluxes in three energy bands, i.e., soft, medium, and hard, for all the sources analyzed are also reported. For the stronger nuclei, we also applied the standard spectral analysis, which provides the best-fit values of the X-ray spectral index and absorbing column density. In addition, a detailed analysis of bright X-ray nuclei that could be affected by pile-up has been performed. X-ray emission was detected for all the nuclei of the radio sources in our sample except for 3C 319. Among the current sample, there are two compact steep spectrum radio sources, two broad-line radio galaxies, and one wide angle tail radio galaxy, 3C 89, hosted in a cluster of galaxies clearly visible in our Chandra snapshot observation. In addition, we also detected soft X-ray emission arising from the galaxy cluster surrounding 3C 196.1. Finally, X-ray emission from hot spots has been found in three FR II radio sources and, in the case of 3C 459, we also report the detection of X-ray emission associated with the eastern radio lobe as well as X-ray emission cospatial with radio jets in 3C 29 and 3C 402.

  19. Occultations of Astrophysical Radio Sources as Probes of Planetary Environments: A Case Study of Jupiter and Possible Applications to Exoplanets

    Energy Technology Data Exchange (ETDEWEB)

    Withers, Paul [Astronomy Department, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Vogt, Marissa F. [Center for Space Physics, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States)

    2017-02-10

    Properties of planetary atmospheres, ionospheres, and magnetospheres are difficult to measure from Earth. Radio occultations are a common method for measuring these properties, but they traditionally rely on radio transmissions from a spacecraft near the planet. Here, we explore whether occultations of radio emissions from a distant astrophysical radio source can be used to measure magnetic field strength, plasma density, and neutral density around planets. In a theoretical case study of Jupiter, we find that significant changes in polarization angle due to Faraday rotation occur for radio signals that pass within 10 Jupiter radii of the planet and that significant changes in frequency and power occur from radio signals that pass through the neutral atmosphere. There are sufficient candidate radio sources, such as pulsars, active galactic nuclei, and masers, that occultations are likely to occur at least once per year. For pulsars, time delays in the arrival of their emitted pulses can be used to measure plasma density. Exoplanets, whose physical properties are very challenging to observe, may also occult distant astrophysical radio sources, such as their parent stars.

  20. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    Energy Technology Data Exchange (ETDEWEB)

    D' Abrusco, R.; Paggi, A.; Smith, H. A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Massaro, F. [Dipartimento di Fisica, Università degli Studi di Torino, via Pietro Giuria 1, I-10125 Torino (Italy); Masetti, N. [INAF/IASF di Bologna, via Gobetti 101, I-40129 Bologna (Italy); Landoni, M. [INAF/Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (Italy); Tosti, G. [Dipartimento di Fisica, Università degli Studi di Perugia, I-06123 Perugia (Italy)

    2014-11-01

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q {sub 22} parameter, which is analogous to the q {sub 24} parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources.

  1. Physics of compact radio sources. I. Particle acceleration and flux variations

    International Nuclear Information System (INIS)

    Pacholczyk, A.G.; Scott, J.S.

    1976-01-01

    The observed patterns of variability of compact radio sources may be explained by assuming that the radio components are plasmons containing relativistic particles, and by applying a model with the following features: (1) the plasmons are ejected at high speed into the interstellar medium in the nuclei of active galaxies: (2) ram pressure confinement of the plasmons leads to Rayleigh-Taylor and Kelvin-Helmholtz instabilities therein; (3) turbulence is thereby introduced into the plasmons; (4) the turbulence amplifies the plasmon magnetic field (for a short period) and this leads to betatron aceleration of the relativistic particles; (5) the turbulence vortices continue to accelerate the particles by the second-order Fermi acceleration mechanism. The emission patterns are the result of the combination of these accelerations and adiabatic losses

  2. Methods for the determination of lunisolar precession from observations of extragalactic radio sources

    International Nuclear Information System (INIS)

    Elsmore, B.

    1976-01-01

    Although it is not practicable at present to determine the position or motion of the equinox using radio techniques, lunisolar precession may be determined from measurements at two epochs of differences of (i) Right Ascension -RA, and (ii) Declinations - Dec., of extragalactic radio sources. The determinations are largely free from systematic errors, and the magnitudes of random errors, arising principally from tropospheric irregularities, are given for observations with the Cambridge 5-km telescope. Some first epoch measure-ments have been made with this instrument and it is estimated that by carrying out second epoch measurements after an interval of 5 yr, the centennial value of lunisolar precession will be determined with a standard error of +- 0''.25. (author)

  3. Opacity in compact extragalactic radio sources and the core shift effect

    International Nuclear Information System (INIS)

    Kovalev, Y Y; Lobanov, A P; Pushkarev, A B; Zensus, J A

    2008-01-01

    The apparent position of the 'core' in a parsec-scale radio jet (a compact, bright emitting region at the narrow end of the jet) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. This dependency both provides a tool to probe physical conditions in the vicinity of the core and poses problems for astrometric studies using compact radio sources. We investigate the frequency-dependent shift of the positions of the cores (core shift) observed with very long baseline interferometry (VLBI) in parsec-scale jets. We present results for 29 selected active galactic nuclei (AGN). In these AGN, the magnitude of the measured core shift between 2.3 and 8.6 GHz reaches 1.4 mas, with a median value for the sample of 0.44 mas. We discuss related physics as well as astrometry applications and plans for further studies.

  4. Flux density measurements of radio sources at 2.14 millimeter wavelength

    International Nuclear Information System (INIS)

    Cogdell, J.R.; Davis, J.H.; Ulrich, B.T.; Wills, B.J.

    1975-01-01

    Flux densities of galactic and extragalactic sources, and planetary temperatures, have been measured at 2.14 mm wavelength (140 GHz). Results are presented for OJ 287; the galactic sources DR 21, W3, and Orion A; the extragalactic sources PKS 0106plus-or-minus01, 3C 84, 3C 120, BL Lac, 3C 216, 3C 273, 3C 279, and NGC 4151; and the Sun, Venus, Mars, and Jupiter. Also presented is the first measurement of the 2.14-mm temperature of Uranus. The spectra of some of these sources are discussed. The flux density scale was calibrated absolutely. The measurements were made with a new continuum receiver on the 4.88-m radio telescope of The University of Texas

  5. Compact radio and infrared sources near the centre of the bipolar outflow NGC 2264D

    International Nuclear Information System (INIS)

    Mendoza, E.E.; Rodriguez, L.F.; Chavarria-K, C.; Neri, L.

    1990-01-01

    A multi-frequency study of the central region of the bipolar outflow NGC 2264D in the Monoceros OB1 molecular cloud has been made in an attempt to localize and understand its driving source. We have detected a weak (≅ 0.6 mJy) radio continuum source at 6 cm, using the VLA; a bright (≅ 270 Jy) H 2 O maser, using the Haystack Observatory telescope; and near-infrared counterparts to these sources at San Pedro Martir Observatory. Stromgren and JHKL'M photometry of stellar objects in the region was also carried out at this observatory. The star-like object W166, a probable Herbig Be/Ae star, which has strong Hα emission and a near-infrared excess, is located closest to the centroid of the bipolar outflow and is probably its driving source. (author)

  6. Scintillating confusion: Evaluation of a technique for measuring compact structure in weak radio sources

    International Nuclear Information System (INIS)

    Spangler, S.R.; Cordes, J.M.; Meyers, K.A.

    1979-01-01

    An attractive scheme for investigating compact structure in weak radio sources is to study the scintillation properties of confusion in a large single-dish radio telescope. We have investigated the utility of this technique by observing the scintillations of 860-MHz confusion of the NRAO 300' (91 m) telescope. Analysis of these data indicated a reduction in the mean scintillation index with decreasing flux density which implied that weaker sources possessed less compact structure. More direct observations indicated that the weak sources of interest were not significantly deficient in compact structure, so the first result is probably due to properties of the IPS process in the strong scintillation regime. Our results may be due to overresolution (by the IPS process in the strong scintillation regime) of the ''hot spots'' responsible for scintillation in most strong sources at frequencies below 1000 MHz, or may indicate abnormally strong turbulence in the solar wind during August, 1977. Future applications of this method would be best conducted at lower frequencies with larger reflectors or short-spacing interferometers

  7. A 31 GHz Survey of Low-Frequency Selected Radio Sources

    Science.gov (United States)

    Mason, B. S.; Weintraub, L.; Sievers, J.; Bond, J. R.; Myers, S. T.; Pearson, T. J.; Readhead, A. C. S.; Shepherd, M. C.

    2009-10-01

    The 100 m Robert C. Byrd Green Bank Telescope and the 40 m Owens Valley Radio Observatory telescope have been used to conduct a 31 GHz survey of 3165 known extragalactic radio sources over 143 deg2 of the sky. Target sources were selected from the NRAO VLA Sky Survey in fields observed by the Cosmic Background Imager (CBI); most are extragalactic active galactic nuclei (AGNs) with 1.4 GHz flux densities of 3-10 mJy. The resulting 31 GHz catalogs are presented in full online. Using a maximum-likelihood analysis to obtain an unbiased estimate of the distribution of the 1.4-31 GHz spectral indices of these sources, we find a mean 31-1.4 GHz flux ratio of 0.110 ± 0.003 corresponding to a spectral index of α = -0.71 ± 0.01 (S ν vprop να) 9.0% ± 0.8% of sources have α > - 0.5 and 1.2% ± 0.2% have α > 0. By combining this spectral-index distribution with 1.4 GHz source counts, we predict 31 GHz source counts in the range 1 mJy S 31) = (16.7 ± 1.7) deg-2(S 31/1 mJy)-0.80±0.07. We also assess the contribution of mJy-level (S 1.4 GHz < 3.4 mJy) radio sources to the 31 GHz cosmic microwave background power spectrum, finding a mean power of ell(ell + 1)C src ell/(2π) = 44 ± 14 μK2 and a 95% upper limit of 80 μK2 at ell = 2500. Including an estimated contribution of 12 μK2 from the population of sources responsible for the turn-up in counts below S 1.4 GHz = 1 mJy, this amounts to 21% ± 7% of what is needed to explain the CBI high-ell excess signal, 275 ± 63 μK2. These results are consistent with other measurements of the 31 GHz point-source foreground.

  8. The distribution of polarized radio sources >15 μJy IN GOODS-N

    International Nuclear Information System (INIS)

    Rudnick, L.; Owen, F. N.

    2014-01-01

    We present deep Very Large Array observations of the polarization of radio sources in the GOODS-N field at 1.4 GHz at resolutions of 1.''6 and 10''. At 1.''6, we find that the peak flux cumulative number count distribution is N(> p) ∼ 45*(p/30 μJy) –0.6 per square degree above a detection threshold of 14.5 μJy. This represents a break from the steeper slopes at higher flux densities, resulting in fewer sources predicted for future surveys with the Square Kilometer Array and its precursors. It provides a significant challenge for using background rotation measures (RMs) to study clusters of galaxies or individual galaxies. Most of the polarized sources are well above our detection limit, and they are also radio galaxies that are well-resolved even at 10'', with redshifts from ∼0.2-1.9. We determined a total polarized flux for each source by integrating the 10'' polarized intensity maps, as will be done by upcoming surveys such as POSSUM. These total polarized fluxes are a factor of two higher, on average, than the peak polarized flux at 1.''6; this would increase the number counts by ∼50% at a fixed flux level. The detected sources have RMs with a characteristic rms scatter of ∼11 rad m –2 around the local Galactic value, after eliminating likely outliers. The median fractional polarization from all total intensity sources does not continue the trend of increasing at lower flux densities, as seen for stronger sources. The changes in the polarization characteristics seen at these low fluxes likely represent the increasing dominance of star-forming galaxies.

  9. Radio weak lensing shear measurement in the visibility domain - II. Source extraction

    Science.gov (United States)

    Rivi, M.; Miller, L.

    2018-05-01

    This paper extends the method introduced in Rivi et al. (2016b) to measure galaxy ellipticities in the visibility domain for radio weak lensing surveys. In that paper, we focused on the development and testing of the method for the simple case of individual galaxies located at the phase centre, and proposed to extend it to the realistic case of many sources in the field of view by isolating visibilities of each source with a faceting technique. In this second paper, we present a detailed algorithm for source extraction in the visibility domain and show its effectiveness as a function of the source number density by running simulations of SKA1-MID observations in the band 950-1150 MHz and comparing original and measured values of galaxies' ellipticities. Shear measurements from a realistic population of 104 galaxies randomly located in a field of view of 1 \\deg ^2 (i.e. the source density expected for the current radio weak lensing survey proposal with SKA1) are also performed. At SNR ≥ 10, the multiplicative bias is only a factor 1.5 worse than what found when analysing individual sources, and is still comparable to the bias values reported for similar measurement methods at optical wavelengths. The additive bias is unchanged from the case of individual sources, but it is significantly larger than typically found in optical surveys. This bias depends on the shape of the uv coverage and we suggest that a uv-plane weighting scheme to produce a more isotropic shape could reduce and control additive bias.

  10. Exploring the Variability of the Flat-spectrum Radio Source 1633+382. II. Physical Properties

    Science.gov (United States)

    Algaba, Juan-Carlos; Lee, Sang-Sung; Rani, Bindu; Kim, Dae-Won; Kino, Motoki; Hodgson, Jeffrey; Zhao, Guang-Yao; Byun, Do-Young; Gurwell, Mark; Kang, Sin-Cheol; Kim, Jae-Young; Kim, Jeong-Sook; Kim, Soon-Wook; Park, Jong-Ho; Trippe, Sascha; Wajima, Kiyoaki

    2018-06-01

    The flat-spectrum radio quasar 1633+382 (4C 38.41) showed a significant increase of its radio flux density during the period 2012 March–2015 August, which correlates with γ-ray flaring activity. Multi-frequency simultaneous very long baseline interferometry (VLBI) observations were conducted as part of the interferometric monitoring of gamma-ray bright active galactic nuclei (iMOGABA) program and supplemented with additional radio monitoring observations with the OVRO 40 m telescope, the Boston University VLBI program, and the Submillimeter Array. The epochs of the maxima for the two largest γ-ray flares coincide with the ejection of two respective new VLBI components. Analysis of the spectral energy distribution indicates a higher turnover frequency after the flaring events. The evolution of the flare in the turnover frequency-turnover flux density plane probes the adiabatic losses in agreement with the shock-in-jet model. The derived synchrotron self-absorption magnetic fields, of the order of 0.1 mG, do not seem to change dramatically during the flares, and are much weaker, by a factor 104, than the estimated equipartition magnetic fields, indicating that the source of the flare may be associated with a particle-dominated emitting region.

  11. Forecasting the Contribution of Polarized Extragalactic Radio Sources in CMB Observations

    Science.gov (United States)

    Puglisi, G.; Galluzzi, V.; Bonavera, L.; Gonzalez-Nuevo, J.; Lapi, A.; Massardi, M.; Perrotta, F.; Baccigalupi, C.; Celotti, A.; Danese, L.

    2018-05-01

    We combine the latest data sets obtained with different surveys to study the frequency dependence of polarized emission coming from extragalactic radio sources (ERS). We consider data over a very wide frequency range starting from 1.4 GHz up to 217 GHz. This range is particularly interesting since it overlaps the frequencies of the current and forthcoming cosmic microwave background (CMB) experiments. Current data suggest that at high radio frequencies (ν ≥ 20 GHz) the fractional polarization of ERS does not depend on the total flux density. Conversely, recent data sets indicate a moderate increase of polarization fraction as a function of frequency, physically motivated by the fact that Faraday depolarization is expected to be less relevant at high radio frequencies. We compute ERS number counts using updated models based on recent data, and we forecast the contribution of unresolved ERS in CMB polarization spectra. Given the expected sensitivities and the observational patch sizes of forthcoming CMB experiments, about ∼200 (up to ∼2000) polarized ERS are expected to be detected. Finally, we assess that polarized ERS can contaminate the cosmological B-mode polarization if the tensor-to-scalar ratio is <0.05 and they have to be robustly controlled to de-lens CMB B-modes at the arcminute angular scales.

  12. Metal negative ion beam extraction from a radio frequency ion source

    Energy Technology Data Exchange (ETDEWEB)

    Kanda, S.; Yamada, N.; Kasuya, T.; Romero, C. F. P.; Wada, M.

    2015-04-08

    A metal ion source of magnetron magnetic field geometry has been designed and operated with a Cu hollow target. Radio frequency power at 13.56 MHz is directly supplied to the hollow target to maintain plasma discharge and induce self-bias to the target for sputtering. The extraction of positive and negative Cu ion beams have been tested. The ion beam current ratio of Cu{sup +} to Ar{sup +} has reached up to 140% when Ar was used as the discharge support gas. Cu{sup −} ion beam was observed at 50 W RF discharge power and at a higher Ar gas pressure in the ion source. Improvement of poor RF power matching and suppression of electron current is indispensable for a stable Cu{sup −} ion beam production from the source.

  13. Metre-wavelength fine structure in 30 extragalactic radio sources with sizes of a few arcsec

    International Nuclear Information System (INIS)

    Banhatti, D.G.; Ananthakrishnan, S.; Pramesh Rao, A.

    1983-01-01

    Interplanetary scintillation (IPS) observations at 327 MHz of an unbiased sample of 30 extragalactic radio sources having overall sizes between 1 and 4 arcsec, and flux densities greater than 1 Jy at 327 MHz are reported. From VLBI observations, these sources have been reported to contain compact components of sizes < approx.= to 0.02 arcsec contributing on an average about 25 per cent of the total emission at 5 HGz. The IPS observations show that about 45 per cent of the total emission at 327 MHz arises from structures of sizes between 0.05 and 0.5 arcsec (corresponding typically to 0.5 to 5 kpc). A comparison of the VLBI and IPS results indicates that the VLBI and IPS components probably refer to the same physical features in these sources. (author)

  14. Another shock for the Bullet cluster, and the source of seed electrons for radio relics

    Science.gov (United States)

    Shimwell, Timothy W.; Markevitch, Maxim; Brown, Shea; Feretti, Luigina; Gaensler, B. M.; Johnston-Hollitt, M.; Lage, Craig; Srinivasan, Raghav

    2015-05-01

    With Australia Telescope Compact Array observations, we detect a highly elongated Mpc-scale diffuse radio source on the eastern periphery of the Bullet cluster 1E 0657-55.8, which we argue has the positional, spectral and polarimetric characteristics of a radio relic. This powerful relic (2.3 ± 0.1 × 1025 W Hz-1) consists of a bright northern bulb and a faint linear tail. The bulb emits 94 per cent of the observed radio flux and has the highest surface brightness of any known relic. Exactly coincident with the linear tail, we find a sharp X-ray surface brightness edge in the deep Chandra image of the cluster - a signature of a shock front in the hot intracluster medium (ICM), located on the opposite side of the cluster to the famous bow shock. This new example of an X-ray shock coincident with a relic further supports the hypothesis that shocks in the outer regions of clusters can form relics via diffusive shock (re-)acceleration. Intriguingly, our new relic suggests that seed electrons for reacceleration are coming from a local remnant of a radio galaxy, which we are lucky to catch before its complete disruption. If this scenario, in which a relic forms when a shock crosses a well-defined region of the ICM polluted with aged relativistic plasma - as opposed to the usual assumption that seeds are uniformly mixed in the ICM - is also the case for other relics, this may explain a number of peculiar properties of peripheral relics.

  15. FIRST Bent-Double Radio Sources: Tracers of High-Redshift Clusters

    International Nuclear Information System (INIS)

    Blanton, E. L.; Gregg, M. D.; Helfand, D. J.; Becker, R. H.; White, R. L.

    2000-01-01

    Bent-double radio sources can act as tracers for clusters of galaxies. We present imaging and spectroscopic observations of the environments surrounding 10 of these sources (most of them wide-angle tails [WATs]) selected from the VLA FIRST survey. Our results reveal a previously unknown cluster associated with eight of the radio sources with redshifts in the range 0.33< z<0.85; furthermore, we cannot rule out that the other two bent doubles may be associated with clusters at higher redshift. Richness measurements indicate that these clusters are typical of the majority of those found in the Abell catalog, with a range of Abell richness classes from 0 to 2. The line-of-sight velocity dispersions are very different from cluster to cluster, ranging from approximately 300 to 1100 km s-1. At the upper end of these intervals, we may be sampling some of the highest redshift massive clusters known. Alternatively, the large velocity dispersions measured in some of the clusters may indicate that they are merging systems with significant substructure, consistent with recent ideas concerning WAT formation (Burns et al.). (c) 2000 The American Astronomical Society

  16. Detection of anomalies in radio tomography of asteroids: Source count and forward errors

    Science.gov (United States)

    Pursiainen, S.; Kaasalainen, M.

    2014-09-01

    The purpose of this study was to advance numerical methods for radio tomography in which asteroid's internal electric permittivity distribution is to be recovered from radio frequency data gathered by an orbiter. The focus was on signal generation via multiple sources (transponders) providing one potential, or even essential, scenario to be implemented in a challenging in situ measurement environment and within tight payload limits. As a novel feature, the effects of forward errors including noise and a priori uncertainty of the forward (data) simulation were examined through a combination of the iterative alternating sequential (IAS) inverse algorithm and finite-difference time-domain (FDTD) simulation of time evolution data. Single and multiple source scenarios were compared in two-dimensional localization of permittivity anomalies. Three different anomaly strengths and four levels of total noise were tested. Results suggest, among other things, that multiple sources can be necessary to obtain appropriate results, for example, to distinguish three separate anomalies with permittivity less or equal than half of the background value, relevant in recovery of internal cavities.

  17. Comparison of three methods of restoration of cosmic radio source profiles

    International Nuclear Information System (INIS)

    Malov, I.F.; Frolov, V.A.

    1986-01-01

    Effectiveness of three methods for restoration of radio brightness distribution over the source: main solution, fitting and minimal - phase method (MPM) - was compared on the basis of data on module and phase of luminosity function (LF) of 15 cosmic radiosources. It is concluded that MPM can soccessfully compete with other known methods. Its obvious advantages in comparison with the fitting method consist in that it gives unambigous and direct restoration and a main advantage as compared with the main solution is the feasibility of restoration in the absence of data on LF phase which reduces restoration errors

  18. Acceleration of relativistic electrons in plasma reactors and non-linear spectra of cosmic radio sources

    International Nuclear Information System (INIS)

    Kaplan, S.A.; Lomadze, R.D.

    1978-01-01

    A second approximation to the theory of turbulent plasma reactors in connection with the problem of interpretation of the non-linear spectra of cosmic radio sources has been investigated by the authors (Kaplan and Lomadze, 1977; Lomadze, 1977). The present paper discusses the basic results received for a Compton reactor with plasma waves of phase velocities smaller than the velocity of light, as well as for the synchrotron reactor. The distortion of the distribution function of relativistic electrons caused by their diffusion from the reactor is also presented as an example. (Auth.)

  19. The width of jets in powerful edge-brightened extragalactic double radio sources

    International Nuclear Information System (INIS)

    Banhatti, D.G.

    1987-01-01

    The widths of primary and secondary jets are derived from a sample of 14 double hotspots in powerful extended extragalactic double radio sources. In the model employed, the primary jet extends from the core to the more compact primary hotspot and the secondary jet emerges from the primary hotspot and dissipates to form the diffuse secondary hotspot. Mean values of hotspot size/jet extent imply that the primary and secondary jets, if free, must be 2 0 and > 27 0 wide, respectively. (author)

  20. The impacts of source structure on geodetic parameters demonstrated by the radio source 3C371

    Science.gov (United States)

    Xu, Ming H.; Heinkelmann, Robert; Anderson, James M.; Mora-Diaz, Julian; Karbon, Maria; Schuh, Harald; Wang, Guang L.

    2017-07-01

    Closure quantities measured by very-long-baseline interferometry (VLBI) observations are independent of instrumental and propagation instabilities and antenna gain factors, but are sensitive to source structure. A new method is proposed to calculate a structure index based on the median values of closure quantities rather than the brightness distribution of a source. The results are comparable to structure indices based on imaging observations at other epochs and demonstrate the flexibility of deriving structure indices from exactly the same observations as used for geodetic analysis and without imaging analysis. A three-component model for the structure of source 3C371 is developed by model-fitting closure phases. It provides a real case of tracing how the structure effect identified by closure phases in the same observations as the delay observables affects the geodetic analysis, and investigating which geodetic parameters are corrupted to what extent by the structure effect. Using the resulting structure correction based on the three-component model of source 3C371, two solutions, with and without correcting the structure effect, are made. With corrections, the overall rms of this source is reduced by 1 ps, and the impacts of the structure effect introduced by this single source are up to 1.4 mm on station positions and up to 4.4 microarcseconds on Earth orientation parameters. This study is considered as a starting point for handling the source structure effect on geodetic VLBI from geodetic sessions themselves.

  1. Towards large and powerful radio frequency driven negative ion sources for fusion

    International Nuclear Information System (INIS)

    Heinemann, B; Fantz, U; Kraus, W; Schiesko, L; Wimmer, C; Wünderlich, D; Bonomo, F; Fröschle, M; Nocentini, R; Riedl, R

    2017-01-01

    The ITER neutral beam system will be equipped with radio-frequency (RF) negative ion sources, based on the IPP Garching prototype source design. Up to 100 kW at 1 MHz is coupled to the RF driver, out of which the plasma expands into the main source chamber. Compared to arc driven sources, RF sources are maintenance free and without evaporation of tungsten. The modularity of the driver concept permits to supply large source volumes. The prototype source (one driver) demonstrated operation in hydrogen and deuterium up to one hour with ITER relevant parameters. The ELISE test facility is operating with a source of half the ITER size (four drivers) in order to validate the modular source concept and to gain early operational experience at ITER relevant dimensions. A large variety of diagnostics allows improving the understanding of the relevant physics and its link to the source performance. Most of the negative ions are produced on a caesiated surface by conversion of hydrogen atoms. Cs conditioning and distribution have been optimized in order to achieve high ion currents which are stable in time. A magnetic filter field is needed to reduce the electron temperature and co-extracted electron current. The influence of different field topologies and strengths on the source performance, plasma and beam properties is being investigated. The results achieved in short pulse operation are close to or even exceed the ITER requirements with respect to the extracted ion currents. However, the extracted negative ion current for long pulse operation (up to 1 h) is limited by the increase of the co-extracted electron current, especially in deuterium operation. (paper)

  2. Probing Motion of Fast Radio Burst Sources by Timing Strongly Lensed Repeaters

    Science.gov (United States)

    Dai, Liang; Lu, Wenbin

    2017-09-01

    Given the possible repetitive nature of fast radio bursts (FRBs), their cosmological origin, and their high occurrence, detection of strongly lensed sources due to intervening galaxy lenses is possible with forthcoming radio surveys. We show that if multiple images of a repeating source are resolved with VLBI, using a method independent of lens modeling, accurate timing could reveal non-uniform motion, either physical or apparent, of the emission spot. This can probe the physical nature of FRBs and their surrounding environments, constraining scenarios including orbital motion around a stellar companion if FRBs require a compact star in a special system, and jet-medium interactions for which the location of the emission spot may randomly vary. The high timing precision possible for FRBs (˜ms) compared with the typical time delays between images in galaxy lensing (≳10 days) enables the measurement of tiny fractional changes in the delays (˜ {10}-9) and hence the detection of time-delay variations induced by relative motions between the source, the lens, and the Earth. We show that uniform cosmic peculiar velocities only cause the delay time to drift linearly, and that the effect from the Earth’s orbital motion can be accurately subtracted, thus enabling a search for non-trivial source motion. For a timing accuracy of ˜1 ms and a repetition rate (of detected bursts) of ˜0.05 per day of a single FRB source, non-uniform displacement ≳0.1-1 au of the emission spot perpendicular to the line of sight is detectable if repetitions are seen over a period of hundreds of days.

  3. Jet emission in young radio sources: A Fermi large area telescope gamma-ray view

    Energy Technology Data Exchange (ETDEWEB)

    Migliori, G.; Siemiginowska, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93107 (United States); Stawarz, Ł. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Celotti, A. [Scuola Internazionale Superiore di Studi Avanzati (SISSA), via Bonomea, 265-34136 Trieste (Italy); Begelman, M. C., E-mail: migliori@cfa.harvard.edu [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309-0440 (United States)

    2014-01-10

    We investigate the contribution of the beamed jet component to the high-energy emission in young and compact extragalactic radio sources, focusing for the first time on the γ-ray band. We derive predictions on the γ-ray luminosities associated with the relativistic jet assuming a leptonic radiative model. The high-energy emission is produced via Compton scattering by the relativistic electrons in a spherical region at the considered scales (≲10 kpc). Simulations show a wide range of γ-ray luminosities, with intensities up to ∼10{sup 46}-10{sup 48} erg s{sup –1} depending on the assumed jet parameters. We find a highly linear relation between the simulated X-ray and γ-ray luminosities that can be used to select candidates for γ-ray detection. We compare the simulated luminosity distributions in the radio, X-ray, and γ-ray regimes with observations for the largest sample of X-ray-detected young radio quasars. Our analysis of ∼4-yr Fermi Large Area Telescope (LAT) data does not yield any statistically significant detections. However, the majority of the model-predicted γ-ray fluxes for the sample are near or below the current Fermi-LAT flux threshold and compatible with the derived upper limits. Our study gives constraints on the minimum jet power (L {sub jet,} {sub kin}/L {sub disk} > 0.01) of a potential jet contribution to the X-ray emission in the most compact sources (≲ 1 kpc) and on the particle-to-magnetic field energy density ratio that are in broad agreement with equipartition assumptions.

  4. Double radio sources and the new approach to cosmical plasma physics

    International Nuclear Information System (INIS)

    Alfven, H.

    1978-01-01

    The methodology of cosmic plasma physics is discussed. It is hazardous to try to describe plasma phenomena by theories which have not been carefully tested experimentally. One present approach is to rely on laboratory measurements and in situ measurements in the magnetosphere and heliosphere, and to approach galactic phenomena by scaling up the wellknown phenomena to galactic dimensions. A summary is given of laboratory investigations of electric double layers, a phenomenon which is known to be very important in laboratory discharges. A summary is also given of the in situ measurements in the magnetosphere by which the importance of electric double layers in the Earth's surrounding is established. The scaling laws between laboratory and magnetospheric double layers are studied. The successful scaling between laboratory and magnetospheric phenomena encourages an extrapolation to heliospheric phenomena. A further extrapolation to galactic phenomena leads to a theory of double radio sources. In analogy with the Sun which, acting as a homopolar inductor, energizes the heliospheric current system, a rotating magnetized galaxy should produce a similar current system. From analogy with laboratory and magnetospheric current systems it is argued that the galactic current might produce double layers where a large energy dissipation takes place. This leads to a theory of the double radio sources which, within the necessary wide limits of uncertainty, is quantitatively reconcilable with observations. (Auth.)

  5. Radio Frequency Plasma Discharge Lamps for Use as Stable Calibration Light Sources

    Science.gov (United States)

    McAndrew, Brendan; Cooper, John; Arecchi, Angelo; McKee, Greg; Durell, Christopher

    2012-01-01

    Stable high radiance in visible and near-ultraviolet wavelengths is desirable for radiometric calibration sources. In this work, newly available electrodeless radio-frequency (RF) driven plasma light sources were combined with research grade, low-noise power supplies and coupled to an integrating sphere to produce a uniform radiance source. The stock light sources consist of a 28 VDC power supply, RF driver, and a resonant RF cavity. The RF cavity includes a small bulb with a fill gas that is ionized by the electric field and emits light. This assembly is known as the emitter. The RF driver supplies a source of RF energy to the emitter. In commercial form, embedded electronics within the RF driver perform a continual optimization routine to maximize energy transfer to the emitter. This optimization routine continually varies the light output sinusoidally by approximately 2% over a several-second period. Modifying to eliminate this optimization eliminates the sinusoidal variation but allows the output to slowly drift over time. This drift can be minimized by allowing sufficient warm-up time to achieve thermal equilibrium. It was also found that supplying the RF driver with a low-noise source of DC electrical power improves the stability of the lamp output. Finally, coupling the light into an integrating sphere reduces the effect of spatial fluctuations, and decreases noise at the output port of the sphere.

  6. Local Group dSph radio survey with ATCA (I): observations and background sources

    Science.gov (United States)

    Regis, Marco; Richter, Laura; Colafrancesco, Sergio; Massardi, Marcella; de Blok, W. J. G.; Profumo, Stefano; Orford, Nicola

    2015-04-01

    Dwarf spheroidal (dSph) galaxies are key objects in near-field cosmology, especially in connection to the study of galaxy formation and evolution at small scales. In addition, dSphs are optimal targets to investigate the nature of dark matter. However, while we begin to have deep optical photometric observations of the stellar population in these objects, little is known so far about their diffuse emission at any observing frequency, and hence on thermal and non-thermal plasma possibly residing within dSphs. In this paper, we present deep radio observations of six local dSphs performed with the Australia Telescope Compact Array (ATCA) at 16 cm wavelength. We mosaicked a region of radius of about 1 deg around three `classical' dSphs, Carina, Fornax, and Sculptor, and of about half of degree around three `ultrafaint' dSphs, BootesII, Segue2, and Hercules. The rms noise level is below 0.05 mJy for all the maps. The restoring beams full width at half-maximum ranged from 4.2 arcsec × 2.5 arcsec to 30.0 arcsec × 2.1 arcsec in the most elongated case. A catalogue including the 1392 sources detected in the six dSph fields is reported. The main properties of the background sources are discussed, with positions and fluxes of brightest objects compared with the FIRST, NVSS, and SUMSS observations of the same fields. The observed population of radio emitters in these fields is dominated by synchrotron sources. We compute the associated source number counts at 2 GHz down to fluxes of 0.25 mJy, which prove to be in agreement with AGN count models.

  7. What Are “X-shaped” Radio Sources Telling Us? II. Properties of a Sample of 87

    Science.gov (United States)

    Saripalli, Lakshmi; Roberts, David H.

    2018-01-01

    In an earlier paper, we presented Jansky Very Large Array multi-frequency, multi-array continuum imaging of a unique sample of low-axial ratio radio galaxies. In this paper, the second in the series, we examine the images to learn the phenomenology of how the off-axis emission relates to the main radio source. Inversion-symmetric offset emission appears to be bimodal and to originate from one of two strategic locations: outer ends of radio lobes (outer-deviation) or from inner ends (inner-deviation). The latter sources are almost always associated with edge-brightened sources. With S- and Z-shaped sources being a subset of outer-deviation sources, this class lends itself naturally to explanations involving black hole axis precession. Our data allow us to present a plausible model for the more enigmatic inner-deviation sources with impressive wings; as for outer-deviation sources these too require black hole axis shifts, although they also require plasma backflows into relic channels. Evolution in morphology over time relates the variety in structures in inner-deviation sources including XRGs. With features such as non-collinearities, central inner-S “spine,” corresponding lobe emission peaks, double and protruding hotspots not uncommon, black hole axis precession, drifts, or flips could be active in a significant fraction of radio sources with prominent off-axis emission. At least 4% of radio galaxies appear to undergo black hole axis rotation. Quasars offer a key signature for recognizing rotating axes. With a rich haul of sources that have likely undergone axis rotation, our work shows the usefulness of low-axial ratio sources in pursuing searches for binary supermassive black holes.

  8. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.

    1976-01-01

    Any discussion of the radio emission from stars should begin by emphasizing certain unique problems. First of all, one must clarify a semantic confusion introduced into radio astronomy in the late 1950's when most new radio sources were described as radio stars. All of these early 'radio stars' were eventually identified with other galactic and extra-galactic objects. The study of true radio stars, where the radio emission is produced in the atmosphere of a star, began only in the 1960's. Most of the work on the subject has, in fact, been carried out in only the last few years. Because the real information about radio stars is quite new, it is not surprising that major aspects of the subject are not at all understood. For this reason this paper is organized mainly around three questions: what is the available observational information; what physical processes seem to be involved; and what working hypotheses look potentially fruitful. (Auth.)

  9. Turbulence in extended synchrotron radio sources. I. Polarization of turbulent sources. II. Power-spectral analysis

    International Nuclear Information System (INIS)

    Eilek, J.A.

    1989-01-01

    Recent theories of magnetohydrodynamic turbulence are used to construct microphysical turbulence models, with emphasis on models of anisotropic turbulence. These models have been applied to the determination of the emergent polarization from a resolved uniform source. It is found that depolarization alone is not a unique measure of the turbulence, and that the turblence will also affect the total-intensity distributions. Fluctuations in the intensity image can thus be employed to measure turbulence strength. In the second part, it is demonstrated that a power-spectral analysis of the total and polarized intensity images can be used to obtain the power spectra of the synchrotron emission. 81 refs

  10. High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions

    Directory of Open Access Journals (Sweden)

    G. Thejappa

    2004-01-01

    Full Text Available Short wavelength ion sound waves (2-4kHz are detected in association with the Langmuir waves (~15-30kHz in the source regions of several local type III radio bursts. They are most probably not due to any resonant wave-wave interactions such as the electrostatic decay instability because their wavelengths are much shorter than those of Langmuir waves. The Langmuir waves occur as coherent field structures with peak intensities exceeding the Langmuir collapse thresholds. Their scale sizes are of the order of the wavelength of an ion sound wave. These Langmuir wave field characteristics indicate that the observed short wavelength ion sound waves are most probably generated during the thermalization of the burnt-out cavitons left behind by the Langmuir collapse. Moreover, the peak intensities of the observed short wavelength ion sound waves are comparable to the expected intensities of those ion sound waves radiated by the burnt-out cavitons. However, the speeds of the electron beams derived from the frequency drift of type III radio bursts are too slow to satisfy the needed adiabatic ion approximation. Therefore, some non-linear process such as the induced scattering on thermal ions most probably pumps the beam excited Langmuir waves towards the lower wavenumbers, where the adiabatic ion approximation is justified.

  11. MULTI-MESSENGER ASTRONOMY OF GRAVITATIONAL-WAVE SOURCES WITH FLEXIBLE WIDE-AREA RADIO TRANSIENT SURVEYS

    Energy Technology Data Exchange (ETDEWEB)

    Yancey, Cregg C.; Shawhan, Peter [Department of Physics, University of Maryland, College Park, MD 20742 (United States); Bear, Brandon E.; Akukwe, Bernadine; Simonetti, John H.; Tsai, Jr-Wei [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Chen, Kevin [Department of Physics, The College of New Jersey, Ewing, NJ 08628 (United States); Dowell, Jayce; Obenberger, Kenneth; Taylor, Gregory B. [Department of Physics and Astronomy, University of New Mexico, Albuquerque NM, 87131 (United States); Gough, Jonathan D. [Department of Chemistry, Lehman College, Bronx, NY 10468 (United States); Kanner, Jonah [LIGO-California Institute of Technology, Pasadena, California CA 91125 (United States); Kavic, Michael [Department of Physics, Long Island University, Brooklyn, NY 11201 (United States)

    2015-10-20

    We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ∼30 s time window and ∼200–500 deg{sup 2} sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ∼2. For some models, we also map the parameter space that may be constrained by non-detections.

  12. An Electron Bunch Compression Scheme for a Superconducting Radio Frequency Linear Accelerator Driven Light Source

    Energy Technology Data Exchange (ETDEWEB)

    C. Tennant, S.V. Benson, D. Douglas, P. Evtushenko, R.A. Legg

    2011-09-01

    We describe an electron bunch compression scheme suitable for use in a light source driven by a superconducting radio frequency (SRF) linac. The key feature is the use of a recirculating linac to perform the initial bunch compression. Phasing of the second pass beam through the linac is chosen to de-chirp the electron bunch prior to acceleration to the final energy in an SRF linac ('afterburner'). The final bunch compression is then done at maximum energy. This scheme has the potential to circumvent some of the most technically challenging aspects of current longitudinal matches; namely transporting a fully compressed, high peak current electron bunch through an extended SRF environment, the need for a RF harmonic linearizer and the need for a laser heater. Additional benefits include a substantial savings in capital and operational costs by efficiently using the available SRF gradient.

  13. A suggested classification and explanation for hotspots in some powerful radio sources

    International Nuclear Information System (INIS)

    Kronberg, P.P.; Jones, T.W.

    1982-01-01

    High resolution (1''→0.1') maps of the outer complexes of some ''well formed'' powerful radio sources suggest that we can now distinguish two physically distinct types of outer hotspots. The authors denote them as type ''A'' and ''B'' and describe them as follows: Type A hotspots, occur at the outer leading edge, and have a cusp-like, or otherwise elongated shape. This strongly suggests that their shape and energy density are determined by the ram-pressure interaction between the end of a beam or momentum flux ''pipeline'', and the ambient i.g.m. Type B hotspots generally lie off the A hotspot-galaxy/QSO axis, and are also behind the Type A hotspots. In at least some cases, they are compact and have a higher minimum energy density than the outer, Type A hotspots. (Auth.)

  14. A test of unification towards the radio source PKS1413+135

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, M.C., E-mail: up200802537@fc.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4150-007 Porto (Portugal); Julião, M.D., E-mail: meinf12013@fe.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Faculdade de Engenharia, Universidade do Porto, Rua Dr Roberto Frias, 4200-465 Porto (Portugal); Martins, C.J.A.P., E-mail: Carlos.Martins@astro.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Monteiro, A.M.R.V.L., E-mail: mmonteiro@fc.up.pt [Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4150-007 Porto (Portugal); Department of Applied Physics, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands)

    2013-07-09

    We point out that existing astrophysical measurements of combinations of the fine-structure constant α, the proton-to-electron mass ratio μ and the proton gyromagnetic ratio g{sub p} towards the radio source PKS1413+135 can be used to individually constrain each of these fundamental couplings. While the accuracy of the available measurements is not yet sufficient to test the spatial dipole scenario, our analysis serves as a proof of concept as new observational facilities will soon allow significantly more robust tests. Moreover, these measurements can also be used to obtain constraints on certain classes of unification scenarios, and we compare the constraints obtained for PKS1413+135 with those previously obtained from local atomic clock measurements.

  15. A test of unification towards the radio source PKS1413+135

    International Nuclear Information System (INIS)

    Ferreira, M.C.; Julião, M.D.; Martins, C.J.A.P.; Monteiro, A.M.R.V.L.

    2013-01-01

    We point out that existing astrophysical measurements of combinations of the fine-structure constant α, the proton-to-electron mass ratio μ and the proton gyromagnetic ratio g p towards the radio source PKS1413+135 can be used to individually constrain each of these fundamental couplings. While the accuracy of the available measurements is not yet sufficient to test the spatial dipole scenario, our analysis serves as a proof of concept as new observational facilities will soon allow significantly more robust tests. Moreover, these measurements can also be used to obtain constraints on certain classes of unification scenarios, and we compare the constraints obtained for PKS1413+135 with those previously obtained from local atomic clock measurements

  16. The optical, infrared and radio properties of extragalactic sources observed by SDSS, 2mass and first surveys

    International Nuclear Information System (INIS)

    Z. Ivezic et al.

    2002-01-01

    We positionally match sources observed by the Sloan Digital Sky Survey (SDSS), the Two Micron All Sky Survey (2MASS), and the Faint Images of the Radio Sky at Twenty-cm (FIRST) survey. Practically all 2MASS sources are matched to an SDSS source within 2 arcsec; ∼ 11% of them are optically resolved galaxies and the rest are dominated by stars. About 1/3 of FIRST sources are matched to an SDSS source within 2 arcsec; ∼ 80% of these are galaxies and the rest are dominated by quasars. Based on these results, we project that by the completion of these surveys the matched samples will include about 10 7 and 10 6 galaxies observed by both SDSS and 2MASS, and about 250,000 galaxies and 50,000 quasars observed by both SDSS and FIRST. Here we present a preliminary analysis of the optical, infrared and radio properties for the extragalactic sources from the matched samples. In particular, we find that the fraction of quasars with stellar colors missed by the SDSS spectroscopic survey is probably not larger than ∼ 10%, and that the optical colors of radio-loud quasars are ∼ 0.05 mag. redder (with 4σ significance) than the colors of radio-quiet quasars

  17. A wide low-mass binary model for the origin of axially symmetric non-thermal radio sources

    International Nuclear Information System (INIS)

    Kool, M. de; Heuvel, E.P.J. van den

    1985-01-01

    An accreting binary model has been proposed by recent workers to account for the origin of the axially symmetric non-thermal radio sources. The authors show that the only type of binary system that can produce the observed structural properties, is a relatively wide neutron star binary, in which the companion of the neutron star is a low-mass giant. Binaries of this type are expected to resemble closely the eight brightest galactic bulge X-ray sources as well as the progenitors of the two wide radio pulsar binaries. (U.K.)

  18. USING THE METHODS OF WAVELET ANALYSIS AND SINGULAR SPECTRUM ANALYSIS IN THE STUDY OF RADIO SOURCE BL LAC

    OpenAIRE

    Donskykh, G. I.; Ryabov, M. I.; Sukharev, A. I.; Aller, M.

    2014-01-01

    We investigated the monitoring data of extragalactic source BL Lac. This monitoring was held withUniversityofMichigan26-meter radio  telescope. To study flux density of extragalactic source BL Lac at frequencies of 14.5, 8 and 4.8 GHz, the wavelet analysis and singular spectrum analysis were used. Calculating the integral wavelet spectra allowed revealing long-term  components  (~7-8 years) and short-term components (~ 1-4 years) in BL Lac. Studying of VLBI radio maps (by the program Mojave) ...

  19. On an Allan variance approach to classify VLBI radio-sources on the basis of their astrometric stability

    Science.gov (United States)

    Gattano, C.; Lambert, S.; Bizouard, C.

    2017-12-01

    In the context of selecting sources defining the celestial reference frame, we compute astrometric time series of all VLBI radio-sources from observations in the International VLBI Service database. The time series are then analyzed with Allan variance in order to estimate the astrometric stability. From results, we establish a new classification that takes into account the whole multi-time scales information. The algorithm is flexible on the definition of ``stable source" through an adjustable threshold.

  20. A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Langston, Glen [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States)

    2013-04-15

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.

  1. Double hotspots and flow redirection in the lobes of powerful extragalactic radio sources

    International Nuclear Information System (INIS)

    Lonsdale, C.J.; Barthel, P.D.; Owens Valley Radio Observatory, Pasadena, CA)

    1986-01-01

    Detailed observations of two powerful extragalactic radio sources that contain a prominent double hotspot in one of their two outer lobes are presented. These double hotspots display similar characteristics in both sources, suggesting a common mechanism for their formation. Several other examples of double hotspots are found in the literature that also display many of the characteristics of those in the present sources. These characteristics cannot easily be explained by beam-jitter models, in which secondary hotspots are interpreted as previous impact sites of a beam, which has moved on to form the primary in a new location. Instead, it is proposed that these double hotspots are caused by a flow of material from the more compact to the less compact of the two. It is found that the most probable cause of the outflow is a collision of a beam from the nucleus with a massive (100-million solar mass), dense (greater than 0.1/cm) cloud in intergalactic space. The details of the deflection process itself are unclear, but a possibility is that the beam inflates a bubble of very hot plasma inside the cloud, which then escapes through a weak point in the wall of the cloud. The existence of such intergalactic clouds is considered to be a strong possibility, based on the recent literature, as well as the present hotspot outflow arguments, despite the apparently extreme values postulated for their mass and density. 45 references

  2. Lightning Radio Source Retrieval Using Advanced Lightning Direction Finder (ALDF) Networks

    Science.gov (United States)

    Koshak, William J.; Blakeslee, Richard J.; Bailey, J. C.

    1998-01-01

    A linear algebraic solution is provided for the problem of retrieving the location and time of occurrence of lightning ground strikes from an Advanced Lightning Direction Finder (ALDF) network. The ALDF network measures field strength, magnetic bearing and arrival time of lightning radio emissions. Solutions for the plane (i.e., no Earth curvature) are provided that implement all of tile measurements mentioned above. Tests of the retrieval method are provided using computer-simulated data sets. We also introduce a quadratic planar solution that is useful when only three arrival time measurements are available. The algebra of the quadratic root results are examined in detail to clarify what portions of the analysis region lead to fundamental ambiguities in source location. Complex root results are shown to be associated with the presence of measurement errors when the lightning source lies near an outer sensor baseline of the ALDF network. In the absence of measurement errors, quadratic root degeneracy (no source location ambiguity) is shown to exist exactly on the outer sensor baselines for arbitrary non-collinear network geometries. The accuracy of the quadratic planar method is tested with computer generated data sets. The results are generally better than those obtained from the three station linear planar method when bearing errors are about 2 deg. We also note some of the advantages and disadvantages of these methods over the nonlinear method of chi(sup 2) minimization employed by the National Lightning Detection Network (NLDN) and discussed in Cummins et al.(1993, 1995, 1998).

  3. Free-form analysis of the cosmological evolution of radio sources

    International Nuclear Information System (INIS)

    Robertson, J.G.

    1980-01-01

    This paper extends an iterative scheme for calculation of free-form evolution functions able to reconcile observed radio source counts with the standard General Relativistic cosmological models. It is assumed that the luminosity dependence of the evolution consists of a gradual turn-on of evolution above a certain luminosity. No particular functional form is assumed for the redshift dependence of the evolution (i.e. it is free-form). The extension concerns the use of the luminosity distribution to supply an effective luminosity function, thus overcoming a problem of consistency at the high-luminosity end of the luminosity function, where the evolution function has to be known. This method also guarantees that the correct average redshifts will be predicted where they are known observationally at high flux densities. The new iterative scheme has been applied to the source counts at 408 MHz from the Molonglo Cross telescope, using the Einstein-de Sitter cosmology and a recent determination of the luminosity distribution for sources of S 408 > 10 Jy. (author)

  4. Inverse Source Data-Processing Strategies for Radio-Frequency Localization in Indoor Environments

    Directory of Open Access Journals (Sweden)

    Gianluca Gennarelli

    2017-10-01

    Full Text Available Indoor positioning of mobile devices plays a key role in many aspects of our daily life. These include real-time people tracking and monitoring, activity recognition, emergency detection, navigation, and numerous location based services. Despite many wireless technologies and data-processing algorithms have been developed in recent years, indoor positioning is still a problem subject of intensive research. This paper deals with the active radio-frequency (RF source localization in indoor scenarios. The localization task is carried out at the physical layer thanks to receiving sensor arrays which are deployed on the border of the surveillance region to record the signal emitted by the source. The localization problem is formulated as an imaging one by taking advantage of the inverse source approach. Different measurement configurations and data-processing/fusion strategies are examined to investigate their effectiveness in terms of localization accuracy under both line-of-sight (LOS and non-line of sight (NLOS conditions. Numerical results based on full-wave synthetic data are reported to support the analysis.

  5. On the nature of emission of the star-gas-dust complex of the W1 radio source

    International Nuclear Information System (INIS)

    Udal'tsov, V.A.; Kovalenko, A.V.

    1982-01-01

    The brightness distribution of the radio source W 1 at 102 MHz has been investigated with the 187x384 m radio telescope in Pushchino. It is shown that W 1 is genetically connected with the stellar association Ceph IV as well as with the extended emission nebula GS 285 which consists of numerous nebulae, including two bright ones, Sharpless (S) 171 and NGC 7822. The radio emission of the nebula S 171 is shown to be thermal, and there is no Supernova remnant in it, in contrast with the other authors' suggestion. By two independent methods, the distance to S 171 has been evaluated to be 840 pc. The emission of NGC 7822 is mainly thermal. The extended nebula GS 285 is a thermal source, not a remnant of a Supernova that had exploded in a dense gas - dust medium, as was believed by other authors. Attention is drawn to the wrong identification by many authors of the radio source in the S 171 region with the nebula NGC 7822. It is shown that when measuring the difference of spectral indices of two sources, the calibration error may be eliminated if their calibration at given frequency is made by means of the same source [ru

  6. Studies of an inductively coupled negative hydrogen ion radio frequency source through simulations and experiments

    International Nuclear Information System (INIS)

    Bandyopadhyay, M.

    2004-01-01

    In the frame work of a development project for ITER neutral beam injection system a radio frequency (RF) driven negative hydrogen (H-/D-) ion source, (BATMAN ion source) is developed which is designed to produce several 10s of ampere of H-/D- beam current. This PhD work has been carried out to understand and optimize BATMAN ion source. The study has been done with the help of computer simulations, modeling and experiments. The complete three dimensional Monte-Carlo computer simulation codes have been developed under the scope of this PhD work. A comprehensive description about the volume production and the surface production of H- ions is presented in the thesis along with the study results obtained from the simulations, modeling and the experiments. One of the simulations is based on the volume production of H- ions, where it calculates the density profile of the vibrationally excited H2 molecules, the density profile of H- ions and the transport probability of those H- ions along the source axis towards the grid. The other simulation studies the transport of those H- ions which are produced on the surface of the plasma grid. It is expected that if there is a plasma flow in the source, the transport of plasma components (molecules and ions) would be influenced. Experimentally it is observed that there is a convective plasma flow exists in the ion source. A transverse magnetic filter field which is present near the grid inside the ion source reduces the flow velocity. Negative ions and electrons have the same sign of charge; therefore the electrons are co-extracted with the negative ions through the grid system, which is not desirable. It is observed that a magnetic field near the grid, magnetized the electrons and therefore reduce the co-extracted electron current. It is also observed experimentally that if the plasma grid is biased positively with respect to the source body, the electron density near the plasma grid is reduced and therefore the co

  7. J1649+2635: A Grand-Design Spiral with a Large Double-Lobed Radio Source

    Science.gov (United States)

    Mao, Minnie Y.; Owen, Frazer; Duffin, Ryan; Keel, Bill; Lacy, Mark; Momjian, Emmanuel; Morrison, Glenn; Mroczkowski, Tony; Neff, Susan; Norris, Ray P.; hide

    2014-01-01

    We report the discovery of a grand-design spiral galaxy associated with a double-lobed radio source. J1649+2635 (z = 0.0545) is a red spiral galaxy with a prominent bulge that it is associated with a L(1.4GHz) is approximately 10(exp24) W Hz(exp-1) double-lobed radio source that spans almost 100 kpc. J1649+2635 has a black hole mass of M(BH) is approximately 3-7 × 10(exp8) Solar mass and SFR is approximately 0.26 - 2.6 solar mass year(exp-1). The galaxy hosts a approximately 96 kpc diffuse optical halo, which is unprecedented for spiral galaxies. We find that J1649+2635 resides in an overdense environment with a mass of M(dyn) = 7.7(+7.9/-4.3) × 10(exp13) Solar mass, likely a galaxy group below the detection threshold of the ROSAT All-Sky Survey. We suggest one possible scenario for the association of double-lobed radio emission from J1649+2635 is that the source may be similar to a Seyfert galaxy, located in a denser-than-normal environment. The study of spiral galaxies that host large-scale radio emission is important because although rare in the local Universe, these sources may be more common at high-redshifts.

  8. THE STATISTICS OF RADIO ASTRONOMICAL POLARIMETRY: BRIGHT SOURCES AND HIGH TIME RESOLUTION

    International Nuclear Information System (INIS)

    Van Straten, W.

    2009-01-01

    A four-dimensional statistical description of electromagnetic radiation is developed and applied to the analysis of radio pulsar polarization. The new formalism provides an elementary statistical explanation of the modal-broadening phenomenon in single-pulse observations. It is also used to argue that the degree of polarization of giant pulses has been poorly defined in past studies. Single- and giant-pulse polarimetry typically involves sources with large flux-densities and observations with high time-resolution, factors that necessitate consideration of source-intrinsic noise and small-number statistics. Self-noise is shown to fully explain the excess polarization dispersion previously noted in single-pulse observations of bright pulsars, obviating the need for additional randomly polarized radiation. Rather, these observations are more simply interpreted as an incoherent sum of covariant, orthogonal, partially polarized modes. Based on this premise, the four-dimensional covariance matrix of the Stokes parameters may be used to derive mode-separated pulse profiles without any assumptions about the intrinsic degrees of mode polarization. Finally, utilizing the small-number statistics of the Stokes parameters, it is established that the degree of polarization of an unresolved pulse is fundamentally undefined; therefore, previous claims of highly polarized giant pulses are unsubstantiated.

  9. Radio over fiber transceiver employing phase modulation of an optical broadband source.

    Science.gov (United States)

    Grassi, Fulvio; Mora, José; Ortega, Beatriz; Capmany, José

    2010-10-11

    This paper proposes a low-cost RoF transceiver for multichannel SCM/WDM signal distribution suitable for future broadband access networks. The transceiver is based on the phase modulation of an optical broadband source centered at third transmission window. Prior to phase modulation the optical broadband source output signal is launched into a Mach-Zehnder interferometer structure, as key device enabling radio signals propagation over the optical link. Furthermore, an optical CWDM is employed to create a multichannel scenario by performing the spectral slicing of the modulated optical signal into a number of channels each one conveying the information from the central office to different base stations. The operation range is up to 20 GHz with a modulation bandwidth around of 500 MHz. Experimental results of the transmission of SCM QPSK and 64-QAM data through 20 Km of SMF exhibit good EVM results in the operative range determined by the phase-to-intensity conversion process. The proposed approach shows a great suitability for WDM networks based on RoF signal transport and also represents a cost-effective solution for passive optical networks.

  10. ON THE SOURCE OF FARADAY ROTATION IN THE JET OF THE RADIO GALAXY 3C 120

    International Nuclear Information System (INIS)

    Gomez, Jose L.; Roca-Sogorb, Mar; Agudo, Ivan; Marscher, Alan P.; Jorstad, Svetlana G.

    2011-01-01

    The source of Faraday rotation in the jet of the radio galaxy 3C 120 is analyzed through Very Long Baseline Array observations carried out between 1999 and 2007 at 86, 43, 22, 15, 12, 8, 5, 2, and 1.7 GHz. Comparison of observations from 1999 to 2001 reveals uncorrelated changes in the linear polarization of the underlying jet emission and the Faraday rotation screen: while the rotation measure (RM) remains constant between approximately 2 and 5 mas from the core, the RM-corrected electric vector position angles (EVPAs) of two superluminal components are rotated by almost 90 0 when compared to other components moving through similar jet locations. On the other hand, the innermost 2 mas experiences a significant change in RM-including a sign reversal-but without variations in the RM-corrected EVPAs. Similarly, observations in 2007 reveal a double sign reversal in RM along the jet, while the RM-corrected EVPAs remain perpendicular to the jet axis. Although the observed coherent structure and gradient of the RM along the jet support the idea that the Faraday rotation is produced by a sheath of thermal electrons that surrounds the emitting jet, the uncorrelated changes in the RM and RM-corrected EVPAs indicate that the emitting jet and the source of Faraday rotation are not closely connected physically and have different configurations for the magnetic field and/or kinematical properties. Furthermore, the existence of a region of enhanced RM whose properties remain constant over three years requires a localized source of Faraday rotation, favoring a model in which a significant fraction of the RM originates in foreground clouds.

  11. Remote sensing of a NTC radio source from a Cluster tilted spacecraft pair

    Directory of Open Access Journals (Sweden)

    P. M. E. Décréau

    2013-11-01

    Full Text Available The Cluster mission operated a "tilt campaign" during the month of May 2008. Two of the four identical Cluster spacecraft were placed at a close distance (~50 km from each other and the spin axis of one of the spacecraft pair was tilted by an angle of ~46°. This gave the opportunity, for the first time in space, to measure global characteristics of AC electric field, at the sensitivity available with long boom (88 m antennas, simultaneously from the specific configuration of the tilted pair of satellites and from the available base of three satellites placed at a large characteristic separation (~1 RE. This paper describes how global characteristics of radio waves, in this case the configuration of the electric field polarization ellipse in 3-D-space, are identified from in situ measurements of spin modulation features by the tilted pair, validating a novel experimental concept. In the event selected for analysis, non-thermal continuum (NTC waves in the 15–25 kHz frequency range are observed from the Cluster constellation placed above the polar cap. The observed intensity variations with spin angle are those of plane waves, with an electric field polarization close to circular, at an ellipticity ratio e = 0.87. We derive the source position in 3-D by two different methods. The first one uses ray path orientation (measured by the tilted pair combined with spectral signature of magnetic field magnitude at source. The second one is obtained via triangulation from the three spacecraft baseline, using estimation of directivity angles under assumption of circular polarization. The two results are not compatible, placing sources widely apart. We present a general study of the level of systematic errors due to the assumption of circular polarization, linked to the second approach, and show how this approach can lead to poor triangulation and wrong source positioning. The estimation derived from the first method places the NTC source region in the

  12. Chemistry of radio-frequency source of negative hydrogen ions; Chemia radio-frekvencneho zdroja negativnych ionov vodika

    Energy Technology Data Exchange (ETDEWEB)

    Skoviera, J.; Cernusak, I. [Univerzita Komenskeho, Prirodovedecka fakulta, Katedra fyzikalnej a teoretickej chemie, 84215 Bratislava (Slovakia)

    2013-04-16

    International Thermonuclear Experimental Reactor (ITER) is a prototype of nuclear fusion reactor Tokamak currently build in Cadarache. It will use as one of primary plasma heating components a radiofrequency driven negative ion source of deuterium. The purpose of cesium evaporated in the part of this ion source is to react with free electrons which can incidentally destroy generated hydrogen ions and are co-extracted with the hydrogen beam. Goal of this work is to investigate majority of processes which might have impact on hydrogen anion in either formative or destructive way associated with cesium. Generally the caesium dynamics is very complex in such sources and the interplay of the individual contributions and their control to establish optimum caesium coverage of the plasma grid is still an open issue. (authors)

  13. Testing for lightning as a source of radio bursts observed on the nightside of Venus

    International Nuclear Information System (INIS)

    Sonwalkar, V.S.; Carpenter, D.L.; Strangeway, R.J.

    1990-11-01

    In certain previous studies of radio burst events recorded by the Pioneer Venus Orbiting Electric Field Detector (OEFD), data were sorted for statistical purposes according to occurrence at filter band frequencies smaller than or greater than typical values of the ambient electron gyrofrequency. The expectation in making this distinction was that the lowest frequency signals, at 100 Hz, were candidates for propagation through the ionosphere to the spacecraft in the whistler mode, and that the higher frequency signals, if of subionospheric origin, would require some different ionospheric penetration mechanism. On the basis of certain assumptions about the homogeneity and horizontal stratification of the Venusian nightside ionosphere, methods were developed for case-by-case testing of the hypothesis that any particular burst event originated in subionospheric lightning. The tests, which are capable of refinement, allow prediction of the resonance cone angle, refractive index, wave dispersion, and wave polarization. The tests have been applied to data from 11 periods along 7 orbits, and are believed to represent an improved way of categorizing OEFD burst data for purposes of investigating source/propagation mechanisms. Four of the five burst events that were not found consistent with the lightning hypothesis involved receptions at multiple OEFD filter band frequencies

  14. Detection of a compact radio source near the center of a gravitational lens: quasar image or galactic core

    International Nuclear Information System (INIS)

    Gorenstein, M.V.; Shapiro, I.I.; Cohen, N.L.

    1983-01-01

    By use of a new, very sensitive interferometric system, a faint, compact radio source has been detected near the center of the galaxy that acts as the main part of a gravitational lens. This lens forms two previously discovered images of the quasar Q0957 + 561, which lies in the direction of the constellation Ursa Major. The newly detected source has a core smaller than 0.002 arc second in diameter with a flux density of 0.6 +- 0.1 millijansky at the 13-centimeter wavelength of the radio observations. This source could be the predicted third image of the transparent gravitational lens, the central core of the galaxy, or some combination of the two. It is not yet possible to choose reliably between these alternatives

  15. Trusted information sources used during and after Superstorm Sandy: TV and radio were used more often than social media.

    Science.gov (United States)

    Burger, Joanna; Gochfeld, Michael; Jeitner, Christian; Pittfield, Taryn; Donio, Mark

    2013-01-01

    Health and safety professionals and the public are interested in the best methods of providing timely information about disasters. The objective of this study was to examine information sources used for Superstorm Sandy with respect to the storm, evacuation routes, shelters, safety, and health issues. Respondents in central New Jersey and Jersey shore communities were differentially impacted by the storm. Jersey shore respondents had higher evacuation rates (47% vs. 13%), higher flood waters in homes, longer power outages (average 23 vs. 6 d), and longer periods without Internet (29 vs. 6 d). Electricity outages disrupted both sources and receivers of communication. Both groups obtained most of their information regarding safety from television, radio, friends, and Web/e-mail. Information sources on health varied by location, with central Jersey respondents using mainly TV and the Web, and Jersey shore respondents obtaining health information from the radio and TV (before the storm). For information on evacuation routes, Jersey shore respondents obtained information from many sources, while central Jersey respondents obtained it from TV. Information on mold was largely obtained from friends and the Web, since mold issues were dealt with several weeks after Sandy. The reliance on traditional sources of information (TV, radio, friends) found in this study suggests that the extreme power outages rendered Web, cell phones, and social media on cell phones less usable, and suggests the need for an integrated communication strategy with redundancies that takes into account prolonged power outages over large geographical areas.

  16. A Measurement of the Millimeter Emission and the Sunyaev-Zel'dovich Effect Associated with Low-Frequency Radio Sources

    Science.gov (United States)

    Gralla, Megan B.; Crichton, Devin; Marriage, Tobias; Mo, Wenli; Aguirre, Paula; Addison, Graeme E.; Asboth, V.; Battaglia, Nick; Bock, James; Bond, J. Richard; hide

    2014-01-01

    We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich effect associated with the halos that host them. We stack data at 148, 218 and 277 GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4 GHz. The thermal Sunyaev-Zel'dovich (SZ) effect associated with the halos that host the AGN is detected at the 5 sigma level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass halos (average M(sub 200) approximately equals 10(sup 13) solar mass h(sub 70)(exp -1) ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous halos. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyze the contribution of radio sources to the angular power spectrum of the cosmic microwave background.

  17. THE COMPACT, TIME-VARIABLE RADIO SOURCE PROJECTED INSIDE W3(OH): EVIDENCE FOR A PHOTOEVAPORATED DISK?

    Energy Technology Data Exchange (ETDEWEB)

    Dzib, Sergio A.; Rodriguez-Garza, Carolina B.; Rodriguez, Luis F.; Kurtz, Stan E.; Loinard, Laurent; Zapata, Luis A.; Lizano, Susana, E-mail: s.dzib@crya.unam.mx [Centro de Radiostronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Morelia 58089 (Mexico)

    2013-08-01

    We present new Karl G. Jansky Very Large Array (VLA) observations of the compact ({approx}0.''05), time-variable radio source projected near the center of the ultracompact H II region W3(OH). The analysis of our new data as well as of VLA archival observations confirms the variability of the source on timescales of years and for a given epoch indicates a spectral index of {alpha} = 1.3 {+-} 0.3 (S{sub {nu}}{proportional_to}{nu}{sup {alpha}}). This spectral index and the brightness temperature of the source ({approx}6500 K) suggest that we are most likely detecting partially optically thick free-free radiation. The radio source is probably associated with the ionizing star of W3(OH), but an interpretation in terms of an ionized stellar wind fails because the detected flux densities are orders of magnitude larger than expected. We discuss several scenarios and tentatively propose that the radio emission could arise in a static ionized atmosphere around a fossil photoevaporated disk.

  18. THE COMPACT, TIME-VARIABLE RADIO SOURCE PROJECTED INSIDE W3(OH): EVIDENCE FOR A PHOTOEVAPORATED DISK?

    International Nuclear Information System (INIS)

    Dzib, Sergio A.; Rodríguez-Garza, Carolina B.; Rodríguez, Luis F.; Kurtz, Stan E.; Loinard, Laurent; Zapata, Luis A.; Lizano, Susana

    2013-01-01

    We present new Karl G. Jansky Very Large Array (VLA) observations of the compact (∼0.''05), time-variable radio source projected near the center of the ultracompact H II region W3(OH). The analysis of our new data as well as of VLA archival observations confirms the variability of the source on timescales of years and for a given epoch indicates a spectral index of α = 1.3 ± 0.3 (S ν ∝ν α ). This spectral index and the brightness temperature of the source (∼6500 K) suggest that we are most likely detecting partially optically thick free-free radiation. The radio source is probably associated with the ionizing star of W3(OH), but an interpretation in terms of an ionized stellar wind fails because the detected flux densities are orders of magnitude larger than expected. We discuss several scenarios and tentatively propose that the radio emission could arise in a static ionized atmosphere around a fossil photoevaporated disk

  19. DYNAMICS INSIDE THE RADIO AND X-RAY CLUSTER CAVITIES OF CYGNUS A AND SIMILAR FRII SOURCES

    International Nuclear Information System (INIS)

    Mathews, William G.; Guo Fulai

    2012-01-01

    We describe approximate axisymmetric computations of the dynamical evolution of material inside radio lobes and X-ray cluster gas cavities in Fanaroff-Riley II (FRII) sources such as Cygnus A. All energy is delivered by a jet to the lobe/cavity via a moving hotspot where jet energy dissipates in a reverse shock. Our calculations describe the evolution of hot plasma, cosmic rays (CRs), and toroidal magnetic fields flowing from the hotspot into the cavity. Many important observational features are explained. Gas, CRs, and field flow back along the cavity surface in a 'boundary backflow' consistent with detailed FRII observations. Computed ages of backflowing CRs are consistent with observed radio-synchrotron age variations only if shear instabilities in the boundary backflow are damped and we assume this is done with viscosity of unknown origin. We compute a faint thermal jet along the symmetry axis and suggest that it is responsible for redirecting the Cygnus A nonthermal jet. Magnetic fields estimated from synchrotron self-Compton (SSC) X-radiation observed near the hotspot evolve into radio lobe fields. Computed profiles of radio-synchrotron lobe emission perpendicular to the jet reveal dramatically limb-brightened emission in excellent agreement with FRII observation, although computed lobe fields exceed those observed. Strong winds flowing from hotspots naturally create kiloparsec-sized spatial offsets between hotspot nonthermal X-ray inverse Compton (IC-CMB) emission and radio-synchrotron emission that peaks 1-2 kpc ahead where the field increases due to wind compression. In our computed version of Cygnus A, nonthermal X-ray emission increases from the hotspot (some IC-CMB, mostly SSC) toward the offset radio-synchrotron peak (mostly SSC).

  20. Motion of the sources for type II and type IV radio bursts and flare-associated interplanetary disturbances

    Science.gov (United States)

    Sakurai, K.; Chao, J. K.

    1974-01-01

    Shock waves are indirectly observed as the source of type II radio bursts, whereas magnetic bottles are identified as the source of moving metric type IV radio bursts. The difference between the expansion speeds of these waves and bottles is examined during their generation and propagation near the flare regions. It is shown that, although generated in the explosive phase of flares, the bottles behave quite differently from the waves and that the bottles are generally much slower than the waves. It has been suggested that the waves are related to flare-associated interplanetary disturbances which produce SSC geomagnetic storms. These disturbances may, therefore, be identified as interplanetary shock waves. The relationship among magnetic bottles, shock waves near the sun, and flare-associated disturbances in interplanetary space is briefly discussed.

  1. Motion of the sources for type 2 and type 4 radio bursts and flare-associated interplanetary disturbances

    Science.gov (United States)

    Sakurai, K.; Chao, J. K.

    1973-01-01

    Shock waves are indirectly observed as the source of type 2 radio brusts, whereas magnetic bottles are identified as the source of moving metric type 4 radio bursts. The difference between the expansion speeds of these waves bottles is examined during their generation and propagation near the flare regions. It is shown that, although generated in the explosive phase of flares, the behavior of the bottles is quite different from that of the waves and that the speed of the former is generally much lower. It is shown that the transit times of disturbances between the sun and the earth give information about the deceleration of shock waves to their local speeds observed near the earth's orbit. A brief discussion is given on the relationship among magnetic bottles, shock waves near the sun, and flare-associated disturbances in interplanetary space.

  2. Optimization of Pulsed Operation of the Superconducting Radio-Frequency (SRF) Cavities at the Spallation Neutron Source (SNS)

    International Nuclear Information System (INIS)

    Kim, Sang-Ho; Campisi, Isidoro E.

    2007-01-01

    In order to address the optimization in a pulsed operation, a systematic computational analysis has been made in comparison with operational experiences in superconducting radio-frequency (SRF) cavities at the Spallation Neutron Source (SNS). From the analysis it appears that the SNS SRF cavities can be operated at temperatures higher than 2.1 K, a fact resulting from both the pulsed nature of the superconducting cavities, the specific configuration of the existing cryogenic plant and the operating frequency

  3. The mystery of the "Kite" radio source in Abell 2626: Insights from new Chandra observations

    Science.gov (United States)

    Ignesti, A.; Gitti, M.; Brunetti, G.; O'Sullivan, E.; Sarazin, C.; Wong, K.

    2018-03-01

    Context. We present the results of a new Chandra study of the galaxy cluster Abell 2626. The radio emission of the cluster shows a complex system of four symmetric arcs without known correlations with the thermal X-ray emission. The mirror symmetry of the radio arcs toward the center and the presence of two optical cores in the central galaxy suggested that they may be created by pairs of precessing radio jets powered by dual active galactic nuclei (AGNs) inside the core dominant galaxy. However, previous observations failed to observe the second jetted AGN and the spectral trend due to radiative age along the radio arcs, thus challenging this interpretation. Aim. The new Chandra observation had several scientific objectives, including the search for the second AGN that would support the jet precession model. We focus here on the detailed study of the local properties of the thermal and non-thermal emission in the proximity of the radio arcs, in order to obtain further insights into their origin. Methods: We performed a standard data reduction of the Chandra dataset deriving the radial profiles of temperature, density, pressure and cooling time of the intra-cluster medium. We further analyzed the two-dimensional (2D) distribution of the gas temperature, discovering that the south-western junction of the radio arcs surrounds the cool core of the cluster. Results: We studied the X-ray surface brightness and spectral profiles across the junction, finding a cold front spatially coincident with the radio arcs. This may suggest a connection between the sloshing of the thermal gas and the nature of the radio filaments, raising new scenarios for their origin. A tantalizing possibility is that the radio arcs trace the projection of a complex surface connecting the sites where electrons are most efficiently reaccelerated by the turbulence that is generated by the gas sloshing. In this case, diffuse emission embedded by the arcs and with extremely steep spectrum should be

  4. Radio Observations of Ultra-Luminous X-Ray Sources ---Microblazars or Intermediate-Mass Black Holes?---

    Science.gov (United States)

    Körding, E.; Colbert, E.; Falcke, H.

    In recent years Ultra-Luminous X-Ray sources (ULXs) received wide attention, however, their true nature is not yet understood. Many explanations have been suggested, including intermediate-mass black holes, super-Eddington accretion flows, anisotropic emission, and relativistic beaming of microquasars. We model the logN-logS distribution of ULXs assuming that each neutron star or black hole XRB can be described by an accretion disk plus jet model, where the jet is relativistically beamed. The distribution can be either fit by intermediate-mass black holes or by stellar mass black holes with mildly relativistic jets. Even though the jet is intrinsically weaker than the accretion disk, relativistic beaming can in the latter approach lead to the high fluxes observed. To further explore the possibility of microblazars contributing to the ULX phenomenon, we have embarked on a radio-monitoring study of ULXs in nearby galaxies with the VLA. However, up to now no radio flare has been detected. Using the radio/X-ray correlation the upper limits on the radio flux can be converted into upper limits for the black hole masses of MBH ≲ 10^3 M⊙.

  5. A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

    Science.gov (United States)

    Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.

    2016-03-01

    We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population, σ _V=949_{-60}^{+80} km s-1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M200 ˜ 7-9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the Pradio-LX relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.

  6. Interplanetary scintillation observations of an unbiased sample of 90 Ooty occultation radio sources at 326.5 MHz

    International Nuclear Information System (INIS)

    Banhatti, D.G.; Ananthakrishnan, S.

    1989-01-01

    We present 327-MHz interplanetary scintillation (IPS) observations of an unbiased sample of 90 extragalactic radio sources selected from the ninth Ooty lunar occultation list. The sources are brighter than 0.75 Jy at 327 MHz and lie outside the galactic plane. We derive values, the fraction of scintillating flux density, and the equivalent Gaussian diameter for the scintillating structure. Various correlations are found between the observed parameters. In particular, the scintillating component weakens and broadens with increasing largest angular size, and stronger scintillators have more compact scintillating components. (author)

  7. Optical identifications of radio sources in the 5C 7 survey

    International Nuclear Information System (INIS)

    Perryman, M.A.C.

    1979-01-01

    An identification procedure developed for the deep radio survey 5C 6 has been refined and applied to the 5C 7 survey. Positions and finding charts are presented for candidate identifications from deep plates taken with the Palomar 48-inch Schmidt telescope. The identification statistics are in good agreement with the 5C 6 results, the accurate radio positions obtained at 1407 MHz defining a reasonably reliable and complete sample of associations with an identification rate of about 40 per cent. At 408 MHz the positional uncertainties are larger and the identifications are thus of lower reliability; the identification rate is about 20 per cent. The results are in good agreement with the assumptions that the optical identifications are coincident with the radio centroids, and that the identifications are not preferentially associated with faint clusters. (author)

  8. SELF-CONSISTENT EVOLUTION OF GAS AND COSMIC RAYS IN CYGNUS A AND SIMILAR FR II CLASSICAL DOUBLE RADIO SOURCES

    International Nuclear Information System (INIS)

    Mathews, William G.; Guo Fulai

    2010-01-01

    In Cygnus A and other classical FR II double radio sources, powerful opposing jets from the cores of halo-centered galaxies drive out into the surrounding cluster gas, forming hotspots of shocked and compressed cluster gas at the jet extremities. The moving hotspots are sandwiched between two shocks. An inner-facing shock receives momentum and cosmic rays from the jet and creates additional cosmic rays that form a radio lobe elongated along the jet axis. An outer-facing bow shock moves directly into the undisturbed group or cluster gas, creating a cocoon of shocked gas enclosing the radio lobe. We describe computations that follow the self-consistent dynamical evolution of the shocked cluster gas and the relativistic synchrotron-emitting gas inside the lobes. Relativistic and non-relativistic components exchange momentum by interacting with small magnetic fields having dynamically negligible energy densities. The evolution of Cygnus A is governed almost entirely by cosmic ray energy flowing from the hotspots. Mass flowing into hotspots from the jets is assumed to be small, greatly reducing the mass of gas flowing back along the jet, common in previous calculations, that would disrupt the spatial segregation of synchrotron-loss ages observed inside FR II radio lobes. We compute the evolution of the cocoon when the velocity and cosmic ray luminosity of the hotspots are constant and when they vary with time. If cosmic rays mix with cluster gas in hotspots before flowing into the radio lobe, the thermal gas is heated to mildly relativistic temperatures, producing an unobserved pressure inside the lobe.

  9. Study feature of variability extragalactic radio sources 3C 446 and BL Lac in the centimeter wavelength range

    International Nuclear Information System (INIS)

    Sukharev, A.L.

    2015-01-01

    This work presents the results of the analysis of long-term monitoring (over 40 years) changes in radio fluxes of the two extragalactic sources - 3C 446, and BL Lac. Observations at frequencies of 14.5, 8, 4.8 GHz were obtained in the Michigan Radio Astronomy Observatory (UMRAO). With using Fourier filtering were selected 0- C (short-period), and the trend component of flux variations that were analyzed separately with using the wavelet-analysis method. Each of these components is associated with certain physical processes in the 'core-accretion disk-jet' system. Were constructed time-frequency wavelet-spectra showing the changes of the frequency composition of the investigated data over time. For the trend component values of the main periods of -4-9 years (3C 446) and -8 years (BL Lac), for 0- C component -0.8-3 years (3C 446) and -0.6-4 years (BL Lac) and they appear in the temporal and structural changes of the jet. On the basis of calculating the global wavelet-spectra in the frequency range identified main phases activity of radio sources. Obtained comparison between the dynamics of jets (Mojave VLBI images), and change the frequency spectral structure of the studied data. With bandpass wavelet filtering, flux components corresponding to the main periods in the spectra, were identified and also found the delay between the observation frequencies in spectral bands of these periods

  10. GYRO-ORBIT SIZE, BRIGHTNESS TEMPERATURE LIMIT, AND IMPLAUSIBILITY OF COHERENT EMISSION BY BUNCHING IN SYNCHROTRON RADIO SOURCES

    International Nuclear Information System (INIS)

    Singal, Ashok K.

    2012-01-01

    We show that an upper limit on the maximum brightness temperature for a self-absorbed incoherent synchrotron radio source is obtained from the size of its gyro orbits, which in turn must lie well within the confines of the total source extent. These temperature limits are obtained without recourse to inverse Compton effects or the condition of equipartition of energy between magnetic fields and relativistic particles. For radio variables, the intra-day variability implies brightness temperatures ∼10 19 K in the comoving rest frame of the source. This, if interpreted purely due to an incoherent synchrotron emission, would imply gyroradii >10 28 cm, the size of the universe, while from the causality arguments the inferred maximum size of the source in such a case is ∼ 15 cm. Such high brightness temperatures are sometimes modeled in the literature as some coherent emission process where bunches of non-thermal particles are somehow formed that radiate in phase. We show that, unlike in the case of curvature radiation models proposed in pulsars, in the synchrotron radiation mechanism the oppositely charged particles would contribute together to the coherent phenomenon without the need to form separate bunches of the opposite charges. At the same time we show that bunches would disperse over dimensions larger than a wavelength in time shorter than the gyro orbital period (∼< 0.1 s). Therefore, a coherent emission by bunches cannot be a plausible explanation of the high brightness temperatures inferred in extragalactic radio sources showing variability over a few hours or longer.

  11. Fornax A, Centaurus A other radio galaxies as sources of ultra-high energy cosmic rays

    Science.gov (United States)

    Matthews, J. H.; Bell, A. R.; Blundell, K. M.; Araudo, A. T.

    2018-06-01

    The origin of ultra-high energy cosmic rays (UHECRs) is still unknown. It has recently been proposed that UHECR anisotropies can be attributed to starburst galaxies or active galactic nuclei. We suggest that the latter is more likely and that giant-lobed radio galaxies such as Centaurus A and Fornax A can explain the data.

  12. TELEVISION AND RADIO IN ADULT EDUCATION, NUMBER 1. CURRENT INFORMATION SOURCES.

    Science.gov (United States)

    Syracuse Univ., NY. ERIC Clearinghouse on Adult Education.

    AN ANNOTATED BIBLIOGRAPHY CONTAINS 32 INDEXED ITEMS, MOSTLY WITH ABSTRACTS, ON ASPECTS OF EDUCATIONAL AND INSTRUCTIONAL RADIO AND TELEVISION, PARTICULARLY VIEWING HABITS, MOTIVATION, PUBLIC TELEVISION, MEDIA TECHNOLOGY (INCLUDING COMMUNICATION SATELLITES), INFORMATION DISSEMINATION AND PATTERNS OF INFORMATION SEEKING, THE USE OF CORRESPONDENCE…

  13. MINIFILAMENT ERUPTION AS THE SOURCE OF A BLOWOUT JET, C-CLASS FLARE, AND TYPE-III RADIO BURST

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Junchao; Jiang, Yunchun; Yang, Jiayan; Li, Haidong; Xu, Zhe, E-mail: hjcsolar@ynao.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, 396 Yangfangwang, Guandu District, Kunming, 650216 (China); Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012 (China)

    2017-01-20

    We report a strong minifilament eruption associated with Geostationary Operational Environmental Satellite C1.6 flare and WIND type-III radio burst. The minifilament, which lies at the periphery of active region 12259, is detected by H α images from the New Vacuum Solar Telescope. The minifilament undergoes a partial and then a full eruption. Simultaneously, two co-spatial jets are successively observed in extreme ultraviolet images from the Solar Dynamic Observatory . The first jet exhibits a typical fan-spine geometry, suggesting that the co-spatial minifilament is possibly embedded in magnetic fields with a fan-spine structure. However, the second jet displays blowout morphology when the entire minifilament erupts upward, leaving behind a hard X-ray emission source in the base. Differential emission measure analyses show that the eruptive region is heated up to about 4 MK during the fan-spine jet, while up to about 7 MK during the blowout jet. In particular, the blowout jet is accompanied by an interplanetary type-III radio burst observed by WIND /WAVES in the frequency range from above 10 to 0.1 MHz. Hence, the minifilament eruption is correlated with the interplanetary type-III radio burst for the first time. These results not only suggest that coronal jets can result from magnetic reconnection initiated by erupting minifilaments with open fields, but also shed light on the potential influence of minifilament eruption on interplanetary space.

  14. Study of electron current extraction from a radio frequency plasma cathode designed as a neutralizer for ion source applications

    Energy Technology Data Exchange (ETDEWEB)

    Jahanbakhsh, Sina, E-mail: sinajahanbakhsh@gmail.com; Satir, Mert; Celik, Murat [Department of Mechanical Engineering, Bogazici University, Istanbul 34342 (Turkey)

    2016-02-15

    Plasma cathodes are insert free devices that are developed to be employed as electron sources in electric propulsion and ion source applications as practical alternatives to more commonly used hollow cathodes. Inductively coupled plasma cathodes, or Radio Frequency (RF) plasma cathodes, are introduced in recent years. Because of its compact geometry, and simple and efficient plasma generation, RF plasma source is considered to be suitable for plasma cathode applications. In this study, numerous RF plasma cathodes have been designed and manufactured. Experimental measurements have been conducted to study the effects of geometric and operational parameters. Experimental results of this study show that the plasma generation and electron extraction characteristics of the RF plasma cathode device strongly depend on the geometric parameters such as chamber diameter, chamber length, orifice diameter, orifice length, as well as the operational parameters such as RF power and gas mass flow rate.

  15. Medicina array demonstrator: calibration and radiation pattern characterization using a UAV-mounted radio-frequency source

    Science.gov (United States)

    Pupillo, G.; Naldi, G.; Bianchi, G.; Mattana, A.; Monari, J.; Perini, F.; Poloni, M.; Schiaffino, M.; Bolli, P.; Lingua, A.; Aicardi, I.; Bendea, H.; Maschio, P.; Piras, M.; Virone, G.; Paonessa, F.; Farooqui, Z.; Tibaldi, A.; Addamo, G.; Peverini, O. A.; Tascone, R.; Wijnholds, S. J.

    2015-06-01

    One of the most challenging aspects of the new-generation Low-Frequency Aperture Array (LFAA) radio telescopes is instrument calibration. The operational LOw-Frequency ARray (LOFAR) instrument and the future LFAA element of the Square Kilometre Array (SKA) require advanced calibration techniques to reach the expected outstanding performance. In this framework, a small array, called Medicina Array Demonstrator (MAD), has been designed and installed in Italy to provide a test bench for antenna characterization and calibration techniques based on a flying artificial test source. A radio-frequency tone is transmitted through a dipole antenna mounted on a micro Unmanned Aerial Vehicle (UAV) (hexacopter) and received by each element of the array. A modern digital FPGA-based back-end is responsible for both data-acquisition and data-reduction. A simple amplitude and phase equalization algorithm is exploited for array calibration owing to the high stability and accuracy of the developed artificial test source. Both the measured embedded element patterns and calibrated array patterns are found to be in good agreement with the simulated data. The successful measurement campaign has demonstrated that a UAV-mounted test source provides a means to accurately validate and calibrate the full-polarized response of an antenna/array in operating conditions, including consequently effects like mutual coupling between the array elements and contribution of the environment to the antenna patterns. A similar system can therefore find a future application in the SKA-LFAA context.

  16. Millimeter wave technology IV and radio frequency power sources; Proceedings of the Meeting, Orlando, FL, May 21, 22, 1987

    International Nuclear Information System (INIS)

    Wiltse, J.C.; Coleman, J.T.

    1987-01-01

    The present conference on mm-wave technology and radio-frequency power sources discusses topics in the fields of vacuum devices, mm-wave antennas and transmission lines, mm-wave systems and subsystems, and mm-wave techniques and components. Attention is given to recent experiments with planar orotrons, a high peak power X-band gyroklystron for linear supercolliders, cathode-driven crossed-field amplifiers, multi-MW quasi-optical gyrotrons, the radiation coupling of interinjection-locked oscillators, air-to-air mm-wave communications, mm-wave active and passive sensors for terrain mapping, and mm-wave components for electronically controllable antennas

  17. Kinematics and physical conditions of H I in nearby radio sources. The last survey of the old Westerbork Synthesis Radio Telescope

    NARCIS (Netherlands)

    Maccagni, F. M.; Morganti, R.; Oosterloo, T. A.; Geréb, K.; Maddox, N.

    2017-01-01

    We present an analysis of the properties of neutral hydrogen (H I) in 248 nearby (0.02 radio galaxies with S1.4 GHz > 30 mJy and for which optical spectroscopy is available. The observations were carried out with the Westerbork Synthesis Radio Telescope as the last large project before the

  18. Evaluation of power transfer efficiency for a high power inductively coupled radio-frequency hydrogen ion source

    Science.gov (United States)

    Jain, P.; Recchia, M.; Cavenago, M.; Fantz, U.; Gaio, E.; Kraus, W.; Maistrello, A.; Veltri, P.

    2018-04-01

    Neutral beam injection (NBI) for plasma heating and current drive is necessary for International Thermonuclear Experimental reactor (ITER) tokamak. Due to its various advantages, a radio frequency (RF) driven plasma source type was selected as a reference ion source for the ITER heating NBI. The ITER relevant RF negative ion sources are inductively coupled (IC) devices whose operational working frequency has been chosen to be 1 MHz and are characterized by high RF power density (˜9.4 W cm-3) and low operational pressure (around 0.3 Pa). The RF field is produced by a coil in a cylindrical chamber leading to a plasma generation followed by its expansion inside the chamber. This paper recalls different concepts based on which a methodology is developed to evaluate the efficiency of the RF power transfer to hydrogen plasma. This efficiency is then analyzed as a function of the working frequency and in dependence of other operating source and plasma parameters. The study is applied to a high power IC RF hydrogen ion source which is similar to one simplified driver of the ELISE source (half the size of the ITER NBI source).

  19. UNVEILING THE NATURE OF THE UNIDENTIFIED GAMMA-RAY SOURCES. III. GAMMA-RAY BLAZAR-LIKE COUNTERPARTS AT LOW RADIO FREQUENCIES

    Energy Technology Data Exchange (ETDEWEB)

    Massaro, F.; Funk, S. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D' Abrusco, R.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Giroletti, M. [INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Masetti, N. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, I-40129 Bologna (Italy); Tosti, G. [Dipartimento di Fisica, Universita degli Studi di Perugia, I-06123 Perugia (Italy); Nori, M. [Department of Physics and Astronomy, University of Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy)

    2013-07-01

    About one-third of the {gamma}-ray sources listed in the second Fermi Large Area Telescope catalog (2FGL) have no firmly established counterpart at lower energies and so are classified as unidentified gamma-ray sources (UGSs). Here, we propose a new approach to find candidate counterparts for the UGSs based on the 325 MHz radio survey performed with the Westerbork Synthesis Radio Telescope in the northern hemisphere. First, we investigate the low-frequency radio properties of blazars, the largest known population of {gamma}-ray sources; then we search for sources with similar radio properties combining the information derived from the Westerbork Northern Sky Survey (WENSS) with those of the NRAO Very Large Array Sky Survey. We present a list of candidate counterparts for 32 UGSs with at least one counterpart in the WENSS. We also performed an extensive research in the literature to look for infrared and optical counterparts of the {gamma}-ray blazar candidates selected using the low-frequency radio observations to confirm their nature. On the basis of our multifrequency research, we identify 23 new {gamma}-ray blazar candidates out of the 32 UGSs investigated. Comparison with previous results on the UGSs is also presented. Finally, we speculate on the advantages of using low-frequency radio observations to associate UGSs and to search for {gamma}-ray pulsar candidates.

  20. Brightness Temperature of Radio Zebras and Wave Energy Densities in Their Sources

    Czech Academy of Sciences Publication Activity Database

    Yasnov, L. V.; Benáček, J.; Karlický, Marian

    2017-01-01

    Roč. 292, č. 11 (2017), 163/1-163/12 ISSN 0038-0938 R&D Projects: GA ČR(CZ) GA16-13277S; GA ČR(CZ) GA17-16447S Grant - others:GA MŠk,CERIT-SC(CZ) LM2015085; GA MŠk(CZ) LM2015042 Institutional support: RVO:67985815 Keywords : Sun corona * Su flares * radio radiation Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 2.682, year: 2016

  1. The VLT/MUSE view of the central galaxy in Abell 2052. Ionized gas swept by the expanding radio source

    Science.gov (United States)

    Balmaverde, Barbara; Capetti, Alessandro; Marconi, Alessandro; Venturi, Giacomo

    2018-04-01

    We report observations of the radio galaxy 3C 317 (at z = 0.0345) located at the center of the Abell cluster A2052, obtained with the VLT/MUSE integral field spectrograph. The Chandra images of this cluster show cavities in the X-ray emitting gas, which were produced by the expansion of the radio lobes inflated by the active galactic nucleus (AGN). Our exquisite MUSE data show with unprecedented detail the complex network of line emitting filaments enshrouding the northern X-ray cavity. We do not detect any emission lines from the southern cavity, with a luminosity asymmetry between the two regions higher than 75. The emission lines produced by the warm phase of the interstellar medium (WIM) enable us to obtain unique information on the properties of the emitting gas. We find dense gas (up to 270 cm-3) that makes up part of a global quasi spherical outflow that is driven by the radio source, and obtain a direct estimate of the expansion velocity of the cavities (265 km s-1). The emission lines diagnostic rules out ionization from the AGN or from star-forming regions, suggesting instead ionization from slow shocks or from cosmic rays. The striking asymmetric line emission observed between the two cavities contrasts with the less pronounced differences between the north and south sides in the hot gas; this represents a significant new ingredient for our understanding of the process of the exchange of energy between the relativistic plasma and the external medium. We conclude that the expanding radio lobes displace the hot tenuous phase of the interstellar medium (ISM), but also impact the colder and denser ISM phases. These results show the effects of the AGN on its host and the importance of radio mode feedback. The reduced datacube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A19

  2. A revisit to self-excited push pull vacuum tube radio frequency oscillator for ion sources and power measurements

    International Nuclear Information System (INIS)

    Hlondo, L. R.; Lalremruata, B.; Punte, L. R. M.; Rebecca, L.; Lalnunthari, J.; Thanga, H. H.

    2016-01-01

    Self-excited push-pull vacuum tube oscillator is one of the most commonly used oscillators in radio frequency (RF)-ion plasma sources for generation of ions using radio frequency. However, in spite of its fundamental role in the process of plasma formation, the working and operational characteristics are the most frequently skip part in the descriptions of RF ion sources in literatures. A more detailed treatment is given in the present work on the RF oscillator alone using twin beam power tetrodes 829B and GI30. The circuit operates at 102 MHz, and the oscillation conditions, stability in frequency, and RF output power are studied and analyzed. A modified form of photometric method and RF peak voltage detection method are employed to study the variation of the oscillator output power with plate voltage. The power curves obtained from these measurements are quadratic in nature and increase with increase in plate voltage. However, the RF output power as measured by photometric methods is always less than the value calculated from peak voltage measurements. This difference is due to the fact that the filament coil of the ordinary light bulb used as load/detector in photometric method is not a perfect inductor. The effect of inductive reactance on power transfer to load was further investigated and a technique is developed to estimate the amount of power correction needed in the photometric measurement result.

  3. Numerical simulation of atmospheric-pressure helium discharge driven by combined radio frequency and trapezoidal pulse sources

    International Nuclear Information System (INIS)

    Wang Qi; Sun Jizhong; Zhang Jianhong; Ding Zhenfeng; Wang Dezhen

    2010-01-01

    Atmospheric-pressure capacitive discharges driven by combined radio frequency (rf) and trapezoidal pulse sources are investigated using a one-dimensional self-consistent fluid model. The results show that the plasma intensity in the rf discharge can be enhanced drastically when a low duty ratio short pulse source is additionally applied. The mechanism for the increase in the plasma density can be attributed to a strong localized electric field induced by the applied short pulse; the strong electric field generates a great number of high energy electrons and chemically active particles, which subsequently generate more electrons and ions. The rf capacitive discharges with the aid of externally applied short pulses can achieve a high plasma density with better power efficiency.

  4. Radio source counts: comments on their convergence and assessment of the contribution to fluctuations of the microwave background

    International Nuclear Information System (INIS)

    Danese, L.; De Zotti, G.; Mandolesi, N.

    1982-01-01

    We point out that statistically estimated high frequency counts at milli-Jansky levels exhibit a slower convergence than expected on the basis of extrapolations of counts at higher flux densities and at longer wavelengths. This seems to demand a substantial cosmological evolution for at least a sub-population of flat-spectrum sources different from QSO's, a fact that might have important implications also in connection with the problem of the origin of the X-ray background. We also compute the discrete source contributions to small scale fluctuations in the Rayleigh-Jeans region of the cosmic microwave background and we show that they set a serious limit to the searches for truly primordial anisotropies using conventional radio-astronomical techniques

  5. Planck intermediate results. VII. Statistical properties of infrared and radio extragalactic sources from the Planck Early Release Compact Source Catalogue at frequencies between 100 and 857 GHz

    Science.gov (United States)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Argüeso, F.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bethermin, M.; Bhatia, R.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Burigana, C.; Cabella, P.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, L.-Y.; Christensen, P. R.; Clements, D. L.; Colafrancesco, S.; Colombi, S.; Colombo, L. P. L.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Fosalba, P.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Jaffe, T. R.; Jaffe, A. H.; Jagemann, T.; Jones, W. C.; Juvela, M.; Keihänen, E.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurinsky, N.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lawrence, C. R.; Leonardi, R.; Lilje, P. B.; López-Caniego, M.; Macías-Pérez, J. F.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Mitra, S.; Miville-Deschènes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sajina, A.; Sandri, M.; Savini, G.; Scott, D.; Smoot, G. F.; Starck, J.-L.; Sudiwala, R.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Türler, M.; Valenziano, L.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, M.; Yvon, D.; Zacchei, A.; Zonca, A.

    2013-02-01

    We make use of the Planck all-sky survey to derive number counts and spectral indices of extragalactic sources - infrared and radio sources - from the Planck Early Release Compact Source Catalogue (ERCSC) at 100 to 857 GHz (3 mm to 350 μm). Three zones (deep, medium and shallow) of approximately homogeneous coverage are used to permit a clean and controlled correction for incompleteness, which was explicitly not done for the ERCSC, as it was aimed at providing lists of sources to be followed up. Our sample, prior to the 80% completeness cut, contains between 217 sources at 100 GHz and 1058 sources at 857 GHz over about 12 800 to 16 550 deg2 (31 to 40% of the sky). After the 80% completeness cut, between 122 and 452 and sources remain, with flux densities above 0.3 and 1.9 Jy at 100 and 857 GHz. The sample so defined can be used for statistical analysis. Using the multi-frequency coverage of the Planck High Frequency Instrument, all the sources have been classified as either dust-dominated (infrared galaxies) or synchrotron-dominated (radio galaxies) on the basis of their spectral energy distributions (SED). Our sample is thus complete, flux-limited and color-selected to differentiate between the two populations. We find an approximately equal number of synchrotron and dusty sources between 217 and 353 GHz; at 353 GHz or higher (or 217 GHz and lower) frequencies, the number is dominated by dusty (synchrotron) sources, as expected. For most of the sources, the spectral indices are also derived. We provide for the first time counts of bright sources from 353 to 857 GHz and the contributions from dusty and synchrotron sources at all HFI frequencies in the key spectral range where these spectra are crossing. The observed counts are in the Euclidean regime. The number counts are compared to previously published data (from earlier Planck results, Herschel, BLAST, SCUBA, LABOCA, SPT, and ACT) and models taking into account both radio or infrared galaxies, and covering a

  6. The 100 strongest radio point sources in the field of the Large Magellanic Cloud at 1.4 GHz

    Directory of Open Access Journals (Sweden)

    Payne J.L.

    2009-01-01

    Full Text Available We present the 100 strongest 1.4 GHz point sources from a new mosaic image in the direction of the Large Magellanic Cloud (LMC. The observations making up the mosaic were made using Australia Telescope Compact Array (ATCA over a ten year period and were combined with Parkes single dish data at 1.4 GHz to complete the image for short spacing. An initial list of co-identifications within 1000 at 0.843, 4.8 and 8.6 GHz consisted of 2682 sources. Elimination of extended objects and artifact noise allowed the creation of a refined list containing 1988 point sources. Most of these are presumed to be background objects seen through the LMC; a small portion may represent compact H ii regions, young SNRs and radio planetary nebulae. For the 1988 point sources we find a preliminary average spectral index (α of -0.53 and present a 1.4 GHz image showing source location in the direction of the LMC.

  7. The 100 Strongest Radio Point Sources in the Field of the Large Magellanic Cloud at 1.4 GHz

    Directory of Open Access Journals (Sweden)

    Payne, J. L.

    2009-06-01

    Full Text Available We present the 100 strongest 1.4~GHz point sources from a new mosaicimage in the direction of the Large Magellanic Cloud (LMC. The observationsmaking up the mosaic were made using Australia Telescope Compact Array (ATCAover a ten year period and were combined with Parkes single dish data at 1.4 GHz to complete the image for short spacing. An initial list of co-identifications within 10arcsec at 0.843, 4.8 and 8.6 GHz consisted of 2682 sources. Elimination of extended objects and artifact noise allowed the creation of a refined list containing 1988 point sources. Most of these are presumed to be background objects seen through the LMC; a small portion may represent compact HII regions, young SNRs and radio planetary nebulae. For the 1988 point sources we find a preliminary average spectral index ($alpha$ of -0.53 and present a 1.4 GHz image showing source locationin the direction of the LMC.

  8. Simplified radio-over-fiber transport systems with a low-cost multiband light source.

    Science.gov (United States)

    Chang, Ching-Hung; Peng, Peng-Chun; Lu, Hai-Han; Shih, Chine-Liang; Chen, Hwan-Wen

    2010-12-01

    In this Letter, low-cost radio-over-fiber (ROF) transport systems are proposed and experimentally demonstrated. By utilizing a laser diode (LD) and a local oscillator (LO) to generate coherent multiband optical carriers, as well as a self-composed wavelength selector to separate every two carriers for different ROF transport systems, no any other dedicated LD or electrical frequency upconverting circuit/process is needed in the central station (CS). Compared with current ROF systems, the required numbers of LDs, LOs, and mixers in a CS are significantly reduced. Reducing the number of components not only can simplify the network structure but can also reduce the volume and complexity of the relative logistics. To demonstrate the practice of the proposed ROF transport systems, clear eye diagrams and error-free transmission performance are experimentally presented.

  9. Radio observations of a galactic high energy gamma-ray source

    Energy Technology Data Exchange (ETDEWEB)

    Giacani, E.; Rovero, A.C. [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina)

    2001-10-01

    PSR B1706-44 is one of the very few galactic pulsars that has been discovered at TeV energies. PSR B1706-44 has been also detected in the X-ray domain. It has been suggested that the high energy radiation could be due to inverse Compton radiation from a pulsar wind nebula (PWN). It was reported on VLA high-resolution observations of a region around the pulsar PSR B1706-44 at 1.4, 4.8 and 8.4 GHz. The pulsar appears embedded in a synchrotron nebula. It was proposed that this synchrotron nebula is the radio counterpart of the high energy emission powered by the spin-down energy of the pulsar.

  10. The Green Bank Third (GB3) survey of extragalactic radio sources at 1400 MHz

    International Nuclear Information System (INIS)

    Rys, S.; Machalski, J.

    1987-01-01

    The NRAO 91-m radio telescope in Green Bank, West Virginia was used to make a 1400-MHz sky survey covering an area of 0.0988 sr at declinations 70 deg ≤ δ 1950 < 76.8 deg with 10.1 x 10.5 arcmin resolution. This survey ends the series of smaller than 1-sr surveys made at 1400 MHz with that telescope and four-feed radiometer. A catalogue of 502 radiosources is presented, statistically complete to 112 mJy, which is about five times the rms noise and extragalactic confusion. The observations and data reduction are briefly summarized; the position and flux density errors are discussed. 13 refs., 2 tabs. (author)

  11. Relations between turbulent regions of interplanetary magnetic field and Jovian decametric radio wave emissions from the main source

    International Nuclear Information System (INIS)

    Oya, H.; Morioka, A.

    1981-01-01

    Jovian decametric radio wave emissions that were observed at Goddard Space Flight Center, U.S.A. for a period from 1 October to 31 December, 1974 and data obtained at Mt. Zao observatory, Tohoku University, Japan, for a period from 14 July to 6 December, 1975 have been used to investigate the relationship of the occurrence of the Jovian decametric radio waves (JDW), from the main source, to the geomagnetic disturbance index, ΣKAPPA sub(rho). The dynamic cross-correlation between JDW and ΣKAPPAsubrho indicates an enhanced correlation for certain values of delay time. The delay time is consistent with predicted values based on a model of rotating turbulent regions in interplanetary space associated with two sector boundaries of the interplanetary magnetic field, i.e. the rotating sector boundaries of the interplanetary magnetic field first encounter the Earth's magnetosphere producing the geomagnetic field disturbances, and after a certain period, they encounter the Jovian magnetosphere. There are also cases where the order of the encounter is opposite, i.e. the sector boundaries encounter first Jovian magnetosphere and encounter the Earth's magnetosphere after a certain period. (author)

  12. The changing source of X-ray reflection in the radio-intermediate Seyfert 1 galaxy III Zw 2

    Science.gov (United States)

    Gonzalez, A. G.; Waddell, S. G. H.; Gallo, L. C.

    2018-03-01

    We report on X-ray observations of the radio-intermediate, X-ray bright Seyfert 1 galaxy, III Zw 2, obtained with XMM-Newton, Suzaku, and Swift over the past 17 yr. The source brightness varies significantly over yearly time-scales, but more modestly over periods of days. Pointed observations with XMM-Newton in 2000 and Suzaku in 2011 show spectral differences despite comparable X-ray fluxes. The Suzaku spectra are consistent with a power-law continuum and a narrow Gaussian emission feature at ˜6.4 keV, whereas the earlier XMM-Newton spectrum requires a broader Gaussian profile and soft-excess below ˜2 keV. A potential interpretation is that the primary power-law emission, perhaps from a jet base, preferentially illuminates the inner accretion disc in 2000, but the distant torus in 2011. The interpretation could be consistent with the hypothesized precessing radio jet in III Zw 2 that may have originated from disc instabilities due to an ongoing merging event.

  13. Chapter 27: Deja vu All Over Again: Using NVO Tools to Re-Investigate a Complete Sample of Texas Radio Survey Sources

    Science.gov (United States)

    Lucas, Ray A.; Rohde, David; Tamura, Takayuki; van Dyne, Jeffrey

    At the first NVO Summer School in September 2004, a complete sample of Texas Radio Survey sources, first derived in 1989 and subsequently observed with the VLA in A-array snapshot mode in 1990, was revisited. The original investigators had never had the occasion to reduce the A-array 5-minute snapshot data, nor to do any other significant follow-up, though the sample still seemed a possibly useful but relatively small study of radio galaxies, AGN, quasars, extragalactic sources, and galaxy clusters, etc. At the time of the original sample definition in late 1989, the best optical material available for the region was the SRC-J plate from the UK Schmidt Telescope in Australia. In much more recent times, the Sloan Digital Sky Survey has included the region in its DR2 data release, so good multicolor optical imaging in a number of standard bandpasses has finally become available. These data, along with other material in the radio, infrared, and (where available) were used to get a better preliminary idea of the nature of the objects in the 1989 sample. We also investigated one of the original questions: whether these radio sources with steeper (or at least non-flat) radio spectra were associated with galaxy clusters, and in some cases higher-redshift galaxy clusters and AGN. A rudimentary web service was created which allowed the user to perform simple cone searches and SIAP image extractions of specified field sizes for multiwavelength data across the electromagnetic spectrum, and a prototype web page was set up which would display the resulting images in wavelength order across the page for sources in the sample. Finally, as an additional investigation, using radio and X-ray IDs as a proxy for AGN which might be associated with large, central cluster galaxies, positional matches of radio and X-ray sources from two much larger catalogs were done using the tool TOPCAT in order to search for the degree of correlation between ID positions, radio luminosity, and cluster

  14. The B3-VLA CSS sample. VIII. New optical identifications from the Sloan Digital Sky Survey The ultraviolet-optical spectral energy distribution of the young radio sources

    Science.gov (United States)

    Fanti, C.; Fanti, R.; Zanichelli, A.; Dallacasa, D.; Stanghellini, C.

    2011-04-01

    Context. Compact steep-spectrum radio sources and giga-hertz peaked spectrum radio sources (CSS/GPS) are generally considered to be mostly young radio sources. In recent years we studied at many wavelengths a sample of these objects selected from the B3-VLA catalog: the B3-VLA CSS sample. Only ≈60% of the sources were optically identified. Aims: We aim to increase the number of optical identifications and study the properties of the host galaxies of young radio sources. Methods: We cross-correlated the CSS B3-VLA sample with the Sloan Digital Sky Survey (SDSS), DR7, and complemented the SDSS photometry with available GALEX (DR 4/5 and 6) and near-IR data from UKIRT and 2MASS. Results: We obtained new identifications and photometric redshifts for eight faint galaxies and for one quasar and two quasar candidates. Overall we have 27 galaxies with SDSS photometry in five bands, for which we derived the ultraviolet-optical spectral energy distribution (UV-O-SED). We extended our investigation to additional CSS/GPS selected from the literature. Most of the galaxies show an excess of ultra-violet (UV) radiation compared with the UV-O-SED of local radio-quiet ellipticals. We found a strong dependence of the UV excess on redshift and analyzed it assuming that it is generated either from the nucleus (hidden quasar) or from a young stellar population (YSP). We also compare the UV-O-SEDs of our CSS/GPS sources with those of a selection of large size (LSO) powerful radio sources from the literature. Conclusions: If the major process of the UV excess is caused by a YSP, our conclusion is that it is the result of the merger process that also triggered the onset of the radio source with some time delay. We do not see evidence for a major contribution from a YSP triggered by the radio sources itself. Appendices A-G are only available in electronic form at http://www.aanda.org

  15. The development of the radio frequency driven negative ion source for neutral beam injectors (invited)

    International Nuclear Information System (INIS)

    Kraus, W.; Fantz, U.; Franzen, P.; Froeschle, M.; Heinemann, B.; Riedl, R.; Wuenderlich, D.

    2012-01-01

    Large and powerful negative hydrogen ion sources are required for the neutral beam injection (NBI) systems of future fusion devices. Simplicity and maintenance-free operation favors RF sources, which are developed intensively at the Max-Planck-Institut fuer Plasmaphysik (IPP) since many years. The negative hydrogen ions are generated by caesium-enhanced surface conversion of atoms and positive ions on the plasma grid surface. With a small scale prototype the required high ion current density and the low fraction of co-extracted electrons at low pressure as well as stable pulses up to 1 h could be demonstrated. The modular design allows extension to large source dimensions. This has led to the decision to choose RF sources for the NBI of the international fusion reactor, ITER. As an intermediate step towards the full size ITER source at IPP, the development will be continued with a half-size source on the new ELISE testbed. This will enable to gain experience for the first time with negative hydrogen ion beams from RF sources of these dimensions.

  16. RADIO SOURCES FROM A 31 GHz SKY SURVEY WITH THE SUNYAEV-ZEL'DOVICH ARRAY

    International Nuclear Information System (INIS)

    Muchovej, Stephen; Hawkins, David; Lamb, James; Woody, David; Leitch, Erik; Carlstrom, John E.; Culverhouse, Thomas; Greer, Chris; Hennessy, Ryan; Loh, Michael; Marrone, Daniel P.; Pryke, Clem; Sharp, Matthew; Joy, Marshall; Miller, Amber; Mroczkowski, Tony

    2010-01-01

    We present the first sample of 31 GHz selected sources to flux levels of 1 mJy. From late 2005 to mid-2007, the Sunyaev-Zel'dovich Array observed 7.7 deg 2 of the sky at 31 GHz to a median rms of 0.18 mJy beam -1 . We identify 209 sources at greater than 5σ significance in the 31 GHz maps, ranging in flux from 0.7 mJy to ∼200 mJy. Archival NVSS data at 1.4 GHz and observations at 5 GHz with the Very Large Array are used to characterize the sources. We determine the maximum-likelihood integrated source count to be N(>S) = (27.2 ± 2.5)deg -2 x (S mJy ) -1.18±0.12 over the flux range 0.7-15 mJy. This result is significantly higher than predictions based on 1.4 GHz selected samples, a discrepancy which can be explained by a small shift in the spectral index distribution for faint 1.4 GHz sources. From comparison with previous measurements of sources within the central arcminute of massive clusters, we derive an overdensity of 6.8 ± 4.4, relative to field sources.

  17. Improvement in the accuracy of flux measurement of radio sources by exploiting an arithmetic pattern in photon bunching noise

    Science.gov (United States)

    Lieu, Richard

    2018-01-01

    A hierarchy of statistics of increasing sophistication and accuracy is proposed, to exploit an interesting and fundamental arithmetic structure in the photon bunching noise of incoherent light of large photon occupation number, with the purpose of suppressing the noise and rendering a more reliable and unbiased measurement of the light intensity. The method does not require any new hardware, rather it operates at the software level, with the help of high precision computers, to reprocess the intensity time series of the incident light to create a new series with smaller bunching noise coherence length. The ultimate accuracy improvement of this method of flux measurement is limited by the timing resolution of the detector and the photon occupation number of the beam (the higher the photon number the better the performance). The principal application is accuracy improvement in the bolometric flux measurement of a radio source.

  18. Improvement in the Accuracy of Flux Measurement of Radio Sources by Exploiting an Arithmetic Pattern in Photon Bunching Noise

    Energy Technology Data Exchange (ETDEWEB)

    Lieu, Richard [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States)

    2017-07-20

    A hierarchy of statistics of increasing sophistication and accuracy is proposed to exploit an interesting and fundamental arithmetic structure in the photon bunching noise of incoherent light of large photon occupation number, with the purpose of suppressing the noise and rendering a more reliable and unbiased measurement of the light intensity. The method does not require any new hardware, rather it operates at the software level with the help of high-precision computers to reprocess the intensity time series of the incident light to create a new series with smaller bunching noise coherence length. The ultimate accuracy improvement of this method of flux measurement is limited by the timing resolution of the detector and the photon occupation number of the beam (the higher the photon number the better the performance). The principal application is accuracy improvement in the signal-limited bolometric flux measurement of a radio source.

  19. Improved dark energy detection through the polarization-assisted cross correlation of the cosmic microwave background with radio sources

    International Nuclear Information System (INIS)

    Liu, Guo-Chin; Ng, Kin-Wang; Pen, Ue-Li

    2011-01-01

    Integrated Sachs-Wolfe (ISW) effect can be estimated by cross-correlating the cosmic microwave background (CMB) sky with tracers of the local matter distribution. At late cosmic time, the dark energy-induced decay of gravitation potential generates a cross correlation signal on large angular scales. The dominant noise is the intrinsic CMB anisotropies from the inflationary epoch. In this paper we use CMB polarization to reduce this intrinsic noise. We cross-correlate the microwave sky observed by Wilkinson Microwave Anisotropy Probe (WMAP) with the radio source catalog compiled by NRAO VLA Sky Survey (NVSS) to study the efficiency of the noise suppression. We find that the error bars are reduced by about 4 to 14% and the statistical power in the signal is improved.

  20. Discovery of the Millisecond Pulsar PSR J2043+1711 in a Fermi Source with the Nancay Radio Telescope

    Science.gov (United States)

    Guillemot, L.; Freire, P. C. C.; Cognard, I.; Johnson, T. J.; Takahashi, Y.; Kataoka, J.; Desvignes, G.; Camilo, F.; Ferrara, E. C.; Harding, A. K.; hide

    2012-01-01

    We report the discovery of the millisecond pulsar PSR J2043+1711 in a search of a Fermi Large Area Telescope (LAT) source with no known associations, with the Nancay Radio Telescope. The new pulsar, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (d approx. pulsars seen with Fermi. X-ray observations of the pulsar with Suzaku and the Swift X-ray Telescope yielded no detection. At 1.4 GHz, we observe strong flux density variations because of interstellar diffractive scintillation; however, a sharp peak can be observed at this frequency during bright scintillation states. At 327 MHz, the pulsar is detected with a much higher signal-to-noise ratio and its flux density is far more steady. However, at that frequency the Arecibo instrumentation cannot yet fully resolve the pulse profile. Despite that, our pulse time-of-arrival measurements have a post-fit residual rms of 2 micro s. This and the expected stability of this system have made PSR J2043+1711 one of the first new Fermi-selected millisecond pulsars to be added to pulsar gravitational wave timing arrays. It has also allowed a significant measurement of relativistic delays in the times of arrival of the pulses due to the curvature of space-time near the companion, but not yet with enough precision to derive useful masses for the pulsar and the companion. Nevertheless, a mass for the pulsar between 1.7 and 2.0 solar Mass can be derived if a standard millisecond pulsar formation model is assumed. In this paper, we also present a comprehensive summary of pulsar searches in Fermi LAT sources with the Nancay Radio Telescope to date.

  1. Use of reactive gases with broad-beam radio frequency ion sources for industrial applications

    International Nuclear Information System (INIS)

    Schneider, St.; Jolly, T.W.; Kohlstedt, H.; Waser, R.

    2004-01-01

    Broad-beam ion sources are used for a number of important industrial etching and deposition applications, and the use of inductively coupled plasmas has greatly increased the feasibility of using beams of reactive gases, especially of chlorine and oxygen, but also of CO, CO 2 , CF 4 , CHF 3 , SF 6 , etc. In order to gain more understanding of the factors that affect the composition of beams of these gases, we have used a Hiden energy-dispersive quadrupole mass spectrometer to analyze the flux of ions and energetic particles produced by an Oxford Instruments 15 cm rf ion source. For all of the above gases, we have analyzed the effects of changing the operating conditions on the composition of the ion beam, and the fractional production of multiply charged ions; on the plasma potential (and the consequential divergence of the ion beam) and on the spread in energy of the ion beam. We discuss how these factors influence the correct use of the ion source in etching applications with these gases. It is important that the design of the ion source should be optimized for the process gases that are used. The source was originally optimized for use on argon. We discuss the effect of the design on the source's performance with the different gases, and we consider whether design changes would be appropriate for optimum performance on different gases

  2. AN X-RAY COOLING-CORE CLUSTER SURROUNDING A LOW-POWER COMPACT STEEP SPECTRUM RADIO SOURCE 1321+045

    International Nuclear Information System (INIS)

    Kunert-Bajraszewska, M.; Siemiginowska, A.; Labiano, A.

    2013-01-01

    We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 ± 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3σ level out to ∼60'' (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of β = 0.58 ± 0.2 and a core radius of 9.4 +1.1 -0.9 arcsec. The average temperature of the cluster is equal to kT = 4.4 +0.5 -0.3 keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L (0.5-2 k eV) = 3 × 10 44 erg s –1 and mass 1.5 × 10 14 M ☉

  3. AN X-RAY COOLING-CORE CLUSTER SURROUNDING A LOW-POWER COMPACT STEEP SPECTRUM RADIO SOURCE 1321+045

    Energy Technology Data Exchange (ETDEWEB)

    Kunert-Bajraszewska, M. [Torun Centre for Astronomy, Faculty of Physics, Astronomy and Informatics, NCU, Grudziacka 5, 87-100 Torun (Poland); Siemiginowska, A. [Harvard Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138 (United States); Labiano, A., E-mail: magda@astro.uni.torun.pl [Centro de Astrobiologia (CSIC-INTA), Carretera de Ajalvir km. 4, E-28850 Torrejon de Ardoz, Madrid (Spain)

    2013-07-20

    We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 {+-} 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3{sigma} level out to {approx}60'' (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of {beta} = 0.58 {+-} 0.2 and a core radius of 9.4{sup +1.1}{sub -0.9} arcsec. The average temperature of the cluster is equal to kT = 4.4{sup +0.5}{sub -0.3} keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L{sub (0.5-2{sub keV)}} = 3 Multiplication-Sign 10{sup 44} erg s{sup -1} and mass 1.5 Multiplication-Sign 10{sup 14} M{sub Sun}.

  4. Obscured flat spectrum radio active galactic nuclei as sources of high-energy neutrinos

    NARCIS (Netherlands)

    Maggi, G.; Buitink, S.; Correa, P.; de Vries, K. D.; Gentile, G.; Tavares, J. León; Scholten, O.; van Eijndhoven, N.; Vereecken, M.; Winchen, T.

    2016-01-01

    Active galactic nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the cosmic neutrinos detected by IceCube show no

  5. On Asymmetries in Powerful Radio Sources and the Quasar/Galaxy ...

    Indian Academy of Sciences (India)

    3National Centre for Energy Research and Development, University of Nigeria,. Nsukka, Nigeria. ∗ e-mail: ... source orientation and relativistic beaming effects in a sample of powerful non-symmetric ..... shown with open circles in Fig. 6, which ...

  6. Radioisotope Power Sources; Sources d'energie utilisant les radiobotopes; Radioizotopnye istochniki ehnergii; Fuentes radio isotopicas de energia

    Energy Technology Data Exchange (ETDEWEB)

    Culwell, J. P. [USAEC, Washington, D.C (United States)

    1963-11-15

    The radioisotope power programme of the US Atomic Energy Commission has brought forth a whole new technology of the use of radioisotopes as energy sources in electric power generators. Radioisotope power systems are particularly suited for remote applications where long-lived, compact, reliable power is needed. Able to perform satisfactorily under extreme environmental conditions of temperature, sunlight and electromagnetic radiations, these ''atomic batteries'' are attractive power sources for remote data collecting devices, monitoring systems, satellites and other space missions. Radioisotopes used as fuels generally are either alpha or beta emitters. Alpha emitters are the preferable fuels but are more expensive and less available than beta fuels and are generally reserved for space applications. Beta fuels separated from reactor fission wastes are being used exclusively in land and sea applications at the present. It can be expected, however, that beta emitters such as stiontium-90 eventually will be used in space. Development work is being carried out on generators which will use mixed fission products as fuel. This fuel will be less expensive than the pure radioisotopes since the costs of isotope separation and purification are eliminated. Prototype thermoelectric generators, fuelled with strontium-90 and caesium-137, are now in operation or being developed for use in weather stations, marine navigation aids and deep sea monitoring devices. A plutonium-238 thermoelectric generator is in orbit operating as electric power source in a US Navy TRANSIT satellite. Generators are under development for use on US National Aeronautics and Space Administration missions. The large quantities of radioactivity involved in radioisotope power sources require that special attention be given to safety aspects of the units. Rigid safety requirements have been established and extensive tests have been conducted to insure that these systems can be employed without creating undue

  7. UNVEILING THE NATURE OF THE UNIDENTIFIED GAMMA-RAY SOURCES. V. ANALYSIS OF THE RADIO CANDIDATES WITH THE KERNEL DENSITY ESTIMATION

    International Nuclear Information System (INIS)

    Massaro, F.; Funk, S.; D'Abrusco, R.; Paggi, A.; Smith, Howard A.; Masetti, N.; Giroletti, M.; Tosti, G.

    2013-01-01

    Nearly one-third of the γ-ray sources detected by Fermi are still unidentified, despite significant recent progress in this area. However, all of the γ-ray extragalactic sources associated in the second Fermi-LAT catalog have a radio counterpart. Motivated by this observational evidence, we investigate all the radio sources of the major radio surveys that lie within the positional uncertainty region of the unidentified γ-ray sources (UGSs) at a 95% level of confidence. First, we search for their infrared counterparts in the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) and then we analyze their IR colors in comparison with those of the known γ-ray blazars. We propose a new approach, on the basis of a two-dimensional kernel density estimation technique in the single [3.4] – [4.6] – [12] μm WISE color-color plot, replacing the constraint imposed in our previous investigations on the detection at 22 μm of each potential IR counterpart of the UGSs with associated radio emission. The main goal of this analysis is to find distant γ-ray blazar candidates that, being too faint at 22 μm, are not detected by WISE and thus are not selected by our purely IR-based methods. We find 55 UGSs that likely correspond to radio sources with blazar-like IR signatures. An additional 11 UGSs that have blazar-like IR colors have been found within the sample of sources found with deep recent Australia Telescope Compact Array observations

  8. The broad beam ion implanter with the use of radio frequency source

    Energy Technology Data Exchange (ETDEWEB)

    Abdelaziz, M E; Zakhary, S G; Ghanem, A A [Accelerators Dept., Nuclear Research Center, Atomic Energy Authority, Cairo (Egypt)

    1997-12-31

    The project started with the design of the broad beam RF ion source and the single gap accelerating column. The preliminary results of the source show that the ion current extracted from the source could reach 30 m A with extraction voltage = 2 kV. The beam uniformity was made by the use of multi apertures graphite cathode designed to make perveance matching to the normal Gaussian distribution of the ion beam. The beam uniformity could reach 66% of the beam width of 6 cm. The design of the single gap accelerating column based on tracing of beam lines inside the accelerating gap and estimation of the minimum value of the electric field required to contain the beam against space charge expansion in order to achieve minimum beam emittance without aberrations. The preliminary results of the acceleration of the ion beams up to 20 KeV show an increase of the extracted ion current with increase of the extraction voltage. This increase is due to decrease of the angular divergence of the beam due to the effect of increasing the axial velocity component of the accelerated field. 9 figs.

  9. A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 1

    Science.gov (United States)

    Gnanalingam, S.; Kane, J. A.

    1973-01-01

    An extensive set of ground-based measurements of the diurnal variation of medium frequency radio wave adsorption and virtual height is analyzed in terms of current understanding of the D- and lower E-region ion production and loss process. When this is done a gross discrepancy arises, the source of which is not known.

  10. Variations in the small-scale galactic magnetic field and short time-scale intensity variations of extragalactic radio sources

    International Nuclear Information System (INIS)

    Simonetti, J.H.

    1985-01-01

    Structure functions of the Faraday rotation measures (RMs) of extragalactic radio sources are used to investigate variations in the interstellar magnetic field on length scales of approx.0.01 to 100 pc. Model structure functions derived assuming a power-law power spectrum of irregularities in n/sub e/B, are compared with those observed. The results indicate an outer angular scale for RM variations of approximately less than or equal to 5 0 and evidence for RM variations on scales as small as 1'. Differences in the variance of n/sub e/B fluctuations for various lines of sight through the Galaxy are found. Comparison of pulsar scintillations in right- and left-circular polarizations yield an upper limit to the variations in n/sub e/ on a length scale of approx.10 11 cm. RMs were determined through high-velocity molecular flows in galactic star-formation regions, with the goal of constraining magnetic fields in and near the flows. RMs of 7 extragalactic sources with a approx.20 arcmin wide area seen through Cep A, fall in two groups separated by approx.150 rad m -2 - large given our knowledge of RM variations on small angular scales and possibly a result of the anisotropy of the high-velocity material

  11. Measurement and analysis of time-domain characteristics of corona-generated radio interference from a single positive corona source

    Science.gov (United States)

    Li, Xuebao; Li, Dayong; Chen, Bo; Cui, Xiang; Lu, Tiebing; Li, Yinfei

    2018-04-01

    The corona-generated electromagnetic interference commonly known as radio interference (RI) has become a limiting factor for the design of high voltage direct current transmission lines. In this paper, a time-domain measurement system is developed to measure the time-domain characteristics of corona-generated RI from a single corona source under a positive corona source. In the experiments, the corona current pulses are synchronously measured through coupling capacitors. The one-to-one relationship between the corona current pulse and measured RI voltage pulse is observed. The statistical characteristics of pulse parameters are analyzed, and the correlations between the corona current pulse and RI voltage pulse in the time-domain and frequency-domain are analyzed. Depending on the measured corona current pulses, the time-domain waveform of corona-generated RI is calculated on the basis of the propagation model of corona current on the conductor, the dipolar model for electric field calculation, and the antenna model for inducing voltage calculation. The well matched results between measured and simulated waveforms of RI voltage can show the validity of the measurement and calculation method presented in this paper, which also further show the close correlation between corona current and corona-generated RI.

  12. THE Low-level Radio Frequency System for the superconducting cavities of National Synchrotron Light Source II

    International Nuclear Information System (INIS)

    Ma, H.; Rose, J.; Holub, B.; Cupolo, J.; Oliva, J.; Sikora, R.; Yeddulla, M.

    2011-01-01

    A digital low-level radio frequency (LLRF) field controller has been developed for the storage ring of The National Synchrotron Light Source-II (NSLS-II). The primary performance goal for the LLRF is to support the required RF operation of the superconducting cavities with a beam current of 500mA and a 0.14 degree or better RF phase stability. The digital field controller is FPGA-based, in a standard format 19-inch/I-U chassis. It has an option of high-level control support with MATLAB running on a local host computer through a USB2.0 port. The field controller has been field tested with the high-power superconducting RF (SRF) at Canadian light Source, and successfully stored a high beam current of 250 mA. The test results show that required specifications for the cavity RF field stability are met. This digital field controller is also currently being used as a development platform for other functional modules in the NSLS-II RF systems.

  13. Radio and X-ray properties of the source G29.37+0.1 linked to HESS J1844-030

    Science.gov (United States)

    Castelletti, G.; Supan, L.; Petriella, A.; Giacani, E.; Joshi, B. C.

    2017-06-01

    Aims: We report on the first detailed multiwavelength study of the radio source G29.37+0.1, which is an as-yet-unclassified object linked to the very-high-energy γ-emitting source HESS J1844-030. The origin of the multiwavelength emission toward G29.37+0.1 has not been clarified so far, leaving open the question about the physical relationship between these sources. Methods: Using observations carried out with the Giant Metrewave Radio Telescope (GMRT), we performed high-quality full-synthesis imaging at 610 MHz of the field containing G29.37+0.1. The obtained data, combined with observations at 1400 MHz from The Multi-Array Galactic Plane Imaging Survey (MAGPIS) were used to investigate in detail the properties of its radio emission. Additionally, we reprocessed archival data obtained with the XMM-Newton and Chandra observatories in order to get a multiwavelength view of this unusual source. Results: The radio source G29.37+0.1 mainly consists of a bright twisted structure, named the S-shaped feature. The high sensitivity of the new GMRT observations allowed the identification of potential lobes, jets, and a nuclear central region in the S-shaped morphology of G29.37+0.1. We also highlight the detection of diffuse and low surface brightness emission enveloping the brightest emitting regions. The brightest emission in G29.37+0.1 has a radio synchrotron spectral index α = 0.59 ± 0.09. Variations in the spectral behaviour are observed across the whole radio source with the flattest spectral features in the central nuclear and jets components (α 0.3). These results lead us to conclude that the brightest radio emission from G29.37+0.1 likely represents a newly recognized radio galaxy. The identification of optical and infrared counterparts to the emission arising from the core of G29.37+0.1 strengthens our interpretation of an extragalactic origin of the radio emission. We performed several tests to explain the physical mechanism responsible for the observed X

  14. On the errors in measurements of Ohio 5 radio sources in the light of the GB survey

    International Nuclear Information System (INIS)

    Machalski, J.

    1975-01-01

    Positions and flux densities of 405 OSU 5 radio sources surveyed at 1415 MHz down to 0.18 f.u. (Brundage et al. 1971) have been examined in the light of data from the GB survey made at 1400 MHz (Maslowski 1972). An identification analysis has shown that about 56% of OSU sources reveal themselves as single, 18% - as confused, 20% - as unresolved and 6% - having no counterparts in the GB survey down to 0.09 f.u. - seem to be spurious. The single OSU sources are strongly affected by the underestimation of their flux densities due to base-line procedure in their vicinity. The average value of about 0.03 f.u. has been found for the systematic underestimation. The second systematic error is due to the presence of a significant number of confused sources with strong overestimation of their flux densities. The confusion effect gives a characteristic non-Gaussian tail in the difference distribution between observed and real flux densities. The confusion effect has a strong influence on source counts from the OSU 5 survey. Differential number-counts relatively to that from the GB survey shows that the counts agree between themselves within the statistical uncertainty up to about 0.40 f.u., which is approximately 4 delta (delta - average rms flux density error in the OSU 5 survey). Below 0.40 f.u. the number of sources missing due to the confusion effect is significantly greater than the number-overestimation due to the noise error. Thus, this part of the OSU 5 source counts cannot be treated seriously, even in the statistical sense. An analysis of the approximate reliability and completeness of the OSU 5 survey shows that, although the total reliability estimated by the authors of the survey is good, the completeness is significantly lower due to the underestimation of the confusion effect magnitude. In fact, the OSU 5 completeness is 67% at 0.18 f.u. and 79% at 0.25 f.u. (author)

  15. Two new planar coil designs for a high pressure radio frequency plasma source

    Science.gov (United States)

    Munsat, T.; Hooke, W. M.; Bozeman, S. P.; Washburn, S.

    1995-04-01

    Two planar coil designs for a high pressure rf plasma source are investigated using spectroscopic techniques and circuit analysis. In an Ar plasma a truncated version of the commonly used ``spiral'' coil is found to produce improvements in peak electron density of 20% over the full version. A coil with figure-8 geometry is found to move plasma inhomogeneities off of center and produce electron densities comparable to the spiral coils. Both of these characteristics are advantageous in industrial applications. Coil design characteristics for favorable power coupling are also determined, including the necessity of closed hydrodynamic plasma loops and the drawback of closely situated antiparallel coil currents.

  16. Statistical survey of type III radio bursts at long wavelengths observed by the Solar TErrestrial RElations Observatory (STEREO)/Waves instruments: goniopolarimetric properties and radio source locations

    Czech Academy of Sciences Publication Activity Database

    Krupař, Vratislav; Maksimovic, M.; Santolík, Ondřej; Cecconi, B.; Krupařová, Oksana

    2014-01-01

    Roč. 289, č. 12 (2014), s. 4633-4652 ISSN 0038-0938 R&D Projects: GA ČR GP13-37174P; GA ČR GAP205/10/2279; GA ČR(CZ) GAP209/12/2394 Institutional support: RVO:68378289 Keywords : plasma radiation * solar radio emissions Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.039, year: 2014 http://link.springer.com/article/10.1007%2Fs11207-014-0601-z

  17. XMM-Newton and Chandra Observations of the Remarkable Dynamics of the Intracluster Medium and Radio Sources in the Clusters Abell 2061 and 3667

    Science.gov (United States)

    Sarazin, C.; Hogge, T.; Chatzikos, M.; Wik, D.; Giacintucci, S.; Clarke, T.; Wong, K.; Gitti, M.; Finoguenov, A.

    2014-07-01

    XMM-Newton and Chandra observations of remarkable dynamic structures in the X-ray gas and connected radio sources in three clusters are presented. Abell 2061 is a highly irregular, merging cluster in the Corona Borealis supercluster. X-ray observations show that there is a plume of very cool gas (˜1 keV) to the NE of the cluster, and a hot (7.6 keV) shock region just NE of the center. There is a very bright radio relic to the far SW of the cluster, and a central radio halo/relic with an extension to the NE. Comparison to SLAM simulations show that this is an offset merger of a ˜5 × 10^{13} M⊙ subcluster with a ˜2.5 × 10^{14} M⊙ cluster seen after first core passage. The plume is the cool-core gas from the subcluster, which has been ``slingshot'' to the NE of the cluster. The plume gas is now falling back into the cluster center, and shocks when it hits the central gas. The model predicts a strong shock to the SW at the location of the bright radio relic, and another shock at the NE radio extension. Time permitting, the observations of Abell 2626 and Abell 3667 will also be presented.

  18. Radio frequency glow discharge source with integrated voltage and current probes used for evaluation of discharge parameters

    International Nuclear Information System (INIS)

    Wilken, L.; Hoffmann, V.; Wetzig, K.

    2006-01-01

    A radio frequency (rf) Grimm-type glow discharge source for the chemical analysis of solid samples, with integrated voltage and current probes, was developed. All elements of a plasma equivalent circuit are determined from the measured current-voltage characteristics. The procedure is based on the independent evaluation of the ion current and electron current region. The physical meaning of the parameters is investigated by comparisons with measurements from dc glow discharges. We found that the reduced rf current of the powered electrode is comparable to the reduced current in dc discharges. A formula is developed that corrects the reduced current due to gas heating. The sheath thickness at the powered rf electrode is evaluated and is between 75 and 1100 μm. The voltage of the bulk plasma is in the range 2-15 V, and the resistance is between 30 and 400 Ω. The bulk plasma consumes about 3% of the total power, and the reduced voltage is comparable to the reduced electrical field in the positive column of direct current discharges. The sheath voltage at the grounded electrode is in the range 25-100 V, the capacities are between 10 and 400 pF, and the resistances are in the range 100 Ω-5000 Ω. We also found invariants for the evaluated sheath parameters

  19. Deep Submillimeter and Radio Observations in the SSA22 Field. I. Powering Sources and the Lyα Escape Fraction of Lyα Blobs

    Science.gov (United States)

    Ao, Y.; Matsuda, Y.; Henkel, C.; Iono, D.; Alexander, D. M.; Chapman, S. C.; Geach, J.; Hatsukade, B.; Hayes, M.; Hine, N. K.; Kato, Y.; Kawabe, R.; Kohno, K.; Kubo, M.; Lehnert, M.; Malkan, M.; Menten, K. M.; Nagao, T.; Norris, R. P.; Ouchi, M.; Saito, T.; Tamura, Y.; Taniguchi, Y.; Umehata, H.; Weiss, A.

    2017-12-01

    We study the heating mechanisms and Lyα escape fractions of 35 Lyα blobs (LABs) at z ≈ 3.1 in the SSA22 field. Dust continuum sources have been identified in 11 of the 35 LABs, all with star formation rates (SFRs) above 100 M ⊙ yr-1. Likely radio counterparts are detected in 9 out of 29 investigated LABs. The detection of submillimeter dust emission is more linked to the physical size of the Lyα emission than to the Lyα luminosities of the LABs. A radio excess in the submillimeter/radio-detected LABs is common, hinting at the presence of active galactic nuclei. Most radio sources without X-ray counterparts are located at the centers of the LABs. However, all X-ray counterparts avoid the central regions. This may be explained by absorption due to exceptionally large column densities along the line-of-sight or by LAB morphologies, which are highly orientation dependent. The median Lyα escape fraction is about 3% among the submillimeter-detected LABs, which is lower than a lower limit of 11% for the submillimeter-undetected LABs. We suspect that the large difference is due to the high dust attenuation supported by the large SFRs, the dense large-scale environment as well as large uncertainties in the extinction corrections required to apply when interpreting optical data.

  20. Characterization and Application of a Planar Radio - Inductively-Coupled Plasma Source for the Production of Barrier Coatings.

    Science.gov (United States)

    Mahoney, Leonard Joseph

    A planar radio-frequency (rf) inductively-coupled plasma (ICP) source is used to produce fluorocarbon discharges (CF_4/Ar) to fluorinate the surface of high-density polyethylene (HDPE). Using this system, concurrent studies of discharge characteristics, permeation properties of treated polymers and polymer surface characteristics are conducted to advance the use of plasma-fluorinated polymer surfaces as a barrier layer for automotive applications. Langmuir probes are used to determine spatial distribution of charged-particle and space-potential characteristics in Ar and CF_4/Ar discharges and to show the influence of the spatial distribution of the heating regions and the reactor boundaries on the discharge uniformity. Langmuir probes are also used to identify rf anisotropic drift motion of electrons in the heating regions of the source and transient high-energy electron features in pulsed discharges. These latter features allow pulsed ICP sources to be operated at low time-averaged powers that are necessary to treat thermally sensitive polymers. Fourier Transform Infrared (FITR) spectroscopy is used to measure the dissociation of fluorocarbon gases and to explore differences between pulsed- and continuous -power operation. Dissociation levels of CF_4 (50-85%) using pulsed-power operation are as high as that for continuous operation, even though the net time -averaged power is far less with pulsed operation. The result suggests that pulsed fluorocarbon discharges possess high concentrations of chemically-active species needed for rapid surface fluorination. A gravimetric permeation cup method is used to measure the permeation rate of test fuels through HDPE membranes, and electron spectroscopy for chemical analysis (ESCA) studies are performed to determine the stoichiometry and thickness of the barrier layer. From these studies we find that a 50-70 A thick, polar, fluoro-hydrocarbon over layer reduces the permeation of isooctane/toluene/methanol mixtures by a

  1. The superluminal radio source 4c 39. 25 as relativistic jet prototype. El cuasar superluminal 4C 93. 25 como prototipo de jet relativistia

    Energy Technology Data Exchange (ETDEWEB)

    Alberdi, A.; Gomez, J.L.; Marcaide, J.M.

    1993-01-01

    We have developed a numerical code which solves the synchrotron radiation transfer equations to compute the total and polarized emission of bent shocked relativistic jets, and we have applied it to reproduce the compact structure, kinematic evolution of the superluminal radio source 4C 39.25 contains a bent relativistic jet which is misaligned relative to the observer near the core region, leading to a relatively low core brightness. (Author) 12 refs.

  2. Is popular radio a source of exposure to alcohol references in mid to later life? A content analysis.

    Science.gov (United States)

    Haighton, C; Halligan, J; Scott, S

    2017-04-20

    There is concern around alcohol consumption in mid to later life yet little understanding about what influences this behaviour. No previous research has explored the extent to which adults in mid to later life may be exposed to alcohol references in the media. This project aimed to determine the frequency of alcohol references on radio stations with a high proportion of listeners in mid to later life. Content analysis of alcohol references on four popular UK music-based radio stations with a high proportion of listeners aged 55-64 years over three time points. Alcohol references occur frequently, but vary by time of year and type of radio station. When alcohol is mentioned its consumption is portrayed as the norm, without negative consequences. On three commercial stations, the majority of mentions came from advertising, whereas on BBC Radio 2 nearly all references were talk-based. All adverts for direct promotion of alcohol were by supermarkets. Alcohol was frequently associated with celebrations, socializing or something to consume for its own sake. Adults in the age group 55-64 may be exposed to references to alcohol that could serve to reinforce norms of consumption of alcohol and promote purchases of cheap alcohol. © The Author 2017. Published by Oxford University Press on behalf of Faculty of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com

  3. VLA and low-frequency VLBI observations of the radio source 0503 + 467 - Austere constraints on interstellar scattering in two media

    International Nuclear Information System (INIS)

    Spangler, S.R.; Fey, A.L.; Cordes, J.M.; Cornell Univ., Ithaca, NY)

    1987-01-01

    The radio source 0503 + 467 lies near the Galactic plane (l = 161.0 deg, b = 3.7 deg) and at the edge of the supernova remnant (SNR) HB 9. The VLA observations show that it has a spectrum typical of a compact extragalactic radio source. The resultant small angular size of the source makes it an excellent probe of turbulence in two media: the diffuse, or type A, component of interstellar turbulence and a hypothesized region of hydromagnetic turbulence upstream of the supernova remnant. An eight-station VLBI experiment at 326 MHz indicates that the source is less than about 20 milliarcseconds (mas) in angular diameter. A value of 16 mas is most appropriate as an upper limit to the interstellar scattering contribution to the measured angular size. The implications of this upper limit are twofold. First, the galactocentric radial scale to the type-A turbulence is probably less than or equal to about 6 kpc. Second, no evidence is seen for shock-associated turbulence upstream of HB 9. The measurements make it possible to constrain a parameter which is a function of the rms density fluctuation in the upstream region, the outer scale to the density turbulence, and the thickness of SNR foreshock region. 14 references

  4. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole.

    Science.gov (United States)

    Rodrigues, G; Becker, R; Hamm, R W; Baskaran, R; Kanjilal, D; Roy, A

    2014-02-01

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged (238)U(40+) (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  5. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, G., E-mail: gerosro@gmail.com; Kanjilal, D.; Roy, A. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi (India); Becker, R. [Institut fur Angewandte Physik der Universitaet, D-60054 Frankfurt/M (Germany); Hamm, R. W. [R and M Technical Enterprises, Inc., 4725 Arlene Place, Pleasanton, California 94566 (United States); Baskaran, R. [Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamilnadu (India)

    2014-02-15

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged {sup 238}U{sup 40+} (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  6. The direct injection of intense ion beams from a high field electron cyclotron resonance ion source into a radio frequency quadrupole

    Science.gov (United States)

    Rodrigues, G.; Becker, R.; Hamm, R. W.; Baskaran, R.; Kanjilal, D.; Roy, A.

    2014-02-01

    The ion current achievable from high intensity ECR sources for highly charged ions is limited by the high space charge. This makes classical extraction systems for the transport and subsequent matching to a radio frequency quadrupole (RFQ) accelerator less efficient. The direct plasma injection (DPI) method developed originally for the laser ion source avoids these problems and uses the combined focusing of the gap between the ion source and the RFQ vanes (or rods) and the focusing of the rf fields from the RFQ penetrating into this gap. For high performance ECR sources that use superconducting solenoids, the stray magnetic field of the source in addition to the DPI scheme provides focusing against the space charge blow-up of the beam. A combined extraction/matching system has been designed for a high performance ECR ion source injecting into an RFQ, allowing a total beam current of 10 mA from the ion source for the production of highly charged 238U40+ (1.33 mA) to be injected at an ion source voltage of 60 kV. In this design, the features of IGUN have been used to take into account the rf-focusing of an RFQ channel (without modulation), the electrostatic field between ion source extraction and the RFQ vanes, the magnetic stray field of the ECR superconducting solenoid, and the defocusing space charge of an ion beam. The stray magnetic field is shown to be critical in the case of a matched beam.

  7. Radio Wavelength Studies of the Galactic Center Source N3, Spectroscopic Instrumentation For Robotic Telescope Systems, and Developing Active Learning Activities for Astronomy Laboratory Courses

    Science.gov (United States)

    Ludovici, Dominic Alesio

    2017-08-01

    The mysterious radio source N3 appears to be located within the vicinity of the Radio Arc region of the Galactic Center. To investigate the nature of this source, we have conducted radio observations with the VLA and the VLBA. Continuum observations between 2 and 50 GHz reveal that N3 is an extremely compact and bright source with a non-thermal spectrum. Molecular line observations with the VLA reveal a compact molecular cloud adjacent to N3 in projection. The properties of this cloud are consistent with other galactic center clouds. We are able to rule out several hypotheses for the nature of N3, though a micro-blazar origin cannot be ruled out. Robotic Telescope systems are now seeing widespread deployment as both teaching and research instruments. While these systems have traditionally been able to produce high quality images, these systems have lacked the capability to conduct spectroscopic observations. To enable spectroscopic observations on the Iowa Robotic Observatory, we have developed a low cost (˜ 500), low resolution (R ˜ 300) spectrometer which mounts inside a modified filter wheel and a moderate cost (˜ 5000), medium resolution (R ˜ 8000) fiber-fed spectrometer. Software has been developed to operate both instruments robotically and calibration pipelines are being developed to automate calibration of the data. The University of Iowa offers several introductory astronomy laboratory courses taken by many hundreds of students each semester. To improve student learning in these laboratory courses, we have worked to integrate active learning into laboratory activities. We present the pedagogical approaches used to develop and update the laboratory activities and present an inventory of the current laboratory exercises. Using the inventory, we make observations of the strengths and weaknesses of the current exercises and provide suggestions for future refinement of the astronomy laboratory curriculum.

  8. Initial Beam Dynamics Simulations of a High-Average-Current Field-Emission Electron Source in a Superconducting RadioFrequency Gun

    Energy Technology Data Exchange (ETDEWEB)

    Mohsen, O. [Northern Illinois U.; Gonin, I. [Fermilab; Kephart, R. [Fermilab; Khabiboulline, T. [Fermilab; Piot, P. [Northern Illinois U.; Solyak, N. [Fermilab; Thangaraj, J. C. [Fermilab; Yakovlev, V. [Fermilab

    2018-01-05

    High-power electron beams are sought-after tools in support to a wide array of societal applications. This paper investigates the production of high-power electron beams by combining a high-current field-emission electron source to a superconducting radio-frequency (SRF) cavity. We especially carry out beam-dynamics simulations that demonstrate the viability of the scheme to form $\\sim$ 300 kW average-power electron beam using a 1+1/2-cell SRF gun.

  9. Structure in radio galaxies

    International Nuclear Information System (INIS)

    Breugel, W. van.

    1980-01-01

    It is shown that radio jets are a rather common phenomenon in radio galaxies. Jets can be disguised as trails in head-tail sources, bridges in double sources or simply remain undetected because of lack of resolution and sensitivity. It is natural to associate these jets with the channels which had previously been suggested to supply energy to the extended radio lobes. The observations of optical emission suggest that a continuous non-thermal spectrum extending from 10 9 to 10 15 Hz is a common property of jets. Because significant amounts of interstellar matter are also observed in each of the galaxies surveyed it seems that models for jets which involve an interaction with this medium may be most appropriate. New information about the overall structure of extended radio sources has been obtained from the detailed multifrequency study with the WSRT. (Auth.)

  10. Source regions of the type II radio burst observed during a CME–CME interaction on 2013 May 22

    Czech Academy of Sciences Publication Activity Database

    Mäkelä, P.; Gopalswamy, N.; Reiner, M. J.; Akiyama, S.; Krupař, Vratislav

    2016-01-01

    Roč. 827, č. 2 (2016), 141/1-141/7 ISSN 0004-637X R&D Projects: GA ČR(CZ) GAP209/12/2394 Grant - others:AV ČR(CZ) AP1401 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:68378289 Keywords : coronal mass ejections (CMEs) * radio radiation Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 5.533, year: 2016 http://iopscience.iop.org/article/10.3847/0004-637X/827/2/141

  11. The apparent source size of type III radio bursts: Preliminary results by the STEREO/WAVES instruments

    Czech Academy of Sciences Publication Activity Database

    Krupař, Vratislav; Maksimovic, M.; Santolík, Ondřej; Cecconi, B.; Nguyen, Q. N.; Hoang, S.; Goetz, K.

    2010-01-01

    Roč. 1216, č. 1 (2010), s. 284-287 ISSN 0094-243X. [International Solar Wind Conference /12./. Saint-Milo, 21.06.2009-26.06.2009] R&D Projects: GA ČR GAP205/10/2279; GA AV ČR IAA301120601; GA MŠk ME09107 Institutional research plan: CEZ:AV0Z30420517 Keywords : WAVES Instrument * Solar Radio Emissions * Singular Value Decomposition technique Subject RIV: BL - Plasma and Gas Discharge Physics

  12. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    Science.gov (United States)

    Brombin, M.; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

    2014-11-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors' holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns.

  13. Langmuir probes for SPIDER (source for the production of ions of deuterium extracted from radio frequency plasma) experiment: Tests in BATMAN (Bavarian test machine for negative ions)

    International Nuclear Information System (INIS)

    Brombin, M.; Spolaore, M.; Serianni, G.; Pomaro, N.; Taliercio, C.; Palma, M. Dalla; Pasqualotto, R.; Schiesko, L.

    2014-01-01

    A prototype system of the Langmuir probes for SPIDER (Source for the production of Ions of Deuterium Extracted from RF plasma) was manufactured and experimentally qualified. The diagnostic was operated in RF (Radio Frequency) plasmas with cesium evaporation on the BATMAN (BAvarian Test MAchine for Negative ions) test facility, which can provide plasma conditions as expected in the SPIDER source. A RF passive compensation circuit was realised to operate the Langmuir probes in RF plasmas. The sensors’ holder, designed to better simulate the bias plate conditions in SPIDER, was exposed to a severe experimental campaign in BATMAN with cesium evaporation. No detrimental effect on the diagnostic due to cesium evaporation was found during the exposure to the BATMAN plasma and in particular the insulation of the electrodes was preserved. The paper presents the system prototype, the RF compensation circuit, the acquisition system (as foreseen in SPIDER), and the results obtained during the experimental campaigns

  14. Radio stars

    International Nuclear Information System (INIS)

    Hjellming, R.M.; Gibson, D.M.

    1985-01-01

    Studies of stellar radio emission became an important field of research in the 1970's and have now expanded to become a major area of radio astronomy with the advent of new instruments such as the Very Large Array in New Mexico and transcontinental telescope arrays. This volume contains papers from the workshop on stellar continuum radio astronomy held in Boulder, Colorado, and is the first book on the rapidly expanding field of radio emission from stars and stellar systems. Subjects covered include the observational and theoretical aspects of stellar winds from both hot and cool stars, radio flares from active double star systems and red dwarf stars, bipolar flows from star-forming regions, and the radio emission from X-ray binaries. (orig.)

  15. Mechanical Design of the Radio-Isotope Source Driver Module for an Initial Prototype of Medium Dose Rate Brachytherapy

    International Nuclear Information System (INIS)

    Ari Satmoko; Tri Harjanto; Hendra Prasetia

    2012-01-01

    High dose rate brachytherapy equipment for therapy against cervical cancer is developed by empowering local products. An Iridium-192 with 5 Curies of energy is used. The source is wrapped in a capsule and combined with a wire diameter of 1 mm and length 1800 mm. The therapy is carried out by inserting the radiation source into the patient's body through an applicator. The system for loading-unloading the isotope source is divided into three modules: the source driver module, the source container modules, and channel distributor module. In this paper, the discussion is focused on engineering activities of the first module that serves to drive forward and backward position of the Iridium-192 isotope sources. The activity begins with the development of preliminary design sketches that produces drawings of mechanical components required. Furthermore, the calculations are carried out in order to establish the main component specifications. From this stage, a stepper motor type M66-A50K-G10 as a mechanical driver is chosen. The next stage is developing the detailed design and producing detailed drawings for all components. The fabrication of each component refers to the detailed design drawings. All components are assembled completely into the source driver module. Test also shows that the module works manually well. By rotating the manual handle in both directions, the tip of the wire moves alternately in forward and backward directions. (author)

  16. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    Science.gov (United States)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  17. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields.

    Science.gov (United States)

    Freudenstein, Frederik; Wiedemann, Peter M; Brown, Tim W C

    2015-01-01

    The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed.

  18. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields

    Science.gov (United States)

    Wiedemann, Peter M.; Brown, Tim W. C.

    2015-01-01

    The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF) exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one's own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed. PMID:26229540

  19. Exposure Perception as a Key Indicator of Risk Perception and Acceptance of Sources of Radio Frequency Electromagnetic Fields

    Directory of Open Access Journals (Sweden)

    Frederik Freudenstein

    2015-01-01

    Full Text Available The presented survey was conducted in six European countries as an online study. A total of 2454 subjects participated. Two main research questions were investigated: firstly, how does the cognitive, moral, and affective framing of radio frequency electromagnetic field (RF EMF exposure perception influence RF EMF risk perception? Secondly, can the deployment of mobile phone base stations have greater acceptance with RF EMF exposure reduction? The findings with respect to the first question clearly indicated that the cognitive framed exposure perception is the main determinant of RF EMF risk perception. The concomitant sensitivity to exposure strength offers an opportunity to improve the acceptance of base stations by exposure reduction. A linear regression analysis supported this assumption: in a fictional test situation, exposure reduction improved the acceptance of base stations, operationalized as the requested distance of the base station from one’s own home. Furthermore, subjects with high RF EMF risk perception were most sensitive to exposure reduction. On average, a 70% exposure reduction reduced the requested distance from about 2000 meters to 1000 meters. The consequences for risk communication are discussed.

  20. A STUDY OF BROADBAND FARADAY ROTATION AND POLARIZATION BEHAVIOR OVER 1.3–10 GHz IN 36 DISCRETE RADIO SOURCES

    International Nuclear Information System (INIS)

    Anderson, C. S.; Gaensler, B. M.; Feain, I. J.

    2016-01-01

    We present a broadband polarization analysis of 36 discrete polarized radio sources over a very broad, densely sampled frequency band. Our sample was selected on the basis of polarization behavior apparent in narrowband archival data at 1.4 GHz: half the sample shows complicated frequency-dependent polarization behavior (i.e., Faraday complexity) at these frequencies, while half shows comparatively simple behavior (i.e., they appear Faraday simple ). We re-observed the sample using the Australia Telescope Compact Array in full polarization, with 6 GHz of densely sampled frequency coverage spanning 1.3–10 GHz. We have devised a general polarization modeling technique that allows us to identify multiple polarized emission components in a source, and to characterize their properties. We detect Faraday complex behavior in almost every source in our sample. Several sources exhibit particularly remarkable polarization behavior. By comparing our new and archival data, we have identified temporal variability in the broadband integrated polarization spectra of some sources. In a number of cases, the characteristics of the polarized emission components, including the range of Faraday depths over which they emit, their temporal variability, spectral index, and the linear extent of the source, allow us to argue that the spectropolarimetric data encode information about the magneto-ionic environment of active galactic nuclei themselves. Furthermore, the data place direct constraints on the geometry and magneto-ionic structure of this material. We discuss the consequences of restricted frequency bands on the detection and interpretation of polarization structures, and the implications for upcoming spectropolarimetric surveys.

  1. DEEP WIDEBAND SINGLE POINTINGS AND MOSAICS IN RADIO INTERFEROMETRY: HOW ACCURATELY DO WE RECONSTRUCT INTENSITIES AND SPECTRAL INDICES OF FAINT SOURCES?

    Energy Technology Data Exchange (ETDEWEB)

    Rau, U.; Bhatnagar, S.; Owen, F. N., E-mail: rurvashi@nrao.edu [National Radio Astronomy Observatory, Socorro, NM-87801 (United States)

    2016-11-01

    Many deep wideband wide-field radio interferometric surveys are being designed to accurately measure intensities, spectral indices, and polarization properties of faint source populations. In this paper, we compare various wideband imaging methods to evaluate the accuracy to which intensities and spectral indices of sources close to the confusion limit can be reconstructed. We simulated a wideband single-pointing (C-array, L-Band (1–2 GHz)) and 46-pointing mosaic (D-array, C-Band (4–8 GHz)) JVLA observation using a realistic brightness distribution ranging from 1 μ Jy to 100 mJy and time-, frequency-, polarization-, and direction-dependent instrumental effects. The main results from these comparisons are (a) errors in the reconstructed intensities and spectral indices are larger for weaker sources even in the absence of simulated noise, (b) errors are systematically lower for joint reconstruction methods (such as Multi-Term Multi-Frequency-Synthesis (MT-MFS)) along with A-Projection for accurate primary beam correction, and (c) use of MT-MFS for image reconstruction eliminates Clean-bias (which is present otherwise). Auxiliary tests include solutions for deficiencies of data partitioning methods (e.g., the use of masks to remove clean bias and hybrid methods to remove sidelobes from sources left un-deconvolved), the effect of sources not at pixel centers, and the consequences of various other numerical approximations within software implementations. This paper also demonstrates the level of detail at which such simulations must be done in order to reflect reality, enable one to systematically identify specific reasons for every trend that is observed, and to estimate scientifically defensible imaging performance metrics and the associated computational complexity of the algorithms/analysis procedures.

  2. Simulations of cm-wavelength Sunyaev-Zel'dovich galaxy cluster and point source blind sky surveys and predictions for the RT32/OCRA-f and the Hevelius 100-m radio telescope

    Energy Technology Data Exchange (ETDEWEB)

    Lew, Bartosz; Kus, Andrzej [Toruń Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Toruń (Poland); Birkinshaw, Mark [HH Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Wilkinson, Peter, E-mail: blew@astro.uni.torun.pl, E-mail: Mark.Birkinshaw@bristol.ac.uk, E-mail: peter.wilkinson@manchester.ac.uk, E-mail: ajk@astro.uni.torun.pl [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Manchester M13 9PL (United Kingdom)

    2015-02-01

    We investigate the effectiveness of blind surveys for radio sources and galaxy cluster thermal Sunyaev-Zel'dovich effects (TSZEs) using the four-pair, beam-switched OCRA-f radiometer on the 32-m radio telescope in Poland. The predictions are based on mock maps that include the cosmic microwave background, TSZEs from hydrodynamical simulations of large scale structure formation, and unresolved radio sources. We validate the mock maps against observational data, and examine the limitations imposed by simplified physics. We estimate the effects of source clustering towards galaxy clusters from NVSS source counts around Planck-selected cluster candidates, and include appropriate correlations in our mock maps. The study allows us to quantify the effects of halo line-of-sight alignments, source confusion, and telescope angular resolution on the detections of TSZEs. We perform a similar analysis for the planned 100-m Hevelius radio telescope (RTH) equipped with a 49-beam radio camera and operating at frequencies up to 22 GHz.We find that RT32/OCRA-f will be suitable for small-field blind radio source surveys, and will detect 33{sup +17}{sub −11} new radio sources brighter than 0.87 mJy at 30 GHz in a 1 deg{sup 2} field at > 5σ CL during a one-year, non-continuous, observing campaign, taking account of Polish weather conditions. It is unlikely that any galaxy cluster will be detected at 3σ CL in such a survey. A 60-deg{sup 2} survey, with field coverage of 2{sup 2} beams per pixel, at 15 GHz with the RTH, would find <1.5 galaxy clusters per year brighter than 60 μJy (at 3σ CL), and would detect about 3.4 × 10{sup 4} point sources brighter than 1 mJy at 5σ CL, with confusion causing flux density errors ∼< 2% (20%) in 68% (95%) of the detected sources.A primary goal of the planned RTH will be a wide-area (π sr) radio source survey at 15 GHz. This survey will detect nearly 3 × 10{sup 5} radio sources at 5σ CL down to 1.3 mJy, and tens of galaxy

  3. Radio structure in quasars

    International Nuclear Information System (INIS)

    Barthel, P.D.

    1984-01-01

    In this thesis, observational attention is given to the extended extragalactic radio sources associated with quasars. The isolated compact radio sources, often identified with quasars, are only included in the discussions. Three aspects of the radio structure in quasars and their cosmic evolution are considered: a study of the parsec scale morphology in quasar cores, in relation to the extended morphologies; an investigation of possible epoch dependent hotspot properties as well as a more detailed investigation of this fine scale structure; a VLA project was carried out to obtain morphological information on scales of 0.5 arcsec on high redshift quasars and to investigate possible epoch dependent morphological properties. MERLIN observations at 0.1 arcsec resolution to supplement the VLA data were initiated. (Auth.)

  4. Classics in radio astronomy

    CERN Document Server

    Sullivan, Woodruff Turner

    1982-01-01

    Radio techniques were the nrst to lead astronomy away from the quiescent and limited Universe revealed by traditional observations at optical wave­ lengths. In the earliest days of radio astronomy, a handful of radio physicists and engineers made one startling discovery after another as they opened up the radio sky. With this collection of classic papers and the extensive intro­ ductory material, the reader can experience these exciting discoveries, as well as understand the developing techniques and follow the motivations which prompted the various lines of inquiry. For instance he or she will follow in detail the several attempts to detect radio waves from the sun at the turn of the century; the unravelling by Jansky of a "steady hiss type static"; the incredible story of Reber who built a 9 meter dish in his backyard in 1937 and then mapped the Milky Way; the vital discoveries by Hey and colleagues of radio bursts from the Sun and of a discrete source in the constellation of Cygnus; the development of re...

  5. Planck intermediate results: VII. Statistical properties of infrared and radio extragalactic sources from the Planck Early Release Compact Source Catalogue at frequencies between 100 and 857 GHz

    DEFF Research Database (Denmark)

    Cardoso, J.-F.; Delabrouille, J.; Ganga, K.

    2013-01-01

    at high flux-density-and compare it to WMAP, Spitzer and IRAS results. The submillimetre number counts are not well reproduced by current evolution models of dusty galaxies, whereas the millimetre part appears reasonably well fitted by the most recent model for synchrotron-dominated sources. Finally we...

  6. Solar Radio

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Scientists monitor the structure of the solar corona, the outer most regions of the Sun's atmosphere, using radio waves (100?s of MHz to 10?s of GHz). Variations in...

  7. Radio astronomy

    International Nuclear Information System (INIS)

    Parijskij, Y.N.; Gossachinskij, I.V.; Zuckerman, B.; Khersonsky, V.K.; Pustilnik, S.; Robinson, B.J.

    1976-01-01

    A critical review of major developments and discoveries in the field of radioastronomy during the period 1973-1975 is presented. The report is presented under the following headings:(1) Continuum radiation from the Galaxy; (2) Neutral hydrogen, 21 cm (galactic and extragalactic) and recombination lines; (3) Radioastronomy investigations of interstellar molecules; (4) Extragalactic radio astronomy and (6) Development in radio astronomy instruments. (B.R.H.)

  8. Assessment of ultrasound equipment as a possible source of nosocomial infection in Lagos state hospitals and radio-diagnostic centres

    International Nuclear Information System (INIS)

    Akpochafor, M.O.; Eze, C.U.; Adeneye, S.O.; Ajekigbe, A.T.

    2015-01-01

    Aim: To assess the role of ultrasound equipment as a possible source of nosocomial infection in Lagos metropolis, Nigeria. Methods: Microbiological cultures were carried out on samples obtained from ultrasound probes, gel and couch before and after scanning period. Cultures were incubated in a culture plate (Chocolate and MacConkey agar) for 48 h at a temperature of 37 ° in order to grow microorganism, after which the culture plate was examined microscopically against a bright light in order to identify the isolated organisms based on their colonial characteristics. Results: Transabdominal ultrasound probes, transvaginal probe, ultrasound couch and ultrasound gel all were contaminated with microorganisms. Staphylococcus aureus was the most frequent and most common organisms found (33.8%). Other organisms such as Staphylococcus epidermidis (15.4%), Candida albicans (6.2%), aerobic spore formers (26.2%), Klebsiella pneumonia (6.2%), Pseudomonas aeruginosa (3.1%), among others were also identified. Conclusion: The ultrasound equipment posed a significant risk for infection transmission. Patients who underwent ultrasonography within the period of the study had significant chances of being infected with Staphylococcus aureus, S. epidermidis and Aerobic spore formers. - Highlights: • Ultrasound equipment has been shown to be a possible source of nosocomial infection for patient undergoing ultrasonography. • The study showed that Staphylococcus aureus was the most commonly isolated organism. • Transabdominal probe was the most commonly contaminated ultrasound equipment in the finding. • The ultrasound gel was also contaminated with organisms like S. aureus, etc. • There was a statistical significant difference between site of collection of sample and growth density of microorganisms (p = 0.03)

  9. Open-source implementation of an ad-hoc IEEE802.11a/g/p software-defined radio on low-power and low-cost general purpose processors

    Directory of Open Access Journals (Sweden)

    S. Ciccia

    2017-12-01

    Full Text Available This work proposes a low-cost and low-power software-defined radio open-source platform with IEEE 802.11 a/g/p wireless communication capability. A state-of-the-art version of the IEEE 802.11 a/g/p software for GNU Radio (a free and open-source software development framework is available online, but we show here that its computational complexity prevents operations in low-power general purpose processors, even at throughputs below the standard. We therefore propose an evolution of this software that achieves a faster and lighter IEEE 802.11 a/g/p transmitter and receiver, suitable for low-power general purpose processors, for which GNU Radio provides very limited support; we discuss and describe the software radio processing structuring that is necessary to achieve the goal, providing a review of signal processing techniques. In particular, we emphasize the advanced reduced-instruction set (RISC machine (ARM study case, for which we also optimize some of the processing libraries. The presented software will remain open-source.

  10. PSR J2030+364I: Radio Discovery and Gamma-ray Study of a Middle-aged Pulsar in the Now Identified Fermi-LAT Source 1FGL J2030.0+3641

    Science.gov (United States)

    Camilo, F.; Kerr, M.; Ray, P. S.; Ransom, S. M.; Johnston, S.; Romani, R. W.; Parent, D.; Decesar, M. E.; Harding, A. K.; Donato, D.; hide

    2011-01-01

    In a radio search with the Green Bank Telescope of three unidentified low Galactic latitude Fermi-LAT sources, we have discovered the middle-aged pulsar J2030+3641, associated with IFGL J2030.0+3641 (2FGL J2030.0+3640). Following the detection of gamma-ray pulsations using a radio ephemeris, we have obtained a phase-coherent timing solution based on gamma-ray and radio pulse arrival times that spans the entire Fermi mission. With a rotation period of 0.28, spin-down luminosity of 3 x 10(exp 34) erg/s, and characteristic age of 0.5 Myr, PSR J2030+3641 is a middle-aged neutron star with spin parameters similar to those of the exceedingly gamma-ray-bright and radio-undetected Geminga. Its gamma-ray flux is 1 % that of Geminga, primarily because of its much larger distance, as suggested by the large integrated column density of free electrons, DM = 246 pc/cu cm. We fit the gamma-ray light curve, along with limited radio polarimetric constraints, to four geometrical models of magnetospheric emission, and while none of the fits have high significance some are encouraging and suggest that further refinements of these models may be worthwhile. We argue that not many more non-millisecond radio pulsars may be detected along the Galactic plane that are responsible for LAT sources, but that modified methods to search for gamma-ray pulsations should be productive - PSR J2030+364 I would have been found blindly in gamma rays if only > or approx. 0.8 GeV photons had been considered, owing to its relatively flat spectrum and location in a region of high soft background.

  11. Plasma Diagnostics of the Interstellar Medium with Radio Astronomy

    OpenAIRE

    Haverkorn, Marijke; Spangler, Steven R.

    2013-01-01

    We discuss the degree to which radio propagation measurements diagnose conditions in the ionized gas of the interstellar medium (ISM). The "signal generators" of the radio waves of interest are extragalactic radio sources (quasars and radio galaxies), as well as Galactic sources, primarily pulsars. The polarized synchrotron radiation of the Galactic non-thermal radiation also serves to probe the ISM, including space between the emitting regions and the solar system. Radio propagation measurem...

  12. Radio astronomy

    CERN Document Server

    Alder, Berni

    1975-01-01

    Methods in Computational Physics, Volume 14: Radio Astronomy is devoted to the role of the digital computer both as a control device and as a calculator in addressing problems related to galactic radio noise. This volume contains four chapters and begins with a technical description of the hardware and the special data-handling problems of using radioheliography, with an emphasis on a selection of observational results obtained with the Culgoora radioheliograph and their significance to solar physics and to astrophysics in general. The subsequent chapter examines interstellar dispersion, i

  13. The excess radio background and fast radio transients

    International Nuclear Information System (INIS)

    Kehayias, John; Kephart, Thomas W.; Weiler, Thomas J.

    2015-01-01

    In the last few years ARCADE 2, combined with older experiments, has detected an additional radio background, measured as a temperature and ranging in frequency from 22 MHz to 10 GHz, not accounted for by known radio sources and the cosmic microwave background. One type of source which has not been considered in the radio background is that of fast transients (those with event times much less than the observing time). We present a simple estimate, and a more detailed calculation, for the contribution of radio transients to the diffuse background. As a timely example, we estimate the contribution from the recently-discovered fast radio bursts (FRBs). Although their contribution is likely 6 or 7 orders of magnitude too small (though there are large uncertainties in FRB parameters) to account for the ARCADE 2 excess, our development is general and so can be applied to any fast transient sources, discovered or yet to be discovered. We estimate parameter values necessary for transient sources to noticeably contribute to the radio background

  14. Radio observations of symbiotic stars

    Energy Technology Data Exchange (ETDEWEB)

    Wright, A E [Commonwealth Scientific and Industrial Research Organization, Epping (Australia). Div. of Radiophysics; Allen, D A

    1978-09-01

    A search for 2-cm continuum emission from 91 symbiotic stars has been undertaken using the Parkes radio telescope. Nine sources have been detected, four of which are reported for the first time. The radio spectral indices are mostly about + 0.6; these are interpreted in terms of mass loss. In two stars a portion of the radio spectrum has an index of zero, and for one of these stars (RX Puppis) this is plausibly a manifestation of the cessation of symbiotic activity that occurred about two decades ago. There is an extraordinarily good correlation between the detectability at 2cm and the presence of circumstellar dust, but not between the radio and optical domains. The importance of continued radio monitoring of HM Sagittae over the next few years is stressed.

  15. Activities of voluntary public squads in Dnipropetrovsk region in the field of crime prevention during in the late 50’s – mid 60’s of XX century (according the sources connected with Dnipropetrovsk radio factory

    Directory of Open Access Journals (Sweden)

    Malyga, N. M.

    2015-05-01

    Full Text Available In the article considered the activities of voluntary public squads in Dnipropetrovsk region in the field of crime prevention during in the late 50’s – mid 60’s of XX century according the sources connected with Dnipropetrovsk radio factory. This enterprise clearly shows peculiarities of social activity of citizens under the leadership of the Communist Party, which considered labor collective as a main link of communist self government. In Ukrainian and foreign historiography this problem is almost unconsidered. Source base is represented by the fund of State archive of Dnipropetrovsk region, acts of the CC KPSU (Central Committee of the Communist Party of the Soviet Union, and puplications of local press. In the article made an attempt to show the process of functioning of voluntary public squads on the example of Dnipropetrovsk radio factory and show the results in field of crime prevention.

  16. Studies and optimization of Pohang Light Source-II superconducting radio frequency system at stable top-up operation with beam current of 400 mA

    International Nuclear Information System (INIS)

    Joo, Youngdo; Yu, Inha; Park, Insoo; Chun, Myunghwan; Lee, Byung-Joon; Hwang, Ilmoon; Ha, Taekyun; Shin, Seunghwan; Sohn, Younguk

    2014-01-01

    After three years of upgrading work, the Pohang Light Source-II (PLS-II) is now successfully operating. The final quantitative goal of PLS-II is a top-up user-service operation with beam current of 400 mA to be completed by the end of 2014. During the beam store test up to 400 mA in the storage ring (SR), it was observed that the vacuum pressure around the radio frequency (RF) window of the superconducting cavity rapidly increases over the interlock level limiting the availability of the maximum beam current storing. Although available beam current is enhanced by setting a higher RF accelerating voltage, it is better to keep the RF accelerating voltage as low as possible in the long time top-up operation. We investigated the cause of the window vacuum pressure increment by studying the changes in the electric field distribution at the superconducting cavity and waveguide according to the beam current. In our simulation, an equivalent physical modeling was developed using a finite-difference time-domain code. The simulation revealed that the electric field amplitude at the RF window is exponentially increased as the beam current increases, thus this high electric field amplitude causes a RF breakdown at the RF window, which comes with the rapid increase of window vacuum pressure. The RF accelerating voltage of PLS-II RF system was set to 4.95 MV, which was estimated using the maximum available beam current that works as a function of RF voltage, and the top-up operation test with the beam current of 400 mA was successfully carried out

  17. Radio Astronomy Explorer /RAE/. I - Observations of terrestrial radio noise.

    Science.gov (United States)

    Herman, J. R.; Caruso, J. A.; Stone, R. G.

    1973-01-01

    Radio Astronomy Explorer (RAE) I data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial radio noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 dB and more above cosmic noise background, on frequencies above the F-layer critical frequency.

  18. Radio investigations of clusters of galaxies

    International Nuclear Information System (INIS)

    Valentijn, E.A.

    1978-01-01

    This thesis contains a number of papers of the series entitled, A Westerbork Survey of Rich Clusters of Galaxies. The primary aim was to study the radio characteristics of cluster galaxies and especially the question whether their ''radio-activity'' is influenced by their location inside a cluster. It is enquired whether the presence of an intra-cluster medium (ICM), or the typical cluster evolution or cluster dynamical processes can give rise to radio-observable effects on the behaviour of cluster galaxies. 610 MHz WSRT observations of the Coma cluster (and radio observations of the Hercules supercluster) are presented. Extended radio sources in Abell clusters are then described. (Auth.)

  19. The Radio JOVE Project - Shoestring Radio Astronomy

    Science.gov (United States)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  20. Space Telecommunications Radio System STRS Cognitive Radio

    Science.gov (United States)

    Briones, Janette C.; Handler, Louis M.

    2013-01-01

    Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

  1. Contrast source inversion (CSI) method to cross-hole radio-imaging (RIM) data - Part 2: A complex synthetic example and a case study

    Science.gov (United States)

    Li, Yongxing; Smith, Richard S.

    2018-03-01

    We present two examples of using the contrast source inversion (CSI) method to invert synthetic radio-imaging (RIM) data and field data. The synthetic model has two isolated conductors (one perfect conductor and one moderate conductor) embedded in a layered background. After inversion, we can identify the two conductors on the inverted image. The shape of the perfect conductor is better resolved than the shape of the moderate conductor. The inverted conductivity values of the two conductors are approximately the same, which demonstrates that the conductivity values cannot be correctly interpreted from the CSI results. The boundaries and the tilts of the upper and the lower conductive layers on the background can also be inferred from the results, but the centre parts of conductive layers in the inversion results are more conductive than the parts close to the boreholes. We used the straight-ray tomographic imaging method and the CSI method to invert the RIM field data collected using the FARA system between two boreholes in a mining area in Sudbury, Canada. The RIM data include the amplitude and the phase data collected using three frequencies: 312.5 kHz, 625 kHz and 1250 kHz. The data close to the ground surface have high amplitude values and complicated phase fluctuations, which are inferred to be contaminated by the reflected or refracted electromagnetic (EM) fields from the ground surface, and are removed for all frequencies. Higher-frequency EM waves attenuate more quickly in the subsurface environment, and the locations where the measurements are dominated by noise are also removed. When the data are interpreted with the straight-ray method, the images differ substantially for different frequencies. In addition, there are some unexpected features in the images, which are difficult to interpret. Compared with the straight-ray imaging results, the inversion results with the CSI method are more consistent for different frequencies. On the basis of what we learnt

  2. X rays from radio binaries

    International Nuclear Information System (INIS)

    Apparao, K.M.V.

    1977-01-01

    Reference is made to the radio binary systems CC Cas, AR Lac, β Per (Algol), β Lyr, b Per and Cyg X-1. It is stated that a thermal interpretation of the radiation from Algol requires a much larger x-ray flux than the observed value of 3.8 x 10 -11 erg/cm 2 /sec/keV in the 2 to 6 keV energy range. Observations of some non-thermal flares, together with the small size of the radio source in Algol, indicate that the radio emission is non-thermal in nature. The radio emission is interpreted as synchrotron radiation and it is suggested that the observed x-ray emission is due to inverse Compton scattering of the light of the primary star by the radio electrons. The x-ray emission from other radio binaries is also calculated using this model. The energy for the radio electrons can arise from annihilation of magnetic lines connecting the binary stars, twisted by the rotation of the stars. (U.K.)

  3. Microlensing of multiply-imaged compact radio sources - Evidence for compact halo objects in the disk galaxy of B1600+434

    NARCIS (Netherlands)

    Koopmans, LVE; de Bruyn, AG

    We present the first unambiguous case of external variability of a radio gravitational lens, CLASS B1600+434. The Very Lai-ge Array (VLA) 8.5-GHz difference light curve of the lensed images, taking the proper time-delay into account, shows the presence of external variability with 14.6-sigma

  4. Flattening and radio emission among elliptical galaxies

    International Nuclear Information System (INIS)

    Disney, M.J.; Sparks, W.B.; Wall, J.V.

    1984-01-01

    In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)

  5. The Dynamic Radio Sky: An Opportunity for Discovery

    Science.gov (United States)

    2010-01-01

    giant pulses from the Crab pulsar , a small number of dedicated radio transient surveys, and the serendipitous discovery of transient radio sources...used in the discovery of over 1800 radio pulsars . In 2003, the Parkes Multibeam Survey had covered the entire Galactic plane visible from Parkes... pulsars , and confirmed the neutron star nature of these sources, dubbed Rotating Radio Transients (RRATs). Since the discovery of the original 11 RRATs

  6. The radio universe

    International Nuclear Information System (INIS)

    Worvill, R.

    1977-01-01

    Elementary description of the development of radioastronomy, radio waves from the sun and planets, the use of radio telescopes and the detection of nebulae, supernova, radio galaxies and quasars is presented. A brief glossary of terms is included. (UK)

  7. RELATIVISTIC PLASMA AS THE DOMINANT SOURCE OF THE OPTICAL CONTINUUM EMISSION IN THE BROAD-LINE RADIO GALAXY 3C 120

    International Nuclear Information System (INIS)

    Leon-Tavares, J.; Lobanov, A. P.; Arshakian, T. G.; Chavushyan, V. H.; Doroshenko, V. T.; Sergeev, S. G.; Efimov, Y. S.; Nazarov, S. V.

    2010-01-01

    We report a relation between radio emission in the inner jet of the Seyfert galaxy 3C 120 and optical continuum emission in this galaxy. Combining the optical variability data with multi-epoch high-resolution very long baseline interferometry observations reveals that an optical flare rises when a superluminal component emerges into the jet, and its maxima is related to the passage of such component through the location of a stationary feature at a distance of ∼1.3 pc from the jet origin. This indicates that a significant fraction of the optical continuum produced in 3C 120 is non-thermal, and it can ionize material in a sub-relativistic wind or outflow. We discuss implications of this finding for the ionization and structure of the broad emission line region, as well as for the use of broad emission lines for determining black hole masses in radio-loud active galactic nucleus.

  8. A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 2

    Science.gov (United States)

    Gnanalingam, S.; Kane, J. A.

    1975-01-01

    The D-region ion production functions are used to calculate the relationship between radio wave absorption and the flux level of X-rays in the 1-8A wavelength band. In order to bring this calculation into agreement with the empirically established relationship, it was found necessary to reduce by, a factor of about 5, the Meira nitric oxide densities below 90 km.

  9. RADIO VARIABILITY IN SEYFERT NUCLEI

    International Nuclear Information System (INIS)

    Mundell, C. G.; Ferruit, P.; Nagar, N.; Wilson, A. S.

    2009-01-01

    Comparison of 8.4 GHz radio images of a sample of eleven, early-type Seyfert galaxies with previous observations reveals possible variation in the nuclear radio flux density in five of them over a seven year period. Four Seyferts (NGC 2110, NGC 3081, MCG -6-30-15, and NGC 5273) show a decline in their 8.4 GHz nuclear flux density between 1992 and 1999, while one (NGC 4117) shows an increase; the flux densities of the remaining six Seyferts (Mrk 607, NGC 1386, Mrk 620, NGC 3516, NGC 4968, and NGC 7465) have remained constant over this period. New images of MCG -5-23-16 are also presented. We find no correlation between radio variability and nuclear radio luminosity or Seyfert nuclear type, although the sample is small and dominated by type 2 Seyferts. Instead, a possible correlation between the presence of nuclear radio variability and the absence of hundred parsec-scale radio emission is seen, with four out of five marginally resolved or unresolved nuclei showing a change in nuclear flux density, while five out of six extended sources show no nuclear variability despite having unresolved nuclear sources. NGC 2110 is the only source in our sample with significant extended radio structure and strong nuclear variability (∼38% decline in nuclear flux density over seven years). The observed nuclear flux variability indicates significant changes are likely to have occurred in the structure of the nucleus on scales smaller than the VLA beam size (i.e., within the central ∼0.''1 (15 pc)), between the two epochs, possibly due to the appearance and fading of new components or shocks in the jet, consistent with previous detection of subparsec-scale nuclear structure in this Seyfert. Our results suggest that all Seyferts may exhibit variation in their nuclear radio flux density at 8.4 GHz, but that variability is more easily recognized in compact sources in which emission from the variable nucleus is not diluted by unresolved, constant flux density radio jet emission

  10. Optical spectra and radio properties of quasars

    International Nuclear Information System (INIS)

    Wills, B.J.

    1982-01-01

    Using high quality spectrophotometric scans obtained at the McDonald Observatory, and data from the literature the author shows that, for quasars, the relative strength of optical Fe II emission (the broad blended feature lambda4570) may be roughly inversely proportional to line widths (full width at half maximum, FWHM). A similar relation between the relative intensity of the UV Fe II blend between 2300 and 2600 A (the lambda2500 feature) and the widths of Mg II and Hβ is shown. She distinguishes between compact and extended radio sources and includes radio quiet quasars, Seyfert 1 galaxies and BLRG's. The quasars associated with extended radio sources have the broadest emission lines and the weakest Fe II, falling close to the region occupied by BLRG's which also have extended radio structure. Those quasars with strong Fe II and compact radio structure are most similar to the Seyfert 1 galaxies. (Auth.)

  11. Radio search for pulsed emission from X-ray pulsars

    Energy Technology Data Exchange (ETDEWEB)

    delli Santi, F S; Delpino, F [Bologna Univ. (Italy). Ist. di Astronomia; Inzani, P; Sironi, G [Consiglio Nazionale delle Ricerche, Milan (Italy). Lab. di Fisica Cosmica e Tecnologie Relative; Mandolesi, N; Morigi, G [Consiglio Nazionale delle Ricerche, Bologna (Italy). Lab. TESRE

    1981-05-01

    An experiment has been performed at 325 MHz, with a 10 m tracking dish, for the search of pulsed radio emission associated with X-ray pulsars. No evidence of radio pulses has been found in the four sources investigated, although the radio pulsar PSR 0329 + 54, used a testing object, has been detected successfully.

  12. Synthesis imaging in radio astronomy

    International Nuclear Information System (INIS)

    Perley, R.A.; Schwab, F.R.; Bridle, A.H.

    1989-01-01

    Recent advances in techniques and instrumentation for radio synthesis imaging in astronomy are discussed in a collection of review essays. Topics addressed include coherence in radio astronomy, the interferometer in practice, primary antenna elements, cross correlators, calibration and editing, sensitivity, deconvolution, self-calibration, error recognition, and image analysis. Consideration is given to wide-field imaging (bandwidth and time-average smearing, noncoplanar arrays, and mosaicking), high-dynamic-range imaging, spectral-line imaging, VLBI, solar imaging with a synthesis telescope, synthesis imaging of spatially coherent objects, noise in images of very bright sources, synthesis observing strategies, and the design of aperture-synthesis arrays

  13. Sources

    International Nuclear Information System (INIS)

    Duffy, L.P.

    1991-01-01

    This paper discusses the sources of radiation in the narrow perspective of radioactivity and the even narrow perspective of those sources that concern environmental management and restoration activities at DOE facilities, as well as a few related sources. Sources of irritation, Sources of inflammatory jingoism, and Sources of information. First, the sources of irritation fall into three categories: No reliable scientific ombudsman to speak without bias and prejudice for the public good, Technical jargon with unclear definitions exists within the radioactive nomenclature, and Scientific community keeps a low-profile with regard to public information. The next area of personal concern are the sources of inflammation. This include such things as: Plutonium being described as the most dangerous substance known to man, The amount of plutonium required to make a bomb, Talk of transuranic waste containing plutonium and its health affects, TMI-2 and Chernobyl being described as Siamese twins, Inadequate information on low-level disposal sites and current regulatory requirements under 10 CFR 61, Enhanced engineered waste disposal not being presented to the public accurately. Numerous sources of disinformation regarding low level radiation high-level radiation, Elusive nature of the scientific community, The Federal and State Health Agencies resources to address comparative risk, and Regulatory agencies speaking out without the support of the scientific community

  14. Radio Frequency Interference Site Survey for Thai Radio Telescopes

    Science.gov (United States)

    Jaroenjittichai, P.; Punyawarin, S.; Singwong, D.; Somboonpon, P.; Prasert, N.; Bandudej, K.; Kempet, P.; Leckngam, A.; Poshyachinda, S.; Soonthornthum, B.; Kramer, B.

    2017-09-01

    Radio astronomical observations have increasingly been threaten by the march of today telecommunication and wireless technology. Performance of radio telescopes lies within the fact that astronomical sources are extremely weak. National Astronomy Research Institute of Thailand (NARIT) has initiated a 5-year project, known as the Radio Astronomy Network and Geodesy for Development (RANGD), which includes the establishment of 40-meter and 13-meter radio telescopes. Possible locations have been narrowed down to three candidates, situated in the Northern part of Thailand, where the atmosphere is sufficiently dry and suitable for 22 and 43 GHz observations. The Radio Frequency Interference (RFI) measurements were carried out with a DC spectrum analyzer and directional antennas at 1.5 meter above ground, from 20 MHz to 6 GHz with full azimuth coverage. The data from a 3-minute pointing were recorded for both horizontal and vertical polarizations, in maxhold and average modes. The results, for which we used to make preliminary site selection, show signals from typical broadcast and telecommunication services and aeronautics applications. The signal intensity varies accordingly to the presence of nearby population and topography of the region.

  15. The isotropic radio background revisited

    Energy Technology Data Exchange (ETDEWEB)

    Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I–10125 Torino (Italy); Lineros, Roberto A. [Instituto de Física Corpuscular – CSIC/U. Valencia, Parc Científic, calle Catedrático José Beltrán, 2, E-46980 Paterna (Spain); Taoso, Marco, E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: taoso@cea.fr [Institut de Physique Théorique, CEA/Saclay, F-91191 Gif-sur-Yvette Cédex (France)

    2014-04-01

    We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky.

  16. The isotropic radio background revisited

    International Nuclear Information System (INIS)

    Fornengo, Nicolao; Regis, Marco; Lineros, Roberto A.; Taoso, Marco

    2014-01-01

    We present an extensive analysis on the determination of the isotropic radio background. We consider six different radio maps, ranging from 22 MHz to 2.3 GHz and covering a large fraction of the sky. The large scale emission is modeled as a linear combination of an isotropic component plus the Galactic synchrotron radiation and thermal bremsstrahlung. Point-like and extended sources are either masked or accounted for by means of a template. We find a robust estimate of the isotropic radio background, with limited scatter among different Galactic models. The level of the isotropic background lies significantly above the contribution obtained by integrating the number counts of observed extragalactic sources. Since the isotropic component dominates at high latitudes, thus making the profile of the total emission flat, a Galactic origin for such excess appears unlikely. We conclude that, unless a systematic offset is present in the maps, and provided that our current understanding of the Galactic synchrotron emission is reasonable, extragalactic sources well below the current experimental threshold seem to account for the majority of the brightness of the extragalactic radio sky

  17. A repeating fast radio burst.

    Science.gov (United States)

    Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-03-10

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  18. The polarization of radio galaxies

    International Nuclear Information System (INIS)

    Jaegers, W.J.

    1986-01-01

    In this thesis radio observations at 0.6 GHz together with matched (convolved) observations at 1.4 GHz of 30 radiosources are described and interpreted. Sources of great interest which are individually discussed are the complex nearby source 3C66B, the source 4C73.48, the narrow edge-darkened double source 3C130 (together with two newly observed narrow-edge-darkened doubles), the galaxies 3C129 and 3C390.3 and the giant quasar 4C34.47. (Auth.)

  19. Intelligent Cognitive Radio Models for Enhancing Future Radio Astronomy Observations

    Directory of Open Access Journals (Sweden)

    Ayodele Abiola Periola

    2016-01-01

    Full Text Available 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.

  20. sources

    Directory of Open Access Journals (Sweden)

    Shu-Yin Chiang

    2002-01-01

    Full Text Available In this paper, we study the simplified models of the ATM (Asynchronous Transfer Mode multiplexer network with Bernoulli random traffic sources. Based on the model, the performance measures are analyzed by the different output service schemes.

  1. Impact of cognitive radio on radio astronomy

    NARCIS (Netherlands)

    Bentum, Marinus Jan; Boonstra, A.J.; Baan, W.A.

    2010-01-01

    The introduction of new communication techniques requires an increase in the efficiency of spectrum usage. Cognitive radio is one of the new techniques that fosters spectrum efficiency by using unoccupied frequency spectrum for communications. However, cognitive radio will increase the transmission

  2. Fast Radio Bursts

    Indian Academy of Sciences (India)

    Akshaya Rane

    2017-09-12

    ) which were first discovered a decade ago. Following an introduction to radio transients in general, including pulsars and rotating radio transients, we discuss the discovery of FRBs. We then discuss FRB follow-up ...

  3. The crisis of the radio producing

    Directory of Open Access Journals (Sweden)

    Dr. Raúl Garcés

    2007-09-01

    Full Text Available In a media world highly influenced by new technologies revolution and the increasing impact of television, speeches on radio are frequently polarized: in one side, some scholars argue radio belongs to the past and it is no longer able of attracting younger audiences. In the other, lay those who predict long life to radio as a source of alternative and communitarian communication experiences. The author reviews the arguments that sustain both perspectives and emphasizes the need of renovating radio producing with audacious and creative formulas. At the same time, he discusses some of the challenges Cuban radio has ahead to attract new audiences, when television and printed press are recovering from the economic crack the Island suffered after Eastern European socialism disappeared.

  4. The statistics of radio emission from quasars

    International Nuclear Information System (INIS)

    Peacock, J.A.; Miller, L.; Longair, M.S.; Edinburgh Univ.

    1986-01-01

    The radio properties of quasars have traditionally been discussed in terms of the radio-to-optical flux-density ratio R, implying a correlation between emission in these wavebands. It is here shown that, for bright quasars, this apparent correlation is largely due to an abrupt change in the radio properties of the quasar population near absolute magnitude Msub(B)=-24. It is suggested that this change in due to the existence of two classes of quasar with differing host galaxies: a proportion of quasars brighter than Msub(B)approx.=-24 lie in elliptical galaxies and thus generate powerful radio sources, while elliptical galaxies with weaker nuclear quasar components are classified as N-galaxies rather than quasars; quasars fainter than Msub(B)approx.=-24 lie in spiral galaxies and thus are high-luminosity analogues of radio-quiet Seyfert galaxies. (author)

  5. Passive radio frequency peak power multiplier

    Science.gov (United States)

    Farkas, Zoltan D.; Wilson, Perry B.

    1977-01-01

    Peak power multiplication of a radio frequency source by simultaneous charging of two high-Q resonant microwave cavities by applying the source output through a directional coupler to the cavities and then reversing the phase of the source power to the coupler, thereby permitting the power in the cavities to simultaneously discharge through the coupler to the load in combination with power from the source to apply a peak power to the load that is a multiplication of the source peak power.

  6. La radio digital

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo Cortés S.

    2015-01-01

    Full Text Available La radio digital es un producto de la llamada convergencia digital. Las nuevas tecnologías interconectadas permiten la aparición de nuevos modos de audiencia y la implementación de herramientas versátiles. Habla del problema de los estándares, de la radio satelital, la radio digital terrestre, las radios internacionales, la interactividad.

  7. Growth of polycrystalline Cu(In,Ga)Se2 thin films using a radio frequency-cracked Se-radical beam source and application for photovoltaic devices

    International Nuclear Information System (INIS)

    Ishizuka, Shogo; Shibata, Hajime; Yamada, Akimasa; Fons, Paul; Sakurai, Keiichiro; Matsubara, Koji; Niki, Shigeru

    2007-01-01

    Cu(In,Ga)Se 2 (CIGS) thin films were grown using a rf-cracked Se-radical beam source. A unique combination of film properties, a highly dense and smooth surface with large grain size, is shown. These features seem to have no significant influence on the photovoltaic performance. Defect control in bulk CIGS leading to corresponding variations in the electrical and photoluminescence properties was found to be possible by regulating the Se-radical source parameters. A competitive energy conversion efficiency of 17.5%, comparable to that of a Se-evaporative source grown CIGS device, has been demonstrated from a solar cell fabricated using a Se-radical source grown CIGS absorber

  8. The Importance of Site Selection for Radio Astronomy

    International Nuclear Information System (INIS)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2014-01-01

    Radio sources are very weak since this object travel very far from outer space. Radio astronomy studies are limited due to radio frequency interference (RFI) that is made by man. If the harassment is not stopped, it will provide critical problems in their radio astronomy scientists research. The purpose of this study is to provide RFI map Peninsular Malaysia with a minimum mapping techniques RFI interference. RFI mapping technique using GIS is proposed as a tool in mapping techniques. Decision-making process for the selection requires gathering information from a variety of parameters. These factors affecting the selection process are also taken account. In this study, various factors or parameters involved such as availability of telecommunications transmission (including radio and television), rainfall, water line and human activity. This study will benefit radio astronomy research especially in the RFI profile in Malaysia. Keywords: Radio Astronomy, Radio Frequency Interference (RFI), RFI mapping technique : GIS

  9. A turbulent radio jet

    International Nuclear Information System (INIS)

    Kahn, F.D.

    1983-01-01

    A relativistic plasma flow can explain many of the observations on the one-sided jets, which are associated with radio sources that show superluminal motions in their cores. The pressure from the ambient medium will communicate across the jet in a relatively short distance, typically 30 kpc. The friction between the jet and the external medium then makes the flow go turbulent. As a result the jet dissipates energy and will be brought to rest within a few hundred kpc, if it does not strike an obstacle before. The mean flow in the jet is strongly sheared and stretches the lines of force of any magnetic field frozen into the plasma. The dominant field direction, as seen from the rest frame of the plasma, is therefore parallel to the length of the jet. Polarization measurements have shown that this is in fact the case. (author)

  10. Radio frequency picosecond phototube

    International Nuclear Information System (INIS)

    Margaryan, A.; Carlini, R.; Ent, R.; Grigoryan, N.; Gyunashyan, K.; Hashimoto, O.; Hovater, K.; Ispiryan, M.; Knyazyan, S.; Kross, B.; Majewski, S.; Marikyan, G.; Mkrtchyan, M.; Parlakyan, L.; Popov, V.; Tang, L.; Vardanyan, H.; Yan, C.; Zhamkochyan, S.; Zorn, C.

    2006-01-01

    We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a 'head-on' geometry is investigated by means of Monte Carlo simulation

  11. Radio frequency picosecond phototube

    Energy Technology Data Exchange (ETDEWEB)

    Margaryan, A. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia)]. E-mail: mat@mail.yerphi.am; Carlini, R. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Ent, R. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Grigoryan, N. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Gyunashyan, K. [Yerevan State University of Architecture and Construction, Yerevan (Armenia); Hashimoto, O. [Tohoku University, Sendai 98-77 (Japan); Hovater, K. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Ispiryan, M. [University of Houston, 4800 Calhoun Rd, Houston TX 77204 (United States); Knyazyan, S. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Kross, B. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Majewski, S. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Marikyan, G. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Mkrtchyan, M. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Parlakyan, L. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Popov, V. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Tang, L. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Vardanyan, H. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Yan, C. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States); Zhamkochyan, S. [Yerevan Physics Institute, 2 Alikhanian Brothers Street, Yerevan 375036 (Armenia); Zorn, C. [Thomas Jefferson National Accelerator Facility, Newport News VA 23606 (United States)

    2006-10-15

    We propose a photon detector for recording low-level and ultra-fast optical signals, based on radio frequency (RF) analysis of low-energy photoelectrons (PEs). By using currently developed 500 MHz RF deflector, it is possible to scan circularly and detect single PEs, amplified in multi-channel plates (MCPs). The operation of the tube is investigated by means of thermionic electron source. It is demonstrated that the signals generated in the MCP can be processed event by event; by using available nanosecond electronics and that time resolution better than 20 ps can be achieved. Timing characteristics of the Cherenkov detector with RF phototube in a 'head-on' geometry is investigated by means of Monte Carlo simulation.

  12. Giant Metrewave Radio Telescope Observations of Head–Tail Radio Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Sebastian, Biny; Lal, Dharam V.; Rao, A. Pramesh, E-mail: biny@ncra.tifr.res.in [National Center for Radio Astrophysics—Tata Institute of Fundamental Research Post Box 3, Ganeshkhind P.O., Pune 41007 (India)

    2017-10-01

    We present results from a study of seven large known head–tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spectral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of multiple bends and wiggles in several head–tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the radio tails. The prevailing equipartition magnetic field also decreases along the radio tails of these sources. These steepening trends are attributed to the synchrotron aging of plasma toward the ends of the tails. The dynamical ages of these sample sources have been estimated to be ∼10{sup 8} yr, which is a factor of six more than the age estimates from the radiative losses due to synchrotron cooling.

  13. Commercial Radio as Communication.

    Science.gov (United States)

    Rothenbuhler, Eric W.

    1996-01-01

    Compares the day-to-day work routines of commercial radio with the principles of a theoretical communication model. Illuminates peculiarities of the conduct of communication by commercial radio. Discusses the application of theoretical models to the evaluation of practicing institutions. Offers assessments of commercial radio deriving from…

  14. The detectability of radio emission from exoplanets

    Science.gov (United States)

    Lynch, C. R.; Murphy, Tara; Lenc, E.; Kaplan, D. L.

    2018-05-01

    Like the magnetised planets in our Solar System, magnetised exoplanets should emit strongly at radio wavelengths. Radio emission directly traces the planetary magnetic fields and radio detections can place constraints on the physical parameters of these features. Large comparative studies of predicted radio emission characteristics for the known population of exoplanets help to identify what physical parameters could be key for producing bright, observable radio emission. Since the last comparative study, many thousands of exoplanets have been discovered. We report new estimates for the radio flux densities and maximum emission frequencies for the current population of known exoplanets orbiting pre-main sequence and main-sequence stars with spectral types F-M. The set of exoplanets predicted to produce observable radio emission are Hot Jupiters orbiting young stars. The youth of these system predicts strong stellar magnetic fields and/or dense winds, which are key for producing bright, observable radio emission. We use a new all-sky circular polarisation Murchison Widefield Array survey to place sensitive limits on 200 MHz emission from exoplanets, with 3σ values ranging from 4.0 - 45.0 mJy. Using a targeted Giant Metre Wave Radio Telescope observing campaign, we also report a 3σ upper limit of 4.5 mJy on the radio emission from V830 Tau b, the first Hot Jupiter to be discovered orbiting a pre-main sequence star. Our limit is the first to be reported for the low-frequency radio emission from this source.

  15. Radio frequency system for nuclear fusion

    International Nuclear Information System (INIS)

    Kozeki, Shoichiro; Sagawa, Norimoto; Takizawa, Teruhiro

    1987-01-01

    The importance of radio frequency waves has been increasing in the area of nuclear fusion since they are indispensable for heating of plasma, etc. This report outlines radio frequency techniques used for nuclear fusion and describes the development of radio frequency systems (radio frequency plasma heating system and current drive system). Presently, in-depth studies are underway at various research institutes to achieve plasma heating by injection of radio frequency electric power. Three ranges of frequencies, ICRF (ion cyclotron range of frequency), LHRF (lower hybrid range of frequency) and ECRF (electron cyclotron range of frequency), are considered promissing for radio frequency heating. Candidate waves for plasma current driving include ECW (electron cyclotron wave), LHW (lower hybrid wave), MSW (magnetic sound wave), ICW (ion cyclotron wave) with minority component, and FW (fast wave). FW is the greatest in terms of current drive efficiency. In general, a radio frequency system for nuclear fusion consists of a radio frequency power source, transmission/matching circuit component and plasma connection component. (Nogami, K.)

  16. Precision Geodesy via Radio Interferometry.

    Science.gov (United States)

    Hinteregger, H F; Shapiro, I I; Robertson, D S; Knight, C A; Ergas, R A; Whitney, A R; Rogers, A E; Moran, J M; Clark, T A; Burke, B F

    1972-10-27

    Very-long-baseline interferometry experiments, involving observations of extragalactic radio sources, were performed in 1969 to determine the vector separations between antenna sites in Massachusetts and West Virginia. The 845.130-kilometer baseline was estimated from two separate experiments. The results agreed with each other to within 2 meters in all three components and with a special geodetic survey to within 2 meters in length; the differences in baseline direction as determined by the survey and by interferometry corresponded to discrepancies of about 5 meters. The experiments also yielded positions for nine extragalactic radio sources, most to within 1 arc second, and allowed the hydrogen maser clocks at the two sites to be synchronized a posteriori with an uncertainty of only a few nanoseconds.

  17. Ham radio for dummies

    CERN Document Server

    Silver, H Ward

    2013-01-01

    An ideal first step for learning about ham radio Beyond operating wirelessly, today's ham radio operators can transmit data and pictures; use the Internet, laser, and microwave transmitters; and travel to places high and low to make contact. This hands-on beginner guide reflects the operational and technical changes to amateur radio over the past decade and provides you with updated licensing requirements and information, changes in digital communication (such as the Internet, social media, and GPS), and how to use e-mail via radio. Addresses the critical use of ham radio for replacing downe

  18. Recent radio studies of SNR

    International Nuclear Information System (INIS)

    Dickel, J.R.

    1983-01-01

    SNR can generally be recognized as extended sources of continuum radio emission with non-thermal spectra located near the galactic plane. The author describes the kinds of observations currently being obtained and what they tell us about the objects. The data include continuum observations which can reach resolutions of about 1 arcsec using aperture synthesis techniques and also spectral line observations of the interstellar matter being encountered by the remnants. (Auth.)

  19. Radiography of Spanish Radio

    Directory of Open Access Journals (Sweden)

    Dra. Emma Rodero Antón

    2007-01-01

    Full Text Available In its eighty years of existence, radio has been always characterized to adapt to the social, cultural and technological transformations. Thus it has been until this moment. Nevertheless, some years ago, the authors and professionals of this medium have been detecting a stagnation that affects to its structure. At a time in continuous technological evolution, radio demands a deep transformation. For that reason, from the conviction of which the future radio, public and commercial, will necessarily have to renew itself, in this paper we establish ten problems and their possible solutions to the radio crisis in order to draw an x-ray of radio in Spain. Radio has future, but it is necessary to work actively by it. That the radio continues being part of sound of our life, it will depend on the work of all: companies, advertisers, professionals, students, investigators and listeners.

  20. Biodiversity Loss in the Orion Radio Zoo?

    Science.gov (United States)

    Henney, W. J.; García-Díaz, Ma. T.; Kurtz, S. E.

    2001-03-01

    We re-examine radio observations of compact sources in the core of the Orion nebula and find that 70% of the sources correspond to known proplyds. For all of these sources, including many that have been previously classified as variable and non-thermal, the radio flux between 1.5 and 86 Ghz is fully accounted for by thermal free-free emission from the photoevaporation flow. We therefore suggest that many of the proposed Orion FOXES are in fact EIDERS, and that their apparent variability reflects observational difficulties in detecting the lower surface-brightness portions of the proplyds. The PIGs turn out to be extinct in Orion, and the hybrid creatures that we dub PANTHERS (Proplyds Associated with Non-THErmal Radio Sources) remain elusive.

  1. THE RADIO PROPERTIES OF RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES ON PARSEC SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Minfeng; Chen, Yongjun; Shen, Zhiqiang [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Komossa, S.; Zensus, J. A. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Yuan, Weimin [Key Lab for Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Wajima, Kiyoaki [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong, Daejeon 305-348 (Korea, Republic of); Zhou, Hongyan, E-mail: gumf@shao.ac.cn [Polar Research Institute of China, 451 Jinqiao Road, Shanghai 200136 (China)

    2015-11-15

    We present the detection of the compact radio structures of 14 radio-loud narrow-line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array (VLBA) observations at 5 GHz performed in 2013. While 50% of the sources of our sample show a compact core only, the remaining 50% exhibit a core-jet structure. The measured brightness temperatures of the cores range from 10{sup 8.4} to 10{sup 11.4} K with a median value of 10{sup 10.1} K, indicating that the radio emission is from non-thermal jets, and that, likely, most sources are not strongly beamed, thus implying a low jet speed in these radio-loud NLS1 galaxies. In combination with archival data taken at multiple frequencies, we find that seven sources show flat or even inverted radio spectra, while steep spectra are revealed in the remaining seven objects. Although all of these sources are very radio-loud with R > 100, their jet properties are diverse in terms of their milliarcsecond (mas) scale (parsec scale) morphology and their overall radio spectral shape. The evidence for slow jet speeds (i.e., less relativistic jets), in combination with the low kinetic/radio power, may offer an explanation for the compact VLBA radio structure in most sources. The mildly relativistic jets in these high accretion rate systems are consistent with a scenario where jets are accelerated from the hot corona above the disk by the magnetic field and the radiation force of the accretion disk. Alternatively, a low jet bulk velocity can be explained by low spin in the Blandford–Znajek mechanism.

  2. An open-source hardware GPS data logger for wildlife radio-telemetry studies: A case study using Eastern box turtles

    Directory of Open Access Journals (Sweden)

    Patrick W. Cain

    2018-04-01

    Full Text Available Global Positioning System (GPS telemetry technology has been a boon to animal spatial ecology studies. Oftentimes, the main limitation to widespread application of this technology is the cost, which can dictate the number of individuals outfitted with GPS technology, thereby limiting sample sizes. Here, we discuss the development of a low-cost, customizable, open-source hardware GPS logger for use in animal movement studies. We also present results from field tests with Eastern box turtles (Terrapene carolina in northwestern Ohio. These GPS loggers have the potential to augment existing projects and facilitate studies that would be otherwise cost-prohibitive. Keywords: GPS, Data logger, Arduino, Eastern box turtle

  3. Radio Astronomy Explorer (RAE) 1 observations of terrestrial radio noise

    Science.gov (United States)

    Herman, J. R.; Caruso, J. A.

    1971-01-01

    Radio Astonomy Explorer (RAE) 1 data are analyzed to establish characteristics of HF terrestrial radio noise at an altitude of about 6000 km. Time and frequency variations in amplitude of the observed noise well above cosmic noise background are explained on the basis of temporal and spatial variations in ionospheric critical frequency coupled with those in noise source distributions. It is shown that terrestrial noise regularly breaks through the ionosphere and reaches RAE with magnitudes 15 or more db higher than cosmic noise background. Maximum terrestrial noise is observed when RAE is over the dark side of the Earth in the neighborhood of equatorial continental land masses where thunderstorms occur most frequently. The observed noise level is 30-40 db lower with RAE over oceans.

  4. Senior radio listeners

    DEFF Research Database (Denmark)

    Blaakilde, Anne Leonora

    Radiobroadcasting and the hardware materialization of radio have during the 20th century changed significantly, which means that senior radio listeners have travelled along with this evolution from large, impressive radio furnitures to DAB and small, wireless, mobile devices, and from grave...... and solemn radio voices to lightharted, laughing and chatting speakers. Senior radio listerners have experienced the development and refinements of technique, content and genres. It is now expected of all media users that they are capable of crossing media, combining, juggling and jumping between various...... media platforms, not the least when listening to radio. The elder generation is no exception from this. Recently, for instance, the Danish public broadcast DR has carried out an exodus of programmes targeted for the senior segment. These programmes are removed from regular FM and sent to DAB receivers...

  5. Radio-flaring Ultracool Dwarf Population Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Route, Matthew, E-mail: mroute@purdue.edu [Department of Astronomy and Astrophysics, the Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

    2017-08-10

    Over a dozen ultracool dwarfs (UCDs), low-mass objects of spectral types ≥M7, are known to be sources of radio flares. These typically several-minutes-long radio bursts can be up to 100% circularly polarized and have high brightness temperatures, consistent with coherent emission via the electron cyclotron maser operating in approximately kilogauss magnetic fields. Recently, the statistical properties of the bulk physical parameters that describe these UCDs have become described adequately enough to permit synthesis of the population of radio-flaring objects. For the first time, I construct a Monte Carlo simulator to model the population of these radio-flaring UCDs. This simulator is powered by Intel Secure Key (ISK), a new processor technology that uses a local entropy source to improve random number generation that has heretofore been used to improve cryptography. The results from this simulator indicate that only ∼5% of radio-flaring UCDs within the local interstellar neighborhood (<25 pc away) have been discovered. I discuss a number of scenarios that may explain this radio-flaring fraction and suggest that the observed behavior is likely a result of several factors. The performance of ISK as compared to other pseudorandom number generators is also evaluated, and its potential utility for other astrophysical codes is briefly described.

  6. Population Studies of Radio and Gamma-Ray Pulsars

    Science.gov (United States)

    Harding, Alice K; Gonthier, Peter; Coltisor, Stefan

    2004-01-01

    Rotation-powered pulsars are one of the most promising candidates for at least some of the 40-50 EGRET unidentified gamma-ray sources that lie near the Galactic plane. Since the end of the EGRO mission, the more sensitive Parkes Multibeam radio survey has detected mere than two dozen new radio pulsars in or near unidentified EGRET sources, many of which are young and energetic. These results raise an important question about the nature of radio quiescence in gamma-ray pulsars: is the non-detection of radio emission a matter of beaming or of sensitivity? The answer is very dependent on the geometry of the radio and gamma-ray beams. We present results of a population synthesis of pulsars in the Galaxy, including for the first time the full geometry of the radio and gamma-ray beams. We use a recent empirically derived model of the radio emission and luminosity, and a gamma-ray emission geometry and luminosity derived theoretically from pair cascades in the polar slot gap. The simulation includes characteristics of eight radio surveys of the Princeton catalog plus the Parkes MB survey. Our results indicate that EGRET was capable of detecting several dozen pulsars as point sources, with the ratio of radio-loud to radio-quiet gamma-ray pulsars increasing significantly to about ten to one when the Parkes Survey is included. Polar cap models thus predict that many of the unidentified EGRET sources could be radio-loud gamma- ray pulsars, previously undetected as radio pulsars due to distance, large dispersion and lack of sensitivity. If true, this would make gamma-ray telescopes a potentially more sensitive tool for detecting distant young neutron stars in the Galactic plane.

  7. Radio propagation through the turbulent interstellar plasma

    International Nuclear Information System (INIS)

    Rickett, B.J.

    1990-01-01

    The current understanding of interstellar scattering is reviewed, and its impact on radio astronomy is examined. The features of interstellar plasma turbulence are also discussed. It is concluded that methods involving the investigation of the flux variability of pulsars and extragalactic sources and the VLBI visibility curves constitute new techniques for probing the ISM. However, scattering causes a seeing limitation in radio observations. It is now clear that variation due to RISS (refractive interstellar scintillations) is likely to be important for several classes of variable sources, especially low-frequency variables and centimeter-wave flickering. 168 refs

  8. Ionosphere and Radio Communication

    Indian Academy of Sciences (India)

    The upperionosphere is used for radio communication and navigationas it reflects long, medium, as well as short radio waves. Sincesolar radiation is the main cause of the existence of ionosphere,any variation in the radiations can affect the entireradio communication system. This article attempts to brieflyintroduce the ...

  9. Writing for Radio.

    Science.gov (United States)

    Tupper, Marianna S.

    1995-01-01

    Describes a 24-hour commercial radio station simulation class project for eighth-grade language arts. Students wrote their own scripts, chose music and were disc jockeys on their own music and talk shows, and prepared news and traffic reports. Guest speakers from actual commercial radio came in to discuss issues such as advertising, censorship,…

  10. Valuing commercial radio licences

    NARCIS (Netherlands)

    Kerste, M.; Poort, J.; van Eijk, N.

    2015-01-01

    Within the EU regulatory framework, licensees for commercial radio broadcasting may be charged a fee to ensure optimal allocation of scarce resources but not to maximize public revenues. While radio licence renewal occurs in many EU countries, an objective, model-based approach for setting licence

  11. The Radio Jove Project

    Science.gov (United States)

    Thieman, J. R.

    2010-01-01

    The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

  12. Boom Booom Net Radio

    DEFF Research Database (Denmark)

    Grimshaw, Mark Nicholas; Yong, Louisa; Dobie, Ian

    1999-01-01

    of an existing Internet radio station; Boom Booom Net Radio. Whilst necessity dictates some use of technology-related terminology, wherever possible we have endeavoured to keep such jargon to a minimum and to either explain it in the text or to provide further explanation in the appended glossary....

  13. Advances in solar radio astronomy

    Science.gov (United States)

    Kundu, M. R.

    1982-01-01

    The status of the observations and interpretations of the sun's radio emission covering the entire radio spectrum from millimeter wavelengths to hectometer and kilometer wavelengths is reviewed. Emphasis is given to the progress made in solar radio physics as a result of recent advances in plasma and radiation theory. It is noted that the capability now exists of observing the sun with a spatial resolution of approximately a second of arc and a temporal resolution of about a millisecond at centimeter wavelengths and of obtaining fast multifrequency two-dimensional pictures of the sun at meter and decameter wavelengths. A summary is given of the properties of nonflaring active regions at millimeter, centimeter, and meter-decameter wavelengths. The properties of centimeter wave bursts are discussed in connection with the high spatial resolution observations. The observations of the preflare build-up of an active region are reviewed. High spatial resolution observations (a few seconds of arc to approximately 1 arcsec) are discussed, with particular attention given to the one- and two-dimensional maps of centimeter-wavelength burst sources.

  14. Radio-continuum emission from quasar host galaxies

    International Nuclear Information System (INIS)

    Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)

    1987-01-01

    Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references

  15. Radio emission in peculiar galaxies

    Science.gov (United States)

    Demellorabaca, Dulia F.; Abraham, Zulema

    1990-01-01

    During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

  16. Mengusung Masyarakat Madani Melalui Radio Komunitas

    Directory of Open Access Journals (Sweden)

    Dede Lilis Chaerowati

    2013-12-01

    Full Text Available This article is about the phenomenon of community radio in Pantura Area, West Java. Radio communities maganed by, for and about the community are rapidly developing among the farmers and fishermen, including in Pantura Area, West Java. The focus of the study is the formation of civil society by standing firmly on communicative actions of Jürgen Habermas. By using qualitative method with case study design, a finding would be produced that community radios implement participatory paradigm and manage community cohesion. We will discuss in details on: (1 initiators of the establishment of community radio, (2 forms of community participation, (3 the financing source of community radio, and (4 the construction of civil society through community radio. This article also covers about how the people see the world of life, that there is social transformation through emancipatordialogs, which then produce community’s selfconsciousness  as individuals and community members in demanding a domination-free communication process. This reality creates the origination of civil society.

  17. Unlocking radio broadcasts

    DEFF Research Database (Denmark)

    Skov, Mette; Lykke, Marianne

    2012-01-01

    This poster reports the preliminary results of a user study uncovering the information seeking behaviour of humanities scholars dedicated to radio research. The study is part of an interdisciplinary research project on radio culture and auditory resources. The purpose of the study is to inform...... the design of information architecture and interaction design of a research infrastructure that will enable future radio and audio based research. Results from a questionnaire survey on humanities scholars‟ research interest and information needs, preferred access points, and indexing levels are reported....... Finally, a flexible metadata schema is suggested, that includes both general metadata and highly media and research project specific metadata....

  18. Radio y elecciones

    Directory of Open Access Journals (Sweden)

    Alma Rosa Alva de la Selva

    2000-01-01

    Full Text Available En este trabajo se analiza el comportamiento de la radio en México ante la contienda electoral de julio de 2000. Se examina el papel de la radio como espacio para la discusión política, así como el tratamiento informativo que hizo del tema. Asimismo, se analiza la posible repercusión de factores de reciente surgimiento en el panorama radiofónico para un manejo más autónomo de la información política en la radio

  19. Heavy element concentration determination by the x-ray fluorescence analysis using radioisotope {gamma}-ray sources; Dosage d'elements lourds par fluorescence X utilisant des radio-sources de rayons gamma

    Energy Technology Data Exchange (ETDEWEB)

    Enomoto, S [Commissariat a l' Energie Atomique, Dir. des Materiaux et des Combustibles Nucleaires, Saclay (France). Centre d' Etudes Nucleaires

    1968-07-01

    A theoretical and experimental study has been made on the fluorescence analysis of high atomic number element, using {gamma}-ray sources for excitation and characteristic K X-rays for the measurement. The choice of the proper {gamma}-ray energy according to the conditions of the determination is considered. The author has studied the usefulness of using the backscattered {gamma}-rays as a correction mean for matrix and grain-size effects. Sources of {sup 153}Gd, {sup 57}Co, {sup 137}Cs have been used for excitation using collimated geometries. Concentration measurements of tungsten in steel, tungsten and lead in aqueous solution, PbS in SiO{sub 2}-PbS powder mixtures have been done, as well as thickness evaluation of gold layers on copper. A precision of about 0.2 per cent (abs.) is obtained for lead determination in light matrixes. A probe design is proposed for the continuous determination of lead in aqueous solutions. (author) [French] On etudie de maniere theorique et experimentale l'analyse d'elements a nombre atomique eleve par fluorescence en utilisant des sources de rayons {gamma} pour l'excitation, et des rayons-X K caracteristiques pour la mesure. On considere le choix de l'energie appropriee des rayons {gamma} suivant les conditions experimentales. L'utilite d'employer les rayons {gamma} retrodiffuses pour corriger les effets de la matrice et de la dimension des grains est etudiee. Des sources de {sup 153}Gd, de {sup 57}Co et de {sup 137}Cs a geometrie collimatee ont ete utilisees pour l'excitation. Des mesures de la concentration du tungstene dans l'acier, du tungstene et du plomb en solutions aqueuses, et du PbS dans des melanges de poudre SiO{sub 2}-PbS ont ete entreprises ainsi que l'evaluation de l'epaisseur des couches d'or sur le cuivre. On obtient une precision d'environ 0,2 pour cent (en absolu) pour la determination du plomb dans des matrices legeres. On propose un modele de sonde pour la determination en continu du plomb en solution aqueuse

  20. VLA radio observations of AR Scorpii

    Science.gov (United States)

    Stanway, E. R.; Marsh, T. R.; Chote, P.; Gänsicke, B. T.; Steeghs, D.; Wheatley, P. J.

    2018-03-01

    Aims: AR Scorpii is unique amongst known white dwarf binaries in showing powerful pulsations extending to radio frequencies. Here we aim to investigate the multi-frequency radio emission of AR Sco in detail, in order to constrain its origin and emission mechanisms. Methods: We present interferometric radio frequency imaging of AR Sco at 1.5, 5 and 9 GHz, analysing the total flux and polarization behaviour of this source at high time resolution (10, 3 and 3 s), across a full 3.6 h orbital period in each band. Results: We find strong modulation of the radio flux on the orbital period and the orbital sideband of the white dwarf's spin period (also known as the "beat" period). This indicates that, like the optical flux, the radio flux arises predominantly from on or near the inner surface of the M-dwarf companion star. The beat-phase pulsations of AR Sco decrease in strength with decreasing frequency. They are strongest at 9 GHz and at an orbital phase 0.5. Unlike the optical emission from this source, radio emission from AR Sco shows weak linear polarization but very strong circular polarization, reaching 30% at an orbital phase 0.8. We infer the probable existence of a non-relativistic cyclotron emission component, which dominates at low radio frequencies. Given the required magnetic fields, this also likely arises from on or near the M-dwarf. A table of the flux time series is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/611/A66

  1. The cluster environments of powerful, high-redshift radio galaxies

    International Nuclear Information System (INIS)

    Yates, M.G.

    1989-01-01

    We present deep imaging of a sample of 25 powerful radio galaxies in the redshift range 0.15 gr ) about each source, a measure of the richness of environment. The powerful radio galaxies in this sample at z>0.3 occupy environments nearly as rich on average as Abell class 0 clusters of galaxies, about three times richer than the environments of the z<0.3 radio galaxies. This trend in cluster environment is consistent with that seen in radio-loud quasars over the same redshift range. Our previous work on the 3CR sample suggested that the fundamental parameter which correlates with the richness of environment might be the radio luminosity of the galaxy, rather than its redshift. Our direct imaging confirms that the most powerful radio galaxies do inhabit rich environments. (author)

  2. RADIO-SELECTED QUASARS IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    McGreer, Ian D.; Helfand, David J.; White, Richard L.

    2009-01-01

    We have conducted a pilot survey for z > 3.5 quasars by combining the FIRST radio survey with the Sloan Digital Sky Survey (SDSS). While SDSS already targets FIRST sources for spectroscopy as quasar candidates, our survey includes fainter quasars and greatly improves the discovery rate by using strict astrometric criteria for matching the radio and optical positions. Our method allows for selection of high-redshift quasars with less color bias than with optical selection, as using radio selection essentially eliminates stellar contamination. We report the results of spectroscopy for 45 candidates, including 29 quasars in the range 0.37 3.5. We compare quasars selected using radio and optical criteria, and find that radio-selected quasars have a much higher fraction of moderately reddened objects. We derive a radio-loud quasar luminosity function at 3.5 < z < 4.0, and find that it is in good agreement with expectations from prior SDSS results.

  3. Magnetized environs of a repeating radio burst

    Science.gov (United States)

    Metzger, Brian D.

    2018-03-01

    One of the astrophysical sources that gives rise to the mysterious transients known as fast radio bursts is embedded in a highly magnetized environment, such as the vicinity of an accreting massive black hole or the birth nebula of a highly magnetized neutron star.

  4. Social cognitive radio networks

    CERN Document Server

    Chen, Xu

    2015-01-01

    This brief presents research results on social cognitive radio networks, a transformational and innovative networking paradigm that promotes the nexus between social interactions and cognitive radio networks. Along with a review of the research literature, the text examines the key motivation and challenges of social cognitive radio network design. Three socially inspired distributed spectrum sharing mechanisms are introduced: adaptive channel recommendation mechanism, imitation-based social spectrum sharing mechanism, and evolutionarily stable spectrum access mechanism. The brief concludes with a discussion of future research directions which ascertains that exploiting social interactions for distributed spectrum sharing will advance the state-of-the-art of cognitive radio network design, spur a new line of thinking for future wireless networks, and enable novel wireless service and applications.

  5. NOAA Weather Radio

    Science.gov (United States)

    del tiempo incluido. Si eres quieres ser avisado de las advertencias y relojes de día o de noche, un Weather Radio relojes son independientes o basadas en el Condado (parroquia basados en Luisiana), aunque

  6. The digital sport radio.

    Directory of Open Access Journals (Sweden)

    Hilario José ROMERO BEJARANO

    2014-07-01

    Full Text Available Radio has been immersed in recent years in a phase of technological integration and business of multimedia, as well as diversification of systems and channels for broadcasting. In addition, Internet has been consolidated as the platform of digital radio that more has evolved as a result of its continued expansion. However, the merger radio-Internet must be understood as a new form of communication, and not solely as a new complementary medium. In this context, it is of great interest to analyze that transformations in the way of reception, contents, languages, programs and schedules, has brought with it for the radio that integration. To this end is taken as main reference the sports areas, a key aspect and broadly representative of the current broadcasting landscape.

  7. Music, radio and mediatization

    DEFF Research Database (Denmark)

    Michelsen, Morten; Krogh, Mads

    2016-01-01

    of mediatization where media as such seem to be ascribed agency. Instead, we consider historical accounts of music–radio in order to address the complex nonlinearity of concrete processes of mediatization as they take place in the multiple meetings between a decentred notion of radio and musical life.......Mediatization has become a key concept for understanding the relations between media and other cultural and social fields. Contributing to the discussions related to the concept of mediatization, this article discusses how practices of radio and music(al life) influence each other. We follow Deacon......’s and Stanyer’s advice to supplement the concept of mediatization with ‘a series of additional concepts at lower levels of abstraction’ and suggest, in this respect, the notion of heterogeneous milieus of music–radio. Hereby, we turn away from the all-encompassing perspectives related to the concept...

  8. ITSY Handheld Software Radio

    National Research Council Canada - National Science Library

    Bose, Vanu

    2001-01-01

    .... A handheld software radio platform would enable the construction of devices that could inter-operate with multiple legacy systems, download new waveforms and be used to construct adhoc networks...

  9. Wireless radio a history

    CERN Document Server

    Coe, Lewis

    2006-01-01

    ""Informative...recommended""--Choice; ""interesting...a good read...well worth reading""--Contact Magazine. This history first looks at Marconi's wireless communications system and then explores its many applications, including marine radio, cellular telephones, police and military uses, television and radar. Radio collecting is also discussed, and brief biographies are provided for the major figures in the development and use of the wireless.

  10. ¿Radios ciudadanas?

    OpenAIRE

    López Vigil, José Ignacio

    1998-01-01

    Educativas, sindicales, populares, comunitarias, libres, rebeldes, participativas, alternativas, alterativas, han sido las denominaciones de la radio cuando su proyecto está al servicio de la gente. Palabras apropiadas y nobles -dice elautor-pero devaluadas, a las que ahora se agrega la radio ciudadana, para relievarla como ejercicio depoder y espacio de verdadera participación de la genteenla vida de su nación.

  11. ON THE ORIGIN OF FANAROFF-RILEY CLASSIFICATION OF RADIO GALAXIES: DECELERATION OF SUPERSONIC RADIO LOBES

    International Nuclear Information System (INIS)

    Kawakatu, Nozomu; Kino, Motoki; Nagai, Hiroshi

    2009-01-01

    We argue that the origin of 'FRI/FRII dichotomy' - the division between Fanaroff-Riley class I (FRI) with subsonic lobes and class II (FRII) radio sources with supersonic lobes is sharp in the radio-optical luminosity plane (Owen-White diagram) - can be explained by the deceleration of advancing radio lobes. The deceleration is caused by the growth of the effective cross-sectional area of radio lobes. We derive the condition in which an initially supersonic lobe turns into a subsonic lobe, combining the ram pressure equilibrium between the hot spots and the ambient medium with the relation between 'the hot spot radius' and 'the linear size of radio sources' obtained from the radio observations. We find that the dividing line between the supersonic lobes and subsonic ones is determined by the ratio of the jet power L j to the number density of the ambient matter at the core radius of the host galaxy n-bar a . It is also found that the maximal ratio of (L j ,n-bar a ) exists and its value resides in (L j ,n-bar a ) max ∼10 44-47 er s -1 cm 3 , taking into account considerable uncertainties. This suggests that the maximal value (L j ,n-bar a ) max separates between FRIs and FRIIs.

  12. Fossil shell emission in dying radio loud AGNs

    Science.gov (United States)

    Kino, M.; Ito, H.; Kawakatu, N.; Orienti, M.; Nagai, H.; Wajima, K.; Itoh, R.

    2016-02-01

    We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV γ-ray band and can be detectable by CTA. Data from STELLA

  13. No evidence for radio-quiet BL Lacertae objects

    International Nuclear Information System (INIS)

    Stocke, J.T.; Morris, S.L.; Gioia, I.; Maccacaro, T.; Schild, R.E.

    1990-01-01

    Using a large, flux-limited sample of faint X-ray sources, a search has been conducted for radio-quiet BL Lacertae objects. None has been found. Thirty-two X-ray-selected BL Lac objects and BL Lac candidates have been found within the sources of the Einstein Medium Sensitivity Survey (EMSS). Thirty-one of these have been observed with the VLA and all have been detected at 5 GHz. While the optical magnitudes of the EMSS BL Lac objects range from 17 to 20.8, their radio-to-optical spectral indices occupy a very small range. The very bright X-ray-selected BL Lac objects like PKS 2155-304 and Markarian 501 have similar range values. Therefore, unlike the clear dichotomy between radio-loud quasars and radio-quiet QSOs, there is no evidence for two populations of Lacertids distinguished by radio loudness. 43 refs

  14. Dynamical evolution in clusters of galaxies with low-frequency radio emission

    International Nuclear Information System (INIS)

    Guthrie, B.N.G.

    1977-01-01

    Clusters of galaxies in which radio emission at low frequencies ( approximately 10 9 yr). Confinement would probably occur for radio sources associated with bright galaxies in the cores of clusters and cD galaxies in clusters. However, cD galaxies may have recurrent radio outbursts so that steep spectra are not always observed. (Auth.)

  15. Radio emission from the nova-like variable AC Cancri and the symbiotic variable AG Draconis

    International Nuclear Information System (INIS)

    Torbett, M.V.; Campbell, B.; Mount Wilson and Las Campanas Observatories, Pasadena, CA)

    1987-01-01

    Radio emission at 6 cm has been detected from the nova-like cataclysmic variable AC Cnc and the symbiotic variable AG Dra. The AC Cnc observation constitutes the first radio detection in this class of objects. The AG Dra source is probably resolved and appears to show asymmetric, extended structure. The radio emission can best be explained by thermal bremsstrahlung. 26 references

  16. Facets of radio-loud AGN evolution : a LOFAR surveys perspective

    NARCIS (Netherlands)

    Williams, Wendy L.

    2015-01-01

    Radio observations provide a unique view of black holes in the Universe. This thesis presents low frequency radio images and uses the radio sources in those images to study the evolution of black holes and galaxies through the age of the Universe.

  17. LOFAR tied-array imaging of Type III solar radio bursts

    NARCIS (Netherlands)

    Morosan, D.E.; et al., [Unknown; Hessels, J.W.T.; Markoff, S.

    2014-01-01

    Context. The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), the Sun has not been imaged extensively because of the instrumental limitations of previous radio

  18. LOFAR tied-array imaging of Type III solar radio bursts

    NARCIS (Netherlands)

    Morosan, D.E.; Gallagher, P.T.; Zucca, P.; Fallows, R.; Carley, E.P.; Mann, G.; Bisi, M.M.; Kerdraon, A.; Avruch, I.M.; Bentum, Marinus Jan; Bernardi, G.; Best, P.; Bonafede, A.; Bregman, J.; Breitling, F.

    2014-01-01

    Context: The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (<100 MHz), the Sun has not been imaged extensively because of the instrumental limitations of previous radio

  19. Solar radio observations and interpretations

    International Nuclear Information System (INIS)

    Rosenberg, H.

    1976-01-01

    The recent solar radio observations related to flares are reviewed for the frequency range of a few kilohertz to several gigahertz. The analysis of the radio data leads to boundary conditions on the acceleration processes which are responsible for the fast particles which cause radio emission. The role and cause of plasma turbulence at the plasma-frequency and at much lower frequencies is discussed in relation to the acceleration processes and the radio emission mechanisms for the various radio bursts. (author)

  20. Millijansky radio variability in SDSS stripe 82

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, J. A.; Becker, R. H. [University of California, 1 Shields Avenue, Davis, CA 95616 (United States); White, R. L. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Richards, G. T., E-mail: hodge@mpia.de [Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States)

    2013-06-01

    We report on a blind survey for extragalactic radio variability that was carried out by comparing two epochs of data from the Faint Images of the Radio Sky at Twenty centimeters survey with a third epoch from a new 1.4 GHz survey of SDSS Stripe 82. The three epochs are spaced seven years apart and have an overlapping area of 60 deg{sup 2}. We uncover 89 variable sources down to the millijansky level, 75 of which are newly identified, and we find no evidence for transient phenomena. This new sample of variable sources allows us to infer an upper limit to the mean characteristic timescale of active galactic nucleus radio variability of 14 yr. We find that only 1% of extragalactic sources have fractional variability f {sub var} > 3, while 44% of Galactic sources vary by this much. The variable sample contains a larger fraction of quasars than a comparable non-variable control sample, though the majority of the variable sources appear to be extended galaxies in the optical. This implies that either quasars are not the dominant contributor to the variability of the sample, or that the deep optical data allow us to detect the host galaxies of some low-z quasars. We use the new, higher resolution data to report on the morphology of the variable sources. Finally, we show that the fraction of sources that are variable remains constant or increases at low flux densities. This may imply that next generation radio surveys with telescopes like Australian Square Kilometer Array Pathfinder and MeerKAT will see a constant or even increasing fraction of variable sources down into the sub-millijansky regime.

  1. The radio halo and active galaxies in the Coma cluster

    International Nuclear Information System (INIS)

    Cordey, R.A.

    1985-01-01

    The Cambridge Low-Frequency Synthesis Telescope has been used to map the Coma cluster at 151 MHz. Two new extended sources are found, associated with the cluster galaxies NGC4839 and NGC4849. The central halo radio source is shown not to have a simple symmetrical structure but to be distorted, with separate centres of brightening near the radio galaxies NGC4874 and IC4040. The structure cannot be accounted for by cluster-wide acceleration processes but implies a close connection with current radio galaxies and, in particular, models requiring diffusion of electrons out of radio sources seem to be favoured. The other large source, near Coma A, is detected and higher resolution data at 1407 MHz are used to clarify its structure. (author)

  2. Radio images of the interplanetary turbulent plasma

    International Nuclear Information System (INIS)

    Vlasov, V.I.

    1979-01-01

    The results of the interplanetary scintillation daily observations of approximately 140 radio sources are given. The observations were carried out at the radiotelescope VLPA FIAN during 24 days in October-November 1975 and 6 days in April 1976. The maps (radio images) of interplanetary turbulent plasma are presented. The analysis of the maps reveals the presence of large-scale irregularities in the interplanetary plasma. The variability in large-scale structure of the interplanetary plasma is due mainly to transport of matter from the Sun. A comparison of the scintillation with the geomagnetic activity index detected the presence of a straight connection between them

  3. Radio Observations of Gamma-ray Novae

    Science.gov (United States)

    Linford, Justin D.; Chomiuk, L.; Ribeiro, V.; project, E.-Nova

    2014-01-01

    Recent detection of gamma-ray emission from classical novae by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope surprised many in the astronomical community. We present results from radio observations, obtained using the Karl G. Jansky Very Large Array (VLA), of three gamma-ray novae: Mon2012, Sco2012, and Del2013. Radio observations allow for the calculation of ejecta masses, place limits on the distances, and provide information about the gamma-ray emission mechanism for these sources.

  4. ARTIP: Automated Radio Telescope Image Processing Pipeline

    Science.gov (United States)

    Sharma, Ravi; Gyanchandani, Dolly; Kulkarni, Sarang; Gupta, Neeraj; Pathak, Vineet; Pande, Arti; Joshi, Unmesh

    2018-02-01

    The Automated Radio Telescope Image Processing Pipeline (ARTIP) automates the entire process of flagging, calibrating, and imaging for radio-interferometric data. ARTIP starts with raw data, i.e. a measurement set and goes through multiple stages, such as flux calibration, bandpass calibration, phase calibration, and imaging to generate continuum and spectral line images. Each stage can also be run independently. The pipeline provides continuous feedback to the user through various messages, charts and logs. It is written using standard python libraries and the CASA package. The pipeline can deal with datasets with multiple spectral windows and also multiple target sources which may have arbitrary combinations of flux/bandpass/phase calibrators.

  5. Mean and extreme radio properties of quasars and the origin of radio emission

    Energy Technology Data Exchange (ETDEWEB)

    Kratzer, Rachael M.; Richards, Gordon T. [Department of Physics, Drexel University, Philadelphia, PA (United States)

    2015-02-01

    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  6. EXTENDED RADIO EMISSION IN MOJAVE BLAZARS: CHALLENGES TO UNIFICATION

    International Nuclear Information System (INIS)

    Kharb, P.; Lister, M. L.; Cooper, N. J.

    2010-01-01

    We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile 'core-only' source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 A, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

  7. Extended Radio Emission in MOJAVE Blazars: Challenges to Unification

    Science.gov (United States)

    Kharb, P.; Lister, M. L.; Cooper, N. J.

    2010-02-01

    We present the results of a study on the kiloparsec-scale radio emission in the complete flux density limited MOJAVE sample, comprising 135 radio-loud active galactic nuclei. New 1.4 GHz Very Large Array (VLA) radio images of six quasars and previously unpublished images of 21 blazars are presented, along with an analysis of the high-resolution (VLA A-array) 1.4 GHz emission for the entire sample. While extended emission is detected in the majority of the sources, about 7% of the sources exhibit only radio core emission. We expect more sensitive radio observations, however, to detect faint emission in these sources, as we have detected in the erstwhile "core-only" source, 1548+056. The kiloparsec-scale radio morphology varies widely across the sample. Many BL Lac objects exhibit extended radio power and kiloparsec-scale morphology typical of powerful FRII jets, while a substantial number of quasars possess radio powers intermediate between FRIs and FRIIs. This poses challenges to the simple radio-loud unified scheme, which links BL Lac objects to FRIs and quasars to FRIIs. We find a significant correlation between extended radio emission and parsec-scale jet speeds: the more radio powerful sources possess faster jets. This indicates that the 1.4 GHz (or low-frequency) radio emission is indeed related to jet kinetic power. Various properties such as extended radio power and apparent parsec-scale jet speeds vary smoothly between different blazar subclasses, suggesting that, at least in terms of radio jet properties, the distinction between quasars and BL Lac objects, at an emission-line equivalent width of 5 Å, is essentially an arbitrary one. While the two blazar subclasses display a smooth continuation in properties, they often reveal differences in the correlation test results when considered separately. This can be understood if, unlike quasars, BL Lac objects do not constitute a homogeneous population, but rather include both FRI and FRII radio galaxies for

  8. INTERSTELLAR SCINTILLATION AND THE RADIO COUNTERPART OF THE FAST RADIO BURST FRB 150418

    Energy Technology Data Exchange (ETDEWEB)

    Akiyama, Kazunori [Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States); Johnson, Michael D., E-mail: kazu@haystack.mit.edu [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2016-06-10

    Keane et al. have recently reported the discovery of a new fast radio burst (FRB), FRB 150418, with a promising radio counterpart at 5.5 and 7.5 GHz—a rapidly decaying source, falling from 200–300 μ Jy to 100 μ Jy on timescales of ∼6 days. This transient source may be associated with an elliptical galaxy at redshift z = 0.492, providing the first firm spectroscopic redshift for an FRB and the ability to estimate the density of baryons in the intergalactic medium via the combination of known redshift and radio dispersion of the FRB. An alternative explanation, first suggested by Williams and Berger, is that the identified counterpart may instead be a compact active galactic nucleus (AGN). The putative counterpart’s variation may then instead be extrinsic, caused by refractive scintillation in the ionized interstellar medium of the Milky Way, which would invalidate the association with FRB 150418. We examine this latter explanation in detail and show that the reported observations are consistent with scintillating radio emission from the core of a radio-loud AGN having a brightness temperature T {sub b} ≳ 10{sup 9} K. Using numerical simulations of the expected scattering for the line of sight to FRB 150418, we provide example images and light curves of such an AGN at 5.5 and 7.5 GHz. These results can be compared with continued radio monitoring to conclusively determine the importance of scintillation for the observed radio variability, and they show that scintillation is a critical consideration for continued searches for FRB counterparts at radio wavelengths.

  9. INTERSTELLAR SCINTILLATION AND THE RADIO COUNTERPART OF THE FAST RADIO BURST FRB 150418

    International Nuclear Information System (INIS)

    Akiyama, Kazunori; Johnson, Michael D.

    2016-01-01

    Keane et al. have recently reported the discovery of a new fast radio burst (FRB), FRB 150418, with a promising radio counterpart at 5.5 and 7.5 GHz—a rapidly decaying source, falling from 200–300 μ Jy to 100 μ Jy on timescales of ∼6 days. This transient source may be associated with an elliptical galaxy at redshift z = 0.492, providing the first firm spectroscopic redshift for an FRB and the ability to estimate the density of baryons in the intergalactic medium via the combination of known redshift and radio dispersion of the FRB. An alternative explanation, first suggested by Williams and Berger, is that the identified counterpart may instead be a compact active galactic nucleus (AGN). The putative counterpart’s variation may then instead be extrinsic, caused by refractive scintillation in the ionized interstellar medium of the Milky Way, which would invalidate the association with FRB 150418. We examine this latter explanation in detail and show that the reported observations are consistent with scintillating radio emission from the core of a radio-loud AGN having a brightness temperature T _b ≳ 10"9 K. Using numerical simulations of the expected scattering for the line of sight to FRB 150418, we provide example images and light curves of such an AGN at 5.5 and 7.5 GHz. These results can be compared with continued radio monitoring to conclusively determine the importance of scintillation for the observed radio variability, and they show that scintillation is a critical consideration for continued searches for FRB counterparts at radio wavelengths.

  10. FAST RADIO BURSTS AND RADIO TRANSIENTS FROM BLACK HOLE BATTERIES

    Energy Technology Data Exchange (ETDEWEB)

    Mingarelli, Chiara M. F. [TAPIR, MC 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Levin, Janna [Institute for Strings, Cosmology and Astroparticle Physics (ISCAP), Columbia University, New York, NY 10027 (United States); Lazio, T. Joseph W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-12-01

    Most black holes (BHs) will absorb a neutron star (NS) companion fully intact without tidal disruption, suggesting the pair will remain dark to telescopes. Even without tidal disruption, electromagnetic (EM) luminosity is generated from the battery phase of the binary when the BH interacts with the NS magnetic field. Originally, the luminosity was expected to be in high-energy X-rays or gamma-rays, however, we conjecture that some of the battery power is emitted in the radio bandwidth. While the luminosity and timescale are suggestive of fast radio bursts (FRBs; millisecond-scale radio transients) NS–BH coalescence rates are too low to make these a primary FRB source. Instead, we propose that the transients form a FRB sub-population, distinguishable by a double peak with a precursor. The rapid ramp-up in luminosity manifests as a precursor to the burst which is 20%–80% as luminous given 0.5 ms timing resolution. The main burst arises from the peak luminosity before the merger. The post-merger burst follows from the NS magnetic field migration to the BH, causing a shock. NS–BH pairs are especially desirable for ground-based gravitational wave (GW) observatories since the pair might not otherwise be detected, with EM counterparts greatly augmenting the scientific leverage beyond the GW signal. The EM signal’s ability to break degeneracies in the parameters encoded in the GW and probe the NS magnetic field strength is quite valuable, yielding insights into open problems in NS magnetic field decay.

  11. FAST RADIO BURSTS AND RADIO TRANSIENTS FROM BLACK HOLE BATTERIES

    International Nuclear Information System (INIS)

    Mingarelli, Chiara M. F.; Levin, Janna; Lazio, T. Joseph W.

    2015-01-01

    Most black holes (BHs) will absorb a neutron star (NS) companion fully intact without tidal disruption, suggesting the pair will remain dark to telescopes. Even without tidal disruption, electromagnetic (EM) luminosity is generated from the battery phase of the binary when the BH interacts with the NS magnetic field. Originally, the luminosity was expected to be in high-energy X-rays or gamma-rays, however, we conjecture that some of the battery power is emitted in the radio bandwidth. While the luminosity and timescale are suggestive of fast radio bursts (FRBs; millisecond-scale radio transients) NS–BH coalescence rates are too low to make these a primary FRB source. Instead, we propose that the transients form a FRB sub-population, distinguishable by a double peak with a precursor. The rapid ramp-up in luminosity manifests as a precursor to the burst which is 20%–80% as luminous given 0.5 ms timing resolution. The main burst arises from the peak luminosity before the merger. The post-merger burst follows from the NS magnetic field migration to the BH, causing a shock. NS–BH pairs are especially desirable for ground-based gravitational wave (GW) observatories since the pair might not otherwise be detected, with EM counterparts greatly augmenting the scientific leverage beyond the GW signal. The EM signal’s ability to break degeneracies in the parameters encoded in the GW and probe the NS magnetic field strength is quite valuable, yielding insights into open problems in NS magnetic field decay

  12. FM Radio and Youth: Listeners or Users?

    Directory of Open Access Journals (Sweden)

    Marina Mučalo

    2014-06-01

    Full Text Available A survey conducted in the spring of 2013, says that Zagreb’s high school students are not regular listeners to FM radio programs. The dominant media is the Internet, which is used a few hours a day, mostly for Facebook. Despite the expressed need for music, the linear and passive nature of FM radio, does not correspond to the individual requirements of young and networked users. The Internet is the most popular daily source for music, with ability to download, while smartphones are becoming devices for storage and playback. However, this survey has shown that students are interested in web radio sites. Changes in media preferences and habits caused by the Internet show us the importance of information literacy, as a basic skill for participation in a networked society.

  13. Tools of radio astronomy

    CERN Document Server

    Wilson, Thomas L; Hüttemeister, Susanne

    2013-01-01

    This 6th edition of “Tools of Radio Astronomy”, the most used introductory text in radio astronomy, has been revised to reflect the current state of this important branch of astronomy. This includes the use of satellites, low radio frequencies, the millimeter/sub-mm universe, the Cosmic Microwave Background and the increased importance of mm/sub-mm dust emission. Several derivations and presentations of technical aspects of radio astronomy and receivers, such as receiver noise, the Hertz dipole and  beam forming have been updated, expanded, re-worked or complemented by alternative derivations. These reflect advances in technology. The wider bandwidths of the Jansky-VLA and long wave arrays such as LOFAR and mm/sub-mm arrays such as ALMA required an expansion of the discussion of interferometers and aperture synthesis. Developments in data reduction algorithms have been included. As a result of the large amount of data collected in the past 20 years, the discussion of solar system radio astronomy, dust em...

  14. Innovations to enrich science communication through radio

    Directory of Open Access Journals (Sweden)

    Thakar Bhaumik

    2004-12-01

    Full Text Available The Radio is an instrument of communication that has percolated to all the strata of the diverse Indian society. Its position has been consolidated through history as a regular companion and a source of information and entertainment. Its affordability, accessibility and non-reliance on costly resources have ensured its presence in almost all the households. It has become indispensable from kitchens, family rooms and even workspaces. It is one of the few or rather the only medium of communication after the print media wherein information dissemination still is primary and entertainment a secondary requirement, especially the rural areas. The role of radio in rural India is one that demands prominence and hence has been used as a primary resource for various projects on science communication. A majority of the science radio serial listeners are from the rural areas. The radio therefore is an ideal medium for reaching out to the masses. The radio even with its popularity and huge following is lacking in certain aspects that make science communication complete. Manthan Educational Programme Society developed concepts to make these efforts more effective by ensuring higher involvement and interest in these programs.

  15. Identification of a Likely Radio Counterpart to the Rapid Burster

    Science.gov (United States)

    Moore, Christopher B.; Rutledge, Robert E.; Fox, Derek W.; Guerriero, Robert A.; Lewin, Walter H. G.; Fender, Robert; van Paradijs, Jan

    2000-04-01

    We have identified a likely radio counterpart to the low-mass X-ray binary MXB 1730-335 (the Rapid Burster). The counterpart has shown 8.4 GHz radio on/off behavior correlated with the X-ray on/off behavior as observed by the RXTE/ASM during six VLA observations. The probability of an unrelated, randomly varying background source duplicating this behavior is 1%-3% depending on the correlation timescale. The location of the radio source is R.A. 17h33m24.61s, decl. -33 deg23'19.8" (J2000), +/-0.1". We do not detect 8.4 GHz radio emission coincident with type II (accretion-driven) X-ray bursts. The ratio of radio to X-ray emission during such bursts is constrained to be below the ratio observed during X-ray-persistent emission at the 2.9 σ level. Synchrotron bubble models of the radio emission can provide a reasonable fit to the full data set, collected over several outbursts, assuming that the radio evolution is the same from outburst to outburst but given the physical constraints the emission is more likely to be due to ~1 hr radio flares such as have been observed from the X-ray binary GRS 1915+105.

  16. The Impact of Radio Interference on Future Radio Telescopes

    Science.gov (United States)

    Mitchell, Daniel A.; Robertson, Gordon J.; Sault, Robert J.

    While future radio telescopes will require technological advances from the communications industry interference from sources such as satellites and mobile phones is a serious concern. In addition to the fact that the level of interference is growing constantly the increased capabilities of next generation instruments make them more prone to harmful interference. These facilities must have mechanisms to allow operation in a crowded spectrum. In this report some of the factors which may limit the effectiveness of these mechanisms are investigated. Radio astronomy is unique among other observing wavelengths in that the radiation can be fully sampled at a rate which completely specifies the electromagnetic environment. Knowledge of phases and antennae gain factors affords one the opportunity to attempt to mitigate interference from the astronomical data. At present several interference mitigation techniques have been demonstrated to be extremely effective. However the observational scales of the new facilities will push the techniques to their limits. Processes such as signal decorrelation varying antenna gain and instabilities in the primary beam will have a serious effect on some of the algorithms. In addition the sheer volume of data produced will render some techniques computationally and financially impossible.

  17. Galactic radio astronomy

    CERN Document Server

    Sofue, Yoshiaki

    2017-01-01

    This book is a concise primer on galactic radio astronomy for undergraduate and graduate students, and provides wide coverage of galactic astronomy and astrophysics such as the physics of interstellar matter and the dynamics and structure of the Milky Way Galaxy and galaxies. Radio astronomy and its technological development have led to significant progress in galactic astronomy and contributed to understanding interstellar matter and galactic structures. The book begins with the fundamental physics of radio-wave radiation, i.e., black body radiation, thermal emission, synchrotron radiation, and HI and molecular line emissions. The author then gives overviews of ingredients of galactic physics, including interstellar matter such as the neutral (HI), molecular hydrogen, and ionized gases, as well as magnetic fields in galaxies. In addition, more advanced topics relevant to the Galaxy and galaxies are also contained here: star formation, supernova remnants, the Galactic Center and black holes, galactic dynamics...

  18. A direct localization of a fast radio burst and its host.

    Science.gov (United States)

    Chatterjee, S; Law, C J; Wharton, R S; Burke-Spolaor, S; Hessels, J W T; Bower, G C; Cordes, J M; Tendulkar, S P; Bassa, C G; Demorest, P; Butler, B J; Seymour, A; Scholz, P; Abruzzo, M W; Bogdanov, S; Kaspi, V M; Keimpema, A; Lazio, T J W; Marcote, B; McLaughlin, M A; Paragi, Z; Ransom, S M; Rupen, M; Spitler, L G; van Langevelde, H J

    2017-01-04

    Fast radio bursts are astronomical radio flashes of unknown physical nature with durations of milliseconds. Their dispersive arrival times suggest an extragalactic origin and imply radio luminosities that are orders of magnitude larger than those of all known short-duration radio transients. So far all fast radio bursts have been detected with large single-dish telescopes with arcminute localizations, and attempts to identify their counterparts (source or host galaxy) have relied on the contemporaneous variability of field sources or the presence of peculiar field stars or galaxies. These attempts have not resulted in an unambiguous association with a host or multi-wavelength counterpart. Here we report the subarcsecond localization of the fast radio burst FRB 121102, the only known repeating burst source, using high-time-resolution radio interferometric observations that directly image the bursts. Our precise localization reveals that FRB 121102 originates within 100 milliarcseconds of a faint 180-microJansky persistent radio source with a continuum spectrum that is consistent with non-thermal emission, and a faint (twenty-fifth magnitude) optical counterpart. The flux density of the persistent radio source varies by around ten per cent on day timescales, and very long baseline radio interferometry yields an angular size of less than 1.7 milliarcseconds. Our observations are inconsistent with the fast radio burst having a Galactic origin or its source being located within a prominent star-forming galaxy. Instead, the source appears to be co-located with a low-luminosity active galactic nucleus or a previously unknown type of extragalactic source. Localization and identification of a host or counterpart has been essential to understanding the origins and physics of other kinds of transient events, including gamma-ray bursts and tidal disruption events. However, if other fast radio bursts have similarly faint radio and optical counterparts, our findings imply that

  19. Low frequency radio observations of five rich clusters of galaxies

    International Nuclear Information System (INIS)

    Hanisch, R.J.; Erickson, W.C.

    1980-01-01

    Observations have been made at 43.0 and 73.8 MHz of five rich x-ray emitting clusters of galaxies: Abell 399/401, Abell 426 (the Perseus cluster), Abell 1367, Abell 1656 (the Coma cluster), and the Virgo cluster. A fan beam synthesis system has been used to search for extended radio emission, i.e., radio halos, in these clusters. Radio halos were detected in the Coma and Virgo clusters. No evidence was found for the existence of 3C84B, the halo source previously thought to exist in the Perseus cluster. If halo sources exist in Abell 399/401 or Abell 1367, they must be quite weak at frequencies less than 100 MHz. The observed sizes of the extended sources in Coma and Virgo imply that the rate of particle propagation away from strong radio galaxies greatly exceeds the Alfven velocity and is probably independent of particle energy

  20. Radio Emission from Supernovae

    International Nuclear Information System (INIS)

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Williams, Christopher L.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-01-01

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  1. Radio emission from Jupiter

    International Nuclear Information System (INIS)

    Velusamy, T.

    1976-01-01

    The basic features of the different radio emissions from the planet Jupiter are reviewed. These radio emissions characterized into three types as thermal, decimetric and decametric, are discussed. The coherent emission mechanism for the origin of the decametric bursts and the acceleration mechanism for relativistic electrons in the decimetric radiation have not been properly understood. The emissions are much related to the magnetic field of Jupiter. The system III rotation period for Jupiter has been calculated as 092 55 m 29.74 S. (A.K.)

  2. ¿Radios Comunitarias?

    OpenAIRE

    José Ignacio López Vigil

    2015-01-01

    Varias han sido las denominaciones dadas a la radio cuando su proyecto está al servicio de la gente. Palabras apropiadas pero devaluadas al decir del autor, a las que ahora se suma otras radios ciudadanas. Ciudadana para relievarla como ejercicio de poder y espacio de verdadera participación de la gente en la vida de su nación. Ciudadanos son los que piensan con cabeza propia y pesan en la opinión pública. Presenta una sinopsis de la historia de éstas desde 1974. Señala que la competencia obl...

  3. Particle content, radio-galaxy morphology, and jet power: all radio-loud AGN are not equal

    Science.gov (United States)

    Croston, J. H.; Ineson, J.; Hardcastle, M. J.

    2018-05-01

    Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGNs) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally, we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of population-wide AGN impact require careful assessment of the contribution of different jet subclasses, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.

  4. Inhomogeneities and the Modeling of Radio Supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Björnsson, C.-I.; Keshavarzi, S. T., E-mail: bjornsson@astro.su.se [Department of Astronomy, AlbaNova University Center, Stockholm University, SE–106 91 Stockholm (Sweden)

    2017-05-20

    Observations of radio supernovae (SNe) often exhibit characteristics not readily accounted for by a homogeneous, spherically symmetric synchrotron model; e.g., flat-topped spectra/light curves. It is shown that many of these deviations from the standard model can be attributed to an inhomogeneous source structure. When inhomogeneities are present, the deduced radius of the source and, hence, the shock velocity, is sensitive to the details of the modeling. As the inhomogeneities are likely to result from the same mechanism that amplify the magnetic field, a comparison between observations and the detailed numerical simulations now under way may prove mutually beneficial. It is argued that the radio emission in Type Ib/c SNe has a small volume filling factor and comes from a narrow region associated with the forward shock, while the radio emission region in SN 1993J (Type IIb) is determined by the extent of the Rayleigh–Taylor instability emanating from the contact discontinuity. Attention is also drawn to the similarities between radio SNe and the structural properties of SN remnants.

  5. Spectrum management and radio resource management considering cognitive radio systems

    NARCIS (Netherlands)

    Haartsen, J.C.; Wieweg, Lasse; Huschke, Jörg

    2005-01-01

    International fora and some national administrations define a cognitive radio (CR) as a pioneering radio communication system that would be capable of altering and adapting its transmitter and receiver parameters based on communication and the exchange of information with related detectable radio

  6. Low-Frequency Radio Bursts and Space Weather

    Science.gov (United States)

    Gopalswamy, N.

    2016-01-01

    Low-frequency radio phenomena are due to the presence of nonthermal electrons in the interplanetary (IP) medium. Understanding these phenomena is important in characterizing the space environment near Earth and other destinations in the solar system. Substantial progress has been made in the past two decades, because of the continuous and uniform data sets available from space-based radio and white-light instrumentation. This paper highlights some recent results obtained on IP radio phenomena. In particular, the source of type IV radio bursts, the behavior of type III storms, shock propagation in the IP medium, and the solar-cycle variation of type II radio bursts are considered. All these phenomena are closely related to solar eruptions and active region evolution. The results presented were obtained by combining data from the Wind and SOHO missions.

  7. The Radio Synchrotron Background: Conference Summary and Report

    Science.gov (United States)

    Singal, J.; Haider, J.; Ajello, M.; Ballantyne, D. R.; Bunn, E.; Condon, J.; Dowell, J.; Fixsen, D.; Fornengo, N.; Harms, B.; Holder, G.; Jones, E.; Kellermann, K.; Kogut, A.; Linden, T.; Monsalve, R.; Mertsch, P.; Murphy, E.; Orlando, E.; Regis, M.; Scott, D.; Vernstrom, T.; Xu, L.

    2018-03-01

    We summarize the radio synchrotron background workshop that took place 2017 July 19–21 at the University of Richmond. This first scientific meeting dedicated to the topic was convened because current measurements of the diffuse radio monopole reveal a surface brightness that is several times higher than can be straightforwardly explained by known Galactic and extragalactic sources and processes, rendering it by far the least well understood photon background at present. It was the conclusion of a majority of the participants that the radio monopole level is at or near that reported by the ARCADE 2 experiment and inferred from several absolutely calibrated zero-level lower frequency radio measurements, and unanimously agreed that the production of this level of surface brightness, if confirmed, represents a major outstanding question in astrophysics. The workshop reached a consensus on the next priorities for investigations of the radio synchrotron background.

  8. Valuing commercial radio licences

    NARCIS (Netherlands)

    Kerste, M.; Poort, J.; van Eijk, N.

    2011-01-01

    Within the EU Regulatory Framework, licensees for commercial radio broadcasting may be charged a fee to ensure optimal allocation of scarce resources but not to maximize public revenues. In this paper, it is described how such a fee can be determined for the purpose of licence renewal or extension.

  9. Radio Frequency Identification

    Indian Academy of Sciences (India)

    Radio Frequency Identification (RFID) has been around sinceearly 2000. Its use has currently become commonplace as thecost of RFID tags has rapidly decreased. RFID tags have alsobecome more 'intelligent' with the incorporation of processorsand sensors in them. They are widely used now in manyinnovative ways.

  10. Nanolensed Fast Radio Bursts

    Science.gov (United States)

    Eichler, David

    2017-12-01

    It is suggested that fast radio bursts can probe gravitational lensing by clumpy dark matter objects that range in mass from 10-3 M ⊙-102 M ⊙. They may provide a more sensitive probe than observations of lensings of objects in the Magellanic Clouds, and could find or rule out clumpy dark matter with an extended mass spectrum.

  11. AMATEUR "HAM" RADIO

    Science.gov (United States)

    these cooler months. Did you know your body can cool 25 times faster in water than in air? That water code at 13 or 20 words-per-minute will no longer be required to obtain amateur radio operating be found by contacting the ARRL or using an Internet search engine to search on such topics as "

  12. Magnetar-like X-Ray Bursts Suppress Pulsar Radio Emission

    Energy Technology Data Exchange (ETDEWEB)

    Archibald, R. F.; Lyutikov, M.; Kaspi, V. M.; Tendulkar, S. P. [Department of Physics and McGill Space Institute, McGill University, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Burgay, M.; Possenti, A. [INAF–Osservatorio Astronomico di Cagliari, Via della Scienza 5, I-09047 Selargius (Italy); Esposito, P.; Rea, N. [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Postbus 94249, 1090 GE Amsterdam (Netherlands); Israel, G. [INAF–Osservatorio Astronomico di Roma, via Frascati 33, I-00040 Monteporzio Catone, Roma (Italy); Kerr, M. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Sarkissian, J. [CSIRO Astronomy and Space Science, Parkes Observatory, P.O. Box 276, Parkes, NSW 2870 (Australia); Scholz, P., E-mail: archibald@astro.utoronto.ca [National Research Council of Canada, Herzberg Astronomy and Astrophysics, Dominion Radio Astrophysical Observatory, P.O. Box 248, Penticton, BC V2A 6J9 (Canada)

    2017-11-10

    Rotation-powered pulsars and magnetars are two different observational manifestations of neutron stars: rotation-powered pulsars are rapidly spinning objects that are mostly observed as pulsating radio sources, while magnetars, neutron stars with the highest known magnetic fields, often emit short-duration X-ray bursts. Here, we report simultaneous observations of the high-magnetic-field radio pulsar PSR J1119−6127 at X-ray, with XMM-Newton and NuSTAR , and at radio energies with the Parkes radio telescope, during a period of magnetar-like bursts. The rotationally powered radio emission shuts off coincident with the occurrence of multiple X-ray bursts and recovers on a timescale of ∼70 s. These observations of related radio and X-ray phenomena further solidify the connection between radio pulsars and magnetars and suggest that the pair plasma produced in bursts can disrupt the acceleration mechanism of radio-emitting particles.

  13. Radio images of the planets

    International Nuclear Information System (INIS)

    De Pater, I.

    1990-01-01

    Observations at radio wavelengths make possible detailed studies of planetary atmospheres, magnetospheres, and surface layers. The paper addresses the question of what can be learned from interferometric radio images of planets. Results from single-element radio observations are also discussed. Observations of both the terrestrial and the giant planets are considered. 106 refs

  14. Discovery of large-scale diffuse radio emission in low-mass galaxy cluster Abell 1931

    Science.gov (United States)

    Brüggen, M.; Rafferty, D.; Bonafede, A.; van Weeren, R. J.; Shimwell, T.; Intema, H.; Röttgering, H.; Brunetti, G.; Di Gennaro, G.; Savini, F.; Wilber, A.; O'Sullivan, S.; Ensslin, T. A.; De Gasperin, F.; Hoeft, M.

    2018-04-01

    Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep spectrum radio source in the low-mass cluster Abell 1931. The source has a fairly irregular morphology with a largest linear size of about 550 kpc. The source is only seen in LOFAR observations at 143 MHz and GMRT observations at 325 MHz. The spectral index of the total source between 143 MHz and 325 MHz is α _{143}^{325} = -2.86 ± 0.36. The source remains invisible in Very Large Array (1-2 GHz) observations as expected given the spectral index. Chandra X-ray observations of the cluster revealed a bolometric luminosity of LX = (1.65 ± 0.39) × 1043 erg s-1 and a temperature of 2.92_{-0.87}^{+1.89} keV which implies a mass of around ˜1014M⊙. We conclude that the source is a remnant radio galaxy that has shut off around 200 Myr ago. The brightest cluster galaxy, a radio-loud elliptical galaxy, could be the source for this extinct source. Unlike remnant sources studied in the literature, our source has a steep spectrum at low radio frequencies. Studying such remnant radio galaxies at low radio frequencies is important for understanding the scarcity of such sources and their role in feedback processes.

  15. On the origin of the dust lane in the active radio galaxies

    International Nuclear Information System (INIS)

    Morita, Kazuhiko; Sakashita, Shiro

    1979-01-01

    A simple explosion model leading to the extragalactic extended radio sources is developed to understand the origin of the dust lane seen in the active radio galaxies. The point explosion in a spheroid with inhomogeneous density distribution is investigated by taking account of the cooling effect induced by radiative energy loss. It is suggested that the morphological relation between the dust lane and double radio sources is well explained on the basis of explosion model. (author)

  16. A transient, flat spectrum radio pulsar near the Galactic Centre

    Science.gov (United States)

    Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

    2017-06-01

    Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

  17. Optical emission line spectra of Seyfert galaxies and radio galaxies

    International Nuclear Information System (INIS)

    Osterbrock, D.E.

    1978-01-01

    Many radio galaxies have strong emission lines in their optical spectra, similar to the emission lines in the spectra of Seyfert galaxies. The range of ionization extends from [O I] and [N I] through [Ne V] and [Fe VII] to [Fe X]. The emission-line spectra of radio galaxies divide into two types, narrow-line radio galaxies whose spectra are indistinguishable from Seyfert 2 galaxies, and broad-line radio galaxies whose spectra are similar to Seyfert 1 galaxies. However on the average the broad-line radio galaxies have steeper Balmer decrements, stronger [O III] and weaker Fe II emission than the Seyfert 1 galaxies, though at least one Seyfert 1 galaxy not known to be a radio source has a spectrum very similar to typical broad-line radio galaxies. Intermediate-type Seyfert galaxies exist that show various mixtures of the Seyfert 1 and Seyfert 2 properties, and the narrow-line or Seyfert 2 property seems to be strongly correlated with radio emission. (Auth.)

  18. Extended radio emission and the nature of blazars

    International Nuclear Information System (INIS)

    Antonucci, R.R.J.; Ulvestad, J.S.

    1985-01-01

    The VLA has been used at 20 cm to map all 23 of the 54 confirmed blazars listed in the Angel and Stockman review paper that had not been mapped before at high resolution. (Blazars include BL Lac objects and optically violently variable quasars.) In addition, data on most of the previously mapped blazars have been reprocessed in order to achieve higher dynamic range. Extended emission has been detected associated with 49 of the 54 objects. The extended radio emission has been used to test the hypothesis that blazars are normal radio galaxies and radio quasars viewed along the jet axes. We find that blazars have substantial extended power, consistent with this hypothesis. Many have extended powers as high as the luminous Fanaroff-Riley class 2 radio doubles. The projected linear sizes are small, as expected from foreshortening of the extended sources, and many blazars have the expected core-halo morphology. There are also several small doubles, a head-tail source, and some one-sided sources, and these could be in cases where the line of sight is slightly off the jet axis, or projections of asymmetrical radio galaxies and quasars. The ratio of core to extended radio emission has been studied as a possible indicator of viewing aspect or beaming intensity. It is found to correlate with optical polarization, optical and radio core variability, and one-sided radio morphology. We can go beyond these consistency checks and work toward a proof of the hypothesis under discussion. The flux from the extended emission alone is sufficient in some blazars to qualify them for inclusion in the 3C and 4C catalogs. Suppose that the radio core emission is anisotropic, but the extended emission is predominantly isotropic. The isotropy of the extended emission implies that these blazars would be in the catalogs even if viewed from the side

  19. Introduction to international radio regulations

    Energy Technology Data Exchange (ETDEWEB)

    Radicella, S M [Abdus Salam International Centre for Theoretical Physics, Trieste (Italy)

    2003-12-15

    These lecture notes contain an overview of basic problems of the International Radio Regulations. Access to the existing information infrastructure, and to that of the future Information Society, depends critically on radio, especially in poor, remote and sparsely populated regions with under-developed telecommunication infrastructure. How the spectrum of radio frequencies is regulated has profound impact on the society, its security, prosperity, and culture. The radio regulations represent a very important framework for an adequate use of radio and should be known by all of those working in the field.

  20. Introduction to international radio regulations

    International Nuclear Information System (INIS)

    Radicella, S.M.

    2003-01-01

    These lecture notes contain an overview of basic problems of the International Radio Regulations. Access to the existing information infrastructure, and to that of the future Information Society, depends critically on radio, especially in poor, remote and sparsely populated regions with under-developed telecommunication infrastructure. How the spectrum of radio frequencies is regulated has profound impact on the society, its security, prosperity, and culture. The radio regulations represent a very important framework for an adequate use of radio and should be known by all of those working in the field

  1. Review of Radio Frequency Photonics Basics

    Science.gov (United States)

    2017-09-06

    AFRL-RY-WP-TR-2017-0157 REVIEW OF RADIO FREQUENCY PHOTONICS BASICS Preetpaul S. Devgan RF/EO Subsystems Branch Aerospace Components & Subsystems...Center (DTIC) (http://www.dtic.mil). AFRL-RY-WP-TR-2017-0157 HAS BEEN REVIEWED AND IS APPROVED FOR PUBLICATION IN ACCORDANCE WITH ASSIGNED...including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing

  2. Chautauqua notebook: appropriate technology on radio

    Energy Technology Data Exchange (ETDEWEB)

    Renz, B.

    1981-01-01

    Experiences in establishing and maintaining a regional call-in information-exchange radio show (Chautauqua) on energy conservation, appropriate technology, renewable energy sources, and self-reliance are discussed. Information is presented on: appropriate technology; the Chautauquaa concept; topics discussed; research performed; guests; interviewing tips; types of listeners; program features; where to find help; promotion and publicity; the technical and engineering aspects; the budget and funding; and station policies. (MCW)

  3. Innovations to enrich science communication through radio

    OpenAIRE

    Thakar Bhaumik; Kothari Abhay

    2004-01-01

    The Radio is an instrument of communication that has percolated to all the strata of the diverse Indian society. Its position has been consolidated through history as a regular companion and a source of information and entertainment. Its affordability, accessibility and non-reliance on costly resources have ensured its presence in almost all the households. It has become indispensable from kitchens, family rooms and even workspaces. It is one of the few or rather the only medium of communicat...

  4. Radio properties of central dominant galaxies in cluster cooling flows

    International Nuclear Information System (INIS)

    O'dea, C.P.; Baum, S.A.

    1986-01-01

    New VLA observations of central dominant (cd) galaxies currently thought to be in cluster cooling flows are combined with observations from the literature to examine the global properties of a heterogeneous sample of 31 cd galaxies. The radio sources tend to be of low or intermediate radio power and have small sizes (median extent about 25 kpc). The resolved sources tend to have distorted morphologies (e.g., wide-angle tails and S shapes). It is not yet clear whether the radio emission from these cd galaxies is significantly different from those not thought to be in cluster cooling flows. The result of Jones and Forman (1984), that there is a possible correlation between radio power and excess X-ray luminosity in the cluster center (above a King model fit to the X-ray surface brightness), is confirmed. 43 references

  5. Ionospheric wave and irregularity measurements using passive radio astronomy techniques

    International Nuclear Information System (INIS)

    Erickson, W.C.; Mahoney, M.J.; Jacobson, A.R.; Knowles, S.H.

    1988-01-01

    The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities. 10 references

  6. Method and apparatus for radio frequency ceramic sintering

    Science.gov (United States)

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  7. Radio-capacity of ecosystems

    International Nuclear Information System (INIS)

    Kultakhmedov, Yu.; Kultakhmedova-Vyshnyakova, V.

    1997-01-01

    This paper consider a universal approach to ecosystems of different types, based on representation of their radio-capacity. The concept of ecosystem includes reproduction of components (bio-productivity) and conditions such as maintaining of environment quality. Radio-capacity in the case of radionuclide pollution appears in accumulation and redistribution of radionuclides in the ecosystem. As a result the radionuclides are redistributed and buried in soil or lake bottom sediments. Estimation models for the radio-capacity of water and terrestrial ecosystems are represented. The calculations of the radio-capacity factor of water ecosystems are performed, and the high radio-capacity of a freshwater reservoir (F=0.6-0.8) and extremely high radio-capacity of a reservoir cascade (F c =0.99) is shown material from the Dnieper's cascade reservoirs. The methods of radio-capacity estimation of agroecosystems, wood and marine ecosystems are developed. (authors)

  8. The Concept of 'Radio Music'

    DEFF Research Database (Denmark)

    Fjeldsøe, Michael

    2016-01-01

    , educational and didactic effort which would enlighten all of society. For a while it seemed that radio music was considered a genre of its own. To fulfil its function, radio music had to consider technical limitations as well as the educational level and listening modes of the new mass audience. Public radio......, as discussed by Kurt Weill and Paul Hindemith, was at first greeted with great expectations, but soon a more realistic attitude prevailed. Weill, himself a radio critic as well, composed Der Lindberghflug (1929) as a piece of ‘radio music theatre’, but then changed some of its features in order to turn...... it into a didactical play for amateurs, a so-called Lehrstück. The article will present the concept of ‘radio music’ developed within German Neue Sachlichkeit and discuss the relevance of such a concept for current research in the field of radio and music....

  9. Tools of radio astronomy

    CERN Document Server

    Wilson, Thomas L; Hüttemeister, Susanne

    2009-01-01

    The recent years have seen breathtaking progress in technology, especially in the receiver and digital technologies relevant for radio astronomy, which has at the same time advanced to shorter wavelengths. This is the updated and completely revised 5th edition of the most used introductory text in radio astronomy. It presents a unified treatment of the entire field from centimeter to sub-millimeter wavelengths. Topics covered include instruments, sensitivity considerations, observational methods and interpretations of the data recorded with both single dishes and interferometers. This text is useful to both students and experienced practicing astronomers. Besides making major updates and additions throughout the book, the authors have re-organized a number of chapters to more clearly separate basic theory from rapidly evolving practical aspects. Further, problem sets have been added at the end of each chapter.

  10. Radio telescope control

    CERN Document Server

    Schraml, J

    1972-01-01

    An on-line computer control process developed for the 100-m radio telescope of the Max-Planck-Institut fur Radioastronomie in Bonn is described. The instrument is the largest fully steerable antenna in the world. Its operation started on May 31st 1972. It is controlled by a Ferranti Argus 500 on-line computer. The first part of the paper deals with the process itself, the radio telescope and its operation, and the demands resulting for the control program. The second part briefly describes the computer and its hardware. The final part introduces the architecture of the executive program in general, which has been tailored to meet the demands of the process and the hardware. The communication between the observer and the system, the format of data on magnetic tape and an on-line reduction of position measurements are considered. (0 refs).

  11. Die radio in Afrika

    Directory of Open Access Journals (Sweden)

    S. de Villiers

    1966-03-01

    Full Text Available Omvang van radio-uitsendings in en na Afrika. — Redes vir die versnelde tempo van uitbreiding. — Radio as die geskikste massa-kommunikasiemiddel vir Afrika. — Faktore wat die verspreiding bemoeilik. — Skouspelagtige toename in luistertalle.Toe Plinius, wat in die jaar 79 oorlede is, in sy „Historia Naturalis” verklaar het dat daar altyd iets nuuts uit Afrika afkomstig is, kon hy nouliks voorsien het dat die „iets" negentien eeue later in die lug sou setel wat hierdie reuse-vasteland oorspan — ’n Babelse spraakverwarring en ’n ongekende, verbete woorde-oorlog in die etergolwe, onder meer daarop bereken om die harte en hoofde van derduisendes te verower.

  12. Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

    Science.gov (United States)

    Mottez, F.; Zarka, P.

    2014-09-01

    Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims: We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods: The analysis is based on the theory of Alfvén wings: for a body immersed in a pulsar wind, a system of two stationary Alfvén waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfvén wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfvén wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results: Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥104), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. Conclusions: The search of pulsar-orbiting bodies could be an exploration

  13. Particle acceleration by Alfven wave turbulence in radio galaxies

    International Nuclear Information System (INIS)

    Eilek, J.A.

    1986-01-01

    Radio galaxies show evidence for acceleration of relativistic electrons locally within the diffuse radio luminous plasma. One likely candidate for the reacceleration mechanism is acceleration by magnetohydrodynamic turbulence which exists within the plasma. If Alfven waves are generated by a fluid turbulent cascade described by a power law energy-wavenumber spectrum, the particle spectrum in the presence of synchrotron losses will evolve towards an asymptotic power law which agrees with the particle spectra observed in these sources

  14. Classifying Radio Galaxies with the Convolutional Neural Network

    International Nuclear Information System (INIS)

    Aniyan, A. K.; Thorat, K.

    2017-01-01

    We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff–Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ∼200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

  15. Classifying Radio Galaxies with the Convolutional Neural Network

    Energy Technology Data Exchange (ETDEWEB)

    Aniyan, A. K.; Thorat, K. [Department of Physics and Electronics, Rhodes University, Grahamstown (South Africa)

    2017-06-01

    We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff–Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ∼200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

  16. Classifying Radio Galaxies with the Convolutional Neural Network

    Science.gov (United States)

    Aniyan, A. K.; Thorat, K.

    2017-06-01

    We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff-Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ˜200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

  17. NOAA Weather Radio

    Science.gov (United States)

    cosas afectan la recepción de señas de la radio. Por ejemplo, las extensiones grandes de agua de sal receptor con una antena interior de calidad buena, o conectarlo a una antena externa. Generalmente los Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing

  18. Radio Frequency Interference Mitigation

    Science.gov (United States)

    An, T.; Chen, X.; Mohan, P.; Lao, B. Q.

    2017-09-01

    The observational facilities of radio astronomy keep constant upgrades and developments to achieve better capabilities including increasing the time of the data recording and frequency resolutions, and increasing the receiving and recording bandwidth. However in contrast, only a limited spectrum resource has been allocated to radio astronomy by the International Telecommunication Union, resulting in that the radio observational instrumentations are inevitably exposed to undesirable radio frequency interference (RFI) signals which originate mainly from the terrestrial human activity and are becoming stronger with time. RFIs degrade the quality of data and even lead to invalid data. The impact of RFIs on scientific outcome becomes more and more serious. In this article, the requirement for RFI mitigation is motivated, and the RFI characteristics, mitigation techniques, and strategies are reviewed. The mitigation strategies adopted at some representative observatories, telescopes, and arrays are also introduced. The advantages and shortcomings of the four classes of RFI mitigation strategies are discussed and presented, applicable at the connected causal stages: preventive, pre-detection, pre-correlation, and post-correlation. The proper identification and flagging of RFI is the key to the reduction of data loss and improvement in data quality, and is also the ultimate goal of developing RFI mitigation technique. This can be achieved through a strategy involving a combination of the discussed techniques in stages. The recent advances in the high speed digital signal processing and high performance computing allow for performing RFI excision of the large data volumes generated from large telescopes or arrays in both real time and offline modes, aiding the proposed strategy.

  19. AIDS radio triggers.

    Science.gov (United States)

    Elias, A M

    1991-07-01

    In April 1991, the Ethnic Communities' Council of NSW was granted funding under the Community AIDS Prevention and Education Program through the Department of Community Services and Health, to produce a series of 6x50 second AIDS radio triggers with a 10-second tag line for further information. The triggers are designed to disseminate culturally-sensitive information about HIV/AIDS in English, Italian, Greek, Spanish, Khmer, Turkish, Macedonian, Serbo-Croatian, Arabic, Cantonese, and Vietnamese, with the goal of increasing awareness and decreasing the degree of misinformation about HIV/AIDS among people of non-English-speaking backgrounds through radio and sound. The 6 triggers cover the denial that AIDS exists in the community, beliefs that words and feelings do not protect one from catching HIV, encouraging friends to be compassionate, compassion within the family, AIDS information for a young audience, and the provision of accurate and honest information on HIV/AIDS. The triggers are slated to be completed by the end of July 1991 and will be broadcast on all possible community, ethnic, and commercial radio networks across Australia. They will be available upon request in composite form with an information kit for use by health care professionals and community workers.

  20. Radio observations of some clusters of galaxies at lambda=3.5 and 4 mm

    International Nuclear Information System (INIS)

    Efanov, V.A.; Zinchenko, I.I.; Kislyakov, A.G.; Krasil'nikov, A.A.; Kukina, E.P.; Moiseev, I.G.

    1980-01-01

    Millimeter radio observations with the 22-m Crimean antenna are reported for the central regions of the clusters of galaxies in Virgo, Hercules, and Coma Berenices, and from the cluster Abell 2199. In two of these, Coma and A2199, sources with a flux density of several jansky have been detected. The position of the source in A2199 matches that of the radio source 3C 338, but the object in the Coma cluster does not correspond to any known radio source. The nature of the emission from the new sources is discussed