WorldWideScience

Sample records for faint evolving radio

  1. 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.

  2. EoR Foregrounds: the Faint Extragalactic Radio Sky

    Science.gov (United States)

    Prandoni, Isabella

    2018-05-01

    A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and μJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population and on the modeling of its various components. In this paper I will provide a brief overview of the latest results in areas that are potentially important for an accurate treatment of extra-galactic foregrounds in experiments designed to probe the Epoch of Reionization.

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Identification and spectrophotometry of faint southern radio galaxies

    International Nuclear Information System (INIS)

    Spinrad, H.; Kron, R.G.; Hunstead, R.W.

    1980-01-01

    We have observed a mixed sample of southern radio sources, identified on the Palomar sky survey or on previous direct plates taken with medium-aperture reflectors. At CIO we obtained a few deep 4m photographs and SIT spectrophotometry for redshift and continuum-color measurement. Almost all our sources were faint galaxies; the largest redshift measured was for 3C 275, with z=0.480. The ultraviolet continuum of PKS 0400--643, a ''thermal'' galaxy with z=0.476, closely resembles that of 3C 295 and shows some color evolution in U--B compared to nearby giant ellipticals

  16. 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).

  17. 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.

  18. 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.

  19. 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.

  20. Radio and infrared observations of the faint nebula GM24

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, L F; Roth, M; Tapia, M; Canto, J; Persi, P; Ferrari-Toniolo, M

    1986-02-01

    The faint nebulosity GM24=PP85 listed by Parsamian and Petrosian (1979) was observed at infrared (1-10 ..mu..m) and radio (6 cm and CO line) wavelengths in the vicinity of the CO hot spot reported by Torrelles et al. (1983). The radio continuum (6 cm) emission from a spherically symmetrical HII region was detected with the Very Large Array. Its position coincides with the brightest part of the visible nebulosity and a 1-4 ..mu..m emission peak. Their infrared maps made at the Observatorio Astronomico Nacional de San Pedro Martir, show two additional (1-10 ..mu..m) peaks located at distances approx. 30 arc sec from the compact HII region, all surrounded by extended near infrared (1-4 ..mu..m) emission. A detailed CO (J=1 ..-->.. 0) map of the whole molecular cloud was also obtained with the University of Texas Millimeter - Wave Telescope. Their results are interpreted in terms of the recent formation of three massive stars, one of which, having developed an HII region, is at a slightly later phase of its evolution. The extended near infrared emission may arise in a reflection nebula similar to NGC 7538-Irs 9. 4 references.

  1. 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).

  2. 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.

  3. Radio Imaging of Envelopes of Evolved Stars

    Science.gov (United States)

    Cotton, Bill

    2018-04-01

    This talk will cover imaging of stellar envelopes using radio VLBI techniques; special attention will be paid to the technical differences between radio and optical/IR interferomery. Radio heterodyne receivers allow a straightforward way to derive spectral cubes and full polarization observations. Milliarcsecond resolution of very bright, i.e. non thermal, emission of molecular masers in the envelopes of evolved stars can be achieved using VLBI techniques with baselines of thousands of km. Emission from SiO, H2O and OH masers are commonly seen at increasing distance from the photosphere. The very narrow maser lines allow accurate measurements of the velocity field within the emitting region.

  4. 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.

  5. A search for radio emission from exoplanets around evolved stars

    Science.gov (United States)

    O'Gorman, E.; Coughlan, C. P.; Vlemmings, W.; Varenius, E.; Sirothia, S.; Ray, T. P.; Olofsson, H.

    2018-04-01

    The majority of searches for radio emission from exoplanets have to date focused on short period planets, i.e., the so-called hot Jupiter type planets. However, these planets are likely to be tidally locked to their host stars and may not generate sufficiently strong magnetic fields to emit electron cyclotron maser emission at the low frequencies used in observations (typically ≥150 MHz). In comparison, the large mass-loss rates of evolved stars could enable exoplanets at larger orbital distances to emit detectable radio emission. Here, we first show that the large ionized mass-loss rates of certain evolved stars relative to the solar value could make them detectable with the LOw Frequency ARray (LOFAR) at 150 MHz (λ = 2 m), provided they have surface magnetic field strengths >50 G. We then report radio observations of three long period (>1 au) planets that orbit the evolved stars β Gem, ι Dra, and β UMi using LOFAR at 150 MHz. We do not detect radio emission from any system but place tight 3σ upper limits of 0.98, 0.87, and 0.57 mJy on the flux density at 150 MHz for β Gem, ι Dra, and β UMi, respectively. Despite our non-detections these stringent upper limits highlight the potential of LOFAR as a tool to search for exoplanetary radio emission at meter wavelengths.

  6. X- and γ-ray pulsations of the nearby radio-faint PSR J1741–2054

    Energy Technology Data Exchange (ETDEWEB)

    Marelli, M.; Belfiore, A.; Caraveo, P.; De Luca, A.; Salvetti, D. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, I-20133 Milano (Italy); Saz Parkinson, P. [Santa Cruz Institute for Particle Physics, University of California, Santa Cruz, CA 95064 (United States); Sarazin, C.; Sivakoff, G. R. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States); Camilo, F., E-mail: marelli@lambrate.inaf.it [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States)

    2014-07-20

    We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741–2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. The nebular emission is consistent with that of a synchrotron pulsar wind nebula, with hints of spatial spectral variation. We extended the available Fermi LAT ephemeris and folded the γ-ray and X-ray data. We detected X-ray pulsations from the neutron star: both the thermal and non-thermal components are ∼35%-40% pulsed, with phase-aligned maxima. A sinusoid fits the thermal-folded profile well. A 10 bin phase-resolved analysis of the X-ray emission shows softening of the non-thermal spectrum during the on-pulse phases. The radio, X-ray, and γ-ray light curves are single-peaked, not phase-aligned, with the X-ray peak trailing the γ-ray peak by more than half a rotation. Spectral considerations suggest that the most probable pulsar distance is in the 0.3-1.0 kpc range, in agreement with the radio dispersion measure.

  7. X- and γ-ray pulsations of the nearby radio-faint PSR J1741–2054

    International Nuclear Information System (INIS)

    Marelli, M.; Belfiore, A.; Caraveo, P.; De Luca, A.; Salvetti, D.; Saz Parkinson, P.; Sarazin, C.; Sivakoff, G. R.; Camilo, F.

    2014-01-01

    We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741–2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. The nebular emission is consistent with that of a synchrotron pulsar wind nebula, with hints of spatial spectral variation. We extended the available Fermi LAT ephemeris and folded the γ-ray and X-ray data. We detected X-ray pulsations from the neutron star: both the thermal and non-thermal components are ∼35%-40% pulsed, with phase-aligned maxima. A sinusoid fits the thermal-folded profile well. A 10 bin phase-resolved analysis of the X-ray emission shows softening of the non-thermal spectrum during the on-pulse phases. The radio, X-ray, and γ-ray light curves are single-peaked, not phase-aligned, with the X-ray peak trailing the γ-ray peak by more than half a rotation. Spectral considerations suggest that the most probable pulsar distance is in the 0.3-1.0 kpc range, in agreement with the radio dispersion measure.

  8. Optical and near-infrared imaging of faint Gigahertz Peaked Spectrum sources

    NARCIS (Netherlands)

    Snellen, IAG; Schilizzi, RT; de Bruyn, AG; Miley, GK; Rottgering, HJA; McMahon, RG; Fournon, IP

    1998-01-01

    A sample of 47 faint Gigahertz Peaked Spectrum (GPS) radio sources selected from the Westerbork Northern Sky Survey (WENSS) has been imaged in the optical and near-infrared, resulting in an identification fraction of 87 per cent. The R - I and R - K colours of the faint optical counterparts are as

  9. 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.

  10. Measuring size evolution of distant, faint galaxies in the radio regime

    Science.gov (United States)

    Lindroos, L.; Knudsen, K. K.; Stanley, F.; Muxlow, T. W. B.; Beswick, R. J.; Conway, J.; Radcliffe, J. F.; Wrigley, N.

    2018-05-01

    We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of ˜1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses M⊙ ≈ 1010-1011 M⊙ and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M* = 5 × 1010 M⊙ as R_e = A× {}(H(z)/H(1.5))^{α _z}. We find that the median radio sizes evolve towards larger sizes at later times with αz = -1.1 ± 0.6, and A (the median size at z ≈ 1.5) is found to be 0.26^'' ± 0.07^'' or 2.3±0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H α sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.

  11. 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

  12. Fainting

    Science.gov (United States)

    ... a medicine you’re taking. Alcohol, cocaine, and marijuana can also cause fainting. More serious causes of fainting include seizures and problems with the heart or with the blood vessels leading to the brain. How is fainting diagnosed? Your doctor will probably ...

  13. The search for faint radio supernova remnants in the outer Galaxy: five new discoveries

    Science.gov (United States)

    Gerbrandt, Stephanie; Foster, Tyler J.; Kothes, Roland; Geisbüsch, Jörn; Tung, Albert

    2014-06-01

    Context. High resolution and sensitivity large-scale radio surveys of the Milky Way are critical in the discovery of very low surface brightness supernova remnants (SNRs), which may constitute a significant portion of the Galactic SNRs still unaccounted for (ostensibly the "missing SNR problem"). Aims: The overall purpose here is to present the results of a systematic, deep data-mining of the Canadian Galactic plane Survey (CGPS) for faint, extended non-thermal and polarized emission structures that are likely the shells of uncatalogued SNRs. Methods: We examine 5 × 5 degree mosaics from the entire 1420 MHz continuum and polarization dataset of the CGPS after removing unresolved "point" sources and subsequently smoothing them. Newly revealed extended emission objects are compared to similarly prepared CGPS 408 MHz continuum mosaics, as well as to source-removed mosaics from various existing radio surveys at 4.8 GHz, 2.7 GHz, and 327 MHz, to identify candidates with non-thermal emission characteristics. We integrate flux densities at each frequency to characterise the radio spectra behaviour of these candidates. We further look for mid- and high-frequency (1420 MHz, 4.8 GHz) ordered polarized emission from the limb brightened "shell"-like continuum features that the candidates sport. Finally, we use IR and optical maps to provide additional backing evidence. Results: Here we present evidence that five new objects, identified as filling all or some of the criteria above, are strong candidates for new SNRs. These five are designated by their Galactic coordinate names G108.5+11.0, G128.5+2.6, G149.5+3.2, G150.8+3.8, and G160.1-1.1. The radio spectrum of each is presented, highlighting their steepness, which is characteristic of synchrotron radiation. CGPS 1420 MHz polarization data and 4.8 GHz polarization data also provide evidence that these objects are newly discovered SNRs. These discoveries represent a significant increase in the number of SNRs known in the outer

  14. 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.

  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. 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.

  17. MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

    International Nuclear Information System (INIS)

    Yi, Shuang-Xi; Gao, He; Zhang, Bing

    2014-01-01

    The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array

  18. 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.

  19. 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

  20. Star formation rate and extinction in faint z ∼ 4 Lyman break galaxies

    Energy Technology Data Exchange (ETDEWEB)

    To, Chun-Hao; Wang, Wei-Hao [Institute of Astronomy and Astrophysics, Academia Sinica, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan (China); Owen, Frazer N. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States)

    2014-09-10

    We present a statistical detection of 1.5 GHz radio continuum emission from a sample of faint z ∼ 4 Lyman break galaxies (LBGs). To constrain their extinction and intrinsic star formation rate (SFR), we combine the latest ultradeep Very Large Array 1.5 GHz radio image and the Hubble Space Telescope Advanced Camera for Surveys (ACS) optical images in the GOODS-N. We select a large sample of 1771 z ∼ 4 LBGs from the ACS catalog using B {sub F435W}-dropout color criteria. Our LBG samples have I {sub F775W} ∼ 25-28 (AB), ∼0-3 mag fainter than M{sub UV}{sup ⋆} at z ∼ 4. In our stacked radio images, we find the LBGs to be point-like under our 2'' angular resolution. We measure their mean 1.5 GHz flux by stacking the measurements on the individual objects. We achieve a statistical detection of S {sub 1.5} {sub GHz} = 0.210 ± 0.075 μJy at ∼3σ for the first time on such a faint LBG population at z ∼ 4. The measurement takes into account the effects of source size and blending of multiple objects. The detection is visually confirmed by stacking the radio images of the LBGs, and the uncertainty is quantified with Monte Carlo simulations on the radio image. The stacked radio flux corresponds to an obscured SFR of 16.0 ± 5.7 M {sub ☉} yr{sup –1}, and implies a rest-frame UV extinction correction factor of 3.8. This extinction correction is in excellent agreement with that derived from the observed UV continuum spectral slope, using the local calibration of Meurer et al. This result supports the use of the local calibration on high-redshift LBGs to derive the extinction correction and SFR, and also disfavors a steep reddening curve such as that of the Small Magellanic Cloud.

  1. Automated Morphological Classification in Deep Hubble Space Telescope UBVI Fields: Rapidly and Passively Evolving Faint Galaxy Populations

    Science.gov (United States)

    Odewahn, Stephen C.; Windhorst, Rogier A.; Driver, Simon P.; Keel, William C.

    1996-11-01

    We analyze deep Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) images in U, B, V, I using artificial neural network (ANN) classifiers, which are based on galaxy surface brightness and light profile (but not on color nor on scale length, rhl). The ANN distinguishes quite well between E/S0, Sabc, and Sd/Irr+M galaxies (M for merging systems) for BJ ~ 24 mag. The faint blue galaxy counts in the B band are dominated by Sd/Irr+M galaxies and can be explained by a moderately steep local luminosity function (LF) undergoing strong luminosity evolution. We suggest that these faint late-type objects (24 mag <~ BJ <~ 28 mag) are a combination of low-luminosity lower redshift dwarf galaxies, plus compact star-forming galaxies and merging systems at z ~= 1--3, possibly the building blocks of the luminous early-type galaxies seen today.

  2. 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)

  3. Fainting

    Science.gov (United States)

    ... go to the ER. When Desiree asked her school nurse about it the next day, she said Desiree probably fainted because she stayed in the whirlpool too long or the temperature was set too high, affecting her blood pressure. ...

  4. Studies of faint field galaxies

    International Nuclear Information System (INIS)

    Ellis, R.S.

    1983-01-01

    Although claims are often made that photometric surveys of faint field galaxies reveal evidence for evolution over recent epochs (z<0.6), it has not yet been possible to select a single evolutionary model from comparisons with the data. Magnitude counts are sensitive to evolution but the data is well-mixed in distance because of the width of the luminosity function (LF). Colours can narrow the possibilities but the effects of redshift and morphology can only be separated using many passbands. In this paper, the author highlights two ways in which one can make further progress in this important subject. First, he discusses results based on the AAT redshift survey which comprises 5 Schmidt fields to J = 16.7 i.e. well beyond local inhomogeneities. Secondly, the difficulties in resolving the many possibilities encountered with faint photometry could be resolved with redshifts. To obtain redshift distributions for faint samples is now feasible via multi-object spectroscopy. At intermediate magnitudes (J=20) such distributions test the faint end of the galaxy LF; at faint magnitudes (J=22) they offer a direct evolutionary test. (Auth.)

  5. 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.

  6. 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

  7. 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.

  8. Syncope (Fainting)

    Science.gov (United States)

    ... for Heart.org CPR & ECC for Heart.org Shop for Heart.org Causes for Heart.org Advocate ... loss of consciousness usually related to insufficient blood flow to the brain. It’s also called fainting or " ...

  9. The Faint End of the Lyman Alpha Luminosity Function at 2 < z < 3.8

    Science.gov (United States)

    Devarakonda, Yaswant; Livermore, Rachael; Indahl, Briana; Wold, Isak; Davis, Dustin; Finkelstein, Steven

    2018-01-01

    Most current models predict that our universe is mostly composed of small, dim galaxies. Due to these galaxies being so faint, it is very difficult to study these types of galaxies outside of our local universe. This is particularly an issue for studying how these small galaxies evolved over their lifetimes. With the benefit of gravitational lensing, however, we are able to observe galaxies that are farther and fainter than ever before possible. In this particular study, we focus on Lyman-Alpha emitting galaxies between the redshifts of 2-3.8, so that we may study these galaxies during the epoch of peak star formation in the universe. We use the McDonald Observatory 2.7, Harlan Smith telescope with the VIRUS-P IFU spectrograph to observe several Hubble Frontier Field lensing clusters to spectroscopically discover faint galaxies over this redshift range. In addition to providing insight into the faint-end slope of the Lyman alpha luminosity function, the spectroscopic redshifts will allow us to better constrain the mass models of the foreground clusters, such as Abell 370, so that we may better understand lensing effects for this and future studies.

  10. 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.

  11. Investigation of Inter-Node B Macro Diversity for Single-Carrier Based Radio Access in Evolved UTRA Uplink

    Science.gov (United States)

    Kawai, Hiroyuki; Morimoto, Akihito; Higuchi, Kenichi; Sawahashi, Mamoru

    This paper investigates the gain of inter-Node B macro diversity for a scheduled-based shared channel using single-carrier FDMA radio access in the Evolved UTRA (UMTS Terrestrial Radio Access) uplink based on system-level simulations. More specifically, we clarify the gain of inter-Node B soft handover (SHO) with selection combining at the radio frame length level (=10msec) compared to that for hard handover (HHO) for a scheduled-based shared data channel, considering the gains of key packet-specific techniques including channel-dependent scheduling, adaptive modulation and coding (AMC), hybrid automatic repeat request (ARQ) with packet combining, and slow transmission power control (TPC). Simulation results show that the inter-Node B SHO increases the user throughput at the cell edge by approximately 10% for a short cell radius such as 100-300m due to the diversity gain from a sudden change in other-cell interference, which is a feature specific to full scheduled-based packet access. However, it is also shown that the gain of inter-Node B SHO compared to that for HHO is small in a macrocell environment when the cell radius is longer than approximately 500m due to the gains from hybrid ARQ with packet combining, slow TPC, and proportional fairness based channel-dependent scheduling.

  12. 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

  13. Optical and radio counterpart of Circinus X-1 (3U 1516-56)

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, J A.J.; Murdin, P G; Peterson, B A [Anglo-Australian Observatory, Epping (Australia); and others

    1977-11-01

    Circinus X-1 (3U 1516-56) has a radio counterpart which, at high frequencies, show flares with the same 16.6 day periodicity as the X-ray intensity. In each cycle the radio flare occurs shortly after the intensity drop-off which defines the X-ray modulation. The radio source is positionally coincident with a faint red star having very strong H..cap alpha.. and weak He I emission lines which are probably variable. The object may be an early-type emission-line star or a symbiotic star, at a distance of 10 kpc.

  14. 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).

  15. Radio continuum observations of NML Cygni

    International Nuclear Information System (INIS)

    Gregory, P.C.; Seaquist, E.R.

    1976-01-01

    An attempt to detect thermal radio emission from a compact circumstellar cloud about the infrared star NML Cyg has been carried out at three frequencies, 2.7, 8.1, and 10.5 GHz. Although positive results were obtained with single-dish observations at 10.5 GHz, the radio emission is not from a circumstellar cloud about NML Cyg. Instead it is postulated that the emission is from an H ii region with an angular extent of approx.2'. The red print of the Sky Survey shows a faint nebulosity of comparable angular size overlapping the star's position, lending support to this interpretation. The interferometer observations at 2.7 and 8.1 GHz provide an upper limit on the radio emission from any compact circumstellar cloud about NML Cyg of 2.8 mJy, which is well below the flux density expected for the absorbing cloud postulated by Davies et al. (1972)

  16. Morphological Evolution in High-Redshift Radio Galaxies and the Formation of Giant Elliptical Galaxies

    International Nuclear Information System (INIS)

    Breugel, W.J. van; Stanford, S.A.; Spinrad, H.; Stern, D.; Graham, J.R.

    1998-01-01

    We present deep near-infrared images of high-redshift radio galaxies (HzRGs) obtained with the near-infrared camera (NIRC) on the Keck I telescope. In most cases, the near-IR data sample rest wavelengths that are free of contamination from strong emission lines and at λ rest > 4000 Angstrom, where older stellar populations, if present, might dominate the observed flux. At z > 3, the rest-frame optical morphologies generally have faint, large-scale (∼50 kpc) emission surrounding multiple, ∼10 kpc components. The brightest of these components are often aligned with the radio structures. These morphologies change dramatically at 2 rest ) ∼ -20 to -22] of the individual components in the z > 3 HzRGs are similar to the total sizes and luminosities of normal radio-quiet star forming galaxies at z = 3 - 4. For objects where such data are available, our observations show that the line-free, near-IR colors of the z > 3 galaxies are very blue, consistent with models in which recent star formation dominates the observed light. Direct spectroscopic evidence for massive star formation in one of the z > 3 HzRGs exists (4C 41.17). Our results suggest that the z > 3 HzRGs evolve into much more massive systems than the radio-quiet galaxies and that they are qualitatively consistent with models in which massive galaxies form in hierarchical fashion through the merging of smaller star-forming systems. The presence of relatively luminous subcomponents along the radio axes of the z > 3 galaxies suggests a causal connection with the AGN. We compare the radio and near-IR sizes as a function of redshift and suggest that this parameter may be a measure of the degree to which the radio sources have induced star formation in the parent objects. We also discuss the Hubble diagram of radio galaxies, the possibility of a radio power dependence in the K-z relation, and its implications for radio galaxy formation. Finally, we present for the first time in published format basic radio and

  17. 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.

  18. 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

  19. FAST RADIO BURSTS: COLLISIONS BETWEEN NEUTRON STARS AND ASTEROIDS/COMETS

    Energy Technology Data Exchange (ETDEWEB)

    Geng, J. J.; Huang, Y. F., E-mail: hyf@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210046 (China)

    2015-08-10

    Fast radio bursts (FRBs) are newly discovered radio transient sources. Their high dispersion measures indicate an extragalactic origin. However, due to the lack of observational data in other wavelengths, their progenitors still remain unclear. Here we suggest that the collisions between neutron stars (NSs) and asteroids/comets are promising mechanisms for FRBs. During the impact process, a hot plasma fireball forms after the material of the small body penetrates into the NS surface. The ionized matter inside the fireball then expands along the magnetic field lines. Coherent radiation from the thin shell at the top of the fireball will account for the observed FRBs. Our scenario can reasonably explain the main features of FRBs, such as their durations, luminosities, and the event rate. We argue that for a single NS, FRBs are not likely to happen repeatedly in a forseeable timespan since such impacts are of low probability. We predict that faint remnant X-ray emissions should be associated with FRBs, but it may be too faint to be detected by detectors at work.

  20. FAST RADIO BURSTS: COLLISIONS BETWEEN NEUTRON STARS AND ASTEROIDS/COMETS

    International Nuclear Information System (INIS)

    Geng, J. J.; Huang, Y. F.

    2015-01-01

    Fast radio bursts (FRBs) are newly discovered radio transient sources. Their high dispersion measures indicate an extragalactic origin. However, due to the lack of observational data in other wavelengths, their progenitors still remain unclear. Here we suggest that the collisions between neutron stars (NSs) and asteroids/comets are promising mechanisms for FRBs. During the impact process, a hot plasma fireball forms after the material of the small body penetrates into the NS surface. The ionized matter inside the fireball then expands along the magnetic field lines. Coherent radiation from the thin shell at the top of the fireball will account for the observed FRBs. Our scenario can reasonably explain the main features of FRBs, such as their durations, luminosities, and the event rate. We argue that for a single NS, FRBs are not likely to happen repeatedly in a forseeable timespan since such impacts are of low probability. We predict that faint remnant X-ray emissions should be associated with FRBs, but it may be too faint to be detected by detectors at work

  1. 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.

  2. THE RADIO AND OPTICAL LUMINOSITY EVOLUTION OF QUASARS. II. THE SDSS SAMPLE

    International Nuclear Information System (INIS)

    Singal, J.; Petrosian, V.; Stawarz, Ł.; Lawrence, A.

    2013-01-01

    We determine the radio and optical luminosity evolutions and the true distribution of the radio-loudness parameter R, defined as the ratio of the radio to optical luminosity, for a set of more than 5000 quasars combining Sloan Digital Sky Survey optical and Faint Images of the Radio Sky at Twenty cm (FIRST) radio data. We apply the method of Efron and Petrosian to access the intrinsic distribution parameters, taking into account the truncations and correlations inherent in the data. We find that the population exhibits strong positive evolution with redshift in both wavebands, with somewhat greater radio evolution than optical. With the luminosity evolutions accounted for, we determine the density evolutions and local radio and optical luminosity functions. The intrinsic distribution of the radio-loudness parameter R is found to be quite different from the observed one and is smooth with no evidence of a bimodality in radio loudness for log R ≥ –1. The results we find are in general agreement with the previous analysis of Singal et al., which used POSS-I optical and FIRST radio data.

  3. Origin of faint blue stars

    International Nuclear Information System (INIS)

    Tutukov, A.; Iungelson, L.

    1987-01-01

    The origin of field faint blue stars that are placed in the HR diagram to the left of the main sequence is discussed. These include degenerate dwarfs and O and B subdwarfs. Degenerate dwarfs belong to two main populations with helium and carbon-oxygen cores. The majority of the hot subdwarfs most possibly are helium nondegenerate stars that are produced by mass exchange close binaries of moderate mass cores (3-15 solar masses). The theoretical estimates of the numbers of faint blue stars of different types brighter than certain stellar magnitudes agree with star counts based on the Palomar Green Survey. 28 references

  4. Discovery of a radio nebula around PSR J0855-4644

    Science.gov (United States)

    Maitra, C.; Roy, S.; Acero, F.; Gupta, Y.

    2018-03-01

    We report the discovery of a diffuse radio emission around PSR J0855-4644 using an upgraded GMRT (uGMRT) observation at 1.35 GHz. The radio emission is spatially coincident with the diffuse X-ray pulsar wind nebula (PWN) seen with XMM-Newton but is much larger in extent compared to the compact axisymmetric PWN seen with Chandra. The morphology of the emission, with a bright partial ring-like structure and two faint tail-like features strongly resembles a bow shock nebula, and indicates a velocity of 100 km/s through the ambient medium. We conclude that the emission is most likely to be associated with the radio PWN of PSR J0855-4644. From the integrated flux density, we estimate the energetics of the PWN.

  5. Infrared and radio emission from S0 galaxies

    International Nuclear Information System (INIS)

    Bally, J.; Thronson, H.A. Jr.

    1989-01-01

    Far-IR data are presented on 74 early-type S0 galaxies that were selected on the basis of the availability of radio-continuum measurements. Most of the galaxies are detected at IR wavelengths with IRAS, indicating the presence of a cold interstellar medium (ISM) in these galaxies. The mass of gas in these systems is estimated to lie in the range of 10 to the 7th to 10 to the 10th solar. The most massive ISM in some S0s approaches that found in some spirals. The brighter IR-emitting galaxies all lie close to a relationship established for gas-rich spiral galaxies. None of these galaxies have large ratio fluxes, suggesting that strong nuclear radio sources or extended radio lobes and jets are absent or suppressed. Strong radio emission is found among those galaxies that are either faint or not detected at IR wavelengths. The absence of an ISM suggests that these galaxies are of an earlier type that those that have large IR fluxes. 38 references

  6. Faint Traces

    OpenAIRE

    Denyer, Frank

    2005-01-01

    CD of six compositions by Denyer played by The Barton Workshop (Amsterdam): ‘Out of the Shattered Shadows 1’; ‘Out of the Shattered Shadows 2’; ‘Faint Traces’; ‘Music for Two Performers’; ‘Play’; ‘Passages’. Liner notes by Bob Gilmore. \\ud \\ud Like ‘Fired City’ (2002), this is a portrait CD and comprises première recordings of six works. The three longest – one of which is the title track (2001) – are the most recent. All six works continue Denyer’s research into new acoustic instrumental sou...

  7. Photometry of faint blue stars

    International Nuclear Information System (INIS)

    Kilkenny, D.; Hill, P.W.; Brown, A.

    1977-01-01

    Photometry on the uvby system is given for 61 faint blue stars. The stars are classified by means of the Stromgren indices, using criteria described in a previous paper (Kilkenny and Hill (1975)). (author)

  8. 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

  9. 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.

  10. 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

  11. Global spiral structure of M81 - radio continuum maps

    International Nuclear Information System (INIS)

    Bash, F.N.; Kaufman, M.; Ohio State Univ., Columbus)

    1986-01-01

    VLA observations of the radio continuum emission from M81 at 6 and 20 cm are presented and used to check the predictions of density-wave theories. Both thermal and nonthermal radiation from the spiral arms are detected. Most of the bright knots along the radio arms are giant radio H II regions. The nonthermal emission defines spiral arms that are patchy and well-resolved, with a width of 1-2 kpc. The observed nonthermal arms are too broad to agree with the continuum gasdynamical calculations of Roberts (1969), Shu et al. (1972), and Visser (1978, 1980) for a classical density wave model. The observed arm widths appear consistent with the predictions of density-wave models that emphasize the clumpy nature of the ISM. The 20 cm arms appear to spiral outward from a faint inner H I ring, suggesting that the ring is produced by the inner Lindblad resonance. 36 references

  12. Radio and optical observations of 0218+357 - The smallest Einstein ring?

    Science.gov (United States)

    O'Dea, Christopher P.; Baum, Stefi A.; Stanghellini, Carlo; Dey, Arjun; Van Breugel, Wil; Deustua, Susana; Smith, Eric P.

    1992-01-01

    VLA radio observations and optical imaging and spectroscopy of the Einstein radio ring 0218+357 are presented. The ring is detected at 22.4 GHz and shows a basically similar structure at 5, 15, and 22.4 GHz. The B component has varied and was about 15 percent brighter in the 8.4 GHz data than in the data of Patnaik et al. (1992). The ring is highly polarized. A weak jetlike feature extending out roughly 2 arcsec to the southeast of component A is detected at 6 cm. The source has amorphous radio structure extending out to about 11 arcsec from the core. For an adopted redshift of 0.68, the extended radio emission is very powerful. The optical spectrum is rather red and shows no strong features. A redshift of about 0.68 is obtained. The identification is a faint compact m(r) about 20 galaxy which extends to about 4.5 arcsec (about 27 kpc). As much as 50 percent of the total light may be due to a central AGN. The observed double core and ring may be produced by an off-center radio core with extended radio structure.

  13. 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)

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. A Search for Millisecond-pulsar Radio Emission from the Faint Quiescent Soft X-Ray Transient 1H 1905+000

    Energy Technology Data Exchange (ETDEWEB)

    Mikhailov, K.; Van Leeuwen, J. [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, P.O. Box 94249, 1090 GE Amsterdam (Netherlands); Jonker, P. G., E-mail: K.Mikhailov@uva.nl [SRON, the Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA, Utrecht (Netherlands)

    2017-05-01

    Transitional millisecond pulsars (tMSPs) switch between an accretion-powered state without radio pulsations and a rotation-powered state with radio pulsations. In the former state, tMSPs are X-ray bright, while in the latter state, they are X-ray dim. Soft X-ray transients (SXTs) undergo similar switches in X-ray, between “high” states with bright X-ray outbursts and “low” states of quiescence. The upper limit on the quiescent X-ray luminosity of SXT 1H 1905+000 suggests that its luminosity might be similar to that of the known tMSPs. A detection of radio pulsations would link SXTs more strongly with tMSPs; and thus, e.g., put stricter constraints on tMSP transitional timescales through the connection with the well-known SXT periods of quiescence. A nondetection allows us, based on the telescope sensitivity, to estimate how likely these sources are to pulsate in radio. Over a 10-year span, 2006–2015, we carried out targeted radio observations at 400/800 MHz with Arecibo, and searched for radio pulsations from the quiescent SXT 1H 1905+000. None of the observations have revealed radio pulsations from the targeted SXT. For a 1 ms pulsar, our flux density upper limit is 10.3 μ Jy. At an assumed distance of 10 kpc this translates to a pseudo-luminosity upper limit of 1.0 mJy kpc{sup 2}, which makes our search complete to ∼85% of the known MSP population. Given the high sensitivity, and the generally large beaming fraction of millisecond pulsars, we conclude that SXT 1H 1905+000 is unlikely to emit in radio as a tMSP.

  19. The Analysis of the Possible Thermal Emission at Radio Frequencies from an Evolved Supernova Remnant HB 3 (G132.7+1.3: Revisited

    Directory of Open Access Journals (Sweden)

    Onić, D.

    2008-12-01

    Full Text Available It has recently been reported that some of the flux density values for an evolved supernova remnant (SNR HB 3 (G132.7$+$1.3 are not accurate enough. In this work we therefore revised the analysis of the possible thermal emission at radio frequencies from this SNR using the recently published, corrected flux density values. A model including the sum of non-thermal (purely synchrotron and thermal (bremsstrahlung components is applied to fit the integrated radio spectrum of this SNR. The contribution of thermal component to the total volume emissivity at $1 mathrm{GHz}$ is estimated to be $approx37 \\%$. The ambient density is also estimated to be $napprox 9 mathrm{cm}^{-3}$ for $mathrm{T}=10^{4} mathrm{K}$. Again we obtained a relatively significant presence of thermal emission at radio frequencies from the SNR, which can support interaction between SNR HB 3 and adjacent molecular cloud associated with the mbox{H,{sc ii}} region W3. Our model estimates for thermal component contribution to total volume emissivity at $1 mathrm{GHz}$ and ambient density are similar to those obtained earlier ($approx40 \\%$, $approx10 mathrm{cm^{-3}}$. It is thus obvious that the corrected flux density values do not affect the basic conclusions.

  20. 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

  1. Radio Detection of the Fermi-LAT Blind Search Millisecond Pulsar J1311-3430

    Science.gov (United States)

    Ray, P. S.; Ransom, S. M.; Cheung, C. C.; Giroletti, M.; Cognard, I.; Camilo, F.; Bhattacharyya, B.; Roy, J.; Romani, R. W.; Ferrara, E. C.; hide

    2013-01-01

    We report the detection of radio emission from PSR J1311.3430, the first millisecond pulsar (MSP) discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for less than 10% of approximately 4.5 hr of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nan cay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311.3430 is not radio quiet and provide additional evidence that radio-quiet MSPs are rare. The radio dispersion measure of 37.8 pc cm(exp -3) provides a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulses as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.

  2. The use of Twitter´s Bio in radio programmes. From the profile´s presentation to the transmedia radio

    Directory of Open Access Journals (Sweden)

    Teresa PIÑEIRO OTERO

    2014-06-01

    Full Text Available The jump of conventional radio programs into social media has evolved in new spaces and interaction forms between radio broadcasters and radio listeners. Particularly, twitter community acquires a new dimension due to its public (non privacy status and shareability. From a transmedia perspective, this microblogging platform makes possible to the radio programs offering rich content (access to the tweets of radio show hosts or / and main collaborators, radio channel’s info... to the radio listeners. Although radio listeners can access those profiles on their own, or following real-time references of the program, it’s getting bigger the way radio show hosts use their profiles on twitter to improve synergies between multiple digital channels in order to increase the community engagement. Present article aims to analyze profile twitter bios of the bigger audience Spanish radio programs, in order to determine flow synergies between channels of the radio (brands and radio show hosts on twitter

  3. 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.)

  4. Globular Clusters for Faint Galaxies

    Science.gov (United States)

    Kohler, Susanna

    2017-07-01

    The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions

  5. Cosmological radio emission induced by WIMP Dark Matter

    International Nuclear Information System (INIS)

    Fornengo, N.; Regis, M.; Lineros, R.; Taoso, M.

    2012-01-01

    We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs

  6. Cosmological radio emission induced by WIMP Dark Matter

    Energy Technology Data Exchange (ETDEWEB)

    Fornengo, N.; Regis, M. [Dipartimento di Fisica Teorica, Università di Torino, via P. Giuria 1, I-10125 Torino (Italy); Lineros, R.; Taoso, M., E-mail: fornengo@to.infn.it, E-mail: rlineros@ific.uv.es, E-mail: regis@to.infn.it, E-mail: mtaoso@phas.ubc.ca [IFIC, CSIC-Universidad de Valencia, Ed. Institutos, Apdo. Correos 22085, E-46071 Valencia (Spain)

    2012-03-01

    We present a detailed analysis of the radio synchrotron emission induced by WIMP dark matter annihilations and decays in extragalactic halos. We compute intensity, angular correlation, and source counts and discuss the impact on the expected signals of dark matter clustering, as well as of other astrophysical uncertainties as magnetic fields and spatial diffusion. Bounds on dark matter microscopic properties are then derived, and, depending on the specific set of assumptions, they are competitive with constraints from other indirect dark matter searches. At GHz frequencies, dark matter sources can become a significant fraction of the total number of sources with brightness below the microJansky level. We show that, at this level of fluxes (which are within the reach of the next-generation radio surveys), properties of the faint edge of differential source counts, as well as angular correlation data, can become an important probe for WIMPs.

  7. A dual-mask coronagraph for observing faint companions to binary stars

    NARCIS (Netherlands)

    Cady, E.; McElwain, M.; Kasdin, N.J.; Thalmann, C.

    2011-01-01

    Observations of binary stars for faint companions with conventional coronagraphic methods are challenging, as both targets will be bright enough to obscure any nearby faint companions if their scattered light is not suppressed. We propose coronagraphic examination of binary stars using an

  8. VizieR Online Data Catalog: Radio luminosity function of FSRQs (Mao+, 2017)

    Science.gov (United States)

    Mao, P.; Urry, C. M.; Marchesini, E.; Landoni, M.; Massaro, F.; Ajello, M.

    2018-01-01

    To build the largest sample of flat-spectrum radio quasars, we started with the radio catalog of the Faint Images of the Radio Sky at Twenty Centimeter (FIRST) survey (Helfand+ 2015, VIII/92), which covered 10575deg2 of the sky; and the Green Bank 6cm (GB6) Radio Source Catalog (Gregory+ 1996, VIII/40), which covered 17000deg2 of the sky. We cross-matched the radio position of each FIRST source with sources in the GB6 catalog, taking into account the positional uncertainties of both radio surveys. Of the 638 radio sources with flat radio spectra, 327 have an optical spectrum available in the literature, 266 from SDSS and the rest from various other sources identified through the NASA Extragalactic Database (NED). Out of the 327 objects with optical spectra classified, 200 were classified as FSRQs (of which 168 are free from contamination), 26 were classified as BL Lacs, 38 were classified as Seyferts, 41 were classified as Galaxies, 2 were classified as stars, and 12 and 8 indicated as noisy or uncertain, respectively. An additional 85 quasars (of which 74 are free from contamination) out of the 119 with a literature description were also included in the inclusive sample. See section 2 for more details on the sample selection. (2 data files).

  9. KILOPARSEC-SCALE RADIO STRUCTURES IN NARROW-LINE SEYFERT 1 GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Doi, Akihiro; Kino, Motoki [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nagira, Hiroshi [Graduate School of Science and Engineering, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8512 (Japan); Kawakatu, Nozomu [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Nagai, Hiroshi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Asada, Keiichi, E-mail: akihiro.doi@vsop.isas.jaxa.jp [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)

    2012-11-20

    We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array, which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two {gamma}-ray-emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (1) extended radio luminosities suggesting jet kinetic powers of {approx}> 10{sup 44} erg s{sup -1}, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of {approx}> 10{sup 7} M {sub Sun }, which can generate the necessary jet powers from near-Eddington mass accretion; and (3) two-sided radio structures at kpc scales, requiring expansion rates of {approx}0.01c-0.3c and kinematic ages of {approx}> 10{sup 7} years. On the other hand, most typical NLS1s would be driven by black holes of {approx}< 10{sup 7} M {sub Sun} in a limited lifetime of {approx}10{sup 7} years. Hence, the kpc-scale radio structures may originate in a small window of opportunity during the final stage of the NLS1 phase just before growing into broad-line AGNs.

  10. MULTIWAVELENGTH OBSERVATIONS OF RADIO-QUIET QUASARS WITH WEAK EMISSION LINES

    International Nuclear Information System (INIS)

    Plotkin, Richard M.; Anderson, Scott F.; MacLeod, Chelsea L.; Brandt, W. N.; Schneider, Donald P.; Diamond-Stanic, Aleksandar M.; Fan Xiaohui; Shemmer, Ohad

    2010-01-01

    We present radio and X-ray observations, as well as optical light curves, for a subset of 26 BL Lac candidates from the Sloan Digital Sky Survey (SDSS) lacking strong radio emission and with z < 2.2. Half of these 26 objects are shown to be stars, galaxies, or absorbed quasars. We conclude that the other 13 objects are active galactic nuclei (AGNs) with abnormally weak emission features; 10 of those 13 are definitively radio quiet, and, for those with available optical light curves, their level of optical flux variability is consistent with radio-quiet quasars. We cannot exclude the possibility that some of these 13 AGNs lie on the extremely radio-faint tail of the BL Lac distribution, but our study generally supports the notion that all BL Lac objects are radio-loud. These radio-quiet AGNs appear to have intrinsically weak or absent broad emission line regions (BELRs), and, based on their X-ray properties, we argue that some are low-redshift analogs to weak line quasars (WLQs). SDSS BL Lac searches are so far the only systematic surveys of the SDSS database capable of recovering such exotic low-redshift WLQs. There are 71 more z < 2.2 radio-quiet BL Lac candidates already identified in the SDSS, but not considered here, and many of those might be best unified with WLQs as well. Future studies combining low- and high-redshift WLQ samples will yield new insight on our understanding of the structure and formation of AGN BELRs.

  11. A New Generation of Telecommunications for Mars: The Reconfigurable Software Radio

    Science.gov (United States)

    Adams, J.; Horne, W.

    2000-01-01

    Telecommunications is a critical component for any mission at Mars as it is an enabling function that provides connectivity back to Earth and provides a means for conducting science. New developments in telecommunications, specifically in software - configurable radios, expand the possible approaches for science missions at Mars. These radios provide a flexible and re-configurable platform that can evolve with the mission and that provide an integrated approach to communications and science data processing. Deep space telecommunication faces challenges not normally faced by terrestrial and near-earth communications. Radiation, thermal, highly constrained mass, volume, packaging and reliability all are significant issues. Additionally, once the spacecraft leaves earth, there is no way to go out and upgrade or replace radio components. The reconfigurable software radio is an effort to provide not only a product that is immediately usable in the harsh space environment but also to develop a radio that will stay current as the years pass and technologies evolve.

  12. 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.

  13. Suzaku Diagnostics of the Energetics in the Lobes of the Giant Radio Galaxy 3C 35

    Science.gov (United States)

    Isobe, Naoki; Seta, Hiromi; Gandhi, Poshak; Tashiro, Makoto S.

    2011-02-01

    The Suzaku observation of a giant radio galaxy 3C 35 revealed faint extended X-ray emission, associated with its radio lobes and/or host galaxy. After careful subtraction of the X-ray and non-X-ray background and contaminating X-ray sources, the X-ray spectrum of the faint emission was reproduced by a sum of the power-law (PL) and soft thermal components. The soft component was attributed to the thermal plasma emission from the host galaxy. The photon index of the PL component, Γ = 1.35+0.56 -0.86 +0.11 -0.10, where the first and second errors represent the statistical and systematic ones, was found to agree with the synchrotron radio index from the lobes, ΓR = 1.7. Thus, the PL component was attributed to the inverse Compton (IC) X-rays from the synchrotron electrons in the lobes. The X-ray flux density at 1 keV was derived as 13.6 ± 5.4+4.0 -3.6 nJy with the photon index fixed at the radio value. The X-ray surface brightness from these lobes (~0.2 nJy arcmin-2) is lowest among the lobes studied through the IC X-ray emission. In combination with the synchrotron radio flux density, 7.5 ± 0.2 Jy at 327.4 MHz, the electron energy density spatially averaged over the lobes was evaluated to be the lowest among those radio galaxies, as u e = (5.8 ± 2.3+1.9 -1.7) × 10-14 erg cm-3 over the electron Lorentz factor of 103-105. The magnetic energy density was calculated as u m = (3.1+2.5 -1.0 +1.4 -0.9) × 10-14 erg cm-3, corresponding to the magnetic field strength of 0.88+0.31 -0.16 +0.19 -0.14 μG. These results suggest that the energetics in the 3C 35 lobes are nearly consistent with equipartition between the electrons and magnetic fields.

  14. Composition of faint comets

    International Nuclear Information System (INIS)

    Brown, L.W.

    1986-01-01

    The study uses an emission line, differential imaging camera built by the Science Operations Branch. This instrument allows photometric data to be obtained over a large area of a comet in a large number of resolution elements. The detector is a 100x100 Reticon array which with interchangeable optics can give resolutions from 2'' to 30'' over a field of 1' to 15'. The camera through its controlling computer can simultaneously take images in on-line and continuum filters and through computer subtraction and calibration present a photometric image of the comet produced by only the emission of the molecule under study. Initial work has shown two significant problems. First the auxiliary equipment of the telescope has not allowed the unambiguous location of faint comets so that systematic observations could be made, and secondly initial data has not shown much molecular emission from the faint comets which were located. Work last year on a software and hardware display system and this year on additional guide motors on the 36-inch telescope has allowed the differential camera to act as its own finder and guide scope. Comet IRAS was observed in C2 and CO+, as well as an occultation by the comet of SAO029103. The perodic comet Giacobini-Zinner was also observed in C2

  15. Confirmation of Faint Dwarf Galaxies in the M81 Group

    Science.gov (United States)

    Chiboucas, Kristin; Jacobs, Bradley A.; Tully, R. Brent; Karachentsev, Igor D.

    2013-11-01

    We have followed up on the results of a 65 deg2 CFHT/MegaCam imaging survey of the nearby M81 Group searching for faint and ultra-faint dwarf galaxies. The original survey turned up 22 faint candidate dwarf members. Based on two-color HST ACS/WFC and WFPC2 photometry, we now confirm 14 of these as dwarf galaxy members of the group. Distances and stellar population characteristics are discussed for each. To a completeness limit of M_{r^{\\prime }} = -10, we find a galaxy luminosity function slope of -1.27 ± 0.04 for the M81 Group. In this region, there are now 36 M81 Group members known, including 4 blue compact dwarfs; 8 other late types including the interacting giants M81, NGC 3077, and M82; 19 early type dwarfs; and at least 5 potential tidal dwarf galaxies. We find that the dSph galaxies in M81 appear to lie in a flattened distribution, similar to that found for the Milky Way and M31. One of the newly discovered dSph galaxies has properties similar to the ultra-faint dwarfs being found in the Local Group with a size Re ~ 100 pc and total magnitude estimates M_{r^{\\prime }} = -6.8 and MI ~ -9.1.

  16. HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Kawamata, Ryota; Shimasaku, Kazuhiro [Department of Astronomy, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Oguri, Masamune, E-mail: ishigaki@icrr.u-tokyo.ac.jp [Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-01-20

    We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functions with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ{sub UV}, at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ{sub UV} decrease trend can be reconciled with the large Thomson scattering optical depth, τ{sub e}, measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ{sub UV} decrease and the large τ {sub e}. It is possible that the ρ{sub UV} decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei.

  17. HUBBLE FRONTIER FIELDS FIRST COMPLETE CLUSTER DATA: FAINT GALAXIES AT z ∼ 5-10 FOR UV LUMINOSITY FUNCTIONS AND COSMIC REIONIZATION

    International Nuclear Information System (INIS)

    Ishigaki, Masafumi; Ouchi, Masami; Ono, Yoshiaki; Kawamata, Ryota; Shimasaku, Kazuhiro; Oguri, Masamune

    2015-01-01

    We present comprehensive analyses of faint dropout galaxies up to z ∼ 10 with the first full-depth data set of the A2744 lensing cluster and parallel fields observed by the Hubble Frontier Fields (HFF) program. We identify 54 dropouts at z ∼ 5-10 in the HFF fields and enlarge the size of the z ∼ 9 galaxy sample obtained to date. Although the number of highly magnified (μ ∼ 10) galaxies is small because of the tiny survey volume of strong lensing, our study reaches the galaxies' intrinsic luminosities comparable to the deepest-field HUDF studies. We derive UV luminosity functions with these faint dropouts, carefully evaluating by intensive simulations the combination of observational incompleteness and lensing effects in the image plane, including magnification, distortion, and multiplication of images, with the evaluation of mass model dependencies. Our results confirm that the faint-end slope, α, is as steep as –2 at z ∼ 6-8 and strengthen the evidence for the rapid decrease of UV luminosity densities, ρ UV , at z > 8 from the large z ∼ 9 sample. We examine whether the rapid ρ UV decrease trend can be reconciled with the large Thomson scattering optical depth, τ e , measured by cosmic microwave background experiments, allowing a large space of free parameters, such as an average ionizing photon escape fraction and a stellar-population-dependent conversion factor. No parameter set can reproduce both the rapid ρ UV decrease and the large τ e . It is possible that the ρ UV decrease moderates at z ≳ 11, that the free parameters significantly evolve toward high z, or that there exist additional sources of reionization such as X-ray binaries and faint active galactic nuclei

  18. Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

    Science.gov (United States)

    2001-11-01

    Astronomers have made the first tentative observations of a long-speculated, but never before detected, source of natural radio waves in interstellar space. Data from the National Science Foundation's 140 Foot Radio Telescope at the National Radio Astronomy Observatory in Green Bank, W.Va., show the faint, tell-tale signals of what appear to be dust grains spinning billions of times each second. This discovery eventually could yield a powerful new tool for understanding the interstellar medium - the immense clouds of gas and dust that populate interstellar space. The NRAO 140 Foot Radio Telescope The NRAO 140-Foot Radio Telescope "What we believe we have found," said Douglas P. Finkbeiner of Princeton University's Department of Astrophysics, "is the first hard evidence for electric dipole emission from rapidly rotating dust grains. If our studies are confirmed, it will be the first new source of continuum emission to be conclusively identified in the interstellar medium in nearly the past 20 years." Finkbeiner believes that these emissions have the potential in the future of revealing new and exciting information about the interstellar medium; they also may help to refine future studies of the Cosmic Microwave Background Radiation. The results from this study, which took place in spring 1999, were accepted for publication in Astrophysical Journal. Other contributors to this paper include David J. Schlegel, department of astrophysics, Princeton University; Curtis Frank, department of astronomy, University of Maryland; and Carl Heiles, department of astronomy, University of California at Berkeley. "The idea of dust grains emitting radiation by rotating is not new," comments Finkbeiner, "but to date it has been somewhat speculative." Scientists first proposed in 1957 that dust grains could emit radio signals, if they were caused to rotate rapidly enough. It was believed, however, that these radio emissions would be negligibly small - too weak to be of any impact to

  19. Near-infrared imaging survey of faint companions around young dwarfs in the Pleiades cluster

    International Nuclear Information System (INIS)

    Itoh, Yoichi; Funayama, Hitoshi; Hashiguchi, Toshio; Oasa, Yumiko; Hayashi, Masahiko; Fukagawa, Misato; Currie, Thayne

    2011-01-01

    We conducted a near-infrared imaging survey of 11 young dwarfs in the Pleiades cluster using the Subaru Telescope and the near-infrared coronagraph imager. We found ten faint point sources, with magnitudes as faint as 20 mag in the K-band, with around seven dwarfs. Comparison with the Spitzer archive images revealed that a pair of the faint sources around V 1171 Tau is very red in infrared wavelengths, which indicates very low-mass young stellar objects. However, the results of our follow-up proper motion measurements implied that the central star and the faint sources do not share common proper motions, suggesting that they are not physically associated.

  20. THE EVOLUTION OF THE REST-FRAME V-BAND LUMINOSITY FUNCTION FROM z = 4: A CONSTANT FAINT-END SLOPE OVER THE LAST 12 Gyr OF COSMIC HISTORY

    International Nuclear Information System (INIS)

    Marchesini, Danilo; Stefanon, Mauro; Brammer, Gabriel B.; Whitaker, Katherine E.

    2012-01-01

    We present the rest-frame V-band luminosity function (LF) of galaxies at 0.4 ≤ z < 4.0, measured from a near-infrared selected sample constructed from the NMBS, the FIRES, the FIREWORKS, and the ultra-deep NICMOS and WFC3 observations in the HDFN, HUDF, and GOODS-CDFS, all having high-quality optical-to-mid-infrared data. This unique sample combines data from surveys with a large range of depths and areas in a self-consistent way, allowing us to (1) minimize the uncertainties due to cosmic variance; and (2) simultaneously constrain the bright and faint ends with unprecedented accuracy over the targeted redshift range, probing the LF down to 0.1L* at z ∼ 3.9. We find that (1) the faint end is fairly flat and with a constant slope from z = 4, with α = –1.27 ± 0.05; (2) the characteristic magnitude has dimmed by 1.3 mag from z ∼ 3.7 to z = 0.1; (3) the characteristic density has increased by a factor of ∼8 from z ∼ 3.7 to z = 0.1, with 50% of this increase from z ∼ 4 to z ∼ 1.8; and (4) the luminosity density peaks at z ≈ 1-1.5, increasing by a factor of ∼4 from z = 4.0 to z ≈ 1-1.5, and subsequently decreasing by a factor of ∼1.5 by z = 0.1. We find no evidence for a steepening of the faint-end slope with redshift out to z = 4, in contrast with previous observational claims and theoretical predictions. The constant faint-end slope suggests that the efficiency of stellar feedback may evolve with redshift. Alternative interpretations are discussed, such as different masses of the halos hosting faint galaxies at low and high redshifts and/or environmental effects.

  1. 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)

  2. CONFIRMATION OF FAINT DWARF GALAXIES IN THE M81 GROUP

    Energy Technology Data Exchange (ETDEWEB)

    Chiboucas, Kristin [Gemini Observatory, 670 North A' ohoku Pl, Hilo, HI 96720 (United States); Jacobs, Bradley A.; Tully, R. Brent [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96821 (United States); Karachentsev, Igor D., E-mail: kchibouc@gemini.edu, E-mail: bjacobs@ifa.hawaii.edu, E-mail: tully@ifa.hawaii.edu, E-mail: ikar@luna.sao.ru [Special Astrophysical Observatory (SAO), Russian Academy of Sciences, Nizhnij Arkhyz, Karachai-Cherkessian Republic 369167 (Russian Federation)

    2013-11-01

    We have followed up on the results of a 65 deg{sup 2} CFHT/MegaCam imaging survey of the nearby M81 Group searching for faint and ultra-faint dwarf galaxies. The original survey turned up 22 faint candidate dwarf members. Based on two-color HST ACS/WFC and WFPC2 photometry, we now confirm 14 of these as dwarf galaxy members of the group. Distances and stellar population characteristics are discussed for each. To a completeness limit of M{sub r{sup '}}= -10, we find a galaxy luminosity function slope of –1.27 ± 0.04 for the M81 Group. In this region, there are now 36 M81 Group members known, including 4 blue compact dwarfs; 8 other late types including the interacting giants M81, NGC 3077, and M82; 19 early type dwarfs; and at least 5 potential tidal dwarf galaxies. We find that the dSph galaxies in M81 appear to lie in a flattened distribution, similar to that found for the Milky Way and M31. One of the newly discovered dSph galaxies has properties similar to the ultra-faint dwarfs being found in the Local Group with a size R{sub e} ∼ 100 pc and total magnitude estimates M{sub r{sup '}}= -6.8 and M{sub I} ∼ –9.1.

  3. On the Dearth of Ultra-faint Extremely Metal-poor Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Sánchez Almeida, J.; Filho, M. E.; Vecchia, C. Dalla [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Skillman, E. D., E-mail: jos@iac.es [Minnesota Institute for Astrophysics, School of Physics and Astronomy, University of Minnesota, Minneapolis, MN (United States)

    2017-02-01

    Local extremely metal-poor galaxies (XMPs) are of particular astrophysical interest since they allow us to look into physical processes characteristic of the early universe, from the assembly of galaxy disks to the formation of stars in conditions of low metallicity. Given the luminosity–metallicity relationship, all galaxies fainter than M{sub r} ≃ −13 are expected to be XMPs. Therefore, XMPs should be common in galaxy surveys. However, they are not common, because several observational biases hamper their detection. This work compares the number of faint XMPs in the SDSS-DR7 spectroscopic survey with the expected number, given the known biases and the observed galaxy luminosity function (LF). The faint end of the LF is poorly constrained observationally, but it determines the expected number of XMPs. Surprisingly, the number of observed faint XMPs (∼10) is overpredicted by our calculation, unless the upturn in the faint end of the LF is not present in the model. The lack of an upturn can be naturally understood if most XMPs are central galaxies in their low-mass dark matter halos, which are highly depleted in baryons due to interaction with the cosmic ultraviolet background and to other physical processes. Our result also suggests that the upturn toward low luminosity of the observed galaxy LF is due to satellite galaxies.

  4. UNDERSTANDING THE EVOLUTION OF CLOSE BINARY SYSTEMS WITH RADIO PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, O. G. [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, 1900 La Plata, Buenos Aires (Argentina); De Vito, M. A. [Instituto de Astrofísica de La Plata (IALP), CCT-CONICET-UNLP. Paseo del Bosque S/N (B1900FWA), La Plata (Argentina); Horvath, J. E., E-mail: obenvenu@fcaglp.unlp.edu.ar, E-mail: adevito@fcaglp.unlp.edu.ar, E-mail: foton@astro.iag.usp.br [Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo R. do Matão 1226 (05508-090), Cidade Universitária, São Paulo SP (Brazil)

    2014-05-01

    We calculate the evolution of close binary systems (CBSs) formed by a neutron star (behaving as a radio pulsar) and a normal donor star, which evolve either to a helium white dwarf (HeWD) or to ultra-short orbital period systems. We consider X-ray irradiation feedback and evaporation due to radio pulsar irradiation. We show that irradiation feedback leads to cyclic mass transfer episodes, allowing CBSs to be observed in between episodes as binary radio pulsars under conditions in which standard, non-irradiated models predict the occurrence of a low-mass X-ray binary. This behavior accounts for the existence of a family of eclipsing binary systems known as redbacks. We predict that redback companions should almost fill their Roche lobe, as observed in PSR J1723-2837. This state is also possible for systems evolving with larger orbital periods. Therefore, binary radio pulsars with companion star masses usually interpreted as larger than expected to produce HeWDs may also result in such quasi-Roche lobe overflow states, rather than hosting a carbon-oxygen WD. We found that CBSs with initial orbital periods of P{sub i} < 1 day evolve into redbacks. Some of them produce low-mass HeWDs, and a subgroup with shorter P{sub i} becomes black widows (BWs). Thus, BWs descend from redbacks, although not all redbacks evolve into BWs. There is mounting observational evidence favoring BW pulsars to be very massive (≳ 2 M {sub ☉}). As they should be redback descendants, redback pulsars should also be very massive, since most of the mass is transferred before this stage.

  5. Imaging of Stellar Surfacess Using Radio Facilities Including ALMA

    Science.gov (United States)

    O'Gorman, Eamon

    2018-04-01

    Until very recently, studies focusing on imaging stars at continuum radio wavelengths (here defined as submillimeter, millimeter, and centimeter wavelengths) has been scarce. These studies have mainly been carried out with the Very Large Array on a handful of evolved stars (i.e., Asymptotic Giant Branch and Red Supergiant stars) whereby their stellar disks have just about been spatially resolved. Some of these results however, have challenged our historical views on the nature of evolved star atmospheres. Now, the very long baselines of the Atacama Large Millimeter/submillimeter Array and the newly upgraded Karl G. Jansky Very Large Array provide a new opportunity to image these atmospheres at unprecedented spatial resolution and sensitivity across a much wider portion of the radio spectrum. In this talk I will first provide a history of stellar radio imaging and then discuss some recent exciting ALMA results. Finally I will present some brand new multi-wavelength ALMA and VLA results for the famous red supergiant Antares.

  6. The Faint End of the Quasar Luminosity Function at z ~ 4

    Science.gov (United States)

    Glikman, Eilat; Bogosavljević, Milan; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Mahabal, Ashish

    2010-02-01

    The evolution of the quasar luminosity function (QLF) is one of the basic cosmological measures providing insight into structure formation and mass assembly in the universe. We have conducted a spectroscopic survey to find faint quasars (-26.0 law (Φ vprop L β) gives a faint-end slope β = -1.6 ± 0.2. If we consider our larger, but highly incomplete sample going 1 mag fainter, we measure a steeper faint-end slope -2 law LF. Our best fit finds a bright-end slope, α = -2.4 ± 0.2, and faint-end slope, β = -2.3 ± 0.2, without a well-constrained break luminosity. This is effectively a single power law, with β = -2.7 ± 0.1. We use these results to place limits on the amount of ultraviolet radiation produced by quasars and find that quasars are able to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  7. The GOODS UV Legacy Fields: A Full Census of Faint Star-Forming Galaxies at z~0.5-2

    Science.gov (United States)

    Oesch, Pascal

    2014-10-01

    Deep HST imaging has shown that the overall star formation density and UV light density at z>3 is dominated by faint, blue galaxies. Remarkably, very little is known about the equivalent galaxy population at lower redshifts. Understanding how these galaxies evolve across the epoch of peak cosmic star-formation is key to a complete picture of galaxy evolution. While we and others have been making every effort to use existing UV imaging data, a large fraction of the prior data were taken without post-flash and are not photometric. We now propose to obtain a robust legacy dataset for a complete census of faint star-forming galaxies at z~0.5-2, akin to what is achieved at z>3, using the unique capabilities of the WFC3/UVIS camera to obtain very deep UV imaging to 27.5-28.0 mag over the CANDELS Deep fields in GOODS North and South. We directly sample the FUV at z>~0.5 and we make these prime legacy fields for JWST with unique and essential UV/blue HST coverage. Together with the exquisite ancillary multi-wavelength data at high spatial resolution from ACS and WFC3/IR our program will result in accurate photometric redshifts for very faint sources and will enable a wealth of research by the community. This includes tracing the evolution of the FUV luminosity function over the peak of the star formation rate density from z~3 down to z~0.5, measuring the physical properties of sub-L* galaxies, and characterizing resolved stellar populations to decipher the build-up of the Hubble sequence from sub-galactic clumps. The lack of a future UV space telescope makes the acquisition of such legacy data imperative for the JWST era and beyond.

  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. Detailed abundances in stars belonging to ultra-faint dwarf spheroidal galaxies

    OpenAIRE

    François, P.; Monaco, L.; Villanova, S.; Catelan, M.; Bonifacio, P.; Bellazzini, M.; Bidin, C. Moni; Marconi, G.; Geisler, D.; Sbordone, L.

    2012-01-01

    We report preliminary results concerning the detailed chemical composition of metal poor stars belonging to close ultra-faint dwarf galaxies (hereafter UfDSphs). The abundances have been determined thanks to spectra obtained with X-Shooter, a high efficiency spectrograph installed on one of the ESO VLT units. The sample of ultra-faint dwarf spheroidal stars have abundance ratios slightly lower to what is measured in field halo star of the same metallicity.We did not find extreme abundances in...

  10. THE SUBARU HIGH-z QUASAR SURVEY: DISCOVERY OF FAINT z ∼ 6 QUASARS

    International Nuclear Information System (INIS)

    Kashikawa, Nobunari; Furusawa, Hisanori; Niino, Yuu; Ishizaki, Yoshifumi; Onoue, Masafusa; Toshikawa, Jun; Ishikawa, Shogo; Willott, Chris J.; Im, Myungshin; Shimasaku, Kazuhiro; Ouchi, Masami; Hibon, Pascale

    2015-01-01

    We present the discovery of one or two extremely faint z ∼ 6 quasars in 6.5 deg 2 utilizing a unique capability of the wide-field imaging of the Subaru/Suprime-Cam. The quasar selection was made in (i'-z B ) and (z B -z R ) colors, where z B and z R are bandpasses with central wavelengths of 8842 Å and 9841 Å, respectively. The color selection can effectively isolate quasars at z ∼ 6 from M/L/T dwarfs without the J-band photometry down to z R < 24.0, which is 3.5 mag deeper than the Sloan Digital Sky Survey (SDSS). We have selected 17 promising quasar candidates. The follow-up spectroscopy for seven targets identified one apparent quasar at z = 6.156 with M 1450 = –23.10. We also identified one possible quasar at z = 6.041 with a faint continuum of M 1450 = –22.58 and a narrow Lyα emission with HWHM =427 km s –1 , which cannot be distinguished from Lyman α emitters. We derive the quasar luminosity function at z ∼ 6 by combining our faint quasar sample with the bright quasar samples by SDSS and CFHQS. Including our data points invokes a higher number density in the faintest bin of the quasar luminosity function than the previous estimate employed. This suggests a steeper faint-end slope than lower z, though it is yet uncertain based on a small number of spectroscopically identified faint quasars, and several quasar candidates still remain to be diagnosed. The steepening of the quasar luminosity function at the faint end does increase the expected emission rate of the ionizing photon; however, it only changes by a factor of approximately two to six. This was found to still be insufficient for the required photon budget of reionization at z ∼ 6

  11. High-energy neutrinos from FR0 radio galaxies?

    Science.gov (United States)

    Tavecchio, F.; Righi, C.; Capetti, A.; Grandi, P.; Ghisellini, G.

    2018-04-01

    The sources responsible for the emission of high-energy (≳100 TeV) neutrinos detected by IceCube are still unknown. Among the possible candidates, active galactic nuclei with relativistic jets are often examined, since the outflowing plasma seems to offer the ideal environment to accelerate the required parent high-energy cosmic rays. The non-detection of single-point sources or - almost equivalently - the absence, in the IceCube events, of multiplets originating from the same sky position - constrains the cosmic density and the neutrino output of these sources, pointing to a numerous population of faint sources. Here we explore the possibility that FR0 radio galaxies, the population of compact sources recently identified in large radio and optical surveys and representing the bulk of radio-loud AGN population, can represent suitable candidates for neutrino emission. Modelling the spectral energy distribution of an FR0 radio galaxy recently associated with a γ-ray source detected by the Large Area Telescope onboard Fermi, we derive the physical parameters of its jet, in particular the power carried by it. We consider the possible mechanisms of neutrino production, concluding that pγ reactions in the jet between protons and ambient radiation is too inefficient to sustain the required output. We propose an alternative scenario, in which protons, accelerated in the jet, escape from it and diffuse in the host galaxy, producing neutrinos as a result of pp scattering with the interstellar gas, in strict analogy with the processes taking place in star-forming galaxies.

  12. 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.

  13. A tale of two feedbacks: Star formation in the host galaxies of radio AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Karouzos, Marios; Im, Myungshin; Jeon, Yiseul; Kim, Ji Hoon [CEOU-Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul (Korea, Republic of); Trichas, Markos [Airbus Defence and Space, Gunnels Wood Road, Stevenage SG1 2AS (United Kingdom); Goto, Tomo [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Malkan, Matt [Division of Astronomy and Astrophysics, 3-714 UCLA, CA 90095-1547 (United States); Ruiz, Angel [Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, 411 007 Pune (India); Lee, Hyung Mok; Kim, Seong Jin [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul (Korea, Republic of); Oi, Nagisa; Matsuhara, Hideo; Takagi, Toshinobu; Murata, K.; Wada, Takehiko; Wada, Kensuke [Institute of Space and Astronautical Science, JAXA, Yoshino-dai 3-1-1, Sagamihara, Kanagawa 229-8510 (Japan); Shim, Hyunjin [Department of Earth Science Education, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Hanami, Hitoshi [Physics Section, Faculty of Humanities, Iwate University, Ueda 3 chome, 18-34 Morioka, Morioka, Iwate 020-8550 (Japan); Serjeant, Stephen; White, Glenn J., E-mail: mkarouzos@astro.snu.ac.kr [Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes (United Kingdom); and others

    2014-04-01

    Several lines of argument support the existence of a link between activity at the nuclei of galaxies, in the form of an accreting supermassive black hole, and star formation activity in these galaxies. Radio jets have long been argued to be an ideal mechanism that allows active galactic nuclei (AGNs) to interact with their host galaxies and affect star formation. We use a sample of radio sources in the North Ecliptic Pole (NEP) field to study the nature of this putative link, by means of spectral energy distribution (SED) fitting. We employ the excellent spectral coverage of the AKARI infrared space telescope and the rich ancillary data available in the NEP to build SEDs extending from UV to far-IR wavelengths. We find a significant AGN component in our sample of relatively faint radio sources (radio luminosity. In contrast, for narrow redshift and AGN luminosity ranges, we find that increasing radio luminosity leads to a decrease in the specific star formation rate. The most radio-loud AGNs are found to lie on the main sequence of star formation for their respective redshifts. For the first time, we potentially see such a two-sided feedback process in the same sample. We discuss the possible suppression of star formation, but not total quenching, in systems with strong radio jets, that supports the maintenance nature of feedback from radio AGN jets.

  14. The Population of Optically Faint GEO Debris

    Science.gov (United States)

    Seitzer, Patrick; Barker, Ed; Buckalew, Brent; Burkhardt, Andrew; Cowardin, Heather; Frith, James; Gomez, Juan; Kaleida, Catherine; Lederer, Susan M.; Lee, Chris H.

    2016-01-01

    The 6.5-m Magellan telescope 'Walter Baade' at the Las Campanas Observatory in Chile has been used for spot surveys of the GEO orbital regime to study the population of optically faint GEO debris. The goal is to estimate the size of the population of GEO debris at sizes much smaller than can be studied with 1-meter class telescopes. Despite the small size of the field of view of the Magellan instrument (diameter 0.5-degree), a significant population of objects fainter than R = 19th magnitude have been found with angular rates consistent with circular orbits at GEO. We compare the size of this population with the numbers of GEO objects found at brighter magnitudes by smaller telescopes. The observed detections have a wide range in characteristics starting with those appearing as short uniform streaks. But there are a substantial number of detections with variations in brightness, flashers, during the 5-second exposure. The duration of each of these flashes can be extremely brief: sometimes less than half a second. This is characteristic of a rapidly tumbling object with a quite variable projected size times albedo. If the albedo is of the order of 0.2, then the largest projected size of these objects is around 10-cm. The data in this paper was collected over the last several years using Magellan's IMACS camera in f/2 mode. The analysis shows the brightness bins for the observed GEO population as well as the periodicity of the flashers. All objects presented are correlated with the catalog: the focus of the paper will be on the uncorrelated, optically faint, objects. The goal of this project is to better characterize the faint debris population in GEO that access to a 6.5-m optical telescope in a superb site can provide.

  15. Faint Objects and How to Observe Them

    CERN Document Server

    Cudnik, Brian

    2013-01-01

    Astronomers' Observing Guides provide up-to-date information for amateur astronomers who want to know all about what it is they are observing. This is the basis of the first part of the book. The second part details observing techniques for practical astronomers, working with a range of different instruments. Faint Objects and How to Observe Them is for visual observers who want to "go deep" with their observing. It's a guide to some of the most distant, dim, and rarely observed objects in the sky, with background information on surveys and object lists -- some familiar and some not. Typically, amateur astronomers begin by looking at the brighter objects, and work their way "deeper" as their experience and skills improve. Faint Objects is about the faintest objects we can see with an amateur's telescope -- their physical nature, why they appear so dim, and how to track them down. By definition, these objects are hard to see! But moderate equipment (a decent telescope of at least 10-inch aperture) and the righ...

  16. 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

  17. RADIO EMISSION FROM SN 1994I IN NGC 5194 (M 51): THE BEST-STUDIED TYPE Ib/c RADIO SUPERNOVA

    International Nuclear Information System (INIS)

    Weiler, Kurt W.; Panagia, Nino; Stockdale, Christopher; Rupen, Michael; Sramek, Richard A.; Williams, Christopher L.

    2011-01-01

    We present the results of detailed monitoring of the radio emission from the Type Ic supernova SN 1994I from three days after optical discovery on 1994 March 31 until eight years later at age 2927 days on 2002 April 5. The data were mainly obtained using the Very Large Array at the five wavelengths of λλ1.3, 2.0, 3.6, 6.2, and 21 cm and from the Cambridge 5 km Ryle Telescope at λ2.0 cm. Two additional measurements were obtained at millimeter wavelengths. This data set represents the most complete, multifrequency radio observations ever obtained for a Type Ib/c supernova. The radio emission evolves regularly in both time and frequency and is well described by established supernova emission/absorption models. It is the first radio supernova with sufficient data to show that it is clearly dominated by the effects of synchrotron self-absorption at early times.

  18. 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

  19. How did the Sun affect the climate when life evolved on the Earth?

    DEFF Research Database (Denmark)

    Karoff, Christoffer; Svensmark, Henrik

    2010-01-01

    day Sun. The reduction in the galactic cosmic ray influx caused by the young Sun's enhanced shielding capability has been suggested as a solution to what is known as the faint young Sun paradox, i.e. the fact that the luminosity of the young Sun was only around 75% of its present value when life...... started to evolve on our planet around four billion years ago. This suggestion relies on the hypothesis that the changing solar activity results in a changing influx of galactic cosmic rays to the Earth, which results in a changing low-altitude cloud coverage and thus a changing climate. Here we show how...

  20. 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.

  1. 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.

  2. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Balokovic, M. [Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Smolcic, V. [Argelander-Institut fuer Astronomie, Auf dem Hugel 71, D-53121 Bonn (Germany); Ivezic, Z. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Zamorani, G. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Schinnerer, E. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Kelly, B. C. [Department of Physics, Broida Hall, University of California, Santa Barbara, CA 93106 (United States)

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 {+-} 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  3. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    International Nuclear Information System (INIS)

    Baloković, M.; Smolčić, V.; Ivezić, Ž.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-01-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 ± 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  4. Chemical Abundance Measurements of Ultra-Faint Dwarf Galaxies Discovered by the Dark Energy Survey

    Science.gov (United States)

    Nagasawa, Daniel; Marshall, Jennifer L.; Simon, Joshua D.; Hansen, Terese; Li, Ting; Bernstein, Rebecca; Balbinot, Eduardo; Drlica-Wagner, Alex; Pace, Andrew; Strigari, Louis; Pellegrino, Craig; DePoy, Darren L.; Suntzeff, Nicholas; Bechtol, Keith; Dark Energy Suvey

    2018-01-01

    We present chemical abundance analysis results derived from high-resolution spectroscopy of ultra-faint dwarfs discovered by the Dark Energy Survey. Ultra-faint dwarf galaxies preserve a fossil record of the chemical abundance patterns imprinted by the first stars in the Universe. High-resolution spectroscopic observations of member stars in several recently discovered Milky Way satellites reveal a range of abundance patterns among ultra-faint dwarfs suggesting that star formation processes in the early Universe were quite diverse. The chemical content provides a glimpse not only of the varied nucleosynthetic processes and chemical history of the dwarfs themselves, but also the environment in which they were formed. We present the chemical abundance analysis of these objects and discuss possible explanations for the observed abundance patterns.

  5. 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)

  6. Photometric Variability in the Faint Sky Variability Survey

    NARCIS (Netherlands)

    Morales-Rueda, L.; Groot, P.J.; Augusteijn, T.; Nelemans, G.A.; Vreeswijk, P.M.; Besselaar, E.J.M. van den

    2005-01-01

    The Faint Sky Variability Survey (FSVS) is aimed at finding photometric and/or astrometric variable objects between 16th and 24th mag on time-scales between tens of minutes and years with photometric precisions ranging from 3 millimag to 0.2 mag. An area of ~23 deg2, located at mid and

  7. The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): survey design, data catalogue and GAMA/WiggleZ spectroscopy

    Science.gov (United States)

    Ching, John H. Y.; Sadler, Elaine M.; Croom, Scott M.; Johnston, Helen M.; Pracy, Michael B.; Couch, Warrick J.; Hopkins, A. M.; Jurek, Russell J.; Pimbblet, K. A.

    2017-01-01

    We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ˜ 0.8. The catalogue covers ˜800 deg2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of Imod point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radio-loud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc.

  8. Mixing advertising and editorial content in radio programmes: appreciation and recall of brand placements versus commercials

    NARCIS (Netherlands)

    van Reijmersdal, E.A.

    2011-01-01

    Although the literature on brand placement is rapidly evolving, no studies thus far have focused on radio brand placement or on the effects of the combination of brand placement and commercials. Therefore, the present experiment (N = 153) focused on the effects of radio brand placement on liking,

  9. Faint galaxies - Bounds on the epoch of galaxy formation and the cosmological deceleration parameter

    International Nuclear Information System (INIS)

    Yoshii, Yuzuru; Peterson, B.A.

    1991-01-01

    Models of galaxy luminosity evolution are used to interpret the observed color distributions, redshift distributions, and number counts of faint galaxies. It is found from the color distributions that the redshift corresponding to the epoch of galaxy formation must be greater than three, and that the number counts of faint galaxies, which are sensitive to the slope of the faint end of the luminosity function, are incompatible with q0 = 1/2 and indicate a smaller value. The models assume that the sequence of galaxy types is due to different star-formation rates, that the period of galaxy formation can be characterized by a single epoch, and that after formation, galaxies change in luminosity by star formation and stellar evolution, maintaining a constant comoving space density. 40 refs

  10. A peculiar distribution of radial velocities of faint radio-galaxies with 13.0<=msub(corr)<=15.5

    International Nuclear Information System (INIS)

    Karoji, H.; Nottale, L.; Vigier, J.-P.

    1976-01-01

    A sample of 41 radio-galaxies with 13.0<=msub(corr)<=15.5 has been analyzed to test the angular redshift anisotropy discovered on Sc I galaxies by Rubin, Rubin and Ford (1973). The sample does not present their anisotropy but contains an even more curious distribution of radial velocities which suggests that the Rubin-Ford effect results from an anomalous redshift of light when it travels through clusters of galaxies. (Auth.)

  11. X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

    Science.gov (United States)

    Torresi, E.; Grandi, P.; Capetti, A.; Baldi, R. D.; Giovannini, G.

    2018-06-01

    Fanaroff-Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to Fanaroff-Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

  12. Jets in Hydrogen-poor Superluminous Supernovae: Constraints from a Comprehensive Analysis of Radio Observations

    Science.gov (United States)

    Coppejans, D. L.; Margutti, R.; Guidorzi, C.; Chomiuk, L.; Alexander, K. D.; Berger, E.; Bietenholz, M. F.; Blanchard, P. K.; Challis, P.; Chornock, R.; Drout, M.; Fong, W.; MacFadyen, A.; Migliori, G.; Milisavljevic, D.; Nicholl, M.; Parrent, J. T.; Terreran, G.; Zauderer, B. A.

    2018-03-01

    The energy source powering the extreme optical luminosity of hydrogen-stripped superluminous supernovae (SLSNe-I) is not known, but recent studies have highlighted the case for a central engine. Radio and/or X-ray observations are best placed to track the fastest ejecta and probe the presence of outflows from a central engine. We compile all the published radio observations of SLSNe-I to date and present three new observations of two new SLSNe-I. None were detected. Through modeling the radio emission, we constrain the subparsec environments and possible outflows in SLSNe-I. In this sample, we rule out on-axis collimated relativistic jets of the kind detected in gamma-ray bursts (GRBs). We constrain off-axis jets with opening angles of 5° (30°) to energies of {E}{{k}}values {ε }e=0.1 and {ε }B=0.01. The deepest limits rule out emission of the kind seen in faint uncollimated GRBs (with the exception of GRB 060218) and from relativistic SNe. Finally, for the closest SLSN-I, SN 2017egm, we constrain the energy of an uncollimated nonrelativistic outflow like those observed in normal SNe to {E}{{k}}≲ {10}48 erg.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. Hubble Space Telescope, Faint Object Camera

    Science.gov (United States)

    1981-01-01

    This drawing illustrates Hubble Space Telescope's (HST's), Faint Object Camera (FOC). The FOC reflects light down one of two optical pathways. The light enters a detector after passing through filters or through devices that can block out light from bright objects. Light from bright objects is blocked out to enable the FOC to see background images. The detector intensifies the image, then records it much like a television camera. For faint objects, images can be built up over long exposure times. The total image is translated into digital data, transmitted to Earth, and then reconstructed. The purpose of the HST, the most complex and sensitive optical telescope ever made, is to study the cosmos from a low-Earth orbit. By placing the telescope in space, astronomers are able to collect data that is free of the Earth's atmosphere. The HST detects objects 25 times fainter than the dimmest objects seen from Earth and provides astronomers with an observable universe 250 times larger than visible from ground-based telescopes, perhaps as far away as 14 billion light-years. The HST views galaxies, stars, planets, comets, possibly other solar systems, and even unusual phenomena such as quasars, with 10 times the clarity of ground-based telescopes. The HST was deployed from the Space Shuttle Discovery (STS-31 mission) into Earth orbit in April 1990. The Marshall Space Flight Center had responsibility for design, development, and construction of the HST. The Perkin-Elmer Corporation, in Danbury, Cornecticut, developed the optical system and guidance sensors.

  18. The faint-end of galaxy luminosity functions at the Epoch of Reionization

    Science.gov (United States)

    Yue, B.; Castellano, M.; Ferrara, A.; Fontana, A.; Merlin, E.; Amorín, R.; Grazian, A.; Mármol-Queralto, E.; Michałowski, M. J.; Mortlock, A.; Paris, D.; Parsa, S.; Pilo, S.; Santini, P.; Di Criscienzo, M.

    2018-05-01

    During the Epoch of Reionization (EoR), feedback effects reduce the efficiency of star formation process in small halos or even fully quench it. The galaxy luminosity function (LF) may then turn over at the faint-end. We analyze the number counts of z > 5 galaxies observed in the fields of four Frontier Fields (FFs) clusters and obtain constraints on the LF faint-end: for the turn-over magnitude at z ~ 6, MUVT >~-13.3 for the circular velocity threshold of quenching star formation process, vc* <~ 47 km s-1. We have not yet found significant evidence of the presence of feedback effects suppressing the star formation in small galaxies.

  19. DISCOVERY OF A FAINT QUASAR AT z ∼ 6 AND IMPLICATIONS FOR COSMIC REIONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yongjung; Im, Myungshin; Jeon, Yiseul; Choi, Changsu; Hong, Jueun; Hyun, Minhee; Jun, Hyunsung David; Kim, Dohyeong; Kim, Duho; Kim, Jae-Woo; Lee, Seong-Kook; Taak, Yoon Chan; Yoon, Yongmin [Center for the Exploration of the Origin of the Universe (CEOU), Building 45, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Minjin; Park, Won-Kee [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Karouzos, Marios [Astronomy Program, FPRD, Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kim, Ji Hoon [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720 (United States); Pak, Soojong, E-mail: yjkim@astro.snu.ac.kr, E-mail: mim@astro.snu.ac.kr [School of Space Research and Institute of Natural Sciences, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 446-701 (Korea, Republic of)

    2015-11-10

    Recent studies suggest that faint active galactic nuclei may be responsible for the reionization of the universe. Confirmation of this scenario requires spectroscopic identification of faint quasars (M{sub 1450} > −24 mag) at z ≳ 6, but only a very small number of such quasars have been spectroscopically identified so far. Here, we report the discovery of a faint quasar IMS J220417.92+011144.8 at z ∼ 6 in a 12.5 deg{sup 2} region of the SA22 field of the Infrared Medium-deep Survey (IMS). The spectrum of the quasar shows a sharp break at ∼8443 Å, with emission lines redshifted to z = 5.944 ± 0.002 and rest-frame ultraviolet continuum magnitude M{sub 1450} = −23.59 ± 0.10 AB mag. The discovery of IMS J220417.92+011144.8 is consistent with the expected number of quasars at z ∼ 6 estimated from quasar luminosity functions based on previous observations of spectroscopically identified low-luminosity quasars. This suggests that the number of M{sub 1450} ∼ −23 mag quasars at z ∼ 6 may not be high enough to fully account for the reionization of the universe. In addition, our study demonstrates that faint quasars in the early universe can be identified effectively with a moderately wide and deep near-infrared survey such as the IMS.

  20. RADIO EMISSION FROM RED-GIANT HOT JUPITERS

    International Nuclear Information System (INIS)

    Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

    2016-01-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array

  1. RADIO EMISSION FROM RED-GIANT HOT JUPITERS

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Yuka [Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo, 152-8550 (Japan); Spiegel, David S. [Analytics and Algorithms, Stitch Fix, San Francisco, CA 94103 (United States); Mroczkowski, Tony [Naval Research Laboratory, 4555 Overlook Ave SW, Washington, DC 20375 (United States); Nordhaus, Jason [Department of Science and Mathematics, National Technical Institute for the Deaf, Rochester Institute of Technology, Rochester, NY 14623 (United States); Zimmerman, Neil T. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Parsons, Aaron R. [Astronomy Department, University of California, Berkeley, CA (United States); Mirbabayi, Mehrdad [Astrophysics Department, Institute for Advanced Study, Princeton, NJ 08540 (United States); Madhusudhan, Nikku, E-mail: yuka.fujii@elsi.jp [Astronomy Department, University of Cambridge (United Kingdom)

    2016-04-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

  2. Radio Emission from Red-Giant Hot Jupiters

    Science.gov (United States)

    Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

    2016-01-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such "Red-Giant Hot Jupiters" (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

  3. 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

  4. Short timescale variability in the faint sky variability survey

    NARCIS (Netherlands)

    Morales-Rueda, L.; Groot, P.J.; Augusteijn, T.; Nelemans, G.A.; Vreeswijk, P.M.; Besselaar, E.J.M. van den

    2006-01-01

    We present the V-band variability analysis of the Faint Sky Variability Survey (FSVS). The FSVS combines colour and time variability information, from timescales of 24 minutes to tens of days, down to V = 24. We find that �1% of all point sources are variable along the main sequence reaching �3.5%

  5. A Fast Radio Burst Every Second?

    Science.gov (United States)

    Kohler, Susanna

    2017-09-01

    far. [Fialkov Loeb 2017]The FRB luminosity functionFRBs may all have the same intrinsic brightness (like Type Ia supernovae, for instance). Alternatively, there may be many more faint and dim FRBs than bright ones (like the distribution of galaxy luminosities). Thisdifference affects the number of FRBs we could detect.The host galaxy populationAre FRBs most commonly hosted by low-mass galaxies like FRB 121102? Or do they occur in high-mass galaxies as well? This affects the number of FRBs we would expect to observe at different redshifts.Future HopeBy exploring a range of models that vary these three factors, Fialkov and Loeb find estimates for the rate of FRBs that would appear inthe 500 MHz3.5 GHz frequency band probed by observatories like Parkes, Arecibo, and the Australian Square Kilometre Array Pathfinder (ASKAP).Fialkov and Loeb find that, when we account for faint sources, one FRB may occur per second across the sky in this band. The authors show that future low-frequency radio telescopes with higher sensitivity, such as the Square Kilometre Array, should be able to detect many more of these sources, helping us to differentiate between the models and narrow down the properties of the bursts and their hosts. This, in turn, may finally reveal what causes these mysterious signals.CitationAnastasia Fialkov and Abraham Loeb 2017 ApJL 846 L27. doi:10.3847/2041-8213/aa8905

  6. Long-Term Continuous Double Station Observation of Faint Meteor Showers

    Czech Academy of Sciences Publication Activity Database

    Vítek, S.; Páta, P.; Koten, Pavel; Fliegel, K.

    2016-01-01

    Roč. 16, č. 9 (2016), 1493/1-1493/10 ISSN 1424-8220 R&D Projects: GA ČR GA14-25251S Institutional support: RVO:67985815 Keywords : faint meteor shower * meteoroid * CCD camera Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 2.677, year: 2016

  7. Counts and colors of faint galaxies

    International Nuclear Information System (INIS)

    Kron, R.G.

    1980-01-01

    The color distribution of faint galaxies is an observational dimension which has not yet been fully exploited, despite the important constraints obtainable for galaxy evolution and cosmology. Number-magnitude counts alone contain very diluted information about the state of things because galaxies from a wide range in redshift contribute to the counts at each magnitude. The most-frequently-seen type of galaxy depends on the luminosity function and the relative proportions of galaxies of different spectral classes. The addition of color as a measured quantity can thus considerably sharpen the interpretation of galaxy counts since the apparent color depends on the redshift and rest-frame spectrum. (Auth.)

  8. FOREWORD: Radio and Antenna Days of the Indian Ocean (RADIO 2012)

    Science.gov (United States)

    Monebhurrun, Vikass; Lesselier, Dominique

    2013-04-01

    scientists delivered keynote speeches during the conference. The two workshops consisted of both regular and invited papers. A call to extended contributions for publication as a volume in the IOP Conference Series: Materials Science and Engineering (MSE) both on-line and in print, was made. Following the call, we received thirty-three full papers and all submitted contributions were then peer-reviewed by the co-editors with considerable help from the editorial board. Following this procedure, twenty-seven of them were accepted for publication in this volume. We believe that this volume will be both an excellent source of pertinant and long-lasting scientific material in the fast evolving fields that are covered by RADIO 2012 as well as good proof of its relevance to the scientific Indian Ocean community and far beyond. Editors Vikass Monebhurrun Dominique Lesselier Editorial Board Members Subramaniam Ananthakrishnan Pavel Belov Michael Gaylard Stephen Gedney Yashwant Gupta Sheshakamal Jayaram Wout Joseph Per-Simon Kildal Dominique Lesselier Jean-Daniel Lan Sun Luk André de Lustrac Vikass Monebhurrun Russel Taylor Lok C Lew Yan Voon

  9. Millimeter-wave and Terahertz Reconfigurable Radio-over-Fiber Systems

    DEFF Research Database (Denmark)

    Vegas Olmos, Juan José

    when deploying fiber is not an option. Radio-over-Fiber (RoF) technologies have evolved from a blue sky academic topic in the 90s to a main driver within the current quest for the 5th generation mobile systems (5G). A twist in RoF technologies is that it has found along the way niches in areas non......, the complexity of fabrication and to integrate this solutions have to compete with the off-the-shelf solutions provided by RoF technologies. Technologically though, reconfigurable Radio-over-Fiber networks require a co-design effort involving tunable lasers, digital signal processing, high speed modulators...

  10. Cognitive Radio Networks for Tactical Wireless Communications

    Science.gov (United States)

    2014-12-01

    exists. Instead, security is an evolving process, as we have seen in the context of WLANs and 2G / 3G networks. New system vulnerabilities continue to...in the network configuration and radio parameters take place due to mobility of platforms, and variation in other users of the RF environment. CRNs...dynamic spectrum access experimentally, and it represents the largest military Mobile Ad hoc Network (MANET) as of today. The WNaN demonstrator has been

  11. THE INTRINSIC FRACTIONS AND RADIO PROPERTIES OF LOW-IONIZATION BROAD ABSORPTION LINE QUASARS

    International Nuclear Information System (INIS)

    Dai Xinyu; Shankar, Francesco; Sivakoff, Gregory R.

    2012-01-01

    Low-ionization (Mg II, Fe II, and Fe III) broad absorption line quasars (LoBALs) probe a relatively obscured quasar population and could be at an early evolutionary stage for quasars. We study the intrinsic fractions of LoBALs using the Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey, and Faint Images of the Radio Sky at Twenty cm survey. We find that the LoBAL fractions of the near-infrared (NIR) and radio samples are approximately 5-7 times higher than those measured in the optical sample. This suggests that the fractions measured in the NIR and radio bands are closer to the intrinsic fractions of the populations, and that the optical fractions are significantly biased due to obscuration effects, similar to high-ionization broad absorption line quasars (HiBALs). Considering a population of obscured quasars that do not enter the SDSS, which could have a much higher LoBAL fraction, we expect that the intrinsic fraction of LoBALs could be even higher. We also find that the LoBAL fractions decrease with increasing radio luminosities, again, similarly to HiBALs. In addition, we find evidence for increasing fractions of LoBALs toward higher NIR luminosities, especially for FeLoBALs with a fraction of ∼18% at M K s < -31 mag. This population of NIR-luminous LoBALs may be at an early evolutionary stage of quasar evolution. To interpret the data, we use a luminosity-dependent model for LoBALs that yields significantly better fits than those from a pure geometric model.

  12. The Properties of Faint Field Galaxies

    Science.gov (United States)

    Driver, Simon. P.

    1994-12-01

    One of the current drawbacks of Charge Coupled Devices (CCDs) is their restrictive fields of view. The Hitchhiker CCD camera overcomes this limitation by operating in parallel with existing instrumentation and is able to cover a large area as well as large volumes. Hitchhiker is mounted on the 4.2m William Herschel Telescope and has been operating for two years. The first use of the Hitchhiker data set has been to study the general properties of faint galaxies. The observed trend of how the differential numbers of galaxies vary with magnitude agrees extremely well with those of other groups and covers, for the first time, all four major optical bandpasses. This multi-band capability has also allowed the study of how the colors of galaxies change with magnitude and how the correlation of galaxies on the sky varies between the optical bandpasses. A dwarf dominated model has been developed to explain these observations and challenges our knowledge of the space-density of dwarf galaxies. The model demonstrates that a simple upward turn in the luminosity distribution of galaxies, similar to that observed in clusters, would remain undetected by the field surveys yet can explain many of the observations without recourse to non-passive galaxy evolution. The conclusion is that the field luminosity distribution is not constrained at faint absolute magnitudes. A combination of a high density of dwarf galaxies and mild evolution could explain all the observations. Continuing work with HST and the Medium Deep Survey Team now reveals the morphological mix of galaxies down to mI ~ 24.0. The results confirm that ellipticals and early-type spirals are well fitted by standard no-evolution models whilst the late-type spirals can only be fitted by strong evolution and/or a significant turn-up in the local field LF.

  13. The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

    International Nuclear Information System (INIS)

    Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard; Marshall, Kevin; Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver

    2014-01-01

    Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

  14. The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

    Energy Technology Data Exchange (ETDEWEB)

    Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303-3083 (United States); Marshall, Kevin [Department of Physics and Astronomy, Widener University, Chester, PA 19013 (United States); Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver, E-mail: maune@chara.gsu.edu [Cahill Laboratory of Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)

    2014-10-10

    Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

  15. Radio observations of the CMa OB1 H II regions

    International Nuclear Information System (INIS)

    Gaylard, M.J.; Kemball, A.J.

    1984-01-01

    A sensitive 10 0 x 15 0 13-cm map made of the CMa OB1 H II regions' radio emission shows a strong similarity to Hα emission photographs. Sharpless 296 is shown to consist of a prominent central and western arc completed by a weaker southern loop, and with a faint northern bar. The emission is thermal, superimposed over a predominantly non-thermal background. The H142α recombination line has been detected at eight positions in S296, and in S292 and S297. The average electron temperature in S296 is 6900 +- 1300 K. The UV fluxes from the CMa OB1 stars account for the observed emission measures of the H II regions. The H142α 1sr velocities indicate that the ionized material is in contact with the molecular clouds. (author)

  16. MEASURING THE UNDETECTABLE: PROPER MOTIONS AND PARALLAXES OF VERY FAINT SOURCES

    International Nuclear Information System (INIS)

    Lang, Dustin; Hogg, David W.; Jester, Sebastian; Rix, Hans-Walter

    2009-01-01

    The near future of astrophysics involves many large solid-angle, multi-epoch, multiband imaging surveys. These surveys will, at their faint limits, have data on a large number of sources that are too faint to be detected at any individual epoch. Here, we show that it is possible to measure in multi-epoch data not only the fluxes and positions, but also the parallaxes and proper motions of sources that are too faint to be detected at any individual epoch. The method involves fitting a model of a moving point source simultaneously to all imaging, taking account of the noise and point-spread function (PSF) in each image. By this method it is possible to measure the proper motion of a point source with an uncertainty close to the minimum possible uncertainty given the information in the data, which is limited by the PSF, the distribution of observation times (epochs), and the total signal-to-noise in the combined data. We demonstrate our technique on multi-epoch Sloan Digital Sky Survey (SDSS) imaging of the SDSS Southern Stripe (SDSSSS). We show that with our new technique we can use proper motions to distinguish very red brown dwarfs from very high-redshift quasars in these SDSS data, for objects that are inaccessible to traditional techniques, and with better fidelity than by multiband imaging alone. We rediscover all 10 known brown dwarfs in our sample and present nine new candidate brown dwarfs, identified on the basis of significant proper motion.

  17. A CLOSER VIEW OF THE RADIO-FIR CORRELATION: DISENTANGLING THE CONTRIBUTIONS OF STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

    International Nuclear Information System (INIS)

    Moric, I.; Smolcic, V.; Riechers, D. A.; Scoville, N.; Kimball, A.; Ivezic, Z.

    2010-01-01

    We extend the Unified Radio Catalog, a catalog of sources detected by various (NVSS, FIRST, WENSS, GB6) radio surveys, and SDSS, to IR wavelengths by matching it to the IRAS Point and Faint Source catalogs. By fitting each NVSS-selected galaxy's NUV-NIR spectral energy distribution (SED) with stellar population synthesis models we add to the catalog star formation rates (SFRs), stellar masses, and attenuations. We further add information about optical emission-line properties for NVSS-selected galaxies with available SDSS spectroscopy. Using an NVSS 20 cm (F 1.4 G Hz ∼> 2.5 mJy) selected sample, matched to the SDSS spectroscopic ('main' galaxy and quasar) catalogs and IRAS data (0.04 < z ∼< 0.2) we perform an in-depth analysis of the radio-FIR correlation for various types of galaxies, separated into (1) quasars, (2) star-forming, (3) composite, (4) Seyfert, (5) LINER, and (6) absorption line galaxies using the standard optical spectroscopic diagnostic tools. We utilize SED-based SFRs to independently quantify the source of radio and FIR emission in our galaxies. Our results show that Seyfert galaxies have FIR/radio ratios lower than, but still within the scatter of, the canonical value due to an additional (likely active galactic nucleus (AGN)) contribution to their radio continuum emission. Furthermore, IR-detected absorption and LINER galaxies are on average strongly dominated by AGN activity in both their FIR and radio emission; however their average FIR/radio ratio is consistent with that expected for star-forming galaxies. In summary, we find that most AGN-containing galaxies in our NVSS-IRAS-SDSS sample have FIR/radio flux ratios indistinguishable from those of the star-forming galaxies that define the radio-FIR correlation. Thus, attempts to separate AGNs from star-forming galaxies by their FIR/radio flux ratios alone can separate only a small fraction of the AGNs, such as the radio-loud quasars.

  18. Observations of faint comets at McDonald Observatory: 1978-1980

    Science.gov (United States)

    Barker, E. S.; Cochran, A. L.; Rybski, P. M.

    1981-01-01

    Modern observational techniques, developed for spectroscopy and photometry of faint galaxies and quasars, successfully applied to faint comets on the 2.7 m telescope. The periodic comets Van Biesbrock, Ashbrook-Jackson, Schwassmann-Wachmann 1, Tempel 2, Encke, Forbes, Brooks 2, Stephan-Oterma and the new comets Bradfield (19791), Bowell (1980b), Chernis-Petrauskas (1980k) were observed. The comets ranged in magnitude from 10th to 20th magnitude. For comets fainter than 19th magnitude, reflectance spectra at 100A resolution and area photometry were obtained. On comets of 17th or 18th magnitude, spectrometric scans (6A resolution) of the nucleus or inner coma region. On those comets which are brighter than 16th magnitude spatial spectrophotometric (6A resolution) studies of the inner and extended comae were done. An extensive spatial study of the comae of P/Encke and P/Stephen-Oterma, correlated with heliocentric distance is taking place. The observing process used is described and examples of the results obtained to date are discussed.

  19. La digitalización de la radio deportiva

    Directory of Open Access Journals (Sweden)

    Romero Bejarano, Hilario José

    2011-12-01

    Full Text Available En español: La radio se ha visto sumergida en los últimos años en una fase de integración tecnológica y empresarial de carácter multimedia, así como de diversificación de sistemas y canales de difusión. Asimismo, Internet se ha ido consolidando como la plataforma de radio digital que más ha evolucionado como consecuencia de su constante expansión. No obstante, la fusión radio-Internet hay que entenderla como una nueva forma de comunicación y no exclusivamente como un soporte exclusivamente complementario. En este contexto resulta de gran interés analizar qué transformaciones en cuanto al modo de recepción, contenidos, lenguajes, programas y programaciones, ha traído consigo para la radio dicha integración. Con este fin se toma como principal referencia los espacios deportivos, aspecto clave y de gran representatividad del actual panorama radiofónico. In english: 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.

  20. Comment on "Clouds and the Faint Young Sun Paradox" by Goldblatt and Zahnle (2011

    Directory of Open Access Journals (Sweden)

    R. Rondanelli

    2012-03-01

    Full Text Available Goldblatt and Zahnle (2011 raise a number of issues related to the possibility that cirrus clouds can provide a solution to the faint young sun paradox. Here, we argue that: (1 climates having a lower than present mean surface temperature cannot be discarded as solutions to the faint young sun paradox, (2 the detrainment from deep convective clouds in the tropics is a well-established physical mechanism for the formation of high clouds that have a positive radiative forcing (even if the possible role of these clouds as a negative climate feedback remains controversial and (3 even if some cloud properties are not mutually consistent with observations in radiative transfer parameterizations, the most relevant consistency (for the purpose of hypothesis testing is with observations of the cloud radiative forcing. Therefore, we maintain that cirrus clouds, as observed in the current climate and covering a large region of the tropics, can provide a solution to the faint young sun paradox, or at least ease the amount of CO2 or other greenhouse substances needed to provide temperatures above freezing during the Archean.

  1. Stellar populations in distant radio galaxies

    International Nuclear Information System (INIS)

    Lilly, S.J.; Longair, M.S.

    1984-01-01

    A homogeneous data set of infrared observations of 83 3CR galaxies with redshifts 0< z<1.6, selected from a statistically complete sample of 90 radio sources, is used to study the colours and magnitudes of these galaxies as a function of their redshifts. New infrared observations are presented for 66 radio galaxies, in addition to new optical results obtained from a re-analysis of existing CCD images. It is shown that the infrared colours do not deviate from the predicted relations with redshift for a standard giant elliptical galaxy spectrum. The optical to infrared colours, however, show substantial deviations at high redshift. No galaxies have been found that are significantly redder than a passively evolving galaxy, and there is a significant scatter of colours bluewards from this model. The excess of ultraviolet light responsible for these colours is not concentrated at the nucleus, and is interpreted as resulting from bursts of star formation, throughout the galaxy. (author)

  2. THE RADIO JET ASSOCIATED WITH THE MULTIPLE V380 ORI SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Luis F.; Yam, J. Omar; Carrasco-González, Carlos [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Anglada, Guillem [Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía, s/n, E-18008, Granada (Spain); Trejo, Alfonso, E-mail: l.rodriguez@crya.unam.mx [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)

    2016-10-01

    The giant Herbig–Haro object 222 extends over ∼6′ in the plane of the sky, with a bow shock morphology. The identification of its exciting source has remained uncertain over the years. A non-thermal radio source located at the core of the shock structure was proposed to be the exciting source. However, Very Large Array studies showed that the radio source has a clear morphology of radio galaxy and a lack of flux variations or proper motions, favoring an extragalactic origin. Recently, an optical–IR study proposed that this giant HH object is driven by the multiple stellar system V380 Ori, located about 23′ to the SE of HH 222. The exciting sources of HH systems are usually detected as weak free–free emitters at centimeter wavelengths. Here, we report the detection of an elongated radio source associated with the Herbig Be star or with its close infrared companion in the multiple V380 Ori system. This radio source has the characteristics of a thermal radio jet and is aligned with the direction of the giant outflow defined by HH 222 and its suggested counterpart to the SE, HH 1041. We propose that this radio jet traces the origin of the large scale HH outflow. Assuming that the jet arises from the Herbig Be star, the radio luminosity is a few times smaller than the value expected from the radio–bolometric correlation for radio jets, confirming that this is a more evolved object than those used to establish the correlation.

  3. THE RADIO JET ASSOCIATED WITH THE MULTIPLE V380 ORI SYSTEM

    International Nuclear Information System (INIS)

    Rodríguez, Luis F.; Yam, J. Omar; Carrasco-González, Carlos; Anglada, Guillem; Trejo, Alfonso

    2016-01-01

    The giant Herbig–Haro object 222 extends over ∼6′ in the plane of the sky, with a bow shock morphology. The identification of its exciting source has remained uncertain over the years. A non-thermal radio source located at the core of the shock structure was proposed to be the exciting source. However, Very Large Array studies showed that the radio source has a clear morphology of radio galaxy and a lack of flux variations or proper motions, favoring an extragalactic origin. Recently, an optical–IR study proposed that this giant HH object is driven by the multiple stellar system V380 Ori, located about 23′ to the SE of HH 222. The exciting sources of HH systems are usually detected as weak free–free emitters at centimeter wavelengths. Here, we report the detection of an elongated radio source associated with the Herbig Be star or with its close infrared companion in the multiple V380 Ori system. This radio source has the characteristics of a thermal radio jet and is aligned with the direction of the giant outflow defined by HH 222 and its suggested counterpart to the SE, HH 1041. We propose that this radio jet traces the origin of the large scale HH outflow. Assuming that the jet arises from the Herbig Be star, the radio luminosity is a few times smaller than the value expected from the radio–bolometric correlation for radio jets, confirming that this is a more evolved object than those used to establish the correlation.

  4. Application of Digital Cellular Radio for Mobile Location Estimation

    Directory of Open Access Journals (Sweden)

    Farhat Anwar

    2012-08-01

    Full Text Available The capability to locate the position of mobiles is a prerequisite to implement a wide range of evolving ITS services. Radiolocation has the potential to serve a wide geographical area. This paper reports an investigation regarding the feasibility of utilizing cellular radio for the purpose of mobile location estimation. Basic strategies to be utilized for location estimation are elaborated. Two possible approaches for cellular based location estimation are investigated with the help of computer simulation. Their effectiveness and relative merits and demerits are identified. An algorithm specifically adapted for cellular environment is reported with specific features where mobiles, irrespective of their numbers, can locate their position without adversely loading the cellular system.Key Words: ITS, GSM, Cellular Radio, DRGS, GPS.

  5. 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.

  6. Primordial black holes as dark matter: constraints from compact ultra-faint dwarfs

    Science.gov (United States)

    Zhu, Qirong; Vasiliev, Eugene; Li, Yuexing; Jing, Yipeng

    2018-05-01

    The ground-breaking detections of gravitational waves from black hole mergers by LIGO have rekindled interest in primordial black holes (PBHs) and the possibility of dark matter being composed of PBHs. It has been suggested that PBHs of tens of solar masses could serve as dark matter candidates. Recent analytical studies demonstrated that compact ultra-faint dwarf galaxies can serve as a sensitive test for the PBH dark matter hypothesis, since stars in such a halo-dominated system would be heated by the more massive PBHs, their present-day distribution can provide strong constraints on PBH mass. In this study, we further explore this scenario with more detailed calculations, using a combination of dynamical simulations and Bayesian inference methods. The joint evolution of stars and PBH dark matter is followed with a Fokker-Planck code PHASEFLOW. We run a large suite of such simulations for different dark matter parameters, then use a Markov chain Monte Carlo approach to constrain the PBH properties with observations of ultra-faint galaxies. We find that two-body relaxation between the stars and PBH drives up the stellar core size, and increases the central stellar velocity dispersion. Using the observed half-light radius and velocity dispersion of stars in the compact ultra-faint dwarf galaxies as joint constraints, we infer that these dwarfs may have a cored dark matter halo with the central density in the range of 1-2 M⊙pc - 3, and that the PBHs may have a mass range of 2-14 M⊙ if they constitute all or a substantial fraction of the dark matter.

  7. Herschel-PACS photometry of faint stars for sensitivity performance assessment and establishment of faint FIR primary photometric standards

    Science.gov (United States)

    Klaas, U.; Balog, Z.; Nielbock, M.; Müller, T. G.; Linz, H.; Kiss, Cs.

    2018-05-01

    Aims: Our aims are to determine flux densities and their photometric accuracy for a set of seventeen stars that range in flux from intermediately bright (≲2.5 Jy) to faint (≳5 mJy) in the far-infrared (FIR). We also aim to derive signal-to-noise dependence with flux and time, and compare the results with predictions from the Herschel exposure-time calculation tool. Methods: We obtain aperture photometry from Herschel-PACS high-pass-filtered scan maps and chop/nod observations of the faint stars. The issues of detection limits and sky confusion noise are addressed by comparison of the field-of-view at different wavelengths, by multi-aperture photometry, by special processing of the maps to preserve extended emission, and with the help of large-scale absolute sky brightness maps from AKARI. This photometry is compared with flux-density predictions based on photospheric models for these stars. We obtain a robust noise estimate by fitting the flux distribution per map pixel histogram for the area around the stars, scaling it for the applied aperture size and correcting for noise correlation. Results: For 15 stars we obtain reliable photometry in at least one PACS filter, and for 11 stars we achieve this in all three PACS filters (70, 100, 160 μm). Faintest fluxes, for which the photometry still has good quality, are about 10-20 mJy with scan map photometry. The photometry of seven stars is consistent with models or flux predictions for pure photospheric emission, making them good primary standard candidates. Two stars exhibit source-intrinsic far-infrared excess: β Gem (Pollux), being the host star of a confirmed Jupiter-size exoplanet, due to emission of an associated dust disk, and η Dra due to dust emission in a binary system with a K1 dwarf. The investigation of the 160 μm sky background and environment of four sources reveals significant sky confusion prohibiting the determination of an accurate stellar flux at this wavelength. As a good model

  8. AN IMAGING STUDY OF A COMPLEX SOLAR CORONAL RADIO ERUPTION

    Energy Technology Data Exchange (ETDEWEB)

    Feng, S. W.; Chen, Y.; Song, H. Q.; Wang, B.; Kong, X. L., E-mail: yaochen@sdu.edu.cn [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, and Institute of Space Sciences, Shandong University, Weihai, Shandong 264209 (China)

    2016-08-10

    Solar coronal radio bursts are enhanced radio emission excited by energetic electrons accelerated during solar eruptions. Studying these bursts is important for investigating the origin and physical mechanism of energetic particles and further diagnosing coronal parameters. Earlier studies suffered from a lack of simultaneous high-quality imaging data of the radio burst and the eruptive structure in the inner corona. Here we present a study on a complex solar radio eruption consisting of a type II burst and three reversely drifting type III bursts, using simultaneous EUV and radio imaging data. It is found that the type II burst is closely associated with a propagating and evolving CME-driven EUV shock structure, originated initially at the northern shock flank and later transferred to the top part of the shock. This source transfer is coincident with the presence of shock decay and enhancing signatures observed at the corresponding side of the EUV front. The electron energy accelerated by the shock at the flank is estimated to be ∼0.3 c by examining the imaging data of the fast-drifting herringbone structure of the type II burst. The reverse-drifting type III sources are found to be within the ejecta and correlated with a likely reconnection event therein. The implications for further observational studies and relevant space weather forecasting techniques are discussed.

  9. Astronomers Win Protection for Key Part of Radio Spectrum

    Science.gov (United States)

    2000-06-01

    Astronomers using the millimeter-wave region of the radio spectrum have won crucial protection for their science. Dedicated allocations for radio astronomy have been given final approval by the 2,500 delegates to the World Radiocommunication Conference (WRC-00), which recently concluded a month of deliberations in Istanbul, Turkey. Radio services can transmit in these parts of the spectrum as long as they don't hinder astronomers' attempts to catch faint signals from the cosmos. The new allocations represent the culmination of more than three years of cooperative planning by radio astronomers in many countries. Millimeter waves -- high-frequency radio waves -- have come of age as an astronomical tool in the last ten years. They are one of the last technological frontiers for astronomers. WRC-00 has protected for science all the frequencies between 71 and 275 Gigahertz (GHz) that radio astronomers currently use, adding more than 90 GHz of spectrum to the 44 GHz already set aside in this frequency range. As a result, radio astronomy is now allocated most of the frequencies between 71 and 275 GHz that can get through the Earth's atmosphere. "We have formal access to all three atmospheric 'windows', apart from their very edges," said Dr. Tom Gergely of the National Science Foundation, one of the U.S. delegates to WRC-00. The WRC also changed most of the frequencies allocated to satellite downlinks within the 71-275 GHz range to frequencies not used for science. Since no satellites yet operate at these high frequencies, no equipment needs to be altered. "Commercial technologies are just starting to develop above 50 GHz," said Dr. Klaus Ruf, Chairman of the Inter-Union Commission for the Allocation of Frequencies. "The WRC's actions mean that, when they are, radio astronomers should be able to share this part of the spectrum with most terrestrial services." The World Radiocommunication Conference is held every two or three years. Here member countries of the

  10. 3C 220.3: A radio galaxy lensing a submillimeter galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Haas, Martin; Westhues, Christian; Chini, Rolf [Astronomisches Institut, Ruhr Universität, Bochum (Germany); Leipski, Christian; Klaas, Ulrich; Meisenheimer, Klaus [Max-Planck-Institut für Astronomie, Heidelberg (Germany); Barthel, Peter; Koopmans, Léon V. E. [Kapteyn Astronomical Institute, University of Groningen (Netherlands); Wilkes, Belinda J.; Bussmann, R. Shane; Willner, S. P.; Ashby, Matthew L. N.; Kuraszkiewicz, Joanna [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States); Vegetti, Simona [Max-Planck-Institut für Astrophysik, Garching (Germany); Clements, David L. [Imperial College, London (United Kingdom); Fassnacht, Christopher D. [University of California, Davis, CA (United States); Horesh, Assaf [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA (United States); Lagattuta, David J. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn (Australia); Stern, Daniel; Wylezalek, Dominika, E-mail: haas@astro.rub.de [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (United States)

    2014-07-20

    Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z = 2.221. At an observed wavelength of 1 mm, the SMG is lensed into three distinct images. In the observed near infrared, these images are connected by an arc of ∼1''.8 radius forming an Einstein half-ring centered near the radio galaxy. In visible light, only the arc is apparent. 3C 220.3 is the only known instance of strong galaxy-scale lensing by a PRG not located in a galaxy cluster and therefore it offers the potential to probe the dark matter content of the radio galaxy host. Lens modeling rejects a single lens, but two lenses centered on the radio galaxy host A and a companion B, separated by 1''.5, provide a fit consistent with all data and reveal faint candidates for the predicted fourth and fifth images. The model does not require an extended common dark matter halo, consistent with the absence of extended bright X-ray emission on our Chandra image. The projected dark matter fractions within the Einstein radii of A (1''.02) and B (0''.61) are about 0.4 ± 0.3 and 0.55 ± 0.3. The mass to i-band light ratios of A and B, M/L{sub i}∼8±4 M{sub ⊙} L{sub ⊙}{sup −1}, appear comparable to those of radio-quiet lensing galaxies at the same redshift in the CfA-Arizona Space Telescope LEns Survey, Lenses Structure and Dynamics, and Strong Lenses in the Legacy Survey samples. The lensed SMG is extremely bright with observed f(250 μm) = 440 mJy owing to a magnification factor μ ∼ 10. The SMG spectrum shows luminous, narrow C IV λ1549 Å emission, revealing that the SMG houses a hidden quasar in addition to a violent starburst. Multicolor image reconstruction of the SMG indicates a bipolar morphology of the emitted ultraviolet (UV) light suggestive of cones through which UV light escapes a

  11. 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

  12. Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

    Science.gov (United States)

    Wheeler, Coral; Oñorbe, Jose; Bullock, James S.; Boylan-Kolchin, Michael; Elbert, Oliver D.; Garrison-Kimmel, Shea; Hopkins, Philip F.; Kereš, Dušan

    2015-10-01

    We present Feedback in Realistic Environment (FIRE)/GIZMO hydrodynamic zoom-in simulations of isolated dark matter haloes, two each at the mass of classical dwarf galaxies (Mvir ≃ 1010 M⊙) and ultra-faint galaxies (Mvir ≃ 109 M⊙), and with two feedback implementations. The resulting central galaxies lie on an extrapolated abundance matching relation from M⋆ ≃ 106 to 104 M⊙ without a break. Every host is filled with subhaloes, many of which form stars. Each of our dwarfs with M⋆ ≃ 106 M⊙ has 1-2 well-resolved satellites with M⋆ = 3-200 × 103 M⊙. Even our isolated ultra-faint galaxies have star-forming subhaloes. If this is representative, dwarf galaxies throughout the Universe should commonly host tiny satellite galaxies of their own. We combine our results with the Exploring the Local Volume in Simulations (ELVIS) simulations to show that targeting ˜ 50 kpc regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by ˜35 per cent compared to random pointings, and specifically identify the region around the Phoenix dwarf galaxy as a good potential target. The well-resolved ultra-faint galaxies in our simulations (M⋆ ≃ 3-30 × 103 M⊙) form within Mpeak ≃ 0.5-3 × 109 M⊙ haloes. Each has a uniformly ancient stellar population ( > 10 Gyr) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that Mhalo ≃ 5 × 109 M⊙ is a probable dividing line between haloes hosting reionization `fossils' and those hosting dwarfs that can continue to form stars in isolation after reionization.

  13. Monte Carlo simulations of radio pulsars and their progenitors

    International Nuclear Information System (INIS)

    Dewey, R.J.; Cordes, J.M.

    1987-01-01

    Standard models of binary evolution were applied to a model of the main-sequence population to trace the paths by which a massive star may evolve into a neutron star. Using three different models of binary evolution, the relative number of neutron stars formed by each path was calculated. It was found that none of the models were able to reproduce both the observed velocity distribution of radio pulsars and the observed incidence of binary pulsars. 59 references

  14. Ultrahigh-energy Cosmic Rays from Fanaroff Riley class II radio galaxies

    Science.gov (United States)

    Rachen, Joerg; Biermann, Peter L.

    1992-08-01

    The hot spots of very powerful radio galaxies (Fanaroff Riley class II) are argued to be the sources of the ultrahigh energy component in Cosmic Rays. We present calculations of Cosmic Ray transport in an evolving universe, taking the losses against the microwave background properly into account. As input we use the models for the cosmological radio source evolution derived by radioastronomers (mainly Peacock 1985). The model we adopt for the acceleration in the radio hot spots has been introduced by Biermann and Strittmatter (1987), and Meisenheimer et al. (1989) and is based on first order Fermi theory of particle acceleration at shocks (see, e.g., Drury 1983). As an unknown the actual proportion of energy density in protons enters, which together with structural uncertainties in the hot spots should introduce no more than one order of magnitude in uncertainty: We easily reproduce the observed spectra of high energy cosmic rays. It follows that scattering of charged energetic particles in intergalactic space must be sufficiently small in order to obtain contributions from sources as far away as even the nearest Fanaroff Riley class II radio galaxies. This implies a strong constraint on the turbulent magnetic field in intergalactic space.

  15. LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

    Science.gov (United States)

    Heesen, V.; Croston, J. H.; Morganti, R.; Hardcastle, M. J.; Stewart, A. J.; Best, P. N.; Broderick, J. W.; Brüggen, M.; Brunetti, G.; ChyŻy, K. T.; Harwood, J. J.; Haverkorn, M.; Hess, K. M.; Intema, H. T.; Jamrozy, M.; Kunert-Bajraszewska, M.; McKean, J. P.; Orrú, E.; Röttgering, H. J. A.; Shimwell, T. W.; Shulevski, A.; White, G. J.; Wilcots, E. M.; Williams, W. L.

    2018-03-01

    We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1 Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensities with advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v∝rβ (β ≈ -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find self-consistent solutions in agreement with the entrainment model of Croston & Hardcastle, where the magnetic field provides ≈1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ≈190 Myr, which, if equated to the source age, would require an average expansion Mach number M ≈ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales.

  16. Four Decades of Space-Borne Radio Sounding

    Science.gov (United States)

    Benson, Robert F.

    2010-01-01

    A review is given of the 38 rocket, satellite, and planetary payloads dedicated to ionospheric/magnetospheric radio sounding since 1961. Between 1961 and 1995, eleven sounding-rocket payloads from four countries evolved from proof-of-concept flights to sophisticated instruments. Some involved dual payloads, with the sounder transmitter on one and the sounder receiver on the other. The rocket sounders addressed specific space-plasma-wave questions, and provided improved measurements of ionospheric electron-density (N(sub e)) field-aligned irregularities (FAI). Four countries launched 12 ionospheric topside-sounder satellites between 1962 and 1994, and an ionospheric sounder was placed on the Mir Space Station in 1998. Eleven magnetospheric radio sounders, most of the relaxation type, were launched from 1977 to 2000. The relaxation sounders used low-power transmitters, designed to stimulate plasma resonances for accurate local Ne determinations. The latest magnetospheric sounder designed for remote sensing incorporated long antennas and digital signal processing techniques to overcome the challenges posed by low Ne values and large propagation distances. Three radio sounders from three countries were included on payloads to extraterrestrial destinations from 1990 to 2003. The scientific accomplishments of space-borne radio sounders included (1) a wealth of global N(sub e) information on the topside ionosphere and magnetosphere, based on vertical and magnetic-field-aligned N(sub e) profiles; (2) accurate in-situ N(sub e) values, even under low-density conditions; and (3) fundamental advances in our understanding of the excitation and propagation of plasma waves, which have even led to the prediction of a new plasma-wave mode.

  17. Genetic programming applied to RFI mitigation in radio astronomy

    Science.gov (United States)

    Staats, K.

    2016-12-01

    Genetic Programming is a type of machine learning that employs a stochastic search of a solutions space, genetic operators, a fitness function, and multiple generations of evolved programs to resolve a user-defined task, such as the classification of data. At the time of this research, the application of machine learning to radio astronomy was relatively new, with a limited number of publications on the subject. Genetic Programming had never been applied, and as such, was a novel approach to this challenging arena. Foundational to this body of research, the application Karoo GP was developed in the programming language Python following the fundamentals of tree-based Genetic Programming described in "A Field Guide to Genetic Programming" by Poli, et al. Karoo GP was tasked with the classification of data points as signal or radio frequency interference (RFI) generated by instruments and machinery which makes challenging astronomers' ability to discern the desired targets. The training data was derived from the output of an observation run of the KAT-7 radio telescope array built by the South African Square Kilometre Array (SKA-SA). Karoo GP, kNN, and SVM were comparatively employed, the outcome of which provided noteworthy correlations between input parameters, the complexity of the evolved hypotheses, and performance of raw data versus engineered features. This dissertation includes description of novel approaches to GP, such as upper and lower limits to the size of syntax trees, an auto-scaling multiclass classifier, and a Numpy array element manager. In addition to the research conducted at the SKA-SA, it is described how Karoo GP was applied to fine-tuning parameters of a weather prediction model at the South African Astronomical Observatory (SAAO), to glitch classification at the Laser Interferometer Gravitational-wave Observatory (LIGO), and to astro-particle physics at The Ohio State University.

  18. 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

  19. CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Casey, Andrew R., E-mail: alexji@mit.edu [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)

    2016-11-20

    We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼ 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.

  20. CHEMICAL DIVERSITY IN THE ULTRA-FAINT DWARF GALAXY TUCANA II

    International Nuclear Information System (INIS)

    Ji, Alexander P.; Frebel, Anna; Ezzeddine, Rana; Casey, Andrew R.

    2016-01-01

    We present the first detailed chemical abundance study of the ultra-faint dwarf galaxy Tucana II, based on high-resolution Magellan/MIKE spectra of four red giant stars. The metallicities of these stars range from [Fe/H] = −3.2 to −2.6, and all stars are low in neutron-capture abundances ([Sr/Fe] and [Ba/Fe] < −1). However, a number of anomalous chemical signatures are present. One star is relatively metal-rich ([Fe/H] = −2.6) and shows [Na, α , Sc/Fe] < 0, suggesting an extended star formation history with contributions from AGB stars and SNe Ia. Two stars with [Fe/H] < −3 are mildly carbon-enhanced ([C/Fe] ∼ 0.7) and may be consistent with enrichment by faint supernovae, if such supernovae can produce neutron-capture elements. A fourth star with [Fe/H] = −3 is carbon-normal, and exhibits distinct light element abundance ratios from the carbon-enhanced stars. This carbon-normal star implies that at least two distinct nucleosynthesis sources, both possibly associated with Population III stars, contributed to the early chemical enrichment of this galaxy. Despite its very low luminosity, Tucana II shows a diversity of chemical signatures that preclude it from being a simple “one-shot” first galaxy yet still provide a window into star and galaxy formation in the early universe.

  1. A Tool for Optimizing Observation Planning for Faint Moving Objects

    Science.gov (United States)

    Arredondo, Anicia; Bosh, Amanda S.; Levine, Stephen

    2016-10-01

    Observations of small solar system bodies such as trans-Neptunian objects and Centaurs are vital for understanding the basic properties of these small members of our solar system. Because these objects are often very faint, large telescopes and long exposures may be necessary, which can result in crowded fields in which the target of interest may be blended with a field star. For accurate photometry and astrometry, observations must be planned to occur when the target is free of background stars; this restriction results in limited observing windows. We have created a tool that can be used to plan observations of faint moving objects. Features of the tool include estimates of best times to observe (when the object is not too near another object), a finder chart output, a list of possible astrometric and photometric reference stars, and an exposure time calculator. This work makes use of the USNOFS Image and Catalogue Archive operated by the United States Naval Observatory, Flagstaff Station (S.E. Levine and D.G. Monet 2000), the JPL Horizons online ephemeris service (Giorgini et al. 1996), the Minor Planet Center's MPChecker (http://cgi.minorplanetcenter.net/cgi-bin/checkmp.cgi), and source extraction software SExtractor (Bertin & Arnouts 1996). Support for this work was provided by NASA SSO grant NNX15AJ82G.

  2. The significance of faint visualization of the superior sagittal sinus in brain scintigraphy for the diagnosis of brain death

    International Nuclear Information System (INIS)

    Bisset, R.; Sfakianakis, G.; Ihmedian, I.; Holzman, B.; Curless, R.; Serafini, A.

    1985-01-01

    Brain death is associated with cessation of blood flow to the brain. Tc-99m brain flow studies are used as a laboratory confirmatory test for the establishment of the diagnosis of brain death. Criteria for the diagnosis of cessation of blood flow to the brain are 1) visualization of carotid artery activity in the neck of the patient and 2) no visualization of activity in the distribution of the anterior and middle cerebral arteries. The authors noticed that in a significant number of patients, although there was no visualization of arterial blood flow to the brain the static images demonstrated faint accumulation of activity in the region of the superior sagittal sinus (SSS). In a four year period 212 brain flow studies were performed in 154 patients for diagnosis of brain death; of them 137 studies (65%) showed no evidence of arterial flow. In 103 out of the 137 studies (75%) there was no visualization of the SSS; in the remaining 34 studies (3l patients) however three patterns of faint activity attributed to partial and or faint visualization of the SSS could be recognized at the midline of the immediate anterior static view: a) linear from the cranial vault floor up b) disk shaped at the apex of the vault and c) disk shaped at the apex tailing caudad. All of the 3l patients in this group satisfied brain death criteria within four days of the last study which showed faint visualization of the superior sagittal sinus. The authors conclude that even in the presence of a faint visualization of the superior sagittal sinus on static post brain flow scintigraphy, the diagnosis of cessation of blood flow to the brain can be made if there is no evidence of arterial blood flow

  3. Galaxy modelling. II. Multi-wavelength faint counts from a semi-analytic model of galaxy formation

    Science.gov (United States)

    Devriendt, J. E. G.; Guiderdoni, B.

    2000-11-01

    This paper predicts self-consistent faint galaxy counts from the UV to the submm wavelength range. The stardust spectral energy distributions described in Devriendt et al. \\citeparyear{DGS99} (Paper I) are embedded within the explicit cosmological framework of a simple semi-analytic model of galaxy formation and evolution. We begin with a description of the non-dissipative and dissipative collapses of primordial perturbations, and plug in standard recipes for star formation, stellar evolution and feedback. We also model the absorption of starlight by dust and its re-processing in the IR and submm. We then build a class of models which capture the luminosity budget of the universe through faint galaxy counts and redshift distributions in the whole wavelength range spanned by our spectra. In contrast with a rather stable behaviour in the optical and even in the far-IR, the submm counts are dramatically sensitive to variations in the cosmological parameters and changes in the star formation history. Faint submm counts are more easily accommodated within an open universe with a low value of Omega_0 , or a flat universe with a non-zero cosmological constant. We confirm the suggestion of Guiderdoni et al. \\citeparyear{GHBM98} that matching the current multi-wavelength data requires a population of heavily-extinguished, massive galaxies with large star formation rates ( ~ 500 M_sun yr-1) at intermediate and high redshift (z >= 1.5). Such a population of objects probably is the consequence of an increase of interaction and merging activity at high redshift, but a realistic quantitative description can only be obtained through more detailed modelling of such processes. This study illustrates the implementation of multi-wavelength spectra into a semi-analytic model. In spite of its simplicity, it already provides fair fits of the current data of faint counts, and a physically motivated way of interpolating and extrapolating these data to other wavelengths and fainter flux

  4. MULTI-FREQUENCY STUDIES OF RADIO RELICS IN THE GALAXY CLUSTERS A4038, A1664, AND A786

    Energy Technology Data Exchange (ETDEWEB)

    Kale, Ruta; Dwarakanath, K. S., E-mail: ruta@iucaa.ernet.in [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560 080 (India)

    2012-01-01

    We present a multi-frequency study of radio relics associated with the galaxy clusters A4038, A1664, and A786. Radio images, integrated spectra, spectral index maps, and fits to the integrated spectra in the framework of the adiabatic compression model are presented. Images of the relic in A4038 at 150, 240, and 606 MHz with the Giant Meterwave Radio Telescope have revealed extended ultra-steep spectrum ({alpha} {approx} -1.8 to -2.7) emission of extent 210 Multiplication-Sign 80 kpc{sup 2}. The model of passively evolving radio lobes compressed by a shock fits the integrated spectrum best. The relic with a circular morphology at the outskirts of the cluster A1664 has an integrated spectral index of {approx} - 1.10 {+-} 0.06 and is best fit by the model of radio lobes lurking for {approx}4 Multiplication-Sign 10{sup 7} yr. The relic near A786 has a curved spectrum and is best fit by a model of radio lobes lurking for {approx}3 Multiplication-Sign 10{sup 7} yr. At 4.7 GHz, a compact radio source, possibly the progenitor of the A786 relic, is detected near the center of the radio relic. The A786 radio relic is thus likely a lurking radio galaxy rather than a site of cosmological shock as has been considered in earlier studies.

  5. 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.

  6. The Faint Optical Afterglow and Host Galaxy of GRB 020124: Implications for the Nature of Dark Gamma-Ray Bursts

    Science.gov (United States)

    Berger, E.; Kulkarni, S. R.; Bloom, J. S.; Price, P. A.; Fox, D. W.; Frail, D. A.; Axelrod, T. S.; Chevalier, R. A.; Colbert, E.; Costa, E.; Djorgovski, S. G.; Frontera, F.; Galama, T. J.; Halpern, J. P.; Harrison, F. A.; Holtzman, J.; Hurley, K.; Kimble, R. A.; McCarthy, P. J.; Piro, L.; Reichart, D.; Ricker, G. R.; Sari, R.; Schmidt, B. P.; Wheeler, J. C.; Vanderppek, R.; Yost, S. A.

    2002-12-01

    We present ground-based optical observations of GRB 020124 starting 1.6 hr after the burst, as well as subsequent Very Large Array and Hubble Space Telescope (HST) observations. The optical afterglow of GRB 020124 is one of the faintest afterglows detected to date, and it exhibits a relatively rapid decay, Fν~t-1.60+/-0.04, followed by further steepening. In addition, a weak radio source was found coincident with the optical afterglow. The HST observations reveal that a positionally coincident host galaxy must be the faintest host to date, R>~29.5 mag. The afterglow observations can be explained by several models requiring little or no extinction within the host galaxy, AhostV~0-0.9 mag. These observations have significant implications for the interpretation of the so-called dark bursts (bursts for which no optical afterglow is detected), which are usually attributed to dust extinction within the host galaxy. The faintness and relatively rapid decay of the afterglow of GRB 020124, combined with the low inferred extinction, indicate that some dark bursts are intrinsically dim and not dust obscured. Thus, the diversity in the underlying properties of optical afterglows must be observationally determined before substantive inferences can be drawn from the statistics of dark bursts.

  7. Hubble Space Telescope: Faint object spectrograph instrument handbook. Version 1.1

    Science.gov (United States)

    Ford, Holland C. (Editor)

    1990-01-01

    The Faint Object Spectrograph (FOS) has undergone substantial rework since the 1985 FOS Instrument Handbook was published, and we are now more knowledgeable regarding the spacecraft and instrument operations requirements and constraints. The formal system for observation specification has also evolved considerably, as the GTO programs were defined in detail. This supplement to the FOS Instrument Handbook addresses the important aspects of these changes, to facilitate proper selection and specification of FOS observing programs. Since the Handbook was published, the FOS red detector has been replaced twice, first with the best available spare in 1985 (which proved to have a poor, and steadily degrading red response), and later with a newly developed Digicon, which exhibits a high, stable efficiency and a dark-count rate less than half that of its predecessors. Also, the FOS optical train was realigned in 1987-88 to eliminate considerable beam-vignetting losses, and the collimators were both removed and recoated for greater reflectivity. Following the optics and detector rework, the FOS was carefully recalibrated (although only ambient measurements were possible, so the far-UV characteristics could not be re-evaluated directly). The resulting efficiency curves, including improved estimates of the telescope throughput, are shown. A number of changes in the observing-mode specifications and addition of several optional parameters resulted as the Proposal Instructions were honed during the last year. Target-brightness limitations, which have only recently been formulated carefully, are described. Although these restrictions are very conservative, it is imperative that the detector safety be guarded closely, especially during the initial stages of flight operations. Restrictions on the use of the internal calibration lamps and aperture-illumination sources (TA LEDs), also resulting from detector safety considerations, are outlined. Finally, many changes have been made to

  8. A CHANDRA SURVEY OF THE X-RAY PROPERTIES OF BROAD ABSORPTION LINE RADIO-LOUD QUASARS

    International Nuclear Information System (INIS)

    Miller, B. P.; Brandt, W. N.; Garmire, G. P.; Gibson, R. R.; Shemmer, O.

    2009-01-01

    This work presents the results of a Chandra study of 21 broad absorption line (BAL) radio-loud quasars (RLQs). We conducted a Chandra snapshot survey of 12 bright BAL RLQs selected from Sloan Digital Sky Survey Data/Faint Images of the Radio Sky data and possessing a wide range of radio and C IV absorption properties. Optical spectra were obtained nearly contemporaneously with the Hobby-Eberly Telescope; no strong flux or BAL variability was seen between epochs. In addition to the snapshot targets, we include in our sample nine additional BAL RLQs possessing archival Chandra coverage. We compare the properties of (predominantly high-ionization) BAL RLQs to those of non-BAL RLQs as well as to BAL radio-quiet quasars (RQQs) and non-BAL RQQs for context. All 12 snapshots and 8/9 archival BAL RLQs are detected, with observed X-ray luminosities less than those of non-BAL RLQs having comparable optical/UV luminosities by typical factors of 4.1-8.5. (BAL RLQs are also X-ray weak by typical factors of 2.0-4.5 relative to non-BAL RLQs having both comparable optical/UV and radio luminosities.) However, BAL RLQs are not as X-ray weak relative to non-BAL RLQs as are BAL RQQs relative to non-BAL RQQs. While some BAL RLQs have harder X-ray spectra than typical non-BAL RLQs, some have hardness ratios consistent with those of non-BAL RLQs, and there does not appear to be a correlation between X-ray weakness and spectral hardness, in contrast to the situation for BAL RQQs. RLQs are expected to have X-ray continuum contributions from both accretion-disk corona and small-scale jet emission. While the entire X-ray continuum in BAL RLQs cannot be obscured to the same degree as in BAL RQQs, we calculate that the jet is likely partially covered in many BAL RLQs. We comment briefly on implications for geometries and source ages in BAL RLQs.

  9. 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.

  10. On the Nature of Ultra-faint Dwarf Galaxy Candidates. II. The Case of Cetus II

    Science.gov (United States)

    Conn, Blair C.; Jerjen, Helmut; Kim, Dongwon; Schirmer, Mischa

    2018-04-01

    We obtained deep Gemini GMOS-S g, r photometry of the ultra-faint dwarf galaxy candidate Cetus II with the aim of providing stronger constraints on its size, luminosity, and stellar population. Cetus II is an important object in the size–luminosity plane, as it occupies the transition zone between dwarf galaxies and star clusters. All known objects smaller than Cetus II (r h ∼ 20 pc) are reported to be star clusters, while most larger objects are likely dwarf galaxies. We found a prominent excess of main-sequence stars in the color–magnitude diagram of Cetus II, best described by a single stellar population with an age of 11.2 Gyr, metallicity of [Fe/H] = ‑1.28 dex, an [α/Fe] = 0.0 dex at a heliocentric distance of 26.3 ± 1.2 kpc. As well as being spatially located within the Sagittarius dwarf tidal stream, these properties are well matched to the Sagittarius galaxy’s Population B stars. Interestingly, like our recent findings on the ultra-faint dwarf galaxy candidate Tucana V, the stellar field in the direction of Cetus II shows no evidence of a concentrated overdensity despite tracing the main sequence for over six magnitudes. These results strongly support the picture that Cetus II is not an ultra-faint stellar system in the Milky Way halo, but made up of stars from the Sagittarius tidal stream.

  11. 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.)

  12. The Luminosity Function of Fermi-Detected Flat-Spectrum Radio Quasars

    Science.gov (United States)

    2012-05-11

    extensively studied at radio (Dunlop & Peacock 1990; Wall et al. 2005), soft X-ray (Giommi & Padovani 1994; Rector et al. 2000; Wolter & Celotti 2001...FSRQs) evolve positively (i.e., there were more blazars in the past, Dunlop & Peacock 1990) up to a redshift cutoff which depends on luminosity (e.g...luminosity of 1048 erg s−1. The LDDE model provides a good fit to the LAT data and is able to reproduce the observed distribution in Figure 2. The log

  13. New light on faint stars

    International Nuclear Information System (INIS)

    Reid, N.; Gilmore, G.

    1982-01-01

    This paper presents the first purely photometric derivation of the stellar main-sequence luminosity function to absolute magnitude Msub(V) = + 19, which is comparable to the minimum mass for thermonuclear burning. The observations consist of COSMOS measures of UK Schmidt telescope plates in the V, R and I bands. They provide a complete sample of every star in 18.24 square degrees towards the South Galactic Pole, brighter than I = 17.0. Absolute magnitudes and distances are derived by photometric parallax from the Msub(V)/V-I and Msub(V)/I-K relations, which have been carefully calibrated on our photometric system. For +9<=Msub(V)<=+19, the photometrically defined luminosity function is in agreement with that derived from samples of nearby stars, and by proper motion techniques. There is no evidence for any excess of intrinsically faint stars, even though this survey reaches some 5 mag deeper into the luminosity function than previous photometric surveys. Re-analysis of subsamples of other photometric studies of the local stellar density removes any evidence for a significant excess of M dwarfs relative to the kinematically derived luminosity function. The missing mass in the solar neighbourhood, if any, does not reside in main-sequence stars brighter than Msub(V) approx. = + 17 mag. (author)

  14. Detecting signatures of cosmological recombination and reionization in the cosmic radio background

    Science.gov (United States)

    Subrahmanyan, Ravi; Shankar Narayana Rao, Udaya; Sathyanarayana Rao, Mayuri; Singh, Saurabh

    2015-08-01

    Evolution of the baryons during the Epochs of cosmological Recombination and Reionization has left traces in the cosmic radio background in the form of spectral distortions (Sunyaev & Chluba 2008 Astron. Nachrichten, 330, 657; Pritchard & Loeb 2012 Rep Prog Phys 75(8):086901). The spectral signature depends on the evolution in the ionization state in hydrogen and helium and on the spin temperature of hydrogen. These probe the physics of energy release beyond the last scattering surface at redshifts exceeding 1090 and the nature of the first sources and gas evolution down to redshift about 6. The spectral distortions are sensitive to the nature of the first stars, ultra-dwarf galaxies, accreting compact objects, and the evolving ambient radiation field: X-rays and UV from the first sources. Detection of the all-sky or global spectral distortions in the radio background is hence a probe of cosmological recombination and reionization.We present new spectral radiometers that we have purpose designed for precision measurements of spectral distortions at radio wavelengths. New antenna elements include frequency independent and electrically small fat-dipole (Raghunathan et al. 2013 IEEE TAP, 61, 3411) and monopole designs. Receiver configurations have been devised that are self-calibratable (Patra et al. 2013 Expt Astron, 36, 319) so that switching of signal paths and of calibration noise sources provide real time calibration for systematics and receiver noise. Observing strategies (Patra et al. arXiv:1412.7762) and analysis methods (Satyanarayana Rao et al. arXiv:1501.07191) have been evolved that are capable of discriminating between the cosmological signals and the substantially brighter foregrounds. We have also demonstrated the value of system designs that exploit advantages of interferometer detection (Mahesh et al. arXiv:1406.2585) of global spectral distortions.Finally we discuss how the Square Kilometer Array stations may be outfitted with precision spectral

  15. 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.)

  16. HERA Broadband Feed Design for Low-Frequency Radio Astronomy

    Science.gov (United States)

    Garza, Sierra; Trung, Vincent; Ewall-Wice, Aaron Michael; Li, Jianshu; Hewitt, Jacqueline; Riley, Daniel; Bradley, Richard F.; Makhija, Krishna

    2018-01-01

    As part of the Hydrogen Epoch of Reionization Array (HERA) project, we are designing a broadband low-frequency radio feed to extend the bandwidth from 100-200 MHz to 50-220 MHz. By extending the lower-limit to 50 MHz, we hope to detect the signatures of the first black holes heating the hydrogen gas in the intergalactic medium.The isolation of a very faint signal from vastly brighter foregrounds sets strict requirements on antenna spectral smoothness, polarization purity, forward gain, and internal reflections. We are currently working to meet these requirements with a broad-band sinuous antenna feed suspended over the 14-m parabolic HERA dish, using a combination of measurements and simulations to verify the performance of our design.A sinuous feed has been designed and simulated with Computer Simulation Technology (CST) software. We will present the construction of a prototype sinuous antenna and measurements of its reflection coefficient, S11, including laboratory characterization of baluns. Our measurements agree well with the CST simulations of the antenna’s performance, giving us confidence in our ability to model the feed and ensure that it meets the requirements of a 21cm cosmology measurement.

  17. IRAS observations of radio-quiet and radio-loud quasars

    Science.gov (United States)

    Neugebauer, G.; Soifer, B. T.; Miley, G.; Habing, H. J.; Young, E.; Low, F. J.; Beichman, C. A.; Clegg, P. E.; Harris, S.; Rowan-Robinson, M.

    1984-01-01

    Observations from 12 to 100 microns are presented of two radio-quiet and three radio-loud quasars. Over this wavelength range, all five have grossly similar continuum energy distributions. The continua of the radio-loud quasars are consistent with synchrotron radiation. There is an indication, however, of excess 100 micron emission in the two radio-quiet quasars.

  18. Resolving the faint end of the satellite luminosity function for the nearest elliptical Centaurus A

    Science.gov (United States)

    Crnojevic, Denija

    2014-10-01

    We request HST/ACS imaging to follow up 15 new faint candidate dwarfs around the nearest elliptical Centaurus A (3.8 Mpc). The dwarfs were found via a systematic ground-based (Magellan/Megacam) survey out to ~150 kpc, designed to directly confront the "missing satellites" problem in a wholly new environment. Current Cold Dark Matter models for structure formation fail to reproduce the shallow slope of the satellite luminosity function in spiral-dominated groups for which dwarfs fainter than M_V<-14 have been surveyed (the Local Group and the nearby, interacting M81 group). Clusters of galaxies show a better agreement with cosmological predictions, suggesting an environmental dependence of the (poorly-understood) physical processes acting on the evolution of low mass galaxies (e.g., reionization). However, the luminosity function completeness for these rich environments quickly drops due to the faintness of the satellites and to the difficult cluster membership determination. We target a yet unexplored "intermediate" environment, a nearby group dominated by an elliptical galaxy, ideal due to its proximity: accurate (10%) distance determinations for its members can be derived from resolved stellar populations. The proposed observations of the candidate dwarfs will confirm their nature, group membership, and constrain their luminosities, metallicities, and star formation histories. We will obtain the first complete census of dwarf satellites of an elliptical down to an unprecedented M_V<-9. Our results will crucially constrain cosmological predictions for the faint end of the satellite luminosity function to achieve a more complete picture of the galaxy formation process.

  19. 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

  20. THE ORIGIN OF THE HEAVIEST METALS IN MOST ULTRA-FAINT DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Roederer, Ian U., E-mail: iur@umich.edu [Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109 (United States)

    2017-01-20

    The heaviest metals found in stars in most ultra-faint dwarf (UFD) galaxies in the Milky Way halo are generally underabundant by an order of magnitude or more when compared with stars in the halo field. Among the heavy elements produced by n -capture reactions, only Sr and Ba can be detected in red giant stars in most UFD galaxies. This limited chemical information is unable to identify the nucleosynthesis process(es) responsible for producing the heavy elements in UFD galaxies. Similar [Sr/Ba] and [Ba/Fe] ratios are found in three bright halo field stars, BD−18°5550, CS 22185–007, and CS 22891–200. Previous studies of high-quality spectra of these stars report detections of additional n -capture elements, including Eu. The [Eu/Ba] ratios in these stars span +0.41 to +0.86. These ratios and others among elements in the rare Earth domain indicate an r -process origin. These stars have some of the lowest levels of r -process enhancement known, with [Eu/H] spanning −3.95 to −3.32, and they may be considered nearby proxies for faint stars in UFD galaxies. Direct confirmation, however, must await future observations of additional heavy elements in stars in the UFD galaxies themselves.

  1. Radio Pulse Search and X-Ray Monitoring of SAX J1808.4−3658: What Causes Its Orbital Evolution?

    Energy Technology Data Exchange (ETDEWEB)

    Patruno, Alessandro; King, Andrew R. [Leiden Observatory, Leiden University, Neils Bohrweg 2, 2333 CA, Leiden (Netherlands); Jaodand, Amruta; Hessels, Jason W. T. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7900 AA, Dwingeloo (Netherlands); Kuiper, Lucien [SRON-National Institute for Space Research, Sorbonnelaan 2, NL-3584 CA, Utrecht (Netherlands); Bult, Peter; Wijnands, Rudy; Van der Klis, Michiel [Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam (Netherlands); Knigge, Christian [University of Southampton, School of Physics and Astronomy, Southampton SO17 1BJ (United Kingdom)

    2017-06-01

    The accreting millisecond X-ray pulsar SAX J1808.4−3658 shows a peculiar orbital evolution that proceeds at a very fast pace. It is important to identify the underlying mechanism responsible for this behavior because it can help to understand how this system evolves and which physical processes (such as mass loss or spin–orbit coupling) are occurring in the binary. It has also been suggested that, when in quiescence, SAX J1808.4−3658 turns on as a radio pulsar, a circumstance that might provide a link between accreting millisecond pulsars and black-widow (BW) radio pulsars. In this work, we report the results of a deep radio pulsation search at 2 GHz using the Green Bank Telescope in 2014 August and an X-ray study of the 2015 outburst with Chandra , Swift XRT, and INTEGRAL . In quiescence, we detect no radio pulsations and place the strongest limit to date on the pulsed radio flux density of any accreting millisecond pulsar. We also find that the orbit of SAX J1808.4−3658 continues evolving at a fast pace. We compare the orbital evolution of SAX J1808.4−3658 to that of several other accreting and nonaccreting binaries, including BWs, redbacks, cataclysmic variables, black holes, and neutron stars in low-mass X-ray binaries. We discuss two possible scenarios: either the neutron star has a large moment of inertia and is ablating the donor, generating mass loss with an efficiency of 40%, or the donor star has a strong magnetic field of at least 1 kG and is undergoing quasi-cyclic variations due to spin–orbit coupling.

  2. 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.

  3. Mass and environment as drivers of galaxy evolution. III. The constancy of the faint-end slope and the merging of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Ying-jie; Lilly, Simon J.; Carollo, Marcella [Institute of Astronomy, ETH Zurich, 8093 Zurich (Switzerland); Renzini, Alvio [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy)

    2014-08-01

    Using our continuity approach, we explore the underlying connections between the evolution of the faint-end slope α{sub s} of the stellar mass function of star-forming galaxies, the logarithmic slope β of the specific star formation rate (sSFR)-mass relation, and the merging of galaxies. We derive analytically the consequences of the observed constancy of α{sub s} since redshifts of at least z ∼ 2. If the logarithmic slope β of the sSFR-mass relation is negative, then the faint-end slope α{sub s} should quickly diverge due to the differential mass increase of galaxies on the star-forming main sequence, and this will also quickly destroy the Schechter form of the mass function. This problem can be solved by removing low-mass galaxies by merging them into more massive galaxies. We quantify this process by introducing the specific merger mass rate (sMMR) as the specific rate of mass added to a given galaxy through mergers. For a modest negative value of β ∼ –0.1, an average sMMR ∼ 0.1 sSFR across the population is required to keep α{sub s} constant with epoch, as observed. This in turn implies a merger rate of ∼0.2 sSFR for major mergers, which is consistent with the available observational estimates. More negative values of β require higher sMMR and higher merger rates, and the steepening of the mass function becomes impossible to control for β < –(α{sub s} + 2). The close link that is required between the in situ sSFR and the sMMR probably arises because both are closely linked to the buildup of dark matter halos. These new findings further develop the formalism for the evolving galaxy population that we introduced earlier and show how striking symmetries in the galaxy population can emerge as the result of deep links between the physical processes involved.

  4. 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

  5. Identification of faint central stars in extended, low-surface-brightness planetary nebulae

    International Nuclear Information System (INIS)

    Kwitter, K.B.; Lydon, T.J.; Jacoby, G.H.

    1988-01-01

    As part of a larger program to study the properties of planetary nebula central stars, a search for faint central stars in extended, low-surface-brightness planetary nebulae using CCD imaging is performed. Of 25 target nebulae, central star candidates have been identified in 17, with certainties ranging from extremely probable to possible. Observed V values in the central star candidates extend to fainter than 23 mag. The identifications are presented along with the resulting photometric measurements. 24 references

  6. The Evolution in the Faint-End Slope of the Quasar Luminosity Function

    OpenAIRE

    Hopkins, Philip F.; Hernquist, Lars; Cox, Thomas J.; Di Matteo, Tiziana; Robertson, Brant; Springel, Volker

    2005-01-01

    (Abridged) Based on numerical simulations of galaxy mergers that incorporate black hole (BH) growth, we predict the faint end slope of the quasar luminosity function (QLF) and its evolution with redshift. Our simulations have yielded a new model for quasar lifetimes where the lifetime depends on both the instantaneous and peak quasar luminosities. This motivates a new interpretation of the QLF in which the bright end consists of quasars radiating at nearly their peak luminosities, but the fai...

  7. MULTIFREQUENCY RADIO MEASUREMENTS OF SUPERNOVA 1987A OVER 22 YEARS

    International Nuclear Information System (INIS)

    Zanardo, G.; Staveley-Smith, L.; Potter, T. M.; Ball, Lewis; Kesteven, M. J.; Manchester, R. N.; Tzioumis, A. K.; Gaensler, B. M.; Ng, C.-Y.

    2010-01-01

    We present extensive observations of the radio emission from the remnant of supernova (SN) 1987A made with the Australia Telescope Compact Array (ATCA), since the first detection of the remnant in 1990. The radio emission has evolved in time providing unique information on the interaction of the SN shock with the circumstellar medium. We particularly focus on the monitoring observations at 1.4, 2.4, 4.8, and 8.6 GHz, which have been made at intervals of 4-6 weeks. The flux density data show that the remnant brightness is now increasing exponentially, while the radio spectrum is flattening. The current spectral index value of -0.68 represents an 18 ± 3% increase over the last eight years. The exponential trend in the flux is also found in the ATCA imaging observations at 9 GHz, which have been made since 1992, approximately twice a year, as well as in the 843 MHz data set from the Molonglo Observatory Synthesis Telescope from 1987 to 2007 March. Comparisons with data at different wavelengths (X-ray, Hα) are made. The rich data set that has been assembled in the last 22 years forms a basis for a better understanding of the evolution of the supernova remnant.

  8. Evolvability Search: Directly Selecting for Evolvability in order to Study and Produce It

    DEFF Research Database (Denmark)

    Mengistu, Henok; Lehman, Joel Anthony; Clune, Jeff

    2016-01-01

    of evolvable digital phenotypes. Although some types of selection in evolutionary computation indirectly encourage evolvability, one unexplored possibility is to directly select for evolvability. To do so, we estimate an individual's future potential for diversity by calculating the behavioral diversity of its...... immediate offspring, and select organisms with increased offspring variation. While the technique is computationally expensive, we hypothesized that direct selection would better encourage evolvability than indirect methods. Experiments in two evolutionary robotics domains confirm this hypothesis: in both...... domains, such Evolvability Search produces solutions with higher evolvability than those produced with Novelty Search or traditional objective-based search algorithms. Further experiments demonstrate that the higher evolvability produced by Evolvability Search in a training environment also generalizes...

  9. The Effect of Solar Radiation on Radio Signal for Radio Astronomy Purposes

    International Nuclear Information System (INIS)

    Nor Hazmin Sabri; Atiq Wahidah Azlan; Roslan Umar; Roslan Umar; Shahirah Syafa Sulan; Zainol Abidin Ibrahim; Wan Zul Adli Wan Mokhtar

    2015-01-01

    Radio astronomy is a subfields of astronomy which is discovers the celestial objects at radio frequencies. Observation in radio astronomy is conducted using single antenna or array of antennas, known as radio telescope. Other than that, radio astronomy also holds an advantage over other alternatives to optical astronomy due to its capability of observing from the ground level. In this study, the effect of solar radiation that contributes the Radio Frequency Interferences (RFI) is reviewed. The low RFI level is required to set up the radio telescope for radio astronomy observation. The effect of solar radiation on radio signal was investigated by determining the RFI pattern using spectrum analyzer. The solar radiation data was obtained from weather station located at KUSZA Observatory, East Coast Environmental Research Institute (ESERI), UniSZA. We can conclude that the solar radiation factor give the minimum significant effect to radio signal. (author)

  10. STELLAR ARCHEOLOGY IN THE GALACTIC HALO WITH ULTRA-FAINT DWARFS. VII. HERCULES

    Energy Technology Data Exchange (ETDEWEB)

    Musella, Ilaria; Ripepi, Vincenzo; Marconi, Marcella, E-mail: ilaria@na.astro.it, E-mail: ripepi@na.astro.it, E-mail: marcella@na.astro.it [INAF, Osservatorio Astronomico di Capodimonte, I-8013 Napoli (Italy); and others

    2012-09-10

    We present the first time-series study of the ultra-faint dwarf galaxy Hercules. Using a variety of telescope/instrument facilities we secured about 50 V and 80 B epochs. These data allowed us to detect and characterize 10 pulsating variable stars in Hercules. Our final sample includes six fundamental-mode (ab-type) and three first-overtone (c-type) RR Lyrae stars, and one Anomalous Cepheid. The average period of the ab-type RR Lyrae stars, (P{sub ab}) = 0.68 days ({sigma} = 0.03 days), places Hercules in the Oosterhoff II group, as found for almost the totality of the ultra-faint dwarf galaxies investigated so far for variability. The RR Lyrae stars were used to obtain independent estimates of the metallicity, reddening, and distance to Hercules, for which we find [Fe/H] = -2.30 {+-} 0.15 dex, E(B - V) = 0.09 {+-} 0.02 mag, and (m - M){sub 0} = 20.6 {+-} 0.1 mag, in good agreement with the literature values. We have obtained a V, B - V color-magnitude diagram (CMD) of Hercules that reaches V {approx} 25 mag and extends beyond the galaxy's half-light radius over a total area of 40' Multiplication-Sign 36'. The CMD and the RR Lyrae stars indicate the presence of a population as old and metal-poor as (at least) the Galactic globular cluster M68.

  11. Radio frequency integrated circuit design for cognitive radio systems

    CERN Document Server

    Fahim, Amr

    2015-01-01

    This book fills a disconnect in the literature between Cognitive Radio systems and a detailed account of the circuit implementation and architectures required to implement such systems.  Throughout the book, requirements and constraints imposed by cognitive radio systems are emphasized when discussing the circuit implementation details.  In addition, this book details several novel concepts that advance state-of-the-art cognitive radio systems.  This is a valuable reference for anybody with background in analog and radio frequency (RF) integrated circuit design, needing to learn more about integrated circuits requirements and implementation for cognitive radio systems. ·         Describes in detail cognitive radio systems, as well as the circuit implementation and architectures required to implement them; ·         Serves as an excellent reference to state-of-the-art wideband transceiver design; ·         Emphasizes practical requirements and constraints imposed by cognitive radi...

  12. Considerations for the Next Revision of NASA's Space Telecommunications Radio System Architecture

    Science.gov (United States)

    Johnson, Sandra K.; Handler, Louis M.; Briones, Janette C.

    2016-01-01

    Development of NASA's Software Defined Radio architecture, the Space Telecommunication Radio System (STRS), was initiated in 2004 with a goal of reducing the cost, risk and schedule when implementing Software Defined Radios (SDR) for National Aeronautics and Space Administration (NASA) space missions. Since STRS was first flown in 2012 on three Software Defined Radios on the Space Communication and Navigation (SCaN) Testbed, only minor changes have been made to the architecture. Multiple entities have since implemented the architecture and provided significant feedback for consideration for the next revision of the standard. The focus for the first set of updates to the architecture is items that enhance application portability. Items that require modifications to existing applications before migrating to the updated architecture will only be considered if there is compelling reasons to make the change. The significant suggestions that were further evaluated for consideration include expanding and clarifying the timing Application Programming Interfaces (APIs), improving handle name and identification (ID) definitions and use, and multiple items related to implementation of STRS Devices. In addition to ideas suggested while implementing STRS, SDR technology has evolved significantly and this impact to the architecture needs to be considered. These include incorporating cognitive concepts - learning from past decisions and making new decisions that the radio can act upon. SDRs are also being developed that do not contain a General Purpose Module - which is currently required for the platform to be STRS compliant. The purpose of this paper is to discuss the comments received, provide a summary of the evaluation considerations, and examine planned dispositions.

  13. Star/galaxy separation at faint magnitudes: Application to a simulated Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Soumagnac, M.T.; et al.

    2013-06-21

    We address the problem of separating stars from galaxies in future large photometric surveys. We focus our analysis on simulations of the Dark Energy Survey (DES). In the first part of the paper, we derive the science requirements on star/galaxy separation, for measurement of the cosmological parameters with the Gravitational Weak Lensing and Large Scale Structure probes. These requirements are dictated by the need to control both the statistical and systematic errors on the cosmological parameters, and by Point Spread Function calibration. We formulate the requirements in terms of the completeness and purity provided by a given star/galaxy classifier. In order to achieve these requirements at faint magnitudes, we propose a new method for star/galaxy separation in the second part of the paper. We first use Principal Component Analysis to outline the correlations between the objects parameters and extract from it the most relevant information. We then use the reduced set of parameters as input to an Artificial Neural Network. This multi-parameter approach improves upon purely morphometric classifiers (such as the classifier implemented in SExtractor), especially at faint magnitudes: it increases the purity by up to 20% for stars and by up to 12% for galaxies, at i-magnitude fainter than 23.

  14. Star/galaxy separation at faint magnitudes: application to a simulated Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Soumagnac, M. T.; Abdalla, F. B.; Lahav, O.; Kirk, D.; Sevilla, I.; Bertin, E.; Rowe, B. T. P.; Annis, J.; Busha, M. T.; Da Costa, L. N.; Frieman, J. A.; Gaztanaga, E.; Jarvis, M.; Lin, H.; Percival, W. J.; Santiago, B. X.; Sabiu, C. G.; Wechsler, R. H.; Wolz, L.; Yanny, B.

    2015-04-14

    We address the problem of separating stars from galaxies in future large photometric surveys. We focus our analysis on simulations of the Dark Energy Survey (DES). In the first part of the paper, we derive the science requirements on star/galaxy separation, for measurement of the cosmological parameters with the gravitational weak lensing and large-scale structure probes. These requirements are dictated by the need to control both the statistical and systematic errors on the cosmological parameters, and by point spread function calibration. We formulate the requirements in terms of the completeness and purity provided by a given star/galaxy classifier. In order to achieve these requirements at faint magnitudes, we propose a new method for star/galaxy separation in the second part of the paper. We first use principal component analysis to outline the correlations between the objects parameters and extract from it the most relevant information. We then use the reduced set of parameters as input to an Artificial Neural Network. This multiparameter approach improves upon purely morphometric classifiers (such as the classifier implemented in SExtractor), especially at faint magnitudes: it increases the purity by up to 20 per cent for stars and by up to 12 per cent for galaxies, at i-magnitude fainter than 23.

  15. Introduction to solar radio astronomy and radio physics

    International Nuclear Information System (INIS)

    Krueger, A.

    1979-01-01

    A systematic summary is presented of the work done during the last thirty years in the field of solar radio astronomy from the standpoint of general solar physics. Instrumental aspects, observations and theory are covered. A brief introduction is given to the matter consisting of the history of solar radio astronomy and some fundamentals of astronomy and solar physics are outlined. Some topics of the instrumental background of solar radio astronomy and the main results of observations are presented. The elements of a theoretical interpretation of solar radio observations are reported and a synthesis of both observation and theory contributing to a general picture of solar and solar-terrestrial physics is outlined. (C.F./Auth)

  16. Evolvable synthetic neural system

    Science.gov (United States)

    Curtis, Steven A. (Inventor)

    2009-01-01

    An evolvable synthetic neural system includes an evolvable neural interface operably coupled to at least one neural basis function. Each neural basis function includes an evolvable neural interface operably coupled to a heuristic neural system to perform high-level functions and an autonomic neural system to perform low-level functions. In some embodiments, the evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy.

  17. 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

  18. La radio en África. Una radio para el desarrollo

    Directory of Open Access Journals (Sweden)

    Jean-Paul Lafrance

    2015-01-01

    Full Text Available La radio de tipo comunitario, tal como la conocemos en Norteamérica y Europa (no-comercial, no-estatal y particípatíva, no existe en Africa. Sin embargo, la situación histórica y el contexto socio-político particulares de Africa han precedido la instauración de una radio que, dentro del marco del presente estudio, nos ha resultado interesante. Se trata de la radio educativa rural. Aunque enmarcada dentro del molde estatal de regímenes que en su mayoría son dictaduras, la radio rural africana, al igual que las radios de tipo comunitario, utiliza la radio con otros fines además de los convencionales. En este caso, la radio es un instrumento al servicio del desarrollo, por no decir al servicio del campesino, en una relación con éste último que probablemente dejará cada vez más de ser uni-direccional. La experiencia africana nos proporcionará en esta perspectiva nuevos elementos de reflexión en lo que respecta al rol de la radio dentro de la comunidad y sobre las condiciones incluso del éxito o no-éxito de la participación popular.

  19. 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.

  20. A Radio Astronomy Science Education Partnership - GAVRT and Radio JOVE

    Science.gov (United States)

    Higgins, C. A.; Thieman, J. R.; Bunnell, K.; Soholt, G.

    2009-12-01

    The planet Jupiter provides an excellent subject to educate, engage, and inspire students and teachers to learn science. The Goldstone Apple-Valley Radio Telescope (GAVRT) program (http://www.lewiscenter.org/gavrt) and The Radio JOVE project (http://radiojove.gsfc.nasa.gov) each have a long history of allowing students and teachers to interact with scientists and real radio telescopes. The upcoming Juno mission to Jupiter (2011 launch) allows both GAVRT and Radio JOVE to combine efforts and engage with the NASA Juno mission, thus increasing the excitement and learning potential for teachers, students, and the general public. Teachers can attend workshops for training to operate a 34-meter radio telescope and/or build their own simple radio telescope, both of which can be used directly in the classroom. We will overview some classroom activities and highlight some teacher-student experiences. In addition, we will update our efforts on greater Web-based control of the radio telescopes, as well as highlight our upcoming workshops to allow better access for teachers in different parts of the Country.

  1. Amateur Planetary Radio Data Archived for Science and Education: Radio Jove

    Science.gov (United States)

    Thieman, J.; Cecconi, B.; Sky, J.; Garcia, L. N.; King, T. A.; Higgins, C. A.; Fung, S. F.

    2015-12-01

    The Radio Jove Project is a hands-on educational activity in which students, teachers, and the general public build simple radio telescopes, usually from a kit, to observe single frequency decameter wavelength radio emissions from Jupiter, the Sun, the galaxy, and the Earth usually with simple dipole antennas. Some of the amateur observers have upgraded their receivers to spectrographs and their antennas have become more sophisticated as well. The data records compare favorably to more sophisticated professional radio telescopes such as the Long Wavelength Array (LWA) and the Nancay Decametric Array. Since these data are often carefully calibrated and recorded around the clock in widely scattered locations they represent a valuable database useful not only to amateur radio astronomers but to the professional science community as well. Some interesting phenomena have been noted in the data that are of interest to the professionals familiar with such records. The continuous monitoring of radio emissions from Jupiter could serve as useful "ground truth" data during the coming Juno mission's radio observations of Jupiter. Radio Jove has long maintained an archive for thousands of Radio Jove observations, but the database was intended for use by the Radio Jove participants only. Now, increased scientific interest in the use of these data has resulted in several proposals to translate the data into a science community data format standard and store the data in professional archives. Progress is being made in translating Radio Jove data to the Common Data Format (CDF) and also in generating new observations in that format as well. Metadata describing the Radio Jove data would follow the Space Physics Archive Search and Extract (SPASE) standard. The proposed archive to be used for long term preservation would be the Planetary Data System (PDS). Data sharing would be achieved through the PDS and the Paris Astronomical Data Centre (PADC) and the Virtual Wave Observatory (VWO

  2. 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.

  3. 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

  4. Accurate shear measurement with faint sources

    International Nuclear Information System (INIS)

    Zhang, Jun; Foucaud, Sebastien; Luo, Wentao

    2015-01-01

    For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys

  5. 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

  6. Combine TV-L1 model with guided image filtering for wide and faint ring artifacts correction of in-line x-ray phase contrast computed tomography.

    Science.gov (United States)

    Ji, Dongjiang; Qu, Gangrong; Hu, Chunhong; Zhao, Yuqing; Chen, Xiaodong

    2018-01-01

    In practice, mis-calibrated detector pixels give rise to wide and faint ring artifacts in the reconstruction image of the In-line phase-contrast computed tomography (IL-PC-CT). Ring artifacts correction is essential in IL-PC-CT. In this study, a novel method of wide and faint ring artifacts correction was presented based on combining TV-L1 model with guided image filtering (GIF) in the reconstruction image domain. The new correction method includes two main steps namely, the GIF step and the TV-L1 step. To validate the performance of this method, simulation data and real experimental synchrotron data are provided. The results demonstrate that TV-L1 model with GIF step can effectively correct the wide and faint ring artifacts for IL-PC-CT.

  7. High-resolution observations of low-luminosity gigahertz-peaked spectrum and compact steep-spectrum sources

    Science.gov (United States)

    Collier, J. D.; Tingay, S. J.; Callingham, J. R.; Norris, R. P.; Filipović, M. D.; Galvin, T. J.; Huynh, M. T.; Intema, H. T.; Marvil, J.; O'Brien, A. N.; Roper, Q.; Sirothia, S.; Tothill, N. F. H.; Bell, M. E.; For, B.-Q.; Gaensler, B. M.; Hancock, P. J.; Hindson, L.; Hurley-Walker, N.; Johnston-Hollitt, M.; Kapińska, A. D.; Lenc, E.; Morgan, J.; Procopio, P.; Staveley-Smith, L.; Wayth, R. B.; Wu, C.; Zheng, Q.; Heywood, I.; Popping, A.

    2018-06-01

    We present very long baseline interferometry observations of a faint and low-luminosity (L1.4 GHz GPS) and compact steep-spectrum (CSS) sample. We select eight sources from deep radio observations that have radio spectra characteristic of a GPS or CSS source and an angular size of θ ≲ 2 arcsec, and detect six of them with the Australian Long Baseline Array. We determine their linear sizes, and model their radio spectra using synchrotron self-absorption (SSA) and free-free absorption (FFA) models. We derive statistical model ages, based on a fitted scaling relation, and spectral ages, based on the radio spectrum, which are generally consistent with the hypothesis that GPS and CSS sources are young and evolving. We resolve the morphology of one CSS source with a radio luminosity of 10^{25} W Hz^{-1}, and find what appear to be two hotspots spanning 1.7 kpc. We find that our sources follow the turnover-linear size relation, and that both homogeneous SSA and an inhomogeneous FFA model can account for the spectra with observable turnovers. All but one of the FFA models do not require a spectral break to account for the radio spectrum, while all but one of the alternative SSA and power-law models do require a spectral break to account for the radio spectrum. We conclude that our low-luminosity sample is similar to brighter samples in terms of their spectral shape, turnover frequencies, linear sizes, and ages, but cannot test for a difference in morphology.

  8. a Faint and Lonely Brown Dwarf in the Solar Vicinity

    Science.gov (United States)

    1997-04-01

    Discovery of KELU-1 Promises New Insights into Strange Objects Brown Dwarfs are star-like objects which are too small to become real stars, yet too large to be real planets. Their mass is too small to ignite those nuclear processes which are responsible for the large energies and high temperatures of stars, but it is much larger than that of the planets we know in our solar system. Until now, very few Brown Dwarfs have been securely identified as such. Two are members of double-star systems, and a few more are located deep within the Pleiades star cluster. Now, however, Maria Teresa Ruiz of the Astronomy Department at Universidad de Chile (Santiago de Chile), using telescopes at the ESO La Silla observatory, has just discovered one that is all alone and apparently quite near to us. Contrary to the others which are influenced by other objects in their immediate surroundings, this new Brown Dwarf is unaffected and will thus be a perfect object for further investigations that may finally allow us to better understand these very interesting celestial bodies. It has been suggested that Brown Dwarfs may constitute a substantial part of the unseen dark matter in our Galaxy. This discovery may therefore also have important implications for this highly relevant research area. Searching for nearby faint stars The story of this discovery goes back to 1987 when Maria Teresa Ruiz decided to embark upon a long-term search (known as the Calan-ESO proper-motion survey ) for another type of unusual object, the so-called White Dwarfs , i.e. highly evolved, small and rather faint stars. Although they have masses similar to that of the Sun, such stars are no larger than the Earth and are therefore extremely compact. They are particularly interesting, because they most probably represent the future end point of evolution of our Sun, some billions of years from now. For this project, the Chilean astronomer obtained large-field photographic exposures with the 1-m ESO Schmidt telescope at

  9. 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...

  10. 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)

  11. Population Synthesis of Radio and Y-ray Normal, Isolated Pulsars Using Markov Chain Monte Carlo

    Science.gov (United States)

    Billman, Caleb; Gonthier, P. L.; Harding, A. K.

    2013-04-01

    We present preliminary results of a population statistics study of normal pulsars (NP) from the Galactic disk using Markov Chain Monte Carlo techniques optimized according to two different methods. The first method compares the detected and simulated cumulative distributions of series of pulsar characteristics, varying the model parameters to maximize the overall agreement. The advantage of this method is that the distributions do not have to be binned. The other method varies the model parameters to maximize the log of the maximum likelihood obtained from the comparisons of four-two dimensional distributions of radio and γ-ray pulsar characteristics. The advantage of this method is that it provides a confidence region of the model parameter space. The computer code simulates neutron stars at birth using Monte Carlo procedures and evolves them to the present assuming initial spatial, kick velocity, magnetic field, and period distributions. Pulsars are spun down to the present and given radio and γ-ray emission characteristics, implementing an empirical γ-ray luminosity model. A comparison group of radio NPs detected in ten-radio surveys is used to normalize the simulation, adjusting the model radio luminosity to match a birth rate. We include the Fermi pulsars in the forthcoming second pulsar catalog. We present preliminary results comparing the simulated and detected distributions of radio and γ-ray NPs along with a confidence region in the parameter space of the assumed models. We express our gratitude for the generous support of the National Science Foundation (REU and RUI), Fermi Guest Investigator Program and the NASA Astrophysics Theory and Fundamental Program.

  12. A Link Between X-ray Emission Lines and Radio Jets in 4U 1630-47?

    Science.gov (United States)

    Neilsen, Joseph; Coriat, Mickaël; Fender, Rob; Lee, Julia C.; Ponti, Gabriele; Tzioumis, A.; Edwards, Phillip; Broderick, Jess

    2014-06-01

    Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. We present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find a strong disk wind but no evidence for any relativistic X-ray emission lines. Indeed, despite ˜5× brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ˜20× weaker than the line observed by Díaz Trigo et al. Thus we can conclusively say that radio emission is not universally associated with relativistically Doppler-shifted emission lines in 4U 1630-47. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby ISM, in which case the X-ray emission lines might be unrelated to the radio emission.

  13. Radio Astronomers Develop New Technique for Studying Dark Energy

    Science.gov (United States)

    2010-07-01

    capabilities of current instruments -- the team used their intensity-mapping technique to accumulate the radio waves emitted by the hydrogen gas in large volumes of space including many galaxies. "Since the early part of the 20th Century, astronomers have traced the expansion of the Universe by observing galaxies. Our new technique allows us to skip the galaxy-detection step and gather radio emissions from a thousand galaxies at a time, as well as all the dimly-glowing material between them," said Jeffrey Peterson, of Carnegie Mellon University. The astronomers also developed new techniques that removed both man-made radio interference and radio emission caused by more-nearby astronomical sources, leaving only the extremely faint radio waves coming from the very distant hydrogen gas. The result was a map of part of the "cosmic web" that correlated neatly with the structure shown by the earlier optical study. The team first proposed their intensity-mapping technique in 2008, and their GBT observations were the first test of the idea. "These observations detected more hydrogen gas than all the previously-detected hydrogen in the Universe, and at distances ten times farther than any radio wave-emitting hydrogen seen before," said Ue-Li Pen of the University of Toronto. "This is a demonstration of an important technique that has great promise for future studies of the evolution of large-scale structure in the Universe," said National Radio Astronomy Observatory Chief Scientist Chris Carilli, who was not part of the research team. In addition to Chang, Peterson, and Pen, the research team included Kevin Bandura of Carnegie Mellon University. The scientists reported their work in the July 22 issue of the scientific journal Nature.

  14. The X-Ray Core of the Low-Luminosity Radio Galaxy 3C346 and ASCA Spectroscopy to Test BL LAC/Radio Galaxy Unification

    Science.gov (United States)

    Worrall, Diana

    2000-01-01

    Radio galaxies are relatively faint sources for Advanced Spacecraft for Cosmology Astrophysics (ASCA), and so in order to get the best possible results from the observations two things have been necessary, both of which delayed the fast preparation of papers. Firstly, the best possible data screening and background subtraction were necessary to improve the signal-to-noise, and all our several initial analysis trials were discarded in favor of using FTOOLS versions 4.1 and above. Secondly, we found that the ASCA spectra were statistically too poor to discriminate well between non-thermal and thermal models, never mind the mixture of the two which we expected on the basis of our ROSAT spatial separation of components in radio galaxies. This means that in each case we have needed to combine the ASCA spectroscopy with analysis of data from other X-ray or radio observations in order to exploit the ASCA data to the full. Our analysis for 3C 346 has yielded the cleanest final result. This powerful radio galaxy at a redshift of 0.161, lies in a poor cluster, which we have separated well from the dominant X-ray component of unresolved emission using a spatial analysis of archival ROSAT data. We were then able to fix the thermal component in our ASCA spectral analysis, and have found evidence that the unresolved emission varied by 32 +/- 13% over the 18 months between the ROSAT and ASCA observations. The unresolved X-ray emission does not suffer from intrinsic absorption, and we have related it to radio structures on both milliarcsecond scales and the arcsecond scales which Chandra can resolve. The source is a target of a Chandra AO2 proposal which we have recently submitted to follow up on our ASCA (and ROSAT) work. 3C 346's orientation to the line of sight is uncertain. However, the absence of X-ray absorption, and the radio/optical/X-ray colors, when combined with with previous radio evidence that the source is a foreshortened radio galaxy of the FRII class, suggest that

  15. Radio Frequency Interference: The Study of Rain Effect on Radio Signal Attenuation

    International Nuclear Information System (INIS)

    Roslan Umar; Roslan Umar; Shahirah Syafa Sulan; Atiq Wahidah Azlan; Zainol Abidin Ibrahim

    2015-01-01

    The intensity of radio waves received by radio telescopes is always not subject to human control. In the millimetre band, the propagation of the electromagnetic waves is severely affected by rain rate, dust particle size and drop size in the terms of attenuation, noise and depolarization. At the frequency above 10 GHz, the absorption and scattering by rain cause a reduction in the transmitted signal amplitude which will lead to the reducing of the availability, reliability and performance on the communications link. In this study, the rain effect on radio signal has been investigated. Spectrum analyzer and weather stations were used to obtain the RFI level and rain rate data respectively. The radio frequency interference (RFI) pattern due to rain factor was determined. This will benefit radio astronomer in managing sites for radio observation for radio astronomy purposes. (author)

  16. GREEN BANK TELESCOPE AND SWIFT X-RAY TELESCOPE OBSERVATIONS OF THE GALACTIC CENTER RADIO MAGNETAR SGR J1745–2900

    Energy Technology Data Exchange (ETDEWEB)

    Lynch, Ryan S.; Archibald, Robert F.; Kaspi, Victoria M.; Scholz, Paul, E-mail: rlynch@physics.mcgill.ca [Department of Physics, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8 (Canada)

    2015-06-20

    We present results from eight months of Green Bank Telescope 8.7 GHz observations and nearly 18 months of Swift X-ray telescope observations of the radio magnetar SGR J1745–2900. We tracked the radio and X-ray flux density, polarization properties, profile evolution, rotation, and single-pulse behavior. We identified two main periods of activity. The first is characterized by approximately 5.5 months of relatively stable evolution in radio flux density, rotation, and profile shape, while in the second these properties varied substantially. Specifically, a third profile component emerged and the radio flux also became more variable. The single pulse properties also changed, most notably with a larger fraction of pulses with pulse widths ∼5–20 ms in the erratic state. Bright single pulses are well described by a log-normal energy distribution at low energies, but with an excess at high energies. The 2–10 keV flux decayed steadily since the initial X-ray outburst, while the radio flux remained stable to within ∼20% during the stable state. A joint pulsar timing analysis of the radio and X-ray data shows a level of timing noise unprecedented in a radio magnetar, though during the time covered by the radio data alone the timing noise was at a level similar to that observed in other radio magnetars. While SGR J1745–2900 is similar to other radio magnetars in many regards, it differs by having experienced a period of relative stability in the radio that now appears to have ended, while the X-ray properties evolved independently.

  17. Mean and Extreme Radio Properties of Quasars and the Origin of Radio Emission

    Science.gov (United States)

    Richards, Gordon T.; Kratzer, R.

    2014-01-01

    We explore the evolution of the fraction of radio loud quasars and the mean radio properties of quasars. Although any quasar has only a ~10% chance of being radio loud and the average quasar has a radio luminosity of ~4x10^30 ergs/s/Hz, these properties are strong functions of not only luminosity, redshift, black hole mass, and accretion rate, but also the strength of the accretion disk wind (as characterized by CIV emission line properties). Quasars with higher optical luminosity and/or lower redshift have a higher than average probability of being radio loud, but their median radio luminosity (relative to optical) is much lower than average. We find that, while radio properties of quasars generally cannot be predicted from their optical properties, objects where one expects a strong radiation line driven wind (based on emission line features) have virtually no chance of being radio loud. The redder quasars are in the optical, the more radio flux (relative to optical) they have; this trend holds even for quasars that are not expected to be significantly dust reddened/extincted in the optical. Finally, we consider the radio properties of quasars in the framework of models which describe the radio loud extrema as being due to particularly high spin resulting from second generation mergers and in the context of star formation at lower levels of radio flux. This work was supported by NSF AAG grant 1108798.

  18. The Evolution of the Faint End of the UV Luminosity Function during the Peak Epoch of Star Formation (1 < z < 3)

    Science.gov (United States)

    Alavi, Anahita; Siana, Brian; Richard, Johan; Rafelski, Marc; Jauzac, Mathilde; Limousin, Marceau; Freeman, William R.; Scarlata, Claudia; Robertson, Brant; Stark, Daniel P.; Teplitz, Harry I.; Desai, Vandana

    2016-11-01

    We present a robust measurement of the rest-frame UV luminosity function (LF) and its evolution during the peak epoch of cosmic star formation at 1\\lt z\\lt 3. We use our deep near-ultraviolet imaging from WFC3/UVIS on the Hubble Space Telescope and existing Advanced Camera for Surveys (ACS)/WFC and WFC3/IR imaging of three lensing galaxy clusters, Abell 2744 and MACS J0717 from the Hubble Frontier Field survey and Abell 1689. Combining deep UV imaging and high magnification from strong gravitational lensing, we use photometric redshifts to identify 780 ultra-faint galaxies with {M}{UV}\\lt -12.5 AB mag at 1\\lt z\\lt 3. From these samples, we identified five new, faint, multiply imaged systems in A1689. We run a Monte Carlo simulation to estimate the completeness correction and effective volume for each cluster using the latest published lensing models. We compute the rest-frame UV LF and find the best-fit faint-end slopes of α =-1.56+/- 0.04, α =-1.72+/- 0.04, and α =-1.94+/- 0.06 at 1.0\\lt z\\lt 1.6, 1.6\\lt z\\lt 2.2, and 2.2\\lt z\\lt 3.0, respectively. Our results demonstrate that the UV LF becomes steeper from z˜ 1.3 to z˜ 2.6 with no sign of a turnover down to {M}{UV}=-14 AB mag. We further derive the UV LFs using the Lyman break “dropout” selection and confirm the robustness of our conclusions against different selection methodologies. Because the sample sizes are so large and extend to such faint luminosities, the statistical uncertainties are quite small, and systematic uncertainties (due to the assumed size distribution, for example) likely dominate. If we restrict our analysis to galaxies and volumes above \\gt 50 % completeness in order to minimize these systematics, we still find that the faint-end slope is steep and getting steeper with redshift, though with slightly shallower (less negative) values (α =-1.55+/- 0.06, -1.69 ± 0.07, and -1.79 ± 0.08 for z˜ 1.3, 1.9, and 2.6, respectively). Finally, we conclude that the faint star

  19. A LINK BETWEEN X-RAY EMISSION LINES AND RADIO JETS IN 4U 1630-47?

    Energy Technology Data Exchange (ETDEWEB)

    Neilsen, Joseph [Department of Astronomy, Boston University, Boston, MA 02215 (United States); Coriat, Mickaël [Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Fender, Rob; Broderick, Jess W. [Department of Physics, Oxford University, Oxford OX1 3RH (United Kingdom); Lee, Julia C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Ponti, Gabriele [Max Planck Institute fur Extraterrestriche Physik, D-85748 Garching (Germany); Tzioumis, Anastasios K.; Edwards, Philip G., E-mail: neilsenj@bu.edu [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia)

    2014-03-20

    Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. Here we present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find no evidence for any relativistic X-ray emission lines. Indeed, despite ∼5 × brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ≳ 20 × weaker than the line observed by Díaz Trigo et al. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby interstellar medium, in which case the X-ray emission lines might be unrelated to the radio emission.

  20. A LINK BETWEEN X-RAY EMISSION LINES AND RADIO JETS IN 4U 1630-47?

    International Nuclear Information System (INIS)

    Neilsen, Joseph; Coriat, Mickaël; Fender, Rob; Broderick, Jess W.; Lee, Julia C.; Ponti, Gabriele; Tzioumis, Anastasios K.; Edwards, Philip G.

    2014-01-01

    Recently, Díaz Trigo et al. reported an XMM-Newton detection of relativistically Doppler-shifted emission lines associated with steep-spectrum radio emission in the stellar-mass black hole candidate 4U 1630-47 during its 2012 outburst. They interpreted these lines as indicative of a baryonic jet launched by the accretion disk. Here we present a search for the same lines earlier in the same outburst using high-resolution X-ray spectra from the Chandra HETGS. While our observations (eight months prior to the XMM-Newton campaign) also coincide with detections of steep spectrum radio emission by the Australia Telescope Compact Array, we find no evidence for any relativistic X-ray emission lines. Indeed, despite ∼5 × brighter radio emission, our Chandra spectra allow us to place an upper limit on the flux in the blueshifted Fe XXVI line that is ≳ 20 × weaker than the line observed by Díaz Trigo et al. We explore several scenarios that could explain our differing results, including variations in the geometry of the jet or a mass-loading process or jet baryon content that evolves with the accretion state of the black hole. We also consider the possibility that the radio emission arises in an interaction between a jet and the nearby interstellar medium, in which case the X-ray emission lines might be unrelated to the radio emission

  1. 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.

  2. [Evaluation of medication advertising broadcast on radio stations].

    Science.gov (United States)

    Batista, Almária Mariz; Carvalho, Maria Cleide Ribeiro Dantas de

    2013-02-01

    The scope of this paper was to evaluate advertising for medication broadcast on radio stations in Natal, State of Rio Grande do Norte, Brazil, from April to September 2008 and from April to September 2010. The advertising was recorded and transcribed in order to conduct legal analysis and content analysis based on the precepts of Laurence Bardin. Both the advertising recorded during the first stage (regulated by RDC 102/00) and the second stage (regulated by RDC 96/08) contained some form of legal violation. Content analysis detected practically the same violations in both stages, namely the lack of information regarding adverse effects of the medication, appeal to consumption, exaggeration of efficiency/effectiveness and abusive exploitation of illness. Despite the inclusion of more modern and restrictive legislation, radio advertising continues to violate the law blatantly, committing abuse and disrespecting the population's entitlement to good health. The study reveals the need for medication advertising to be dealt with in a broader context, in other words to be treated as a public health concern. It must take into consideration the socio-historical scenario in which it evolved, since the legislation alone is insufficient to combat abuse committed to the detriment of public health.

  3. Alignment statistics of clusters with their brightest members at bright and faint isophotes

    International Nuclear Information System (INIS)

    Struble, M.F.

    1987-01-01

    For a sample of 21 first-ranked cluster galaxies with published isophotal photometry and position angles of these isophotes, it is found that the major axes of both the bright and faint isophotal contours tend to be aligned within about 30 deg of the major axis of the parent cluster. This supports the hypothesis that first-ranked galaxies are formed already aligned with their parent clusters rather than the hypothesis that only outer envelopes which accreted after formation are aligned with the cluster. 21 references

  4. Extended Schmidt law holds for faint dwarf irregular galaxies

    Science.gov (United States)

    Roychowdhury, Sambit; Chengalur, Jayaram N.; Shi, Yong

    2017-12-01

    Context. The extended Schmidt law (ESL) is a variant of the Schmidt which relates the surface densities of gas and star formation, with the surface density of stellar mass added as an extra parameter. Although ESL has been shown to be valid for a wide range of galaxy properties, its validity in low-metallicity galaxies has not been comprehensively tested. This is important because metallicity affects the crucial atomic-to-molecular transition step in the process of conversion of gas to stars. Aims: We empirically investigate for the first time whether low metallicity faint dwarf irregular galaxies (dIrrs) from the local universe follow the ESL. Here we consider the "global" law where surface densities are averaged over the galactic discs. dIrrs are unique not only because they are at the lowest end of mass and star formation scales for galaxies, but also because they are metal-poor compared to the general population of galaxies. Methods: Our sample is drawn from the Faint Irregular Galaxy GMRT Survey (FIGGS) which is the largest survey of atomic hydrogen in such galaxies. The gas surface densities are determined using their atomic hydrogen content. The star formation rates are calculated using GALEX far ultraviolet fluxes after correcting for dust extinction, whereas the stellar surface densities are calculated using Spitzer 3.6 μm fluxes. The surface densities are calculated over the stellar discs defined by the 3.6 μm images. Results: We find dIrrs indeed follow the ESL. The mean deviation of the FIGGS galaxies from the relation is 0.01 dex, with a scatter around the relation of less than half that seen in the original relation. In comparison, we also show that the FIGGS galaxies are much more deviant when compared to the "canonical" Kennicutt-Schmidt relation. Conclusions: Our results help strengthen the universality of the ESL, especially for galaxies with low metallicities. We suggest that models of star formation in which feedback from previous generations

  5. 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.

  6. 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)

  7. A Modified Adaptive Stochastic Resonance for Detecting Faint Signal in Sensors

    Directory of Open Access Journals (Sweden)

    Hengwei Li

    2007-02-01

    Full Text Available In this paper, an approach is presented to detect faint signals with strong noises in sensors by stochastic resonance (SR. We adopt the power spectrum as the evaluation tool of SR, which can be obtained by the fast Fourier transform (FFT. Furthermore, we introduce the adaptive filtering scheme to realize signal processing automatically. The key of the scheme is how to adjust the barrier height to satisfy the optimal condition of SR in the presence of any input. For the given input signal, we present an operable procedure to execute the adjustment scheme. An example utilizing one audio sensor to detect the fault information from the power supply is given. Simulation results show that th

  8. Faint H-alpha emission objects near the equatorial selected areas

    International Nuclear Information System (INIS)

    Robertson, T.H.; Jordan, T.M.

    1989-01-01

    An objective-prism survey of fields centered on the 24 Kapteyn Selected Areas along the celestial equator has resulted in the detection of 120 faint H-alpha emission-line objects. Diffuse objects and stars having molecular bands in their spectra are not included. Only 18 of these stars were identified in previous lists of emission-line objects. Identifications were found for an additional three stars. Images of these objects appear to be stellar on direct plates. The magnitude range for these stars is V = 10.1-19.00. Positions and V magnitudes of these objects are provided, as are identifications of objects which have been reported in other lists. Frequency distributions of the apparent magnitudes and Galactic latitudes of these emission-line objects are discussed, and finding charts are provided. 14 refs

  9. South African Radio League Introduction to Amateur Radio: A study guide for the Radio Amateur Examination

    CSIR Research Space (South Africa)

    Burger, Chris

    2016-01-01

    Full Text Available ) .............................................................................. 15 1.12 The Radio Amateurs’ Examination .......................................................................... 15 1.13 Restrictions on the Use of an Amateur Radio Station .............................................. 16 Chapter 2: Operating... ............................................................................................. 116 14.1 Theory of Operation ............................................................................................... 116 14.2 Turns Ratio...

  10. 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

  11. 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.

  12. The origin and development of extragalactic radio astronomy: the role of CSIRO's Division of Radiophysics Dover Heights Field Station in Sydney

    Science.gov (United States)

    Orchiston, Wayne; Robertson, Peter

    2017-12-01

    Initial post-war developments in non-solar radio astronomy were inspired by Hey, Phillips and Parson’s report in 1946 of an intense source of radio emission in Cygnus. This so-called ‘radio star’ was unique, and questions immediately were raised about its true nature. But it did not remain unique for long. Observing from Sydney, John Bolton, Gordon Stanley and Bruce Slee followed up the Cygnus discovery with more radio star detections, beginning what would evolve into a long-term multi-faceted research program and one of the mainstays of the CSIRO’s Division of Radiophysics. But more than this, these early discoveries in England and in Sydney opened up a whole new field of investigation, extragalactic radio astronomy, which has remained a major area of investigation through to the present day. This paper focusses on the early years of this program when the observations were carried out at Dover Heights Field Station in Sydney, and the ways in which new developments in instrumentation that allowed a major expansion of the program eventually led to the closure of Dover Heights and the founding of the Fleurs Field Station.

  13. The Joint Facial and Invasive Neck Trauma (J-FAINT) Project, Iraq and Afghanistan 2003-2011

    Science.gov (United States)

    2013-01-01

    Original Research— Facial Plastic and Reconstructive Surgery The Joint Facial and Invasive Neck Trauma (J-FAINT) Project, Iraq and Afghanistan 2003...number and type of facial and penetrat- ing neck trauma injuries sustained in Operation Iraqi Freedom (OIF) and Operation Enduring Freedom (OEF). Study...queried for data from OIF and OEF from January 2003 to May 2011. Information on demographics; type and severity of facial , neck, and associated trauma

  14. 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

    -ray emission, which appears overlapping the northeastern part of the radio emission. Our spectral analysis demonstrated that a non-thermal origin for the X-ray emission compatible with a pulsar wind nebula is quite possible. The analysis of the spatial distribution of the CO gas revealed the presence of a complex of molecular clouds located in projection adjacent to the radio halo emission and probably interacting with it. We propose that the faint halo represents a composite supernova remnant with a pulsar powered component given by the diffuse X-ray emission superimposed along the line of sight to the radio galaxy. Further broadband observations of HESS J1844-030 are needed to disentangle its origin, although its shape and position suggest an extragalactic origin connected to G29.37+0.1. The reduced GMRT image (FITS file) 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/602/A31

  15. Comparison of Time/Phase Lags in the Hard State and Plateau State of GRS 1915+105

    NARCIS (Netherlands)

    Pahari, M.; Neilsen, J.; Yadav, J.S.; Misra, R.; Uttley, P.

    2013-01-01

    We investigate the complex behavior of energy- and frequency-dependent time/phase lags in the plateau state and the radio-quiet hard (χ) state of GRS 1915+105. In our timing analysis, we find that when the source is faint in the radio, quasi-periodic oscillations (QPOs) are observed above 2 Hz and

  16. The difference between radio-loud and radio-quiet active galaxies

    Science.gov (United States)

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

    1995-01-01

    The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

  17. Discovery of intergalactic radio emission in the Coma-A1367 supercluster

    International Nuclear Information System (INIS)

    Kim, K.T.; Kronberg, P.P.; Venturi, T.

    1989-01-01

    The Coma cluster is a rich cluster of galaxies nested in an even larger super cluster of galaxies. The plane of the supercluster seems to be defined by the Coma cluster itself and another galaxy cluster, Abell 1367, which lies ∼ 40 Mpc farther west. The largest structures known are the giant voids and superclusters which are as large as 70h 75 -1 Mpc (refs 3-5). The Coma cluster of galaxies seems to be located on the rim of a giant void in the three-dimensional distribution of galaxies. Here we describe the detection of faint, supercluster-scale radio emission at 326 MHz that extends between the Coma cluster of galaxies and the Abell 1367 cluster and which is apparently not associated with any individual galaxy system in the complex. The radiation's synchrotron origin implies the existence of a large-scale intercluster magnetic field with an estimated strength of 0.3-0.6 μG, which is remarkably strong. The synchrotron-emitting relativistic electrons cannot be older than a few times 10 8 yr, but we speculate that the magnetic field is the fossil of a pre-galactic primaeval field, which was amplified in the course of the formation of intergalactic voids and superclusters. (author)

  18. Faint (and bright variable stars in the satellites of the Milky Way

    Directory of Open Access Journals (Sweden)

    Vivas A. Katherina

    2017-01-01

    Full Text Available I describe two ongoing projects related with variable stars in the satellites of the MilkyWay. In the first project, we are searching for dwarf Cepheid stars (a.k.a δ Scuti and/or SX Phe in some of the classical dwarf spheroidal galaxies. Our goal is to characterize the population of these variable stars under different environments (age, metallicity in order to study their use as standard candles in systems for which the metallicity is not necessarily known. In the second project we search for RR Lyrae stars in the new ultra-faint satellite galaxies that have been discovered around the Milky Way in recent years.

  19. Information Content in Radio Waves: Student Investigations in Radio Science

    Science.gov (United States)

    Jacobs, K.; Scaduto, T.

    2013-12-01

    We describe an inquiry-based instructional unit on information content in radio waves, created in the summer of 2013 as part of a MIT Haystack Observatory (Westford, MA) NSF Research Experiences for Teachers (RET) program. This topic is current and highly relevant, addressing science and technical aspects from radio astronomy, geodesy, and atmospheric research areas as well as Next Generation Science Standards (NGSS). Projects and activities range from simple classroom demonstrations and group investigations, to long term research projects incorporating data acquisition from both student-built instrumentation as well as online databases. Each of the core lessons is applied to one of the primary research centers at Haystack through an inquiry project that builds on previously developed units through the MIT Haystack RET program. In radio astronomy, students investigate the application of a simple and inexpensive software defined radio chip (RTL-SDR) for use in systems implementing a small and very small radio telescope (SRT and VSRT). Both of these systems allow students to explore fundamental principles of radio waves and interferometry as applied to radio astronomy. In ionospheric research, students track solar storms from the initial coronal mass ejection (using Solar Dynamics Observatory images) to the resulting variability in total electron density concentrations using data from the community standard Madrigal distributed database system maintained by MIT Haystack. Finally, students get to explore very long-baseline interferometry as it is used in geodetic studies by measuring crustal plate displacements over time. Alignment to NextGen standards is provided for each lesson and activity with emphasis on HS-PS4 'Waves and Their Applications in Technologies for Information Transfer'.

  20. Tracking Galaxy Evolution Through Low-Frequency Radio Continuum Observations using SKA and Citizen-Science Research using Multi-Wavelength Data

    Science.gov (United States)

    Hota, Ananda; Konar, C.; Stalin, C. S.; Vaddi, Sravani; Mohanty, Pradeepta K.; Dabhade, Pratik; Dharmik Bhoga, Sai Arun; Rajoria, Megha; Sethi, Sagar

    2016-12-01

    We present a brief review of progress in the understanding of general spiral and elliptical galaxies, through merger, star formation and AGN activities. With reference to case studies performed with the GMRT, we highlight the unique aspects of studying galaxies in the radio wavelengths where powerful quasars and bright radio galaxies are traditionally the dominating subjects. Though AGN or quasar activity is extremely energetic, it is extremely short-lived. This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old as a few hundred Myr. There is a huge gap between this and what is found in optical bands. The very first relic-evidences of a past quasar activity (Hanny's Voorwerp) was discovered in 2007 by a Galaxy Zoo citizen-scientist, a school teacher, in the optical bands. This relic is around a few tens of thousand years old. More discoveries needed to match these time-scales with star formation time-scales in AGN host galaxies to better understand black hole galaxy co-evolution process via feedback-driven quenching of star formation. It is now well-accepted that discovery and characterization of such faint fuzzy relic features can be more efficiently done by human eye than a machine. Radio interferometry images are more complicated than optical and need the citizen-scientists to be trained. RAD@home, the only Indian citizen-science research project in astronomy, analysing TIFR GMRT Sky Survey (TGSS) 150 MHz data and observing from the Giant Meterwave Radio Telescope (GMRT), was launched in April 2013. Unique, zero-infrastructure zero-funded design of RAD@home as a collaboratory of 69 trained e-astronomers is briefly described. Some of the new-found objects like episodic radio galaxies, radio-jet and

  1. 47 CFR 95.201 - (R/C Rule 1) What is the Radio Control (R/C) Radio Service?

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false (R/C Rule 1) What is the Radio Control (R/C...) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Radio Control (R/C) Radio Service General Provisions § 95.201 (R/C Rule 1) What is the Radio Control (R/C) Radio Service? The R/C Service is a private...

  2. Robustness to Faults Promotes Evolvability: Insights from Evolving Digital Circuits.

    Science.gov (United States)

    Milano, Nicola; Nolfi, Stefano

    2016-01-01

    We demonstrate how the need to cope with operational faults enables evolving circuits to find more fit solutions. The analysis of the results obtained in different experimental conditions indicates that, in absence of faults, evolution tends to select circuits that are small and have low phenotypic variability and evolvability. The need to face operation faults, instead, drives evolution toward the selection of larger circuits that are truly robust with respect to genetic variations and that have a greater level of phenotypic variability and evolvability. Overall our results indicate that the need to cope with operation faults leads to the selection of circuits that have a greater probability to generate better circuits as a result of genetic variation with respect to a control condition in which circuits are not subjected to faults.

  3. 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)

  4. Foreground effect on the J-factor estimation of ultra-faint dwarf spheroidal galaxies

    Science.gov (United States)

    Ichikawa, Koji; Horigome, Shun-ichi; Ishigaki, Miho N.; Matsumoto, Shigeki; Ibe, Masahiro; Sugai, Hajime; Hayashi, Kohei

    2018-05-01

    Dwarf spheroidal galaxies (dSphs) are promising targets for the gamma-ray dark matter (DM) search. In particular, DM annihilation signal is expected to be strong in some of the recently discovered nearby ultra-faint dSphs, which potentially give stringent constraints on the O(1) TeV WIMP DM. However, various non-negligible systematic uncertainties complicate the estimation of the astrophysical factors relevant for the DM search in these objects. Among them, the effects of foreground stars particularly attract attention because the contamination is unavoidable even for the future kinematical survey. In this article, we assess the effects of the foreground contamination on the astrophysical J-factor estimation by generating mock samples of stars in the four ultra-faint dSphs and using a model of future spectrographs. We investigate various data cuts to optimize the quality of the data and apply a likelihood analysis which takes member and foreground stellar distributions into account. We show that the foreground star contaminations in the signal region (the region of interest) and their statistical uncertainty can be estimated by interpolating the foreground star distribution in the control region where the foreground stars dominate the member stars. Such regions can be secured at future spectroscopic observations utilizing a multiple object spectrograph with a large field of view; e.g. the Prime Focus Spectrograph mounted on Subaru Telescope. The above estimation has several advantages: The data-driven estimation of the contamination makes the analysis of the astrophysical factor stable against the complicated foreground distribution. Besides, foreground contamination effect is considered in the likelihood analysis.

  5. 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.

  6. Radio-graphene in theranostic perspectives

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Do Won [Dept. of Nuclear Medicine, Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2017-03-15

    Owing to its unique physicochemical properties such as high surface area, notable biocompatibility, robust mechanical strength, high thermal conductivity, and ease of functionalization, 2D-layered graphene has received tremendous attention as a futuristic nanomaterial and its-associated research has been rapidly evolving in a variety of fields. With the remarkable advances of graphene especially in the biomedical realm, in vivo evaluation techniques to examine in vivo behavior of graphene are largely demanded under the hope of clinical translation. Many different types of drugs such as the antisense oligomer and chemotherapeutics require optimal delivery conveyor and graphene is now recognized as a suitable candidate due to its simple and high drug loading property. Termed as ‘radio-graphene’, radioisotope-labeled graphene approach was recently harnessed in the realm of biomedicine including cancer diagnosis and therapy, contributing to the acquisition of in vivo information for targeted drug delivery. In this review, we highlight current examples for bioapplication of radiolabeled graphene with brief perspectives on future strategies in its extensive bio- or clinical applications.

  7. 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.

  8. Preface: evolving rotifers, evolving science: Proceedings of the XIV International Rotifer Symposium

    Czech Academy of Sciences Publication Activity Database

    Devetter, Miloslav; Fontaneto, D.; Jersabek, Ch.D.; Welch, D.B.M.; May, L.; Walsh, E.J.

    2017-01-01

    Roč. 796, č. 1 (2017), s. 1-6 ISSN 0018-8158 Institutional support: RVO:60077344 Keywords : evolving rotifers * 14th International Rotifer Symposium * evolving science Subject RIV: EG - Zoology OBOR OECD: Zoology Impact factor: 2.056, year: 2016

  9. 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…

  10. 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.

  11. THE [O III] NEBULA OF THE MERGER REMNANT NGC 7252: A LIKELY FAINT IONIZATION ECHO

    International Nuclear Information System (INIS)

    Schweizer, François; Kelson, Daniel D.; Villanueva, Edward V.; Seitzer, Patrick; Walth, Gregory L.

    2013-01-01

    We present images and spectra of a ∼10 kpc-sized emission-line nebulosity discovered in the prototypical merger remnant NGC 7252 and dubbed the ''[O III] nebula'' because of its dominant [O III] λ5007 line. This nebula seems to yield the first sign of episodic active galactic nucleus (AGN) activity still occurring in the remnant, ∼220 Myr after the coalescence of two gas-rich galaxies. Its location and kinematics suggest it belongs to a stream of tidal-tail gas falling back into the remnant. Its integrated [O III] λ5007 luminosity is 1.4 × 10 40 erg s –1 , and its spectrum features some high-excitation lines, including He II λ4686. In diagnostic line-ratio diagrams, the nebula lies in the domain of Seyfert galaxies, suggesting that it is photoionized by a source with a power-law spectrum. Yet, a search for AGN activity in NGC 7252 from X-rays to radio wavelengths yields no detection, with the most stringent upper limit set by X-ray observations. The upper luminosity limit of L 2-10 k eV,0 39 erg s –1 estimated for the nucleus is ∼10 3 times lower than the minimum ionizing luminosity of ∼> 5 × 10 42 erg s –1 necessary to excite the nebula. This large discrepancy suggests that the nebula is a faint ionization echo excited by a mildly active nucleus that has declined by ∼3 orders of magnitude over the past 20,000-200,000 yr. In many ways this nebula resembles the prototypical ''Hanny's Voorwerp'' near IC 2497, but its size is 3× smaller and its [O III] luminosity ∼100× lower. We propose that it be classified as an extended emission-line region (EELR). The [O III] nebula is then the lowest-luminosity ionization echo and EELR discovered so far, indicative of recent, probably sputtering AGN activity of Seyfert-like intensity in NGC 7252

  12. Rats Can Acquire Conditional Fear of Faint Light Leaking through the Acrylic Resin Used to Mount Fiber Optic Cannulas

    Science.gov (United States)

    Eckmier, Adam; de Marcillac, Willy Daney; Maître, Agnès; Jay, Thérèse M.; Sanders, Matthew J.; Godsil, Bill P.

    2016-01-01

    Rodents are exquisitely sensitive to light and optogenetic behavioral experiments routinely introduce light-delivery materials into experimental situations, which raises the possibility that light could leak and influence behavioral performance. We examined whether rats respond to a faint diffusion of light, termed caplight, which emanated through…

  13. Indoor radio measurement and planning for UMTS/HSDPA with antennas

    Science.gov (United States)

    Eheduru, Marcellinus

    Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, approximately 70-80% of the HSDPA traffic is estimated to originate from inside buildings. Thus for network operators, indoor coverage has become a necessity for technical and business reasons. Macro-cellular (outdoor) to indoor coverage is a natural inexpensive way of providing network coverage inside the buildings. However, it does not guarantee sufficient link quality required for optimal HSDPA operation. On the contrary, deploying a dedicated indoor system may be far too expensive from an operator's point of view. In this thesis, the concept is laid for the understanding of indoor radio wave propagation in a campus building environment which could be used to plan and improve outdoor-to-indoor UMTS/HSDPA radio propagation performance. It will be shown that indoor range performance depends not only on the transmit power of an indoor antenna, but also on the product's response to multipath and obstructions in the environment along the radio propagation path. An extensive measurement campaign will be executed in different indoor environments analogous to easy, medium and hard radio conditions. The effects of walls, ceilings, doors and other obstacles on measurement results would be observed. Chapter one gives a brief introduction to the evolution of UMTS and HSDPA. It goes on to talk about radio wave propagation

  14. NAC/NINE Program Building Radio Jove's and Brining Radio Astronomy to the Community

    Science.gov (United States)

    Ramona Gallego, Angelina; Paul Gueye, Al Amin Kabir,

    2018-01-01

    During the course of the 8-week program, (NINE, National and International Non-Traditional Exchange Program), the summer was spent in Socorro, New Mexico, working on building a Radio Jove, and making observations with the Radio Jove as well as working on learning project management practices in order to take the CAPM PMI Exam. The NINE built the Radio Jove’s at the same time and in doing so learned to replicate it to teach it to others. The final portion of the program that was worked on was to create a NINE hub and do outreach with the community teaching them about radio astronomy and teaching students how to build their own Radio Jove’s and make observations. An important aspect of the summer program was to bring back the knowledge received about radio astronomy and teach it to high school students with the help of the institution each NINE participants came from.

  15. 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)

  16. 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 ...

  17. Revealing a comet-like shape of the faint periphery of the nearby galaxy M 32

    Science.gov (United States)

    Georgiev, Ts. B.

    2016-02-01

    We performed BVRI photometry of the galaxy M 32 building images and isophote maps in magnitudes and in color indexes. While searching for the faint thick disk of M 32 we apply median filtering with aperture of 7.3 arcmin to detach the residual image of M 32 and its periphery above the surrounding magnitude or color background. The residual images in all photometric systems show that the periphery of M 32 possesses a comet-like shape with a tail oriented to SSE, in a direction opposite to the direction of M 110. The images calibrated in color indexes (b - v) and (b - v)+(r - i) show that the tail is redder than the local median background. The residual images in color indexes show that the red tail broadens and curves in direction towards S and SW. Simultaneously, the brightest part of M 32 occurs bounded from NW-NE-SE sides by a sickle-like formation with a significantly lower red color index. Generally, we do not find a faint thick disk of M 32. However, the comet-like shape on the periphery of M 32, especially as a formation with an increased red color index, provokes involuntarily the impression that the satellite M 32 overtakes the Andromeda galaxy. The redshifts show that the intimacy velocity of M 32 and Andromeda galaxy is about 100 km/s.

  18. The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VI. Radio Constraints on a Relativistic Jet and Predictions for Late-time Emission from the Kilonova Ejecta

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, K. D.; Berger, E.; Fong, W.; Williams, P. K. G.; Guidorzi, C.; Margutti, R.; Metzger, B. D.; Annis, J.; Blanchard, P. K.; Brout, D.; Brown, D. A.; Chen, H. -Y.; Chornock, R.; Cowperthwaite, P. S.; Drout, M.; Eftekhari, T.; Frieman, J.; Holz, D. E.; Nicholl, M.; Rest, A.; Sako, M.; Soares-Santos, M.; Villar, V. A.

    2017-10-16

    We present Very Large Array (VLA) and Atacama Large Millimeter/sub-millimeter Array ALMA radio observations of GW\\,170817, the first Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo gravitational wave (GW) event from a binary neutron star merger and the first GW event with an electromagnetic (EM) counterpart. Our data include the first observations following the discovery of the optical transient at both the centimeter ($13.7$ hours post merger) and millimeter ($2.41$ days post merger) bands. We detect faint emission at 6 GHz at 19.47 and 39.23 days after the merger, but not in an earlier observation at 2.46 d. We do not detect cm/mm emission at the position of the optical counterpart at frequencies of 10-97.5 GHz at times ranging from 0.6 to 30 days post merger, ruling out an on-axis short gamma-ray burst (SGRB) for energies $\\gtrsim 10^{48}$ erg. For fiducial SGRB parameters, our limits require an observer viewer angle of $\\gtrsim 20^{\\circ}$. The radio and X-ray data can be jointly explained as the afterglow emission from an SGRB with a jet energy of $\\sim 10^{49}-10^{50}$ erg that exploded in a uniform density environment with $n\\sim 10^{-4}-10^{-2}$ cm$^{-3}$, viewed at an angle of $\\sim 20^{\\circ}-40^{\\circ}$ from the jet axis. Using the results of our light curve and spectral modeling, in conjunction with the inference of the circumbinary density, we predict the emergence of late-time radio emission from the deceleration of the kilonova (KN) ejecta on a timescale of $\\sim 5-10$ years that will remain detectable for decades with next-generation radio facilities, making GW\\,170817 a compelling target for long-term radio monitoring.

  19. 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....

  20. 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...

  1. Teaching the Thrill of Discovery: Student Exploration of Ultra-Faint Dwarf Galaxies with the NOAO Data Lab

    Science.gov (United States)

    Olsen, Knut; Walker, Constance E.; Smith, Blake; NOAO Data Lab Team

    2018-01-01

    We describe an activity aimed at teaching students how ultra-faint Milky Way dwarf galaxies are typically discovered: through filtering of optical photometric catalogs and cross-examination with deep images. The activity, which was developed as part of the Teen Astronomy Café program (https://teensciencecafe.org/cafes/az-teen-astronomy-cafe-tucson/), uses the NOAO Data Lab (http://datalab.noao.edu) and other professional-grade tools to lead high school students through exploration of the object catalog and images from the Survey of the Magellanic Stellar History (SMASH). The students are taught how to use images and color-magnitude diagrams to analyze and interpret stellar populations of increasing complexity, including those of star clusters and the Magellanic Clouds, and culminating with the discovery of the Hydra II ultra-faint dwarf galaxy. The tools and datasets presented allow the students to explore and discover other known stellar systems, as well as unknown candidate star clusters and dwarf galaxies. The ultimate goal of the activity is to give students insight into the methods of modern astronomical research and to allow them to participate in the thrill of discovery.

  2. 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.

  3. 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

  4. XMM-Newton and Swift spectroscopy of the newly discovered very faint X-ray transient IGR J17494-3030

    NARCIS (Netherlands)

    Armas Padilla, M.; Wijnands, R.; Degenaar, N.

    2013-01-01

    A growing group of low-mass X-ray binaries are found to be accreting at very faint X-ray luminosities of <1036 erg s−1 (2-10 keV). One such system is the new X-ray transient IGR J17494-3030. We present Swift and XMM-Newton observations obtained during its 2012 discovery outburst. The Swift

  5. Measurement Technique in Radio Frequency Interference (RFI) Study for Radio Astronomy Purposes

    International Nuclear Information System (INIS)

    Roslan Umar; Roslan Umar; Nor Hazmin Sabri; Zainol Abidin Ibrahim; Zamri Zainal Abidin; Asyaari Muhamad

    2015-01-01

    In this paper, we will review our method in making measurements of radio frequency interference (RFI) in order to investigate the sereneness of interference in selected radio interference in Malaysia and Thailand. The selected site are University of Malaya (UM), Universiti Pendidikan Sultan Idris (UPSI), Ubon (UB) and Chiang Mai (CM). The major RFI affecting radio astronomical windows below 1 GHz are electronic equipment system specifically radio navigation between 73.1 MHz and 75.2 MHz, radio broadcasting (151 MHz, 151.8 MHz and 152 MHz), aeronautical navigation (245.5 MHz, 248.7 MHz and 249 MHz and also fixed mobile at 605 MHz, 608.3 MHz, 612.2 MHz, 613.3 MHz. It is obviously showed that all sites within this region are free from interference between 320MHz and 330 MHz and is the best specific region to be considered for solar burst monitoring. We also investigate the effect of RFI on discovery of solar burst. (author)

  6. 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

  7. FAINT NEAR-ULTRAVIOLET/FAR-ULTRAVIOLET STANDARDS FROM SWIFT/UVOT, GALEX, AND SDSS PHOTOMETRY

    International Nuclear Information System (INIS)

    Siegel, Michael H.; Hoversten, Erik A.; Roming, Peter W. A.; Brown, Peter

    2010-01-01

    At present, the precision of deep ultraviolet photometry is somewhat limited by the dearth of faint ultraviolet standard stars. In an effort to improve this situation, we present a uniform catalog of 11 new faint (u ∼ 17) ultraviolet standard stars. High-precision photometry of these stars has been taken from the Sloan Digital Sky Survey and Galaxy Evolution Explorer archives and combined with new data from the Swift Ultraviolet Optical Telescope to provide precise photometric measures extending from the near-infrared to the far-ultraviolet. These stars were chosen because they are known to be hot (20, 000 eff < 50, 000 K) DA white dwarfs with published Sloan spectra that should be photometrically stable. This careful selection allows us to compare the combined photometry and Sloan spectroscopy to models of pure hydrogen atmospheres to both constrain the underlying properties of the white dwarfs and test the ability of white dwarf models to predict the photometric measures. We find that the photometry provides good constraints on white dwarf temperatures, which demonstrates the ability of Swift/UVOT to investigate the properties of hot luminous stars. We further find that the models reproduce the photometric measures in all 11 passbands to within their systematic uncertainties. Within the limits of our photometry, we find the standard stars to be photometrically stable. This success indicates that the models can be used to calibrate additional filters to our standard system, permitting easier comparison of photometry from heterogeneous sources. The largest source of uncertainty in the model fitting is the uncertainty in the foreground reddening curve, a problem that is especially acute in the UV.

  8. 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.)

  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. Radio propagation measurement and channel modelling

    CERN Document Server

    Salous, Sana

    2013-01-01

    While there are numerous books describing modern wireless communication systems that contain overviews of radio propagation and radio channel modelling, there are none that contain detailed information on the design, implementation and calibration of radio channel measurement equipment, the planning of experiments and the in depth analysis of measured data. The book would begin with an explanation of the fundamentals of radio wave propagation and progress through a series of topics, including the measurement of radio channel characteristics, radio channel sounders, measurement strategies

  11. Characterization of a Prototype Radio Frequency Space Environment Path Emulator for Evaluating Spacecraft Ranging Hardware

    Science.gov (United States)

    Mitchell, Jason W.; Baldwin, Philip J.; Kurichh, Rishi; Naasz, Bo J.; Luquette, Richard J.

    2007-01-01

    The Formation Flying Testbed (FFTB) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) provides a hardware-in-the-loop test environment for formation navigation and control. The facility is evolving as a modular, hybrid, dynamic simulation facility for end-to-end guidance, navigation and control (GN&C) design and analysis of formation flying spacecraft. The core capabilities of the FFTB, as a platform for testing critical hardware and software algorithms in-the-loop, have expanded to include S-band Radio Frequency (RF) modems for interspacecraft communication and ranging. To enable realistic simulations that require RF ranging sensors for relative navigation, a mechanism is needed to buffer the RF signals exchanged between spacecraft that accurately emulates the dynamic environment through which the RF signals travel, including the effects of the medium, moving platforms, and radiated power. The Path Emulator for Radio Frequency Signals (PERFS), currently under development at NASA GSFC, provides this capability. The function and performance of a prototype device are presented.

  12. New radio model in the fourth screen: radiovision, the radio that you can watch

    Directory of Open Access Journals (Sweden)

    Sandra CAVIA FRAILE

    2016-12-01

    Full Text Available The traditional radio is not strange to the social revolution that Internet and new technologies are raising. In recent years, the fourth screen has led the emergence of new models of radio, including Radiovision. The «radio that you can watch» intends to change and innovate the radio broadcasting media to offer a product that meets the multimedia requirements of users. However, currently, the Radiovisión is still at an early stage and it has many aspects that it should improve and care, as the contents and the staging. It is a big chance for the radio that poses challenges and opportunities both for journalism and journalists.

  13. Transistor Radio Receivers; Radio and Television Service, Intermediate: 9785.04.

    Science.gov (United States)

    Dade County Public Schools, Miami, FL.

    The course outlined is one of the required courses in the Radio and Television Service Curriculum. Mastery of the skills in Basic Radio Circuits and Vacuum Tube AM Troubleshooting (9785.03) is a prerequisite. Eight blocks of instruction are divided into several units each. The instruction blocks are: orientation, fundamentals of transistor…

  14. Analiza efikasnosti funkcionalnih radio-komunikacionih centara / The efficiency analysis of functional radio communication centers

    Directory of Open Access Journals (Sweden)

    Saša M. Devetak

    2008-10-01

    Full Text Available U radu je prikazan jedan pristup u analizi efikasnosti radio-komunikacionih centara funkcionalnog telekomunikacionog sistema, kao što je vojni sistem veza. Radio-komunikacioni centar modelovan je kao sistem masovnog opsluživanja. Opisana su stanja sistema i parametri i izveden izraz za određivanje verovatnoće opsluživanja radio-komunikacionog centra, kao kriterijuma za ocenu efikasnosti. Predstavljen je, takođe, model, odnosno izrazi za kvantitativnu analizu efikasnosti radio- komunikacionih centara u uslovima elektronskih dejstava. / One approach in the analysis of efficiency of radio communication centers of functional telecommunication systems (for example Military Systems has been shown in this article. A radio communication centre has been presented as a model of mass service systems. The system states and its parameters have been described as well as the resulting formula for determining service probability as a criterion for efficiency evaluation. A model and the formulae for quantitative analysis of efficiency in electronic warfare have been presented as well.

  15. Wide Field Radio Transient Surveys

    Science.gov (United States)

    Bower, Geoffrey

    2011-04-01

    The time domain of the radio wavelength sky has been only sparsely explored. Nevertheless, serendipitous discovery and results from limited surveys indicate that there is much to be found on timescales from nanoseconds to years and at wavelengths from meters to millimeters. These observations have revealed unexpected phenomena such as rotating radio transients and coherent pulses from brown dwarfs. Additionally, archival studies have revealed an unknown class of radio transients without radio, optical, or high-energy hosts. The new generation of centimeter-wave radio telescopes such as the Allen Telescope Array (ATA) will exploit wide fields of view and flexible digital signal processing to systematically explore radio transient parameter space, as well as lay the scientific and technical foundation for the Square Kilometer Array. Known unknowns that will be the target of future transient surveys include orphan gamma-ray burst afterglows, radio supernovae, tidally-disrupted stars, flare stars, and magnetars. While probing the variable sky, these surveys will also provide unprecedented information on the static radio sky. I will present results from three large ATA surveys (the Fly's Eye survey, the ATA Twenty CM Survey (ATATS), and the Pi GHz Survey (PiGSS)) and several small ATA transient searches. Finally, I will discuss the landscape and opportunities for future instruments at centimeter wavelengths.

  16. 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.)

  17. Flexible Adaptation in Cognitive Radios

    CERN Document Server

    Li, Shujun

    2013-01-01

    This book provides an introduction to software-defined radio and cognitive radio, along with methodologies for applying knowledge representation, semantic web, logic reasoning and artificial intelligence to cognitive radio, enabling autonomous adaptation and flexible signaling. Readers from the wireless communications and software-defined radio communities will use this book as a reference to extend software-defined radio to cognitive radio, using the semantic technology described. Readers with a background in semantic web and artificial intelligence will find in this book the application of semantic web and artificial intelligence technologies to wireless communications. For readers in networks and network management, this book presents a new approach to enable interoperability, collaborative optimization and flexible adaptation of network components. Provides a comprehensive ontology covering the core concepts of wireless communications using a formal language; Presents the technical realization of using a ...

  18. THE FLUENCE AND DISTANCE DISTRIBUTIONS OF FAST RADIO BURSTS

    International Nuclear Information System (INIS)

    Vedantham, H. K.; Ravi, V.; Hallinan, G.; Shannon, R. M.

    2016-01-01

    Fast radio bursts (FRB) are millisecond-duration radio pulses with apparent extragalactic origins. All but two of the FRBs have been discovered using the Parkes dish, which employs multiple beams formed by an array of feed horns on its focal plane. In this paper, we show that (i) the preponderance of multiple-beam detections and (ii) the detection rates for varying dish diameters can be used to infer the index α of the cumulative fluence distribution function (the log N –log F function: α = 1.5 for a non-evolving population in a Euclidean universe). If all detected FRBs arise from a single progenitor population, multiple-beam FRB detection rates from the Parkes telescope yield the constraint 0.52 < α < 1.0 with 90% confidence. Searches at other facilities with different dish sizes refine the constraint to 0.5 < α < 0.9. Our results favor FRB searches with smaller dishes, because for α < 1 the gain in field of view for a smaller dish is more important than the reduction in sensitivity. Further, our results suggest that (i) FRBs are not standard candles, and (ii) the distribution of distances to the detected FRBs is weighted toward larger distances. If FRBs are extragalactic, these results are consistent with a cosmological population, which would make FRBs excellent probes of the baryonic content and geometry of the universe.

  19. 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.

  20. Transient behaviour of EIT and EIA in an optical-radio two-photon coupling configuration

    Science.gov (United States)

    Li, Xiaoli; Yang, Zicai; Shang, Yaxuan

    2012-11-01

    Both electromagnetically induced absorption (EIA) and transparency (EIT) can be obtained in a modified quasi-lambda four level system consisting of an optical-radio two-photon coupling field and a probing field. A physical account of EIA and EIT is given in terms of a transient state picture in this paper. It can be seen that the optical coupling field in this quasi-lambda four level system has a crucial effect on the forming of EIA and EIT. An EIA is observed under a resonant optical coupling and it evolves into an EIT when there is a detuning.

  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. 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.

  3. IA-Regional-Radio - Social Network for Radio Recommendation

    Science.gov (United States)

    Dziczkowski, Grzegorz; Bougueroua, Lamine; Wegrzyn-Wolska, Katarzyna

    This chapter describes the functions of a system proposed for the music hit recommendation from social network data base. This system carries out the automatic collection, evaluation and rating of music reviewers and the possibility for listeners to rate musical hits and recommendations deduced from auditor's profiles in the form of regional Internet radio. First, the system searches and retrieves probable music reviews from the Internet. Subsequently, the system carries out an evaluation and rating of those reviews. From this list of music hits, the system directly allows notation from our application. Finally, the system automatically creates the record list diffused each day depending on the region, the year season, the day hours and the age of listeners. Our system uses linguistics and statistic methods for classifying music opinions and data mining techniques for recommendation part needed for recorded list creation. The principal task is the creation of popular intelligent radio adaptive on auditor's age and region - IA-Regional-Radio.

  4. Faint nebulosities in the vicinity of the Magellanic H I Stream

    International Nuclear Information System (INIS)

    Johnson, P.G.; Meaburn, J.; Osman, A.M.I.

    1982-01-01

    Very deep Hα image tube photographs with a wide-field filter camera have been taken of the Magellanic H I Stream. A diffuse region of emission has been detected. Furthermore a mosaic of high contrast prints of IIIaJ survey plates taken with the SRC Schmidt, has been compiled over the same area. A complex region of faint, blue, filamentary nebulosity has been revealed. This appears to be reflection nebulosity either in the galactic plane or less probably, in the vicinity of the Large Magellanic Cloud. A deep Hα 1.2-m Schmidt photograph of these blue filaments reinforces the suggestion that they are reflection nebulae. The reflection and emission nebulosities in this vicinity have been compared to each other and the Magellanic H I Stream. The diffuse region of Hα emission is particularly well correlated with the Stream. (author)

  5. 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...

  6. SURVEY PERILAKU MENDENGARKAN RADIO DI JAKARTA

    Directory of Open Access Journals (Sweden)

    Siti Dewi Sri Ratna Sari

    2016-05-01

    Full Text Available This research is to find out the profile of radio broadcasting’s content in Jakarta and to look for measured data as the parameter to assess radio broadcasting programs and the radio listeners profile in DKI Jakarta. The research methodology is survey with 1000 respondents as the sample with 2.24% margin of error and 95% credibility level. The sampling method used is Multistage Random Sampling from 5 out of 6 DKI Jakarta Province areas, except Thousand Islands Regency. Data collection technique used is face to face personal interview by giving gift to the respondents. Research result describes the profile of radio listeners is middle class productive age working men and women whose prime reason listening to radio is music as their pastime. Respondents are categorized as medium listeners with 1.87 hour as their average of listening to radio. Nevertheless, the prime time is covering the whole day both while they are listening at home and while they are mobile. Research found that respondents are already satisfied by the radio programs in Jakarta. The competition of radio stations in Jakarta based on their listeners is Gen FM at the top with 44.6%, followed by Bens Radio, Elshinta, I-Radio, Prambors, CBB, and so on. An interesting finding is that radio’s function to deliver social communication is fulfilled by placing religious speech and information as the second and the third most preferable programs with 9.8% and 8.0% below music program.   Penelitian ini bertujuan untuk mengetahui profil isi siaran radio yang selama ini bersiaran di Jakarta sekaligus mencari data terukur sebagai parameter untuk melakukan penilaian terhadap program isi siaran radio, termasuk pola mendengarkan radio pendengar radio seperti durasi dan tempat di provinsi DKI Jakarta. Metode penelitian berupa survei dengan sampel yang diambil sebanyak 1000 responden, margin of error 2.24% dan tingkat kepercayaan 95%. Metode pengambilan sampel dalam penelitian ini adalah dengan

  7. 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...

  8. Studying The Spectral Shape And The X-ray/uv Variability Of Active Galactic Nuclei With Data From Swift And Xmm Archives

    Science.gov (United States)

    Turriziani, Sara

    2011-01-01

    Many efforts have been made in understanding the underlying origin of variability in Active Galactic Nuclei (AGN), but at present they could give still no conclusive answers. Since a deeper knowledge of variability will enable to understand better the accretion process onto supermassive black holes, I built the first ensemble struction function analysis of the X-ray variability of samples of quasars with data from Swift and XMM-Newton archives in order to study the average properties of their variability. Moreover, it is known that UV and X-ray luminosities of quasars are correlated and recent studies quantified this relation across 5 orders of magnitude. In this context, I presents results on the X-ray/UV ratio from simultaneous observations in UV and X-ray bands of a sample of quasars with data from XMM-Newton archive. Lastly, I will present a complete sample of Swift/SDSS faint blazars and other non-thermal dominated AGNs. I used this sample to calculate the general statistical properties of faint blazars and radio galaxies and in particular their Radio LogN-LogS with fluxes down to 10 mJy, in order to gain knowledge on the contribution to Cosmic Microwave Background (CMB) and gamma-ray background radiation from the faint tail of the radio population. I acknowledge financial support through Grant ASI I/088/06/0.

  9. Unseen cosmos the universe in radio

    CERN Document Server

    Graham-Smith, Francis

    2013-01-01

    Radio telescopes have transformed our understanding of the Universe. Pulsars, quasars, Big Bang cosmology: all are discoveries of the new science of radio astronomy. Here, Francis Graham-Smith describes the birth, development, and maturity of radio astronomy, from the first discovery of cosmic radio waves to its present role as a major part of modern astronomy. Radio is part of the electromagnetic spectrum, covering infra-red, visible light, ultraviolet, X-rays, and gamma-rays, and Graham-Smith explains why it is that radio waves give us a unique view of the Universe. Tracing the development o

  10. Implementing a DVB-T/H Receiver on a Software-Defined Radio Platform

    Directory of Open Access Journals (Sweden)

    Yong Jiang

    2009-01-01

    Full Text Available Digital multimedia broadcasting is available in more and more countries with various forms. One of the most successful forms is Digital Video Broadcasting for Terrestrial (DVB-T, which has been deployed in most countries of the world for years. In order to bring the digital multimedia broadcasting services to battery-powered handheld receivers in a mobile environment, Digital Video Broadcasting for Handheld (DVB-H has been formally adopted by ETSI. More advanced and complex digital multimedia broadcasting systems are under development, for example, the next generation of DVB-T, a.k.a. DVB-T2. Current commercial DVB-T/H receivers are usually built upon dedicated application-specific integrated circuits (ASICs. However, ASICs are not flexible for incoming evolved standards and less overall-area efficient since they cannot be efficiently reused and shared among different radio standards, when we integrate a DVB-T/H receiver into a mobile phone. This paper presents an example implementation of a DVB-T/H receiver on the prototype of Infineon Technologies' Software-Defined Radio (SDR platform called MuSIC (Multiple SIMD Cores, which is a DSP-centered and accelerator-assisted architecture and aims at battery-powered mass-market handheld terminals.

  11. Radio Telescopes to Keep Sharp Eye on Mars Lander

    Science.gov (United States)

    2008-05-01

    As NASA's Phoenix Mars Lander descends through the Red Planet's atmosphere toward its landing on May 25, its progress will be scrutinized by radio telescopes from the National Radio Astronomy Observatory (NRAO). At NRAO control rooms in Green Bank, West Virginia, and Socorro, New Mexico, scientists, engineers and technicians will be tracking the faint signal from the lander, 171 million miles from Earth. The GBT Robert C. Byrd Green Bank Telescope CREDIT: NRAO/AUI/NSF To make a safe landing, Phoenix must make a risky descent, slowing down from nearly 13,000 mph at the top of the Martian atmosphere to only 5 mph in the final seconds before touchdown. NASA officials point out that fewer than half of all Mars landing missions have been successful, but the scientific rewards of success are worth the risk. Major events in the spacecraft's atmospheric entry, descent and landing will be marked by changes in the Doppler Shift in the frequency of the vehicle's radio signal. Doppler Shift is the change in frequency caused by relative motion between the transmitter and receiver. At Green Bank, NRAO and NASA personnel will use the giant Robert C. Byrd Green Bank Telescope (GBT) to follow the Doppler changes and verify that the descent is going as planned. The radio signal from Phoenix is designed to be received by other spacecraft in Mars orbit, then relayed to Earth. However, the GBT, a dish antenna with more than two acres of collecting surface and highly-sensitive receivers, can directly receive the transmissions from Phoenix. "We'll see the frequency change as Phoenix slows down in the Martian atmosphere, then there will be a big change when the parachute deploys," said NRAO astronomer Frank Ghigo. When the spacecraft's rocket thrusters slow it down for its final, gentle touchdown, its radio frequency will stabilize, Ghigo said. "We'll have confirmation of these major events through our direct reception several seconds earlier than the controllers at NASA's Jet Propulsion

  12. Combined synthetic x-ray and radio observations of simulated radio jets

    Energy Technology Data Exchange (ETDEWEB)

    Tregillis, I. L. (Ian L.); Jones, T. W. (Thomas Walter),; Ryu, Dongsu

    2004-01-01

    We present results from an extensive synthetic observation analysis of numerically-simulated radio galaxy jets. This is the first such analysis to be based on simulations with sufficient physical detail to allow the application of standard observational analysis techniques to simulated radio galaxies. Here we focus on extracting magnetic field properties from nonthermal intensity information. We study field values obtained via the combination of synchrotron radio and inverse-Compton X-ray data as well as those from the minimum-energy approach. The combined radio/X-ray technique provides meaningful information about the field. The minimum-energy approach retrieves reasonable field estimates in regions physically close to the minimum-energy partitioning, though the technique is highly susceptible to deviations from the underlying assumptions. We also look at how the two field measurement techniques might be combined to provide a rough measure of the actual energy in particles and fields. A full report on this work can be found in the Astrophysical Journal, v601, p778.

  13. 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....

  14. Natural selection promotes antigenic evolvability.

    Science.gov (United States)

    Graves, Christopher J; Ros, Vera I D; Stevenson, Brian; Sniegowski, Paul D; Brisson, Dustin

    2013-01-01

    The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed 'cassettes' that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections.

  15. Natural selection promotes antigenic evolvability.

    Directory of Open Access Journals (Sweden)

    Christopher J Graves

    Full Text Available The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed 'cassettes' that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish

  16. Radio frequency ablation of small renal tumors:: intermediate results.

    Science.gov (United States)

    Hwang, J J; Walther, M M; Pautler, S E; Coleman, J A; Hvizda, J; Peterson, James; Linehan, W M; Wood, B J

    2004-05-01

    With evolving radio frequency technology, the clinical application of radio frequency ablation (RFA) has been actively investigated in the treatment for small renal tumors. We present our intermediate patient outcomes after RFA. Since January 2001, 17 patients with a total of 24 hereditary renal tumors ranging from 1.2 to 2.85 cm were treated with RFA using the 200 W Cool-tip RF System (Radionics, Burlington, Massachusetts) under laparoscopic (9) or percutaneous (8) guidance and had a minimum 1-year followup. A percutaneous approach was considered unsuitable if kidney tumors were contiguous to bowel, ureter or large vessels. Treatment eligibility criteria included an average tumor diameter of less than 3.0 cm, tumor growth during 1 year and solid appearance with contrast enhancement (HU change greater than 20) on computerized tomography (CT). Postoperative followup consisted of CT with and without intravenous contrast, and renal function assessment at regular intervals. Median patient age was 38 years (range 20 to 51). At a median followup of 385 days (range 342 to 691), median tumor or thermal lesion diameter decreased from 2.26 to 1.62 cm (p = 0.0013), and only 1 lesion (4%), which was located centrally near the hilum, exhibited contrast enhancement (HU change greater than 10) on CT at 12 months. Of the 15 renal tumors ablated laparoscopically, 13 were in direct contact with the bowel and 2 were abutting the ureter, necessitating mobilization before RFA. Laparoscopic ultrasound was used to guide radio frequency electrode placement and monitor the ablation process in these cases. Operative time and intraoperative blood loss (mean +/- standard mean of error) were 243 +/- 29 minutes and 67 +/- 9 cc, respectively. In 1 patient whose ureter was adherent to the tumor a ureteropelvic junction obstruction developed after laparoscopic RFA, requiring open repair. At the minimum 1-year followup 23 of 24 ablated tumors lacked contrast uptake on CT, meeting our radiographic

  17. LOW-POWER RADIO GALAXIES IN THE DISTANT UNIVERSE: A SEARCH FOR FR I AT 1 < z < 2 IN THE COSMOS FIELD

    International Nuclear Information System (INIS)

    Chiaberge, Marco; Tremblay, Grant; Macchetto, F. Duccio; Sparks, W. B.; Capetti, Alessandro; Tozzi, Paolo

    2009-01-01

    We present a search for FR I radio galaxies between 1 < z < 2 in the COSMOS field. In absence of spectroscopic redshift measurements, the selection method is based on multiple steps which make use of both radio and optical constraints. The basic assumptions are that (1) the break in radio power between low-power FR Is and the more powerful FR IIs does not change with redshift, and (2) that the photometric properties of the host galaxies of low-power radio galaxies in the distant universe are similar to those of FR IIs in the same redshift bin, as is the case for nearby radio galaxies. We describe the results of our search, which yields 37 low-power radio galaxy candidates that are possibly FR Is. We show that a large fraction of these low-luminosity radio galaxies display a compact radio morphology that does not correspond to the FR I morphological classification. Furthermore, our objects are apparently associated with galaxies that show clear signs of interactions, at odds with the typical behavior observed in low-z FR I hosts. The compact radio morphology might imply that we are observing intrinsically small and possibly young objects that will eventually evolve into the giant FR Is we observe in the local universe. One of the objects appears as pointlike in Hubble Space Telescope (HST) images. This might belong to a population of FR I-QSOs, which however would represent a tiny minority of the overall population of high-z FR Is. As for the local FR Is, a large fraction of our objects are likely to be associated with groups or clusters, making them 'beacons' for high-redshift clusters of galaxies. Our search for candidate high-z FR Is we present in this paper constitutes a pilot study for objects to be observed with future high-resolution and high-sensitivity instruments such as the EVLA and ALMA in the radio band, HST/WFC3 in the optical and IR, James Webb Space Telescope in the IR, as well as future generation X-ray satellites.

  18. Hydra II: A Faint and Compact Milky Way Dwarf Galaxy Found in the Survey of the Magellanic Stellar History

    NARCIS (Netherlands)

    Martin, Nicolas F.; Nidever, David L.; Besla, Gurtina; Olsen, Knut; Walker, Alistair R.; Vivas, A. Katherina; Gruendl, Robert A.; Kaleida, Catherine C.; Muñoz, Ricardo R.; Blum, Robert D.; Saha, Abhijit; Conn, Blair C.; Bell, Eric F.; Chu, You-Hua; Cioni, Maria-Rosa L.; de Boer, Thomas J. L.; Gallart, Carme; Jin, Shoko; Kunder, Andrea; Majewski, Steven R.; Martinez-Delgado, David; Monachesi, Antonela; Monelli, Matteo; Monteagudo, Lara; Noël, Noelia E. D.; Olszewski, Edward W.; Stringfellow, Guy S.; van der Marel, Roeland P.; Zaritsky, Dennis

    We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact ({{r}h}=68 ± 11 pc) and faint ({{M}V}=-4.8 ± 0.3),

  19. Radio morphing - towards a full parametrisation of the radio signal from air showers

    Science.gov (United States)

    Zilles, A.; Charrier, D.; Kotera, K.; Le Coz, S.; Martineau-Huynh, O.; Medina, C.; Niess, V.; Tueros, M.; de Vries, K.

    2017-12-01

    Over the last decades, radio detection of air showers has been established as a detection technique for ultra-high-energy cosmic-rays impinging on the Earth's atmosphere with energies far beyond LHC energies. Today’s second-generation of digital radio-detection experiments, as e.g. AERA or LOFAR, are becoming competitive in comparison to already standard techniques e.g. fluorescence light detection. Thanks to a detailed understanding of the physics of the radio emission in extensive air showers, simulations of the radio signal are already successfully tested and applied in the reconstruction of cosmic rays. However the limits of the computational power resources are easily reached when it comes to computing electric fields at the numerous positions requested by large or dense antenna arrays. In the case of mountainous areas as e.g. for the GRAND array, where 3D shower simulations are necessary, the problem arises with even stronger acuity. Therefore we developed a full parametrisation of the emitted radio signal on the basis of generic shower simulations which will reduce the simulation time by orders of magnitudes. In this talk we will present this concept after a short introduction to the concept of the radio detection of air-shower induced by cosmic rays.

  20. 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.

  1. STAR FORMATION RATES FOR STARBURST GALAXIES FROM ULTRAVIOLET, INFRARED, AND RADIO LUMINOSITIES

    International Nuclear Information System (INIS)

    Sargsyan, Lusine A.; Weedman, Daniel W.

    2009-01-01

    We present a comparison of star formation rates (SFR) determined from mid-infrared 7.7 μm polycyclic aromatic hydrocarbon (PAH) luminosity [SFR(PAH)], from 1.4 GHz radio luminosity [SFR(radio)], and from far-ultraviolet luminosity [SFR(UV)] for a sample of 287 starburst galaxies with z ν (7.7 μm)] - 42.57 ± 0.2, for SFR in M sun yr -1 and νL ν (7.7 μm) the luminosity at the peak of the 7.7 μm PAH feature in erg s -1 , is found to agree with SFR(radio). Comparing with SFR(UV) determined independently from ultraviolet observations of the same sources with the Galaxy Evolution Explorer mission (not corrected for dust extinction), the median log [SFR(PAH)/SFR(UV)] = 1.67, indicating that only 2% of the ultraviolet continuum typically escapes extinction by dust within a starburst. This ratio SFR(PAH)/SFR(UV) depends on infrared luminosity, with the form log [SFR(PAH)/SFR(UV)] = (0.53 ± 0.05)log [νL ν (7.7 μm)] - 21.5 ± 0.18, indicating that more luminous starbursts are also dustier. Using our adopted relation between νL ν (7.7 μm) and L ir , this becomes log [SFR(PAH)/SFR(UV)]= (0.53 ± 0.05)log L ir - 4.11 ± 0.18, for L ir in L sun . Only blue compact dwarf galaxies show comparable or greater SFR(UV) compared to SFR(PAH). We also find that the ratio SFR(PAH)/SFR(UV) is similar to that in infrared-selected starbursts for a sample of Markarian starburst galaxies originally selected using optical classification, which implies that there is no significant selection effect in SFR(PAH)/SFR(UV) using starburst galaxies discovered by Spitzer. These results indicate that SFRs determined with ultraviolet luminosities require dust corrections by a factor of ∼10 for typical local starbursts but this factor increases to >700 for the most luminous starbursts at z ∼ 2.5. Application of this factor explains why the most luminous starbursts discovered by Spitzer at z ∼ 2.5 are optically faint; with this amount of extinction, the optical magnitude of a starburst

  2. On the evaluation of Web Radio

    OpenAIRE

    Field, A.N.; Hartel, Pieter H.

    2001-01-01

    We develop an evaluation method for Web radio, and perform it to see what we can be learnt about seven prominent Web radio sites. We also evaluate a commercial FM radio station for control purposes. We present a taxonomy of Web radio, and we give our observations and conclusions on this evaluation.

  3. 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.)

  4. 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,…

  5. Pair-Matching of Radio-Loud and Radio-Quiet AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Kozieł-Wierzbowska, Dorota [Astronomical Observatory, Jagiellonian University, Krakow (Poland); Stasińska, Grażyna [LUTH, Observatoire de Paris, Centre National de la Recherche Scientifique, Université Paris Diderot, Meudon (France); Vale Asari, Natalia [Departamento de Física–CFM, Universidade Federal de Santa Catarina, Florianópolis (Brazil); Sikora, Marek [Nicolaus Copernicus Astronomical Center, Warsaw (Poland); Goettems, Elisa [Departamento de Física–CFM, Universidade Federal de Santa Catarina, Florianópolis (Brazil); Wójtowicz, Anna, E-mail: dorota.koziel@uj.edu.pl [Astronomical Observatory, Jagiellonian University, Krakow (Poland)

    2017-11-07

    Active galactic nuclei (AGNs) are known to cover an extremely broad range of radio luminosities and the spread of their radio-loudness is very large at any value of the Eddington ratio. This implies very diverse jet production efficiencies which can result from the spread of the black hole spins and magnetic fluxes. Magnetic fluxes can be developed stochastically in the innermost zones of accretion discs, or can be advected to the central regions prior to the AGN phase. In the latter case there could be systematic differences between the properties of galaxies hosting radio-loud (RL) and radio-quiet (RQ) AGNs. In the former case the differences should be negligible for objects having the same Eddington ratio. To study the problem we decided to conduct a comparison study of host galaxy properties of RL and RQ AGNs. In this study we selected type II AGNs from SDSS spectroscopic catalogs. Our RL AGN sample consists of the AGNs appearing in the Best and Heckman (2012) catalog of radio galaxies. To compare RL and RQ galaxies that have the same AGN parameters we matched the galaxies in black hole mass, Eddington ratio and redshift. We compared several properties of the host galaxies in these two groups of objects like galaxy mass, color, concentration index, line widths, morphological type and interaction signatures. We found that in the studied group RL AGNs are preferentially hosted by elliptical galaxies while RQ ones are hosted by galaxies of later type. We also found that the fraction of interacting galaxies is the same in both groups of AGNs. These results suggest that the magnetic flux in RL AGNs is advected to the nucleus prior to the AGN phase.

  6. 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

  7. Circumstellar envelopes seen in radio (OH masers) and in the infrared observations (IRAS)

    International Nuclear Information System (INIS)

    David, Pedro-Correia-de-Matos

    1992-01-01

    Intermediate mass stars, namely from one to nine solar masses, eject mass into the surrounding interstellar medium at high rates (up to 1/10000 solar masses per year) in their late stages of evolution on the so called asymptotic giant branch (AGB). Indeed, the presence of a circumstellar envelope (CSE) composed of dust and gas is one of the principal features of the objects on the AGB. Because of the high opacity at visible wavelength of the CSE, most of these objects can only be observed at infrared and radio frequencies. This study was undertaken using infrared and radio data from a large sample of CSE sources. The infrared data was obtained from the infrared astronomical satellite (IRAS) data base. For a selection of IRAS objects, radio observations were made of the OH maser at 1612 and 1667 MHz at the Nancay radio telescope, France. This work consists in two parts, one is theoretical in nature, the other observational. The theoretical part is concerned with the modeling of IRAS low resolution spectra (LRS catalog) and IRAS photometry through the use of a radiative transfer code. Confrontation between models and data has yielded such results as a better definition of the grain optical properties and the behavior of the CSE as it evolves. A model of a shock wave (a possible lifting engine of the CSE) propagating in the atmosphere of Mira stars (AGB) is described. On the observational side, a large number of objects has been surveyed for the presence of OH masers at 1612 and 1667 MHz. A statistical analysis has established more clearly the evolutionary status of CSE and the OH maser characteristics. A compiling of detection rates for the occurrence of masers, average location of these masing CSEs in the Galaxy, and OH maser characteristics is reported for use in future work. (author) [fr

  8. Propagation engineering in radio links design

    CERN Document Server

    Ghasemi, Abdollah; Ghasemi, Farshid

    2013-01-01

    Propagation Engineering in Radio Link Design covers the basic principles of radiowaves propagation in a practical manner.  This fundamental understanding enables the readers to design radio links efficiently. This book elaborates on new achievements as well as recently developed propagation models.  This is in addition to a comprehensive overview of fundamentals of propagation in various scenarios. It examines theoretical calculations, approaches and applied procedures needed for radio links design. The authors study and analysis of the main propagation phenomena and its mechanisms based on the recommendations of International Telecommunications Union, (ITU). The book has been organized in 9 chapters and examines the role of antennas and passive reflectors in radio services, propagation mechanisms related to radar, satellite, short distance, broadcasting and trans-horizon radio links, with two chapters devoted to radio noise and main  parameters of radio link design. The book presents some 278 illustration...

  9. 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

  10. 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.

  11. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Kapińska, A. D.; Staveley-Smith, L.; Meurer, G. R.; For, B.-Q. [International Centre for Radio Astronomy Research (ICRAR), University of Western Australia, 35 Stirling Hwy, WA 6009 (Australia); Crocker, R. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Bhandari, S.; Callingham, J. R.; Gaensler, B. M.; Hancock, P. J.; Lenc, E. [ARC Centre of Excellence for All-Sky Astrophysics (CAASTRO), Sydney NSW (Australia); Hurley-Walker, N.; Seymour, N. [International Centre for Radio Astronomy Research (ICRAR), Curtin University, Bentley, WA 6102 (Australia); Offringa, A. R. [Netherlands Institute for Radio Astronomy (ASTRON), P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Hanish, D. J. [Spitzer Science Center, California Institute of Technology, MC 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Ekers, R. D.; Bell, M. E. [CSIRO Astronomy and Space Science (CASS), P.O. Box 76, Epping, NSW 1710 (Australia); Dwarakanath, K. S. [Raman Research Institute, Bangalore 560080 (India); Hindson, L. [Centre of Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Johnston-Hollitt, M. [School of Chemical and Physical Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140 (New Zealand); McKinley, B., E-mail: anna.kapinska@uwa.edu.au [School of Physics, The University of Melbourne, Parkville, VIC 3010 (Australia); and others

    2017-03-20

    We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free–free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGC 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154–231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z -direction (from the major axis).

  12. Geological Sulfur Isotopes Indicate Elevated OCS in the Archean Atmosphere, Solving the Faint Young Sun Paradox

    DEFF Research Database (Denmark)

    Ueno, Yuichiro; Johnson, Matthew Stanley; Danielache, Sebastian Oscar

    2009-01-01

    Distributions of sulfur isotopes in geological samples would provide a record of atmospheric composition if the mechanism producing the isotope effects could be described quantitatively. We determined the UV absorption spectra of 32SO2, 33SO2, and 34SO2 and use them to interpret the geological re......-rich, reducing Archean atmosphere. The radiative forcing, due to this level of OCS, is able to resolve the faint young sun paradox. Further, the decline of atmospheric OCS may have caused the late Archean glaciation....

  13. A Radio-Frequency-over-Fiber link for large-array radio astronomy applications

    International Nuclear Information System (INIS)

    Mena, J; Bandura, K; Cliche, J-F; Dobbs, M; Gilbert, A; Tang, Q Y

    2013-01-01

    A prototype 425-850 MHz Radio-Frequency-over-Fiber (RFoF) link for the Canadian Hydrogen Intensity Mapping Experiment (CHIME) is presented. The design is based on a directly modulated Fabry-Perot (FP) laser, operating at ambient temperature, and a single-mode fiber. The dynamic performance, gain stability, and phase stability of the RFoF link are characterized. Tests on a two-element interferometer built at the Dominion Radio Astrophysical Observatory for CHIME prototyping demonstrate that RFoF can be successfully used as a cost-effective solution for analog signal transport on the CHIME telescope and other large-array radio astronomy applications

  14. 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

  15. 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

    of the total energy output from the AGNs into jet kinetic energy versus radiant energy than do FR 2 sources. If this interpretation is correct, then this suggests that there is a fundamental difference in the central engine and/or in the immediate "accretion region" around the engine in FR 1 and FR 2 radio galaxies. We note also the absence of FR 1 sources with nuclear broad line regions and suggest that the absence of the BLR is tied to the absence of the "isotropic" nuclear UV continuum source in FR 1 sources. We put forth the possibility that the FR 1/FR 2 dichotomy (i.e., the observed differences in the properties of low- and high-power radio sources) is due to qualitative differences in the structural properties of the central engines in these two types of sources. Following early work by Rees et al. (1982), we suggest the possibility that FR 1 sources are produced when the central engine is fed at a lower accretion rate, leading to the creation of a source in which the ratio of radiant to jet bulk kinetic energy is low, while FR 2 sources are produced when the central engine is fed at a higher accretion rate, causing the central engine to deposit a higher fraction of its energy in radiant energy. We further suggest the possibility that associated differences in the spin properties of the central black hole between FR 1 (lower spin) and FR 2 (higher spin) sources may be responsible for the different collimation properties and Mach numbers of the jets produced by these two types of radio-loud galaxies. This scenario, although currently clearly speculative, is nicely consistent with our current picture of the triggering, feeding, environments, and evolution of powerful radio galaxies. This model allows for evolution of these properties with time for example, the mass accretion rate and BH spin may decline with time causing an FR 2 radio source or quasar to evolve into a FR 1 radio source.

  16. Perancangan Radio Streaming Edukasi (Studi Kasus Balai Pengembangan Media Radio YOGYAKARTA)

    OpenAIRE

    Nurwulan, Ayu Isni; Paputungan, Irving Vitra

    2009-01-01

    Pendidikan berkualitas sudah sewajarnya bisa dinikmati secara merata oleh semua orang. Mediapembelajaran secara audio yang selama ini disampaikan masih memiliki banyak keterbatasan, terutama padalingkup wilayah penyampaian. Dalam makalah ini, sebuah media pendidikan berbasis audio dengan cara laindiusulkan. Media tersebut bernama radio streaming. Pembuatan radio streaming memerlukan banyak analisissehingga perancangannya tepat. Hasil analisis dan perancangan yang disampaikan dalam makalah ini...

  17. Radio frequency identification enabled wireless sensing for intelligent food logistics.

    Science.gov (United States)

    Zou, Zhuo; Chen, Qiang; Chen, Qing; Uysal, Ismail; Zheng, Lirong

    2014-06-13

    Future technologies and applications for the Internet of Things (IoT) will evolve the process of the food supply chain and create added value of business. Radio frequency identifications (RFIDs) and wireless sensor networks (WSNs) have been considered as the key technological enablers. Intelligent tags, powered by autonomous energy, are attached on objects, networked by short-range wireless links, allowing the physical parameters such as temperatures and humidities as well as the location information to seamlessly integrate with the enterprise information system over the Internet. In this paper, challenges, considerations and design examples are reviewed from system, implementation and application perspectives, particularly with focus on intelligent packaging and logistics for the fresh food tracking and monitoring service. An IoT platform with a two-layer network architecture is introduced consisting of an asymmetric tag-reader link (RFID layer) and an ad-hoc link between readers (WSN layer), which are further connected to the Internet via cellular or Wi-Fi. Then, we provide insights into the enabling technology of RFID with sensing capabilities. Passive, semi-passive and active RFID solutions are discussed. In particular, we describe ultra-wideband radio RFID which has been considered as one of the most promising techniques for ultra-low-power and low-cost wireless sensing. Finally, an example is provided in the form of an application in fresh food tracking services and corresponding field testing results.

  18. Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

    International Nuclear Information System (INIS)

    Beck, R.; Drury, L.O.; Voelk, H.J.; Bogdan, T.J.

    1985-01-01

    The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium

  19. Onion-shell model for cosmic ray electrons and radio synchrotron emission in supernova remnants

    Science.gov (United States)

    Beck, R.; Drury, L. O.; Voelk, H. J.; Bogdan, T. J.

    1985-01-01

    The spectrum of cosmic ray electrons, accelerated in the shock front of a supernova remnant (SNR), is calculated in the test-particle approximation using an onion-shell model. Particle diffusion within the evolving remnant is explicity taken into account. The particle spectrum becomes steeper with increasing radius as well as SNR age. Simple models of the magnetic field distribution allow a prediction of the intensity and spectrum of radio synchrotron emission and their radial variation. The agreement with existing observations is satisfactory in several SNR's but fails in other cases. Radiative cooling may be an important effect, especially in SNR's exploding in a dense interstellar medium.

  20. 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.)

  1. 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...

  2. 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

  3. Reconfigurable radio systems network architectures and standards

    CERN Document Server

    Iacobucci, Maria Stella

    2013-01-01

    This timely book provides a standards-based view of the development, evolution, techniques and potential future scenarios for the deployment of reconfigurable radio systems.  After an introduction to radiomobile and radio systems deployed in the access network, the book describes cognitive radio concepts and capabilities, which are the basis for reconfigurable radio systems.  The self-organizing network features introduced in 3GPP standards are discussed and IEEE 802.22, the first standard based on cognitive radio, is described. Then the ETSI reconfigurable radio systems functional ar

  4. The effect of solar radio bursts on the GNSS radio occultation signals

    Science.gov (United States)

    Yue, Xinan; Schreiner, William S.; Kuo, Ying-Hwa; Zhao, Biqiang; Wan, Weixing; Ren, Zhipeng; Liu, Libo; Wei, Yong; Lei, Jiuhou; Solomon, Stan; Rocken, Christian

    2013-09-01

    radio burst (SRB) is the radio wave emission after a solar flare, covering a broad frequency range, originated from the Sun's atmosphere. During the SRB occurrence, some specific frequency radio wave could interfere with the Global Navigation Satellite System (GNSS) signals and therefore disturb the received signals. In this study, the low Earth orbit- (LEO-) based high-resolution GNSS radio occultation (RO) signals from multiple satellites (COSMIC, CHAMP, GRACE, SAC-C, Metop-A, and TerraSAR-X) processed in University Corporation for Atmospheric Research (UCAR) were first used to evaluate the effect of SRB on the RO technique. The radio solar telescope network (RSTN) observed radio flux was used to represent SRB occurrence. An extreme case during 6 December 2006 and statistical analysis during April 2006 to September 2012 were studied. The LEO RO signals show frequent loss of lock (LOL), simultaneous decrease on L1 and L2 signal-to-noise ratio (SNR) globally during daytime, small-scale perturbations of SNR, and decreased successful retrieval percentage (SRP) for both ionospheric and atmospheric occultations during SRB occurrence. A potential harmonic band interference was identified. Either decreased data volume or data quality will influence weather prediction, climate study, and space weather monitoring by using RO data during SRB time. Statistically, the SRP of ionospheric and atmospheric occultation retrieval shows ~4% and ~13% decrease, respectively, while the SNR of L1 and L2 show ~5.7% and ~11.7% decrease, respectively. A threshold value of ~1807 SFU of 1415 MHz frequency, which can result in observable GNSS SNR decrease, was derived based on our statistical analysis.

  5. 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.

  6. GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4

    Energy Technology Data Exchange (ETDEWEB)

    Pannella, M.; Elbaz, D.; Daddi, E.; Hwang, H. S.; Schreiber, C.; Strazzullo, V.; Aussel, H.; Bethermin, M.; Cibinel, A.; Juneau, S.; Floc’h, E. Le; Leiton, R. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu—CNRS—Université Paris Diderot, CEA-Saclay, F-91191 Gif-sur-Yvette (France); Dickinson, M. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Buat, V. [Aix-Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR7326, F-13388, Marseille (France); Charmandaris, V.; Magdis, G. [Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, 15236, Penteli (Greece); Ivison, R. J. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Borgne, D. Le [Institut d’Astrophysique de Paris, UMR 7095, CNRS, 98bis boulevard Arago, F-75005 Paris (France); Lin, L. [Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 106, Taiwan (China); Morrison, G. E. [Institute for Astronomy, University of Hawaii, Honolulu, Hawaii, HI-96822 (United States); and others

    2015-07-10

    We use deep panchromatic data sets in the GOODS-N field, from GALEX to the deepest Herschel far-infrared (FIR) and VLA radio continuum imaging, to explore the evolution of star-formation activity and dust attenuation properties of star-forming galaxies to z ≃ 4, using mass-complete samples. Our main results can be summarized as follows: (i) the slope of the star-formation rate–M{sub *} correlation is consistent with being constant ≃0.8 up to z ≃ 1.5, while its normalization keeps increasing with redshift; (ii) for the first time we are able to explore the FIR–radio correlation for a mass-selected sample of star-forming galaxies: the correlation does not evolve up to z ≃ 4; (iii) we confirm that galaxy stellar mass is a robust proxy for UV dust attenuation in star-forming galaxies, with more massive galaxies being more dust attenuated. Strikingly, we find that this attenuation relation evolves very weakly with redshift, with the amount of dust attenuation increasing by less than 0.3 mag over the redshift range [0.5–4] for a fixed stellar mass; (iv) the correlation between dust attenuation and the UV spectral slope evolves with redshift, with the median UV slope becoming bluer with redshift. By z ≃ 3, typical UV slopes are inconsistent, given the measured dust attenuations, with the predictions of commonly used empirical laws. (v) Finally, building on existing results, we show that gas reddening is marginally larger (by a factor of around 1.3) than the stellar reddening at all redshifts probed. Our results support a scenario where the ISM conditions of typical star-forming galaxies evolve with redshift, such that at z ≥ 1.5 Main Sequence galaxies have ISM conditions moving closer to those of local starbursts.

  7. Radio-quiet Gamma-ray Pulsars

    Directory of Open Access Journals (Sweden)

    Lupin Chun-Che Lin

    2016-09-01

    Full Text Available A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400 of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on are also to specified discuss their common and specific features.

  8. 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.

  9. ¿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.

  10. CONSTRAINING RADIO EMISSION FROM MAGNETARS

    Energy Technology Data Exchange (ETDEWEB)

    Lazarus, P.; Kaspi, V. M.; Dib, R. [Department of Physics, Rutherford Physics Building, McGill University, 3600 University Street, Montreal, Quebec H3A 2T8 (Canada); Champion, D. J. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Hessels, J. W. T., E-mail: plazar@physics.mcgill.ca [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands)

    2012-01-10

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U 0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected for any of our targets. The non-detections allow us to place luminosity upper limits of L{sub 1950} {approx}< 1.60 mJy kpc{sup 2} for periodic emission and L{sub 1950,single} {approx}< 7.6 Jy kpc{sup 2} for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.

  11. Affirmation of triggered Jovian radio emissions and their attribution to corotating radio lasers

    Science.gov (United States)

    Calvert, W.

    1985-01-01

    It is argued that the original statistical evidence for the existence of triggered radio emissions and corotating radio lasers on Jupiter remains valid notwithstanding the critique of Desch and Kaiser (1985). The Voyager radio spectrograms used to identify the triggered emissions are analyzed and the results are discussed. It is shown that the critique by Desch and Kaiser is unjustified because it is not based on the original event criteria, i.e., the correlation between the occurrence of Jovian auroral kilometric radiation and fast-drift type III solar bursts in the same frequency.

  12. The Hartebeeshoek Radio Astronomy Observatory

    International Nuclear Information System (INIS)

    Nicolson, G.D.

    1986-01-01

    This article briefly discusses the questions, problems and study fields of the modern astronomer. Radioastronomy has made important contributions to the study of the evolution of stars and has given much information on the birth of stars while at the other extreme, studies of neutron stars and the radio emission from the remnants of supernova explosions have given further insight into the death of individual stars. Radio astronomical studies have learned astronomers much about the structure of the Milky way and some twenty years ago, in a search for new radio galaxies, quasars were discovered. Radioastronomy research in South Africa is carried out at the Hartebeesthoek Radio Astronomy Observatory

  13. 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.)

  14. Evolvability Is an Evolved Ability: The Coding Concept as the Arch-Unit of Natural Selection.

    Science.gov (United States)

    Janković, Srdja; Ćirković, Milan M

    2016-03-01

    Physical processes that characterize living matter are qualitatively distinct in that they involve encoding and transfer of specific types of information. Such information plays an active part in the control of events that are ultimately linked to the capacity of the system to persist and multiply. This algorithmicity of life is a key prerequisite for its Darwinian evolution, driven by natural selection acting upon stochastically arising variations of the encoded information. The concept of evolvability attempts to define the total capacity of a system to evolve new encoded traits under appropriate conditions, i.e., the accessible section of total morphological space. Since this is dependent on previously evolved regulatory networks that govern information flow in the system, evolvability itself may be regarded as an evolved ability. The way information is physically written, read and modified in living cells (the "coding concept") has not changed substantially during the whole history of the Earth's biosphere. This biosphere, be it alone or one of many, is, accordingly, itself a product of natural selection, since the overall evolvability conferred by its coding concept (nucleic acids as information carriers with the "rulebook of meanings" provided by codons, as well as all the subsystems that regulate various conditional information-reading modes) certainly played a key role in enabling this biosphere to survive up to the present, through alterations of planetary conditions, including at least five catastrophic events linked to major mass extinctions. We submit that, whatever the actual prebiotic physical and chemical processes may have been on our home planet, or may, in principle, occur at some time and place in the Universe, a particular coding concept, with its respective potential to give rise to a biosphere, or class of biospheres, of a certain evolvability, may itself be regarded as a unit (indeed the arch-unit) of natural selection.

  15. A New Clue in the Mystery of Fast Radio Bursts

    Science.gov (United States)

    Kohler, Susanna

    2017-06-01

    .Bassa and collaborators also found that the properties of the host galaxy are consistent with those of a type of galaxy known as extreme emission line galaxies. This provides a tantalizing clue, as these galaxies are known to host both hydrogen-poor superluminous supernovae and long-duration gamma-ray bursts.Linking to the CauseWhat can this tell us about the cause of FRB 121102? The fact that this burst repeats already eliminates cataclysmic events as the origin. But the projected location of FRB 121102 within a star-forming region especially in a host galaxy thats similar to those typically hosting superluminous supernovae and long gamma-ray bursts strongly suggests theres a relation between these events.Artists impression of a gamma-ray burst in a star-forming region. [NASA/Swift/Mary Pat Hrybyk-Keith and John Jones]The authors propose that this observed coincidence, supported by models of magnetized neutron star birth, indicate an evolutionary link between fast radio bursts and neutron stars. In this picture, neutron stars or magnetars are born as long gamma-ray bursts or hydrogen-poor supernovae, and then evolve into fast-radio-burst-emitting sources.This picture may finally explain the cause of fast radio bursts but Bassa and collaborators caution that its also possible that this model applies only to FRB 121102. Since FRB 121102 is unique in being the only burst discovered to repeat, its cause may also be unique. The authors suggest that targeted searches of star-forming regions in galaxies similar to FRB 121102s host may reveal other repeating burst candidates, helping us to unravel the ongoing mystery of fast radio bursts.CitationC. G. Bassa et al 2017 ApJL 843 L8. doi:10.3847/2041-8213/aa7a0c

  16. 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)

  17. Natural selection promotes antigenic evolvability

    NARCIS (Netherlands)

    Graves, C.J.; Ros, V.I.D.; Stevenson, B.; Sniegowski, P.D.; Brisson, D.

    2013-01-01

    The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide

  18. 2nd Radio and Antenna Days of the Indian Ocean (RADIO 2014)

    Science.gov (United States)

    2014-10-01

    It was an honor and a great pleasure for all those involved in its organization to welcome the participants to the ''Radio and Antenna Days of the Indian Ocean'' (RADIO 2014) international conference that was held from 7th to 10th April 2014 at the Sugar Beach Resort, Wolmar, Flic-en-Flac, Mauritius. RADIO 2014 is the second of a series of conferences organized in the Indian Ocean region. The aim of the conference is to discuss recent developments, theories and practical applications covering the whole scope of radio-frequency engineering, including radio waves, antennas, propagation, and electromagnetic compatibility. The RADIO international conference emerged following discussions with engineers and scientists from the countries of the Indian Ocean as well as from other parts of the world and a need was felt for the organization of such an event in this region. Following numerous requests, the Island of Mauritius, worldwide known for its white sandy beaches and pleasant tropical atmosphere, was again chosen for the organization of the 2nd RADIO international conference. The conference was organized by the Radio Society, Mauritius and the Local Organizing Committee consisted of scientists from SUPELEC, France, the University of Mauritius, and the University of Technology, Mauritius. We would like to take the opportunity to thank all people, institutions and companies that made the event such a success. We are grateful to our gold sponsors CST and FEKO as well as URSI for their generous support which enabled us to partially support one PhD student and two scientists to attend the conference. We would also like to thank IEEE-APS and URSI for providing technical co-sponsorship. More than hundred and thirty abstracts were submitted to the conference. They were peer-reviewed by an international scientific committee and, based on the reviews, either accepted, eventually after revision, or rejected. RADIO 2014 brought together participants from twenty countries spanning

  19. Effectiveness of radio spokesperson's gender, vocal pitch and accent and the use of music in radio advertising

    Directory of Open Access Journals (Sweden)

    Josefa D. Martín-Santana

    2015-07-01

    Full Text Available The aim of this study is to analyze how certain voice features of radio spokespersons and background music influence the advertising effectiveness of a radio spot from the cognitive, affective and conative perspectives. We used a 2 × 2 × 2 × 2 experimental design in 16 different radio programs in which an ad hoc radio spot was inserted during advertising block. This ad changed according to combinations of spokesperson's gender (male–female, vocal pitch (low–high and accent (local–standard. In addition to these independent factors, the effect of background music in advertisements was also tested and compared with those that only had words. 987 regular radio listeners comprised the sample that was exposed to the radio program we created. Based on the differences in the levels of effectiveness in the tested voice features, our results suggest that the choice of the voice in radio advertising is one of the most important decisions an advertiser faces. Furthermore, the findings show that the inclusion of music does not always imply greater effectiveness.

  20. 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.

  1. 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

  2. Perkembangan dan Problematika Radio Komunitas di Indonesia

    Directory of Open Access Journals (Sweden)

    Masduki .

    2013-12-01

    Full Text Available Abstract: This article is about the development of community radio in Indonesia, it is problems and solutions. Community radio in Indonesia developed as an alternative to both public radio and commercial radio after the fall of Soeharto in 1998. Two important features of community radio are that it provides all community members with equal access to information, enhancing their rights and obligations, access to justice, public accountability and also enables them to participate actively in radio management and production. Both features enhance people’s selfawareness and sense of belonging to a community. The expansion of the progressive, participatory, community ownership, and non-profit model of community radio, has become a third sector of communication beside the commercial or state media. The dynamic development of community radio in Indonesia faced several problems starting from it is definition, implementation of regulation until standards of programmes operation based on the concept of community approach and participation

  3. 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.

  4. 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

  5. RADIO PROPERTIES OF THE BAT AGNs: THE FIR–RADIO RELATION, THE FUNDAMENTAL PLANE, AND THE MAIN SEQUENCE OF STAR FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Krista Lynne; Mushotzky, Richard F.; Vogel, Stuart; Shimizu, Thomas T. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Miller, Neal, E-mail: klsmith@astro.umd.edu [Department of Mathematics and Physics, Stevenson University, Stevenson, MD 21117 (United States)

    2016-12-01

    We conducted 22 GHz 1″ JVLA imaging of 70 radio-quiet active galactic nuclei (AGNs) from the Swift -BAT survey. We find radio cores in all but three objects. The radio morphologies of the sample fall into three groups: compact and core-dominated, extended, and jet-like. We spatially decompose each image into core flux and extended flux, and compare the extended radio emission with that predicted from previous Herschel observations using the canonical FIR–radio relation. After removing the AGN contribution to the FIR and radio flux densities, we find that the relation holds remarkably well despite the potentially different star formation physics in the circumnuclear environment. We also compare our core radio flux densities with predictions of coronal models and scale-invariant jet models for the origin of radio emission in radio-quiet AGNs, and find general consistency with both models. However, we find that the L {sub R}/ L {sub X} relation does not distinguish between star formation and non-relativistic AGN-driven outflows as the origin of radio emission in radio-quiet AGNs. Finally, we examine where objects with different radio morphologies fall in relation to the main sequence (MS) of star formation, and conclude that those AGNs that fall below the MS, as X-ray selected AGNs have been found to do, have core-dominated or jet-like 22 GHz morphologies.

  6. Division B Commission 40: Radio Astronomy

    NARCIS (Netherlands)

    Chapman, Jessica M.; Giovaninni, Gabriele; Taylor, Russell; Carilli, Christopher; Hills, Richard; Hirabayashi, Hisashi; Jonas, Justin L.; Lazio, Joseph; Morganti, Raffaella; Nan, Rendong; Rubio, Monica; Shastri, Prjaval; Kellermann, Ken; Ekers, Ronald; Ohishi, Masatoshi

    2016-01-01

    IAU Commission 40 for Radio Astronomy (hereafter C40) brought together scientists and engineers who carry out observational and theoretical research in radio astronomy and who develop and operate the ground and space-based radio astronomy facilities and instrumentation. As of June 2015, the

  7. Zero-Power Radio Device.

    Energy Technology Data Exchange (ETDEWEB)

    Brocato, Robert W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2018-02-01

    This report describes an unpowered radio receiver capable of detecting and responding to weak signals transmit ted from comparatively long distances . This radio receiver offers key advantages over a short range zero - power radio receiver previously described in SAND2004 - 4610, A Zero - Power Radio Receiver . The device described here can be fabricated as an integrated circuit for use in portable wireless devices, as a wake - up circuit, or a s a stand - alone receiver operating in conjunction with identification decoders or other electroni cs. It builds on key sub - components developed at Sandia National Laboratories over many years. It uses surface acoustic wave (SAW) filter technology. It uses custom component design to enable the efficient use of small aperture antennas. This device uses a key component, the pyroelectric demodulator , covered by Sandia owned U.S. Patent 7397301, Pyroelectric Demodulating Detector [1] . This device is also described in Sandia owned U.S. Patent 97266446, Zero Power Receiver [2].

  8. Disgust: Evolved function and structure

    NARCIS (Netherlands)

    Tybur, J.M.; Lieberman, D.; Kurzban, R.; DeScioli, P.

    2013-01-01

    Interest in and research on disgust has surged over the past few decades. The field, however, still lacks a coherent theoretical framework for understanding the evolved function or functions of disgust. Here we present such a framework, emphasizing 2 levels of analysis: that of evolved function and

  9. RADIO WITHOUT A LISTENER: "MAYAK"

    Directory of Open Access Journals (Sweden)

    Bysko Maxim V.

    2017-12-01

    Full Text Available The singularity of this article is that it is entirely based on a critical analysis of only one live musical radio program on the Mayak radio station and dedicated to the life and work of the famous British composer Andrew Lloyd Webber. In principle, the article can be considered a scientific review of the media product. Based on his analysis, the author comes to the paradoxical conclusion that the presence of a listener becomes unnecessary for modern broadcasting. This is stated by many principles of the conduct of the air, presented in the radio program, where all the information load is placed on the guest in the studio, where there is no preparatory work of the DJs, where their inability to navigate the genres of journalism violates communication norms and colloquial ethics, where an obvious deconstructive approach to the material offered for the listener. In addition, the phenomenon of being the DJs in the radio studio exclusively "for themselves" is emphasized by the sound design of the radio program, which runs counter to the logic of auditory perception (for example, the sequence of jingles, as well as the incompetent selection of musical material, which undoubtedly repels professional radio listeners-musicians.

  10. An overview and guide: planning instructional radio.

    Science.gov (United States)

    Imhoof, M

    1984-03-01

    Successful instructional radio projects require both comprehensive and complex planning. The instructional radio planning team needs to have knowledge and capabilities in several technical, social, and educational areas. Among other skills, the team must understand radio, curriculum design, the subject matter being taught, research and evaluation, and the environment in which the project operates. Once a basic approach to educational planning has been selected and broad educational goals set, radio may be selected as a cost effective means of achieving some of the goals. Assuming radio is a wise choice, there are still several factors which must be analyzed by a team member who is a radio specialist. The most obvious consideration is the inventory and evaluation of the facilities: studios; broadcast, recording, and transmission equipment; classroom radios; and so on. Capabilities of broadcast personnel are another consideration. Initial radio lessons need to teach the learners how to listen to the radio if they have no previous experience with institutional radio broadcasts. A captive, inschool audience ready to listen to radio instructions requires a different use of the medium than a noncaptive audience. With the noncaptive audience, the educational broadcaster must compete with entertaining choices from other media and popular activities and pastimes of the community. The most complex knowledge and analysis required in planning instructional radio concerns the relationship of the content to the medium. Environmental factors are important in planning educational programs. The physical environment may present several constraints on the learning experience and the use of radio. The most obvious is the effect of climate and terrain on the quality of radio reception. The physical environment is easily studied through experience in the target area, but this knowledge plays a significant role in designing effective learning materials for specific learners. Social

  11. Exploring Cognition Using Software Defined Radios for NASA Missions

    Science.gov (United States)

    Mortensen, Dale J.; Reinhart, Richard C.

    2016-01-01

    NASA missions typically operate using a communication infrastructure that requires significant schedule planning with limited flexibility when the needs of the mission change. Parameters such as modulation, coding scheme, frequency, and data rate are fixed for the life of the mission. This is due to antiquated hardware and software for both the space and ground assets and a very complex set of mission profiles. Automated techniques in place by commercial telecommunication companies are being explored by NASA to determine their usability by NASA to reduce cost and increase science return. Adding cognition the ability to learn from past decisions and adjust behavior is also being investigated. Software Defined Radios are an ideal way to implement cognitive concepts. Cognition can be considered in many different aspects of the communication system. Radio functions, such as frequency, modulation, data rate, coding and filters can be adjusted based on measurements of signal degradation. Data delivery mechanisms and route changes based on past successes and failures can be made to more efficiently deliver the data to the end user. Automated antenna pointing can be added to improve gain, coverage, or adjust the target. Scheduling improvements and automation to reduce the dependence on humans provide more flexible capabilities. The Cognitive Communications project, funded by the Space Communication and Navigation Program, is exploring these concepts and using the SCaN Testbed on board the International Space Station to implement them as they evolve. The SCaN Testbed contains three Software Defined Radios and a flight computer. These four computing platforms, along with a tracking antenna system and the supporting ground infrastructure, will be used to implement various concepts in a system similar to those used by missions. Multiple universities and SBIR companies are supporting this investigation. This paper will describe the cognitive system ideas under consideration and

  12. DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449

    International Nuclear Information System (INIS)

    Hunik, Dominika; Jamrozy, Marek

    2016-01-01

    We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed

  13. The Faint End of the Quasar Luminosity Function at z ~ 4: Implications for Ionization of the Intergalactic Medium and Cosmic Downsizing

    Science.gov (United States)

    Glikman, Eilat; Djorgovski, S. G.; Stern, Daniel; Dey, Arjun; Jannuzi, Buell T.; Lee, Kyoung-Soo

    2011-02-01

    We present an updated determination of the z ~ 4 QSO luminosity function (QLF), improving the quality of the determination of the faint end of the QLF presented by Glikman et al. (2010). We have observed an additional 43 candidates from our survey sample, yielding one additional QSO at z = 4.23 and increasing the completeness of our spectroscopic follow-up to 48% for candidates brighter than R = 24 over our survey area of 3.76 deg2. We study the effect of using K-corrections to compute the rest-frame absolute magnitude at 1450 Å compared with measuring M 1450 directly from the object spectra. We find a luminosity-dependent bias: template-based K-corrections overestimate the luminosity of low-luminosity QSOs, likely due to their reliance on templates derived from higher luminosity QSOs. Combining our sample with bright quasars from the Sloan Digital Sky Survey and using spectrum-based M 1450 for all the quasars, we fit a double power law to the binned QLF. Our best fit has a bright-end slope, α = 3.3 ± 0.2, and faint-end slope, β = 1.6+0.8 -0.6. Our new data revise the faint-end slope of the QLF down to flatter values similar to those measured at z ~ 3. The break luminosity, though poorly constrained, is at M* = -24.1+0.7 -1.9, approximately 1-1.5 mag fainter than at z ~ 3. This QLF implies that QSOs account for about half the radiation needed to ionize the intergalactic medium at these redshifts. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  14. How safe is tuning a radio?: using the radio tuning task as a benchmark for distracted driving.

    Science.gov (United States)

    Lee, Ja Young; Lee, John D; Bärgman, Jonas; Lee, Joonbum; Reimer, Bryan

    2018-01-01

    Drivers engage in non-driving tasks while driving, such as interactions entertainment systems. Studies have identified glance patterns related to such interactions, and manual radio tuning has been used as a reference task to set an upper bound on the acceptable demand of interactions. Consequently, some view the risk associated with radio tuning as defining the upper limit of glance measures associated with visual-manual in-vehicle activities. However, we have little knowledge about the actual degree of crash risk that radio tuning poses and, by extension, the risk of tasks that have similar glance patterns as the radio tuning task. In the current study, we use counterfactual simulation to take the glance patterns for manual radio tuning tasks from an on-road experiment and apply these patterns to lead-vehicle events observed in naturalistic driving studies. We then quantify how often the glance patterns from radio tuning are associated with rear-end crashes, compared to driving only situations. We used the pre-crash kinematics from 34 crash events from the SHRP2 naturalistic driving study to investigate the effect of radio tuning in crash-imminent situations, and we also investigated the effect of radio tuning on 2,475 routine braking events from the Safety Pilot project. The counterfactual simulation showed that off-road glances transform some near-crashes that could have been avoided into crashes, and glance patterns observed in on-road radio tuning experiment produced 2.85-5.00 times more crashes than baseline driving. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. 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

  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. 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.

  18. 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 ...

  19. 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....

  20. The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447 II. The Radio View

    Science.gov (United States)

    Schulz, R.; Kreikenbohm, A.; Kadler, M.; Ojha, R.; Ros, E.; Stevens, J.; Edwards, P. G.; Carpenter, B.; Elsaesser, D.; Gehrels, N.; hide

    2016-01-01

    Context. gamma-ray-detected radio-loud narrow-line Seyfert 1 (gamma-NLS1) galaxies constitute a small but interesting sample of the gamma-ray-loud AGN. The radio-loudest gamma-NLS1 known, PKS2004447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring programme TANAMI. Aims. We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS2004447, which are essential for understanding the diversity of the radio properties of gamma-NLS1s. Methods. The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active galaxies in the southern hemisphere. Lower resolution radio flux density measurements at multiple radio frequencies over four years of observations were obtained with the Australia Telescope Compact Array (ATCA). Results. The TANAMI VLBI image at 8.4GHz shows an extended one-sided jet with a dominant compact VLBI core. Its brightness temperature is consistent with equipartition, but it is an order of magnitude below other gamma-NLS1s with the sample value varying over two orders of magnitude. We find a compact morphology with a projected large-scale size 11 kpc and a persistent steep radio spectrum with moderate flux-density variability. Conclusions. PKS2004447 appears to be a unique member of the gamma-NLS1 sample. It exhibits blazar-like features, such as a flat featureless X-ray spectrum and a core-dominated, one-sided parsec-scale jet with indications for relativistic beaming. However, the data also reveal properties atypical for blazars, such as a radio spectrum and large-scale size consistent with compact-steep-spectrum (CSS) objects, which are usually associated with young radio sources. These characteristics are unique among all gamma-NLS1s and extremely rare among gamma-ray-loud AGN.

  1. 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.

  2. Propagation of Energetic Electrons from the Corona into Interplanetary Space and Type III Radio Emission. Planetary Radio Emissions| PLANETARY RADIO EMISSIONS VII 7|

    OpenAIRE

    Vocks, C.; Breitling, F.; Mann, G.

    2011-01-01

    During solar flares a large amount of electrons with energies greater than 20 keV is generated with a production rate of typically 1036 s-1. A part of them is able to propagate along open magnetic field lines through the corona into interplanetary space. During their travel they emit radio radiation which is observed as type III radio bursts in the frequency range from 100 MHz down to 10 kHz by the WAVES radio spectrometer aboard the spacecraft WIND, for instance. From the drift rates of thes...

  3. 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.

  4. Ionospheric Caustics in Solar Radio Observations

    Science.gov (United States)

    Koval, A.; Chen, Y.; Stanislavsky, A.

    2016-12-01

    The Earth ionosphere possesses by natural focusing and defocusing effects on radio waves due to presence of variable ionospheric irregularities which could act like convergent and divergent lenses on incident radiation. In particular, the focusing of emission from the Sun was firstly detected on the Nançay Decameter Array dynamic spectra in the 1980s. On time-frequency spectrograms the intensity variations form specific structures different from well-known solar radio bursts and clearly distinguishing on a background of solar radiation. Such structures have been identified as ionospheric caustics (ICs) and considered to be the result of radio waves refraction on medium scale travelling ionospheric disturbances (MSTIDs). Although nowadays the ICs are registered by different radio observatories due to augmentation of low-frequency radio telescopes, the most recent papers devoted to ICs in solar radio records date back to the 1980s. In this study, we revisit the ICs issue with some new results by conducting a statistical analysis of occurrence rate of ICs in solar dynamic spectra in meter-decameter wavelength range for long continuous period (15 years). The seasonal variations in ICs appearance have been found for the first time. Besides, we report the possible solar cycle dependence of ICs emergence. The radio waves propagation in the ionosphere comprising MSTIDs will be considered. The present research renews the subject of ICs in the low-frequency solar radio astronomy after about 35-year letup.

  5. The properties of radio ellipticals

    International Nuclear Information System (INIS)

    Sparks, W.B.; Disney, M.J.; Rodgers, A.W.

    1984-01-01

    Optical and additional radio data are presented for the bright galaxies of the Disney and Wall survey (1977 Mon. Not. R. Astron. Soc. 179, 235). These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas. (author)

  6. Radio and the Church – a Historical Glance

    Directory of Open Access Journals (Sweden)

    Carl-Mario Sultana

    2014-09-01

    Full Text Available Radio is a very powerful mass communication medium. In radio broadcasting, one can hear the echo of Christ’s words to his apostles in the missionary discourse: “You received without charge, give without charge...What you hear in whispers, proclaim from the house tops” (Mt 10,8b.27. Although the Church uses radio as a means to transmit the Good News of salvation, and we as human beings receive radio transmissions as a part of our daily life, we barely stop to think and reflect upon the underlying aspects of radio as a means of communication. In this paper, the Author endeavours to give a historical overview of what makes radio an important medium for evangelisation according to four key documents of the Church, while also studying the underlying theological positions found in these documents. These documents enable us to study radio as a broadcasting medium, highlighting the possible reactions of the Church to radio and how the Church changed its stance on radio over the years. The reason for focussing specifically on radio is for two particular reasons: from the very beginning, the Church has considered radio as a means for evangelising the masses. Notwithstanding this, what is going to be discussing in the paper can be equally applied to Television as a mass communication medium. Secondly, the Church took an active role in radio broadcasting by asking Guglielmo Marconi himself to construct the Vatican Radio in 1931. The documents of the Church also offer us a theology of radio as a mass communication medium, with unity, progress and evangelisation being the fundamental aspects. Church documents posit that not everything should be broadcasted over radio but only messages which bring about peace and unity.

  7. Grote Reber, Radio Astronomy Pioneer, Dies

    Science.gov (United States)

    2002-12-01

    Grote Reber, one of the earliest pioneers of radio astronomy, died in Tasmania on December 20, just two days shy of his 91st birthday. Reber was the first person to build a radio telescope dedicated to astronomy, opening up a whole new "window" on the Universe that eventually produced such landmark discoveries as quasars, pulsars and the remnant "afterglow" of the Big Bang. His self- financed experiments laid the foundation for today's advanced radio-astronomy facilities. Grote Reber Grote Reber NRAO/AUI photo "Radio astronomy has changed profoundly our understanding of the Universe and has earned the Nobel Prize for several major contributions. All radio astronomers who have followed him owe Grote Reber a deep debt for his pioneering work," said Dr. Fred Lo, director of the National Radio Astronomy Observatory (NRAO). "Reber was the first to systematically study the sky by observing something other than visible light. This gave astronomy a whole new view of the Universe. The continuing importance of new ways of looking at the Universe is emphasized by this year's Nobel Prizes in physics, which recognized scientists who pioneered X-ray and neutrino observations," Lo added. Reber was a radio engineer and avid amateur "ham" radio operator in Wheaton, Illinois, in the 1930s when he read about Karl Jansky's 1932 discovery of natural radio emissions coming from outer space. As an amateur operator, Reber had won awards and communicated with other amateurs around the world, and later wrote that he had concluded "there were no more worlds to conquer" in radio. Learning of Jansky's discovery gave Reber a whole new challenge that he attacked with vigor. Analyzing the problem as an engineer, Reber concluded that what he needed was a parabolic-dish antenna, something quite uncommon in the 1930s. In 1937, using his own funds, he constructed a 31.4-foot-diameter dish antenna in his back yard. The strange contraption attracted curious attention from his neighbors and became

  8. DIFFERENCES BETWEEN RADIO-LOUD AND RADIO-QUIET γ -RAY PULSARS AS REVEALED BY FERMI

    Energy Technology Data Exchange (ETDEWEB)

    Hui, C. Y.; Lee, Jongsu [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of); Takata, J. [Institute of Particle physics and Astronomy, Huazhong University of Science and Technology (China); Ng, C. W.; Cheng, K. S., E-mail: cyhui@cnu.ac.kr, E-mail: takata@hust.edu.cn [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong)

    2017-01-10

    By comparing the properties of non-recycled radio-loud γ -ray pulsars and radio-quiet γ -ray pulsars, we have searched for the differences between these two populations. We found that the γ -ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled γ -ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We note that this might result from an observational bias. By reexamining the previously reported difference of γ -ray-to-X-ray flux ratios, we found that the significance can be hampered by their statistical uncertainties. In the context of the outer gap model, we discuss the expected properties of these two populations and compare with the possible differences that are identified in our analysis.

  9. Radio systems engineering a tutorial approach

    CERN Document Server

    Santos, Héctor J De Los; Ponte, Juan

    2015-01-01

    This book is intended for readers who already have knowledge of devices and circuits for radio-frequency (RF) and microwave communication and are ready to study the systems engineering-level aspects of modern radio communications systems. The authors provide a general overview of radio systems with their components, focusing on the analog parts of the system and their non-idealities. Based on the physical functionality of the various building blocks of a modern radio system, block parameters are derived, which allows the examination of their influence on the overall system performance. The dis

  10. X-ray-bright optically faint active galactic nuclei in the Subaru Hyper Suprime-Cam wide survey

    Science.gov (United States)

    Terashima, Yuichi; Suganuma, Makoto; Akiyama, Masayuki; Greene, Jenny E.; Kawaguchi, Toshihiro; Iwasawa, Kazushi; Nagao, Tohru; Noda, Hirofumi; Toba, Yoshiki; Ueda, Yoshihiro; Yamashita, Takuji

    2018-01-01

    We construct a sample of X-ray-bright optically faint active galactic nuclei by combining Subaru Hyper Suprime-Cam, XMM-Newton, and infrared source catalogs. Fifty-three X-ray sources satisfying i-band magnitude fainter than 23.5 mag and X-ray counts with the EPIC-PN detector larger than 70 are selected from 9.1 deg2, and their spectral energy distributions (SEDs) and X-ray spectra are analyzed. Forty-four objects with an X-ray to i-band flux ratio FX/Fi > 10 are classified as extreme X-ray-to-optical flux sources. Spectral energy distributions of 48 among 53 are represented by templates of type 2 AGNs or star-forming galaxies and show the optical signature of stellar emission from host galaxies in the source rest frame. Infrared/optical SEDs indicate a significant contribution of emission from dust to the infrared fluxes, and that the central AGN is dust obscured. The photometric redshifts determined from the SEDs are in the range of 0.6-2.5. The X-ray spectra are fitted by an absorbed power-law model, and the intrinsic absorption column densities are modest (best-fit log NH = 20.5-23.5 cm-2 in most cases). The absorption-corrected X-ray luminosities are in the range of 6 × 1042-2 × 1045 erg s-1. Twenty objects are classified as type 2 quasars based on X-ray luminsosity and NH. The optical faintness is explained by a combination of redshifts (mostly z > 1.0), strong dust extinction, and in part a large ratio of dust/gas.

  11. The Spectrum Landscape: Prospects for Terrestrial Radio Astronomy

    Science.gov (United States)

    Liszt, Harvey Steven

    2018-01-01

    Radio astronomers work within broad constraints imposed by commercial and other non-astronomical uses of the radio spectrum, somewhat modified to accommodate astronomy’s particular needs through the provision of radio quiet zones, radio frequency allocations, coordination agreements and other devices of spectrum management. As radio astronomers increase the instantaneous bandwidth, frequency coverage and sensitivity of their instruments, these external constraints, and not the limitations of their own instruments, will increasingly be the greatest obstacles to radio astronomy’s ability to observe the cosmos from the surface of the Earth. Therefore, prospects for future radio astronomy operations are contingent on situational awareness and planning for the impact of non-astronomical uses of the radio frequency spectrum. New radio astronomy instruments will have to incorporate adaptive reactions to external developments, and radio astronomers should be encouraged to think in untraditional ways. Increased attention to spectrum management is one of these. In this talk I’ll recap some recent developments such as the proliferation of 76 – 81 GHz car radar and orbiting earth-mapping radars, either of which can burn out a radio astronomy receiver. I’ll summarize present trends for non-astronomical radio spectrum use that will be coming to fruition in the next decade or so, categorized into terrestrial fixed and mobile, airborne and space-borne uses, sub-divided by waveband from the cm to the sub-mm. I’ll discuss how they will impact terrestrial radio astronomy and the various ways in which radio astronomy should be prepared to react. Protective developments must occur both within radio astronomy’s own domain – designing, siting and constructing its instruments and mitigating unavoidable RFI – and facing outward toward the community of other spectrum users. Engagement with spectrum management is no panacea but it is an important means, and perhaps the only

  12. 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...

  13. La radio: aquellos primeros años

    Directory of Open Access Journals (Sweden)

    Luis Dávila Loor

    2015-01-01

    Full Text Available El autor reseña lo que fueron los primeros años de la radio, pues luego de inventado el telégrafo, el gramófono y el teléfono, estaban dados los ingredientes para inventar la radio. Las dos primeras décadas la radio fue utilizada para fines militares y marítimos. En los años 20 llegó a su máximo apogeo. Advino más tarde(1924 el radio teatro. La disonancia no lo desanimaba, Edison seguramente estaba convencido que un siglo después aparecerían los compac disks, en los que se escucharían con absoluta fidelidad las bulliciosas pero armoniosas canciones de un cantante negro con facha de mujer blanca. Con el desarrollo de la televisión vino el declive de la radio tradicional pero se inicio la etapa de la radio compañera que más tarde dio a lugar a la radio comunitaria.

  14. Introduction to international radio regulations

    Energy Technology Data Exchange (ETDEWEB)

    Struzak, R

    2003-12-15

    These notes introduce the ITU Radio Regulations and related UN and WTO agreements that specify how terrestrial and satellite radio should be used in all countries over the planet. Access to the existing information infrastructure, and to that of the future Information Society, depends critically on these regulations. The paper also discusses few problems related to the use of the radio frequencies and satellite orbits. The notes are extracted from a book under preparation, in which these issues are discussed in more detail. (author)

  15. Introduction to international radio regulations

    International Nuclear Information System (INIS)

    Struzak, R.

    2003-01-01

    These notes introduce the ITU Radio Regulations and related UN and WTO agreements that specify how terrestrial and satellite radio should be used in all countries over the planet. Access to the existing information infrastructure, and to that of the future Information Society, depends critically on these regulations. The paper also discusses few problems related to the use of the radio frequencies and satellite orbits. The notes are extracted from a book under preparation, in which these issues are discussed in more detail. (author)

  16. Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation

    Energy Technology Data Exchange (ETDEWEB)

    Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A

    2006-08-01

    We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.

  17. X-ray measurement of the spin-down of CalverA: A radio- and gamma-ray-quiet pulsar

    Energy Technology Data Exchange (ETDEWEB)

    Halpern, J. P.; Bogdanov, S.; Gotthelf, E. V., E-mail: jules@astro.columbia.edu [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027-6601 (United States)

    2013-12-01

    We measure spin-down of the 59 ms X-ray pulsar Calvera by comparing the XMM-Newton discovery data from 2009 with new Chandra timing observations taken in 2013. Its period derivative is P-dot =(3.19± 0.08)×10{sup −15}, which corresponds to spin-down luminosity E-dot =6.1×10{sup 35} erg s{sup –1}, characteristic age τ{sub c}≡P/2 P-dot =2.9×10{sup 5} yr, and surface dipole magnetic field strength B{sub s} = 4.4 × 10{sup 11} G. These values rule out a mildly recycled pulsar, but Calvera could be an orphaned central compact object (anti-magnetar), with a magnetic field that was initially buried by supernova debris and is now reemerging and approaching normal strength. We also performed unsuccessful searches for high-energy γ-rays from Calvera in both imaging and timing of >100 MeV Fermi photons. Even though the distance to Calvera is uncertain by an order of magnitude, an upper limit of d < 2 kpc inferred from X-ray spectra implies a γ-ray luminosity limit of <3.3 × 10{sup 32} erg s{sup –1}, which is less than that of any pulsar of comparable E-dot . Calvera shares some properties with PSR J1740+1000, a young radio pulsar that we show by virtue of its lack of proper motion was born outside of the Galactic disk. As an energetic, high-Galactic-latitude pulsar, Calvera is unique in being undetected in both radio and γ-rays to faint limits, which should place interesting constraints on models for particle acceleration and beam patterns in pulsar magnetospheres.

  18. Radio Flares from Gamma-ray Bursts

    Science.gov (United States)

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.

    2015-06-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1-1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

  19. RADIO FLARES FROM GAMMA-RAY BURSTS

    International Nuclear Information System (INIS)

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Gomboc, A.; Guidorzi, C.; Melandri, A.

    2015-01-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1–1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time

  20. An Improved Technique for the Photometry and Astrometry of Faint Companions

    Science.gov (United States)

    Burke, Daniel; Gladysz, Szymon; Roberts, Lewis; Devaney, Nicholas; Dainty, Chris

    2009-07-01

    We propose a new approach to differential astrometry and photometry of faint companions in adaptive optics images. It is based on a prewhitening matched filter, also referred to in the literature as the Hotelling observer. We focus on cases where the signal of the companion is located within the bright halo of the parent star. Using real adaptive optics data from the 3 m Shane telescope at the Lick Observatory, we compare the performance of the Hotelling algorithm with other estimation algorithms currently used for the same problem. The real single-star data are used to generate artificial binary objects with a range of magnitude ratios. In most cases, the Hotelling observer gives significantly lower astrometric and photometric errors. In the case of high Strehl ratio (SR) data (SR ≈ 0.5), the differential photometry of a binary star with a Δm = 4.5 and a separation of 0.6″ is better than 0.1 mag a factor of 2 lower than the other algorithms considered.

  1. Radio Astronomy at TIFR, some highlights and reminiscences

    Science.gov (United States)

    Swarup, G.

    Radio astronomy research was initiated at TIFR fifty years ago. In this historical article, I firstly trace my initiation in the field of radio astronomy during 1953-55 in the Radio Physics Laboratory of CSIRO in Australia and later during 1956-63 in USA. In September 1961, four radio astronomers working abroad wrote to a number of scientific organizations in India with their desire to start radio astronomy research in India. Soon thereafter Dr. Homi Bhabha, the founder Director of TIFR, approved the formation of a radio astronomy group therein. I joined TIFR in April 1963. During the last 50 years, TIFR has built two of the world's largest radio telescopes, namely the 530m long and 30 m wide parabolic cylinder equatorially mounted on a hill at Ooty in South India during 1960s and the Giant Metrewave Radio Telescope near Pune, consisting of 30 nos. of fully steerable parabolic dishes of 45 m diameters during 1990s. Fifty years of radio astronomy research at TIFR is briefly highlighted here.

  2. Community Radio in Political Theory and Development Practice

    African Journals Online (AJOL)

    zeleza

    These structural and conceptual elements provide community radio the ... characteristic problems of development projects based on its theoretical and structural .... and to fix basic radio equipment is a standard practice of community radio stations. ... community radio stations and participatory media organizations, but also ...

  3. A neighbourhood evolving network model

    International Nuclear Information System (INIS)

    Cao, Y.J.; Wang, G.Z.; Jiang, Q.Y.; Han, Z.X.

    2006-01-01

    Many social, technological, biological and economical systems are best described by evolved network models. In this short Letter, we propose and study a new evolving network model. The model is based on the new concept of neighbourhood connectivity, which exists in many physical complex networks. The statistical properties and dynamics of the proposed model is analytically studied and compared with those of Barabasi-Albert scale-free model. Numerical simulations indicate that this network model yields a transition between power-law and exponential scaling, while the Barabasi-Albert scale-free model is only one of its special (limiting) cases. Particularly, this model can be used to enhance the evolving mechanism of complex networks in the real world, such as some social networks development

  4. Two-way radios and scanners for dummies

    CERN Document Server

    Silver, H Ward

    2013-01-01

    Discover a fun new hobby with helpful possibilities Get directions, talk to folks overseas, or find out whether the fish are biting Want to check out the morning news in London, help out in emergencies, or tune in to the big race? Two-way radios open up a world of possibilities - literally. This handy guide tells you about the equipment you need, fills you in on radio etiquette, shows you how to stay legal, and gives you lots of cool ideas for family-friendly radio activities. Discover how to * Use the right radio lingo * Choose and operate different types of radios * Get a license if you n

  5. Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

    Science.gov (United States)

    Lähteenmäki, A.; Järvelä, E.; Ramakrishnan, V.; Tornikoski, M.; Tammi, J.; Vera, R. J. C.; Chamani, W.

    2018-06-01

    We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections. 37 GHz data are only available in electronic form 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/614/L1

  6. 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.

  7. Newnes radio and electronics engineer's pocket book

    CERN Document Server

    Moorshead, H W; Perry, J

    1978-01-01

    Newnes Radio and Electronics Engineer's Pocket Book, Fifteenth Edition provides reference of the information relevant in radio and electronics engineering. The book presents tables, illustrations, and diagrams of various data used in radio and electronics engineering. The coverage of the text includes abbreviations and symbols, electrical equations, and code conversions. The text will be useful to engineers, technicians, and other professionals who require a reference about the different aspects of radio and electronics.

  8. 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.)

  9. Communicating Science for Impact: Radio for Reaching Farmers ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Radio to share results The project will translate research results into simple radio campaign messages targeting small-scale farmers. Researchers will test ... The project will assess the effect of radio campaigns in influencing adoption decisions among listeners. Farm Radio ... Agent(e) responsable du CRDI. crmadm CRM ...

  10. 47 CFR 20.9 - Commercial mobile radio service.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Commercial mobile radio service. 20.9 Section... COMMERCIAL MOBILE RADIO SERVICES § 20.9 Commercial mobile radio service. (a) The following mobile services shall be treated as common carriage services and regulated as commercial mobile radio services...

  11. 47 CFR 2.107 - Radio astronomy station notification.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Radio astronomy station notification. 2.107....107 Radio astronomy station notification. (a) Pursuant to No. 1492 of Article 13 and Section F of Appendix 3 to the international Radio Regulations (Geneva, 1982), operators of radio astronomy stations...

  12. 49 CFR 220.23 - Publication of radio information.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Publication of radio information. 220.23 Section... § 220.23 Publication of radio information. Each railroad shall designate where radio base stations are.... The publication shall indicate the periods during which base and wayside radio stations are...

  13. 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

  14. Millisecond radio pulsars in globular clusters

    Science.gov (United States)

    Verbunt, Frank; Lewin, Walter H. G.; Van Paradijs, Jan

    1989-01-01

    It is shown that the number of millisecond radio pulsars, in globular clusters, should be larger than 100, applying the standard scenario that all the pulsars descend from low-mass X-ray binaries. Moreover, most of the pulsars are located in a small number of clusters. The prediction that Teran 5 and Liller 1 contain at least about a dozen millisecond radio pulsars each is made. The observations of millisecond radio pulsars in globular clusters to date, in particular the discovery of two millisecond radio pulsars in 47 Tuc, are in agreement with the standard scenario, in which the neutron star is spun up during the mass transfer phase.

  15. On the Critical Role of Divergent Selection in Evolvability

    Directory of Open Access Journals (Sweden)

    Joel Lehman

    2016-08-01

    Full Text Available An ambitious goal in evolutionary robotics is to evolve increasingly complex robotic behaviors with minimal human design effort. Reaching this goal requires evolutionary algorithms that can unlock from genetic encodings their latent potential for evolvability. One issue clouding this goal is conceptual confusion about evolvability, which often obscures the aspects of evolvability that are important or desirable. The danger from such confusion is that it may establish unrealistic goals for evolvability that prove unproductive in practice. An important issue separate from conceptual confusion is the common misalignment between selection and evolvability in evolutionary robotics. While more expressive encodings can represent higher-level adaptations (e.g. sexual reproduction or developmental systems that increase long-term evolutionary potential (i.e. evolvability, realizing such potential requires gradients of fitness and evolvability to align. In other words, selection is often a critical factor limiting increasing evolvability. Thus, drawing from a series of recent papers, this article seeks to both (1 clarify and focus the ways in which the term evolvability is used within artificial evolution, and (2 argue for the importance of one type of selection, i.e. divergent selection, for enabling evolvability. The main argument is that there is a fundamental connection between divergent selection and evolvability (on both the individual and population level that does not hold for typical goal-oriented selection. The conclusion is that selection pressure plays a critical role in realizing the potential for evolvability, and that divergent selection in particular provides a principled mechanism for encouraging evolvability in artificial evolution.

  16. Evolved H II regions

    International Nuclear Information System (INIS)

    Churchwell, E.

    1975-01-01

    A probable evolutionary sequence of H II regions based on six distinct types of observed objects is suggested. Two examples which may deviate from this idealized sequence, are discussed. Even though a size-mean density relation of H II regions can be used as a rough indication of whether a nebula is very young or evolved, it is argued that such a relation is not likely to be useful for the quantitative assignment of ages to H II regions. Evolved H II regions appear to fit into one of four structural types: rings, core-halos, smooth structures, and irregular or filamentary structures. Examples of each type are given with their derived physical parameters. The energy balance in these nebulae is considered. The mass of ionized gas in evolved H II regions is in general too large to trace the nebula back to single compact H II regions. Finally, the morphological type of the Galaxy is considered from its H II region content. 2 tables, 2 figs., 29 refs

  17. Exploring Community Radio Programming Practices to Inform ...

    African Journals Online (AJOL)

    A collective case study (multi-site) design was used to probe educational programming practices used in community radio. The paper explores how community radio station programming engages listeners in community generated education programmes that are produced through collaborative work with radio listener clubs.

  18. Politics and Radio in the 1924 Campaign.

    Science.gov (United States)

    Berkman, Dave

    1987-01-01

    Discusses the relation between radio broadcasting and politics in the 1924 presidential campaign, focusing on newspaper and magazine coverage. Notes radio's influence on candidate image, the aspect of censorship, and the use of radio during the campaign and after the election. (MM)

  19. An X-ray view of the very faint black hole X-ray transient Swift J1357.2-0933 during its 2011 outburst

    NARCIS (Netherlands)

    Armas Padilla, M.; Wijnands, R.; Altamirano, D.; Méndez, M.; Miller, J. M.; Degenaar, N.

    We report on the X-ray spectral (using XMM-Newton data) and timing behaviour [using XMM-Newton and Rossi X-ray Timing Explorer (RXTE) data] of the very faint X-ray transient and black hole system Swift J1357.2-0933 during its 2011 outburst. The XMM-Newton X-ray spectrum of this source can be

  20. 47 CFR 2.815 - External radio frequency power amplifiers.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false External radio frequency power amplifiers. 2... AND RADIO TREATY MATTERS; GENERAL RULES AND REGULATIONS Marketing of Radio-frequency Devices § 2.815 External radio frequency power amplifiers. (a) As used in this part, an external radio frequency power...

  1. Cognitive Radio RF: Overview and Challenges

    Directory of Open Access Journals (Sweden)

    Van Tam Nguyen

    2012-01-01

    Full Text Available Cognitive radio system (CRS is a radio system which is aware of its operational and geographical environment, established policies, and its internal state. It is able to dynamically and autonomously adapt its operational parameters and protocols and to learn from its previous experience. Based on software-defined radio (SDR, CRS provides additional flexibility and offers improved efficiency to overall spectrum use. CRS is a disruptive technology targeting very high spectral efficiency. This paper presents an overview and challenges of CRS with focus on radio frequency (RF section. We summarize the status of the related regulation and standardization activities which are very important for the success of any emerging technology. We point out some key research challenges, especially implementation challenges of cognitive radio (CR. A particular focus is on RF front-end, transceiver, and analog-to-digital and digital-to-analog interfaces which are still a key bottleneck in CRS development.

  2. Interferometry and synthesis in radio astronomy

    CERN Document Server

    Thompson, A Richard; Swenson Jr , George W

    2017-01-01

    This book is open access under a CC BY-NC 4.0 license. The third edition of this indispensable book in radio interferometry provides extensive updates to the second edition, including results and technical advances from the past decade; discussion of arrays that now span the full range of the radio part of the electromagnetic spectrum observable from the ground, 10 MHz to 1 THz; an analysis of factors that affect array speed; and an expanded discussion of digital signal-processing techniques and of scintillation phenomena and the effects of atmospheric water vapor on image distortion, among many other topics. With its comprehensiveness and detailed exposition of all aspects of the theory and practice of radio interferometry and synthesis imaging, this book has established itself as a standard reference in the field. It begins with an overview of the basic principles of radio astronomy, a short history of the development of radio interferometry, and an elementary discussion of the operation of an interferomete...

  3. Virtual observatory tools and amateur radio observations supporting scientific analysis of Jupiter radio emissions

    Science.gov (United States)

    Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Savalle, Renaud; Stéphane, Erard; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Génot, Vincent; Thieman, Jim; Typinski, Dave; Sky, Jim; Higgins, Chuck; Imai, Masafumi

    2016-04-01

    In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  4. 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.)

  5. 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.

  6. Lyman continuum escape fraction of faint galaxies at z 3.3 in the CANDELS/GOODS-North, EGS, and COSMOS fields with LBC

    Science.gov (United States)

    Grazian, A.; Giallongo, E.; Paris, D.; Boutsia, K.; Dickinson, M.; Santini, P.; Windhorst, R. A.; Jansen, R. A.; Cohen, S. H.; Ashcraft, T. A.; Scarlata, C.; Rutkowski, M. J.; Vanzella, E.; Cusano, F.; Cristiani, S.; Giavalisco, M.; Ferguson, H. C.; Koekemoer, A.; Grogin, N. A.; Castellano, M.; Fiore, F.; Fontana, A.; Marchi, F.; Pedichini, F.; Pentericci, L.; Amorín, R.; Barro, G.; Bonchi, A.; Bongiorno, A.; Faber, S. M.; Fumana, M.; Galametz, A.; Guaita, L.; Kocevski, D. D.; Merlin, E.; Nonino, M.; O'Connell, R. W.; Pilo, S.; Ryan, R. E.; Sani, E.; Speziali, R.; Testa, V.; Weiner, B.; Yan, H.

    2017-06-01

    Context. The reionization of the Universe is one of the most important topics of present-day astrophysical research. The most plausible candidates for the reionization process are star-forming galaxies, which according to the predictions of the majority of the theoretical and semi-analytical models should dominate the H I ionizing background at z ≳ 3. Aims: We measure the Lyman continuum escape fraction, which is one of the key parameters used to compute the contribution of star-forming galaxies to the UV background. It provides the ratio between the photons produced at λ ≤ 912 Å rest-frame and those that are able to reach the inter-galactic medium, I.e. that are not absorbed by the neutral hydrogen or by the dust of the galaxy's inter-stellar medium. Methods: We used ultra-deep U-band imaging (U = 30.2 mag at 1σ) from Large Binocular Camera at the Large Binocular Telescope (LBC/LBT) in the CANDELS/GOODS-North field and deep imaging in the COSMOS and EGS fields in order to estimate the Lyman continuum escape fraction of 69 star-forming galaxies with secure spectroscopic redshifts at 3.27 ≤ z ≤ 3.40 to faint magnitude limits (L = 0.2L∗, or equivalently M1500 - 19). The narrow redshift range implies that the LBC U-band filter exclusively samples the λ ≤ 912 Å rest-frame wavelengths. Results: We measured through stacks a stringent upper limit (L∗), while for the faint population (L = 0.2L∗) the limit to the escape fraction is ≲ 10%. We computed the contribution of star-forming galaxies to the observed UV background at z 3 and find that it is not sufficient to keep the Universe ionized at these redshifts unless their escape fraction increases significantly (≥ 10%) at low luminosities (M1500 ≥ - 19). Conclusions: We compare our results on the Lyman continuum escape fraction of high-z galaxies with recent estimates in the literature, and discuss future prospects to shed light on the end of the Dark Ages. In the future, strong gravitational

  7. 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.

  8. The collective radio properties of symbiotic stars

    International Nuclear Information System (INIS)

    Seaquist, E.R.; Taylor, A.R.

    1990-01-01

    Radio measurements of symbiotic stars are reported which extend the search for radio emission and provide multifrequency and multiepoch measurements of previously detected stars. The results show no evidence that there are time variations in excess of about 30 percent over a period of several years in the detected stars. The radio flux densities are correlated with brightness in the IR, especially at the longer IR wavelengths where dust emission dominates. It is confirmed that symbiotics with the latest red giant spectral types are the most luminous radio emitters. The D-types are the most radio-luminous. Virtually all detected stars with measurements at more than one frequency exhibit a positive spectral index, consistent with optically thick thermal bremsstrahlung. The binary separation for a number of radio-emitting symbiotics is estimated, and it is found that the distribution of inferred binary separations is dramatically different for IR D-types than for S-types. 37 refs

  9. 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.

  10. 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

  11. A COTS RF Optical Software Defined Radio for the Integrated Radio and Optical Communications Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Zeleznikar, Daniel J.; Wroblewski, Adam C.; Tokars, Roger P.; Schoenholz, Bryan L.; Lantz, Nicholas C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration (NASA) is investigating the merits of a hybrid radio frequency (RF) and optical communication system for deep space missions. In an effort to demonstrate the feasibility and advantages of a hybrid RFOptical software defined radio (SDR), a laboratory prototype was assembled from primarily commercial-off-the-shelf (COTS) hardware components. This COTS platform has been used to demonstrate simultaneous transmission of the radio and optical communications waveforms through to the physical layer (telescope and antenna). This paper details the hardware and software used in the platform and various measures of its performance. A laboratory optical receiver platform has also been assembled in order to demonstrate hybrid free space links in combination with the transmitter.

  12. A COTS RF/Optical Software Defined Radio for the Integrated Radio and Optical Communications Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Zeleznikar, Daniel J.; Wroblewski, Adam C.; Tokars, Roger P.; Schoenholz, Bryan L.; Lantz, Nicholas C.

    2017-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration (NASA) is investigating the merits of a hybrid radio frequency (RF) and optical communication system for deep space missions. In an effort to demonstrate the feasibility and advantages of a hybrid RF/Optical software defined radio (SDR), a laboratory prototype was assembled from primarily commercial-off-the-shelf (COTS) hardware components. This COTS platform has been used to demonstrate simultaneous transmission of the radio and optical communications waveforms through to the physical layer (telescope and antenna). This paper details the hardware and software used in the platform and various measures of its performance. A laboratory optical receiver platform has also been assembled in order to demonstrate hybrid free space links in combination with the transmitter.

  13. Meteor trajectory estimation from radio meteor observations

    Science.gov (United States)

    Kákona, J.

    2016-01-01

    Radio meteor observation techniques are generally accepted as meteor counting methods useful mainly for meteor flux detection. Due to the technical progress in radio engineering and electronics a construction of a radio meteor detection network with software defined receivers has become possible. These receivers could be precisely time synchronized and could obtain data which provide us with more information than just the meteor count. We present a technique which is able to compute a meteor trajectory from the data recorded by multiple radio stations.

  14. THE SPITZER HIGH-REDSHIFT RADIO GALAXY SURVEY

    International Nuclear Information System (INIS)

    De Breuck, Carlos; Galametz, Audrey; Vernet, Joel; Seymour, Nick; Stern, Daniel; Eisenhardt, P. R. M.; Willner, S. P.; Fazio, G. G.; Lacy, Mark; Rettura, Alessandro; Rocca-Volmerange, Brigitte

    2010-01-01

    We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 1 3 μ m /S 1.6 μ m versus S 5 μ m /S 3 μ m criterion, we identify 42 sources where the rest-frame 1.6 μm emission from the stellar population can be measured. For these radio galaxies, the median stellar mass is high, 2 x 10 11 M sun , and remarkably constant within the range 1 3, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z ∼ 3, but confirmation by more detailed decomposition of stellar and active galactic nucleus (AGN) emission is needed. The rest-frame 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the rest-frame 5 μm hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance-an indicator of jet orientation-is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6'') companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers.

  15. SUPERNOVA 2003ie WAS LIKELY A FAINT TYPE IIP EVENT

    Energy Technology Data Exchange (ETDEWEB)

    Arcavi, Iair; Gal-Yam, Avishay [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); Sergeev, Sergey G., E-mail: iair.arcavi@weizmann.ac.il [Crimean Astrophysical Observatory, P/O Nauchny, Crimea 98409 (Ukraine)

    2013-04-15

    We present new photometric observations of supernova (SN) 2003ie starting one month before discovery, obtained serendipitously while observing its host galaxy. With only a weak upper limit derived on the mass of its progenitor (<25 M{sub Sun }) from previous pre-explosion studies, this event could be a potential exception to the ''red supergiant (RSG) problem'' (the lack of high-mass RSGs exploding as Type IIP SNe). However, this is true only if SN2003ie was a Type IIP event, something which has never been determined. Using recently derived core-collapse SN light-curve templates, as well as by comparison to other known SNe, we find that SN2003ie was indeed a likely Type IIP event. However, with a plateau magnitude of {approx} - 15.5 mag, it is found to be a member of the faint Type IIP class. Previous members of this class have been shown to arise from relatively low-mass progenitors (<12 M{sub Sun }). It therefore seems unlikely that this SN had a massive RSG progenitor. The use of core-collapse SN light-curve templates is shown to be helpful in classifying SNe with sparse coverage. These templates are likely to become more robust as large homogeneous samples of core-collapse events are collected.

  16. 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.)

  17. Radio as the Voice of God: Peace and Tolerance Radio Programming’s Impact on Norms

    Directory of Open Access Journals (Sweden)

    Daniel P. Aldrich

    2012-12-01

    Full Text Available Observers have argued that radio programming can alter norms, especially through hate radio designed to increase animosity between groups. This article tests whether or not radio programming under the Countering Violent Extremism (CVE policy framework can reduce potential conflict and increase civic engagement and positive views of foreign nations. Data from surveys of more than 1,000 respondents in Mali, Chad, and Niger illuminate the ways in which peace and tolerance programming changed perspectives and altered behavior in statistically significant ways. Results show that individuals exposed to multi-level U.S. government programming were more likely to listen to peace and tolerance radio. Further, bivariate, multivariate regression, and propensity score matching techniques show that individuals who listened more regularly to such programs participated more frequently in civic activities and supported working with the West to combat terrorism (holding constant a number of potential confounding economic, demographic, and attitudinal factors. However, higher levels of radio listening had no measurable impact on opposition to the use of violence in the name of Islam or opposition to the imposition of Islamic law. Further, data indicate that women and men have responded to programming in measurably different ways. These mixed results have important implications for current and future “soft-side” programs for countering violent extremism.

  18. TOWARD A NETWORK OF FAINT DA WHITE DWARFS AS HIGH-PRECISION SPECTROPHOTOMETRIC STANDARDS

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, G.; Matheson, T.; Saha, A.; Claver, J. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Axelrod, T.; Olszewski, E. [University of Arizona, Steward Observatory, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Holberg, J. B. [University of Arizona, Lunar and Planetary Laboratory, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Stubbs, C. W. [Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States); Bohlin, R. C.; Deustua, S.; Rest, A., E-mail: gnarayan@noao.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2016-05-10

    We present the initial results from a program aimed at establishing a network of hot DA white dwarfs to serve as spectrophotometric standards for present and future wide-field surveys. These stars span the equatorial zone and are faint enough to be conveniently observed throughout the year with large-aperture telescopes. The spectra of these white dwarfs are analyzed in order to generate a non-local-thermodynamic-equilibrium model atmosphere normalized to Hubble Space Telescope colors, including adjustments for wavelength-dependent interstellar extinction. Once established, this standard star network will serve ground-based observatories in both hemispheres as well as space-based instrumentation from the UV to the near IR. We demonstrate the effectiveness of this concept and show how two different approaches to the problem using somewhat different assumptions produce equivalent results. We discuss the lessons learned and the resulting corrective actions applied to our program.

  19. Hardware Interface Description for the Integrated Power, Avionics, and Software (iPAS) Space Telecommunications Radio Ssystem (STRS) Radio

    Science.gov (United States)

    Shalkhauser, Mary Jo W.; Roche, Rigoberto

    2017-01-01

    The Space Telecommunications Radio System (STRS) provides a common, consistent framework for software defined radios (SDRs) to abstract the application software from the radio platform hardware. The STRS standard aims to reduce the cost and risk of using complex, configurable and reprogrammable radio systems across NASA missions. To promote the use of the STRS architecture for future NASA advanced exploration missions, NASA Glenn Research Center (GRC) developed an STRS-compliant SDR on a radio platform used by the Advance Exploration System program at the Johnson Space Center (JSC) in their Integrated Power, Avionics, and Software (iPAS) laboratory. The iPAS STRS Radio was implemented on the Reconfigurable, Intelligently-Adaptive Communication System (RIACS) platform, currently being used for radio development at JSC. The platform consists of a Xilinx ML605 Virtex-6 FPGA board, an Analog Devices FMCOMMS1-EBZ RF transceiver board, and an Embedded PC (Axiomtek eBox 620-110-FL) running the Ubuntu 12.4 operating system. Figure 1 shows the RIACS platform hardware. The result of this development is a very low cost STRS compliant platform that can be used for waveform developments for multiple applications.The purpose of this document is to describe how to develop a new waveform using the RIACS platform and the Very High Speed Integrated Circuits (VHSIC) Hardware Description Language (VHDL) FPGA wrapper code and the STRS implementation on the Axiomtek processor.

  20. Waveform Developer's Guide for the Integrated Power, Avionics, and Software (iPAS) Space Telecommunications Radio System (STRS) Radio

    Science.gov (United States)

    Shalkhauser, Mary Jo W.; Roche, Rigoberto

    2017-01-01

    The Space Telecommunications Radio System (STRS) provides a common, consistent framework for software defined radios (SDRs) to abstract the application software from the radio platform hardware. The STRS standard aims to reduce the cost and risk of using complex, configurable and reprogrammable radio systems across NASA missions. To promote the use of the STRS architecture for future NASA advanced exploration missions, NASA Glenn Research Center (GRC) developed an STRS-compliant SDR on a radio platform used by the Advance Exploration System program at the Johnson Space Center (JSC) in their Integrated Power, Avionics, and Software (iPAS) laboratory. The iPAS STRS Radio was implemented on the Reconfigurable, Intelligently-Adaptive Communication System (RIACS) platform, currently being used for radio development at JSC. The platform consists of a Xilinx(Trademark) ML605 Virtex(Trademark)-6 FPGA board, an Analog Devices FMCOMMS1-EBZ RF transceiver board, and an Embedded PC (Axiomtek(Trademark) eBox 620-110-FL) running the Ubuntu 12.4 operating system. The result of this development is a very low cost STRS compliant platform that can be used for waveform developments for multiple applications. The purpose of this document is to describe how to develop a new waveform using the RIACS platform and the Very High Speed Integrated Circuits (VHSIC) Hardware Description Language (VHDL) FPGA wrapper code and the STRS implementation on the Axiomtek processor.

  1. Tuning in to pavement radio

    NARCIS (Netherlands)

    Ellis, S.

    1989-01-01

    This article describes a phenomenon known all over Africa, for which there is no really satisfactory term in English but which is summed up in the French term 'radio trottoir', literally 'pavement radio'. It may be defined as the popular and unofficial discussion of current affairs in Africa,

  2. Miniature EVA Software Defined Radio

    Science.gov (United States)

    Pozhidaev, Aleksey

    2012-01-01

    As NASA embarks upon developing the Next-Generation Extra Vehicular Activity (EVA) Radio for deep space exploration, the demands on EVA battery life will substantially increase. The number of modes and frequency bands required will continue to grow in order to enable efficient and complex multi-mode operations including communications, navigation, and tracking applications. Whether conducting astronaut excursions, communicating to soldiers, or first responders responding to emergency hazards, NASA has developed an innovative, affordable, miniaturized, power-efficient software defined radio that offers unprecedented power-efficient flexibility. This lightweight, programmable, S-band, multi-service, frequency- agile EVA software defined radio (SDR) supports data, telemetry, voice, and both standard and high-definition video. Features include a modular design, an easily scalable architecture, and the EVA SDR allows for both stationary and mobile battery powered handheld operations. Currently, the radio is equipped with an S-band RF section. However, its scalable architecture can accommodate multiple RF sections simultaneously to cover multiple frequency bands. The EVA SDR also supports multiple network protocols. It currently implements a Hybrid Mesh Network based on the 802.11s open standard protocol. The radio targets RF channel data rates up to 20 Mbps and can be equipped with a real-time operating system (RTOS) that can be switched off for power-aware applications. The EVA SDR's modular design permits implementation of the same hardware at all Network Nodes concept. This approach assures the portability of the same software into any radio in the system. It also brings several benefits to the entire system including reducing system maintenance, system complexity, and development cost.

  3. Radio emission of the sun and planets

    CERN Document Server

    Zheleznyakov, V V

    1970-01-01

    International Series of Monographs in Natural Philosophy, Volume 25: Radio Emission of the Sun and Planets presents the origin of the radio emission of the planets. This book examines the outstanding triumphs achieved by radio astronomy of the solar system. Comprised of 10 chapters, this volume begins with an overview of the physical conditions in the upper layers of the Sun, the Moon, and the planets. This text then examines the three characteristics of radio emission, namely, the frequency spectrum, the polarization, and the angular spectrum. Other chapters consider the measurements of the i

  4. Radio protocols for LTE and LTE-advanced

    CERN Document Server

    Yi, SeungJune; Lee, YoungDae; Park, SungJun; Jung, SungHoon

    2012-01-01

    Provides a unique focus on radio protocols for LTE and LTE-Advanced (LTE-A) Giving readers a valuable understanding of LTE radio protocols, this book covers LTE (Long-Term Evolution) Layer 2/3 radio protocols as well as new features including LTE-Advanced. It is divided into two sections to differentiate between the two technologies' characteristics. The authors systematically explain the design principles and functions of LTE radio protocols during the development of mobile handsets. The book also provides essential knowledge on the interaction between mobile networks a

  5. ¿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...

  6. A Fast Radio Burst Host Galaxy

    OpenAIRE

    Keane, E. F.; Johnston, S.; Bhandari, S.; Barr, E.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Flynn, C.; Jameson, A.; Kramer, M.; Petroff, E.; Possenti, A.; van Straten, W.; Bailes, M.; Burke-Spolaor, S.

    2016-01-01

    In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in...

  7. Uticaj transportnih protokola na efikasnost namenskih radio-komunikacija

    Directory of Open Access Journals (Sweden)

    Ljubiša S. Nedeljković

    2014-04-01

    Full Text Available Savremene namenske radio-komunikacije zasnivaju se na internet protokolu. Efikasnost namenskih radio-komunikacija zavisi od propusnosti. Na propusnost namenskih radio-komunikacija utiču i transportni protokoli. U radu je analizirana propusnost transportnih protokola TCP (Transport Control Protocol i UDP (User Datagram Protocol u VF (visoko frekvencijskim i VVF (vrlo visoko- frekvencijskim namenskim radio-komunikacijama sa očekivanim vremenima kašnjenja i verovatnoćom greške po paketu podataka. Ocenjena je mogućnost njihove primene u namenskim radio-komunikacijama. Pri tome je uzet u obzir uticaj sledećih faktora: vreme povratnog puta, veličina paketa podataka, veličina prozora i verovatnoća greške po paketu podataka. Transportni protokol sa većom propusnošću pogodniji je za primenu u namenskim radio-komunikacijama. Veća propusnost transportnih protokola znači da je veća i propusnost namenskih radio-komunikacija. 

  8. Radio pulsar glitches as a state-dependent Poisson process

    Science.gov (United States)

    Fulgenzi, W.; Melatos, A.; Hughes, B. D.

    2017-10-01

    Gross-Pitaevskii simulations of vortex avalanches in a neutron star superfluid are limited computationally to ≲102 vortices and ≲102 avalanches, making it hard to study the long-term statistics of radio pulsar glitches in realistically sized systems. Here, an idealized, mean-field model of the observed Gross-Pitaevskii dynamics is presented, in which vortex unpinning is approximated as a state-dependent, compound Poisson process in a single random variable, the spatially averaged crust-superfluid lag. Both the lag-dependent Poisson rate and the conditional distribution of avalanche-driven lag decrements are inputs into the model, which is solved numerically (via Monte Carlo simulations) and analytically (via a master equation). The output statistics are controlled by two dimensionless free parameters: α, the glitch rate at a reference lag, multiplied by the critical lag for unpinning, divided by the spin-down rate; and β, the minimum fraction of the lag that can be restored by a glitch. The system evolves naturally to a self-regulated stationary state, whose properties are determined by α/αc(β), where αc(β) ≈ β-1/2 is a transition value. In the regime α ≳ αc(β), one recovers qualitatively the power-law size and exponential waiting-time distributions observed in many radio pulsars and Gross-Pitaevskii simulations. For α ≪ αc(β), the size and waiting-time distributions are both power-law-like, and a correlation emerges between size and waiting time until the next glitch, contrary to what is observed in most pulsars. Comparisons with astrophysical data are restricted by the small sample sizes available at present, with ≤35 events observed per pulsar.

  9. Shoestring Budget Radio Astronomy (Abstract)

    Science.gov (United States)

    Hoot, J. E.

    2017-12-01

    (Abstract only) The commercial exploitation of microwave frequencies for cellular, WiFi, Bluetooth, HDTV, and satellite digital media transmission has brought down the cost of the components required to build an effective radio telescope to the point where, for the cost of a good eyepiece, you can construct and operate a radio telescope. This paper sets forth a family of designs for 1421 MHz telescopes. It also proposes a method by which operators of such instruments can aggregate and archive data via the Internet. With 90 or so instruments it will be possible to survey the entire radio sky for transients with a 24 hour cadence.

  10. Evolving Technologies: A View to Tomorrow

    Science.gov (United States)

    Tamarkin, Molly; Rodrigo, Shelley

    2011-01-01

    Technology leaders must participate in strategy creation as well as operational delivery within higher education institutions. The future of higher education--the view to tomorrow--is irrevocably integrated and intertwined with evolving technologies. This article focuses on two specific evolving technologies: (1) alternative IT sourcing; and (2)…

  11. 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.

  12. 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

  13. 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

  14. Radio science investigations with Voyager

    International Nuclear Information System (INIS)

    Eshleman, V.R.; Tyler, G.L.; Croft, T.A.

    1977-01-01

    The planned radio science investigations during the Voyager missions to the outer planets involve: (1) the use of the radio links to and from the spacecraft for occultation measurements of planetary and satellite atmospheres and ionospheres, the rings of Saturn, the solar corona, and the general-relativistic time delay for radiowave propagation through the Sun's gravity field; (2) radio link measurements of true or apparent spacecraft motion caused by the gravity fields of the planets, the masses of their larger satellites, and characteristics of the interplanetary medium; and (3) related measurements which could provide results in other areas, including the possible detection of long-wavelength gravitational radiation propagating through the Solar System. The measurements will be used to study: atmospheric and ionospheric structure, constituents, and dynamics; the sizes, radial distribution, total mass, and other characteristics of the particles in the rings of Saturn; interior models for the major planets and the mean density and bulk composition of a number of their satellites; the plasma density and dynamics of the solar corona and interplanetary medium; and certain fundamental questions involving gravitation and relativity. The instrumentation for these experiments is the same ground-based and spacecraft radio systems as will be used for tracking and communicating with the Voyager spacecraft, although several important features of these systems have been provided primarily for the radio science investigations. (Auth.)

  15. Strategi Reputation Marketing untuk Mendapatkan Awareness Khalayak Radio (Studi Kasus: 97.5 Fm Motion Radio Jakarta

    Directory of Open Access Journals (Sweden)

    Anathasia Citra

    2013-04-01

    Full Text Available The research aims to know the implication of reputation marketing strategy in Broadcast Media Management, how the Reputation Marketing impacts the improvement of Audience awareness. This is a descriptive research using qualitative approach with the methodology of observant participatory. The result is that Reputation Marketing is essential to be conducted specially in new radio station to get attention of audiences. As the result, its increasing the awareness of the radio station and benefit for the radio station is because the increase of the numbers of advertisers.  

  16. Radio-controlled automatic gas meter-reading system; Releve automatique de compteur par radio

    Energy Technology Data Exchange (ETDEWEB)

    Yasui, M. [Osaka Gas Co., Ltd (Japan); Ishikawa, K.; Fujiwara, J. [Tokyo Gas Co., Ltd. (Japan); Ichihashi, T. [Toho Gas Co., Ltd. (Japan)

    2000-07-01

    In Japan, an automatic gas meter-reading system is in operation, also incorporating the functions of monitoring for abnormalities in gas use and remote-controlled emergency gas supply shutoff. This system has been realized by linking microcomputer-controlled gas meters(It's called 'Intelligent gas mater') equipped with automatic shutoff mechanism to the gas utility company operation center via communication lines. While the present system uses cable communication lines, we of Tokyo Gas Co., Ltd., Osaka Gas Co., Ltd. and Toho Gas Co., Ltd., have jointly developed a new system based on radio communication. This paper introduces this new system. While radio-controlled meter-reading systems are used in many countries around the world solely for automatic meter reading, our recently developed system is also capable of monitoring for abnormalities in gas use and remote-controlled emergency gas supply shutoff, thanks to its almost real-time two-way communication function. The new system can serve for a period of ten years without recharging. It is also characterized by its applicability as different systems according to purposes: 1) conventional automatic meter-reading system (terminal network control unit or T-NCU), 2) large-scale radio-controlled meter-reading system, and 3) portable terminal-type radio-controlled meter-reading system. (authors)

  17. 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

  18. Spacetimes containing slowly evolving horizons

    International Nuclear Information System (INIS)

    Kavanagh, William; Booth, Ivan

    2006-01-01

    Slowly evolving horizons are trapping horizons that are ''almost'' isolated horizons. This paper reviews their definition and discusses several spacetimes containing such structures. These include certain Vaidya and Tolman-Bondi solutions as well as (perturbatively) tidally distorted black holes. Taking into account the mass scales and orders of magnitude that arise in these calculations, we conjecture that slowly evolving horizons are the norm rather than the exception in astrophysical processes that involve stellar-scale black holes

  19. STAR FORMATION IN ULTRA-FAINT DWARFS: CONTINUOUS OR SINGLE-AGE BURSTS?

    International Nuclear Information System (INIS)

    Webster, David; Bland-Hawthorn, Joss; Sutherland, Ralph

    2015-01-01

    We model the chemical evolution of six ultra-faint dwarfs (UFDs): Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I based on their recently determined star formation histories. We show that two single-age bursts cannot explain the observed [α/Fe] versus [Fe/H] distribution in these galaxies and that some self-enrichment is required within the first burst. An alternative scenario is modeled, in which star formation is continuous except for short interruptions when one or more supernovae temporarily blow the dense gas out from the center of the system. This model allows for self-enrichment and can reproduce the chemical abundances of the UFDs in which the second burst is only a trace population. We conclude that the most likely star formation history is one or two extended periods of star formation, with the first burst lasting for at least 100 Myr. As found in earlier work, the observed properties of UFDs can be explained by formation at a low mass (M vir ∼10 7 M ⊙ ), rather than being stripped remnants of much larger systems

  20. STAR FORMATION IN ULTRA-FAINT DWARFS: CONTINUOUS OR SINGLE-AGE BURSTS?

    Energy Technology Data Exchange (ETDEWEB)

    Webster, David; Bland-Hawthorn, Joss [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Sutherland, Ralph, E-mail: d.webster@physics.usyd.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Rd, Weston, ACT 2611 (Australia)

    2015-01-30

    We model the chemical evolution of six ultra-faint dwarfs (UFDs): Bootes I, Canes Venatici II, Coma Berenices, Hercules, Leo IV, and Ursa Major I based on their recently determined star formation histories. We show that two single-age bursts cannot explain the observed [α/Fe] versus [Fe/H] distribution in these galaxies and that some self-enrichment is required within the first burst. An alternative scenario is modeled, in which star formation is continuous except for short interruptions when one or more supernovae temporarily blow the dense gas out from the center of the system. This model allows for self-enrichment and can reproduce the chemical abundances of the UFDs in which the second burst is only a trace population. We conclude that the most likely star formation history is one or two extended periods of star formation, with the first burst lasting for at least 100 Myr. As found in earlier work, the observed properties of UFDs can be explained by formation at a low mass (M{sub vir}∼10{sup 7} M{sub ⊙}), rather than being stripped remnants of much larger systems.

  1. New radio observations of NGC1275

    International Nuclear Information System (INIS)

    Pedlar, A.; Perley, R.; Crane, P.; Harrison, B.; Davies, R.D.

    1986-01-01

    VLA maps are presented for NGC1275 at 20 cm, with resolutions ranging from 1 to 40 arcsec. Over the central 30 arcsec there is evidence for collimated ejection at position angle -160 deg. Outside this region the radio structure bends rapidly by approximately 90 deg before merging into the 10-arcmin radio halo. It is suggested that models of pressure-driven accretion flows should take into account the presence of the relativistic gas which is responsible for the radio halo. 14 references

  2. 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.

  3. La radio glocal cross-media: la alternativa ante la reducción de espacios de proximidad local en la radio convencional

    Directory of Open Access Journals (Sweden)

    José María Chomón Serna

    2016-01-01

    Full Text Available Palabras clave: Información, Proximidad, Radio-periódico, Inmediatez, Cross-media, Transmedia ResumenLas cadenas radiofónicas españolas, Ser, Onda Cero, Cope y RNE (Radio 5 Todo Noticias compiten por la reducción de la proximidad local, sin reparar en las consecuencias y fijando como objetivo los recortes económicos.Las cadenas radiofónicas, mediante un proceso de mimetismo, aplican una misma pauta de programación local, y tienden a instaurar un nuevo modelo radiofónico: la “radio-periódico”. Este modelo supone la pérdida de dos de las principales características de la radio: la inmediatez y la cercanía.La estrategia de reducción de contenidos locales no supone en este contexto una contradicción si se compensa mediante las herramientas que propicien que el “prosumer” acceda a contenidos “glocales”, facilitando la actividad cross-media  y el relato transmedia. Keywords: Information, Proximity, Radio-newspaper, Immediacy, Cross-media, Transmedia AbstractThe Spanish radio stations Ser, Onda Cero, Cope and RNE (Radio 5 Todo Noticias compete for the reduction of local proximity, without thinking about the consequences and setting the economic cutbacks as the only objective.The radio stations, through a mimicry process, make use of the same pattern of local schedule, having established a new radio model: the radio-newspaper. This model means the loss of two of the main radio features: The immediacy and the nearness.The reduction of local content strategy does not mean, in this context, a contradiction if it is offsetting by the tools that propitiate the access of the "prosumer" to "glocal" contents, making easier the cross-media activity and the transmedia stories.

  4. Searching for Faint Traces of CO(2-1) and HCN(4-3) Gas In Debris Disks

    Science.gov (United States)

    Stafford Lambros, Zachary; Hughes, A. Meredith

    2018-01-01

    The surprising presence of molecular gas in the debris disks around main sequence stars provides an opportunity to study the dissipation of primordial gas and, potentially, the composition of gas in other solar systems. Molecular gas is not expected to survive beyond the pre-main sequence phase, and it is not yet clear whether the gas is a remnant of the primordial protoplanetary material or whether the gas, like the dust, is second-generation material produced by collisional or photodesorption from planetesimals, exocomets, or the icy mantles of dust grains. Here we present two related efforts to characterize the prevalence and properties of gas in debris disks. First, we place the lowest limits to date on the CO emission from an M star debris disk, using 0.3" resolution observations of CO(2-1) emission from the AU Mic system with the Atacama Large Millimeter/submillimeter Array (ALMA). We place a 3-sigma upper limit on the integrated flux of 0.39 Jy km/s, corresponding to a maximum CO mass of 5e10-6 (Earth Masses) if the gas is in LTE. We also present the results of an ALMA search for HCN(4-3) emission from the prototypical gas-rich debris disk around 49 Ceti at a spatial resolution of 0.3". Despite hosting one of the brightest CO-rich debris disks yet discovered, our observations of 49 Ceti also yield a low upper limit of 0.057 Jy km/s in the HCN line, leaving CO as the only molecule clearly detected in emission from a debris disk. We employ several methods of detecting faint line emission from debris disks, including a model based on Keplerian kinematics as well as a spectral shifting method previously used to detect faint CO emission from the Fomalhaut debris disk, and compare our results.

  5. The other radios: Alternative scenario in Peru

    Directory of Open Access Journals (Sweden)

    Carlos Rivadeneyra-Olcese

    2009-10-01

    Full Text Available Peruvian radio shows a huge diversity in direct proportion to its multiculturality, the same which shows a process full of different influences of social actor which have produced a complex and extremely rich scenario, that is also filled with opportunities and challenges. Beyond the great capital commercial radio are the other radios, small companies, provincial, from church or the mayor or small business owners sons of folkloric melomania, different actors with a passion to establish a new media. The multiple motivations produce a scenario with many types of radio that we wishes to start knowing.

  6. Computing angle of arrival of radio signals

    Science.gov (United States)

    Borchardt, John J.; Steele, David K.

    2017-11-07

    Various technologies pertaining to computing angle of arrival of radio signals are described. A system that is configured for computing the angle of arrival of a radio signal includes a cylindrical sheath wrapped around a cylindrical object, where the cylindrical sheath acts as a ground plane. The system further includes a plurality of antennas that are positioned about an exterior surface of the cylindrical sheath, and receivers respectively coupled to the antennas. The receivers output measurements pertaining to the radio signal. A processing circuit receives the measurements and computes the angle of arrival of the radio signal based upon the measurements.

  7. 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

  8. 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)

  9. Modular Software-Defined Radio

    Directory of Open Access Journals (Sweden)

    Rhiemeier Arnd-Ragnar

    2005-01-01

    Full Text Available In view of the technical and commercial boundary conditions for software-defined radio (SDR, it is suggestive to reconsider the concept anew from an unconventional point of view. The organizational principles of signal processing (rather than the signal processing algorithms themselves are the main focus of this work on modular software-defined radio. Modularity and flexibility are just two key characteristics of the SDR environment which extend smoothly into the modeling of hardware and software. In particular, the proposed model of signal processing software includes irregular, connected, directed, acyclic graphs with random node weights and random edges. Several approaches for mapping such software to a given hardware are discussed. Taking into account previous findings as well as new results from system simulations presented here, the paper finally concludes with the utility of pipelining as a general design guideline for modular software-defined radio.

  10. 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.

  11. 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

  12. Energy-Aware Cognitive Radio Systems

    KAUST Repository

    Bedeer, Ebrahim

    2016-01-15

    The concept of energy-aware communications has spurred the interest of the research community in the most recent years due to various environmental and economical reasons. It becomes indispensable for wireless communication systems to shift their resource allocation problems from optimizing traditional metrics, such as throughput and latency, to an environmental-friendly energy metric. Although cognitive radio systems introduce spectrum efficient usage techniques, they employ new complex technologies for spectrum sensing and sharing that consume extra energy to compensate for overhead and feedback costs. Considering an adequate energy efficiency metric—that takes into account the transmit power consumption, circuitry power, and signaling overhead—is of momentous importance such that optimal resource allocations in cognitive radio systems reduce the energy consumption. A literature survey of recent energy-efficient based resource allocations schemes is presented for cognitive radio systems. The energy efficiency performances of these schemes are analyzed and evaluated under power budget, co-channel and adjacent-channel interferences, channel estimation errors, quality-of-service, and/or fairness constraints. Finally, the opportunities and challenges of energy-aware design for cognitive radio systems are discussed.

  13. College radio as a mechanism for participatory learning: Exploring the scope for online radio based learning among undergraduates

    Directory of Open Access Journals (Sweden)

    Bahaeldin Ibrahim

    2016-03-01

    Full Text Available This paper explores the prospects of online college radio at Sur College of Applied Sciences, its need among students and the possible scope of its contributions to student learning, engagement and community service. It explores the method of developing a holistic mechanism to capture the possibilities of maximizing learning experience by employing college radio as an educational tool to understand the micro-dynamics and localized necessities that deem it necessary or unnecessary. Through this, it attempts to locate an appropriate mechanism, and targeted use of the college radio in contributing to the learning outcomes and educational experience of the students. The study finds considerable scope for radio based learning at Sur College of Applied Sciences across a range of uses and gratification indicators consistent with the primary objectives of the college. The study discusses the theoretical and practical implications of the findings, and the pedagogical significance of the college radio as an alternative.

  14. Evolvable Neural Software System

    Science.gov (United States)

    Curtis, Steven A.

    2009-01-01

    The Evolvable Neural Software System (ENSS) is composed of sets of Neural Basis Functions (NBFs), which can be totally autonomously created and removed according to the changing needs and requirements of the software system. The resulting structure is both hierarchical and self-similar in that a given set of NBFs may have a ruler NBF, which in turn communicates with other sets of NBFs. These sets of NBFs may function as nodes to a ruler node, which are also NBF constructs. In this manner, the synthetic neural system can exhibit the complexity, three-dimensional connectivity, and adaptability of biological neural systems. An added advantage of ENSS over a natural neural system is its ability to modify its core genetic code in response to environmental changes as reflected in needs and requirements. The neural system is fully adaptive and evolvable and is trainable before release. It continues to rewire itself while on the job. The NBF is a unique, bilevel intelligence neural system composed of a higher-level heuristic neural system (HNS) and a lower-level, autonomic neural system (ANS). Taken together, the HNS and the ANS give each NBF the complete capabilities of a biological neural system to match sensory inputs to actions. Another feature of the NBF is the Evolvable Neural Interface (ENI), which links the HNS and ANS. The ENI solves the interface problem between these two systems by actively adapting and evolving from a primitive initial state (a Neural Thread) to a complicated, operational ENI and successfully adapting to a training sequence of sensory input. This simulates the adaptation of a biological neural system in a developmental phase. Within the greater multi-NBF and multi-node ENSS, self-similar ENI s provide the basis for inter-NBF and inter-node connectivity.

  15. Radio Context Awareness and Applications

    Directory of Open Access Journals (Sweden)

    Luca Reggiani

    2013-01-01

    Full Text Available The context refers to “any information that can be used to characterize the situation of an entity, where an entity can be a person, place, or physical object.” Radio context awareness is defined as the ability of detecting and estimating a system state or parameter, either globally or concerning one of its components, in a radio system for enhancing performance at the physical, network, or application layers. In this paper, we review the fundamentals of context awareness and the recent advances in the main radio techniques that increase the context awareness and smartness, posing challenges and renewed opportunities to added-value applications in the context of the next generation of wireless networks.

  16. 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...

  17. La radio no está amenazada por internet

    Directory of Open Access Journals (Sweden)

    Bruce Girard

    2015-01-01

    Full Text Available La radio es mucho más penetrante y asequible, el uso de los servicios de Internet puede contribuir a informar mejor a sus clientes y establecer interactividad. En vista que por ahora la accesibilidad del Internet es accesible solo a unos pocos, para la radio no es una amenaza el Internet. Enuncia los roles de la radio y señala que está considerada como un vínculo comunitario. Trata además sobre las radio-cadenas satelitales, la radio e Internet: convergencia para la democracia y el crecimiento de la brecha de los que acceden a la información.

  18. REFERENCE-LESS DETECTION, ASTROMETRY, AND PHOTOMETRY OF FAINT COMPANIONS WITH ADAPTIVE OPTICS

    International Nuclear Information System (INIS)

    Gladysz, Szymon; Christou, Julian C.

    2009-01-01

    We propose a complete framework for the detection, astrometry, and photometry of faint companions from a sequence of adaptive optics (AO) corrected short exposures. The algorithms exploit the difference in statistics between the on-axis and off-axis intensity of the AO point-spread function (PSF) to differentiate real sources from speckles. We validate the new approach and illustrate its performance using moderate Strehl ratio data obtained with the natural guide star AO system on the Lick Observatory's 3 m Shane Telescope. We obtain almost a 2 mag gain in achievable contrast by using our detection method compared to 5σ detectability in long exposures. We also present a first guide to expected accuracy of differential photometry and astrometry with the new techniques. Our approach performs better than PSF-fitting in general and especially so for close companions, which are located within the uncompensated seeing (speckle) halo. All three proposed algorithms are self-calibrating, i.e., they do not require observation of a calibration star. One of the advantages of this approach is improved observing efficiency.

  19. An Optical Receiver Post Processing System for the Integrated Radio and Optical Communications Software Defined Radio Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Tokars, Roger P.; Wroblewski, Adam C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administrations (NASA) Glenn Research Center is investigating the feasibility of a hybrid radio frequency (RF) and optical communication system for future deep space missions. As a part of this investigation, a test bed for a radio frequency (RF) and optical software defined radio (SDR) has been built. Receivers and modems for the NASA deep space optical waveform are not commercially available so a custom ground optical receiver system has been built. This paper documents the ground optical receiver, which is used in order to test the RF and optical SDR in a free space optical communications link.

  20. An Optical Receiver Post-Processing System for the Integrated Radio and Optical Communications Software Defined Radio Test Bed

    Science.gov (United States)

    Nappier, Jennifer M.; Tokars, Roger P.; Wroblewski, Adam C.

    2016-01-01

    The Integrated Radio and Optical Communications (iROC) project at the National Aeronautics and Space Administration's (NASA) Glenn Research Center is investigating the feasibility of a hybrid radio frequency (RF) and optical communication system for future deep space missions. As a part of this investigation, a test bed for a radio frequency (RF) and optical software defined radio (SDR) has been built. Receivers and modems for the NASA deep space optical waveform are not commercially available so a custom ground optical receiver system has been built. This paper documents the ground optical receiver, which is used in order to test the RF and optical SDR in a free space optical communications link.

  1. Contribution Towards Practical Cognitive Radios Systems

    KAUST Repository

    Ben Ghorbel, Mahdi

    2013-01-01

    to cognitive radio systems while taking into account practical constraints. Cogni- tive radios requires a capability to detect spectrum holes (spectrum sensing) and a scheduling flexibility to avoid the occupied spectrum and selectively use the empty spectrum

  2. A Radio-Controlled Car Challenge

    Science.gov (United States)

    Roman, Harry T.

    2010-01-01

    Watching a radio-controlled car zip along a sidewalk or street has become a common sight. Within this toy are the basic ingredients of a mobile robot, used by industry for a variety of important and potentially dangerous tasks. In this challenge, students consider modifying an of-the-shelf, radio-controlled car, adapting it for a robotic task.

  3. MOA-2008-BLG-379Lb: A massive planet from a high magnification event with a faint source

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, D.; Sumi, T.; Fukagawa, M.; Shibai, H. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Bennett, D. P. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Bond, I. A.; Ling, C. H. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Abe, F.; Furusawa, K.; Itow, Y.; Masuda, K.; Matsubara, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa, Nagoya, Aichi 464-8601 (Japan); Botzler, C. S.; Freeman, M.; Rattenbury, N. [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory, 3037-5 Honjo, Kamogata, Asakuchi, Okayama 719-0232 (Japan); Muraki, Y. [Department of Physics, Konan University, Nishiokamoto 8-9-1, Kobe 658-8501 (Japan); Ohnishi, K. [Nagano National College of Technology, Nagano 381-8550 (Japan); Saito, To. [Tokyo Metropolitan College of Industrial Technology, Tokyo 116-8523 (Japan); Collaboration: MOA Collaboration; OGLE Collaboration; and others

    2014-01-10

    We report on the analysis of the high microlensing event MOA-2008-BLG-379, which has a strong microlensing anomaly at its peak due to a massive planet with a mass ratio of q = 6.9 × 10{sup –3}. Because the faint source star crosses the large resonant caustic, the planetary signal dominates the light curve. This is unusual for planetary microlensing events, and as a result, the planetary nature of this light curve was not immediately noticed. The planetary nature of the event was found when the Microlensing Observations in Astrophysics (MOA) Collaboration conducted a systematic study of binary microlensing events previously identified by the MOA alert system. We have conducted a Bayesian analysis based on a standard Galactic model to estimate the physical parameters of the lens system. This yields a host star mass of M{sub L}=3.3{sub −1.2}{sup +1.7} M{sub ⊙} orbited by a planet of mass m{sub P}=0.56{sub −0.27}{sup +0.24} M{sub Jup} at an orbital separation of a=3.3{sub −1.2}{sup +1.3} AU at a distance of D{sub L}=4.1{sub −1.9}{sup +1.7} kpc. The faint source magnitude of I {sub S} = 21.30 and relatively high lens-source relative proper motion of μ{sub rel} = 7.6 ± 1.6 mas yr{sup –1} imply that high angular resolution adaptive optics or Hubble Space Telescope observations are likely to be able to detect the source star, which would determine the masses and distance of the planet and its host star.

  4. 77 FR 61535 - Private Land Mobile Radio Rules

    Science.gov (United States)

    2012-10-10

    ... technology that we believe can provide valuable benefits to land mobile radio users. III. Summary of..., GPS equipment, pagers, cellular phones, mobile communications equipment, and radio and television...-114] Private Land Mobile Radio Rules AGENCY: Federal Communications Commission. ACTION: Final rule...

  5. VHF spectrum monitoring using Meraka cognitive radio platform

    CSIR Research Space (South Africa)

    Aderonmu, AI

    2012-11-01

    Full Text Available discuss the Meraka Cognitive Radio Platform (MCRP) developed using the second version of the Universal Serial Radio Peripheral (USRP2) hardware and the GNU Radio software. We also discussed how the spectrum monitoring system is being implemented...

  6. Evolving phenotypic networks in silico.

    Science.gov (United States)

    François, Paul

    2014-11-01

    Evolved gene networks are constrained by natural selection. Their structures and functions are consequently far from being random, as exemplified by the multiple instances of parallel/convergent evolution. One can thus ask if features of actual gene networks can be recovered from evolutionary first principles. I review a method for in silico evolution of small models of gene networks aiming at performing predefined biological functions. I summarize the current implementation of the algorithm, insisting on the construction of a proper "fitness" function. I illustrate the approach on three examples: biochemical adaptation, ligand discrimination and vertebrate segmentation (somitogenesis). While the structure of the evolved networks is variable, dynamics of our evolved networks are usually constrained and present many similar features to actual gene networks, including properties that were not explicitly selected for. In silico evolution can thus be used to predict biological behaviours without a detailed knowledge of the mapping between genotype and phenotype. Copyright © 2014 The Author. Published by Elsevier Ltd.. All rights reserved.

  7. 3C 254: the alignment effect and unification schemes

    Science.gov (United States)

    Bremer, M. N.

    1997-01-01

    3C 254 is a radio-loud quasar at z=0.734. Optical line and continuum emission from the underlying galaxy is clearly extended and aligned with the radio axis; the object shows the so-called `alignment effect' which is often seen in powerful radio galaxies. This is the clearest case yet of the continuum alignment effect in a radio-loud quasar. The object is one of the most lobe-dominated 3C quasars; the significance of the aligned emission in this source is discussed in terms of orientation-based unification schemes for radio-loud quasars and radio galaxies. 3C 254 is a very asymmetric radio source and it is shown that the radio structure on the side with the shortest nucleus-hotspot distance is interacting with the emission-line gas surrounding the quasar. It is also shown that the quasar is surrounded by an overdensity of faint objects, consistent with a cluster or group of galaxies around the object.

  8. 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...

  9. canEvolve: a web portal for integrative oncogenomics.

    Directory of Open Access Journals (Sweden)

    Mehmet Kemal Samur

    Full Text Available BACKGROUND & OBJECTIVE: Genome-wide profiles of tumors obtained using functional genomics platforms are being deposited to the public repositories at an astronomical scale, as a result of focused efforts by individual laboratories and large projects such as the Cancer Genome Atlas (TCGA and the International Cancer Genome Consortium. Consequently, there is an urgent need for reliable tools that integrate and interpret these data in light of current knowledge and disseminate results to biomedical researchers in a user-friendly manner. We have built the canEvolve web portal to meet this need. RESULTS: canEvolve query functionalities are designed to fulfill most frequent analysis needs of cancer researchers with a view to generate novel hypotheses. canEvolve stores gene, microRNA (miRNA and protein expression profiles, copy number alterations for multiple cancer types, and protein-protein interaction information. canEvolve allows querying of results of primary analysis, integrative analysis and network analysis of oncogenomics data. The querying for primary analysis includes differential gene and miRNA expression as well as changes in gene copy number measured with SNP microarrays. canEvolve provides results of integrative analysis of gene expression profiles with copy number alterations and with miRNA profiles as well as generalized integrative analysis using gene set enrichment analysis. The network analysis capability includes storage and visualization of gene co-expression, inferred gene regulatory networks and protein-protein interaction information. Finally, canEvolve provides correlations between gene expression and clinical outcomes in terms of univariate survival analysis. CONCLUSION: At present canEvolve provides different types of information extracted from 90 cancer genomics studies comprising of more than 10,000 patients. The presence of multiple data types, novel integrative analysis for identifying regulators of oncogenesis, network

  10. The statistics of low frequency radio interference at the Murchison Radio-astronomy Observatory

    OpenAIRE

    Sokolowski, Marcin; Wayth, Randall B.; Lewis, Morgan

    2016-01-01

    We characterize the low frequency radio-frequency interference (RFI) environment at the Murchison Radio-astronomy Observatory (MRO), the location selected for the low-frequency component of the Square Kilometre Array. Data were collected from the BIGHORNS instrument, located at the MRO, which records a contiguous bandwidth between 70 and 300 MHz, between November 2014 to March 2015 inclusive. The data were processed to identify RFI, and we describe a series of statistics in both the time and ...

  11. Radio transmission system for industrial area

    International Nuclear Information System (INIS)

    Iliescu, M.; Culcer, M.; Curuia, M.; Anghel, N.M.; Stefanescu, I.

    2003-01-01

    The paper deals with a data transmission system operating in a large, noisy industrial area. The radio transmission system permits data and commands communication between the local units of collecting data and a central monitoring and/or command station ( dispatch). The communication support are radio waves in the range 450 MHz. The transducers are of transmitter type, with 4-20 mA output signal, providing information about environmental and/or work parameters. Data are primarily acquisitioned in a data logger with microcontroller, then transmitted via a FSK radio modem and a radio station to the dispatch. Data logger can also be connected in a network. The dispatch personal computer receives and processes data and transmits commands. The system functioning is supervised by a communication software in MCS - 51 assembler and an application software in Visual C ++ . (author)

  12. 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

  13. 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.)

  14. Hybrid cognitive engine for radio systems adaptation

    KAUST Repository

    Alqerm, Ismail

    2017-07-20

    Network efficiency and proper utilization of its resources are essential requirements to operate wireless networks in an optimal fashion. Cognitive radio aims to fulfill these requirements by exploiting artificial intelligence techniques to create an entity called cognitive engine. Cognitive engine exploits awareness about the surrounding radio environment to optimize the use of radio resources and adapt relevant transmission parameters. In this paper, we propose a hybrid cognitive engine that employs Case Based Reasoning (CBR) and Decision Trees (DTs) to perform radio adaptation in multi-carriers wireless networks. The engine complexity is reduced by employing DTs to improve the indexing methodology used in CBR cases retrieval. The performance of our hybrid engine is validated using software defined radios implementation and simulation in multi-carrier environment. The system throughput, signal to noise and interference ratio, and packet error rate are obtained and compared with other schemes in different scenarios.

  15. Real-Time Measurements for Adaptive and Cognitive Radio Systems

    Directory of Open Access Journals (Sweden)

    Hüseyin Arslan

    2009-01-01

    Full Text Available Adaptive and cognitive radios (CR have been becoming popular for optimizing mobile radio system transmission and reception. One of the most important elements of the adaptive radio and CR concepts is the ability to measure, sense, learn about, and be aware of parameters related to the radio channel characteristics, availability of spectrum and power, interference and noise temperature, operational environment of radio, user requirements and applications, available networks and infrastructures, local policies, other operating restrictions, and so on. This paper discusses some of the important measurement parameters for enabling adaptive radio and CR systems along with their relationships and impacts on the performance including relevant challenges.

  16. 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

  17. Emergence of radio astronomy-the Indian scenario

    International Nuclear Information System (INIS)

    Das Gupta, M.K.

    1990-01-01

    Professor S.K. Mitra, the initiator of post graduate studies in radio-electronics and the pioneer of radio research in India realized the far-reaching importance of the then emerging science of radio astronomy, as early as mid-forties. The exposition of the subject has been dedicated to the memory of esteemed Professor S.K. Mitra. The article is divided into three broad heads, namely (i)the emergence of radioastronomy-achievements made so far, (ii)some major contributions made by the Indian scientists working abroad in the fifties, and (iii) the emergence of radio astronomy in India and its present status. (author). 55 refs

  18. Cognitive Radio MAC Protocol for WLAN

    DEFF Research Database (Denmark)

    Zhang, Qi; Fitzek, Frank H.P.; Iversen, Villy Bæk

    2008-01-01

    hole; moreover, it designs dual inband sensing scheme to detect primary user appearance. Additionally, C-CSMA/CA has the advantage to effectively solve the cognitive radio self-coexistence issues in the overlapping CR BSSs scenario. It also realizes station-based dynamic resource selection......To solve the performance degradation issue in current WLAN caused by the crowded unlicensed spectrum, we propose a cognitive radio (CR) media access protocol, C-CSMA/CA. The basic idea is that with cognitive radio techniques the WLAN devices can not only access the legacy WLAN unlicensed spectrum...

  19. Predicting radio fluxes of extrasolar planets (Griessmeier+, 2007)

    NARCIS (Netherlands)

    Griessmeier, J.M.; Zarka, P.; Spreeuw, H.

    2007-01-01

    Expected radio emission from presently known exoplanets. For each of the currently known exoplanets, we list its estimated magnetic moment, maximum radio emission frequency, plasma frequency in the ambient stellar wind, and radio fluxes according to three different models. (1 data file).

  20. 47 CFR 0.485 - Commercial radio operator examinations.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Commercial radio operator examinations. 0.485....485 Commercial radio operator examinations. Generally, written and telegraphy examinations for commercial radio operator licenses shall be conducted at locations and times specified by commercial operator...