Science.gov

Sample records for compact extragalactic radio

  1. The LBA Calibrator Survey of Southern Compact Extragalactic Radio Sources - LCS1

    NASA Technical Reports Server (NTRS)

    Petrov, Leonid; Phillips, Chris; Bertarini, Alessandra; Murphy, Tara; Sadler, Elaine M.

    2011-01-01

    We present a catalogue of accurate positions and correlated flux densities for 410 flat-spectrum, compact extragalactic radio sources previously detected in the Australia Telescope 20 GHz (AT20G) survey. The catalogue spans the declination range [-90deg, -40deg] and was constructed from four 24-h very long baseline interferometry (VLBI) observing sessions with the Australian Long Baseline Array at 8.3 GHz. The VLBI detection rate in these experiments is 97 per cent, the median uncertainty of the source positions is 2.6 mas and the median correlated flux density on projected baselines longer than 1000 km is 0.14 Jy. The goals of this work are (1) to provide a pool of southern sources with positions accurate to a few milliarcsec, which can be used for phase-referencing observations, geodetic VLBI and space navigation; (2) to extend the complete flux-limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec-scale properties of high-frequency selected sources from the AT20G survey. As a result of this VLBI campaign, the number of compact radio sources south of declination -40deg which have measured VLBI correlated flux densities and positions known to milliarcsec accuracy has increased by a factor of 3.5.

  2. Effects of gamma-ray, neutrino, and particle production on the energetics and dynamics of compact extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Vestrand, W. T.; Scott, J. S.; Marscher, A. P.; Christiansen, W. A.

    1981-01-01

    Consideration is given to particle production and high-energy radiation within apparently superluminal radio components of extragalactic radio sources forming within the apparent region of nuclear activity of a quasar or active galaxy. The physical conditions in compact components observed as radio emitters are derived for the quasars 3C 273 and 3C 345 and extrapolated to those of initial components of sizes on the order of 10 to the 15th cm on the basis of two-dimensional relativistic jet and relativistic three-dimensional models of component expansion. Probabilities that a given particle avoids an inelastic collision in the relativistic plasma are calculated for both cases which show that collisions which produce particles and radiation may be very important during the formation of a compact radio component. The consequences of electron-positron production, bremsstrahlung and proton-proton inelastic collisions ultimately giving rise to neutrinos and gamma rays for the development and energetics of the radio component are then examined, and upper limits to the amount of energy which can be channeled into radio components from an active region without giving rise to a high-energy X-ray source are derived.

  3. Extragalactic Radio Sources

    ERIC Educational Resources Information Center

    Kellerman, Kenneth I.

    1973-01-01

    Discusses new problems arising from the growing observational data through radio telescope arrays, involving the origin of radio sources, apparent superluminal velocities, conversion of radio sources to relativistic particles, and the nature of compact opaque and extended transparent sources. New physics may be needed to answer these cosmological…

  4. The Extragalactic Radio Background

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2011-01-01

    The existence of an isotropic component of the high-latitude radio sky has been recognized for nearly fifty years, but has typically been assumed to be Galactic in origin. We use recent radio observations to test whether the observed high-latitude component could originate within either an extended Galactic halo or a more local "bubble" structure. The lack of significant polarization from the isotropic component, combined with the lack of significant correlation with the Galactic far-infrared emission, rule out an origin within the Galaxy. We conclude that an extragalactic origin is the only viable alternative for the bulk of the isotropic high-latitude emission. The extragalactic component is 2-3 times brighter than local (Galactic) emission towards the Galactic poles and is consistent with a power law in frequency with amplitude T(sub r) = 24.1 plus or minus 2.1 K and spectral index beta = -2.599 plus or minus 0.036 evaluated at reference frequency 310 MHz.

  5. Extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.

    1984-01-01

    The standard model for extragalactic variable radio sources comprises an isotropically expanding plasmoid with frozen magnetic flux and an electron distribution which evolves adiabatically. This model leads to the following relaton between the peak luminosity L (sub nu, m) and the relevant frequency nu(sub m) which are functions of time: L(sub nu,m) is proportional to nu(sub m)(n) where N = (7n + 5)/(4n + 5). In this expression, n is the spectral index in the optically thin part of the spectrum, where L (sub nu) is proportional to nu (-n). For n in the range 0.5 to 1.5, the standard model yields N in the range 1.2 to 1.4. By contrast, analysis of observational data yields estimates of N in a small range about the mean value 0.4, in clear contradiction with the standard model.

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

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Argüeso, F.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Cabella, P.; Cappellini, B.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, L.-Y.; Christensen, P. R.; Clements, D. L.; Colafrancesco, S.; Colombi, S.; Couchot, F.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Dole, H.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Harrison, D.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Jaffe, A. H.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leach, S.; Leahy, J. P.; Leonardi, R.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Magliocchetti, M.; Maino, D.; Mandolesi, N.; Mann, R.; Maris, M.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; O'Dwyer, I. J.; Osborne, S.; Pajot, F.; Paladini, R.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sajina, A.; Sandri, M.; Scott, D.; Seiffert, M. D.; Serjeant, S.; Shellard, P.; Smoot, G. F.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wilkinson, A.; Yvon, D.; Zacchei, A.; Zonca, A.

    2011-12-01

    The data reported in Planck's Early Release Compact Source Catalogue (ERCSC) are exploited to measure the number counts (dN/dS) of extragalactic radio sources at 30, 44, 70, 100, 143 and 217 GHz. Due to the full-sky nature of the catalogue, this measurement extends to the rarest and brightest sources in the sky. At lower frequencies (30, 44, and 70 GHz) our counts are in very good agreement with estimates based on WMAP data, being somewhat deeper at 30 and 70 GHz, and somewhat shallower at 44 GHz. Planck's source counts at 143 and 217 GHz join smoothly with the fainter ones provided by the SPT and ACT surveys over small fractions of the sky. An analysis of source spectra, exploiting Planck's uniquely broad spectral coverage, finds clear evidence of a steepening of the mean spectral index above about 70 GHz. This implies that, at these frequencies, the contamination of the CMB power spectrum by radio sources below the detection limit is significantly lower than previously estimated. Corresponding author: J. González-Nuevo, e-mail: gnuevo@sissa.it

  7. Extragalactic Radio Bursts

    NASA Astrophysics Data System (ADS)

    Bailes, Matthew; Johnston, Simon; Bhat, Ramesh; Burke-Spolaor, Sarah; Barnes, David; van Straten, Willem

    2008-04-01

    We propose a sky monitoring survey that will piggy-back multibeam observations of other scientific programmes; the intent of our search is to intercept and analyse millisecond-duration, single, impulsive bursts from transient events in the extragalactic sky.

  8. Extragalactic Radio Bursts

    NASA Astrophysics Data System (ADS)

    Burke-Spolaor, Sarah; Johnston, Simon; Bailes, Matthew; Bhat, Ramesh; Barnes, David; van Straten, Willem

    2008-10-01

    We propose a sky monitoring survey that will piggy-back multibeam observations of other scientific programmes; the intent of our search is to intercept and analyse millisecond-duration, single, impulsive bursts from transient events in the extragalactic sky.

  9. X-Raying the MOJAVE Sample of Compact Extragalactic Radio Jets

    NASA Technical Reports Server (NTRS)

    Kadler, M.; Sato, G.; Tueller, J.; Sambruna, R. M.; Markwardt, C. B.; Giommi, P.; Gehrels, N.

    2007-01-01

    The MOJAVE sample is the first large radio-selected, VLBI-monitored AGN sample for which complete X-ray spectral information is being gathered. We report on the status of Swift survey observations which complement the available archival X-ray data at 0.3-10 keV and in the UV with its XRT and UVOT instruments. Many of these 133 radio-brightest AGN in the northern sky are now being observed for the first time at these energies. These and complementary other multiwavelength observations provide a large statistical sample of radio-selected AGN whose spectral energy distributions we measured from radio to gamma-ray wavelengths, available at the beginning of GLAST operations in 2008. Here, we report the X-ray spectral characteristics of 36 of these previously unobserved MOJAVE sources. In addition, the number of MOJAVE sources detected by the BAT instrument in the hard X-ray band is growing: we report the detection of five new blazars with BAT.

  10. A catalog of selected compact radio sources for the construction of an extragalactic radio/optical reference frame (Argue et al. 1984): Documentation for the machine-readable version

    NASA Technical Reports Server (NTRS)

    1990-01-01

    This document describes the machine readable version of the Selected Compact Radio Source Catalog as it is currently being distributed from the international network of astronomical data centers. It is intended to enable users to read and process the computerized catalog. The catalog contains 233 strong, compact extragalactic radio sources having identified optical counterparts. The machine version contains the same data as the published catalog and includes source identifications, equatorial positions at J2000.0 and their mean errors, object classifications, visual magnitudes, redshift, 5-GHz flux densities, and comments.

  11. Populations of extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Wall, J. V.

    In the late 1950s and early 1960s, radio sky surveys were the center of an intense and public debate -- Big-Bang versus Steady-State cosmology -- the arguments revolving about source counts and statistical interpretations in the face of instrumental complications. The 1965 discovery of the microwave background took the fire from the debate, but left the momentum in place for large-area radio surveys at different frequencies, and for extensive identification/redshift-measurement programs. By the 1970s the data enabled us to start disentangling the different populations of extragalactic radio sources. We could refine our taxonomy, and we could view the possibility of delineating individual cosmic histories and evolutions. We could at least describe a goal to elucidate the birth-life-death cycles of the objects involved 1quasi-stellar objects (QSOs) and radio galaxies: together the 'active galactic nuclei' (AGNs)1 whose unaccountably prodigious energies somehow produce the beautifully aligned radio structures with which we are now familiar. One part of John Bolton's vision was to see how distorted a view of the AGN universe the original long-wavelength surveys provided. One legacy is thus the 'short-wavelength survey' for extragalactic radio sources, which has done so much to balance our picture of the radio sky. And indeed the legacy continues in the form of the immense sky surveys at present under way, complete with their sub-industries of radio-positioning and identification. From these, yet further results are emerging on spatial distribution and the skeleton structure of the universe. It is the purpose of this paper to outline something of this current view of the populations, their differences, similarities and unifying concepts.

  12. ARCADE Detection of an Extragalactic Radio Background

    NASA Technical Reports Server (NTRS)

    Kogut, Alan J.

    2009-01-01

    Sometimes when we look for one thing we stumble on something else. The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) was designed to measure the blackbody spectrum of the cosmic microwave background to search for spectral distortions related to the epoch of reionization. Instead, the July 2006 flight found evidence for an extragalactic radio background with amplitude six times brighter than the expected contribution from faint radio sources. The author discusses the ARCADE instrument and the evidence for an extragalactic radio background.

  13. Plan for VLBI observations of close approaches of Jupiter to compact extragalactic radio sources in 2014-2016

    NASA Astrophysics Data System (ADS)

    Girdiuk, A.; Titov, O.

    2014-12-01

    Very Long Baseline Interferometry is capable of measuring the gravitational delay caused by the Sun and planet gravitational fields. The post-Newtonian parameter gamma is now estimated with accuracy of sigma_gamma=2*10^(-4) using a global set of VLBI data from 1979 to present (Lambert, Gontier, 2009), and sigma_gamma=2*10^(-5) by the Cassini spacecraft (Bertotti et. al, 2003). Unfortunately, VLBI observations in S- and X-bands very close to the Solar limb (less than 2-3 degrees) are not possible due to the strong turbulence in the Solar corona. Instead, the close approach of big planets to the line of sight of the reference quasars could be also used for testing of the general relativity theory with VLBI. Jupiter is the most appropriate among the big planets due to its large mass and relatively fast apparent motion across the celestial sphere. Six close approaches of Jupiter with quasars in 2014-2016 were found using the DE405/LE405 ephemerides, including one occultation in 2016. We have formed tables of visibility for all six events for VLBI radio telescopes participating in regular IVS programs. Expected magnitudes of the relativistic effects to be measured during these events are discussed in this paper.

  14. MAGNETIC FIELDS IN LARGE-DIAMETER H II REGIONS REVEALED BY THE FARADAY ROTATION OF COMPACT EXTRAGALACTIC RADIO SOURCES

    SciTech Connect

    Harvey-Smith, L.; Madsen, G. J.; Gaensler, B. M.

    2011-08-01

    We present a study of the line-of-sight magnetic fields in five large-diameter Galactic H II regions. Using the Faraday rotation of background polarized radio sources, as well as dust-corrected H{alpha} surface brightness as a probe of electron density, we estimated the strength and orientation of the magnetic field along 93 individual sight lines through the H II regions. Each of the H II regions displayed a coherent magnetic field. The magnetic field strength (line-of-sight component) in the regions ranges from 2 to 6 {mu}G, which is similar to the typical magnetic field strength in the diffuse interstellar medium. We investigated the relationship between magnetic field strength and electron density in the five H II regions. The slope of magnetic field versus density in the low-density regime (0.8 cm{sup -3} < n{sub e} <30 cm{sup -3}) is very slightly above zero. We also calculated the ratio of thermal to magnetic pressure, {beta}{sub th}, for each data point, which fell in the range 1.01 < {beta}{sub th} < 25. Finally, we studied the orientation of the magnetic field in the solar neighborhood (d < 1.1 kpc) using our data from five H II regions along with existing measurements of the line-of-sight magnetic field strength from polarized pulsars whose distances have been determined from their annual parallax. We identify a net direction for the magnetic field in the solar neighborhood, but find no evidence for a preferred vertical direction of the magnetic field above or below the Galactic plane.

  15. Radio properties of extragalactic IRAS sources

    NASA Technical Reports Server (NTRS)

    Condon, J. J.; Broderick, J. J.

    1991-01-01

    The present study identifies extragalactic sources from the IRAS Faint Source Catalog by position coincidence with radio sources stronger than 25 mJy and lying north of +5 deg on the Green Bank 4.85 GHz sky maps. Published VLA maps, new 4.86 GHz VLA maps made with 15-arcsec resolution, and accurate optical positions are used to confirm 122 of these candidate identifications. Normal and starburst spiral galaxies were found to comprise about 97 percent of the FIR flux-limited sample. Radio-loud 'monsters' with q less than 2.25 dominate the radio emission from about 2 percent of the FIR source sample, and radio-quiet monsters are responsible for the FIR emission from less than about 1 percent of the FIR sample. All of the radio-identified sources are optically identified, mostly with relatively bright nearby galaxies. No evidence was found for any new populations of high-redshift FIR sources, nonthermal sources with steep FIR/optical spectra, or dust-shrouded sources visible only at FIR and radio wavelengths.

  16. The unusual smoothness of the extragalactic unresolved radio background

    SciTech Connect

    Holder, Gilbert P.

    2014-01-01

    If the radio background is coming from cosmological sources, there should be some amount of clustering due to the large scale structure in the universe. Simple models for the expected clustering combined with the recent measurement by ARCADE-2 of the mean extragalactic temperature lead to predicted clustering levels that are substantially above upper limits from searches for anisotropy on arcminute scales using the Australia Telescope Compact Array and the Very Large Array. The rms temperature variations in the cosmic radio background appear to be more than a factor of 10 smaller (in temperature) than the fluctuations in the cosmic infrared background. It is therefore extremely unlikely that this background comes from galaxies, galaxy clusters, or any sources that trace dark matter halos at z ≲ 5, unless typical sources are smooth on arcminute scales, requiring typical sizes of several Mpc.

  17. THE DYNAMIC EVOLUTION OF YOUNG EXTRAGALACTIC RADIO SOURCES

    SciTech Connect

    An Tao; Baan, Willem A. E-mail: baan@astron.nl

    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.

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

    NASA Technical Reports Server (NTRS)

    Aatrokoski, J.; Ade, P. A. R.; Aghanim, N.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Amaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoit, A.; Berdyugin, A.; Bernard, J. P.; Bersanelli, M.; Bhatia, R.; Bonaldi, A.; Bonavera, L.; Gehrels, 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 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.

  19. Radio properties of Compact Steep Spectrum and GHz-Peaked Spectrum radio sources

    NASA Astrophysics Data System (ADS)

    Orienti, M.

    2016-02-01

    Compact steep spectrum (CSS) and GHz-peaked spectrum (GPS) radio sources represent a large fraction of the extragalactic objects in flux density-limited samples. They are compact, powerful radio sources whose synchrotron peak frequency ranges between a few hundred MHz to several GHz. CSS and GPS radio sources are currently interpreted as objects in which the radio emission is in an early evolutionary stage. In this contribution I review the radio properties and the physical characteristics of this class of radio sources, and the interplay between their radio emission and the ambient medium of the host galaxy.

  20. Gamma rays from extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Dermer, Charles D.; Schlickeiser, Reinhard; Mastichiadis, Apostolos

    1992-01-01

    It is proposed that the important connection between 3C 273 and 3C 279, the first two extragalactic sources detected at greater than 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a radiation mechanism that focuses gamma rays in the superluminal direction, due to Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet.

  1. The Catalog of Positions of Optically Bright Extragalactic Radio Sources OBRS-1

    NASA Technical Reports Server (NTRS)

    Petrov, L.

    2011-01-01

    It is expected that the European Space Agency mission Gaia will make it possible to determine coordinates in the optical domain of more than 500,000 quasars. In 2006, a radio astrometry project was launched with the overall goal of making comparisons between coordinate systems derived from future space-born astrometry instruments and the coordinate system constructed from analysis of global very long baseline interferometry (VLBI) more robust. Investigation of the rotation, zonal errors, and non-alignment of the radio and optical positions caused by both radio and optical structures is needed to validate both techniques. In order to support these studies, the densification of the list of compact extragalactic objects that are bright in both radio and optical ranges is desirable. A set of 105 objects from the list of 398 compact extragalactic radio sources with decl. > -10deg was observed with the Very Long Baseline Array and European VLBI Network (EVN) with the primary goal of producing images with milliarcsecond resolution. These sources are brighter than 18 mag in the V band, and they were previously detected by the EVN. In this paper, coordinates of observed sources have been derived with milliarcsecond accuracies from analysis of these VLBI observations using an absolute astrometry method. The catalog of positions for 105 target sources is presented. The accuracies of source coordinates are in the range of 0.3.7 mas, with a median of 1.1 mas.

  2. FIR galaxies with compact radio cores

    NASA Astrophysics Data System (ADS)

    Chini, R.; Biermann, P. L.; Kreysa, E.; Kuhr, H.; Mezger, P. G.; Schmidt, J.; Witzel, A.; Zensus, J. A.

    1987-07-01

    Comparing the IRAS point-source catalog (1985) with sources detected in a VLBI extragalactic radio source survey (Zensus et al., 1984), five FIR sources are found which all show compact radio cores. These objects have been observed with the 30-m MRT at Pico Veleta (Spain) at 1.2-mm wavelength to provide spectral coverage between IRAS and radio bands. The two galaxies among the five sources have luminosities of order 10 to the 12th solar luminosities in the FIR and thus may be super star bursters similar to Arp 220. On the other hand, all five objects have active galactic nuclei, and so the FIR luminosities may be powered by the nuclear activity. Since flat-spectrum radio sources have compact nuclear components, the 1-Jy catalog and its extension to lower flux densities (Kuehr et al., 1979 and 1981) are compared with the IRAS catalog, and a small number of additional active nuclei with strong emission in the FIR are identified. These objects can serve to study the competition between starbursts and nuclear activity to explain high FIR luminosities.

  3. Sco X-1 - A galactic radio source with an extragalactic radio morphology

    NASA Technical Reports Server (NTRS)

    Geldzahler, B. J.; Corey, B. E.; Fomalont, E. B.; Hilldrup, K.

    1981-01-01

    VLA observations of radio emissions at 1465 and 4885 MHz, of Sco X-1 confirm the existence of a colinear triple structure. Evidence that the three components of Sco X-1 are physically associated is presented, including the morphology, spectrum, variability, volume emissivity and magnetic field strength. The possibility of a physical phenomenon occurring in Sco X-1 similar to that occurring in extragalactic radio sources is discussed, and two galactic sources are found having extended emission similar to that in extragalactic objects. The extended structure of Sco X-1 is also observed to be similar to that of the hot spots in luminous extragalactic sources, and a radio source 20 arcmin from Sco X-1 is found to lie nearly along the radio axis formed by the components of Sco X-1.

  4. Flicker of extragalactic radio sources at two frequencies

    SciTech Connect

    Simonetti, J.H.; Cordes, J.M.; Heeschen, D.S.

    1985-09-01

    Dual-frequency observations of flat and steep-spectrum extragalactic radio sources made at Arecibo Observatory over a 20-day period are analyzed. As first reported by Heeschen (1982, 1984), flat-spectrum sources generally have larger intensity variations than steep-spectrum ones. A structure function analysis demonstrates a qualitative difference in the time series of the sources. The case against interstellar scintillation is examined, including a review of applicable scintillation theory. Relativistic source motion is treated as a solution to the brightness-temperature problems which arise if the variations are assumed intrinsic to the sources. 16 references.

  5. The core dominance parameter and Fermi detection of extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Liu, Zhen-Kuo; Wu, Zhong-Zu; Gu, Min-Feng

    2016-08-01

    By cross-correlating an archive sample of 542 extragalactic radio sources with the Fermi-LAT Third Source Catalog (3FGL), we have compiled a sample of 80 γ-ray sources and 462 non-Fermi sources with available core dominance parameter (R CD), and core and extended radio luminosity; all the parameters are directly measured or derived from available data in the literature. We found that R CD has significant correlations with radio core luminosity, γ-ray luminosity and γ-ray flux; the Fermi sources have on average higher R CD than non-Fermi sources. These results indicate that the Fermi sources should be more compact, and the beaming effect should play a crucial role in the detection of γ-ray emission. Moreover, our results also show Fermi sources have systematically larger radio flux than non-Fermi sources at fixed R CD, indicating larger intrinsic radio flux in Fermi sources. These results show a strong connection between radio and γ-ray flux for the present sample and indicate that the non-Fermi sources are likely due to the low beaming effect, and/or the low intrinsic γ-ray flux. This supports a scenario that has been published in the literature: a co-spatial origin of the activity for the radio and γ-ray emission, suggesting that the origin of the seed photons for the high-energy γ-ray emission is within the jet.

  6. Contribution to the diffuse radio background from extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Vernstrom, T.; Scott, Douglas; Wall, J. V.

    2011-08-01

    We examine the brightness of the cosmic radio background (CRB) by comparing the contribution from individual source counts to absolute measurements. We use a compilation of radio counts to estimate the contribution of detected sources to the CRB in several different frequency bands. Using a Monte Carlo Markov chain technique, we estimate the brightness values and uncertainties, paying attention to various sources of systematic error. At ν= 150, 325, 408, 610, 1.4, 4.8 and 8.4 GHz, our calculated contributions to the background sky temperature are 18, 2.8, 1.6, 0.71, 0.11, 0.0032 and 0.0059 K, respectively. We then compare our results to absolute measurements from the Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission (ARCADE 2) experiment. If the ARCADE 2 measurements are correct and come from sources, then there must be an additional population of radio galaxies, fainter than where current data are probing. More specifically, the Euclidean-normalized counts at 1.4 GHz have to have an additional bump below about 10 μJy.

  7. 318-MHz variability of complete samples of extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Dennison, B.; Broderick, J. J.; Ledden, J. E.; Odell, S. L.; Condon, J. J.

    1981-01-01

    It is found by a low-frequency variability survey, involving two- and three-epoch, 318-MHz observations of extragalactic sources in samples complete to 3 Jy at 1400 MHz and 1 Jy at 5000 MHz, that steep-spectrum sources do not seem to vary while all flat-spectrum sources exhibit low-frequency variability greater than 8% over about 5 yr. It is also found that the flat-spectrum sources with inverted spectra show the largest fractional variations, and that there is a correlation between the incidence of low-frequency variability and the determination that a source is an optically violent variable. These statistical properties are consistent with models which invoke radio and optical emission relativistic beaming.

  8. Predicting Changes in the Radio Emission Fluxes of Extragalactic Sources

    NASA Astrophysics Data System (ADS)

    Sukharev, A. L.; Ryabov, M. I.; Donskikh, G. I.

    2016-06-01

    Data from long-term monitoring with the 26-m University of Michigan radio telescope at a frequency of 14.5 GHz (1974-2011) is used to predict changes in the radio emission fluxes from the extragalactic sources 3C273, 3C120, 3C345, 3C446, 3C454.3, OJ287, OT081, and BLLac. The predictions are based on data on the major periods of variability and their durations obtained by wavelet analysis. The radio emission fluxes from the sources 3C345, 3C446, and 3C454.3, which have complicated variabilities, are predicted using an autoregression linear prediction method. This yields a forecast of the flux variations extending up to 5 years. Harmonic prediction is used for another group of sources, BLLac, OJ287, and OT081, with rapid variability. This approach yielded forecasts extending 4-9 years. For the sources 3C273 and 3C120, which have stable long periods, the harmonic method was also used and yielded a forecast extending up to 16 years. The reliability of the prediction was confirmed by independent observational data from the MOJAVE program for 2011-2015.

  9. Short-duration radio bursts with apparent extragalactic dispersion

    SciTech Connect

    Saint-Hilaire, P.; Benz, A. O.; Monstein, C.

    2014-11-01

    We present the results of the longest yet undertaken search for apparently extragalactic radio bursts at the Bleien Radio Observatory covering 21,000 hr (898 days). The data were searched for events of less than 50 ms FWHM duration showing a ν{sup –2} drift in the spectrogram characteristic of the delay of radio waves in plasma. We have found five cases suggesting dispersion measures between 350 and 400 cm{sup –3} pc while searching in the range of 75-2000 cm{sup –3} pc. Four of the five events occurred between 10:27 and 11:24 a.m. local civil time. The only exception occurred at night with the full Moon in the beam. It was an event that poorly fits plasma dispersion, but had the characteristics of a solar Type III burst. However, we were not able to confirm that it was a lunar reflection. All events were observed with a log-periodic dipole within 6800 hr, but none with a more directional horn antenna observing the rest of the time. These properties suggest a terrestrial origin of the 'peryton' type reported before. However, the cause of these events remains ambiguous.

  10. SUPERB - A SUrvey for Pulsars & Extragalactic Radio Bursts

    NASA Astrophysics Data System (ADS)

    Keane, Evan; Possenti, Andrea; Johnston, Simon; Kramer, Michael; Burgay, Marta; Bailes, Matthew; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; Eatough, Ralph; van Straten, Willem; Stappers, Benjamin; Bates, Samuel; Levin, Lina; Champion, David; Jameson, Andrew; Ng, Cherry; Tiburzi, Caterina; Petroff, Emily; Barr, Ewan; Flynn, Chris; Jankowski, Fabian; Caleb, Manisha; Lyon, Robert; Morello, Vincent; Bhandari, Shivani

    2014-10-01

    SUPERB is a large-scale survey for pulsars and extragalactic radio bursts. It will uses optimised GPU codes to search for pulsars and fast radio bursts (FRBs), making discoveries in real time. Handling our data as it comes in is essential for the SKA Phase I era so this work applies directly to the high-data rates of next generation telescopes. The pulsars discovered will enable studies of the interstellar medium, allow us to more accurately constrain the MSP luminosity function (which informs estimates of the SKA yield of MSPs), tests of theories of gravity and several will contribute to the precision timing projects of the PPTA. The FRBs discovered will have much more associated information than all previous detections. Firstly the discovery lag will be ~1 second, rather than months/years. The Parkes observations will be shadowed by the Molonglo telescope to allow, for the first time, localisation of FRBs, and a host of optical and high-energy telescopes will then be triggered as appropriate. This is key for identifying FRB host galaxies, so as to solve the mystery of their progenitors. The survey will discover ~20 MSPs, ~100 slower pulsars and ~10 FRBs.

  11. SUPERB - A SUrvey for Pulsars & Extragalactic Radio Bursts

    NASA Astrophysics Data System (ADS)

    Keane, Evan; Possenti, Andrea; Johnston, Simon; Kramer, Michael; Burgay, Marta; Bailes, Matthew; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; Eatough, Ralph; van Straten, Willem; Stappers, Benjamin; Bates, Samuel; Levin, Lina; Champion, David; Jameson, Andrew; Ng, Cherry; Tiburzi, Caterina; Petroff, Emily; Barr, Ewan; Flynn, Chris; Jankowski, Fabian; Caleb, Manisha; Lyon, Robert; Morello, Vincent

    2014-04-01

    SUPERB is a large-scale survey for pulsars and extragalactic radio bursts. It will use highly optimised GPU codes to search for pulsars and fast radio bursts (FRBs), making discoveries in real time. Handling our data as it comes in is essential for the SKA Phase I era so this work applies directly to the high-data rates of next generation telescopes. The pulsars discovered will enable studies of the interstellar medium, allow us to more accurately constrain the MSP luminosity function (which informs estimates of the SKA yield of MSPs), tests of theories of gravity and several will contribute to the precision timing projects of the PPTA. The FRBs discovered will have much more associated information than all previous detections. Firstly the discovery lag will be ~1 second, rather than months/years. The Parkes observations will be shadowed by the Molonglo telescope to allow, for the first time, localisation of FRBs, and a host of optical and high-energy telescopes will then be triggered as appropriate. This is key for identifying FRB host galaxies, so as to solve the mystery of their progenitors. The survey will discover ~20 MSPs, ~100 slower pulsars and ~10 FRBs.

  12. IS THERE AN UNACCOUNTED FOR EXCESS IN THE EXTRAGALACTIC COSMIC RADIO BACKGROUND?

    SciTech Connect

    Subrahmanyan, Ravi; Cowsik, Ramanath E-mail: cowsik@physics.wustl.edu

    2013-10-10

    Analyses of the distribution of absolute brightness temperature over the radio sky have recently led to suggestions that there exists a substantial unexplained extragalactic radio background. Consequently, there have been numerous attempts to place constraints on plausible origins of this 'excess'. We suggest here that this expectation of a large extragalactic background, over and above that contributed by the sources observed in the surveys, is based on an extremely simple geometry adopted to model the Galactic emission and the procedure adopted in the estimation of the extragalactic contribution. In this paper, we derive the extragalactic radio background from wide-field radio images using a more realistic modeling of the Galactic emission and decompose the sky maps at 150, 408, and 1420 MHz into anisotropic Galactic and isotropic extragalactic components. The anisotropic Galactic component is assumed to arise from a highly flattened spheroid representing the thick disk, embedded in a spherical halo, both centered at the Galactic center, along with Galactic sources, filamentary structures, and Galactic loops and spurs. All components are constrained to be positive and the optimization scheme minimizes the sky area occupied by the complex filaments. We show that in contrast with simple modeling of Galactic emission as a plane parallel slab, the more realistic modeling yields estimates for the uniform extragalactic brightness that are consistent with expectations from known extragalactic radio source populations.

  13. 26.3 MHz radio source survey. III - Correlation with extragalactic X-ray sources

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.; Matthews, T. A.; Viner, M. R.

    1978-01-01

    The correlation between extragalactic X-ray sources and radio sources in a 26.3-MHz catalog is studied. A list of reliably identified sources is developed by examining X-ray, optical, and radio data for those candidate objects that are in or near the X-ray error boxes. The source 3UR 0432+05 is identified with 3C 120, 3UR 1555+27 (identified with A2142) is shown to be a steep-spectrum radio source, and it is found that 86% of the high-galactic-latitude sources can be reliably identified when the X-ray source error areas are no more than 1 sq deg. The results also indicate that: (1) X-ray sources identified with clusters of galaxies as a whole, with individual galaxies in clusters, and with separate isolated galaxies have similar decametric properties in that their spectral indices and radio luminosities fall in the same range; (2) there is a Bautz-Morgan dependence of both the X-ray and the decametric luminosities of clusters and of individual objects in clusters; and (3) the X-ray luminosity of all except compact sources appears to be approximately proportional to the decametric luminosity.

  14. The discovery of strong extragalactic polarization using the Parkes Radio Telescope

    NASA Astrophysics Data System (ADS)

    Bracewell, Ronald N.

    2002-12-01

    By the end of 1961, interferometry to arc-minute precision in the East-West direction had resolved the compact source at the centre of Centaurus A into two equal components spaced about 5‧ in right ascension and with measured widths. Were they on the dark bar of the associated extragalactic nebula, NGC 5128, and perhaps indicatios of a toroidal source, or were they in the perpendicular direction and on their way out to feed the extended radio source Centaurus A? The 6‧.7 pencil beam of the Parkes Radio Telescope, employed in an unusual scanning mode, was capable of just separating the peaks and resolving the ambiguity in declination. In 1962 April, I carried out the first observations of linear polarization in Centaurus A using the Parkes antenna, and these were soon followed by other observations made by Brian Cooper and Marcus Price and then by Frank Gardner and John Whiteoak. Because the research papers reporting these pioneering observations were not published in chronological order and the dates of the observations and submission of the manuscripts ware not mentioned in them there has been considerable confusion surrounding the discovery history of Centaurus A polarization at Parkes, and this has been compounded by a misleading contemporary newspaper report, uninformed folklore, and conflicting recollectioms printed 30 years after the event. This paper clarifies the situation by presenting a first-hand account of the original observations and associated publications.

  15. Compact radio cores in radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Maini, A.; Prandoni, I.; Norris, R. P.; Giovannini, G.; Spitler, L. R.

    2016-04-01

    Context. The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGNs) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. Aims: We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. Methods: We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. Results: We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. Conclusions: We report on a first direct evidence of radio cores in RQ AGNs at cosmological redshifts. Our detections show that some of the sources that are classified as RQ contain an active AGN that can contribute significantly (~50% or more) to the total radio emission.

  16. Extragalactic astronomy

    NASA Technical Reports Server (NTRS)

    Burbidge, E. M.

    1986-01-01

    Components of the active extragalactic universe are examined to discover what extragalactic objects exhibit physical processes of the same kind as those thought to be important within the galaxy. Radio galaxies; quasars; bulk ejection from galactic objects such as novae supernovae, and other galactic nuclei; the red shifts of quasars; and the possibility of non-cosmological red shifts are among the topics discussed. It is concluded that the highest energy cosmic rays may have an extragalactic or extragalactic origin.

  17. Compact Radio Sources in NGC 660

    NASA Astrophysics Data System (ADS)

    Wiercigroch, A. B.

    1995-12-01

    The nuclei of starburst galaxies are often obscured by dust and hence are probed best in non-visual wavelength regimes such as the infrared and radio. For example, radio studies of classical starburst galaxies such as NGC 253 and M82 have identified ~ 50 compact sources in each galaxy. One of the purposes of this type of observing program has been to classify the compact radio sources as H II regions or radio supernovae, and to estimate the supernova rates. If obtainable, spectral indices are used to identify the compact structures; otherwise supporting evidence or assumptions are needed. NGC 660, located at a distance of 7.5 Mpc, is a strong candidate for a search for compact radio sources. It is a relatively strong infrared emitter, has far infrared colors similar to NGC 253 and M82, and shows several peaks in published Very Large Array (VLA) maps at 6 cm and 20 cm. We therefore observed NGC 660 at 3.6 cm in the A-configuration of the VLA on 1995 July 13--14. Total integration time on-source was 4.8 hrs. The image shows a large family ( ~ 20) of compact radio structures with a flux density range of 0.1--3.4 mJy, three of which have fluxes > 2.0 mJy. The source luminosities are comparable to those of the stronger sources in M82 and NGC 253, typically a few times more powerful than Cas A. A number of the compact sources appear to lie along a ring projected against the more diffuse radio emission in the galaxy's nuclear region. The work described in this paper was carried out by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  18. Host Galaxies of X-Shaped Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Springmann, Alessondra; Cheung, C. C.

    2007-05-01

    The majority of radiation from galaxies containing active galactic nuclei (AGNs) is emitted not by the stars composing the galaxy, but from an active source at the galactic center, most likely a supermassive black hole. Of particular interest are radio galaxies, the active galaxies emitting much of their radiation at radio wavelengths. Classical double-lobed radio galaxies are characterized by a single pair of "active" radio lobes. A small subset show an additional pair of lower surface brightness 'wings' of emission, thus forming an overall winged or X-shaped appearance. Two competing mechanisms have been proposed to explain the "winged" morphology. One model posits that these are the remnants left over from a relatively recent merger of a binary supermassive black hole system. Others have argued that they result naturally from strong backflow in a radio jet cocoon expanding into an asymmetric medium. We used available Sloan Digital Sky Survey r-band images of 11 X-shaped sources to measure the host galaxy ellipticities. By analyzing the host galaxy shapes, we trace the surrounding gas distribution. The radio morphologies are compared to the host galaxy parameters to analogize between differing model expectations. This work was funded by the Department of Energy's Student Undergraduate Laboratory Internship Program and the Stanford Linear Accelerator Center.

  19. Simultaneous synchrotron and adiabatic effects in multiply shocked jets in extended extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Ekejiuba, Ifeanyi E.; Wiita, Paul J.; Frazin, Richard A.

    1994-10-01

    As part of the effort to understand the radio spectra of extragalactic radio sources, we have incorporated the effects of simultaneous synchrotron and adiabatic processes for jet plasma crossing several shocks, which could produce multiple radio hot spots within the lobes. Oblique shocks compress the transverse component of the magnetic field and also boost the energy of the plasma within the shock regions. We make the assumption that more powerful jets typically pass through more shocks before terminating subsonically. A model incorporating these effects is able to reproduce the spectral evolution usually observed in the hot spots and lobes of high-luminosity double radio sources. Our results also support Gopal-Krishna & Wiita's view that the observed correlation between steeper indices and higher radio power results when a jet passes through a sequence of oblique shocks within the lobe of a radio source.

  20. Possible Fluctuation of the Position of Sagittarius A* Relative to Extragalactic Radio Sources

    NASA Astrophysics Data System (ADS)

    Hosokawa, Mizuhiko; Jauncey, David; Reynolds, John; Tzioumis, Anastasios; Ohnishi, Kouji; Fukushima, Toshio

    2002-11-01

    When we measure the position of an extragalactic radio source through the Galaxy, apparent position wander will be induced because of the gravitational deflection by intervening stars in the Galaxy. When measuring the annual parallax of a radio source with respect to the nearby extragalactic radio sources, such position wander should be taken into account. This effect is especially serious in the case of the trigonometric measurement of Sgr A*, located in the Galactic center. We estimated the optical depth and the event rate of the position wander of the extragalactic radio sources near Sgr A* and found that such position wander degrades the measurement of trigonometric parallax of Sgr A* significantly. For observations with an accuracy of 10 μas, the probability of degradation is a few tens of percent. Several years of continuous observation are needed for the separation of this gravitational position wander from the annual parallactic motion. Even for observations with an accuracy of 25 μas, a few years of continuous observation are needed to eliminate the effect of position wander.

  1. Extragalactic Synchrotron Transients in the Era of Wide-field Radio Surveys. I. Detection Rates and Light Curve Characteristics

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Williams, P. K. G.; Berger, Edo

    2015-06-01

    The impending era of wide-field radio surveys has the potential to revolutionize our understanding of astrophysical transients. Here we evaluate the prospects of a wide range of planned and hypothetical radio surveys using the properties and volumetric rates of known and hypothetical classes of extragalactic synchrotron radio transients (e.g., on-axis and off-axis gamma-ray bursts (GRBs), supernovae, tidal disruption events, compact object mergers). Utilizing these sources and physically motivated considerations we assess the allowed phase space of radio luminosity and peak timescale for extragalactic transients. We also include for the first time effects such as redshift evolution of the rates, K-corrections, and non-Euclidean luminosity distance, which affect the detection rates of the most sensitive surveys. The number of detected events is calculated by means of a Monte Carlo method, using the various survey properties (depth, cadence, area) and realistic detection criteria that include a cut on the minimum variability of the transients during the survey and an assessment of host galaxy contamination. We find that near-term GHz frequency surveys (ASKAP/VAST, Very Large Array Sky Survey) will detect few events: ≲ 30-50 on- and off-axis long GRBs (LGRBs) and off-axis tidal disruption events, and ∼ 50-100 neutron star binary mergers if ∼ 0.5% of the mergers result in a stable millisecond magnetar. Low-frequency surveys (e.g., LOFAR) are unlikely to detect any transients, while a hypothetical large-scale mm survey may detect ∼40 on-axis LGRBs. On the other hand, we find that SKA1 surveys at ∼ 0.1-1 GHz have the potential to uncover thousands of transients, mainly on-axis and off-axis LGRBs, on-axis short GRBs, off-axis TDEs, and neutron star binary mergers with magnetar remnants.

  2. Optical identifications of southern compact radio sources

    NASA Technical Reports Server (NTRS)

    Jauncey, David L.; Savage, Ann; Morabito, David D.; Preston, Robert A.; Nicolson, George C.

    1989-01-01

    Optical identifications are presented for 158 radio sources, mostly from the Southern Hemisphere, based on the coincidence between the position of the optical object and the compact milliarcsecond radio nucleus. Radio positions with an accuracy of typically 0.3 arcsec rms were measured from the observed delay and fringe rate of VLBI observations at 2.29 GHz on an Australia-to-South Africa baseline. Optical identifications and positions were measured from the UK Schmidt Telescope deep IIIa-J Southern Sky Survey plates, where available.

  3. Local Circumnuclear Magnetar Solution to Extragalactic Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Pen, Ue-Li; Connor, Liam

    2015-07-01

    We synthesize the known information about fast radio bursts (FRBs) and radio magnetars, and describe an allowed origin near nuclei of external, but non-cosmological, galaxies. This places them at z\\ll 1, within a few hundred megaparsecs. In this scenario, the high dispersion measure (DM) is dominated by the environment of the FRB, modeled on the known properties of the Milky Way center, whose innermost 100 pc provides 1000 pc cm-3. A radio loud magnetar is known to exist in our galactic center, within ˜2 arcsec of Sgr A*. Based on the polarization, DM, and scattering properties of this known magnetar, we extrapolate its properties to those of Crab-like giant pulses and SGR flares and point out their consistency with observed FRBs. We conclude that galactic center magnetars could be the source of FRBs. This scenario is readily testable with very long baseline interferometry measurements as well as with flux count statistics from large surveys such as CHIME or UTMOST.

  4. Fine structure of 25 extragalactic radio sources. [interferometric observations of quasars

    NASA Technical Reports Server (NTRS)

    Wittels, J. J.; Knight, C. A.; Shapiro, I. I.; Hinteregger, H. F.; Rogers, A. E. E.; Whitney, A. R.; Clark, T. A.; Hutton, L. K.; Marandino, G. E.; Niell, A. E.

    1975-01-01

    Interferometric observations taken at 7.8 GHz (gamma approximately = 3.8 cm) with five pairings of antennae of 25 extragalactic radio sources between April, 1972 and May, 1973 are reported. These sources exhibit a broad variety of fine structure from very simple to complex. The total flux and the correlated flux of some of the sources underwent large changes in a few weeks, while the structure and total power of others remained constant during the entire period of observation. Some aspects of the data processing and a discussion of errors are presented. Numerous figures are provided and explained. The individual radio sources are described in detail.

  5. A bright millisecond radio burst of extragalactic origin.

    PubMed

    Lorimer, D R; Bailes, M; McLaughlin, M A; Narkevic, D J; Crawford, F

    2007-11-01

    Pulsar surveys offer a rare opportunity to monitor the radio sky for impulsive burst-like events with millisecond durations. We analyzed archival survey data and found a 30-jansky dispersed burst, less than 5 milliseconds in duration, located 3 degrees from the Small Magellanic Cloud. The burst properties argue against a physical association with our Galaxy or the Small Magellanic Cloud. Current models for the free electron content in the universe imply that the burst is less than 1 gigaparsec distant. No further bursts were seen in 90 hours of additional observations, which implies that it was a singular event such as a supernova or coalescence of relativistic objects. Hundreds of similar events could occur every day and, if detected, could serve as cosmological probes. PMID:17901298

  6. The deep diffuse extragalactic radio sky at 1.75 GHz

    NASA Astrophysics Data System (ADS)

    Vernstrom, T.; Norris, Ray P.; Scott, Douglas; Wall, J. V.

    2015-03-01

    We present a study of diffuse extragalactic radio emission at 1.75 GHz from part of the ELAIS-S1 (European Large Area Infrared Space Observatory Survey - South 1) field using the Australia Telescope Compact Array. The resulting mosaic is 2.46 deg2, with a roughly constant noise region of 0.61 deg2 used for analysis. The image has a beam size of 150 arcsec × 60 arcsec and instrumental <σn> = (52 ± 5) μJy beam-1. Using point-source models from the Australia Telescope Large Area Survey, we subtract the discrete emission in this field for S ≥ 150 μJy beam-1. Comparison of the source-subtracted probability distribution, or P(D), with the predicted distribution from unsubtracted discrete emission and noise, yields an excess of (76 ± 23) μJy beam-1. Taking this as an upper limit on any extended emission, we constrain several models of extended source counts, assuming Ωsource ≤ 2 arcmin. The best-fitting models yield temperatures of the radio background from extended emission of Tb = (10 ± 7) mK, giving an upper limit on the total temperature at 1.75 GHz of (73 ± 10) mK. Further modelling shows that our data are inconsistent with the reported excess temperature of ARCADE2 to a source-count limit of 1 μJy. Our new data close a loop-hole in the previous constraints, because of the possibility of extended emission being resolved out at higher resolution. Additionally, we look at a model of cluster halo emission and two dark matter particle annihilation source-count models, and discuss general constraints on any predicted counts from such sources. Finally, we report the derived integral count at 1.4 GHz using the deepest discrete count plus our new extended-emission limits, providing numbers that can be used for planning future ultradeep surveys.

  7. Search for correlated radio and optical events in long-term studies of extragalactic sources

    NASA Technical Reports Server (NTRS)

    Pomphrey, R. B.; Smith, A. G.; Leacock, R. J.; Olsson, C. N.; Scott, R. L.; Pollock, J. T.; Edwards, P.; Dent, W. A.

    1976-01-01

    For the first time, long-term records of radio and optical fluxes of a large sample of variable extragalactic sources have been assembled and compared, with linear cross-correlation analysis being used to reinforce the visual comparisons. Only in the case of the BL Lac object OJ 287 is the correlation between radio and optical records strong. In the majority of cases there is no evidence of significant correlation, although nine sources show limited or weak evidence of correlation. The results do not support naive extrapolation of the expanding source model. The general absence of strong correlation between the radio and optical regions has important implications for the energetics of events occurring in such sources.

  8. Compact radio sources in the galactic plane

    NASA Technical Reports Server (NTRS)

    Jones, Terry Jay; Garwood, Robert; Dickey, John M.

    1988-01-01

    The preliminary results of a search for infrared counterparts to compact continuum radio sources found within 0.5 deg of the Galactic plane are presented. Out of 75 positions searched, nine very red sources, each with a probability of less than 0.01 of being a random field star, were found. Most of the nine sources are characterized by deep silicate absorption features at 10 microns and a red energy distribution that continues to rise beyond 25 microns. Six of the sources are best explained as late O or early B stars exciting a compact H II region. The radio emission is close to that expected for the rate of emission of ionizing photons for a normal main-sequence star. Although these H II regions are compact, they are not sufficiently dusty in the immediate environment of the star to significantly reduce the ionizing flux. Three of the sources show considerably more emission than expected for a main-sequence star, indicating they are either hotter than a main-sequence star with the same luminosity or the radio emision is nonthermal and coming from a more exotic object.

  9. VizieR Online Data Catalog: Optically Bright extragalactic Radio Sources II (Petrov, 2013)

    NASA Astrophysics Data System (ADS)

    Petrov, L.

    2014-06-01

    The first VLBI (Very Long Baseline Interferometry) observing campaign in 2007 resulted in the detection of 398 targets with the European VLBI Network (EVN; Bourda et al., 2010, cat. J/A+A/520/A113). During the second observing campaign, a subset of 105 sources detected in the previous campaign was observed (Bourda et al., 2011, cat. J/A+A/526/A102). Their positions were derived by Petrov (2011, cat. J/AJ/142/105) and formed the OBRS-1 (Optically Bright extragalactic Radio Sources) catalog. The remaining sources were observed in the third campaign, called OBRS-2. During the OBRS-2 campaign, there were three observing sessions with 10 VLBA (Very Long Baseline Array) stations and 5-6 EVN stations from this list: EFLSBERG, MEDICINA, ONSALA60, YEBES40M, DSS63, HARTRAO, and NOTO. Observations were made on 2010 Mar 23 (session ID gc034a), on 2011 Nov 8 (gc034bcd), and on 2011 Mar 15 (gc034ef). The OBRS-2 catalog presents precise positions of the 295 extragalactic radio sources as well as median correlated flux densities at 8.4 and 2.2GHz at baseline lengths shorter than 900km and at baseline lengths longer than 5000km. (1 data file).

  10. A comparison between accurate radio and optical positions for six Southern Hemisphere extragalactic sources

    NASA Astrophysics Data System (ADS)

    Jauncey, David L.; White, Graeme L.; Preston, Robert A.; Niell, Arthur E.; Harvey, Bruce R.; Morabito, David D.; Meier, David L.; Slade, Martin A.; Stolz, Artur; Tzioumis, Anastasios K.

    1989-07-01

    Radio positions measured on a 275 km baseline are given for six extragalactic sources south of declination -45°. The measurements were made using very long baseline interferometry (VLBI) at 2.3 and 8.4 GHz between the 64 m antennas at Parkes and Tidbinbilla, Australia. Positions with accuracies of ±0.11 arcsec in right ascension and ±0.08 arcsec in declination are given with respect to the JPL VLBI reference frame. This program is a first step in establishing an accurate radio reference frame in the mid-latitude to polar regions of the southern hemisphere. Accurate optical positions have also been determined from glass plate copies of the ESO B Schmidt atlas using reference stars from the Perth 70 catalog. A comparison between the optical and radio positions yields mean differences (optical - radio) of -0.02 ± 0.09 and 0.05 ± 0.13 arcsec in right ascension and declination, respectively. On average, the optical reference frame south of -45°, the FK4 as defined by the Perth 70 catalog, and the VLBI radio reference frame as defined by the present six sources, appear to be consistent at the tenth of an arcsecond level.

  11. Interstellar scattering of compact radio sources near supernova remnants

    NASA Technical Reports Server (NTRS)

    Spangler, S. R.; Mutel, R. L.; Benson, J. M.; Cordes, J. M.

    1986-01-01

    A multifrequency VLBI search for interstellar scattering of extragalactic radio sources near supernova remnants is reported. VLBI observations at 610, 1663, and 4991 MHz were made of compact sources near the supernova remnants CTA 1, G33.6 + 0.1, G74.9 + 1.2, and HB 21, and 610 MHz observations were also made of a source near HB 9. These observations were motivated by the possibility of enhanced cosmic ray-induced turbulence in front of supernova remnants, as expected in 'diffusive' theories of shock wave acceleration. Angular broadening is definitely seen in the case of the source 2013 + 370, which lies within 4 arcmin of the supernova remnant G74.9 + 1.2. Present observations cannot unambiguously attribute the scattering material to the supernova remnant, as the line of sight also passes through the Cygnus OB1 association. The source 1849 + 005 appears to be highly scattered, as fringes were not detected even on short baselines at 5 GHz. This result may be due to the low galactic longitude of this source rather than its proximity to the supernova remnant G 33.6 + 0.1. Broadening was not detected for sources whose lines of sight pass close to the supernova remnants HB 9, HB 21, and CTA 1.

  12. Compact radio sources in luminous infrared galaxies

    NASA Astrophysics Data System (ADS)

    Parra, Rodrigo

    2007-08-01

    Radio interferometry is an observational technique of high sensitivity and incomparably high spatial resolution. Moreover, because radio waves can freely propagate through interstellar dust and gas, it allows the study of regions of the universe completely obscured at other wavelengths. This thesis reports the observational and theoretical results of my research during the past four years which are mostly based on interferometric radio data. The COLA sample is an infrared selected sample of active star forming galaxies. We conducted 6 cm VLA and VLBI snapshot observations of the northern half of this sample. The radio emission seen at VLA scales is consistent with being powered by star formation activity because it follows the far infrared to radio correlation. We detect 22% of the sample sources in our VLBI snapshots. Based on luminosity arguments, we argue that these sub-parsec VLBI sources are powered by AGN activity. Furthermore, we find that VLBI detections are preferentially found in sources whose VLA scale structures have the highest peak brightnesses suggesting a strong correlation between compact starburst and AGN activity. This observational result is consistent with the theoretical picture of an Eddington-limited nuclear starburst acting as the last valve in the pipeline transporting the gas from kiloparsec scales onto the accretion disc of a buried AGN. Arp 220 is the archetypical ultra luminous infrared galaxy. For many years this source has been known to harbour a compact (~100 pc) cluster of unresolved 18 cm bright sources believed to be bright core collapse supernovae. Using multiwavelength VLBI observations, we obtained for the first time radio spectra for 18 of these sources. We find that over a half of them have spectra consistent with young supernovae. The rest can be better explained as older supernova remnants interacting with the high density starburst ISM. This finding allowed us to constrain the number of possible scenarios for the Arp 220

  13. FUELING LOBES OF RADIO GALAXIES: STATISTICAL PARTICLE ACCELERATION AND THE EXTRAGALACTIC {gamma}-RAY BACKGROUND

    SciTech Connect

    Massaro, F.; Ajello, M.

    2011-03-01

    The recent discovery of the {gamma}-ray emission from the lobes of the closest radio galaxy Centaurus A by Fermi implies the presence of high-energy electrons at least up to {gamma} {approx} 10{sup 5}-10{sup 6}. These high-energy electrons are required to interpret the observed {gamma}-ray radiation in terms of inverse Compton emission off the cosmic microwave background (IC/CMB), the widely accepted scenario to describe the X-ray emission of radio galaxy lobes. In this Letter, we consider the giant radio lobes of FR II radio galaxies showing that it is possible to maintain electrons at energies {gamma} {approx} 10{sup 5}-10{sup 6}, assuming an acceleration scenario (driven by turbulent magnetic fields) that compensates radiative losses. In addition, we consider the contribution to the diffuse extragalactic {gamma}-ray background due to the IC/CMB emission of FR IIs' lobes, showing its relevance in the keV to MeV energy range.

  14. X-ray, Optical and Radio Observations of the Extragalactic Superbubble N7793-S26

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas; Schlegel, E. M.; Filipovic, M. D.; Crawford, E.; Payne, J.; Grimes, C. K.

    2012-01-01

    We present a multi-wavelength (X-ray, optical and radio) spatial and spectral analysis of the extragalactic superbubble N7793-S26. Prior observations and analysis of this source had revealed extended emission spanning nearly 400 parsecs at all three wavelength domains: the extended morphology of this object suggests a superbubble classification, prompting the argument that N7793-S26 is actually a microquasar. We investigate the microquasar interpretation of this source based on analysis of its spatial and spectral properties and compare N7793-S26 to another known extragalactic superbubble located in the Local Group Galaxy IC 10. We investigate the scenario that the soft X-ray sources seen at the northern and southern edges of N7793-S26 are actually supernova remnants and that the central hard X-ray source is an X-ray binary serendipitously located to give the appearance of a central engine with two jets. This scenario will be presented and discussed.

  15. The many facets of extragalactic radio surveys: towards new scientific challenges

    NASA Astrophysics Data System (ADS)

    2015-10-01

    Radio continuum surveys are a powerful tool to detect large number of objects over a wide range of redshifts and obtain information on the intensity, polarization and distribution properties of radio sources across the sky. They are essential to answer to fundamental questions of modern astrophysics. Radio astronomy is in the midst of a transformation. Developments in high-speed digital signal processing and broad-band optical fibre links between antennas have enabled significant upgrades of the existing radio facilities (e-MERLIN, JVLA, ATCA-CABB, eEVN, APERTIF), and are leading to next-generation radio telescopes (LOFAR, MWA, ASKAP, MeerKAT). All these efforts will ultimately lead to the realization of the Square Kilometre Array (SKA), which, owing to advances in sensitivity, field-of-view, frequency range and spectral resolution, will yield transformational science in many astrophysical research fields. The purpose of this meeting is to explore new scientific perspectives offered by modern radio surveys, focusing on synergies allowed by multi-frequency, multi-resolution observations. We will bring together researchers working on wide aspects of the physics and evolution of extra-galactic radio sources, from star-forming galaxies to AGNs and clusters of galaxies, including their role as cosmological probes. The organization of this conference has been inspired by the recent celebration of the 50th anniversary of the Northern Cross Radio Telescope in Medicina (BO), whose pioneering B2 and B3 surveys provided a significant contribution to radio astronomical studies for many decades afterwards. The conference was organized by the Istituto di Radioastronomia (INAF), and was held at the CNR Research Area in Bologna, on 20-23 October 2015. This Conference has received support from the following bodies and funding agencies: National Institute for Astrophysics (INAF), ASTRON, RadioNet3 (through the European Union’s Seventh Framework Programme for research

  16. The ICRF realisations: the WGRF combination solution versus the GAOUA catalogues of positions of extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Molotaj, O.; Tel'Nyuk-Adamchuk, V.; Yatskiv, Ya.

    The GAOUA series of compiled catalogues of extragalactic radio source (ERS) posistions based on initial ones is being constructed using the Kyiv arc length method. On the basis of a comparison of these catalogues with the ICRF two methods of combination of initial catalogues of ERS positions are discussed.

  17. Magnetic Bubble Expansion as an Experimental Model for Extra-Galactic Radio Lobes

    NASA Astrophysics Data System (ADS)

    Lynn, Alan; Zhang, Yue; Hsu, Scott

    2010-11-01

    The Plasma Bubble Expansion Experiment (PBEX) is conducting laboratory experiments to address outstanding nonlinear plasma physics issues related to how magnetic energy and helicity carried by extra-galactic jets interacts with the intergalactic medium to form radio lobe structures. Experiments are being conducted in the 4 meter long, 50 cm diameter HELCAT linear plasma device at UNM. A pulsed magnetized coaxial gun (˜10 kV, ˜100 kA, ˜2 mWb) forms and injects magnetized plasma bubbles perpendicularly into a lower pressure weakly magnetized background plasma formed by a helicon and/or hot cathode source in HELCAT. Ideal MHD simulations show that an MHD shock develops ahead of the bubble as it propagates, and that the bubble develops asymmetries due to the background field [1]. Experimental data from plasma bubble injection into a background plasma, particularly magnetic probe measurements, will be discussed. [4pt] [1] W. Liu et al., Phys. Plasmas 15, 072905 (2008).

  18. JPL 1990-3: A 5-nrad extragalactic source catalog based on combined radio interferometric observations

    NASA Technical Reports Server (NTRS)

    Sovers, O. J.

    1991-01-01

    A combined analysis merges 17,000 Deep Space Network (DSN) Very Long Baseline Interferometric (VLBI) observations with 303,000 observations from the Crustal Dynamics Project (CDP) and the International Radio Interferometric Surveying (IRIS) project. Observations from the Radio Reference Frame Development (RRFD) and Time and Earth Motion Precision Observations (TEMPO) programs through late 1990 form the DSN VLBI data set. The combined analysis yields angular coordinates of extragalactic radio sources with a precision of a few nanoradians, as compared with 5 to 10 nrad precision for coordinates derived in the past solely from DSN data. The improvement in the combined analysis is due to the new Mark III DSN data, as well as to increased statistical strength from the large volume of observations from non-DSN experiments. Such a unified analysis is made possible by recent improvements in parameter estimation software efficiency. The terrestrial reference frame is based on joint VLBI experiments using both DSN and CDP antennas, and on specifying the coordinates of VLBI antennas in a proper geocentric coordinate system by means of Global Positioning System (GPS) collocation of VLBI, LLR, and SLR (Laser Ranging) sites.

  19. On the Connection of the Apparent Proper Motion and the VLBI Structure of Compact Radio Sources

    NASA Astrophysics Data System (ADS)

    Moór, A.; Frey, S.; Lambert, S. B.; Titov, O. A.; Bakos, J.

    2011-06-01

    Many of the compact extragalactic radio sources that are used as fiducial points to define the celestial reference frame are known to have proper motions detectable with long-term geodetic/astrometric very long baseline interferometry (VLBI) measurements. These changes can be as high as several hundred microarcseconds per year for certain objects. When imaged with VLBI at milliarcsecond (mas) angular resolution, these sources (radio-loud active galactic nuclei) typically show structures dominated by a compact, often unresolved "core" and a one-sided "jet." The positional instability of compact radio sources is believed to be connected with changes in their brightness distribution structure. For the first time, we test this assumption in a statistical sense on a large sample rather than on only individual objects. We investigate a sample of 62 radio sources for which reliable long-term time series of astrometric positions as well as detailed 8 GHz VLBI brightness distribution models are available. We compare the characteristic direction of their extended jet structure and the direction of their apparent proper motion. We present our data and analysis method, and conclude that there is indeed a correlation between the two characteristic directions. However, there are cases where the ~1-10 mas scale VLBI jet directions are significantly misaligned with respect to the apparent proper motion direction.

  20. VizieR Online Data Catalog: Extragalactic Radio Source Identifications (Veron-Cetty+ 1983)

    NASA Astrophysics Data System (ADS)

    Veron-Cetty, M.-P.; Veron, P.

    1996-05-01

    The catalog is a compilation of all published optical identifications of extragalactic radio sources. This machine-readable version is an updated and greatly expanded edition of the original published one; this version contains 14585 identifications and citations to 917 papers. The data file contains most commonly used source name, number in the 4C catalog Gower et al. (1967), and Pilkington and Scott (1965) if applicable, right ascension and declination (equinox B1950.0), magnitude estimate for the identification type of optical object, identification reference, alternate name for identified object (if known), confirmation or invalidation code and associated reference, finding chart existence (or nonexistence), redshift, and reference for the spectrum. A reference file contains the references ordered by number cited in the catalog and alphabetically by author. Completeness has been attempted for all papers published through the end of 1982. The present version contains fewer references than the 1974 version (which had 935) because certain numbers were unused in the previous edition and because certain references are no longer used in the 1983 version and were removed. The authors have prepared this final version and have discontinued future updates. (2 data files).

  1. Study of interstellar molecular clouds using formaldehyde absorption toward extragalactic radio sources

    SciTech Connect

    Araya, E. D.; Andreev, N.; Dieter-Conklin, N.; Goss, W. M.

    2014-04-01

    We present new Very Large Array 6 cm H{sub 2}CO observations toward four extragalactic radio continuum sources (B0212+735, 3C 111, NRAO 150, and BL Lac) to explore the structure of foreground Galactic clouds as revealed by absorption variability. This project adds a new epoch in the monitoring observations of the sources reported by Marscher and collaborators in the mid-1990s. Our new observations confirm the monotonic increase in H{sub 2}CO absorption strength toward NRAO 150. We do not detect significant variability of our 2009 spectra with respect to the 1994 spectra of 3C111, B0212+735, and BL Lac; however, we find significant variability of the 3C111 2009 spectrum with respect to archive observations conducted in 1991 and 1992. Our analysis supports that changes in absorption lines could be caused by chemical and/or geometrical gradients in the foreground clouds and not necessarily by small-scale (∼10 AU) high-density molecular clumps within the clouds.

  2. Double layers and plasma-wave resistivity in extragalactic jets - Cavity formation and radio-wave emission

    NASA Technical Reports Server (NTRS)

    Borovsky, Joseph E.

    1987-01-01

    Current driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur in extragalactic jets for estimated values of the carried currents. Strong plasma double layers, however, may exist within self-maintained density cavities. The relativistic double-layer-emitted electron and ion beams drive plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

  3. Double layers and plasma-wave resistivity in extragalactic jets: Cavity formation and radio-wave emission

    NASA Technical Reports Server (NTRS)

    Borovsky, Joseph E.

    1987-01-01

    For estimated values of the currents carried by extragalactic jets, current-driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur. Strong plasma double layers, however, may exist within self-maintained density cavities, the relativistic double-layer-emitted electron, and ion beams driving plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

  4. Determination of the extragalactic-planetary frame tie from joint analysis of radio interferometric and lunar laser ranging measurements

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; Charlot, P.; Finger, M. H.; Williams, J. G.; Sovers, O. J.; Newhall, XX; Standish, E. M., Jr.

    1994-01-01

    Very Long Baseline Interferometry (VLBI) observations of extragalactic radio sources provide the basis for defining an accurate non-rotating reference frame in terms of angular positions of the sources. Measurements of the distance from the Earth to the Moon and to the inner planets provide the basis for defining an inertial planetary ephemeris reference frame. The relative orientation, or frame tie, between these two reference frames is of interest for combining Earth orientation measurements, for comparing Earth orientation results with theories referred to the mean equator and equinox, and for determining the positions of the planets with respect to the extragalactic reference frame. This work presents an indirect determination of the extragalactic-planetary frame tie from a combined reduction of VLBI and Lunar Laser Ranging (LLR) observations. For this determination, data acquired by LLR tracking stations since 1969 have been analyzed and combined with 14 years of VLBI data acquired by NASA's Deep Space Network since 1978. The frame tie derived from this joint analysis, with an accuracy of 0.003 sec, is the most accurate determination obtained so far. This result, combined with a determination of the mean ecliptic (defined in the rotating sense), shows that the mean equinox of epoch J2000 is offset from the x-axis of the extragalactic frame adopted by the International Earth Rotation Service for astrometric and geodetic applications by 0.078 sec +/- 0.010 sec along the y-direction and y 0.019 sec +/- 0.001 sec. along the z-direction.

  5. Radio Structures of Compact Quasars with Broad Absorption Lines

    NASA Astrophysics Data System (ADS)

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  6. Acceleration of Compact Radio Jets on Sub-parsec Scales

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Sung; Lobanov, Andrei P.; Krichbaum, Thomas P.; Zensus, J. Anton

    2016-08-01

    Jets of compact radio sources are highly relativistic and Doppler boosted, making studies of their intrinsic properties difficult. Observed brightness temperatures can be used to study the intrinsic physical properties of relativistic jets, and constrain models of jet formation in the inner jet region. We aim to observationally test such inner jet models. The very long baseline interferometry (VLBI) cores of compact radio sources are optically thick at a given frequency. The distance of the core from the central engine is inversely proportional to the frequency. Under the equipartition condition between the magnetic field energy and particle energy densities, the absolute distance of the VLBI core can be predicted. We compiled the brightness temperatures of VLBI cores at various radio frequencies of 2, 8, 15, and 86 GHz. We derive the brightness temperature on sub-parsec scales in the rest frame of the compact radio sources. We find that the brightness temperature increases with increasing distance from the central engine, indicating that the intrinsic jet speed (the Lorentz factor) increases along the jet. This implies that the jets are accelerated in the (sub-)parsec regions from the central engine.

  7. Compact radio sources in the starburst galaxy M82 and the Sigma-D relation for supernova remnants

    NASA Technical Reports Server (NTRS)

    Huang, Z. P.; Thuan, T. X.; Chevalier, R. A.; Condon, J. J.; Yin, Q. F.

    1994-01-01

    We have obtained an 8.4 GHz Very Large Array (VLA) A-array map of the starburst galaxy M82 with a resolution Full Width at Half Maximum (FWHM) approximately 0.182 sec. About 50 compact radio sources in the central region of M82 were detected with a peak surface brightness approximately greater than 10(exp -17) W/Hz/sq m/sr. Comparison with previous observations shows that most sources are declining in flux. Three previously visible sources have faded into the background of our map (approximately less than 0.2 mJy/beam), while a few sources, including the second and third brightest radio sources in M82, may have increased slightly in flux over the last decade. No new radio supernova was found. The birth rate of the compact radio sources is estimated to be 0.11 + or - 0.05/yr. We attribute the population of such bright, small supernova remnants (SNRs) in M82 to the high pressure in the central region that can truncate the mass loss during a red supergiant phase or allow dense ionized clouds to be present. The compact radio sources obey a Sigma(radio surface brightness) - D(diameter) relation which is remarkably similar to that followed by supernova remnants in the Galaxy and the Magellanic Clouds and by two of the strongest known extragalactic radio supernovae: SN 1986J and SN 1979C. A least-squares fit to the SNR data gives: Sigma(sub 8.4 GHz) (W/Hz/sq m/sr) = 4.4 x 10(exp -16) D(sub pc)(exp -3.5 +/- 0.1) covering seven orders of magnitude in Sigma. Possible selection effects are discussed and a theoretical discussion of the correlation is presented.

  8. Relativistic blast-wave model for the rapid flux variations of AO 0235+164 and other compact radio sources

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.

    1978-01-01

    A relativistic blast-wave version of a signal-screen model is developed which can adequately explain the details of the flux-density and structural variations of compact extragalactic radio sources. The relativistic motion implied by flux variations is analyzed with respect to the synchrotron spectrum of the BL Lac object AO 0235+164 observed during outbursts, and a signal-screen model for rapidly expanding shells produced by ultrarelativistic blast waves is examined. The approximate observed structure of the blast wave at three stages in its evolution is illustrated, each stage is described, and the model is applied to the flux density outburst in AO 0235+164 observed in late 1975. The results show that a relativistic blast-wave model can in general reproduce the main features of the observed flux variations in compact sources. Some problems with the proposed model are briefly discussed.

  9. UNVEILING EXTRAGALACTIC STAR FORMATION USING RADIO RECOMBINATION LINES: AN EXPANDED VERY LARGE ARRAY PILOT STUDY WITH NGC 253

    SciTech Connect

    Kepley, Amanda A.; Johnson, Kelsey E.; Chomiuk, Laura; Balser, Dana S.; Goss, W. M.; Pisano, D. J. E-mail: kej7a@virginia.edu E-mail: dbalser@nrao.edu E-mail: DJPisano@mail.wvu.edu

    2011-09-20

    Radio recombination lines (RRLs) are powerful, extinction-free diagnostics of the ionized gas in young, star-forming regions. Unfortunately, these lines are difficult to detect in external galaxies. We present the results of Expanded Very Large Array (EVLA) observations of the RRL and radio continuum emission at 33 GHz from NGC 253, a nearby nuclear starburst galaxy. We detect the previously unobserved H58{alpha} and H59{alpha} RRLs and make simultaneous sensitive measurements of the continuum. We measure integrated line fluxes of 44.3 {+-} 0.7 W m{sup -2} and 39.9 {+-} 0.8 W m{sup -2} for the H58{alpha} and H59{alpha} lines, respectively. The thermal gas in NGC 253 is kinematically complex with multiple velocity components. We constrain the density of the thermal gas to (1.4-4) x 10{sup 4} cm{sup -3} and estimate an ionizing photon flux of 1 x 10{sup 53} s{sup -1}. We use the RRL kinematics and the derived ionizing photon flux to show that the nuclear region of NGC 253 is not gravitationally bound, which is consistent with the outflow of gas inferred from the X-ray and H{alpha} measurements. The line profiles, fluxes, and kinematics of the H58{alpha} and H59{alpha} lines agree with those of RRLs at different frequencies confirming the accuracy of the previous, more difficult, high-frequency observations. We find that the EVLA is an order of magnitude more efficient for extragalactic RRL observations than the Very Large Array. These observations demonstrate both the power of the EVLA and the future potential of extragalactic RRL studies with the EVLA.

  10. Scorpius X-1: The Evolution and Nature of the Twin Compact Radio Lobes

    NASA Astrophysics Data System (ADS)

    Fomalont, E. B.; Geldzahler, B. J.; Bradshaw, C. F.

    2001-09-01

    The motion and variability of the radio components in the low-mass X-ray binary system Sco X-1 have been monitored with extensive VLBI imaging at 1.7 and 5.0 GHz over 4 yr, including a 56 hr continuous VLBI observation in 1999 June. We detect one strong and one weak compact radio component, moving in opposite directions from the radio core. Their relative motion and flux densities are consistent with relativistic effects, from which we derive an average component speed of v/c=0.45+/-0.03 at an angle of 44deg+/-6deg to the line of sight. This inclination of the binary orbit suggests a mass of the secondary star that is less than 0.9 Msolar, assuming a neutron star mass of 1.4 Msolar. We suggest that the two moving radio components consist of ultrarelativistic plasma that is produced at a working surface where the energy in dual-opposing beams disrupt. The radio lobe advance velocity is constant over many hours, but differs among lobe-pairs: 0.32c, 0.46c, 0.48c, and 0.57c. A lobe-pair lifetime is less than 2 days, with a new pair formed near the core within a day. The lobe flux has flux density that is variable over a timescale of 1 hr, has a measured minimum size of 1 mas (4×108 km), and is extended perpendicular to its motion. This timescale and size are consistent with an electron radiative lifetime of less than 1 hr. Such a short lifetime can be caused by synchrotron losses if the lobe magnetic field is 300 G or by adiabatic expansion of the electrons as soon as they are produced at the working surface. The lobes also show periods of slow expansion and a steepening radio spectrum. Two of the core flares are correlated with the lobe flares under the assumption that the flares are produced by an energy burst traveling down the beams with a speed greater than 0.95. The radio morphology for Sco X-1 differs from most other Galactic jet sources. Possible reasons for the morphology difference are that Sco X-1 is associated with a neutron star, it is a persistent X

  11. New method for determining the distances to certain extragalactic radio sources

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.

    1980-01-01

    The structural evolution of variable radio sources is examined in the Hedgehog model. It is shown that the time evolution of the angular separation of two components is described by the ellipse equation.

  12. Radio and gamma-ray properties of extragalactic jets from the TANAMI sample

    NASA Astrophysics Data System (ADS)

    Böck, M.; Kadler, M.; Müller, C.; Tosti, G.; Ojha, R.; Wilms, J.; Bastieri, D.; Burnett, T.; Carpenter, B.; Cavazzuti, E.; Dutka, M.; Blanchard, J.; Edwards, P. G.; Hase, H.; Horiuchi, S.; Jauncey, D. L.; Krauß, F.; Lister, M. L.; Lovell, J. E. J.; Lott, B.; Murphy, D. W.; Phillips, C.; Plötz, C.; Pursimo, T.; Quick, J.; Ros, E.; Taylor, G.; Thompson, D. J.; Tingay, S. J.; Tzioumis, A.; Zensus, J. A.

    2016-05-01

    The TANAMI program has been observing parsec-scale radio jets of southern (declination south of - 30°) γ-ray bright AGN, simultaneously with Fermi/LAT monitoring of their γ-ray emission, via high-resolution radio imaging with Very Long Baseline Interferometry techniques. We present the radio and γ-rayproperties of the TANAMI sources based on one year of contemporaneous TANAMI and Fermi/LAT data. A large fraction (72%) of the TANAMI sample can be associated with bright γ-ray sources for this time range. Association rates differ for different optical classes with all BL Lacs, 76% of quasars, and just 17% of galaxies detected by the LAT. Upper limits were established on the γ-ray flux from TANAMI sources not detected by LAT. This analysis led to the identification of three new Fermi sources whose detection was later confirmed. The γ-ray and radio luminosities are related by Lγ ∝ Lr0.89±0.04. The brightness temperatures of the radio cores increase with the average γ-ray luminosity and the presence of brightness temperatures above the inverse Compton limit implies strong Doppler boosting in those sources. The undetected sources have lower γ/radio luminosity ratios and lower contemporaneous brightness temperatures. Unless the Fermi/LAT-undetected blazars are much γ-ray-fainter than the Fermi/LAT-detected sources, their γ-ray luminosity should not be significantly lower than the upper limits calculated here.

  13. Witnessing the Gradual Slowdown of Powerful Extragalactic Jets: The X-Ray-Optical-Radio Connection

    NASA Technical Reports Server (NTRS)

    Georganopoulos, Markos; Kazanas, Demosthenes

    2004-01-01

    A puzzling feature of the Chandra-detected quasar jets is that their X-ray emission decreases faster along the jet than their radio emission, resulting from an outward-increasing radio-to-X-ray ratio. In some sources this behavior is so extreme that the radio emission peak is located clearly downstream of that of the X-rays. This is a rather unanticipated behavior given that the inverse Compton nature of the X-rays and the synchrotron radio emission are attributed to roughly the same electrons of the jet's nonthermal electron distribution. In this letter we show that this morphological behavior can result from the gradual deceleration of a relativistic flow and that the offsets in peak emission at different wavelengths carry the imprint of this deceleration. This notion is consistent with another recent finding, namely, that the jets feeding the terminal hot spots of powerful radio galaxies and quasars are still relativistic with Lorentz factors GAMMA approximately 2-3. The picture of the kinematics of powerful jets emerging from these considerations is that they remain relativistic as they gradually decelerate from kiloparsec scales to the hot spots, where, in a final collision with the intergalactic medium, they slow down rapidly to the subrelativistic velocities of the hot spot advance speed.

  14. Lensing of Fast Radio Bursts as a Probe of Compact Dark Matter.

    PubMed

    Muñoz, Julian B; Kovetz, Ely D; Dai, Liang; Kamionkowski, Marc

    2016-08-26

    The possibility that part of the dark matter is made of massive compact halo objects (MACHOs) remains poorly constrained over a wide range of masses, and especially in the 20-100  M_{⊙} window. We show that strong gravitational lensing of extragalactic fast radio bursts (FRBs) by MACHOs of masses larger than ∼20  M_{⊙} would result in repeated FRBs with an observable time delay. Strong lensing of a FRB by a lens of mass M_{L} induces two images, separated by a typical time delay ∼few×(M_{L}/30  M_{⊙})  msec. Considering the expected FRB detection rate by upcoming experiments, such as canadian hydrogen intensity mapping experiment (CHIME), of 10^{4} FRBs per year, we should observe from tens to hundreds of repeated bursts yearly, if MACHOs in this window make up all the dark matter. A null search for echoes with just 10^{4} FRBs would constrain the fraction f_{DM} of dark matter in MACHOs to f_{DM}≲0.08 for M_{L}≳20  M_{⊙}. PMID:27610840

  15. Global VLBI Observations of Weak Extragalactic Radio Sources: Imaging Candidates to Align the VLBI and Gaia Frames

    NASA Technical Reports Server (NTRS)

    Bourda, Geraldine; Collioud, Arnaud; Charlot, Patrick; Porcas, Richard; Garrington, Simon

    2010-01-01

    The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames (International Celestial Reference Frame) with the highest accuracy. In this respect, it is found that only 10% of the ICRF sources are suitable to establish this link (70 sources), either because most of the ICRF sources are not bright enough at optical wavelengths or because they show extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the situation, we initiated a multi-step VLBI observational project, dedicated to finding additional suitable radio sources for aligning the two frames. The sample consists of about 450 optically-bright radio sources, typically 20 times weaker than the ICRF sources, which have been selected by cross-correlating optical and radio catalogs. The initial observations, aimed at checking whether these sources are detectable with VLBI, and conducted with the European VLBI Network (EVN) in 2007, showed an excellent 90% detection rate. This paper reports on global VLBI observations carried out in March 2008 to image 105 from the 398 previously detected sources. All sources were successfully imaged, revealing compact VLBI structure for about half of them, which is very promising for the future.

  16. X-ray spectra of a complete sample of extragalactic core-dominated radio sources

    NASA Technical Reports Server (NTRS)

    Brunner, H.; Lamer, G.; Worrall, D. M.; Staubert, R.

    1994-01-01

    We present ROSAT soft X-ray spectra for the members of a complete sample of 13 core-dominated, flat radio spectrum sources. The sample comprises all radio sources from a flux-limited radio catalog (S(sub 5GHz) greater than 1 Jy; Kuehr et al. 1981) which are north of delta = 70 deg, at galactic latitudes b greater than 10 deg, and have a flat radio spectrum between 1.4 and 5 GHz (alpha(sub r) less than 0.5; f approximately nu(sup -alpha)). The sources have already undergone much study at radio and optical wavelengths and are classified in broad terms as quasars (8 sources) and BL Lac objects (5 sources). We find mean X-ray power-law energy indices of alpha(sub x) = 0.59 +/- 0.19 for the quasars and 1.36 +/- 0.27 for the BL Lac objects (68% confidence range for two parameters of interest as determined by a maximum likelihood method), supporting earlier Einstein Observatory results for heterogeneous samples of sources (Worrall & Wilkes 1990). A non-zero dispersion on alpha(sub x) is found for both the quasars and the BL Lac objects. When we incorporate published radio, mm, and optical measurements and compare the X-ray and broad-band spectral indices alpha(sub x), alpha(sub rx), alpha(sub mm,x), and alpha(sub ox), the most obvious difference between the quasar and BL Lac subsamples lies within the X-ray band. We have fitted the multi-wavelength data to inhomogeneous synchotron-self-Compton models and find that, for the BL Lac objects with steep X-ray spectra, synchotron emission can account for the radio to soft X-ray measurements, whereas the BL Lac objects with hard X-ray spectra and the quasars require significant Compton emission to model the spectral flattening indicated by alpha(sub x) less than alpha(sub ox).

  17. Low Power Compact Radio Galaxies at High Angular Resolution

    SciTech Connect

    Giroletti, Marcello; Giovannini, G.; Taylor, G.B.; /KIPAC, Menlo Park /NRAO, Socorro

    2005-06-30

    We present sub-arcsecond resolution multi-frequency (8 and 22 GHz) VLA images of five low power compact (LPC) radio sources, and phase referenced VLBA images at 1.6 GHz of their nuclear regions. At the VLA resolution we resolve the structure and identify component positions and flux densities. The phase referenced VLBA data at 1.6 GHz reveals flat-spectrum, compact cores (down to a few milliJansky) in four of the five sources. The absolute astrometry provided by the phase referencing allows us to identify the center of activity on the VLA images. Moreover, these data reveal rich structures, including two-sided jets and secondary components. On the basis of the arcsecond scale structures and of the nuclear properties, we rule out the presence of strong relativistic effects in our LPCs, which must be intrinsically small (deprojected linear sizes {approx}< 10 kpc). Fits of continuous injection models reveal break frequencies in the GHz domain, and ages in the range 10{sup 5}-10{sup 7} yrs. In LPCs, the outermost edge may be advancing more slowly than in more powerful sources or could even be stationary; some LPCs might also have ceased their activity. In general, the properties of LPCs can be related to a number of reasons, including, but not limited to: youth, frustration, low kinematic power jets, and short-lived activity in the radio.

  18. Compact Superconducting Radio-frequency Accelerators and Innovative RF Systems

    SciTech Connect

    Kephart, Robert; Chattopadhyay, Swaapan; Milton, Stephen

    2015-04-10

    We will present several new technical and design breakthroughs that enable the creation of a new class of compact linear electron accelerators for industrial purposes. Use of Superconducting Radio-Frequency (SRF) cavities allow accelerators less than 1.5 M in length to create electron beams beyond 10 MeV and with average beam powers measured in 10’s of KW. These machines can have the capability to vary the output energy dynamically to produce brehmstrahlung x-rays of varying spectral coverage for applications such as rapid scanning of moving cargo for security purposes. Such compact accelerators will also be cost effective for many existing and new industrial applications. Examples include radiation crosslinking of plastics and rubbers, creation of pure materials with surface properties radically altered from the bulk, modification of bulk or surface optical properties of materials, sterilization of medical instruments animal solid or liquid waste, and destruction of organic compounds in industrial waste water effluents. Small enough to be located on a mobile platform, such accelerators will enable new remediation methods for chemical and biological spills and/or in-situ crosslinking of materials. We will describe one current design under development at Fermilab including plans for prototype and value-engineering to reduce costs. We will also describe development of new nano-structured field-emitter arrays as sources of electrons, new methods for fabricating and cooling superconducting RF cavities, and a new novel RF power source based on magnetrons with full phase and amplitude control.

  19. Extragalactic Radio Astronomy from an Armchair: Continuum Spectral Shapes of 150 Faint Sources

    NASA Astrophysics Data System (ADS)

    Gonzalez-Perez, J. N.; Andernach, H.

    1994-08-01

    We have used all available radio-source surveys to construct the continuum spectra for sources in an area of 5 by 10 degrees near the North Ecliptic Pole (NEP), previously observed at 2.7 GHz with the Effelsberg telescope. Most of the surveys are of similar angular resolution (~3 to 5 arcmin) and cover a wide range of frequencies from 38 MHz to 5 GHz. We have developed a cross-identification algorithm that takes into account the dependence of source structure on observing frequency. This improved the number of true matches between the source catalogues. Spectra for 229 sources with flux measurements at two or more frequencies were constructed. For 124 of these we found data at four or more frequencies, allowing us to classify their spectral shape. In our rather faint sample (S_2.7GHz > 20 mJy) we find the fraction of sources with spectral curvature to be much lower than in samples of stronger sources previously studied by other authors. Preliminary optical identifications are being drawn from the digitized versions of the first Palomar Sky Survey prepared at STScI.

  20. Using Space Telescope to tie the HIPPARCOS and extragalactic reference frames together

    NASA Technical Reports Server (NTRS)

    Hemenway, P. D.; Duncombe, R. L.; Jefferys, W. H.; Shelus, P. J.

    1985-01-01

    Hubble Space Telescope observations will be made to tie the HIPPARCOS Instrumental System (HIS) to extragalactic objects, to determine the overall rotation of the HIS with respect to a set of extragalactic objects; to compare the HIS to an accurate radio reference frame; and to look for motions in the optical centroids of compact extragalactic objects at the level of 0.001 arcseconds per year. About 75 radio sources and extragalactic objects will be chosen from the initial group of 414 pairs. The egos will have their positions and proper motions determined relative to the HIPPARCOS Input Catalog stars. The candidate stars are being screened by ground based speckle interferometry to select a final set.

  1. Extragalactic continuum sources.

    NASA Astrophysics Data System (ADS)

    Valtaoja, E.

    1989-09-01

    As with most other high-frequency radio telescopes, continuum work occupies only a small fraction - currently about 5% - of SEST's total time. The importance of these observations in increasing our understanding of quasars and other extragalactic sources is, however, large.

  2. Morphology of high-luminosity compact radio sources.

    PubMed

    Zensus, J A; Krichbaum, T P; Lobanov, A P

    1995-12-01

    High-dynamic range imaging and monitoring with very-long-baseline interferometry reveal a rich morphology of luminous flat-spectrum radio sources. One-sided core-jet structures abound, and superluminal motion is frequently measured. In a few cases, both distinct moving features and diffuse underlying jet emission can be detected. Superluminal motion seen in such sources is typically complex, on curved trajectories or ridge lines, and with variable component velocities, including stationary features. The curved trajectories seen can be modeled by helical motion within the underlying jet flow. The very-long-baseline interferometry properties of the superluminal features in the jet of 3C 345 and other similar sources can be explained by models invoking the emission from shocks, at least within the vicinity of the compact core. Inverse-Compton calculations, constrained by x-ray observations, yield realistic estimates for the physical conditions in the parsec-scale jet. There is evidence for a transition region in this source beyond which other factors (e.g., plasma interactions and nonsynchrotron radiation processes) may become prominent. Multifrequency and polarization imaging (especially at high frequencies) are emerging as critical tools in testing model predictions. PMID:11607595

  3. Morphology of high-luminosity compact radio sources.

    PubMed Central

    Zensus, J A; Krichbaum, T P; Lobanov, A P

    1995-01-01

    High-dynamic range imaging and monitoring with very-long-baseline interferometry reveal a rich morphology of luminous flat-spectrum radio sources. One-sided core-jet structures abound, and superluminal motion is frequently measured. In a few cases, both distinct moving features and diffuse underlying jet emission can be detected. Superluminal motion seen in such sources is typically complex, on curved trajectories or ridge lines, and with variable component velocities, including stationary features. The curved trajectories seen can be modeled by helical motion within the underlying jet flow. The very-long-baseline interferometry properties of the superluminal features in the jet of 3C 345 and other similar sources can be explained by models invoking the emission from shocks, at least within the vicinity of the compact core. Inverse-Compton calculations, constrained by x-ray observations, yield realistic estimates for the physical conditions in the parsec-scale jet. There is evidence for a transition region in this source beyond which other factors (e.g., plasma interactions and nonsynchrotron radiation processes) may become prominent. Multifrequency and polarization imaging (especially at high frequencies) are emerging as critical tools in testing model predictions. PMID:11607595

  4. VLA observations of NGC 247: identification of compact radio sources including three candidate UD H II regions

    SciTech Connect

    Lacey, Christina K.; Vuolo, Matthew; Schultz, Sara

    2014-03-01

    A high resolution, Very Large Array continuum survey of NGC 247 was undertaken in order to identify compact thermal and nonthermal radio sources, such as supernova remnants (SNRs) and H II regions. NGC 247 was observed at two frequencies, 20 cm and 6 cm, in order to calculate the spectral index, and the survey resulted in the identification of 19 compact radio sources. Using the spectral index to discriminate between source types, we identify two candidate SNRs and one H II region. Three of the radio sources have inverted spectra, indicative of ultradense H II (UD H II) regions, the short-lived, dense cores where massive stars form. Four of the sources are thermal in origin, but were not detected at 20 cm, so they could be H II regions or UD H II regions. The rest of the sources are nonthermal or undetermined. We compare the radio images with Hα, V band, and infrared archive images to look for correspondences that confirm that the sources reside in NGC 247 and are not background sources. We find that over two-thirds of the radio sources have counterparts in the Hα or V band images and are associated with NGC 247. The most luminous radio source in NGC 247 is a candidate SNR, and if confirmed as an SNR, it would be a very luminous extragalactic SNR. The H II regions and UD H II regions are calculated to have ionizing luminosities of between 4-10 × 10{sup 50} s{sup –1}; each individual source would require between 41-100 O7.5V stars to produce the corresponding ionizing luminosity. The ionizing luminosity of the UD H II regions indicates that these UD H II regions represent the lower luminosity population of the known UD H II regions and thus, they may represent a more typical population of UD H II regions that can be found and studied in the nearby galaxies as opposed to more extreme examples that have been found previously.

  5. Occultation of a compact radio source by Venus

    NASA Astrophysics Data System (ADS)

    Linfield, R.

    1992-05-01

    An occultation of the compact radio source P 0507+17 by Venus on 19 Jul. 1988, was observed in Tidbinbilla, Australia at a frequency of 2.3 GHz. The purpose of this observation was to measure the position of Venus in the radio reference frame. When data from both ingress (Venus dayside) and egress (Venus nightside) were used to solve for the position of Venus in ecliptic longitude and latitude, the results were consistent with zero offsets from the nominal values, with an uncertainty of approximately 0.2 arcsec in both coordinates. By using the nightside data alone, a value of -0.026 +/- 0.04 arcsec was obtained for the linear combination delta(lambda) + 0.51delta(beta), where delta(lambda) and delta(beta) were the offsets from their nominal values of the ecliptic longitude and latitude of Venus. Distortion of a vacuum Fresnel fringe pattern by the Venus troposphere, and especially by the Venus ionosphere, was observed. The dayside ionosphere of Venus caused very large distortions; the amplitude of the first Fresnel fringe in the ingress data was eight times larger than was expected for an airless planet. The observed fringe patterns were modeled by using plausible ionospheres (i.e., consistent with spacecraft measurements of the Venus ionosphere and with solar extreme ultraviolet flux and solar wind pressure measurements at the occultation epoch). However, the range of Venus ionospheric profiles (electron density as a function of altitude) allowed by a priori constraints and by the occultation data was large (e.g., the ionopause height on the dayside was uncertain by a factor of two). This ionospheric uncertainty (particularly on the dayside) translated into a large position uncertainty (0.2 arcsec for the dayside and 0.04 arcsec for the nightside). If it was possible to calibrate the Venus ionosphere by some external means, the accuracy in delta(lambda) and delta(beta) would have been 0.01 arcsec or better.

  6. VizieR Online Data Catalog: Compact radio cores in radio galaxies. (Jones+, 1994)

    NASA Astrophysics Data System (ADS)

    Jones, P. A.; McAdam, W. B.; Reynolds, J. E.

    1999-04-01

    This catalog contains compact core fluxes for a list of 175 southern radio galaxies, measured with the Parkes-Tidbinbilla Interferometer (PTI, Norris et al. 1988ApJS...67...85N) on a single 275 km baseline at 2.3 GHz and 8.4 GHz. The sample consists of large angular size ( > 0.5 arcmin) steep spectrum sources from Jones & McAdam (1992ApJS...80..137J) observed to determine the fraction of flux contained in compact (VLBI-scale) cores. Of the 172 sources observed at 2.3 GHz (100 milliarcsec fringe spacing), 63 had cores detected and upper limits were determined for the remaining 109. Of the 88 sources observed at 8.4 GHz (30 milliarcsec fringe spacing), 38 had cores detected and 50 have upper limits. A comparison of the detections and upper limits at the two frequencies shows that the cores have flat or inverted spectra. The core fluxes quoted here may vary by around 20 % if there is structure on the scale of the fringe spacing and the cores are probably intrinsically variable. (1 data file).

  7. First Detection in Gamma-Rays of a Young Radio Galaxy: Fermi-LAT Observations of the Compact Symmetric Object PKS 1718-649

    NASA Astrophysics Data System (ADS)

    Migliori, G.; Siemiginowska, A.; Sobolewska, M.; Loh, A.; Corbel, S.; Ostorero, L.; Stawarz, Ł.

    2016-04-01

    We report the γ-ray detection of a young radio galaxy, PKS 1718-649, belonging to the class of compact symmetric objects (CSOs), with the Large Area Telescope (LAT) on board the Fermi satellite. The third Fermi Gamma-ray LAT catalog (3FGL) includes an unassociated γ-ray source, 3FGL J1728.0-6446, located close to PKS 1718-649. Using the latest Pass 8 calibration, we confirm that the best-fit 1σ position of the γ-ray source is compatible with the radio location of PKS 1718-649. Cross-matching of the γ-ray source position with the positions of blazar sources from several catalogs yields negative results. Thus, we conclude that PKS 1718-649 is the most likely counterpart to the unassociated LAT source. We obtain a detection test statistics TS ˜ 36 (>5σ) with a best-fit photon spectral index Γ = 2.9 ± 0.3 and a 0.1-100 GeV photon flux density F 0.1-100 GeV = (11.5 ± 0.3) × 10-9 ph cm-2 s-1. We argue that the linear size (˜2 pc), the kinematic age (˜100 years), and the source distance (z = 0.014) make PKS 1718-649 an ideal candidate for γ-ray detection in the framework of the model proposing that the most compact and the youngest CSOs can efficiently produce GeV radiation via inverse-Compton scattering of the ambient photon fields by the radio lobe non-thermal electrons. Thus, our detection of the source in γ-rays establishes young radio galaxies as a distinct class of extragalactic high-energy emitters and yields a unique insight on the physical conditions in compact radio lobes interacting with the interstellar medium of the host galaxy.

  8. Compact continuum source finding for next generation radio surveys

    NASA Astrophysics Data System (ADS)

    Hancock, P. J.; Murphy, T.; Gaensler, B. M.; Hopkins, A.; Curran, J. R.

    2012-05-01

    We present a detailed analysis of four of the most widely used radio source-finding packages in radio astronomy, and a program being developed for the Australian Square Kilometer Array Pathfinder telescope. The four packages: SEXTRACTOR, SFIND, IMSAD and SELAVY are shown to produce source catalogues with high completeness and reliability. In this paper we analyse the small fraction (˜1 per cent) of cases in which these packages do not perform well. This small fraction of sources will be of concern for the next generation of radio surveys which will produce many thousands of sources on a daily basis, in particular for blind radio transients surveys. From our analysis we identify the ways in which the underlying source-finding algorithms fail. We demonstrate a new source-finding algorithm AEGEAN, based on the application of a Laplacian kernel, which can avoid these problems and can produce complete and reliable source catalogues for the next generation of radio surveys.

  9. The compact radio structure of radio-loud NLS1 galaxies and the relationship to CSS sources

    NASA Astrophysics Data System (ADS)

    Gu, M.; Chen, Y.; Komossa, S.; Yuan, W.; Shen, Z.

    2016-02-01

    Narrow-line Seyfert 1 galaxies are thought to be young AGNs with relatively small black hole masses and high accretion rates. Radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar-like characteristics, while others resemble compact steep-spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed by the gamma-ray flaring of some of them. These properties may possibly be contrary to typical radio-loud AGNs, in light of the low black-hole masses, and high accretion rates. We present the compact radio structure of fourteen RLNLS1 galaxies from Very Long Baseline Array observations at 5 GHz in 2013. Although all these sources are very radio-loud with {R > 100}, their jet properties are diverse, in terms of their milli-arcsecond (mas) scale (pc scale) morphology and their overall radio spectral shape. The core brightness temperatures of our sources are significantly lower than those of blazars, therefore, the beaming effect is generally not significant in our sources, compared to blazars. This implies that the bulk jet speed may likely be low in our sources. The relationship between RLNLS1s and compact steep-spectrum sources, and the implications on jet formation are discussed based on the pc-scale jet properties.

  10. On the nature of bright compact radio sources at z>4.5

    NASA Astrophysics Data System (ADS)

    Coppejans, Rocco; Frey, Sándor; Cseh, Dávid; Müller, Cornelia; Paragi, Zsolt; Falcke, Heino; Gabányi, Krisztina É.; Gurvits, Leonid I.; An, Tao; Titov, Oleg

    2016-09-01

    High-redshift radio-loud quasars are used to, among other things, test the predictions of cosmological models, set constraints on black hole growth in the early universe and understand galaxy evolution. Prior to this paper, 20 extragalactic radio sources at redshifts above 4.5 have been imaged with very long baseline interferometry (VLBI). Here we report on observations of an additional ten z > 4.5 sources at 1.7 and 5 GHz with the European VLBI Network (EVN), thereby increasing the number of imaged sources by 50 per cent. Combining our newly observed sources with those from the literature, we create a substantial sample of 30 z > 4.5 VLBI sources, allowing us to study the nature of these objects. Using spectral indices, variability and brightness temperatures, we conclude that of the 27 sources with sufficient information to classify, the radio emission from one source is from star formation, 13 are flat-spectrum radio quasars and 13 are steep-spectrum sources. We also argue that the steep-spectrum sources are off-axis (unbeamed) radio sources with rest-frame self-absorption peaks at or below GHz frequencies and that these sources can be classified as gigahertz peaked-spectrum (GPS) and megahertz peaked-spectrum (MPS) sources.

  11. Compact radio sources in the spiral galaxy M83

    NASA Astrophysics Data System (ADS)

    Soria, Roberto; Long, Knox S.; Winkler, P. Frank; Kuntz, Kip; Blair, William

    2011-04-01

    We are doing a multiband study of the stellar life cycle in the grand-design spiral galaxy M83, one of the most actively star-forming systems in the local Universe. We have already obtained exceptional optical coverage with HST and Magellan, and we have been awarded 750 ks of Chandra time this year. Now we propose an ATCA radio study, crucial for integrating the optical and X-ray studies. The radio study will allow us to achieve three main objectives: a) monitor the long-term evolution of three historical supernovae observed in M83 over the last 100 years, and hence constrain the late stages of evolution of their stellar progenitors; b) determine the distribution, radio spectral index and other physical properties of different types of young supernova remnants; c) resolve the morphology and search for variability of the nuclear sources: in particular, we will investigate the radio evidence for a double nucleus. In addition, we will study the aligned triple source just outside the nucleus: the traditional interpretation is that it is a background radio galaxy, but it has recently been suggested that it could be a recoiling nuclear black hole in M83.

  12. Extragalactic jets as probes of distant clusters of galaxies and the clusters occupied by bent radio AGN (COBRA) survey

    NASA Astrophysics Data System (ADS)

    Blanton, Elizabeth L.; Paterno-Mahler, Rachel; Wing, Joshua D.; Ashby, M. L. N.; Golden-Marx, Emmet; Brodwin, Mark; Douglass, E. M.; Randall, Scott W.; Clarke, T. E.

    2015-03-01

    We are conducting a large survey of distant clusters of galaxies using radio sources with bent jets and lobes as tracers. These radio sources are driven by AGN and achieve their bent morphologies through interaction with the surrounding gas found in clusters of galaxies. Based on low-redshift studies, these types of sources can be used to identify clusters very efficiently. We present initial results from our survey of 653 bent-double radio sources with optical hosts too faint to appear in the SDSS. The sample was observed in the infrared with Spitzer, and it has revealed ~200 distant clusters or proto-clusters in the redshift range z ~ 0.7 - 3.0. The sample of bent-doubles contains both quasars and radio galaxies enabling us to study both radiative and kinetic mode feedback in cluster and group environments at a wide range of redshifts.

  13. A Catalog of 2118 Compact Radio Sources in the Northern Sky

    NASA Astrophysics Data System (ADS)

    Wrobel, J. M.; Patnaik, A. R.; Browne, I. W. A.; Wilkinson, P. N.

    1998-12-01

    A catalog of 2118 compact radio sources was derived from the Jodrell Bank - VLA Astrometric Survey (JVAS) of flat-spectrum sources (Patnaik et al. 1992, mnras, 254, 655; Browne et al. 1998, mnras, 293, 257; Wilkinson et al., mnras, in press). Each compact VLA source (a) has a peak flux density at 8.4 GHz >= 50 mJy at a resolution of 200 milliarcsec; (b) contains 80% or more of the total source flux density; and (c) has a position known to an rms accuracy of 12-55 milliarcsec. The 2118 sources are uniformly distributed in the northern sky at Galactic latitudes mid b mid >= 2.5(deg) . Although these sources are primarily intended for use as phase calibrators for the Jodrell Bank MERLIN, they will also be suitable as phase calibrators for the NRAO VLA and can be considered as candidate phase calibrators for VLBI arrays (Peck & Beasley 1998, IAU Colloquium 164, 155) and the NRAO MMA (Holdaway, Owen & Rupen 1994, MMA Memo No. 123). Furthermore, compact radio sources close to the Galactic plane can be used to probe the interstellar medium, through studies of scintillation, angular broadening, Faraday rotation, and both molecular and atomic absorption. Compact radio sources are also useful as navigation aids for spacecraft missions to Solar System bodies. Finally, masing conditions in cometary comas can be examined by observing compact radio sources during occultation events. The catalog of 2118 compact radio sources is available via anonymous ftp from host ftp.aoc.nrao.edu; cd to directory /pub and get file sources.jvas. The file can be read by the NRAO VLBI scheduling program SCHED.

  14. Cosmological Constraints from Compact Radio Source Angular Size versus Redshift Data

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Ratra, Bharat

    2003-01-01

    We use the Gurvits, Kellermann, & Frey compact radio source angular size versus redshift data to place constraints on cosmological model parameters in models with and without a constant or time-variable cosmological constant. The resulting constraints are consistent with but weaker than those determined using current supernova apparent magnitude versus redshift data.

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

    SciTech Connect

    Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina E-mail: l.zapata@crya.unam.mx

    2014-07-20

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

  16. A sample of southern Compact Steep Spectrum radio sources: The VLBI observations

    NASA Astrophysics Data System (ADS)

    Tzioumis, A.; King, E.; Morganti, R.; Dallacasa, D.; Tadhunter, C.; Fanti, C.; Reynolds, J.; Jauncey, D.; Preston, R.; McCulloch, P.; Tingay, S.; Edwards, P.; Costa, M.; Jones, D.; Lovell, J.; Clay, R.; Meier, D.; Murphy, D.; Gough, R.; Ferris, R.; White, G.; Jones, P.

    2002-09-01

    A small sample of 7 southern Compact Steep Spectrum (CSS) radio sources has been selected as part of the study of a larger flux-limited complete sample of radio sources. High resolution images, using the VLBI network in the southern hemisphere and the high resolution MERLIN array, are presented for all sources in the CSS sample. The overall morphology of each source consists of well-defined double lobes but with substantial diffuse and extended components present. In the majority of cases only a fraction of the total flux density is detected on the VLBI baselines, indicating the presence of larger extended radio structures. However, all sources are unresolved at arcsecond scales and are of sub-galactic size, with linear size in the range 0.1-2 kpc. The radio properties of the sources agree well with CSS sources in other samples. Based on observations with the Southern Hemisphere VLBI Network (SHEVE) and the MERLIN.

  17. VLBI Observations of Gamma-Ray-Quiet AGN: Comparing Radio Core Brightness Temperatures

    NASA Technical Reports Server (NTRS)

    Tingay, S. J.; Murphy, D. W.; Lovell, J. E. J.; Costa, M. E.; McCulloch, P.; Edwards, P. G.; Jauncey, D. L.; Reynolds, J. E.; Tzioumis, A. K.; King, E. A.; Jones, D. L.; Preston, R. A.; Meier, D. L.; van Ommen, T. D.; Nicolson, G. D.; Quick, J. F. H.

    1998-01-01

    We present VLBI and Australia Telescope Compact Array images, and derive source frame radio-core brightness temperatures for three prominent, flat-spectrum extragalactic radio sources, notable because they have not been detected as gamma-ray sources with the EGRET instrument.

  18. Extremely red compact radio sources - The empty field objects

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.; Neugebauer, G.; Soifer, B. T.; Matthews, K.; Wootten, H. A.; Pravdo, S. H.

    1981-01-01

    Radiation of 10 microns has been detected from 1413+135, one of the very red objects discovered by Rieke, Lebofsky, and Kinman (1979) at near-infrared wavelengths. The spectrum of this object flattens at wavelengths longer than 2.2 microns. Upper limits are also given for the 10-micron emission from 2255+14, 0026+34, and 0406+121. Photometry between 1.25 and 2.2 microns confirms the variability of 1413+135, 2255+41, and 0406+121. Five percent resolution spectra of 1413+135 and 0406+121 between 1.5 and 2.4 microns show no emission or absorption lines. The spectral data rule out the possibility that 1413+135 is a quasar with normal line strengths and a redshift less than 1.3 and greater than 4. The lack of features of the 1.5-2.4-micron spectra, the rapid variability, and the overall shape of the radio, infrared, and X-ray energy distributions are consistent with a BL Lac nature for these objects.

  19. The possibility of using sparse reference-star grids to determine the optical positions of extragalactic radio sources

    NASA Astrophysics Data System (ADS)

    Lazorenko, P. F.

    The paper examines a method for determining plate constants using two reference-star grids: (1) AGK 2, and (2) a grid based on the n = 3 stars closest to the radio source with positions in the FK4 system with an accuracy up to sigma(f) = 0.08 arcsec. In this case, it is possible to link the secondary reference grid with the FK4 system with an accuracy of sigma(f)/square root of n of about 0.05 arcsec.

  20. The compact structure of radio-loud broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Jiang, D. R.; Wang, T. G.; Xie, F. G.

    2008-11-01

    We present the results of EVN+MERLIN very long baseline interferometry (VLBI) polarization observations of eight broad absorption line (BAL) quasars at 1.6 GHz, including four low-ionization BAL quasars (LoBALs) and four high-ionization BAL quasars (HiBALs) with either steep or flat spectra on Very Large Array (VLA) scales. Only one steep-spectrum source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other four steep-spectrum sources and three flat-spectrum sources display either an unresolved image or a core-jet structure on scales of less than 300 pc. In all cases, the marginally resolved core is the dominant radio component. Linear polarization in the cores has been detected in the range of a few to 10 per cent. Polarization, together with high brightness temperatures (from 2 × 109 to 5 × 1010K), suggests a synchrotron origin for the radio emission. There is no apparent difference in the radio morphologies or polarization between low-ionization and high-ionization BAL quasi-stellar objects (QSOs) or between flat- and steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat and steep spectra, and consider a possible evolutionary scenario for BAL QSOs. In this scenario, BAL QSOs are probably a young population of radio sources that are compact steep spectrum or GHz peaked radio source analogues at the low end of radio power.

  1. CONSTRAINING THE EVOLUTIONARY FATE OF CENTRAL COMPACT OBJECTS: ''OLD'' RADIO PULSARS IN SUPERNOVA REMNANTS

    SciTech Connect

    Bogdanov, Slavko; Ng, C.-Y.; Kaspi, Victoria M.

    2014-09-10

    Central compact objects (CCOs) constitute a population of radio-quiet, slowly spinning (≥100 ms) young neutron stars with anomalously high thermal X-ray luminosities. Their spin-down properties imply weak dipole magnetic fields (∼10{sup 10-11} G) and characteristic ages much greater than the ages of their host supernova remnants (SNRs). However, CCOs may posses strong ''hidden'' internal magnetic fields that may re-emerge on timescales of ≳10 kyr, with the neutron star possibly activating as a radio pulsar in the process. This suggests that the immediate descendants of CCOs may be masquerading as slowly spinning ''old'' radio pulsars. We present an X-ray survey of all ordinary radio pulsars within 6 kpc that are positionally coincident with Galactic SNRs in order to test the possible connection between the supposedly old but possibly very young pulsars and the SNRs. None of the targets exhibit anomalously high thermal X-ray luminosities, suggesting that they are genuine old ordinary pulsars unrelated to the superposed SNRs. This implies that CCOs are either latent radio pulsars that activate long after their SNRs dissipate or they remain permanently radio-quiet. The true descendants of CCOs remain at large.

  2. Accurate radio and optical positions for southern radio sources

    NASA Technical Reports Server (NTRS)

    Harvey, Bruce R.; Jauncey, David L.; White, Graeme L.; Nothnagel, Axel; Nicolson, George D.; Reynolds, John E.; Morabito, David D.; Bartel, Norbert

    1992-01-01

    Accurate radio positions with a precision of about 0.01 arcsec are reported for eight compact extragalactic radio sources south of -45-deg declination. The radio positions were determined using VLBI at 8.4 GHz on the 9589 km Tidbinbilla (Australia) to Hartebeesthoek (South Africa) baseline. The sources were selected from the Parkes Catalogue to be strong, flat-spectrum radio sources with bright optical QSO counterparts. Optical positions of the QSOs were also measured from the ESO B Sky Survey plates with respect to stars from the Perth 70 Catalogue, to an accuracy of about 0.19 arcsec rms. These radio and optical positions are as precise as any presently available in the far southern sky. A comparison of the radio and optical positions confirms the estimated optical position errors and shows that there is overall agreement at the 0.1-arcsec level between the radio and Perth 70 optical reference frames in the far south.

  3. Do the compact radio sources in NGC 253 and M82 fade over time?

    NASA Technical Reports Server (NTRS)

    Ulvestad, James S.; Antonucci, Robert R. J.

    1994-01-01

    The nearby starburst galaxy NGC 253 has been observed at a third epoch at 6 cm, and a second epoch at 3.6 cm, using the highest resolution configuration of the Very Large Array (VLA). Over a total time span of 4 yr between 1987 and 1991, no new compact radio sources have appeared. The flux density limit ranges from 3 mJy (3 times the power of Cas A) for most of the main body of the source to approximately 0.3 mJy off the diffuse source surrounding the nucleus. Furthermore, there is no evidence for significant source fading over 4 yr, in contrast to the result reported by Kronberg & Sramek (1985) for M82. More recent data suggest that, except for the strongest source in that galaxy, the compact radio sources in M82 may not be fading after all. If this suggestion proves correct, supernova rates of 0.2-0.3/yr in M82, estimated based on the assumed source fading, are incorrect. More accurate limits on source fading indicate that the current rate of production of radio supernovae in M82 is no greater than 0.1/yr, while that in NGC 253 is no greater than 0.25/yr.

  4. The Population of Compact Radio Sources in the Orion Nebula Cluster

    NASA Astrophysics Data System (ADS)

    Forbrich, J.; Rivilla, V. M.; Menten, K. M.; Reid, M. J.; Chandler, C. J.; Rau, U.; Bhatnagar, S.; Wolk, S. J.; Meingast, S.

    2016-05-01

    We present a deep centimeter-wavelength catalog of the Orion Nebula Cluster (ONC), based on a 30 hr single-pointing observation with the Karl G. Jansky Very Large Array in its high-resolution A-configuration using two 1 GHz bands centered at 4.7 and 7.3 GHz. A total of 556 compact sources were detected in a map with a nominal rms noise of 3 μJy bm‑1, limited by complex source structure and the primary beam response. Compared to previous catalogs, our detections increase the sample of known compact radio sources in the ONC by more than a factor of seven. The new data show complex emission on a wide range of spatial scales. Following a preliminary correction for the wideband primary-beam response, we determine radio spectral indices for 170 sources whose index uncertainties are less than ±0.5. We compare the radio to the X-ray and near-infrared point-source populations, noting similarities and differences.

  5. The Extragalactic Distance Scale

    NASA Astrophysics Data System (ADS)

    Livio, Mario; Donahue, Megan; Panagia, Nino

    1997-07-01

    Participants; Preface; Foreword; Early history of the distance scale problem, S. van den Bergh; Cosmology: From Hubble to HST, M. S. Turner; Age constraints nucleocosmochronology, J. Truran; The ages of globular clusters, P. Demarque; The linearity of the Hubble flow M. Postman; Gravitational lensing and the extragalactic distance scale, R. D. Blandford andT . Kundic; Using the cosmic microwave background to constrain the Hubble constant A. Lasenby and T M. Jones; Cepheids as distance indicators, N. R. Tanvir; The I-band Tully-Fisher relation and the Hubble constant, R. Giovanell; The calibration of type 1a supernovae as standard candles, A. Saha; Focusing in on the Hubble constant, G. A. Tammann & M. Federspiel; Interim report on the calibration of the Tully-Fisher relation in the HST Key Project to measure the Hubble constant, J. Mould et al.; Hubble Space Telescope Key Project on the extragalactic distance scale, W. L. Freedman, B. F. Madore and T R. C. Kennicutt; Novae as distance indicators, M. Livio; Verifying the planetary nebula luminosity function method, G. H. Jacoby; On the possible use of radio supernovae for distance determinations, K. W. Weiler et al.; Post-AGB stars as standard candles, H. Bond; Helium core flash at the tip of the red giant branch: a population II distance indicator, B. F. Madore, W. L. Freedman and T S. Sakai; Globular clusters as distance indicators, B. C. Whitmore; Detached eclipsing binaries as primary distance and age indicators, B. Paczynski; Light echoes: geometric measurement of galaxy distances, W. B. Sparks; The SBF survey of galaxy distances J. L. Tonry; Extragalactic distance scales: The long and short of it, V. Trimble.

  6. Submilliarcsecond VLBI Using Compact Close Pairs of Radio Sources: Error Analysis

    NASA Technical Reports Server (NTRS)

    Morabito, D. D.

    1984-01-01

    The potential accuracy attainable for (delta) VLBI positional measurements (submilliarc second level) is reached by simultaneously observing pairs of compact radio sources whose angular separation are smaller than the beamwidth of each antenna. Simultaneous (delta) VLBI (SVLBI) enables significant cancellation of measurement errors. Solar plasma is the dominant fluctuating error source in SVLBI positional measurements since there is enhanced cancellation of the troposphere and ionosphere, and complete cancellation of oscillator instabilities. Of the nonfluctuating error sources, errors due to universal time predominate. By performing SVLBI experiments over several years with many different close pairs of radio sources, limits can be placed on reference frame stability. Intrinsic properties of the sources, such as source structure and proper motion, will limit measurements. The SVLBI differential phase and corruptive noise sources will be discussed here along with estimated results.

  7. Compact Radio Sources and Jet-driven AGN Feedback in the Early Universe: Constraints from Integral-Field Spectroscopy

    SciTech Connect

    Nesvadba, N H; Lehnert, M D; De Breuck, C; Gilbert, A; van Breugel, W

    2007-07-05

    To investigate the impact of radio jets during the formation epoch of their massive host galaxies, we present an analysis of two massive, log M{sub stellar}/M{sub {circle_dot}} {approx} 10.6 and 11.3, compact radio galaxies at z = 3.5, TNJ0205+2242 and TNJ0121+1320. Their small radio sizes (R {le} 10 kpc) are most likely a sign of youth. In particular, we compare their radio properties and gas dynamics with those in well extended radio galaxies at high redshift, which show strong evidence for powerful, jet-driven outflows of significant gas masses (M {approx} 10{sup 9-10} M{sub {circle_dot}}). Our analysis combines rest-frame optical integral-field spectroscopy obtained with SINFONI on the VLT with existing radio imaging, CO(4-3) emission line spectra, and rest-frame UV longslit spectroscopy. [OIII]{lambda}5007 line emission is compact in both galaxies and lies within the region defined by the radio lobes. For TNJ0205+2242, the Ly{alpha} profile narrows significantly outside the jet radius, indicating the presence of a quiescent halo. TNJ0121+1320 has two components at a projected relative distance of {approx}10 kpc and a velocity offset of {approx}300 km s{sup -1}, measured from the [OIII]{lambda}5007 velocity map. This suggests that the fainter component is orbiting around the more massive, radio-loud galaxy. If motions are gravitational, this implies a dynamical mass of 2 x 10{sup 11} M{sub {circle_dot}} for the radio-loud component. The dynamical mass, molecular gas mass measured from the CO line emission, and radio luminosity of these two compact radio galaxies imply that compact radio sources may well develop large-scale, energetic outflows as observed in extended radio galaxies, with the potential of removing significant fractions of the ISM from the host galaxy. The absence of luminous emission line gas extending beyond the radio emission in these sources agrees with the observed timescales and outflow rates in extended radio galaxies, and adds further

  8. Plasma discharge characteristics in compact SF6 radio-frequency plasma source for plasma etching application

    NASA Astrophysics Data System (ADS)

    Motomura, Taisei; Takahashi, Kazunori; Kasashima, Yuji; Uesugi, Fumihiko; Ando, Akira

    2015-09-01

    In order to create a compact plasma etching reactor, plasma discharge characteristics in compact SF6 radio-frequency (RF) plasma source which has a chamber diameter of 40 mm have been studied. Convergent magnetic field configuration produced by a solenoid coil and a permanent magnet located behind substrate is employed for efficient plasma transport downstream of plasma source. A discharge characteristics with the changes in relative emission intensity of fluorine atom of FI at 703.7 nm in compact SF6 plasma source are discussed: the dependence of relative emission intensity on the magnetic field strength, the RF input power, and the mass flow rate of the SF6 gas. The relative emission intensity was significantly increased when the RF input power is ~150 W. We present the fundamental etching performance (especially etching rate) of compact plasma source, and then the etching rate of 0.1-1.0 μm/min was obtained under the condition of a RF input power of 50-200 W, a mass flow rate of SF6 of 5.5 sccm and a bias RF power of 20 W. The results of test etching will be shown in presentation.

  9. Radio jets in NGC 4151

    NASA Technical Reports Server (NTRS)

    Johnston, K. J.; Elvis, M.; Kjer, D.; Shen, B. S. P.

    1982-01-01

    The relationship between the radio and optical emissions from the nucleus of the Seyfert galaxy NGC 4151 is investigated by mapping the radio radiation from this source at wavelengths of 20 and 6 cm using the Very Large Array of the National Radio Astronomy Observatory. Results show that the radio emission at wavelengths from 20 to 6 cm extend 10'' (950 pc) along a position angle of 72-84 degrees. This nonthermal emission is found to consist of at least six components and is similar to jets observed in other compact extragalactic radio sources. These radio jets appear to be coincident with the optical line emission region in NGC 4151 and are aligned with the position angle of the linearly polarized optical continuum emission.

  10. Deep Hubble Space Telescope imaging of a compact radio galaxy at z = 2.390

    NASA Technical Reports Server (NTRS)

    Windhorst, Rogier; Mathis, Douglas F.; Keel, William C.

    1992-01-01

    The radio galaxy with the highest redshift in the Leiden-Berkeley Deep Survey, 53W002, is described and examined in terms of UV profile in relation to an early-type galaxy. The HST WFC images have a resolution of 0.2 arcsec FWHM, and the I- and V-band structures are assessed. The source is elongated in a manner similar to the Ly alpha cloud in V, and the structure is highly compact in I. The present object with a young starburst has very high central UV surface brightnesses relative to nearby luminous early-type galaxies, while the light profiles are similar. The data are concluded to suggest that 53W002 is a young galaxy that has a regular light profile at z = 2.390 even though it has been forming stars since not more than about 0.5 Gyr before z = 2.390. Such a scenario is consistent with concurrent dynamical collapse and star formation in the compact radio galaxy.

  11. Optical variability of extragalactic objects used to tie the HIPPARCOS reference frame to an extragalactic system using Hubble space telescope observations

    NASA Technical Reports Server (NTRS)

    Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel

    1990-01-01

    Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65 percent are optical variables beyond a 0.2 mag limit. To ensure proper exposure times, accurate mean magnitudes are necessary. In many cases, the average magnitudes listed in the literature were not adequate. The literature was searched for all relevant photometric information for the EGOs, and photometric parameters were derived, including mean magnitude, maximum range, and timescale of variability. This paper presents the results of that search and the parameters derived. The results will allow exposure times to be estimated such that an observed magnitude different from the tabular magnitude by 0.5 mag in either direction will not degrade the astrometric centering ability on a Planetary Camera CCD frame.

  12. Radio flares of compact binary mergers: the effect of non-trivial outflow geometry

    NASA Astrophysics Data System (ADS)

    Margalit, Ben; Piran, Tsvi

    2015-10-01

    The next generation gravitational waves (GW) detectors are most sensitive to GW emitted by compact (neutron star/black hole) binary mergers. If one of those is a neutron star the merger will also emit electromagnetic radiation via three possible channels: gamma-ray bursts and their (possibly orphan) afterglows, Li-Paczynski Macronovae and radio flares. This accompanying electromagnetic radiation is vitally important in confirming the GW detections. It could also reveal a wealth of information regarding the merger and will open a window towards multimessenger astronomy. Identifying and characterizing these counterparts is therefore of utmost importance. In this work, we explore late time radio flares emitted by the dynamically ejected outflows. We build upon previous work and consider the effect of the outflow's non-trivial geometry. Using an approximate method, we estimate the radio light-curves for several ejected matter distributions obtained in numerical simulations. Our method provides an upper limit to the effect of non-sphericity. Together with the spherical estimates, the resulting light curves bound the actual signal. We find that while non-spherical geometries can in principle lead to an enhanced emission, in most cases they result in an increase in the time-scale compared with a corresponding spherical configuration. This would weaken somewhat these signals and might decrease the detection prospects.

  13. Structure and evolution of the compact radio source in NGC 1275.

    PubMed Central

    Romney, J D; Benson, J M; Dhawan, V; Kellermann, K I; Vermeulen, R C; Walker, R C

    1995-01-01

    Investigations of the fine-scale structure in the compact nucleus of the radio source 3C 84 in NGC 1275 (New General Catalogue number) are reported. Structural monitoring observations beginning as early as 1976, and continuing to the present, revealed subluminal motions in a jet-like relatively diffuse region extending away from a flat-spectrum core. A counterjet feature was discovered in 1993, and very recent nearly simultaneous studies have detected the same feature at five frequencies ranging from 5 to 43 GHz. The counterjet exhibits a strong low-frequency cutoff, giving this region of the source an inverted spectrum. The observations are consistent with a physical model in which the cutoff arises from free-free absorption in a volume that surrounds the core but obscures only the counterjet feature. If such a model is confirmed, very-long-baseline radio interferometry observations can then be used to probe the accretion region, outside the radio jet, on parsec scales. PMID:11607597

  14. Structure and evolution of the compact radio source in NGC 1275.

    PubMed

    Romney, J D; Benson, J M; Dhawan, V; Kellermann, K I; Vermeulen, R C; Walker, R C

    1995-12-01

    Investigations of the fine-scale structure in the compact nucleus of the radio source 3C 84 in NGC 1275 (New General Catalogue number) are reported. Structural monitoring observations beginning as early as 1976, and continuing to the present, revealed subluminal motions in a jet-like relatively diffuse region extending away from a flat-spectrum core. A counterjet feature was discovered in 1993, and very recent nearly simultaneous studies have detected the same feature at five frequencies ranging from 5 to 43 GHz. The counterjet exhibits a strong low-frequency cutoff, giving this region of the source an inverted spectrum. The observations are consistent with a physical model in which the cutoff arises from free-free absorption in a volume that surrounds the core but obscures only the counterjet feature. If such a model is confirmed, very-long-baseline radio interferometry observations can then be used to probe the accretion region, outside the radio jet, on parsec scales. PMID:11607597

  15. Very-long-baseline radio interferometry surveys of the compact structure in active galactic nuclei.

    PubMed Central

    Wilkinson, P N

    1995-01-01

    Very-long-baseline radio interferometry (VLBI) imaging surveys have been undertaken since the late 1970s. The sample sizes were initially limited to a few tens of objects but the snapshot technique has now allowed samples containing almost 200 sources to be studied. The overwhelming majority of powerful compact sources are asymmetric corejects of one form or another, most of which exhibit apparent superluminal motion. However 5-10% of powerful flat-spectrum sources are 100-parsec (pc)-scale compact symmetric objects; these appear to form a continuum with the 1-kpc-scale double-lobed compact steep-spectrum sources, which make up 15-20% of lower frequency samples. It is likely that these sub-galactic-size symmetric sources are the precursors to the large-scale classical double sources. There is a surprising peak around 90 degrees in the histogram of misalignments between the dominant source axes on parsec and kiloparsec scales; this seems to be associated with sources exhibiting a high degree of relativistic beaming. VLBI snapshot surveys have great cosmological potential via measurements of both proper motion and angular size vs. redshift as well as searches for gravitational "millilensing." PMID:11607594

  16. A compact radio frequency quadrupole for ion bunching in the WITCH experiment

    NASA Astrophysics Data System (ADS)

    Traykov, E.; Beck, M.; Breitenfeldt, M.; Delahaye, P.; De Leebeeck, V.; Friedag, P.; Herlert, A.; Geeraert, N.; Heirman, W.; Lønne, P.-I.; Mader, J.; Roccia, S.; Soti, G.; Tandecki, M.; Timmermans, M.; Thiboud, J.; Van Gorp, S.; Wauters, F.; Weinheimer, C.; Zákoucký, D.; Severijns, N.

    2011-08-01

    During the last several years the WITCH (Weak Interaction Trap for CHarged particles) experimental setup at ISOLDE has undergone various upgrades aiming at improvement of general performance. An essential innovation, a compact Radio Frequency Quadrupole (RFQ) ion cooler and buncher device, was designed and successfully commissioned as a part of the off-line tuning system of WITCH. The RFQ is coupled to the existing surface ionization ion source providing high intensity ion bunches (up to 107 ions per bunch) towards the pulsed drift tube and the Penning traps of WITCH. This achievement allows for loading and tuning of the Penning traps in the domain of space charge limits and grants off-line operation independently of the REX-ISOLDE ion source. The current upgrade allows for a more thorough and frequent testing with bunched stable ion beams of high intensities, which will be used for studying various systematic effects involved in experiments with radioactive ions.

  17. Radio continuum emission and HI gas accretion in the NGC 5903/5898 compact group of galaxies

    NASA Astrophysics Data System (ADS)

    Wiita, Paul; Gopal-Krishna; Mhaskey, Mukul

    2012-03-01

    We investigate the nature of the multi-component radio continuum and HI emission associated with the nearby galaxy group comprised of two dominant ellipticals, NGC 5898 and NGC 5903 and a dwarf lenticular ESO514-G003. Striking new details of radio emission come from the ongoing TIFR.GMRT.SKY.SURVEY (TGSS) which provides images with a resolution of ˜24^'' x18^'' and rms noise of 5 mJy at 150 MHz. Previous observations of this compact triplet include images at higher frequencies of the radio continuum as well as huge HI trails originating from the vicinity of NGC 5903. The TGSS 150 MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf SO galaxy ESO514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (α˜-1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the HI trails. Both its radio loud members are also the only galaxies that are seen to be connected to an HI filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  18. Development of a radio-astrometric catalog by means of very long baseline interferometry observations

    NASA Technical Reports Server (NTRS)

    Fanselow, J. L.; Sovers, O. J.; Thomas, J. B.; Bletzacker, F. R.; Kearns, T. J.; Cohen, E. J.; Purcell, G. H., Jr.; Rogstad, D. H.; Skjerve, L. J.; Young, L. E.

    1981-01-01

    The Jet Propulsion Laboratory has been developing a radio-astrometric catalogue for use in the application of radio interferometry to interplanetary navigation and geodesy. The catalogue consists of approximately 100 compact extragalactic radio sources whose relative positions have formal uncertainties of the order of 0.01 arcsec. The sources cover nearly all of the celestial sphere above -40 deg declination. By using the optical counterparts of many of these radio sources, this radio reference frame has been tied to the FK4 optical system with a global accuracy of approximately 0.1 arcsec. This paper describes the status of this work.

  19. Extending the ICRF to Higher Radio Frequencies: 24 and 43 GHz Astrometry

    NASA Technical Reports Server (NTRS)

    Jacobs, Christopher S.; Charlot, Patrick; Fomalont, Ed B.; Gordon, David; Lanyi, Gabor E.; Ma, Chopo; Naudet, Charles J.; Sovers, Ojars J.; Zhang, Li-Wei D.

    2004-01-01

    We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-band) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

  20. Extending the ICRF to Higher Radio Frequencies: Imaging and Source Structure

    NASA Technical Reports Server (NTRS)

    Boboltz, David A.; Fey, Alan L.; Charlot, Patrick; Fomalont, Edward B.; Lanyi, Gabor E.; Zhang, Li-Wei

    2004-01-01

    We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-braid) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

  1. A review of decametric radio astronomy - Instruments and science

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.; Cane, H. V.

    1987-01-01

    The techniques and instruments used in Galactic and extragalactic radio astronomy at dkm wavelengths are surveyed, and typical results are summarized. Consideration is given to the large specialized phased arrays used for early surveys, the use of wideband elements to increase frequency agility, experimental VLBI observations, and limitations on ground-based observations below about 10 MHz (where the proposed LF Space Array, with resolution 0.5-5 arcmin, could make a major contribution). Observations discussed cover the Galactic center, the Galactic background radiation, SNRs, compact Galactic sources, the ISM, and large extragalactic sources.

  2. Estimating extragalactic Faraday rotation

    NASA Astrophysics Data System (ADS)

    Oppermann, N.; Junklewitz, H.; Greiner, M.; Enßlin, T. A.; Akahori, T.; Carretti, E.; Gaensler, B. M.; Goobar, A.; Harvey-Smith, L.; Johnston-Hollitt, M.; Pratley, L.; Schnitzeler, D. H. F. M.; Stil, J. M.; Vacca, V.

    2015-03-01

    Observations of Faraday rotation for extragalactic sources probe magnetic fields both inside and outside the Milky Way. Building on our earlier estimate of the Galactic contribution, we set out to estimate the extragalactic contributions. We discuss the problems involved; in particular, we point out that taking the difference between the observed values and the Galactic foreground reconstruction is not a good estimate for the extragalactic contributions. We point out a degeneracy between the contributions to the observed values due to extragalactic magnetic fields and observational noise and comment on the dangers of over-interpreting an estimate without taking into account its uncertainty information. To overcome these difficulties, we develop an extended reconstruction algorithm based on the assumption that the observational uncertainties are accurately described for a subset of the data, which can overcome the degeneracy with the extragalactic contributions. We present a probabilistic derivation of the algorithm and demonstrate its performance using a simulation, yielding a high quality reconstruction of the Galactic Faraday rotation foreground, a precise estimate of the typical extragalactic contribution, and a well-defined probabilistic description of the extragalactic contribution for each data point. We then apply this reconstruction technique to a catalog of Faraday rotation observations for extragalactic sources. The analysis is done for several different scenarios, for which we consider the error bars of different subsets of the data to accurately describe the observational uncertainties. By comparing the results, we argue that a split that singles out only data near the Galactic poles is the most robust approach. We find that the dispersion of extragalactic contributions to observed Faraday depths is most likely lower than 7 rad/m2, in agreement with earlier results, and that the extragalactic contribution to an individual data point is poorly

  3. mJIVE-20: A survey for compact mJy radio objects with the very long baseline array

    SciTech Connect

    Deller, A. T.; Middelberg, E.

    2014-01-01

    We present the description and early results of the mJy Imaging VLBA Exploration at 20 cm (mJIVE-20). mJIVE-20 is a large project on the Very Long Baseline Array which is systematically inspecting a large sample of mJy radio sources, pre-selected from the Faint Images of the Radio Sky at Twenty cm (FIRST) survey made with the Very Large Array, to identify any compact emission that may be present. The survey is being undertaken using filler time on the VLBA, which utilizes short segments scheduled in bad weather and/or with a reduced number of antennas, during which no highly rated science projects can be scheduled. The newly available multifield capability of the VLBA makes it possible for us to inspect of the order of 100 sources per hour of observing time with a 6.75σ detection sensitivity of approximately 1 mJy beam{sup –1}. The results of the mJIVE-20 survey are made publicly available as soon as the data are calibrated. After 18 months of observing, over 20,000 FIRST sources have been inspected, with 4336 very long baseline interferometry detections. These initial results suggest that within the range 1-200 mJy, fainter sources are somewhat more likely to be dominated by a very compact component than brighter sources. Over half of all arcsecond-scale mJy radio sources contain a compact component, although the fraction of sources that are dominated by milliarcsecond scale structure (where the majority of the arcsecond scale flux is recovered in the mJIVE-20 image) is smaller at around 30%-35%, increasing toward lower flux densities. Significant differences are seen depending on the optical classification of the source. Radio sources with a stellar/point-like counterpart in the Sloan Digital Sky Survey (SDSS) are more likely to be detected overall, but this detection likelihood appears to be independent of the arcsecond-scale radio flux density. The trend toward higher radio compactness for fainter sources is confined to sources that are not detected in SDSS

  4. PKS B1718-649: An H I and H2 perspective on the birth of a compact radio source

    NASA Astrophysics Data System (ADS)

    Maccagni, F. M.; Santoro, F.; Morganti, R.; Oosterloo, T. A.; Oonk, J. B. R.; Emonts, B. H. C.

    2016-02-01

    We present neutral hydrogen (H I) and warm molecular hydrogen (H2) observations of the young (102 yr) radio galaxy PKS B1718-649. We study the morphology and the kinematics of both gas components, focusing, in particular, on their properties in relation to the triggering of the radio activity. The regular kinematics of the large scale H I disk, seen in emission, suggests that an interaction event occurred too long ago to be responsible for the recent triggering of the radio activity. In absorption, we detect two absorption lines along the narrow line of sight of the compact ({r<2} pc) radio source. The lines trace two clouds with opposite radial motions. These may represent a population of clouds in the very inner regions of the galaxy, which may be involved in triggering the radio activity. The warm molecular hydrogen (H 2 1-0 S(1) ro-vibrational line) in the innermost kilo-parsec of the galaxy appears to be distributed in a circum-nuclear disk following the regular kinematics of the H I and of the stellar component. An exception to this behaviour arises only in the very centre, where a highly dispersed component is detected. These particular H I and H2 features suggest that a strong interplay between the radio source and the surrounding ISM is ongoing. The physical properties of the cold gas in the proximity of the radio source may regulate the accretion recently triggered in this AGN.

  5. The Extragalactic Ferment

    ERIC Educational Resources Information Center

    MOSAIC, 1978

    1978-01-01

    Discusses the efforts which have been accomplished in extragalactic astronomy (the study of bodies and systems beyond the Milky Way) since 1929. Some of the most perplexing problems of extragalactic astronomy such as the missing mass of the galaxies are also discussed. (HM)

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    Claims for a galactic-latitude dependence of interstellar angular broadening based on interplanetary-scintillation (IPS) observations are investigated. Analysis of the statistics of the angular sizes in an IPS survey shows that there is no evidence for increased angular broadening in the galactic plane. A region of sky about 500 sq deg of arc in area is considered in which significant angular broadening is thought to exist. An association between this region and the nearby North Polar Spur is proposed on the basis of the former's extension off the galactic plane to high latitudes. An evaluation of two-frequency angular-broadening measurements suggests that the data used to support the conclusion about a galactic-latitude dependence are not statistically significant. A study of pulsar data and implications for the angular broadening expected in the interstellar medium for sources at galactic latitudes below + or - 10 deg indicates the possible existence of a previously unsuspected class of compact galactic nonthermal radio sources, designated 'scintars'.

  7. The Shroud around the `Compact, Symmetric' Radio Jets in NGC1052

    NASA Astrophysics Data System (ADS)

    Vermeulen, R. C.; Ros, E.; Kellermann, K. I.; Cohen, M. H.; Zensus, J. A.; van Langevelde, H. J.

    This is a paper on young jet material in a frustratingly complex environment. NGC1052 has a compact, flat or GHz peaked spectrum radio nucleus consisting of bi-symmetric jets, oriented close to the plane of the sky. Many features on both sides move away at υapp~0.26c (H0 = 65kms-1Mpc-1). VLBI at seven frequencies shows a wide range of spectral shapes and brightness temperatures; there is clearly free-free absorption, probably together with synchrotron self-absorption, on both sides of the core. The absorbing structure is likely to be geometrically thick and oriented roughly orthogonal to the jets, but it is patchy. HI VLBI shows atomic gas in front of the approaching as well as the receding jet. There appear to be three velocity systems, at least two of which are local to the AGN environment. The `high velocity system', 125-200kms-1 redward of systemic, seems restricted to a shell 1-2pc away from the core. Closer to the centre, this gas might be largely ionised; it could cause the free-free absorption. WSRT spectroscopy shows 1667 and 1665MHz OH absorption over a wide velocity range. OH and HI profile similarity suggests co-location of molecular and atomic `high velocity' gas; the connection to H2O masing gas is unclear. Further, at `high velocity' we detected the OH 1612MHz satellite line in absorption and the 1720MHz line in emission, with complementary strengths.

  8. Radio Spectra of Selected Compact Sources in the Nucleus of M82

    NASA Astrophysics Data System (ADS)

    Allen, Michael L.; Kronberg, Philipp P.

    1998-07-01

    We have determined detailed radio spectra for 26 compact sources in the starburst nucleus of M82, between 74 and 1.3 cm. Seventeen show low-frequency turnovers. One other has a thermal emission spectrum, and we identify it as an H II region. The low-frequency turnovers result from absorption by interstellar thermal gas in M82. New information on the active galactic nucleus candidate 44.01+595 shows it to have a nonthermal falling power-law spectrum at the highest frequencies and that it is strongly absorbed below 2 GHz. We derive large magnetic fields in the supernova remnants of order (1-2)(1 + k)2/7φ-2/7 mG; hence, large pressures in the sources suggest that the brightest ones are either expanding or are strongly confined by a dense interstellar medium. From the largest source in our sample we derive a supernova rate of 0.016 yr-1.

  9. An Energy-Efficient and Compact Clustering Scheme with Temporary Support Nodes for Cognitive Radio Sensor Networks

    PubMed Central

    Salim, Shelly; Moh, Sangman; Choi, Dongmin; Chung, Ilyong

    2014-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network whose sensor nodes are equipped with cognitive radio capability. Clustering is one of the most challenging issues in CRSNs, as all sensor nodes, including the cluster head, have to use the same frequency band in order to form a cluster. However, due to the nature of heterogeneous channels in cognitive radio, it is difficult for sensor nodes to find a cluster head. This paper proposes a novel energy-efficient and compact clustering scheme named clustering with temporary support nodes (CENTRE). CENTRE efficiently achieves a compact cluster formation by adopting two-phase cluster formation with fixed duration. By introducing a novel concept of temporary support nodes to improve the cluster formation, the proposed scheme enables sensor nodes in a network to find a cluster head efficiently. The performance study shows that not only is the clustering process efficient and compact but it also results in remarkable energy savings that prolong the overall network lifetime. In addition, the proposed scheme decreases both the clustering overhead and the average distance between cluster heads and their members. PMID:25116905

  10. An energy-efficient and compact clustering scheme with temporary support nodes for cognitive radio sensor networks.

    PubMed

    Salim, Shelly; Moh, Sangman; Choi, Dongmin; Chung, Ilyong

    2014-01-01

    A cognitive radio sensor network (CRSN) is a wireless sensor network whose sensor nodes are equipped with cognitive radio capability. Clustering is one of the most challenging issues in CRSNs, as all sensor nodes, including the cluster head, have to use the same frequency band in order to form a cluster. However, due to the nature of heterogeneous channels in cognitive radio, it is difficult for sensor nodes to find a cluster head. This paper proposes a novel energy-efficient and compact clustering scheme named clustering with temporary support nodes (CENTRE). CENTRE efficiently achieves a compact cluster formation by adopting two-phase cluster formation with fixed duration. By introducing a novel concept of temporary support nodes to improve the cluster formation, the proposed scheme enables sensor nodes in a network to find a cluster head efficiently. The performance study shows that not only is the clustering process efficient and compact but it also results in remarkable energy savings that prolong the overall network lifetime. In addition, the proposed scheme decreases both the clustering overhead and the average distance between cluster heads and their members. PMID:25116905

  11. Fermi/LAT Observations of Swift/BAT Seyfert Galaxies: On the Contribution of Radio-Quiet Active Galactic Nuclei to the Extragalactic gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Mushotzky, Richard F.; Sambruna, Rita M.; Davis, David S.; Reynolds, Christopher S.

    2011-01-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R(sub X,BAT) where radio-loud objects have logR(sub X,BAT) > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be approx.2x10(exp -11) photons/sq cm/s, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the gamma-ray (1-100 GeV) luminosity of < approx.3x10(exp 41) erg/s. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  12. FERMI/LAT OBSERVATIONS OF SWIFT/BAT SEYFERT GALAXIES: ON THE CONTRIBUTION OF RADIO-QUIET ACTIVE GALACTIC NUCLEI TO THE EXTRAGALACTIC {gamma}-RAY BACKGROUND

    SciTech Connect

    Teng, Stacy H.; Mushotzky, Richard F.; Reynolds, Christopher S.; Sambruna, Rita M.; Davis, David S.

    2011-12-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R{sub X,BAT} where radio-loud objects have log R{sub X,BAT} > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be {approx}2 Multiplication-Sign 10{sup -11} photons cm{sup -2} s{sup -1}, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the {gamma}-ray (1-100 GeV) luminosity of {approx}< 3 Multiplication-Sign 10{sup 41} erg s{sup -1}. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  13. Discovery of New Faint Radio Emission on 8° to 3' Scales in the Coma Field, and Some Galactic and Extragalactic Implications

    NASA Astrophysics Data System (ADS)

    Kronberg, P. P.; Kothes, R.; Salter, C. J.; Perillat, P.

    2007-04-01

    We present a deep, 8° diameter, 0.4 GHz radio image using a first-time combination of the NAIC Arecibo 305 m telescope in Puerto Rico and the wide-angle interferometer at the Dominion Radio Astrophysical Observatory at Penticton, Canada. Our observations are centered on the Coma Cluster of galaxies in the ``Great Wall'' of galaxies near the north Galactic pole. The complementary nature of these two instruments enables us to produce a distortion-free image that is sensitive to radiation on scales from 8° down to that of an individual galaxy halo at the 100 Mpc distance of the Great Wall. Newly revealed patches of distributed radio ``glow'' are seen well above the detection limit. One prominent such area coincides with groupings of radio galaxies near the Coma Cluster and indicates intergalactic magnetic fields in the range 0.2-0.4 μG on scales of up to ~4 Mpc. Other patches of diffuse emission, not previously explored at these high latitudes on arcminute scales, probably consist of Galactic ``cirrus.'' A striking anticorrelation is found between low-level diffuse radio glow and some regions of enhanced optical galaxy surface density, suggesting that cosmological large-scale structure, normally defined by the baryonic (or dark) matter density, is not uniquely traced by faint continuum radio glow. Rather, intergalactic diffuse synchrotron radiation may be a proxy for IGM cosmic-ray and magnetic energy density, rather than matter density. The diffuse, arcminute-level structures over a large region of sky are potentially important pathfinders to CMB foreground radiation on high multipole scales.

  14. Bidirectional motion observed in the compact symmetric object 1946+708.

    PubMed Central

    Taylor, G B; Vermeulen, R C; Pearson, T J

    1995-01-01

    We present the first direct measurements of bidirectional motions in an extragalactic radio jet. The radio source 1946+708 is a compact symmetric object with striking S-symmetry identified with a galaxy at a redshift of 0.101. From observations 2 years apart we have determined the velocities of four compact components in the jet, the fastest of which has an apparent velocity of 1.09 h-1c. By pairing up the components, assuming they were simultaneously ejected in opposite directions, we derive a 1 lower limit on the Hubble constant, H0 > 42 km.s-1.Mpc-1. PMID:11607603

  15. Singular-Spectrum Analysis and Wavelet Analysis of the Variability of the Extragalactic Radio Sources 3C 120 and CTA 102

    NASA Astrophysics Data System (ADS)

    Donskikh, G. I.; Ryabov, M. I.; Sukharev, A. L.; Aller, M.

    2016-06-01

    This is a study of the variability of the fluxes of radio emission from the quasar CTA 102 and the radio galaxy 3C 120 based on data from the University of Michigan Radio Astronomy Observatory (UMRAO, Ann Arbor). The data were obtained at three frequencies (14.5, 8, and 4.8 GHz) with the 26-m radio telescope. Two mutually complementary methods were used for the analysis: wavelet analysis and singular spectrum analysis. Wavelet analysis is based on the Fourier transform, while singular-spectrum analysis does not use an analyzing function. Long-duration components of the variability in the range of ~4-11 years were found for 3C 120 and ~1.5-3 years, for CTA 102. The short-duration components of the variability are characterized by periods of ~0.7-3.4 years for 3C 120 and ~0.5-0.8 years for CTA 102. These data were also compared with VLBI charts from the MOJAVE archive for studying the evolution of the components in the jets of the quasars studied here.

  16. 86 GHz VLBI survey of Ultra compact radio emission in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan Nair, Dhanya; Lobanov, Andrei; Ros, Eduardo; Krichbaum, Thomas; Zensus, Anton

    2016-07-01

    Very Long Baseline Interferometry (VLBI) observations at 86 GHz reach a resolution of about 50 μas and sample the scales as small as 10 ^{3} - 10 ^{4} Schwartzchild radii of the central black hole in Active Galactic Nuclei (AGN), and uncover the jet regions where acceleration and collimation of the relativistic flow takes place. The high resolution millimetre VLBI studies makes it possible to look deeper into the core and inner jets of AGN which is invisible at centimetre and longer wavelengths due to self absorption or free-free absorption by the torus. We have done a large global VLBI survey of 162 unique ultra compact radio sources at 86 GHz (˜3 mm) conducted in 2010 - 2011. All the sources were detected and imaged; increasing by a factor of ˜2, the total number of AGN ever imaged with VLBI at 86 GHz. The survey data attained a baseline sensitivity of 0.1 Jy and the image sensitivity of 5 mJy/beam. We have used Gaussian model fitting to represent the structure of the observed sources and to estimate the flux densities and sizes of the core and jet components. The model fitting yields estimates of the brightness temperature (T _{b}) of the VLBI bright core (base) of the jet and inner jet components of AGN, taking into account the resolution limits of the data at 3 mm.The brightness temperatures of the VLBI cores peak at ˜10 ^{11} K. We have applied a basic population model with a single value of intrinsic brightness temperature,T _{o}, in order to reproduce the observed distribution of T _{b}. Our data are consistent with a population of sources that have T _{o} ˜(1-7)×10 ^{11} K in the VLBI cores and T _{o} ≤ 5 ×10 ^{10} K in the jets. We also find a correlation between the brightness temperatures obtained from the model fits with estimates of the brightness temperature limits made directly from the visibility data. For objects with sufficient structural detail detected, we investigated the effect of adiabatic energy losses on the evolution of

  17. Compact field programmable gate array-based pulse-sequencer and radio-frequency generator for experiments with trapped atoms.

    PubMed

    Pruttivarasin, Thaned; Katori, Hidetoshi

    2015-11-01

    We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz. PMID:26628171

  18. Compact field programmable gate array-based pulse-sequencer and radio-frequency generator for experiments with trapped atoms

    SciTech Connect

    Pruttivarasin, Thaned; Katori, Hidetoshi

    2015-11-15

    We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz.

  19. Extragalactic Gravitational Collapse

    NASA Astrophysics Data System (ADS)

    Rees, Martin J.

    After some introductory "numerology", routes towards black hole formation are briefly reviewed; some properties of black holes relevant to theories for active galactic nuclei are then described. Applications are considered to specific models for energy generation and the production of relativistic beams. The paper concludes with a discussion of extragalactic sources of gravitational waves.

  20. The impact of compact radio sources on their host galaxies: observations

    NASA Astrophysics Data System (ADS)

    Tadhunter, C.

    2016-02-01

    I review the observational evidence that CSS/GPS radio sources have a significant impact on the evolution of their host galaxies, particularly on the kpc-scales of the galaxy bulges. Starting with an overview of the observational evidence for jet-cloud interactions and warm ionised outflows in CSS/GPS sources, I then consider the challenges involved in quantifying the feedback effect of the warm outflows in terms of their mass outflow rates and kinetic powers. For the best-observed cases it is shown that the warm outflows may have a major negative feedback effect in the very central regions, but probably lack the power to heat and eject the full cool ISM contents of the host galaxies. In contrast, the recently-discovered neutral and molecular outflows are more massive and powerful and therefore carry more destructive potential. However, the feedback effect of such outflows is not necessarily negative: there is now clear observational evidence that the molecular outflows are formed as the hot, compressed gas cools behind fast shocks driven into the ISM by the relativistic jets. The natural endpoint of this process is the formation of stars. Therefore, jet-induced star formation may be a significant process in CSS/GPS radio galaxies. Finally, I discuss whether CSS/GPS sources are ``imposters'' in flux-limited radio samples, due the flux boosting of the radio sources by strong jet-cloud interactions in the early stages of radio source evolution.

  1. Planck on Radio Sources: Data and Findings

    NASA Astrophysics Data System (ADS)

    Partridge, Robert Bruce

    2015-08-01

    Planck scanned the entire sky every six months at nine frequency bands from 28 to 857 GHz with enough sensitivity to detect over a thousand extragalactic radio sources. It thus provides measurements of the mm and sub-mm spectra of these sources in a regular cadence, even at wavelengths hard to observe from the ground. Polarization measurements (or upper limits) are provided for brighter sources at 28-353 GHz. Finally, Planck is calibrated to <1% accuracy in most of its frequency bands.I will first introduce the valuable data set Planck provides on extragalactic sources, in particular the Second Planck Catalogue of Compact Sources (PCCS2), then more briefly describe some of the scientific conclusions drawn from the Planck measurments.

  2. High Resolution Rapid Response Observations of Compact Radio Sources with the Ceduna Hobart Interferometer (CHI)

    NASA Technical Reports Server (NTRS)

    Blanchard, Jay M.; Lovell, James E. J.; Ojha, Roopesh; Kadler, Matthias; Dickey, John M.; Edwards, Philip G.

    2011-01-01

    Context. Frequent, simultaneous observations across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including Active Galactic Nuclei. A key tool of such studies is the ability to observe an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific observational procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer. that can rapidly observe a flaring object. This is the only facility that is dedicated to rapid high resolution radio observations of an object south of -30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at y-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our observing strategy within half an hour of a triggering event. These observations can be calibrated with amplitude errors better than 20%. Lower limits to the brightness temperatures of the sources can also be calculated using CHI. Key words. instrumentation:interferometers - galaxies:active - galaxies:jets - galaxies:nuclei quasars:general gamma rays:galaxies- 1.

  3. EVN detection of a compact radio source as a counterpart to Fermi J1418+3541

    NASA Astrophysics Data System (ADS)

    Frey, Sandor; Paragi, Zsolt; Gabanyi, Krisztina; An, Tao

    2013-01-01

    Fermi J1418+3541 is a suspected blazar recently detected as a flaring gamma-ray point source, identified with likely radio, optical and infrared counterparts within the Fermi LAT error circle (Dutka et al. 2012, ATEL #4643; Mahabal et al. 2012, ATEL #4645; Bernieri et al. 2013, A&A, in press, arXiv:1212.6868).

  4. Extragalactic Cataclysmic Variables

    NASA Astrophysics Data System (ADS)

    Shara, Michael M.; Neill, James D.

    2005-03-01

    SALT is uniquely poised to make major inroads in the study of extragalactic cataclysmic variables (CVs) - novae and dwarf novae. The ability to search an external galaxy for erupting CVs night after night, for months at a time, AND to obtain confirmatory spectra within a night of discovery is unique and invaluable. We present several examples of multi-week to multi-month searches for extragalactic CVs with 1 to 4 meter-class telescopes. In particular, we have detected the first erupting dwarf novae in the LMC and placed a lower limit on the number of CVs in that galaxy. We have also observed the Local Group dwarf ellipticals M32 and NGC 205 in their entirety every clear night over a 4.5 month interval. In this survey we discovered one nova each in M32 and NGC 205, far more than previous nova surveys led us to expect. A similar search in M81 again reveals more novae than expected, and demonstrates, conclusively, that novae are predominantly a bulge population in spiral galaxies. Finally we report the detection of intergalactic tramp novae in the Fornax cluster, and emphasize that these are valuable tracers of stars stripped from their hosts during galaxy harassment. The insights gained during these preliminary studies illustrate how valuable SALT campaigns on extragalactic CVs will be.

  5. Horizon-scale Lepton Acceleration in Jets: Explaining the Compact Radio Emission in M87

    NASA Astrophysics Data System (ADS)

    Broderick, Avery E.; Tchekhovskoy, Alexander

    2015-08-01

    It has now become clear that the radio jet in the giant elliptical galaxy M87 must turn on very close to the black hole. This implies the efficient acceleration of leptons within the jet at scales much smaller than feasible by the typical dissipative events usually invoked to explain jet synchrotron emission. Here we show that the stagnation surface, the separatrix between material that falls back into the black hole and material that is accelerated outward forming the jet, is a natural site of pair formation and particle acceleration. This occurs via an inverse Compton pair catastrophe driven by unscreened electric fields within the charge-starved region about the stagnation surface and substantially amplified by a post-gap cascade. For typical estimates of the jet properties in M87, we find excellent quantitive agreement between the predicted relativistic lepton densities and those required by recent high-frequency radio observations of M87. This mechanism fails to adequately fill a putative jet from Sagittarius A* with relativistic leptons, which may explain the lack of an obvious radio jet in the Galactic center. Finally, this process implies a relationship between the kinetic jet power and the gamma-ray luminosity of blazars, produced during the post-gap cascade.

  6. Radio continuum emission and H I gas accretion in the NGC 5903/5898 compact group of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Mhaskey, Mukul

    Striking new details of radio emission are unveiled from the 2nd Data Release of the ongoing TIFR.GMRT.SKY.SURVEY (TGSS) which provides images with a resolution of 24'' × 18'' and a typical rms noise of 5 mJy at 150 MHz. Previous radio observations of this compact triplet of galaxies include images at higher frequencies of the radio continuum as well as H I emission, the latter showing huge H I trails originating from the vicinity of NGC 5903 where H I is in a kinematically disturbed state. The TGSS 150 MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf SO galaxy ESO514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (alpha -1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the H I trails. Another noteworthy aspect of this triplet of early-type galaxies highlighted by the present study is that both its radio loud members, namely NGC 5903 and ESO514-G003, are also the only galaxies that are seen to be connected to an H I filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  7. Compact floating ion energy analyzer for measuring energy distributions of ions bombarding radio-frequency biased electrode surfaces

    NASA Astrophysics Data System (ADS)

    Edelberg, Erik A.; Perry, Andrew; Benjamin, Neil; Aydil, Eray S.

    1999-06-01

    A compact floating retarding-field ion energy analyzer and the accompanying electronics have been designed and built to measure the energy distribution of ions bombarding radio-frequency (rf) biased electrodes in high-density plasma reactors. The design consists of two main components, a compact retarding field vacuum probe and an integrated stack of floating electronics for providing output voltages, measuring currents and voltages and transmitting data to a computer. The operation and capabilities of the energy analyzer are demonstrated through ion energy distribution measurements conducted on a 4 MHz rf-biased electrostatic chuck in a 13.56 MHz high-density transformer coupled plasma (TCP) reactor. The analyzer is capable of operating while floating on several hundreds of volts of rf bias and at pressures up to 30 mTorr without differential pumping. The effects of pressure (2-30 mTorr), TCP power (500-1500 W), rf-bias power (0-800 W), gas composition, and ion mass on the ion energy distributions are demonstrated through Ar, Ne, and Ar/Ne discharges.

  8. Columbia/Einstein observations of extragalactic X-ray sources

    NASA Technical Reports Server (NTRS)

    Ku, W. H. M.

    1979-01-01

    Results are presented of the analysis of data from observations of extragalactic objects with the imaging proportional counter on board the Einstein Observatory. Surveys of normal galaxies, radio galaxies, active galaxies, quasars and BL Lacs, and clusters of galaxies were studied in order to improve the understanding of the origin of the Milky Way Galaxy.

  9. BROADBAND JET EMISSION IN YOUNG AND POWERFUL RADIO SOURCES: THE CASE OF THE COMPACT STEEP SPECTRUM QUASAR 3C 186

    SciTech Connect

    Migliori, Giulia; Siemiginowska, Aneta; Celotti, Annalisa

    2012-04-20

    We present the X-ray analysis of a deep ({approx}200 ks) Chandra observation of the compact steep spectrum radio-loud quasar 3C 186 (z = 1.06) and investigate the contribution of the unresolved radio jet to the total X-ray emission. The spectral analysis is not conclusive on the origin of the bulk of the X-ray emission. In order to examine the jet contribution to the X-ray flux, we model the quasar spectral energy distribution, adopting several scenarios for the jet emission. For the values of the main physical parameters favored by the observables, a dominant role of the jet emission in the X-ray band is ruled out when a single-zone (leptonic) scenario is adopted, even including the contribution of the external photon fields as seed photons for inverse Compton emission. We then consider a structured jet, with the blazar component that-although not directly visible in the X-ray band-provides an intense field of seed synchrotron photons Compton-scattered by electrons in a mildly relativistic knot. In this case, the whole X-ray emission can be accounted for if we assume a blazar luminosity within the range observed from flat spectrum radio quasars. The X-ray radiative efficiency of such a (structured) jet is intimately related to the presence of a complex velocity structure. The jet emission can provide a significant contribution in X-rays if it decelerates within the host galaxy on kiloparsec scales. We discuss the implications of this model in terms of jet dynamics and interaction with the ambient medium.

  10. X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta; Janiuk, Agnieszka

    2009-11-10

    We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jet can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.

  11. The extragalactic distance scale

    NASA Astrophysics Data System (ADS)

    Rowan-Robinson, Michael

    1988-03-01

    Recent advances in the determination of the extragalactic distance scale are discussed, reviewing the results of observational and theoretical investigations from the period 1983-1987. Consideration is given to the galactic calibration of the Cepheids, the extension of the nova method to the Virgo cluster, improvements in the supernova distance method, the reasons why the Tully-Fisher method gives distances shorter than those of other techniques, and a modified Faber-Jackson distance method for elliptical galaxies. Numerical results are compiled in extensive tables and graphs, and it is concluded that only minor corrections to the cosmological distance ladder of Rowan-Robinson (1985) are required.

  12. Extragalactic origin of antiprotons

    NASA Technical Reports Server (NTRS)

    Stephens, S. A.; Golden, R. L.

    1989-01-01

    The effect of Galactic modulation on cosmic rays entering the Galaxy from outside has been studied for two different models for the confinement of cosmic rays, using a one-dimensional transport equation. From this study, the role of extragalactic cosmic rays has been examined critically in the context of the recent data on antiprotons. It is concluded that they are not a significant source of cosmic ray antiprotons. However, determination of the energy spectrum of antiprotons at least up to a few tens of GeV would provide information on the modulation of cosmic rays, while entering the Galaxy from outside.

  13. The compact radio structure of the high-redshift quasar OQ172

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Jiang, D. R.; Gu, M.; Gurvits, L. I.

    2016-02-01

    The GHz-Peaked Spectrum (GPS) quasar OQ172 (J1445+0958) has an extremely high rest-frame rotation measure (RM > 20 000 rad m-2) and an RM gradient in its inner nucleus. Its jet observed with Very Long Baseline Interferometry (VLBI) is strongly bent along an arc spanning > 100 pc. Near infrared (NIR) spectra reveal an unusually large [O III] line width which suggests a large mass within the NLR and/or strong interactions between the emerging jet and the dense material therein. We present our VLBI Space Observatory Programme (VSOP) and Multi-frequency Very Long Baseline Array (VLBA) observation of the GPS quasar OQ172. The observations will help us to explore the VLBI radio properties and to better understand the circumnuclear environment of OQ172.

  14. The BL LAC phenomenon: X-ray observations of transition objects and determination of the x-ray spectrum of a complete sample of flat-spectrum radio sources

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    1994-01-01

    This report summarizes the activities related to two ROSAT investigations: (1) x-ray properties of radio galaxies thought to contain BL Lac type nuclei; and (2) x-ray spectra of a complete sample of flat-spectrum radio sources. The following papers describing the research are provided as attachments: Multiple X-ray Emission Components in Low Power Radio Galaxies; New X-ray Results on Radio Galaxies; Analysis Techniques for a Multiwavelength Study of Radio Galaxies; Separation of X-ray Emission Components in Radio Galaxies; X-ray Emission in Powerful Radio Galaxies and Quasars; Extended and Compact X-ray Emission in Powerful Radio Galaxies; and X-ray Spectra of a Complete Sample of Extragalactic Core-dominated Radio Sources.

  15. The large-scale radio structure of R Aquarii

    NASA Technical Reports Server (NTRS)

    Hollis, J. M.; Michalitsianos, A. G.; Oliversen, R. J.; Yusef-Zadeh, F.; Kafatos, M.

    1987-01-01

    Radio continuum observations of the R Aqr symbiotic star system, using the compact D configuration of the VLA at 6-cm wavelength, reveal a large-scale about 2-arcmin structure engulfing the binary, which has long been known to have a similar optical nebula. This optical/radio nebula possesses about 4 x 10 to the 42nd ergs of kinetic energy which is typical of a recurrent nova outburst. Moreover, a cluster of a dozen additional 6-cm radio sources were observed in proximity to R Aqr, most of these discrete sources lie about 3 arcmin south and/or west of R Aqr and, coupled with previous 20-cm data, spectral indices limits suggest a thermal nature for some of these sources. If the thermal members of the cluster are associated with R Aqr, it may indicate a prehistoric eruption of the system's suspected recurrent nova. The nonthermal cluster members may be extragalactic background radio sources.

  16. Electronic Catalog Of Extragalactic Objects

    NASA Technical Reports Server (NTRS)

    Helou, George; Madore, Barry F.

    1993-01-01

    NASA/IPAC Extragalactic Database (NED) is publicly accessible computerized catalog of published information about extragalactic observations. Developed to accommodate increasingly large sets of data from surveys, exponentially growing literature, and trend among astronomers to take multispectral approach to astrophysical problems. Accessible to researchers and librarians.

  17. Radio continuum emission and H I gas accretion in the NGC 5903/5898 compact group of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Gopal-Krishna; Mhaskey, Mukul; Wiita, Paul J.; Sirothia, S. K.; Kantharia, N. G.; Ishwara-Chandra, C. H.

    2012-06-01

    We discuss the nature of the multicomponent radio continuum and H I emission associated with the nearby galaxy group comprised of two dominant ellipticals, NGC 5898 and NGC 5903, and a dwarf lenticular ESO 514-G003. Striking new details of radio emission are unveiled from the second Data Release of the ongoing TIFR GMRT Sky Survey (TGSS) which provides images with a resolution of ˜24 × 18 arcsec2 and a typical rms noise of 5 mJy at 150 MHz. Previous radio observations of this compact triplet of galaxies include images at higher frequencies of the radio continuum as well as H I emission, the latter showing huge H I trails originating from the vicinity of NGC 5903 where H I is in a kinematically disturbed state. The TGSS 150-MHz image has revealed a large asymmetric radio halo around NGC 5903 and also established that the dwarf S0 galaxy ESO 514-G003 is the host to a previously known bright double radio source. The radio emission from NGC 5903 is found to have a very steep radio spectrum (α˜-1.5) and to envelope a network of radio continuum filaments bearing a spatial relationship to the H I trails. Another noteworthy aspect of this triplet of early-type galaxies highlighted by the present study is that both its radio-loud members, namely NGC 5903 and ESO 514-G003, are also the only galaxies that are seen to be connected to an H I filament. This correlation is consistent with the premise that cold gas accretion is of prime importance for triggering powerful jet activity in the nuclei of early-type galaxies.

  18. High performance tunable slow wave elements enabled with nano-patterned permalloy thin film for compact radio frequency applications

    NASA Astrophysics Data System (ADS)

    Farid Rahman, B. M.; Divan, Ralu; Zhang, Hanqiao; Rosenmann, Daniel; Peng, Yujia; Wang, Xuehe; Wang, Guoan

    2014-05-01

    Slow wave elements are promising structures to design compact RF (radio frequency) and mmwave components. This paper reports a comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS). New techniques including the use of defected ground structure and the different signal conductor shape have been implemented to achieve higher slow wave effect with comparative loss. Results show that over 42% and 35% reduction in length is reported in the expense of only 0.3 dB and 0.1 dB insertion loss, respectively, which can end up with 66% and 58% area reduction for the design of a branch line coupler. Implementation of the sub micrometer patterned Permalloy (Py) thin film on top of the simple SWS has been demonstrated for the first time to increase the slow wave effect. Comparing with the traditional slow wave structure, with 100 nm thick Py patterns, the inductance per unit length of the SWS has been increased from 879 nH/m to 963 nH/m. The slow wave effect of the designed structure is also tunable by applied DC current. Measured results have shown that the phase shift can be changed from 94° to 90.5° by applying 150 mA DC current. This provides a solution in designing RF passive components which can work in multiple frequency bands.

  19. VizieR Online Data Catalog: Compact radio sources within 30" of Sgr A* (Yusef-Zadeh+, 2015)

    NASA Astrophysics Data System (ADS)

    Yusef-Zadeh, F.; Bushouse, H.; Schodel, R.; Wardle, M.; Cotton, W.; Roberts, D. A.; Nogueras-Lara, F.; Gallego-Cano, E.

    2016-04-01

    We obtained two sets of A-array observations with the Karl G. Jansky Very Large Array (VLA). The first set of observations of the stellar cluster at the Galactic center were obtained on 2011 July 8-9 and 2011 August 31-September 1 at 44GHz (program 11A-224). Further details of these first-epoch observations are given in Yusef-Zadeh et al. (2014ApJ...792L...1Y). We reobserved the region within 30" of Sgr A* on 2014 February 21, again using the VLA in its A-configuration at 44GHz. We also carried out A-array observations (program 14A-232) in the Ka (9mm) band on 2014 March 9 at 34.5GHz. We searched for NIR counterparts to compact radio sources using high-angular resolution AOs assisted imaging observations acquired with the VLT/NACO (NAos-COnica). A Ks-band (central wavelength 2.18um) image was obtained in a rectangular dither pattern on 2012 September 12. L'-band (3.8um) observations were obtained during various observing runs between 2012 June and September. (1 data file).

  20. New Limits on Extragalactic Magnetic Fields from Rotation Measures.

    PubMed

    Pshirkov, M S; Tinyakov, P G; Urban, F R

    2016-05-13

    We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields. PMID:27232014

  1. New Limits on Extragalactic Magnetic Fields from Rotation Measures

    NASA Astrophysics Data System (ADS)

    Pshirkov, M. S.; Tinyakov, P. G.; Urban, F. R.

    2016-05-01

    We take advantage of the wealth of rotation measures data contained in the NRAO VLA Sky Survey catalog to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic magnetic field contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-α clouds. Based on the observation that rotation measures from distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Jeans' length coherence length to be below 1.7 nG at the 2 σ level, and fields coherent across the entire observable Universe below 0.65 nG. These limits do not depend on the particular origin of these cosmological fields.

  2. Extragalactic HI surveys

    NASA Astrophysics Data System (ADS)

    Giovanelli, Riccardo; Haynes, Martha P.

    2015-12-01

    We review the results of HI line surveys of extragalactic sources in the local Universe. In the last two decades major efforts have been made in establishing on firm statistical grounds the properties of the HI source population, the two most prominent being the HI Parkes All Sky Survey and the Arecibo Legacy Fast ALFA survey. We review the choices of technical parameters in the design and optimization of spectro-photometric "blind" HI surveys, which for the first time produced extensive HI-selected data sets. Particular attention is given to the relationship between optical and HI populations, the differences in their clustering properties and the importance of HI-selected samples in contributing to the understanding of apparent conflicts between observation and theory on the abundance of low mass halos. The last section of this paper provides an overview of currently ongoing and planned surveys which will explore the cosmic evolution of properties of the HI population.

  3. Probing the intergalactic medium with fast radio bursts

    SciTech Connect

    Zheng, Z.; Ofek, E. O.; Kulkarni, S. R.; Neill, J. D.; Juric, M.

    2014-12-10

    The recently discovered fast radio bursts (FRBs), presumably of extragalactic origin, have the potential to become a powerful probe of the intergalactic medium (IGM). We point out a few such potential applications. We provide expressions for the dispersion measure and rotation measure as a function of redshift, and we discuss the sensitivity of these measures to the He II reionization and the IGM magnetic field. Finally, we calculate the microlensing effect from an isolated, extragalactic stellar-mass compact object on the FRB spectrum. The time delays between the two lensing images will induce constructive and destructive interference, leaving a specific imprint on the spectra of FRBs. With a high all-sky rate, a large statistical sample of FRBs is expected to make these applications feasible.

  4. Ground-based astrometry with the ASPHO: optical-radio reference systems connection.

    NASA Astrophysics Data System (ADS)

    Martin, V. A. F.; Leister, N. V.; Poppe, P. C. R.; Brito, A. A.; Mattos, L.

    2003-11-01

    Precise positions and proper motions of optical counterparts of radiostars are needed in order to determine a direct link between the radio reference frame (VLBI - Very long Baseline Interferometry) and the ground-based optical reference frame (based on fundamental stars) (Poma & Zanzu 1991, Kovalevsky 1990, Walter et al. 1990). The basic problems are concerning with the optical-radio systems connection and the quick deterioration that he Hipparcos system is subjected. Thus, there is a request of exact and systematic observations with the instruments in the Earth (Kovalevsky 1990). Radiostars are suitable intermediaries for linking optical stellar reference frame to the quasi-inertial radio reference frame (RRF) represented by compact extragalactic radio sources. With the goal of the connection radio-optical reference frames the observational programme has included a total of 36 radiostars.

  5. Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Caccianiga, A.; Foschini, L.; Peterson, B. M.; Mathur, S.; Terreran, G.; Ciroi, S.; Congiu, E.; Cracco, V.; Frezzato, M.; La Mura, G.; Rafanelli, P.

    2016-06-01

    Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of γ-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.

  6. The prevalence of supernova remnants among unidentified Galactic radio sources

    NASA Technical Reports Server (NTRS)

    Helfand, David J.; Velusamy, T.; Becker, R. H.; Lockman, Felix J.

    1989-01-01

    Nine Galactic radio sources were mapped to identify new Crab-like and composite supernova remnants. The sources were selected on the basis of existing stringent upper limits on their hydrogen recombination line fluxes. One new Cracb-like remnant, one new composite remnant, at least one, and probably two, new shell-like remnants, and a compact H II region were found, along with the expected collection of extragalactic objects. The results suggest that there are several hundred SNRs in the Galaxy which are detectable with current instruments, but which have yet to be identified.

  7. MARBLE (Multiple Antenna Radio-interferometry for Baseline Length Evaluation): Development of a Compact VLBI System for Calibrating GNSS and Electronic Distance Measurement Devices

    NASA Astrophysics Data System (ADS)

    Ichikawa, R.; Ishii, A.; Takiguchi, H.; Kimura, M.; Sekido, M.; Takefuji, K.; Ujihara, H.; Hanado, Y.; Koyama, Y.; Kondo, T.; Kurihara, S.; Kokado, K.; Kawabata, R.; Nozawa, K.; Mukai, Y.; Kuroda, J.; Ishihara, M.; Matsuzaka, S.

    2012-12-01

    We are developing a compact VLBI system with a 1.6-m diameter aperture dish in order to provide reference baseline lengths for calibration. The reference baselines are used to validate surveying instruments such as GPS and EDM and is maintained by the Geospatial Information Authority of Japan (GSI). The compact VLBI system will be installed at both ends of the reference baseline. Since the system is not sensitive enough to detect fringes between the two small dishes, we have designed a new observation concept including one large dish station. We can detect two group delays between each compact VLBI system and the large dish station based on conventional VLBI measurement. A group delay between the two compact dishes can be indirectly calculated using a simple equation. We named the idea "Multiple Antenna Radio-interferometry for Baseline Length Evaluation", or MARBLE system. The compact VLBI system is easy transportable and consists of the compact dish, a new wide-band front-end system, azimuth and elevation drive units, an IF down-converter unit, an antenna control unit (ACU), a counterweight, and a monument pillar. Each drive unit is equipped with a zero-backlash harmonic drive gearing component. A monument pillar is designed to mount typical geodetic GNSS antennas easily and an offset between the GNSS antenna reference point. The location of the azimuth-elevation crossing point of the VLBI system is precisely determined with an uncertainty of less than 0.2 mm. We have carried out seven geodetic VLBI experiments on the Kashima-Tsukuba baseline (about 54 km) using the two prototypes of the compact VLBI system between December 2009 and December 2010. The average baseline length and repeatability of the experiments is 54184874.0 ± 2.4 mm. The results are well consistent with those obtained by GPS measurements. In addition, we are now planning to use the compact VLBI system for precise time and frequency comparison between separated locations.

  8. Very Large Array and Jansky Very Large Array observations of the compact radio sources in M8

    SciTech Connect

    Masqué, Josep M.; Rodríguez, Luis F.; Dzib, Sergio

    2014-12-10

    We analyze high-resolution Very Large Array continuum observations of the M8 region carried out at several epochs that span a period of 30 yr. Our maps reveal two compact sources. One is associated with Her 36 SE, a possible companion of the O7 luminous massive star Her 36, and the other is associated with G5.97–1.17, whose proplyd nature was previously established. Using the analyzed data, we do not find significant time variability in any of these sources. The derived spectral index of ≥0.1 for Her 36 SE, the marginal offset of the radio emission with the previous infrared detection, and the associated X-ray emission previously reported suggest the presence of an unresolved interaction region between the strong winds of Her 36 and Her 36 SE. This region would contribute non-thermal contamination to the global wind emission of Her 36, flattening its spectral index. On the other hand, the emission of G5.97–1.17 can also be explained by a mixture of thermal and non-thermal emission components, with different relative contributions of both emission mechanisms along the proplyd. We argue that the shock created by the photo-evaporation flow of the proplyd with the collimated stellar wind of Her 36 accelerates charged particles in G5.97–1.17, producing considerable synchrotron emission. On the contrary, an electron density enhancement at the southwest of G5.97–1.17 makes the thermal emission dominant over this region.

  9. EXTRAGALACTIC CS SURVEY

    SciTech Connect

    Bayet, E.; Viti, S.; Aladro, R.; MartIn, S.; MartIn-Pintado, J.

    2009-12-10

    We present a coherent and homogeneous multi-line study of the CS molecule in nearby (D < 10 Mpc) galaxies. We include, from the literature, all the available observations from the J = 1-0 to the J = 7-6 transitions toward NGC 253, NGC 1068, IC 342, Henize 2-10, M 82, the Antennae Galaxies, and M 83. We have, for the first time, detected the CS(7-6) line in NGC 253, M 82 (both in the northeast and southwest molecular lobes), NGC 4038, M 83 and tentatively in NGC 1068, IC 342, and Henize 2-10. We use the CS molecule as a tracer of the densest gas component of the interstellar medium in extragalactic star-forming regions, following previous theoretical and observational studies by Bayet et al. In this first paper out of a series, we analyze the CS data sample under both local thermodynamical equilibrium (LTE) and non-LTE (large velocity gradient) approximations. We show that except for M 83 and Overlap (a shifted gas-rich position from the nucleus NGC 4039 in the Antennae Galaxies), the observations in NGC 253, IC 342, M 82-NE, M 82-SW, and NGC 4038 are not well reproduced by a single set of gas component properties and that, at least, two gas components are required. For each gas component, we provide estimates of the corresponding kinetic temperature, total CS column density, and gas density.

  10. The Spitzer Extragalactic Representative Volume Survey (SERVS)

    NASA Astrophysics Data System (ADS)

    Mauduit, Jean-Christophe; Lacy, M.; Farrah, D.; Surace, J.; Jarvis, M.; Oliver, S.; Maraston, C.; SERVS Team

    2012-01-01

    We present details of the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 square degrees medium-deep survey at 3.6 and 4.5 μm with the post-cryogenic Spitzer Space Telescope to ≈ 2 μJy (AB=23.1) depth of five highly observed astronomical fields (Elais-N1, Elais-S1, Lockman Hole, Chandra-Deep Fied South and XMM). Data will be made available to the community in the Spring of 2012. SERVS is designed to enable the study of galaxy evolution as a function of environment from z ≈ 5 to the present day, and is the first extragalactic survey both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z ≥ 1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter and radio wavelengths to provide a coherent picture of the formation of massive galaxies.

  11. The Arp Ring: Galactic or extragalactic?

    NASA Technical Reports Server (NTRS)

    Abolins, J. A.; Rice, W. L.

    1987-01-01

    The Arp Ring is a faint, loop-like structure around the northern end of M81 which becomes apparent only on deep optical photographs of the galaxy. The nature of the Ring and its proximity to M81 are uncertain. Is it simply foreground structure, part of this galaxy, or is it within the M81 system? Infrared Astronomy Satellite (IRAS) maps of the region show a far-infrared counterpart of the Ring. The infrared data are compared with previous optical and radio observations to try to ascertain its physical nature. The poor correlation found between the common infrared/optical structure and the distribution of extragalactic neutral hydrogen, and the fact that its infrared properties are indistinguishable from those of nearby galactic cirrus, imply that the Arp Ring is simply a ring structure in the galactic cirrus.

  12. Modeling the Extragalactic Epoch of Reionization Foreground

    NASA Astrophysics Data System (ADS)

    Carroll, Patricia A.

    The Epoch of Reionization represents a largely unexplored yet fundamental chapter of the early universe. During this period, spanning several hundred million years, the first stars and galaxies formed and the Hydrogen-dominated intergalactic medium transitioned from a predominantly neutral to ionized state. Modern efforts to study exactly when and how reionization occurred are largely focused on the distribution of neutral Hydrogen gas and its evolution in response to the increasing abundance of luminous objects and ionizing flux. The Murchison Widefield Array is a low frequency radio interferometer designed as a first generation EoR experiment. The predominant systematic difficulty in making a detection of the primordial HI signal is the overwhelmingly bright emission from the intervening foreground galaxies and quasars. This thesis presents novel survey methods used to create a highly precise and reliable catalog of discrete extragalactic sources for the purposes of both calibration and foreground removal.

  13. The IRAS view of the extragalactic sky

    NASA Technical Reports Server (NTRS)

    Soifer, B. T.; Neugebauer, G.; Houck, J. R.

    1987-01-01

    The IR-observable characteristics of the extragalactic sky are reviewed, summarizing the results of recent studies based on the IRAS survey, which covers over 96 percent of the sky to about 500 mJy at 12, 25, and 60 microns and to about 1.5 Jy at 100 microns. The numerical and morphological data are described; possible mechanisms for the IR emission are discussed; and the object classes are considered separately. Consideration is given to spiral and disk galaxies, barred and ring galaxies, irregular and dwarf galaxies, blue compact galaxies, elliptical and S0 galaxies, AGN observations (BL Lacs and OVV quasars, Seyfert galaxies, and quasars), highly luminous IR galaxies, and the cosmological implications of the IRAS findings. Diagrams, graphs, and tables are provided.

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

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Angelakis, E.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Balbi, A.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Benabed, K.; Benoît, A.; Bernard, J.-P.; Bersanelli, M.; Bhatia, R.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Cabella, P.; Cappellini, B.; Cardoso, J.-F.; Catalano, A.; Cayón, L.; Challinor, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, L.-Y.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Couchot, F.; Coulais, A.; Crill, B. P.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Gasperis, G.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Donzelli, S.; Doré, O.; Dörl, U.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Fuhrmann, L.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Harrison, D.; Henrot-Versillé, S.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Hoyland, R. J.; Huffenberger, K. M.; Huynh, M.; Jaffe, A. H.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knox, L.; Krichbaum, T. P.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lavonen, N.; Lawrence, C. R.; Leach, S.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Mann, R.; Maris, M.; Marleau, F.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Mingaliev, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, A.; Naselsky, P.; Natoli, P.; Nestoras, I.; Netterfield, C. B.; Nieppola, E.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Pajot, F.; Paladini, R.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Plaszczynski, S.; Platania, P.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Poutanen, T.; Prézeau, G.; Procopio, P.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Renault, C.; Ricciardi, S.; Riller, T.; Riquelme, D.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sajina, A.; Sandri, M.; Savolainen, P.; Scott, D.; Seiffert, M. D.; Sievers, A.; Smoot, G. F.; Sotnikova, Y.; Starck, J.-L.; Stivoli, F.; Stolyarov, V.; Sudiwala, R.; Sygnet, J.-F.; Tammi, J.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tornikoski, M.; Torre, J.-P.; Tristram, M.; Tuovinen, J.; Türler, M.; Turunen, M.; Umana, G.; Ungerechts, H.; Valenziano, L.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; Wilkinson, A.; Yvon, D.; Zacchei, A.; Zensus, J. A.; Zonca, A.

    2011-12-01

    Planck's all-sky surveys at 30-857 GHz provide an unprecedented opportunity to follow the radio spectra of a large sample of extragalactic sources to frequencies 2-20 times higher than allowed by past, large-area, ground-based surveys. We combine the results of the Planck Early Release Compact Source Catalog (ERCSC) with quasi-simultaneous ground-based observations as well as archival data at frequencies below or overlapping Planck frequency bands, to validate the astrometry and photometry of the ERCSC radio sources and study the spectral features shown in this new frequency window opened by Planck. The ERCSC source positions and flux density scales are found to be consistent with the ground-based observations. We present and discuss the spectral energy distributions of a sample of "extreme" radio sources, to illustrate the richness of the ERCSC for the study of extragalactic radio sources. Variability is found to play a role in the unusual spectral features of some of these sources. Corresponding author: B. Partridge, e-mail: bpartrid@haverford.edu

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

    SciTech Connect

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

    2013-07-20

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

  16. Interpretation of extragalactic jets

    SciTech Connect

    Norman, M.L.

    1985-01-01

    The nature of extragalatic radio jets is modeled. The basic hypothesis of these models is that extragalatic jets are outflows of matter which can be described within the framework of fluid dynamics and that the outflows are essentially continuous. The discussion is limited to the interpretation of large-scale (i.e., kiloparsec-scale) jets. The central problem is to infer the physical parameters of the jets from observed distributions of total and polarized intensity and angle of polarization as a function of frequency. 60 refs., 6 figs.

  17. The extragalactic gamma-ray sky in the Fermi era

    NASA Astrophysics Data System (ADS)

    Massaro, Francesco; Thompson, David J.; Ferrara, Elizabeth C.

    2015-12-01

    The Universe is largely transparent to γ -rays in the GeV energy range, making these high-energy photons valuable for exploring energetic processes in the cosmos. After 7 years of operation, the Fermi Gamma-ray Space Telescope has produced a wealth of information about the high-energy sky. This review focuses on extragalactic γ -ray sources: what has been learned about the sources themselves and about how they can be used as cosmological probes. Active galactic nuclei (blazars, radio galaxies, Seyfert galaxies) and star-forming galaxies populate the extragalactic high-energy sky. Fermi observations have demonstrated that these powerful non-thermal sources display substantial diversity in energy spectra and temporal behavior. Coupled with contemporaneous multifrequency observations, the Fermi results are enabling detailed, time-dependent modeling of the energetic particle acceleration and interaction processes that produce the γ -rays, as well as providing indirect measurements of the extragalactic background light and intergalactic magnetic fields. Population studies of the γ -ray source classes compared to the extragalactic γ -ray background place constraints on some models of dark matter. Ongoing searches for the nature of the large number of γ -ray sources without obvious counterparts at other wavelengths remain an important challenge.

  18. VizieR Online Data Catalog: Compact steep spectrum new sample (Kunert-Bajraszewska+, 2010)

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    Using the final release of FIRST, combined with the Green Bank 6-cm (GB6) survey at 4.85GHz, we looked for unresolved, isolated sources, that is, more compact than the FIRST beam (5.4-arcsec), and surrounded by an empty field (we adopted 1-arcmin as the radius of that field). We required that the redshifts of the objects identified with radio sources were known, and we extracted these from the National Aeronautics and Space Administration (NASA)/Infrared Processing and Analysis Center (IPAC) Extragalactic Data base (NED) and the Sloan Digital Sky Survey (SDSS). (3 data files).

  19. Magnetic Bubble Expansion Experimental Investigation Using a Compact Coaxial Magnetized Plasma Gun

    NASA Astrophysics Data System (ADS)

    Zhang, Yue; Lynn, Alan; Hsu, Scott; Li, Hui; Liu, Wei; Gilmore, Mark; Watts, Christopher

    2009-11-01

    The poster will first discuss the construction and improved design of a compact coaxial magnetized plasma gun. The plasma gun is used for experimental studies of magnetic bubble expansion into a lower pressure background plasma, which as a model for extragalactic radio lobes and solar coronal mass ejections. In this experiment, the plasma bubble's density, electron temperature, and propagation speed are measured by using a multiple-tipped langmuir probe. Also a three axis B-dot probe array is used to measure the magnetic field in three dimensions during the expansion process. In this poster experiment setup and data will be provided. Finally the comparison with the simulation result will be made.

  20. EXTRAGALACTIC VERY HIGH ENERGY GAMMA-RAY BACKGROUND

    SciTech Connect

    Neronov, A.; Semikoz, D. V.

    2012-09-20

    We study the origin of the extragalactic diffuse gamma-ray background using the data from the Fermi telescope. To estimate the background level, we count photons at high Galactic latitudes |b| > 60 Degree-Sign . Subtracting photons associated with known sources and the residual cosmic-ray and Galactic diffuse backgrounds, we estimate the extragalactic gamma-ray background (EGB) flux. We find that the spectrum of EGB in the very high energy band above 30 GeV follows the stacked spectrum of BL Lac objects. Large Area Telescope data reveal the positive (1 + z) {sup k}, 1 < k < 4 cosmological evolution of the BL Lac source population consistent with that of their parent population, Fanaroff-Riley type I radio galaxies. We show that EGB at E > 30 GeV could be completely explained by emission from unresolved BL Lac objects if k {approx_equal} 3.

  1. Extragalactic background light measurements and applications

    PubMed Central

    Cooray, Asantha

    2016-01-01

    This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB. PMID:27069645

  2. Extragalactic background light measurements and applications.

    PubMed

    Cooray, Asantha

    2016-03-01

    This review covers the measurements related to the extragalactic background light intensity from γ-rays to radio in the electromagnetic spectrum over 20 decades in wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centred at 1 μm, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar System. The best measurements of COB come from an indirect technique involving γ-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 μm established an energetically important background with an intensity comparable to the optical background. This discovery paved the way for large aperture far-infrared and sub-millimetre observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV (EUV) background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 and 5 μm using a small aperture telescope observing either from the outer Solar System, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB. PMID:27069645

  3. A-3 scientific results - extragalactic

    NASA Technical Reports Server (NTRS)

    Schwartz, D. A.

    1979-01-01

    The results of the HEAO A-3 experiment are summarized. Specific contributions of the experiment to extragalactic astronomy are emphasized. The discovery of relatively condensed X-ray emission in the cores of those clusters of galaxies which are dominated by a giant elliptical or cD galaxy, the discovery of extended X-ray emitting plasma in groups of galaxies, and the demonstration that BL Lac objects are a class of X-ray sources are among the topics discussed.

  4. Metsaehovi Radio Observatory Annual Report 1998

    NASA Astrophysics Data System (ADS)

    Urpo, S.; Mujunen, A.

    1999-01-01

    Contents include the following: Introduction; Research Activities; Radio Astronomical Instrumentation; Extragalactic Radio Sources; Observations with Other Facilities; VLBI Research; Solar Research; HRDL for Alpha Magnetic Spectrometer (AMS); Radio Spectroscopy; Publications; Visits to Foreign Institutes; Visiting Scientists; Teaching; Other Activities; Personnel in 1998; and List of Figures.

  5. Application of disturbance observer-based control in low-level radio-frequency system in a compact energy recovery linac at KEK

    NASA Astrophysics Data System (ADS)

    Qiu, Feng; Michizono, Shinichiro; Miura, Takako; Matsumoto, Toshihiro; Omet, Mathieu; Sigit, Basuki Wibowo

    2015-09-01

    A disturbance observer (DOB)-based control for a digital low-level radio-frequency (LLRF) system in a compact energy recovery linac (cERL) at KEK has been developed. The motivation for this control approach is to compensate for or suppress the disturbance signal in the rf system such as beam loading, power supply ripples, and microphonics. Disturbance signals in specified frequency ranges were observed and reconstructed accurately in the field-programmable gate array and were then removed in the feedforward model in real time. The key component in this DOB controller is a disturbance observer, which includes the inverse mathematical model of the rf plant. In this paper, we have designed a DOB control-based approach in order to improve the LLRF system performance in disturbance rejection. We have confirmed this approach in the cERL beam commissioning.

  6. A Compact X-Ray Source in the Radio Pulsar-wind Nebula G141.2+5.0

    NASA Astrophysics Data System (ADS)

    Reynolds, Stephen P.; Borkowski, Kazimierz J.

    2016-01-01

    We report the results of a 50 ks Chandra observation of the recently discovered radio object G141.2+5.0, presumed to be a pulsar-wind nebula. We find a moderately bright unresolved X-ray source that we designate CXOU J033712.8 615302 coincident with the central peak radio emission. An absorbed power-law fit to the 241 counts describes the data well, with absorbing column {N}H=6.7(4.0,9.7)× {10}21 cm-2 and photon index {{Γ }}=1.8(1.4,2.2). For a distance of 4 kpc, the unabsorbed luminosity between 0.5 and 8 keV is {1.7}-0.3+0.4× {10}32 erg s-1 (90% confidence intervals). Both LX and Γ are quite typical of pulsars in PWNe. No extended emission is seen; we estimate a conservative 3σ upper limit to the surface brightness of any X-ray PWN near the point source to be 3× {10}-17 erg cm-2 s-1 arcsec-2 between 0.5 and 8 keV, assuming the same spectrum as the point source; for a nebula of diameter 13\\prime\\prime , the flux limit is 6% of the flux of the point source. The steep radio spectrum of the PWN (α ˜ -0.7), if continued to the X-ray without a break, predicts {L}{{X}} {{(nebula)}}˜ 1× {10}33 erg s-1, so additional spectral steepening between radio and X-rays is required, as is true of all known PWNe. The high Galactic latitude gives a z-distance of 350 pc above the Galactic plane, quite unusual for a Population I object.

  7. Modeling extragalactic bowshocks. I. The model.

    NASA Astrophysics Data System (ADS)

    Ferruit, P.; Binette, L.; Sutherland, R. S.; Pecontal, E.

    1997-06-01

    To probe the effects of the nuclear activity on the host galaxy, it is essential to disentangle the relative contribution of shock excitation from that of photoionization. One milestone towards this goal is the ability to model the bowshock structures created by the interaction of radio ejecta with their surrounding medium. We have built a bowshock model based on TDA's one (Taylor, Dyson & Axon, 1992MNRAS.255..351T) which was itself derived from an earlier work on Herbig-Haro objects. Since TDA's original model supplied the astronomers with only [OIII]λ5007 fluxes and profiles for various models of bowshocks, we undertook to include magnetic fields and to incorporate all of the atomic data tables of the code Mappings Ic for the computation of ionization states, cooling rates and line emissivities of the gas. This new model allows us to map line ratios and profiles of extragalactic bowshocks for all major lines of astrophysical interest. In this first paper, we present our model, analyse the gas behavior along the bowshock and give some examples of model results.

  8. IUE observations of extragalactic objects

    NASA Technical Reports Server (NTRS)

    Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti, P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.; Gondhalekar, P.

    1978-01-01

    During the commissioning phase of IUE several extragalactic objects were observed spectrally at low dispersion in the UV range lambda lambda 1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained.

  9. Variable Radio Sources in the Galactic Plane

    NASA Astrophysics Data System (ADS)

    Becker, Robert H.; Helfand, David J.; White, Richard L.; Proctor, Deanne D.

    2010-07-01

    Using three epochs of Very Large Array observations of the Galactic plane in the first quadrant taken ~15 years apart, we have conducted a search for a population of variable Galactic radio emitters in the flux density range 1-100 mJy at 6 cm. We find 39 variable sources in a total survey area of 23.2 deg2. Correcting for various selection effects and for the extragalactic variable population of active galactic nuclei, we conclude there are ~1.6 deg-2 Galactic sources which vary by more than 50% on a time scale of years (or shorter). We show that these sources are much more highly variable than extragalactic objects; more than 50% show variability by a factor >2 compared to <10% for extragalactic objects in the same flux density range. We also show that the fraction of variable sources increases toward the Galactic center (another indication that this is a Galactic population), and that the spectral indices of many of these sources are flat or inverted. A small number of the variables are coincident with mid-IR sources and two are coincident with X-ray emitters, but most have no known counterparts at other wavelengths. Intriguingly, one lies at the center of a supernova remnant, while another appears to be a very compact planetary nebula; several are likely to represent activity associated with star formation regions. We discuss the possible source classes which could contribute to the variable cohort and follow-up observations which could clarify the nature of these sources.

  10. 21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies

    SciTech Connect

    Loeb, Abraham

    2008-05-15

    The clumpy maser discs observed in some galactic nuclei mark the outskirts of the accretion disc that fuels the central black hole and provide a potential site of nuclear star formation. Unfortunately, most of the gas in maser discs is currently not being probed; large maser gains favor paths that are characterized by a small velocity gradient and require rare edge-on orientations of the disc. Here we propose a method for mapping the atomic hydrogen distribution in nuclear discs through its 21 cm absorption against the radio continuum glow around the central black hole. In NGC 4258, the 21 cm optical depth may approach unity for high angular resolution (VLBI) imaging of coherent clumps which are dominated by thermal broadening and have the column density inferred from x-ray absorption data, {approx}10{sup 23} cm{sup -2}. Spreading the 21 cm absorption over the full rotation velocity width of the material in front of the narrow radio jets gives a mean optical depth of {approx}0.1. Spectroscopic searches for the 21 cm absorption feature in other galaxies can be used to identify the large population of inclined gaseous discs which are not masing in our direction. Follow-up imaging of 21 cm silhouettes of accelerating clumps within these discs can in turn be used to measure cosmological distances.

  11. A panchromatic study of extragalactic HII regions

    NASA Astrophysics Data System (ADS)

    Peeters, Els; Allamandola, Louis; Bernard-Salas, Jeronimo; Tielens, Alexander

    2006-05-01

    Star formation rates (SFR) are considered the key to understanding galaxy formation and evolution. All wavelength regions have been exploited to determine the SFR by studying massive star forming regions at all redshifts. Indeed, traditionally, SFR in galaxies are determined based upon H alpha, FIR and the UV. In recent years, MIR tracers of star formation activity of galaxies have been explored but their quantitative use is still under debate. Here, we propose to obtain Spitzer-IRS SL-LL observations of a sample of well-characterized HII regions in two galaxies, M33 and M83. These HII regions span a wide range in galactocentric radii and hence metallicity. These metallicities have been determined through an earlier, unrelated investigation (PID 3412 & 20057; PI Rubin). The proposed observations are complementary to existing auxiliary data and are in fact the missing link for a panchromatic view of individual extragalactic HII regions. This proposal will provide, for the first time, a quantitative estimate of the effects on the MIR characteristics of extagalactic HII regions of parameters such as the metallicity, the hardness of the stellar radiation field (NeIII/NeII and/or SIV/SIII ratios), density (NeIII and/or SIII line ratios), stellar luminosity (radio, H alpha) can be systematically investigated. Hence, the proposed observations form the basis for a systematic study of PAH and dust properties, their dependency on the physical conditions of the environment and their usefulness as a quantitative tracer for star formation. As a result, this study will influence the interpretation of star forming regions on small and large scales and distances out to the era of vigorous star formation activity.

  12. Supergiant pulses from extragalactic neutron stars

    NASA Astrophysics Data System (ADS)

    Cordes, J. M.; Wasserman, Ira

    2016-03-01

    We consider radio bursts that originate from extragalactic neutron stars (NSs) by addressing three questions about source distances. What are the physical limitations on coherent radiation at GHz frequencies? Do they permit detection at cosmological distances? How many bursts per NS are needed to produce the inferred burst rate ˜103-104sky-1 d-1? The burst rate is comparable to the NS formation rate in a Hubble volume, requiring only one per NS if they are bright enough. Radiation physics suggests a closer population, requiring more bursts per NS and increasing the chances for repeats. Bursts comprise sub-ns, coherent shot pulses superposed incoherently to produce ms-duration ˜1 Jy amplitudes; each shot pulse can be much weaker than 1 Jy, placing less restrictive requirements on the emission process. None the less, single shot pulses are similar to the extreme, unresolved (<0.4 ns) MJy shot pulse seen from the Crab pulsar, consistent with coherent curvature radiation emitted near the light cylinder by an almost neutral clump with net charge ˜± 1021e and total energy ≳ 1023 erg. Bursts from Gpc distances require incoherent superposition of {˜ } 10^{12}d_Gpc^2 shot pulses or a total energy ≳ 10^{35} d_Gpc^2 erg. The energy reservoir near the light cylinder limits the detection distance to ≲ few × 100 Mpc for a fluence ˜1 Jy ms unless conditions are more extreme than for the Crab pulsar, such as in magnetars. We discuss contributions to dispersion measures from galaxy clusters and we propose tests for the overall picture presented.

  13. The Evolving Radio Jet in BL Lacerta

    NASA Astrophysics Data System (ADS)

    Aller, H. D.; Hughes, P. A.; Aller, M. F.

    1994-05-01

    During the past 15 years, there have been at least ten outbursts at centimeter wavelengths in this extragalactic object. We describe here the flux density and linear polarization variations observed at 4.8, 8.0 and 14.5 GHz with the Michigan 26-meter telescope during the series of outbursts since 1987. The recent bursts are somewhat different from the highly polarized bursts in the early 1980s, which provided a successful quantitative test of a source model based on propagating transverse shocks in a relativistic jet. The most notable change is that the polarization position angle during polarized outbursts has increased by approximately 10 degrees. This is approximately the same shift as found in a comparison of VLBI maps taken during the same time periods by Mutel, Denn and Dryer (1994, NRAO Workshop on Compact Extragalactic Radio Sources, ed. Zensus and Kellermann, p. 191), and supports their conclusion that the orientation of the radio emitting jet in BL Lac has changed over time. Our preliminary analysis further suggests that a simple scaling of the physical parameters which gave quantitatively good fits to both the 1982 and 1983 bursts will not accurately describe the recent, relatively isolated, burst in 1991. We also note that while some bursts (e.g. in 1982, 1983 and 1991) exhibit degrees of linear polarization in excess of ten percent, other bursts (e.g. in 1980 and 1990) exhibit a very low degree of linear polarization. A common characteristic of the low polarization events is that they all exhibit high internal synchrotron self absorption (as indicated by the flux density spectra of the outbursts). This research has been supported in part by NSF grant AST-9120224.

  14. Gravitational-wave Constraints on the Progenitors of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Callister, Thomas; Kanner, Jonah; Weinstein, Alan

    2016-07-01

    The nature of fast radio bursts (FRBs) remains enigmatic. Highly energetic radio pulses of millisecond duration, FRBs are observed with dispersion measures consistent with an extragalactic source. A variety of models have been proposed to explain their origin. One popular class of theorized FRB progenitor is the coalescence of compact binaries composed of neutron stars and/or black holes. Such coalescence events are strong gravitational-wave emitters. We demonstrate that measurements made by the LIGO and Virgo gravitational-wave observatories can be leveraged to severely constrain the validity of FRB binary coalescence models. Existing measurements constrain the binary black hole rate to approximately 5% of the FRB rate, and results from Advanced LIGO’s O1 and O2 observing runs may place similarly strong constraints on the fraction of FRBs due to binary neutron star and neutron star–black hole progenitors.

  15. A Sample of Clusters of Extragalactic Ultracompact H II Regions

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsey E.; Kobulnicky, Henry A.; Massey, Philip; Conti, Peter S.

    2001-10-01

    We report on the detection of optically thick free-free radio sources in the galaxies M33, NGC 253, and NGC 6946 using data in the literature. We interpret these sources as being young embedded star birth regions that are likely to be clusters of ultracompact H II regions. All 35 of the sources presented in this article have positive radio spectral indices (α>0 for Sν~να), suggesting an optically thick thermal bremsstrahlung origin from the H II region surrounding the hot stars. The estimated emission measures for these sources are EM6 cm>~108 cm-6 pc, and energy requirements indicate that the sources in our sample have a range of a few to ~560 O7 V star equivalents powering their H II regions. Assuming a Salpeter initial mass function with lower and upper mass cutoffs of 1 and 100 Msolar, respectively, this range in NLyc corresponds to integrated stellar masses of 0.1-60×103 Msolar. For roughly half of the sources in our sample there is no obvious optical counterpart, which gives further support for their deeply embedded nature; for most of the remaining sources, the correspondence to an optical source is insecure owing to relative astrometric uncertainty. Their luminosities and radio spectral energy distributions are consistent with H II regions modeled as spheres of plasma with electron densities from ne~1.5×103 to ~1.5×104 cm-3 and radii of ~1-7 pc. Because of the high densities required to fit the data, we suggest that the less luminous of these sources are extragalactic ultracompact H II region complexes, those of intermediate luminosity are similar to W49 in the Galaxy, and the brightest will be counterparts to 30 Doradus when they emerge from their birth material. These objects constitute the lower mass range of extragalactic ``ultradense H II regions,'' which we argue are the youngest stages of massive star cluster formation yet observed. The sample presented in this paper is beginning to fill in the continuum of objects between small associations

  16. Statistical analysis of power-size-redshift distributions of extragalactic jets

    NASA Technical Reports Server (NTRS)

    Rosen, Alexander; Wiita, Paul J.

    1991-01-01

    This paper investigates whether a hot, sparse, yet cosmologically significant intergalactic medium is consistent with data collected from extragalactic radio sources. This is done by use of Monte Carlo simulations which employ previously run pseudohydrodynamical simulations to cover an observational parameter space. These observational parameters include the scale height, central density, and temperature of a (isothermal) galactic halo, and the power of the central engine which drives the jet. The Monte Carlo simulations generate distribution of sizes in bins of (received) power and redshift, which have been compared with observational data using Kolmogorov-Smirnov tests. Results of this analysis are consistent with the existence of an IGM with temperature and density mentioned above. In addition, this analysis suggests that the active lifetime of powerful extragalactic radio sources decreases with increasing power.

  17. On the variability of extragalactic sources in the decimeter range and their correlation with galactic structures

    NASA Technical Reports Server (NTRS)

    Shapirovskaya, N. Y.

    1979-01-01

    It is shown that all of the extragalactic radio sources presently known are variable in the decimeter range (lambda or = 30 cm) and are projected on the large continuum radio structure of the galaxy: loops, spurs, ridges. Probability that coordinates could coincide is or = 10 to the minus 7 power. The variations in the intensity are explained by scintillations (regime of focusing radiation) on the large-scale irregularities of electron density in the medium of loops, spurs and ridges with the dimension a magnitude of approximately 10 to the 13th power cm. A correlation of the characteristics of radiation of the sources with their position relative to the galactic loop is considered. Based on the known experimental data, it is shown that the angle of scattering of extragalactic radiation and the dispersion measures of pulsars projecting on the loops is considerably larger than those of the sources lying outside the loops.

  18. LOCATING THE ''MISSING'' BARYONS WITH EXTRAGALACTIC DISPERSION MEASURE ESTIMATES

    SciTech Connect

    McQuinn, Matthew

    2014-01-10

    Recently, Thornton and coworkers confirmed a class of millisecond radio bursts likely of extragalactic origin that is well-suited for estimating dispersion measures (DMs). We calculate the probability distribution of DM(z) in different models for how the cosmic baryons are distributed (both analytically and with cosmological simulations). We show that the distribution of DM is quite sensitive to whether the ''missing'' baryons lie around the virial radius of 10{sup 11}-10{sup 13} M{sub ☉} halos or further out, which is not easily constrained with other observational techniques. The intrinsic contribution to DM from each source could complicate studies of the extragalactic contribution. This difficulty is avoided by stacking based on the impact parameter to foreground galaxies. We show that a stacking analysis using a sample of ∼100 DM measurements from arcminute-localized, z ≳ 0.5 sources would place interesting constraints at 0.2-2 halo virial radii on the baryonic mass profile surrounding different galaxy types. Conveniently for intergalactic studies, sightlines that intersect intervening galactic disks should be easily identified owing to scattering. A detectable level of scattering may also result from turbulence in the circumgalactic medium.

  19. VLA observations of a complete sample of extragalactic X-ray sources. II

    NASA Technical Reports Server (NTRS)

    Schild, R.; Zamorani, G.; Gioia, I. M.; Feigelson, E. D.; Maccacaro, T.

    1983-01-01

    A complete sample of 35 X-ray selected sources found with the Einstein Observatory has been observed with the Very Large Array at 6 cm to investigate the relationship between radio and X-ray emission in extragalactic objects. Detections include three active galactic nuclei (AGNs), two clusters or groups of galaxies, two individual galaxies, and two BL Lac objects. The frequency of radio emission in X-ray selected AGNs is compared with that of optically selected quasars using the integral radio-optical luminosity function. The result suggests that the probability for X-ray selected quasars to be radio sources is higher than for those optically selected. No obvious correlation is found in the sample between the richness of X-ray luminosity of the cluster and the presence of a galaxy with radio luminosity at 5 GHz larger than 10 to the 30th ergs/s/Hz.

  20. Automated Searches for Extragalactic Novae

    NASA Astrophysics Data System (ADS)

    Darnley, M. J.

    2005-06-01

    Classical novae (CNe) are interacting binary systems in which the white dwarf undergoes unpredictable explosive outbursts. The energy of a nova outburst is only surpassed by that of gamma-ray bursts, supernovae and a small number of luminous blue variables. However, the outbursts of CNe are far more common than any of these other stars. Due to their brightness and occurrence in both Population I and Population II systems, novae are potentially important as extragalactic distance indicators and tools in the exploration of binary star evolution in galaxies. The POINT-AGAPE survey is an optical search for gravitational micro-lensing events towards the Andromeda galaxy (M31). As well as micro-lensing, the survey is sensitive to many different classes of variable stars and transients, including CNe. In this work we describe the automated detection and selection pipeline used to identify M31 CNe and we present the resulting catalogue of 20 strong CN candidates observed over three seasons. The CNe we discover are observed both in the M31 bulge region as well as over a wide area of the M31 disc. Nine of the CNe are caught during the final rise phase (which is often missed in Galactic novae) and all are well sampled in at least two colours. The excellent light-curve coverage has allowed us to detect and classify CNe over a wide range of speed classes, from very fast to very slow. Among the light curves is, for example, a moderately fast CN exhibiting entry into a deep transition minimum, followed by its final decline. We have also observed in detail a very slow CN which faded by only 0.01 mag day^{-1} over a 150 day period. The CN catalogue constitutes a uniquely well-sampled and objectively-selected data set with which to study the statistical properties of CNe in M31. As a by-product, we have detected other interesting variable objects, including one of the longest period and most luminous Mira variables. An analysis of the MMRD relationship in M31 was performed using the

  1. A SURVEY OF EXTRAGALACTIC FARADAY ROTATION AT HIGH GALACTIC LATITUDE: THE VERTICAL MAGNETIC FIELD OF THE MILKY WAY TOWARD THE GALACTIC POLES

    SciTech Connect

    Mao, S. A.; Gaensler, B. M.; Madsen, G. J.; Haverkorn, M.; Zweibel, E. G.; McClure-Griffiths, N. M.; Shukurov, A.; Kronberg, P. P.

    2010-05-10

    We present a study of the vertical magnetic field of the Milky Way toward the Galactic poles, determined from observations of Faraday rotation toward more than 1000 polarized extragalactic radio sources at Galactic latitudes |b| {>=} 77{sup 0}, using the Westerbork Radio Synthesis Telescope and the Australia Telescope Compact Array. We find median rotation measures (RMs) of 0.0 {+-} 0.5 rad m{sup -2} and +6.3 {+-} 0.7 rad m{sup -2} toward the north and south Galactic poles, respectively, demonstrating that there is no coherent vertical magnetic field in the Milky Way at the Sun's position. If this is a global property of the Milky Way's magnetism, then the lack of symmetry across the disk rules out pure dipole or quadrupole geometries for the Galactic magnetic field. The angular fluctuations in RM seen in our data show no preferred scale within the range {approx}0.{sup 0}1 to {approx}25{sup 0}. The observed standard deviation in RM of {approx}9 rad m{sup -2} then implies an upper limit of {approx}1 {mu}G on the strength of the random magnetic field in the warm ionized medium at high Galactic latitudes.

  2. A NEW RESULT ON THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

    SciTech Connect

    Zhou Ming; Wang Jiancheng

    2013-06-01

    In this paper, we repeatedly use the method of image stacking to study the origin of the extragalactic gamma-ray background (EGB) at GeV bands, and find that the Faint Images of the Radio Sky at Twenty centimeters (FIRST) sources undetected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope can contribute about (56 {+-} 6)% of the EGB. Because FIRST is a flux-limited sample of radio sources with incompleteness at the faint limit, we consider that point sources, including blazars, non-blazar active galactic nuclei, and starburst galaxies, could produce a much larger fraction of the EGB.

  3. Compact Low Frequency Radio Antenna

    DOEpatents

    Punnoose, Ratish J.

    2008-11-11

    An antenna is disclosed that comprises a pair of conductive, orthogonal arches and a pair of conductive annular sector plates, wherein adjacent legs of each arch are fastened to one of the annular sector plates and the opposite adjacent pair of legs is fastened to the remaining annular sector plate. The entire antenna structure is spaced apart from a conductive ground plane by a thin dielectric medium. The antenna is driven by a feed conduit passing through the conductive ground plane and dielectric medium and attached to one of the annular sector plates, wherein the two orthogonal arched act as a pair of crossed dipole elements. This arrangement of elements provides a radiation pattern that is largely omni-directional above the horizon.

  4. HET Spectroscopy of Extragalactic Novae

    NASA Astrophysics Data System (ADS)

    Shafter, Allen W.; Coelho, E. A.; Misselt, K. A.; Bode, M. F.; Darnley, M. J.

    2006-12-01

    We are currently involved in a multifaceted campaign to study extragalactic novae in the optical and IR using a variety of instruments: The Mount Laguna 1m, the Steward 2.3m, and the Liverpool 2m telescopes for optical imaging, the Hobbey-Eberly Telescope (HET) for optical spectroscopy, and the Spitzer Space Telescope for IR photometry and spectroscopy. Here, we report the initial results from our program of spectroscopic observations obtained with the LRS on the HET. Thus far, we have obtained spectra of three novae: Nova M31-2006#9 (ATEL 887), Nova M32-2006#1 (CBET 591), and Nova M33-2006#1 (CBET 655), which were taken on 24-Sep-2006 UT, 30-Sep-2006 UT, and 02-Oct-2006 UT, approximately 6, 65, and 4 days post discovery, for the three novae respectively. The spectra of Nova M31-2006#9 and Nova M33-2006#1 revealed prominent Balmer (FWHM 1600 km/s) and Fe II emission lines typical of the "Fe II" class in the classification system of Williams (1992 AJ, 104, 725). The spectrum of Nova M32-2006#1, which was obtained much longer after eruption, showed strong H-alpha (FWHM 1300 km/s), along with weaker H-beta, Fe II, and [N II] 5755, indicating that this nova is also a member of the Fe II class, and that it had entered the nebular phase at the time of our observations. In addition to these three novae, we also attempted to obtain a spectrum of Nova M31-2006#7 (CBET 615) on 23-Sep-2006 UT, approximately three weeks after discovery. However, by the time of our observations, the nova had faded to invisibility. An 1800s integration at the reported position reveled no trace of the nova. It is likely that this optical transient was an unusually fast nova, possibly of the "He/N" class. This work is being supported in part by NSF grant AST-0607682.

  5. Extragalactic astronomy: The universe beyond our galaxy

    NASA Technical Reports Server (NTRS)

    Jacobs, K. C.

    1976-01-01

    This single-topic brochure is for high school physical science teachers to use in introducing students to extragalactic astronomy. The material is presented in three parts: the fundamental content of extragalactic astronomy; modern discoveries delineated in greater detail; and a summary of the earlier discussions within the structure of the Big-Bang Theory of evolution. Each of the three sections is followed by student exercises (activities, laboratory projects, and questions-and-answers). The unit close with a glossary which explains unfamilar terms used in the text and a collection of teacher aids (literature references and audiovisual materials for utilization in further study).

  6. Antiparticles in the extragalactic cosmic radiation

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Wolfendale, A. W.

    1985-01-01

    It may be possible to account for a previously puzzling feature - a bump in the energy range 10 to the 14th power eV to 10 to the 15th power - of the cosmic ray spectrum by hypothesizing a primary extragalactic origin for the bulk of the observed cosmic ray antiprotons, although such an explanation is not unique. In this model, most of the cosmic rays above 10 to the 15th power eV are extragalactic. A method is described of testing this hypothesis experimentally.

  7. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  8. The balance between shocks and AGN photoionization in radio sources and its relation to the radio size

    NASA Astrophysics Data System (ADS)

    Moy, E.; Rocca-Volmerange, B.

    2002-01-01

    We have analyzed the ultraviolet and optical emission line ratios of a large sample of extragalactic radio sources (QSOs and radio galaxies), with the help of models combining AGN photoionization and shocks. The results strongly suggest that the two ionizing mechanisms frequently coexist. The model sequences obtained by varying the balance between shocks and AGN photoionization account for most emission line data in the 12 line ratio diagrams we have considered. In the frequently used diagrams involving [OIII]lambda 5007/Hβ , [OI]lambda 6300/Hα , [NII]lambda 6584/Hα and [SII]lambda lambda 6716, 6731 (Veilleux & Osterbrock 1987), the effect of varying the shock-photoionization balance mimics a variation of the ionization parameter (U) in traditional photoionization sequences. In most of the remaining diagrams, such as [OI]lambda 6300/[OIII]lambda 5007 vs. [OIII]lambda 4363/[OIII]lambda 5007, [OIII]lambda 5007/Hβ vs. [OIII]lambda 4363/[OIII]lambda 5007 and CIII]lambda 1909/[CII]lambda 2326 vs. CIVlambda 1549/[CII]lambda 2326, the data can only be accounted for if both photoionization and shocks contribute to the line fluxes. The coexistence of shocks and AGN photoionization also provides an explanation for the most extreme objects in the NVlambda 1240/HeIIlambda 1640 vs. NVlambda 1240/CIVlambda 1549 diagram without requiring largely super-solar metallicities. In addition, we show that there is a relationship between the [OII]lambda 3727/[OIII]lambda 5007 ratio (i.e., the ionization level of the gas) and the radio size in radio galaxies. This strongly supports the hypothesis that the most compact (le 2kpc) and the largest (ge 150 kpc) sources are dominated by photoionization, while intermediate-sized radio galaxies are dominated by shocks. We briefly discuss the possible origin of the relation between the shock-ionization balance and the radio size.

  9. Extragalactic Astronomy: The Universe Beyond Our Galaxy.

    ERIC Educational Resources Information Center

    Jacobs, Kenneth Charles

    This booklet is part of an American Astronomical Society curriculum project designed to provide teaching materials to teachers of secondary school chemistry, physics, and earth science. The material is presented in three parts: one section provides the fundamental content of extragalactic astronomy, another section discusses modern discoveries in…

  10. EXTRAGALACTIC DARK MATTER AND DIRECT DETECTION EXPERIMENTS

    SciTech Connect

    Baushev, A. N.

    2013-07-10

    Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute {approx}12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed ({approx}600 km s{sup -1}), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow ({approx}20 km s{sup -1}). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s{sup -1}), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors.

  11. The Extragalactic Nature of PP:31

    NASA Astrophysics Data System (ADS)

    Parsamian, E. S.; Guichard, J.; Mujica, R.

    1994-10-01

    A discussion about the extragalactic nature of PP 31 is presented. This object has been previously classified as a Galactic cometary nebula, but a spectroscopic study reveals that it has a redshift of z = 0.0169. A comparison of some line ratios with the Veilleux & Osterbrock diagrams indicates that this object is an HII region galaxy.

  12. Long term monitoring of extragalactic sources in the framework of the Gaia ESA mission

    NASA Astrophysics Data System (ADS)

    TARIS, François

    2015-08-01

    The Gaia astrometric mission of the European Space Agency has been launched the 19th December 2013. It will provide an astrometric catalogue of 500.000 extragalactic sources that could be the basis of a new optical reference frame after the Hipparcos satellite one. On the other hand, the current International Celestial Reference Frame (ICRF) is based on the observations of extragalactic sources at radio wavelength. The astrometric coordinates of sources in these two reference systems will have roughly the same uncertainty. It is then mandatory to observe a set of common targets at both optical and radio wavelength to link the ICRF with what could be called the GCRF (Gaia Celestial Reference Frame).This poster presents the set of optical telescopes used to observe the targets chosen for the link of the two reference systems.It also presents some results obtained with the Lomb-Scargle method and CLEAN algorithm applied to optical magnitude monitoring of extragalactic sources suitable for the GCRF-ICRF link. These two methods allow to show that some periodic (or quasi-periodic) phenomena could be present and could be at the origin of the observed light curves. This could have an important impact on the photocenter's position of a particular target which is relevant for the link of the reference systems.

  13. A Compact Beam Measurement Setup

    NASA Astrophysics Data System (ADS)

    Graf, Urs U.

    2016-08-01

    We present the design of a compact measurement device to determine the position of a beam in a radio optical setup. The unit is used to align the Terahertz optics of the GREAT instrument on the airborne astronomical observatory SOFIA.

  14. A Compact Beam Measurement Setup

    NASA Astrophysics Data System (ADS)

    Graf, Urs U.

    2016-03-01

    We present the design of a compact measurement device to determine the position of a beam in a radio optical setup. The unit is used to align the Terahertz optics of the GREAT instrument on the airborne astronomical observatory SOFIA.

  15. Detection of Extended Emission from Fornax A and Measurement of the Extragalactic Background Light

    NASA Astrophysics Data System (ADS)

    Magill, Jeffrey; McConville, William; Georganopoulos, Markos; Meyer, Eileen; Perkins, Jeremy; Stawarz, Lukasz; Fermi-LAT Collaboration

    2015-04-01

    Prior to the launch of Fermi in 2008, the radio galaxy Fornax A was identified as one of the few extragalactic objects that might be detected as spatially extended above 100 MeV. However, even though it was detected with high confidence in the first 2 years of the mission, it was not determined to be an extended source. Recently, the Fermi-LAT collaboration developed a new event-level analysis called Pass 8 which yields a larger acceptance, a better angular and energy resolution, as well as smaller systematic uncertainties. The improvements provided with Pass 8 combined with a longer exposure means that the spatial extension of Fornax A is significantly detected, making it only the second extragalactic gamma-ray source so far to show extent. Details of this measurement will be presented along with modeling of the emission above 100 MeV.

  16. Faint Radio Sources in the NOAO Boötes Field: VLBA Imaging and Optical Identifications

    NASA Astrophysics Data System (ADS)

    Wrobel, J. M.; Taylor, G. B.; Rector, T. A.; Myers, S. T.; Fassnacht, C. D.

    2005-09-01

    As a step toward investigating the parsec-scale properties of faint extragalactic radio sources, the Very Long Baseline Array (VLBA) was used at 5.0 GHz to obtain phase-referenced images of 76 sources in the NOAO Boötes field. These 76 sources were selected from the Faint Images of the Radio Sky at Twenty cm (FIRST) catalog to have peak flux densities above 10 mJy at 5" resolution and deconvolved major diameters of less than 3" at 1.4 GHz. Of these faint radio sources, 57 were identified with accretion-powered radio galaxies and quasars brighter than 25.5 mag in the optical I band. On Very Large Array (VLA) scales at 1.4 GHz, a measure of the compactness of the faint sources (the ratio of the peak flux density from FIRST to the integrated flux density from the NRAO VLA Sky Survey catalog) spans the full range of possibilities arising from source-resolution effects. Of the faint radio sources, 30, or 39+9-7%, were detected with the VLBA at 5.0 GHz with peak flux densities above 6 σ~2 mJy at 2 mas resolution. The VLBA detections occur through the full range of compactness ratios. The stronger VLBA detections can themselves serve as phase-reference calibrators, boding well for opening up much of the radio sky to VLBA imaging. For the adopted cosmology, the VLBA resolution corresponds to 17 pc or finer. Most VLBA detections are unresolved or slightly resolved, but one is diffuse and five show either double or core-jet structures; the properties of these latter six are discussed in detail. Three VLBA detections are unidentified and fainter than 25.5 mag in the optical I band; their properties are highlighted because they likely mark optically obscured active nuclei at high redshift.

  17. Radio Stars or Radio Nebulae? - The Uncertainties of 1953

    NASA Astrophysics Data System (ADS)

    Sullivan, W. T., III

    1997-12-01

    By the early 1950s radio astronomers in England and Australia had assembled a handful of catalogues giving flux densities (at 100 MHz) and positions for a total of about 200 radio sources. But only a half dozen of these sources had suggested optical identifications and there raged a debate as to whether the radio sources as a whole were galactic or extragalactic. Furthermore, what was the relationship between these discrete radio sources and the strong galactic background radiation? Could a consistent model be constructed in which the background was the integrated radiation from the weaker members of the detected population? This paper aims to convey the uncertainty of astronomers in 1953. The primary data emanated from the surveys of Ryle, Smith and Elsmore (1950), Bolton, Stanley and Slee (1950), Mills (1952), and Hanbury Brown and Hazard (1953). Quoted position uncertainties were typically 0.5 to 2 degrees; even more discouraging, in overlapping regions the surveys seldom agreed. Optical identifications were rare and of varying degrees of acceptance, and in any case were about evenly split between galaxies (e.g., M31, Cyg A, Vir A) and galactic objects (e.g., Tau A = the Crab nebula, Cas A). And why were so many bright galaxies and gaseous nebulae not detected in the radio? Were there two classes of source, as suggested by Bernard Mills? If the bulk of the sources were extragalactic, what was their source of prodigious radio luminosity and why was it so much larger than the Milky Way's? If the background consisted of radio stars with a Population II distribution, was there also an isotropic extragalactic background component, as modelled by Jan Oort and Gart Westerhout (1950)? What in fact was the radiation mechanism for the sources and the background - free-free (but of what optical thickness?), synchrotron (but did the cosmic ray electrons exist?), or something else?

  18. The Astronomical Low Frequency Array: A Proposed Explorer Mission for Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Jones, D.; Allen, R.; Basart, J.; Bastian, T.; Bougeret, J. L.; Dennison, B.; Desch, M.; Dwarakanath, K.; Erickson, W.; Finley, D.; Kaiser, M.; Kassim, N.; Kuiper, T.; MacDowall, R.; Mahoney, M.; Perley, R.; Preston, R.; Reiner, M.; Rodriguez, P.; Stone, R.; Unwin, S.; Weiler, K.; Woan, G.; Woo, R.

    1999-01-01

    A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.

  19. Precision Geodesy via Radio Interferometry.

    PubMed

    Hinteregger, H F; Shapiro, I I; Robertson, D S; Knight, C A; Ergas, R A; Whitney, A R; Rogers, A E; Moran, J M; Clark, T A; Burke, B F

    1972-10-27

    Very-long-baseline interferometry experiments, involving observations of extragalactic radio sources, were performed in 1969 to determine the vector separations between antenna sites in Massachusetts and West Virginia. The 845.130-kilometer baseline was estimated from two separate experiments. The results agreed with each other to within 2 meters in all three components and with a special geodetic survey to within 2 meters in length; the differences in baseline direction as determined by the survey and by interferometry corresponded to discrepancies of about 5 meters. The experiments also yielded positions for nine extragalactic radio sources, most to within 1 arc second, and allowed the hydrogen maser clocks at the two sites to be synchronized a posteriori with an uncertainty of only a few nanoseconds. PMID:17815361

  20. HET Spectra of Three Recent Extragalactic Novae

    NASA Astrophysics Data System (ADS)

    Shafter, A. W.; Coelho, E. A.; Misselt, K. A.; Bode, M. F.; Darnley, M. J.; Quimby, R.

    2006-10-01

    We report optical spectroscopic observations (4280Å - 7280Å) obtained with the HET of three extragalactic novae: Nova M31 2006 No. 9 (ATEL #887), Nova M32 2006 No. 1 (CBET #591), and Nova M33 2006 No. 1 (CBET #655). The spectra were obtained on 24 Sep 2006 UT, 30 Sep 2006 UT, and 02 Oct 2006 UT, corresponding to approximately 6, 65, and 4 days post discovery, for the three novae respectively.

  1. Infrared Astronomy. [observations of extragalactic sources

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Matthews, K.

    1981-01-01

    Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported.

  2. Faint Radio Sources in the NOAO Bootes Field. VLBA Imaging And Optical Identifications

    SciTech Connect

    Wrobel, J.M.; Taylor, Greg B.; Rector, T.A.; Myers, S.T.; Fassnacht, C.D.; /UC, Davis

    2005-06-13

    As a step toward investigating the parsec-scale properties of faint extragalactic radio sources, the Very Long Baseline Array (VLBA) was used at 5.0 GHz to obtain phase-referenced images of 76 sources in the NOAO Booetes field. These 76 sources were selected from the FIRST catalog to have peak flux densities above 10 mJy at 5'' resolution and deconvolved major diameters of less than 3'' at 1.4 GHz. Fifty-five of these faint radio sources were identified with accretion-powered radio galaxies and quasars brighter than 25.5 mag in the optical I band. On VLA scales at 1.4 GHz, a measure of the compactness of the faint sources (the ratio of the peak flux density from FIRST to the integrated flux density from the NVSS catalog) spans the full range of possibilities arising from source-resolution effects. Thirty of the faint radio sources, or 39{sub -7}{sup +9}%, were detected with the VLBA at 5.0 GHz with peak flux densities above 6 {sigma} {approx} 2 mJy at 2 mas resolution. The VLBA detections occur through the full range of compactness ratios. The stronger VLBA detections can themselves serve as phase-reference calibrators, boding well for opening up much of the radio sky to VLBA imaging. For the adopted cosmology, the VLBA resolution corresponds to 17 pc or finer. Most VLBA detections are unresolved or slightly resolved but one is diffuse and five show either double or core-jet structures; the properties of these latter six are discussed in detail. Eight VLBA detections are unidentified and fainter than 25.5 mag in the optical I band; their properties are highlighted because they likely mark optically-obscured active nuclei at high redshift.

  3. The Bonn contribution to the extragalactic link of the HIPPARCOS proper motion system.

    NASA Astrophysics Data System (ADS)

    Tucholke, H.-J.; Brosche, P.; Odenkirchen, M.

    1997-05-01

    In order to calibrate the proper motions of the Hipparcos astrometry satellite, our group has measured accurate absolute proper motions of Hipparcos stars in small fields around optically bright extragalactic radio sources or bright galaxies with star-like features. In addition, we also use fields where relative proper motions are calibrated by measurements of large numbers of stars and galaxies on wide-field plates. The median internal accuracy of our relative proper motions, based on photographic plates with epoch differences up to 100 years (typically 70 years), is 1.0 milliarcsec/year (mas/a), while the calibration to an inertial system in each of the 13 fields has a median uncertainty of 1.3 mas/a. We compute the rotation from the Hipparcos proper motions (median internal errors \\e{0.9}{mas/a}) to the extragalactic reference frame represented by our absolute proper motions, using 88 stars in common. The three components of the angular velocity vector have internal errors of 0.3 mas/a. Our rotation solution has been used together with those of independent groups for the extragalactic calibration of the Hipparcos proper motion system (\\cite[Kovalevsky et al. 1996)]{kova96}. It compares favourably with the adopted mean solution. Based on observations made with the ESA Hipparcos satellite.

  4. Components of the Extragalactic Gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.; Venters, Tonia M.

    2011-01-01

    We present new theoretical estimates of the relative contributions of unresolved blazars and star-forming galaxies to the extragalactic gamma-ray background (EGB) and discuss constraints on the contributions from alternative mechanisms such as dark matter annihilation and truly diffuse gamma-ray production. We find that the Fermi source count data do not rule out a scenario in which the EGB is dominated by emission from unresolved blazars, though unresolved star-forming galaxies may also contribute significantly to the background, within order-of-magnitude uncertainties. In addition, we find that the spectrum of the unresolved star-forming galaxy contribution cannot explain the EGB spectrum found by EGRET at energies between 50 and 200 MeV, whereas the spectrum of unresolved flat spectrum radio quasars, when accounting for the energy-dependent effects of source confusion, could be consistent with the combined spectrum of the low-energy EGRET EGB measurements and the Fermi-Large Area Telescope EGB measurements.

  5. SCORPIO: a deep survey of radio emission from the stellar life-cycle

    NASA Astrophysics Data System (ADS)

    Umana, G.; Trigilio, C.; Franzen, T. M. O.; Norris, R. P.; Leto, P.; Ingallinera, A.; Buemi, C. S.; Agliozzo, C.; Cavallaro, F.; Cerrigone, L.

    2015-11-01

    Radio emission has been detected in a broad variety of stellar objects from all stages of stellar evolution. However, most of our knowledge originates from targeted observations of small samples, which are strongly biased to sources which are peculiar at other wavelengths. In order to tackle this problem we have conducted a deep 1.4 GHz survey by using the Australian Telescope Compact Array, with a net bandwidth of 1.7 GHz (1.4-3.1 GHz) , following the same observing setup as that used for the Australia Telescope Large Area Survey project, this time choosing a region more appropriate for stellar work. In this paper, the Stellar Continuum Originating from Radio Physics In Ourgalaxy (SCORPIO) project is presented as well as results from the pilot experiment. The achieved rms is 30 μJy and the angular resolution ˜10 arcsec. 614 point-like sources have been extracted just from the pilot field. Only 34 of them are classified in SIMBAD or the NASA/IPAC Extragalactic Database. About 80 per cent of the extracted sources are reported in one of the inspected catalogues and 50 per cent of them appears to belong to a reddened stellar/Galactic population. However, the evaluation of extragalactic contaminants is very difficult without further investigations. Interesting results have been obtained for extended radio sources that fall in the SCORPIO field. Many roundish-like structures (indicated as bubbles in the following) have been found, some of which are classified at other wavelengths. However, for all of these sources, our project has provided us with images of unprecedented sensitivity and angular resolution.

  6. Extragalactic cosmic rays and their signatures

    NASA Astrophysics Data System (ADS)

    Berezinsky, V.

    2014-01-01

    The signatures of UHE proton propagation through CMB radiation are pair-production dip and GZK cutoff. The visible manifestations of these two spectral features are ankle, which is intrinsic part of the dip, beginning of GZK cutoff in the differential spectrum and E in integral spectrum. Observed practically in all experiments since 1963, the ankle is usually interpreted as a feature caused by transition from galactic to extragalactic cosmic rays. Using the mass composition measured by HiRes, Telescope Array and Auger detectors at energy (1-3) EeV, calculated anisotropy of galactic cosmic rays at these energies, and the elongation curves we strongly argue against the interpretation of the ankle given above. The transition must occur at lower energy, most probably at the second knee as the dip model predicts. The other prediction of the dip model, the shape of the dip, is well confirmed by HiRes, Telescope Array (TA), AGASA and Yakutsk detectors, and, after recalibration of energies, by Auger detector. Predicted beginning of GZK cutoff and E agree well with HiRes and TA data. However, directly measured mass composition remains a puzzle. While HiRes and TA detectors observe the proton-dominated mass composition, as required by the dip model, the data of Auger detector strongly evidence for nuclei mass composition becoming progressively heavier at energy higher than 4 EeV and reaching Iron at energy about 35 EeV. The Auger-based scenario is consistent with another interpretation of the ankle at energy Ea≈4 EeV as transition from extragalactic protons to extragalactic nuclei. The heavy-nuclei dominance at higher energies may be provided by low-energy of acceleration for protons Epmax∼4 EeV and rigidity-dependent EAmax=ZEpmax for nuclei. The highest energy suppression may be explained as nuclei-photodisintegration cutoff.

  7. The Chandra Survey of Extragalactic Sources in the 3CR Catalog: X-ray Emission from Nuclei, Jets, and Hotspots in the Chandra Archival Observations

    NASA Astrophysics Data System (ADS)

    Massaro, F.; Harris, D. E.; Liuzzo, E.; Orienti, M.; Paladino, R.; Paggi, A.; Tremblay, G. R.; Wilkes, B. J.; Kuraszkiewicz, J.; Baum, S. A.; O'Dea, C. P.

    2015-09-01

    As part of our program to build a complete radio and X-ray database of all Third Cambridge catalog extragalactic radio sources, we present an analysis of 93 sources for which Chandra archival data are available. Most of these sources have already been published. Here we provide a uniform re-analysis and present nuclear X-ray fluxes and X-ray emission associated with radio jet knots and hotspots using both publicly available radio images and new radio images that have been constructed from data available in the Very Large Array archive. For about 1/3 of the sources in the selected sample, a comparison between the Chandra and radio observations was not reported in the literature: we find X-ray detections of 2 new radio jet knots and 17 hotspots. We also report the X-ray detection of extended emission from the intergalactic medium for 15 galaxy clusters.

  8. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  9. The Taiwan Extragalactic Astronomical Data Center

    NASA Astrophysics Data System (ADS)

    Foucaud, S.; Hashimoto, Y.; Tsai, M.-F.; Kamennoff, N.; TWEA-DC Team

    2013-10-01

    Founded in 2010, the Taiwan Extragalactic Astronomical Data Center (TWEA-DC) has for its goal to provide access to large amount of data for the Taiwanese and International community, focusing its efforts on Extragalactic science. In continuation with individual efforts in Taiwan over the past few years, this is the first stepping-stone towards the building of a National Virtual Observatory. Taking advantage of our own fast indexing algorithm (BLINK), based on a octahedral meshing of the sky coupled with a very fast kd-tree and a clever parallelization amongst available resources, TWEA-DC will provide, from spring 2013, a service of “on-the-fly” matching, between on-site and user-based catalogs. We will also offer access to public and private raw and reducible data available to the Taiwanese community. Finally, we are developing high-end on-line analysis tools, such as an automated photometric redshifts and SED fitting code (APz), and an automated groups and clusters finder (APFoF).

  10. Deep VLA Images of the HH 124 IRS Radio Cluster and Its Surroundings, and a New Determination of the Distance to NGC 2264

    NASA Astrophysics Data System (ADS)

    Dzib, Sergio A.; Loinard, Laurent; Rodríguez, Luis F.; Galli, Phillip

    2014-06-01

    We present new deep (σ ~ 6 μJy) radio images of the HH 124 IRS radio cluster at 4.8 and 7.5 GHz. We detect a total of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determine the nature of the sources and of their radio emission. A proper motion study was also performed for several of these radio sources using previously reported radio observations. Our analysis shows that 11 radio sources can be associated with Galactic objects, most of them probably young stars. Interestingly, 8 of these sources are in an area less than 1 arcmin2 in size. The importance of such compact clusters resides in that all of its members can be observed in a single pointing with most telescopes and are, therefore, ideal for multi-wavelength studies of variability. Another 4 of the detected sources are clearly extragalactic. Finally, we propose from statistical arguments that out of the remaining sources, about 10 are Galactic, but our study does not allow us to identify which of the sources fall in that specific category. The relatively large proper motions observed for the sources in HH 124 IRS suggest that this region is located at about 400 pc from the Sun. This is significantly smaller than the ~800-900 pc distance usually assigned to the nearby open cluster NGC 2264 with which HH 124 is thought to be associated. However, a reanalysis of the Hipparcos parallaxes for members of NGC 2264, a convergent point approach, and a kinematic analysis all argue in favor of a distance of the order of 400 pc for NGC 2264 as well.

  11. Deep VLA images of the HH 124 IRS radio cluster and its surroundings, and a new determination of the distance to NGC 2264

    SciTech Connect

    Dzib, Sergio A.; Loinard, Laurent; Rodríguez, Luis F.; Galli, Phillip

    2014-06-20

    We present new deep (σ ∼ 6 μJy) radio images of the HH 124 IRS radio cluster at 4.8 and 7.5 GHz. We detect a total of 50 radio sources, most of them compact. Variability and spectral indices were analyzed in order to determine the nature of the sources and of their radio emission. A proper motion study was also performed for several of these radio sources using previously reported radio observations. Our analysis shows that 11 radio sources can be associated with Galactic objects, most of them probably young stars. Interestingly, 8 of these sources are in an area less than 1 arcmin{sup 2} in size. The importance of such compact clusters resides in that all of its members can be observed in a single pointing with most telescopes and are, therefore, ideal for multi-wavelength studies of variability. Another 4 of the detected sources are clearly extragalactic. Finally, we propose from statistical arguments that out of the remaining sources, about 10 are Galactic, but our study does not allow us to identify which of the sources fall in that specific category. The relatively large proper motions observed for the sources in HH 124 IRS suggest that this region is located at about 400 pc from the Sun. This is significantly smaller than the ∼800-900 pc distance usually assigned to the nearby open cluster NGC 2264 with which HH 124 is thought to be associated. However, a reanalysis of the Hipparcos parallaxes for members of NGC 2264, a convergent point approach, and a kinematic analysis all argue in favor of a distance of the order of 400 pc for NGC 2264 as well.

  12. A CHANDRA SNAPSHOT SURVEY FOR 3C RADIO GALAXIES WITH REDSHIFTS BETWEEN 0.3 AND 0.5

    SciTech Connect

    Massaro, F.; Harris, D. E.; Paggi, A.; Tremblay, G. R.; Liuzzo, E.; Bonafede, A.

    2013-05-01

    This paper contains an analysis of short Chandra observations of 19 3C sources with redshifts between 0.3 and 0.5 not previously observed in the X-rays. This sample is part of a project to obtain Chandra data for all of the extragalactic sources in the 3C catalog. Nuclear X-ray intensities as well as any X-ray emission associated with radio jet knots, hotspots, or lobes have been measured in three energy bands: soft, medium, and hard. Standard X-ray spectral analysis for the four brightest nuclei has also been performed. X-ray emission was detected for all the nuclei of the radio sources in the current sample with the exception of 3C 435A. There is one compact steep spectrum source while all the others are FR II radio galaxies. X-ray emission from two galaxy clusters (3C 19 and 3C 320), from six hotspots in four radio galaxies (3C 16, 3C 19, 3C 268.2, 3C 313), and extended X-ray emission on kiloparsec scales in 3C 187 and 3C 313, has been detected.

  13. A repeating fast radio burst

    NASA Astrophysics Data System (ADS)

    Spitler, L. G.; Scholz, P.; Hessels, J. W. T.; Bogdanov, S.; Brazier, A.; Camilo, F.; Chatterjee, S.; Cordes, J. M.; Crawford, F.; Deneva, J.; Ferdman, R. D.; Freire, P. C. C.; Kaspi, V. M.; Lazarus, P.; Lynch, R.; Madsen, E. C.; McLaughlin, M. A.; Patel, C.; Ransom, S. M.; Seymour, A.; Stairs, I. H.; Stappers, B. W.; van Leeuwen, J.; Zhu, W. W.

    2016-03-01

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  14. A repeating fast radio burst.

    PubMed

    Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-03-10

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star. PMID:26934226

  15. A compact 10 kW, 476 MHz solid state radio frequency amplifier for pre-buncher cavity of free electron laser injector linear accelerator

    SciTech Connect

    Mohania, Praveen; Mahawar, Ashish; Shrivastava, Purushottam; Gupta, P. D.

    2013-09-15

    A 10 kW, 476 MHz, 0.1% duty cycle solid state RF amplifier system for driving sub-harmonic, pre-buncher cavity of IR-FEL injector LINAC, has been developed at RRCAT. The 10 kW power is achieved by combining output of eight 1400 W amplifier modules using 8-way planar corporate combiner. The solid state amplifier modules have been developed using 50 V RF LDMOS transistors which although meant for push-pull operation are being used in single ended configuration with matching circuit developed on a thin (25 mils), high dielectric constant (9.7), low loss microwave laminate with an aim to have a compact structure. Ease of fabrication, modularity, small size, and low cost are the important features of this design which could be used as a template for low duty cycle medium to high pulsed power UHF amplifier system.

  16. A compact 10 kW, 476 MHz solid state radio frequency amplifier for pre-buncher cavity of free electron laser injector linear accelerator

    NASA Astrophysics Data System (ADS)

    Mohania, Praveen; Mahawar, Ashish; Shrivastava, Purushottam; Gupta, P. D.

    2013-09-01

    A 10 kW, 476 MHz, 0.1% duty cycle solid state RF amplifier system for driving sub-harmonic, pre-buncher cavity of IR-FEL injector LINAC, has been developed at RRCAT. The 10 kW power is achieved by combining output of eight 1400 W amplifier modules using 8-way planar corporate combiner. The solid state amplifier modules have been developed using 50 V RF LDMOS transistors which although meant for push-pull operation are being used in single ended configuration with matching circuit developed on a thin (25 mils), high dielectric constant (9.7), low loss microwave laminate with an aim to have a compact structure. Ease of fabrication, modularity, small size, and low cost are the important features of this design which could be used as a template for low duty cycle medium to high pulsed power UHF amplifier system.

  17. A compact 10 kW, 476 MHz solid state radio frequency amplifier for pre-buncher cavity of free electron laser injector linear accelerator.

    PubMed

    Mohania, Praveen; Mahawar, Ashish; Shrivastava, Purushottam; Gupta, P D

    2013-09-01

    A 10 kW, 476 MHz, 0.1% duty cycle solid state RF amplifier system for driving sub-harmonic, pre-buncher cavity of IR-FEL injector LINAC, has been developed at RRCAT. The 10 kW power is achieved by combining output of eight 1400 W amplifier modules using 8-way planar corporate combiner. The solid state amplifier modules have been developed using 50 V RF LDMOS transistors which although meant for push-pull operation are being used in single ended configuration with matching circuit developed on a thin (25 mils), high dielectric constant (9.7), low loss microwave laminate with an aim to have a compact structure. Ease of fabrication, modularity, small size, and low cost are the important features of this design which could be used as a template for low duty cycle medium to high pulsed power UHF amplifier system. PMID:24089846

  18. The Spitzer Extragalactic Representative Volume Survey

    NASA Astrophysics Data System (ADS)

    Lacy, Mark; SERVS Team

    2009-05-01

    The Spitzer Extragalactic Representative Volume Survey (SERVS) will image a total of 18 deg2 of sky to micro-Jansky depth in the [3.6] and [4.5] micron bands split amongst the SWIRE ELAIS-S1, ELAIS-N1, XMM-LSS, Lockman and CDFS fields. SERVS will have substantial overlap with the VISTA/VIDEO and UKIDSS DXS near-infrared surveys, and the Hermes far-infrared survey with Herschel. Key science goals include: understanding stellar mass assembly in massive galaxies from z 5 to the present across a wide range of environments, studying the effects of AGN feedback on the formation of massive galaxies, and finding quasars at z>6.5. In this talk I shall describe the science possible with SERVS, the data taking and analysis schedule, plans for bandmerging with other surveys, and eventual public release.

  19. The VISTA Deep Extragalactic Observations (VIDEO) Survey

    NASA Astrophysics Data System (ADS)

    Jarvis, M. J.; Häußler, B.; McAlpine, K.

    2013-12-01

    The VIDEO survey is designed to answer key questions regarding the formation and evolution of galaxies, in particular the role of accretion onto black holes and how galaxy evolution may vary depending on environment. VIDEO undertakes deep near-infrared imaging over three well-observed extragalactic fields allowing in-depth study of galaxy evolution over 1 < z < 4, linking the shallower VST and VISTA surveys with the UltraVISTA survey. The area and depth of the VIDEO survey enables the detection of the bulk of the luminosity density arising from galaxies over 90% of the history of the Universe, as well as the most massive galaxies at all epochs and any associated accretion activity. A few scientific highlights from the early VIDEO data are provided.

  20. Deep Extragalactic X-Ray Surveys

    NASA Astrophysics Data System (ADS)

    Brandt, W. N.; Hasinger, G.

    2005-09-01

    Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting active galactic nuclei (AGN) is assessed. Some key results from deep surveys are highlighted, including (a) measurements of AGN evolution and the growth of supermassive black holes, (b) constraints on the demography and physics of high-redshift AGN, (c) the X-ray AGN content of infrared and submillimeter galaxies, and (d) X-ray emission from distant starburst and normal galaxies. We also describe some outstanding problems and future prospects for deep extragalactic X-ray surveys.

  1. HIPPARCOS Extragalactic Link: the Potsdam Contribution

    NASA Astrophysics Data System (ADS)

    Hirte, S.; Schilbach, E.; Scholz, R.-D.

    1997-08-01

    The Potsdam group was involved in the link of the Hipparcos proper motion system to an extragalactic reference system. Absolute proper motions were derived from measurements of photographic plates taken mainly with the Tautenburg Schmidt telescope (134/200/400 cm). In 24 fields included in different Potsdam proper motion programmes and well distributed over the northern sky, 360 Hipparcos stars were measured. In each field of about 10 square degrees a large number of galaxies was used for the link. Detailed investigations showed that the proper motion determination of bright stars is affected by systematic magnitude dependent errors. Therefore, only the 256 stars with B >= 9.0 were used to determine the spin parameters of the Hipparcos system. The accuracy of our final results is 0.5 mas/yr for all three spin parameters. The results are in good agreement with the VLBI link parameters and the synthesized solution by Kovalevsky et al. (1997).

  2. Adult Compacts.

    ERIC Educational Resources Information Center

    Further Education Unit, London (England).

    This bulletin focuses on adult compacts, three-way agreements among employers, potential employees, and trainers to provide the right kind of quality training to meet the employers' requirements. Part 1 is an executive summary of a report of the Adult Compacts Project, which studied three adult compacts in Birmingham and Loughborough, England, and…

  3. The Herschel Multi-tiered Extragalactic Survey: HerMES

    NASA Technical Reports Server (NTRS)

    Oliver, S.J.; Bock, J.; Altieri, B.; Amblard, A.; Arumugam, V.; Aussel, H.; Babbedge, T.; Beelen, A.; Bethermin, M.; Blain, A.; Boselli, A.; Bridge, C.; Brisbin, D; Buat, V.; Burgarella, D.; Castro-Rodriguez, N.; Cava, A.; Chanial, P.; Cirasuolo, M.; Clements, D. L.; Conley, A.; Conversi, L.; Dwek, E.; Levenson, L.; Nguyen, H. T.

    2012-01-01

    The Herschel Multi-tiered Extragalactic Survey, HerMES, is a legacy program designed to map a set of nested fields totalling approx. 380 deg(exp 2). Fields range in size from 0.01 to approx. 20 deg (exp 2), using Herschel-SPIRE (at 250, 350 and 500 micron), and Herschel-PACS (at 100 and 160 micron), with an additional wider component of 270 deg. (exp. 2) with SPIRE alone. These bands cover the peak of the redshifted thermal spectral energy distribution from interstellar dust and thus capture the re-processed optical and ultra-violet radiation from star formation that has been absorbed by dust, and are critical for forming a complete multi-wavelength understanding of galaxy formation and evolution. The survey will detect of order 100,000 galaxies at 5-sigma in some of the best studied fields in the sky. Additionally, HerMES is closely coordinated with the PACS Evolutionary Probe survey. Making maximum use of the full spectrum of ancillary data, from radio to X-ray wavelengths, it is designed to: facilitate redshift determination; rapidly identify unusual objects; and understand the relationships between thermal emission from dust and other processes. Scientific questions HerMES will be used to answer include: the total infrared emission of galaxies; the evolution of the luminosity function; the clustering properties of dusty galaxies; and the properties of populations of galaxies which lie below the confusion limit through lensing and statistical techniques. This paper defines the survey observations and data products, outlines the primary scientific goals of the HerMES team, and reviews some of the early results.

  4. Search for Extragalactic Point Sources in WMAP First Year Data

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wright, E. L.

    2005-12-01

    In 2003, Bennett et al. made a search for point sources in the WMAP maps and provided a catalog of 208 detected sources (with 98% reliability). These sources tend to be radio galaxies and quasars, and most of them have strong radiation at the K, Ka and Q bands, but not necessarily at the V and W bands. Here we present a new search for extragalactic point sources in V- and W-band full sky WMAP maps, using a different approach that cancels the ``noise'' due to the CMB anisotropy signal. 29 point sources are found in our study including 16 WMAP point sources, which is a strong proof of the feasibility and reliability of our method. Also since in our method the major noise contribution is due to random errors in the observations which can be minimized by repeated observations, the sensitivity of our study is expected to be greatly enhanced when more years of WMAP data are available. A comparison to previous surveys shows that 5 of our point source candidates have nearby infrared sources which cannot be positively associated due to insufficient spectral data; and another 3 do not have any companions in a 4-arcmin radius vicinity, which are most likely sources undetected before. We have proposed VLA X-band observations for these unidentified sources. The observation results should be available at the time of this meeting and will be presented along with the WMAP analysis. We acknowledge the use of the Legacy Archive for Microwave Background Data Analysis (LAMBDA). Support for LAMBDA is provided by the NASA Office of Space Science.

  5. Radio Jet Feedback and Star Formation in Heavily Obscured, Hyperluminous Quasars at Redshifts ∼ 0.5–3. I. ALMA Observations

    NASA Astrophysics Data System (ADS)

    Lonsdale, Carol J.; Lacy, M.; Kimball, A. E.; Blain, A.; Whittle, M.; Wilkes, B.; Stern, D.; Condon, J.; Kim, M.; Assef, R. J.; Tsai, C.-W.; Efstathiou, A.; Jones, S.; Eisenhardt, P.; Bridge, C.; Wu, J.; Lonsdale, Colin J.; Jones, K.; Jarrett, T.; Smith, R.

    2015-11-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm (345 GHz) data for 49 high-redshift (0.47 < z < 2.85), luminous (11.7\\lt {log}({L}{{bol}}/{L}ȯ )\\lt 14.2) radio-powerful active galactic nuclei (AGNs), obtained to constrain cool dust emission from starbursts concurrent with highly obscured radiative-mode black hole (BH) accretion in massive galaxies that possess a small radio jet. The sample was selected from the Wide-field Infrared Survey Explorer with extremely steep (red) mid-infrared colors and with compact radio emission from NVSS/FIRST. Twenty-six sources are detected at 870 μm, and we find that the sample has large mid- to far-infrared luminosity ratios, consistent with a dominant and highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7\\lt {log}({P}\\text{3.0 GHz}/{{{W}} {Hz}}-1)\\lt 27.3, and all sources are radio-intermediate or radio-loud. BH mass estimates are 7.7 < log(MBH/M⊙) < 10.2. The rest-frame 1–5 μm spectral energy distributions are very similar to the “Hot DOGs” (hot dust-obscured galaxies), and steeper (redder) than almost any other known extragalactic sources. ISM masses estimated for the ALMA-detected sources are 9.9 < log (MISM/M⊙) < 11.75 assuming a dust temperature of 30 K. The cool dust emission is consistent with star formation rates reaching several thousand M⊙ yr‑1, depending on the assumed dust temperature, but we cannot rule out the alternative that the AGN powers all the emission in some cases. Our best constrained source has radiative transfer solutions with approximately equal contributions from an obscured AGN and a young (10–15 Myr) compact starburst.

  6. Radio Jet Feedback and Star Formation in Heavily Obscured, Hyperluminous Quasars at Redshifts ˜ 0.5-3. I. ALMA Observations

    NASA Astrophysics Data System (ADS)

    Lonsdale, Carol J.; Lacy, M.; Kimball, A. E.; Blain, A.; Whittle, M.; Wilkes, B.; Stern, D.; Condon, J.; Kim, M.; Assef, R. J.; Tsai, C.-W.; Efstathiou, A.; Jones, S.; Eisenhardt, P.; Bridge, C.; Wu, J.; Lonsdale, Colin J.; Jones, K.; Jarrett, T.; Smith, R.

    2015-11-01

    We present Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm (345 GHz) data for 49 high-redshift (0.47 < z < 2.85), luminous (11.7\\lt {log}({L}{{bol}}/{L}⊙ )\\lt 14.2) radio-powerful active galactic nuclei (AGNs), obtained to constrain cool dust emission from starbursts concurrent with highly obscured radiative-mode black hole (BH) accretion in massive galaxies that possess a small radio jet. The sample was selected from the Wide-field Infrared Survey Explorer with extremely steep (red) mid-infrared colors and with compact radio emission from NVSS/FIRST. Twenty-six sources are detected at 870 μm, and we find that the sample has large mid- to far-infrared luminosity ratios, consistent with a dominant and highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7\\lt {log}({P}\\text{3.0 GHz}/{{{W}} {Hz}}-1)\\lt 27.3, and all sources are radio-intermediate or radio-loud. BH mass estimates are 7.7 < log(MBH/M⊙) < 10.2. The rest-frame 1-5 μm spectral energy distributions are very similar to the “Hot DOGs” (hot dust-obscured galaxies), and steeper (redder) than almost any other known extragalactic sources. ISM masses estimated for the ALMA-detected sources are 9.9 < log (MISM/M⊙) < 11.75 assuming a dust temperature of 30 K. The cool dust emission is consistent with star formation rates reaching several thousand M⊙ yr-1, depending on the assumed dust temperature, but we cannot rule out the alternative that the AGN powers all the emission in some cases. Our best constrained source has radiative transfer solutions with approximately equal contributions from an obscured AGN and a young (10-15 Myr) compact starburst.

  7. Weak and compact radio emission in early massive star formation regions: an ionized jet toward G11.11–0.12P1

    SciTech Connect

    Rosero, V.; Hofner, P.; McCoy, M.; Kurtz, S.; Loinard, L.; Carrasco-González, C.; Rodríguez, L. F.; Menten, K. M.; Wyrowski, F.; Araya, E. D.; Cesaroni, R.; Ellingsen, S. P.

    2014-12-01

    We report 1.3 cm and 6 cm continuum observations toward the massive proto-stellar candidate G11.11–0.12P1 using the Karl G. Jansky Very Large Array. We detect a string of four unresolved radio continuum sources coincident with the mid-infrared source in G11P1. The continuum sources have positive spectral indices consistent with a thermal (free-free) ionized jet. The most likely origins of the ionized gas are shocks due to the interaction of a stellar wind with the surrounding high-density material. We also present NIR United Kingdom Infrared Telescope (UKIRT) archival data that show an extended structure detected only at K band (2.2 μm), which is oriented perpendicular to the jet, and that may be scattered light from a circumstellar disk around the massive protostar. Our observations plus the UKIRT archival data thus provide new evidence that a disk/jet system is present in the massive proto-stellar candidate located in the G11.11–0.12P1 core.

  8. Radio astronomers, X-ray astronomers and the space telescope

    NASA Technical Reports Server (NTRS)

    Longair, M. S.

    1979-01-01

    The use of the Space Telescope and the study of objects in the radio and X-ray wavebands, particularly extragalactic objects, are discussed. The scientific objectives of a number of projects which involve observations with the Space Telescope are described.

  9. Early Radio Astronomy in the USSR

    NASA Astrophysics Data System (ADS)

    Kellermann, Kenneth I.

    2007-12-01

    As in many other countries, radio astronomy in the Soviet Union began as an outgrowth of wartime radar research. The early leaders of Soviet radio astronomy, including Simon Braude, Vladimir Kotelnikov, Vladimir Troitskii, and Viktor Vitkevitch, all began their careers during WWII. Although the theoretical contributions of people like Iosef Shklovsky and Vitaly Ginzburg were well known in the West, the early experimental and observational programs received much less attention, partially the result of cold war military secrecy. When they were noticed, the Soviet observations were largely ignored or declared wrong. We will discuss the controversial Soviet contributions to the detection of polarized cosmic radio emission, the development of very long baseline interferometry, the prediction and verification of radio recombination lines, and the first detection of variability in an extragalactic radio source.

  10. EXAM: A search for extragalactic antimatter

    SciTech Connect

    Crary, D.J.

    1991-01-01

    This thesis presents results from a search for extragalactic antimatter in the cosmic rays (the EXAM experiment). The reasons for undertaking a search for antimatter are given, along with various arguments that indicate that a antimatter fraction of 10{sup {minus}6} {minus} 10{sup {minus}7} in the cosmic-ray flux at earth would not be inconsistent with current antimatter limits obtained from cosmic-ray experiments or with limits set by gamma-ray observations. An experimental technique sensitive to antinuclei with charge Z near iron (Z = 26) is reviewed. This technique uses a combination of active detectors (scintillators, Cerenkov counters) and CR-39 track-etch detectors to provide a unique signature for antimatter detection at a level consistent with the flux estimates given above. This is followed by description of the implementation of this technique (the EXAM detector), along with a summary of the data analysis to date. Directions for future work are described. A detailed description of the microscope system used in the automated analysis of the CR-39 plastic is presented.

  11. Extragalactic Surveys with NuSTAR

    NASA Astrophysics Data System (ADS)

    Boydstun, Kristen; Ajello, M.; Alexander, D.; Assef, R. J.; Ballantyne, D. R.; Balokovic, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Christensen, F.; Civano, F. M.; Comastri, A.; Craig, W.; Del Moro, A.; Elvis, M.; Fiore, F.; Hailey, C. J.; Harrison, F.; Helfand, D. J.; Hickox, R. C.; LaMassa, S. M.; Lansbury, G.; Luo, B.; Madsen, K.; Markwardt, C.; Mullaney, J.; Puccetti, S.; Saez, C.; Stern, D.; Tagliaferri, G.; Treister, E.; Urry, C. M.; Walton, D.; Zhang, W.; NuSTAR Science Team

    2013-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, is opening the high energy X-ray sky for sensitive study for the first time. Soft X-ray telescopes like Chandra and XMM-Newton have peered deep into the X-ray universe at low energies and have resolved much of the X-ray background below a few keV. However, extrapolating such work to higher energies indicates that a significant population of heavily-obscured AGN remain undetected in the soft X-rays, but should be detectable in the hard X-ray band. By focusing X-rays at higher energy, up to 79 keV, NuSTAR will study the X-ray background at its 30 keV peak. The NuSTAR mission baselines three nested extragalactic surveys, a very deep 200 ks), pencil-beam survey of the Extended Chandra Deep Field-South (ECDFS) field, a moderate depth 50 ks) survey of the COSMOS field, and a shallow 10 ks) survey of 100 bright Swift/BAT AGN. We discuss plans, predictions and early results of the ECDFS and COSMOS programs. Discussion of the Swift/BAT program is presented in the companion poster by T.-N. Lu.

  12. The VISTA Deep Extragalactic Observations (VIDEO) Survey

    NASA Astrophysics Data System (ADS)

    Bonfield, David G.; Jarvis, M. J.; VIDEO Consortium

    2010-01-01

    The VISTA Deep Extragalactic Observations (VIDEO) survey is a 12 sq. degree, Z,Y,J,H,Ks survey, to be carried out with the new ESO Visible and Infrared Survey Telescope for Astronomy (VISTA). The survey is specifically designed to enable galaxy and cluster/structure evolution to be traced as a function of both epoch and environment from the present day out to redshift z=4, and AGN and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully probe the epoch of activity in the Universe, where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialise. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it is most crucial. The three survey fields (ELAIS-S1, XMM-LSS, and CDF-S) have been chosen to maximise overlap with complementary multiwavelength data, and, as an ESO public survey, for future follow-up from southern facilities including the VLT, APEX, and ALMA. We have also recently established an agreement with the Dark Energy Survey Supernova Survey which will allow rest-frame optical light curves to be measured for distant supernovae, thus negating some of the biases inherent to optical surveys.

  13. The VLBA Fast Radio Transient Experiment: Progress and Early Results

    NASA Astrophysics Data System (ADS)

    Wayth, Randall B.; Brisken, Walter F.; Deller, Adam T.; Majid, Walid A.; Thompson, David R.; Tingay, Steven J.; Wagstaff, Kiri L.

    2012-04-01

    Motivated by recent discoveries of isolated, dispersed radio pulses of possible extragalactic origin, we are performing a commensal search for short-duration (ms) continuum radio pulses using the Very Long Baseline Array (VLBA). The geographically separated antennæ of the VLBA make the system robust to local RFI and allow events to be verified and localised on the sky with milli-arcsec accuracy. We report sky coverage and detection limits from the experiment to date.

  14. The peculiar radio source M17 JVLA 35

    SciTech Connect

    Rodríguez, L. F.; Carrasco-González, C.; Montes, G.; Tapia, M.

    2014-07-01

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

  15. Jet Emission in Young Radio Sources: A Fermi Large Area Telescope Gamma-Ray View

    NASA Astrophysics Data System (ADS)

    Migliori, G.; Siemiginowska, A.; Kelly, B. C.; Stawarz, Ł.; Celotti, A.; Begelman, M. C.

    2014-01-01

    We investigate the contribution of the beamed jet component to the high-energy emission in young and compact extragalactic radio sources, focusing for the first time on the γ-ray band. We derive predictions on the γ-ray luminosities associated with the relativistic jet assuming a leptonic radiative model. The high-energy emission is produced via Compton scattering by the relativistic electrons in a spherical region at the considered scales (lsim10 kpc). Simulations show a wide range of γ-ray luminosities, with intensities up to ~1046-1048 erg s-1 depending on the assumed jet parameters. We find a highly linear relation between the simulated X-ray and γ-ray luminosities that can be used to select candidates for γ-ray detection. We compare the simulated luminosity distributions in the radio, X-ray, and γ-ray regimes with observations for the largest sample of X-ray-detected young radio quasars. Our analysis of ~4-yr Fermi Large Area Telescope (LAT) data does not yield any statistically significant detections. However, the majority of the model-predicted γ-ray fluxes for the sample are near or below the current Fermi-LAT flux threshold and compatible with the derived upper limits. Our study gives constraints on the minimum jet power (L jet, kin/L disk > 0.01) of a potential jet contribution to the X-ray emission in the most compact sources (lsim 1 kpc) and on the particle-to-magnetic field energy density ratio that are in broad agreement with equipartition assumptions.

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

    SciTech Connect

    Migliori, G.; Siemiginowska, A.; Kelly, B. C.; Stawarz, Ł.; Celotti, A.; Begelman, M. C.

    2014-01-10

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

  17. The Spitzer Extragalactic Representative Volume Survey (SERVS): Survey Definition and Goals

    NASA Astrophysics Data System (ADS)

    Mauduit, J.-C.; Lacy, M.; Farrah, D.; Surace, J. A.; Jarvis, M.; Oliver, S.; Maraston, C.; Vaccari, M.; Marchetti, L.; Zeimann, G.; Gonzáles-Solares, E. A.; Pforr, J.; Petric, A. O.; Henriques, B.; Thomas, P. A.; Afonso, J.; Rettura, A.; Wilson, G.; Falder, J. T.; Geach, J. E.; Huynh, M.; Norris, R. P.; Seymour, N.; Richards, G. T.; Stanford, S. A.; Alexander, D. M.; Becker, R. H.; Best, P. N.; Bizzocchi, L.; Bonfield, D.; Castro, N.; Cava, A.; Chapman, S.; Christopher, N.; Clements, D. L.; Covone, G.; Dubois, N.; Dunlop, J. S.; Dyke, E.; Edge, A.; Ferguson, H. C.; Foucaud, S.; Franceschini, A.; Gal, R. R.; Grant, J. K.; Grossi, M.; Hatziminaoglou, E.; Hickey, S.; Hodge, J. A.; Huang, J.-S.; Ivison, R. J.; Kim, M.; LeFevre, O.; Lehnert, M.; Lonsdale, C. J.; Lubin, L. M.; McLure, R. J.; Messias, H.; Martínez-Sansigre, A.; Mortier, A. M. J.; Nielsen, D. M.; Ouchi, M.; Parish, G.; Perez-Fournon, I.; Pierre, M.; Rawlings, S.; Readhead, A.; Ridgway, S. E.; Rigopoulou, D.; Romer, A. K.; Rosebloom, I. G.; Rottgering, H. J. A.; Rowan-Robinson, M.; Sajina, A.; Simpson, C. J.; Smail, I.; Squires, G. K.; Stevens, J. A.; Taylor, R.; Trichas, M.; Urrutia, T.; van Kampen, E.; Verma, A.; Xu, C. K.

    2012-07-01

    We present the Spitzer Extragalactic Representative Volume Survey (SERVS), an 18 deg2 medium-deep survey at 3.6 and 4.5 μm with the postcryogenic Spitzer Space Telescope to ≈2 μJy (AB = 23.1) depth of five highly observed astronomical fields (ELAIS-N1, ELAIS-S1, Lockman Hole, Chandra Deep Field South, and XMM-LSS). SERVS is designed to enable the study of galaxy evolution as a function of environment from z ~ 5 to the present day and is the first extragalactic survey that is both large enough and deep enough to put rare objects such as luminous quasars and galaxy clusters at z gsim 1 into their cosmological context. SERVS is designed to overlap with several key surveys at optical, near- through far-infrared, submillimeter, and radio wavelengths to provide an unprecedented view of the formation and evolution of massive galaxies. In this article, we discuss the SERVS survey design, the data processing flow from image reduction and mosaicking to catalogs, and coverage of ancillary data from other surveys in the SERVS fields. We also highlight a variety of early science results from the survey. Since this article was published online on 4 August 2012, corrections have been made. An erratum appears in the October 2012 issue of the journal. The current online version was corrected on 10 October 2012.

  18. Accurate and Robust Calibration of the Extragalactic Distance Scale with the Maser Galaxy NGC4258

    NASA Astrophysics Data System (ADS)

    Greenhill, Lincoln

    2003-07-01

    The extragalactic distance scale {EDS} is defined by a comparison of Cepheid Period-Luminosity {PL} relations for nearby galaxies and the LMC, whose uncertain distance is thereby the SOLE anchor. Studies of maser sources orbiting the central black hole in the galaxy NGC4258 have provided the most accurate extragalactic distance ever {7.2+/- 0.5Mpc}. Since this distance is well determined and based on GEOMETRIC arguments, NGC4258 can provide a much needed new anchor for the EDS. We propose multi-epoch BVIH observations of NGC4258 in order to discover about 100 Cepheids and to characterize their light curves with 2-3 times greater accuracy than was previously possible with WFPC2. At 90 orbits {48 in Cycle 12; 42 in Cycle 13}, this is a relatively large program. However, the result will have a major impact on the EDS, and substantial attention must be paid to characterization and minimization of systematic errors, as from metallicity, crowding, and blending. The resulting dataset will be the most complete for Cepheids in any galaxy yet studied with HST. In an ongoing NASA-funded program {OSS-SARA}, we are using new analysis techniques and radio data to reduce uncertainty in the geometric distance to < 3% {0.07 mag}. With this improved geometric distance and the BVIH data, we will be able to calculate the zero point of the PL relation ROBUSTLY to <4% {0.09 mag}.

  19. HELP: The Herschel Extragalactic Legacy Project and The Coming of Age of Multi-wavelength Astrophysics

    NASA Astrophysics Data System (ADS)

    Vaccari, M.

    How did galaxies form and evolve? This is one of the most challenging questions in astronomy today. Answering it requires a careful combination of observational and theoretical work to reliably determine the observed properties of cosmic bodies over large portions of the distant Universe on the one hand, and accurately model the physical processes driving their evolution on the other. Most importantly, it requires bringing together disparate multi-wavelength and multi-resolution spectro-photometric datasets in an homogeneous and well-characterized manner so that they are suitable for a rigorous statistical analysis. The Herschel Extragalactic Legacy Project (HELP) funded by the EC FP7 SPACE program aims to achieve this goal by combining the expertise of optical, infrared and radio astronomers to provide a multi-wavelength database for the distant Universe as an accessible value-added resource for the astronomical community. It will do so by bringing together multi-wavelength datasets covering the 1,000 deg2 mapped by Herschel extragalactic surveys in an homogeneous and well-characterized manner, creating a joint lasting legacy from several ambitious sky surveys.

  20. ANATOMY OF HELICAL EXTRAGALACTIC JETS: THE CASE OF S5 0836+710

    SciTech Connect

    Perucho, M.; Kovalev, Y. Y.; Lobanov, A. P.; Hardee, P. E.; Agudo, I.

    2012-04-10

    Helical structures are common in extragalactic jets. They are usually attributed in the literature to periodical phenomena in the source (e.g., precession). In this work, we use very long baseline interferometry data of the radio jet in the quasar S5 0836+710 and hypothesize that the ridgeline of helical jets like this corresponds to a pressure maximum in the jet and assume that the helically twisted pressure maximum is the result of a helical wave pattern. For our study, we use observations of the jet in S5 0836+710 at different frequencies and epochs. The results show that the structures observed are physical and not generated artificially by the observing arrays. Our hypothesis that the observed intensity ridgeline can correspond to a helically twisted pressure maximum is confirmed by our observational tests. This interpretation allows us to explain jet misalignment between parsec and kiloparsec scales when the viewing angle is small, and also brings us to the conclusion that high-frequency observations may show only a small region of the jet flow concentrated around the maximum pressure ridgeline observed at low frequencies. Our work provides a potential explanation for the apparent transversal superluminal speeds observed in several extragalactic jets by means of transversal shift of an apparent core position with time.

  1. VIBRATION COMPACTION

    DOEpatents

    Hauth, J.J.

    1962-07-01

    A method of compacting a powder in a metal container is described including the steps of vibrating the container at above and below the resonant frequency and also sweeping the frequency of vibration across the resonant frequency several times thereby following the change in resonant frequency caused by compaction of the powder. (AEC)

  2. Extragalactic Jets as Electrical Circuits and Transmission Lines

    NASA Astrophysics Data System (ADS)

    Kronberg, Philipp

    2014-10-01

    I describe the first attempt to measure a current in an extended radio galaxy jet: ~1018A at ~50 kpc from the elliptical galaxy's ultra-compact nucleus. This class of jet is known to transport its magnetic energy ``intact'', up to supragalactic scales. I discuss plasma parameters for 3C303 and recent attempts to measure its jet axial current. I discuss analogies with both electrical circuits, - and transmission lines. Power is delivered into a ``load'', whose impedance, Z, is close to that of free space, and the jet power flow I2 Z is ~1035 erg s-1 - broadly consistent with astronomically measured total power outputs, luminosities and lifetimes of AGN-powered radio lobes.The current and power levels are also consistent with SMBH accretion disk model predictions by Stirling Colgate, H. Li, V. Pariev, J. Finn, and others, beginning with Lovelace 1976 (Nature). A further analogy with transmission lines shows how the supragalactic power flows can be disrupted by a complex impedance in the ``circuit.'' Reactive components in space, i.e. a complex Z, can disrupt, reflect or deflect the power flow. This could explain the wide variety of magneto-plasma configurations seen in these systems. Funded by NSERC Discovery Grant A5713.

  3. Extragalactic Sub-millimeter H2O Maser - Detection of a 321 GHz Water Maser in Circinus Galaxy

    NASA Astrophysics Data System (ADS)

    Hagiwara, Y.; Horiuchi, S.; Doi, A.; Miyoshi, M.

    2015-12-01

    We present the first detection of the extragalactic 321 GHz H2O emission towards the Circinus Galaxy, the nearby Type2 Seyfert galaxy. It is likely that the detected emission is a maser because of the narrow line shape, the compact emission (< 0.66″) and the high energy level of the transition. High velocity emission, red-shifted up to 635 km/s, was tentatively detected. The maser location of about 0.02 pc from the center of the galaxy is estimated by adopting the Kepler rotating disk model. This could be the molecular material observed closest to the central engine.

  4. The grand unified photon spectrum: A coherent view of the diffuse extragalactic background radiation

    NASA Technical Reports Server (NTRS)

    Ressell, M. Ted; Turner, Michael S.

    1989-01-01

    The spectrum of diffuse extragalactic background radiation (DEBRA) at wavelengths from 10(exp 5) to 10(exp -24) cm is presented in a coherent fashion. Each wavelength region, from the radio to ultra-high energy photons and cosmic rays, is treated both separately and as part of the grand unified photon spectrum (GUPS). A discussion of, and references to, the relevant literature for each wavelength region is included. This review should provide a useful tool for those interested in diffuse backgrounds, the epoch of galaxy formation, astrophysical/cosmological constraints to particle properties, exotic early Universe processes, and many other astrophysical and cosmological enterprises. As a worked example, researchers derive the cosmological constraints to an unstable-neutrino spies (with arbitrary branching ratio to a radiative decay mode) that follow from the GUPS.

  5. The imprint of the extragalactic background light in the gamma-ray spectra of blazars.

    PubMed

    Ackermann, M; Ajello, M; Allafort, A; Schady, P; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bellazzini, R; Blandford, R D; Bloom, E D; Borgland, A W; Bottacini, E; Bouvier, A; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Cavazzuti, E; Cecchi, C; Charles, E; Chaves, R C G; Chekhtman, A; Cheung, C C; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; de Palma, F; Dermer, C D; Digel, S W; do Couto e Silva, E; Domínguez, A; Drell, P S; Drlica-Wagner, A; Favuzzi, C; Fegan, S J; Focke, W B; Franckowiak, A; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guiriec, S; Gustafsson, M; Hadasch, D; Hayashida, M; Hays, E; Jackson, M S; Jogler, T; Kataoka, J; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Tramacere, A; Nuss, E; Greiner, J; Ohno, M; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; Ormes, J F; Paneque, D; Perkins, J S; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reyes, L C; Ritz, S; Rau, A; Romoli, C; Roth, M; Sánchez-Conde, M; Sanchez, D A; Scargle, J D; Sgrò, C; Siskind, E J; Spandre, G; Spinelli, P; Stawarz, Łukasz; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J G; Thompson, D J; Tibaldo, L; Tinivella, M; Torres, D F; Tosti, G; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Winer, B L; Wood, K S; Wood, M

    2012-11-30

    The light emitted by stars and accreting compact objects through the history of the universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited by galactic and other foreground emissions. Here, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z ∼ 1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to ultraviolet frequencies and allowed us to measure the EBL flux density in this frequency band. PMID:23118013

  6. The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Allafort, A.; Schady, P.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Bouvier, A.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Gehrels, N.; Guirec, S.; Hays, E.; McEnery, J. E.; Perkins, J. S.; Scargle, J. D.; Troja, E.

    2012-01-01

    The light emitted by stars and accreting compact objects through the history of the universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL isimportant to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are limited by galactic and other foreground emissions. Here, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z approx. 1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to ultraviolet frequencies and allowed us to measure the EBL flux density in this frequency band.

  7. Classification and list of transitions of, and observation prospects for, extragalactic methanol masers

    NASA Astrophysics Data System (ADS)

    Sobolev, A. M.

    1993-08-01

    A new classification of methanol masers based on different types of maser sources is proposed. A division into two broad classes, with the designations of the generally accepted classification taken into account, is suggested. Class I consists of GMCs and their large-scale fragments and clumps comprising GCM hot cores. Class II contains sources connected with the boundaries of compact HII regions. Results of statistical equilibrium calculations for methanol masers as well as regularities of torsional pumping of Class II masers are considered. It is shown that the most promising observations, from the standpoint of the search for extragalactic methanol masers, are those of starburst galaxies in the 4(-1)-3(0)E and 5(-1)-4(0)E lines.

  8. Absolute Calibration of the Radio Astronomy Flux Density Scale at 22 to 43 GHz Using Planck

    NASA Astrophysics Data System (ADS)

    Partridge, B.; López-Caniego, M.; Perley, R. A.; Stevens, J.; Butler, B. J.; Rocha, G.; Walter, B.; Zacchei, A.

    2016-04-01

    The Planck mission detected thousands of extragalactic radio sources at frequencies from 28 to 857 GHz. Planck's calibration is absolute (in the sense that it is based on the satellite’s annual motion around the Sun and the temperature of the cosmic microwave background), and its beams are well characterized at sub-percent levels. Thus, Planck's flux density measurements of compact sources are absolute in the same sense. We have made coordinated Very Large Array (VLA) and Australia Telescope Compact Array (ATCA) observations of 65 strong, unresolved Planck sources in order to transfer Planck's calibration to ground-based instruments at 22, 28, and 43 GHz. The results are compared to microwave flux density scales currently based on planetary observations. Despite the scatter introduced by the variability of many of the sources, the flux density scales are determined to 1%–2% accuracy. At 28 GHz, the flux density scale used by the VLA runs 2%–3% ± 1.0% below Planck values with an uncertainty of +/- 1.0%; at 43 GHz, the discrepancy increases to 5%–6% ± 1.4% for both ATCA and the VLA.

  9. WFIRST Extragalactic Potential Observations (EXPO) Science Investigation Team

    NASA Astrophysics Data System (ADS)

    Robertson, Brant

    The Wide-Field InfraRed Survey Telescope (WFIRST) holds tremendous promise as a space observatory for extragalactic astrophysics beyond cosmological surveys. The WFIRST Extragalactic Potential Observations (EXPO) Science Investigation Team will identify the most pressing and scientifically compelling Guest Investigator and Guest Observer projects with WFIRST to address a range of exciting outstanding issues in galaxy formation, from the epoch of reionization to galaxy-galaxy lensing, the discovery of exotic supernovae and luminous active galaxies, and charting the chemical evolution of galaxies. The identified EXPO GI projects will help maximize the scientific return of the WFIRST cosmological surveys, and supply innovative ideas and methods for archival research that leverages the WFIRST dataset. The EXPO team will also evaluate the science payoff of translating previous successful space telescope surveys to the era of WFIRST, helping us to realize the full power of WFIRST for extragalactic astronomy through the competed GO programs. The WFIRST-EXPO team consists of world-wide experts in designing and executing space-based extragalactic programs, multi-object spectroscopic campaigns in the optical and infrared, and theoretical modeling of galaxy formation, exotic supernovae, and reionization. In support of WFIRST before Critical Design Review, WFIRST-EXPO will 1) develop and publicly release tools to generate mock catalogs for planning extragalactic astrophysics investigations with the HLS (GI) and GO community programs, 2) simulate images for modeling medium- and ultra-deep extragalactic GO programs, 3) develop and publicly release work flows for planning and evaluating the science return of potential extragalactic GI/GO programs, 4) perform case studies of medium- and ultra-deep imaging and spectroscopic GO/GI programs, 5) evaluate WFIRST design choices that influence extragalactic science return, and 6) serve as liaisons to James Webb Space Telescope, Large

  10. A catalogue of AKARI FIS BSC extragalactic objects

    NASA Astrophysics Data System (ADS)

    Marton, Gabor; Toth, L. Viktor; Gyorgy Balazs, Lajos

    2015-08-01

    We combined photometric data of about 70 thousand point sources from the AKARI Far-Infrared Surveyor Bright Source Catalogue with AllWISE catalogue data to identify galaxies. We used Quadratic Discriminant Analysis (QDA) to classify our sources. The classification was based on a 6D parameter space that contained AKARI [F65/F90], [F90/F140], [F140/F160] and WISE W1-W2 colours along with WISE W1 magnitudes and AKARI [F140] flux values. Sources were classified into 3 main objects types: YSO candidates, evolved stars and galaxies. The training samples were SIMBAD entries of the input point sources wherever an associated SIMBAD object was found within a 30 arcsecond search radius. The QDA resulted more than 5000 AKARI galaxy candidate sources. The selection was tested cross-correlating our AKARI extragalactic catalogue with the Revised IRAS-FSC Redshift Catalogue (RIFSCz). A very good match was found. A further classification attempt was also made to differentiate between extragalactic subtypes using Support Vector Machines (SVMs). The results of the various methods showed that we can confidently separate cirrus dominated objects (type 1 of RIFSCz). Some of our “galaxy candidate” sources are associated with 2MASS extended objects, and listed in the NASA Extragalactic Database so far without clear proofs of their extragalactic nature. Examples will be presented in our poster. Finally other AKARI extragalactic catalogues will be also compared to our statistical selection.

  11. The Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey

    NASA Technical Reports Server (NTRS)

    Marriage, T. A.; Juin, J. B.; Lin, Y. T.; Marsden, D.; Nolta, M. R.; Partridge, B.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.; Barrientos, L. F.; Battistelli, E. S.; Bond, J. R.; Brown, B.; Burger, B.; Chervenak, J.; Das, S.; Devlin, M. J.; Dicker, S. R.; Doriese, W. B.; Dunkley, J.; Dunner, R.; Essinger-Hileman, T.; Fisher, R. P.; Fowler, J. W.

    2011-01-01

    We report on extragalactic sources detected in a 455 square-degree map of the southern sky made with data at a frequency of 148 GHz from the Atacama Cosmology Telescope 2008 observing season. We provide a catalog of 157 sources with flux densities spanning two orders of magnitude: from 15 mJy to 1500 mJy. Comparison to other catalogs shows that 98% of the ACT detections correspond to sources detected at lower radio frequencies. Three of the sources appear to be associated with the brightest cluster galaxies of low redshift X-ray selected galaxy clusters. Estimates of the radio to mm-wave spectral indices and differential counts of the sources further bolster the hypothesis that they are nearly all radio sources, and that their emission is not dominated by re-emission from warm dust. In a bright (> 50 mJy) 148 GHz-selected sample with complete cross-identifications from the Australia Telescope 20 GHz survey, we observe an average steepening of the spectra between .5, 20, and 148 GHz with median spectral indices of alp[ha (sub 5-20) = -0.07 +/- 0.06, alpha (sub 20-148) -0.39 +/- 0.04, and alpha (sub 5-148) = -0.20 +/- 0.03. When the measured spectral indices are taken into account, the 148 GHz differential source counts are consistent with previous measurements at 30 GHz in the context of a source count model dominated by radio sources. Extrapolating with an appropriately rescaled model for the radio source counts, the Poisson contribution to the spatial power spectrum from synchrotron-dominated sources with flux density less than 20 mJy is C(sup Sync) = (2.8 +/- 0.3) x 1O (exp-6) micro K(exp 2).

  12. THE ATACAMA COSMOLOGY TELESCOPE: EXTRAGALACTIC SOURCES AT 148 GHz IN THE 2008 SURVEY

    SciTech Connect

    Marriage, Tobias A.; Lin Yenting; Das, Sudeep; Juin, Jean Baptiste; Aguirre, Paula; Barrientos, L. Felipe; Marsden, Danica; Devlin, Mark J.; Dicker, Simon R.; Nolta, Michael R.; Bond, John R.; Partridge, Bruce; Ade, Peter A. R.; Amiri, Mandana; Battistelli, Elia S.; Burger, Bryce; Appel, John William; Brown, Ben; Chervenak, Jay

    2011-04-20

    We report on extragalactic sources detected in a 455 deg{sup 2} map of the southern sky made with data at a frequency of 148 GHz from the Atacama Cosmology Telescope (ACT) 2008 observing season. We provide a catalog of 157 sources with flux densities spanning two orders of magnitude: from 15 mJy to 1500 mJy. Comparison to other catalogs shows that 98% of the ACT detections correspond to sources detected at lower radio frequencies. Three of the sources appear to be associated with the brightest cluster galaxies of low-redshift X-ray-selected galaxy clusters. Estimates of the radio to millimeter-wave spectral indices and differential counts of the sources further bolster the hypothesis that they are nearly all radio sources, and that their emission is not dominated by re-emission from warm dust. In a bright (>50 mJy) 148 GHz selected sample with complete cross-identifications from the Australia Telescope 20 GHz survey, we observe an average steepening of the spectra between 5, 20, and 148 GHz with median spectral indices of {alpha}{sub 5-20} = -0.07 {+-} 0.06, {alpha}{sub 20-148} = -0.39 {+-} 0.04, and {alpha}{sub 5-148} = -0.20 {+-} 0.03. When the measured spectral indices are taken into account, the 148 GHz differential source counts are consistent with previous measurements at 30 GHz in the context of a source count model dominated by radio sources. Extrapolating with an appropriately rescaled model for the radio source counts, the Poisson contribution to the spatial power spectrum from synchrotron-dominated sources with flux density less than 20 mJy is C {sup Sync} = (2.8 {+-} 0.3) x 10{sup -6}{mu}K{sup 2}.

  13. The VISTA Deep Extragalactic Observations (VIDEO) survey

    NASA Astrophysics Data System (ADS)

    Jarvis, Matt J.; Bonfield, D. G.; Bruce, V. A.; Geach, J. E.; McAlpine, K.; McLure, R. J.; González-Solares, E.; Irwin, M.; Lewis, J.; Yoldas, A. Kupcu; Andreon, S.; Cross, N. J. G.; Emerson, J. P.; Dalton, G.; Dunlop, J. S.; Hodgkin, S. T.; Le, Fèvre O.; Karouzos, M.; Meisenheimer, K.; Oliver, S.; Rawlings, S.; Simpson, C.; Smail, I.; Smith, D. J. B.; Sullivan, M.; Sutherland, W.; White, S. V.; Zwart, J. T. L.

    2013-01-01

    In this paper, we describe the first data release of the Visible and Infrared Survey Telescope for Astronomy (VISTA) Deep Extragalactic Observations (VIDEO) survey. VIDEO is a ˜12 deg2 survey in the near-infrared Z, Y, J, H and Ks bands, specifically designed to enable the evolution of galaxies and large structures to be traced as a function of both epoch and environment from the present day out to z = 4, and active galactic nuclei (AGNs) and the most massive galaxies up to and into the epoch of reionization. With its depth and area, VIDEO will be able to fully explore the period in the Universe where AGN and starburst activity were at their peak and the first galaxy clusters were beginning to virialize. VIDEO therefore offers a unique data set with which to investigate the interplay between AGN, starbursts and environment, and the role of feedback at a time when it was potentially most crucial. We provide data over the VIDEO-XMM3 tile, which also covers the Canada-France-Hawaii Telescope Legacy Survey Deep-1 field (CFHTLS-D1). The released VIDEO data reach a 5σ AB-magnitude depth of Z = 25.7, Y = 24.5, J = 24.4, H = 24.1 and Ks = 23.8 in 2 arcsec diameter apertures (the full depth of Y = 24.6 will be reached within the full integration time in future releases). The data are compared to previous surveys over this field and we find good astrometric agreement with the Two Micron All Sky Survey, and source counts in agreement with the recently released UltraVISTA survey data. The addition of the VIDEO data to the CFHTLS-D1 optical data increases the accuracy of photometric redshifts and significantly reduces the fraction of catastrophic outliers over the redshift range 0 < z < 1 from 5.8 to 3.1 per cent in the absence of an i-band luminosity prior. However, we expect that the main improvement in photometric redshifts will come in the redshift range 1 < z < 4 due to the sensitivity to the Balmer and 4000 Å breaks provided by the near-infrared VISTA filters. All

  14. The faint galaxy contribution to the diffuse extragalactic background light

    NASA Technical Reports Server (NTRS)

    Cole, Shaun; Treyer, Marie-Agnes; Silk, Joseph

    1992-01-01

    Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.

  15. The case for antiparticles in the extragalactic cosmic radiation

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Wolfendale, A. W.

    1984-01-01

    The presence of an excess of low-energy antiprotons in the primary cosmic radiation has given rise to several possible explanations, some of which involve exotic processes such as mini-black holes and extragalactic antiparticles. The latter possibility is considered, and it is shown that there are interesting implications for the cosmic radiation at higher energies. Indeed, it may be possible to account for a previously puzzling feature of the cosmic ray spectrum (a 'bump' in the range between 10 to the 14th and 10 to the 15th eV) by hypothesizing a primary extragalactic origin for the bulk of the observed cosmic ray antiprotons, although such an explanation is not unique. In this model, most of the cosmic rays above 10 to the 15th eV are extragalactic. A method of testing this hypothesis experimentally is described.

  16. Extragalactic OH megamasers in strong IRAS sources

    NASA Technical Reports Server (NTRS)

    Bottinelli, L.; Dennefeld, H.; Gouguenheim, L.; Martin, J. M.; Paturel, G.; Lesqueren, A. M.

    1987-01-01

    From the OH and HI survey of the strongest far infrared IRAS sources, 3 new powerful OH megamasers were discovered in Arp 143, IRAS 1510+0724 and in the uncatalogued IRAS source, IRAS 17208-0014. The HI line, the OH 1667 and 1665 MHz main lines and the 21 cm continuum observations were made with Nancy radio telescope. The optical spectra and images were obtained at the European Southern Observatory. The spectra are displayed in figures together with the main IR and OH properties of the 8 megamasers detected up to now, including IC 4553, NGC 3690 and Mrk 231, Mrk 273 and III ZW35.

  17. Fast Radio Bursts: The Search for Their Origins

    NASA Astrophysics Data System (ADS)

    Burke Spolaor, Sarah

    2015-08-01

    Fast Radio Bursts (FRBs) are millisecond-duration radio signals whose swept-frequency signals indicate a non-local origin.FRB science has been building rapidly since the first discovery of an FRB in 2007; proof of an FRB population in 2013 (Thornton et al.) was quickly followed by further evidence of their likely, although not yet definite, extragalactic origin (e.g. Kulkarni et al. 2014, Burke-Spolaor & Bannister 2014). Until recently, only circumstantial evidence allowed statements on what progenitors FRBs might arise from, and whether they are local, Galactic, or extragalactic. However, we are now able to detect FRB events in real-time, and have the capability to detect FRBs with radio interferometers. This has opened up the possibility to understand their origins through arcsecond localization and the identification of multi-wavelength counterparts. I will describe what we currently know about FRBs, and the status of the FRB hunt for their enigmatic origins.

  18. The case for antiparticles in the extragalactic cosmic radiation

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Wolfendale, A. W.

    1984-01-01

    The presence of an excess of low energy antiprotons in the primary cosmic radiation has given rise to a number of possible explanations. The possibility that these are extragalactic in origin is considered and it is shown that there are interesting implications for the bulk of the cosmic radiation at higher energies. In particular, it may be possible to account for a previously puzzling feature, a bump in the cosmic ray energy spectrum in the energy range 10(14) to 10(15) eV, with this primary extragalactic origin hypothesis. A method for testing this hypothesis experimentally is also described.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Sources of the Radio Background Considered

    SciTech Connect

    Singal, J.; Stawarz, L.; Lawrence, A.; 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.

  1. Ureilite compaction

    NASA Astrophysics Data System (ADS)

    Walker, D.; Agee, C. B.

    1988-03-01

    Ureilite meteorites show the simple mineralogy and compact recrystallized textures of adcumulate rock or melting residues. A certain amount of controversy exists about whether they are in fact adcumulate rocks or melting residues and about the nature of the precursor liquid or solid assemblage. The authors undertook a limited experimental study which made possible the evaluation of the potential of the thermal migration mechanism (diffusion on a saturation gradient) for forming ureilite-like aggregates from carbonaceous chondrite precursors. They find that the process can produce compact recrystallized aggregates of silicate crystals which do resemble the ureilities and other interstitial-liquid-free adcumulate rocks in texture.

  2. On the extragalactic origin of gamma-ray bursts

    SciTech Connect

    Johnson, M.; Teller, E.

    1984-11-02

    A theory to explain the origin of extragalactic gamma ray bursts is presented. Collisions of black dwarf and neutron stars with a subsequent fragmentation of the dwarf producing relativistic particle accelerations toward the neutron star and a resulting turbulent flow of material at the neutron star surface is postulated. (DWL)

  3. CENTAURUS A: THE EXTRAGALACTIC SOURCE OF COSMIC RAYS WITH ENERGIES ABOVE THE KNEE

    SciTech Connect

    Biermann, Peter L.; De Souza, Vitor E-mail: vitor@ifsc.usp.br

    2012-02-10

    The origin of cosmic rays at all energies is still uncertain. In this paper, we present and explore an astrophysical scenario to produce cosmic rays with energy ranging from below 10{sup 15} to 3 Multiplication-Sign 10{sup 20} eV. We show here that just our Galaxy and the radio galaxy Cen A, each with their own galactic cosmic-ray particles but with those from the radio galaxy pushed up in energy by a relativistic shock in the jet emanating from the active black hole, are sufficient to describe the most recent data in the PeV to near ZeV energy range. Data are available over this entire energy range from the KASCADE, KASCADE-Grande, and Pierre Auger Observatory experiments. The energy spectrum calculated here correctly reproduces the measured spectrum beyond the knee and, contrary to widely held expectations, no other extragalactic source population is required to explain the data even at energies far below the general cutoff expected at 6 Multiplication-Sign 10{sup 19} eV, the Greisen-Zatsepin-Kuz'min turnoff due to interaction with the cosmological microwave background. We present several predictions for the source population, the cosmic-ray composition, and the propagation to Earth which can be tested in the near future.

  4. The Planck Compact Source Catalogues

    NASA Astrophysics Data System (ADS)

    Lopez-Caniego, Marcos

    2015-12-01

    The Second Planck Catalogue of Compact Sources is a catalogue of sources observed over the entire sky at nine different frequencies between 30 and 857 GHz. It consists of Galactic and extragalactic objects detected in the Planck single-frequency full mission total intensity maps. Compact sources detected in the lower frequency channels are assigned to the PCCS2, while at higher frequencies they are assigned to one of two sub·catalogues, the PCCS2 or PCCS2E, depending on their location on the sky. The PCCS2 covers most of the sky and can be used to produce subsamples at higher reliabilities than the target 80% integral reliability of the catalogue. The PCCS2E contains sources located in certain regions where the complex background makes it difficult to quantify the reliability of the detections. Both the PCCS2 and PCCS2E include polarization measurements, in the form of polarized flux densities, or upper limits, and orientation angles for all seven polarization-sensitive Planck channels.

  5. The cosmic population of extended radio sources: A Radio-Optical study

    NASA Astrophysics Data System (ADS)

    Thorat, K.

    2014-03-01

    This thesis presents studies of cosmic populations of extragalactic radio sources. The problems selected for this thesis are 1) the derivation of constraints on the emergence of new sub-mJy populations at flux density below about 1 mJy (at 1.4 GHz) paying careful attention to including sources with low surface brightness and counting sources rather than components 2) development of a new method to estimate the asymmetry in the large scale galaxy environment with respect to the axes of extended radio sources and use this to examine for evidence of impact of the environment on the morphology of radio sources. The studies presented herein have been carried out using the Australia Telescope Low Brightness Survey (ATLBS), which is a sensitive radio survey at 1.4 GHz, imaging 8.42 square degrees of the sky along with accompanying optical observations of the same region.

  6. Exploring Extragalactic Emission: The Hα Dot Survey

    NASA Astrophysics Data System (ADS)

    Rampalli, Rayna; Salzer, John Joseph

    2016-01-01

    The Hα Dot Survey was established as a result of finding point sources of strong line emission in the data obtained for the ALFALFA Hα Survey (Van Sistine et al. 2015). In the latter survey, broad-band R and narrow-band Hα filters were used to examine target galaxies from the ALFALFA blind HI survey (Giovanelli et al. 2005, Haynes et al. 2011). In the process of reducing the ALFALFA Hα Survey data the "Hα Dots" were discovered (Kellar et al. 2008, 2012). Using specialized image analysis tools, a large population of dots has already been detected in the more than 1500 ALFALFA Hα narrow-band images taken with the 0.9m WIYN and 2.1m KPNO telescopes. Follow-up spectra of over 200 Hα Dots discovered from the 0.9m images reveal that these objects are a mix of nearby low-luminosity star-forming galaxies, compact starbursts and Seyfert 2 galaxies at intermediate redshifts, and high-redshift QSOs. Here we present the first list of Hα Dots detected using 2.1m telescope data. The 2.1m images yield a sample of Dots that average almost two magnitudes fainter than those detected with the 0.9m. The current REU project is designed to characterize the set of Hα Dots detected in the deeper 2.1m telescope images, while the broad goals of the Hα Dot Survey include the desire to understand better the chemical evolution of galaxies over cosmic time. This project was supported in part by the NSF REU grant 1358980, by the Maria Mitchell Association (Nantucket, MA), and by the Massachusetts Space Grant Consortium.

  7. Compact accelerator

    DOEpatents

    Caporaso, George J.; Sampayan, Stephen E.; Kirbie, Hugh C.

    2007-02-06

    A compact linear accelerator having at least one strip-shaped Blumlein module which guides a propagating wavefront between first and second ends and controls the output pulse at the second end. Each Blumlein module has first, second, and third planar conductor strips, with a first dielectric strip between the first and second conductor strips, and a second dielectric strip between the second and third conductor strips. Additionally, the compact linear accelerator includes a high voltage power supply connected to charge the second conductor strip to a high potential, and a switch for switching the high potential in the second conductor strip to at least one of the first and third conductor strips so as to initiate a propagating reverse polarity wavefront(s) in the corresponding dielectric strip(s).

  8. Photographic photometry of compact extragalactic objects Optical variability of the quasar 3C 345

    NASA Astrophysics Data System (ADS)

    Babadzhanyants, M. K.; Belokon, E. T.; Denisenko, N. S.; Semenova, E. V.

    1985-08-01

    The results of 11-years photographic observations of optical variability of the quasar 3C 345 are presented. A flare with a timescale of the order of one year, similar to those of 1967 and 1971, was observed in 1982. From a comparison of the obtained series of observations with those of the Rosemary Hill Observatory, a conclusion is drawn on the absence of systematic variability at a timescale of 5 - 20 hours exceeding 0m.2 in magnitude.

  9. Far-infrared photometry of compact extragalactic sources: OJ 187 and BL Lac

    NASA Technical Reports Server (NTRS)

    Harvey, P. M.; Joy, M.; Lester, D. F.; Wilking, B. A.

    1984-01-01

    The 50 and 100 micron emissions of OJ 287 were detected and upper limits for BL Lac were obtained. These first measurements of two BL Lac objects in the far-infrared show them to be similar to the few quasars previously observed in the far-infrared. In particular, there is no evidence for significant dust emission, and the lambda approximately 100 micron flux density fits on a smooth line joining the near-infrared and millimeter continuum fluxes. The implications of the results for models of the sources are discussed briefly.

  10. Photographic photometry of compact extragalactic objects Optical variability of the quasar 3C 345

    SciTech Connect

    Babadzhaniants, M.K.; Belokon, E.T.; Denisenko, N.S.; Semenova, E.V.

    1985-08-01

    An 11-yr (1973-1983) program of photographic observations at the Leningrad Byurakan station is reported, tracing the optical variability of the quasar 3C 345. A roughly 1-yr flare resembling those of 1967 and 1971 occurred in 1982. Comparison with the concurrent observations at Rosemary Hill, Florida, shows no appreciable systematic B-band fluctuations on time scales of 5-20 h. 10 references.

  11. Educational Radio.

    ERIC Educational Resources Information Center

    Arafeh, Sousan

    1999-01-01

    Examines the effectiveness of the radio in education and the crucial role of the radio in distance education in first half of the 20th century; dramatic social changes in the 1960s that led to a review of educational institutions and of educational media; and the radio today as a neglected but inexpensive medium of communication that should be…

  12. Statistical techniques for detecting the intergalactic magnetic field from large samples of extragalactic Faraday rotation data

    SciTech Connect

    Akahori, Takuya; Gaensler, B. M.; Ryu, Dongsu E-mail: bryan.gaensler@sydney.edu.au

    2014-08-01

    Rotation measure (RM) grids of extragalactic radio sources have been widely used for studying cosmic magnetism. However, their potential for exploring the intergalactic magnetic field (IGMF) in filaments of galaxies is unclear, since other Faraday-rotation media such as the radio source itself, intervening galaxies, and the interstellar medium of our Galaxy are all significant contributors. We study statistical techniques for discriminating the Faraday rotation of filaments from other sources of Faraday rotation in future large-scale surveys of radio polarization. We consider a 30° × 30° field of view toward the south Galactic pole, while varying the number of sources detected in both present and future observations. We select sources located at high redshifts and toward which depolarization and optical absorption systems are not observed so as to reduce the RM contributions from the sources and intervening galaxies. It is found that a high-pass filter can satisfactorily reduce the RM contribution from the Galaxy since the angular scale of this component toward high Galactic latitudes would be much larger than that expected for the IGMF. Present observations do not yet provide a sufficient source density to be able to estimate the RM of filaments. However, from the proposed approach with forthcoming surveys, we predict significant residuals of RM that should be ascribable to filaments. The predicted structure of the IGMF down to scales of 0.°1 should be observable with data from the Square Kilometre Array, if we achieve selections of sources toward which sightlines do not contain intervening galaxies and RM errors are less than a few rad m{sup –2}.

  13. Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

    NASA Technical Reports Server (NTRS)

    Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

    2004-01-01

    Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

  14. Elusive Extragalactic Magnetic Fields and their Impact on UHECR propagation

    NASA Astrophysics Data System (ADS)

    Miniati, Francesco; Sigl, Günter

    2005-08-01

    The presence, strength and topology of large scale intergalactic magnetic fields are of crucial importance for the study of Ultra High Energy Cosmic Rays (UHECRs) because they affect their propagation and, therefore, the interpretation of their observational properties. In the following, we present a brief, and by no means exhaustive, summary of the observational properties and origin of large scale magnetic fields and briefly discuss their impact on propagation of UHECRs in the case of a particular simulation model of extragalactic magnetic fields.

  15. Firefighters' Radios

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

  16. Axion-Like particles from extragalactic High Energy sources

    NASA Astrophysics Data System (ADS)

    Conrad, J.; Meyer, M.; Montanino, D.

    2016-05-01

    Background radiation fields (such as Extragalactic Background Light, EBL, or Cosmic Microwave Background, CMB) pervade the Universe. Above a certain energy any gamma ray flux emitted by an extragalactic source should be attenuated by the process γ+ γ(bgk) → e + + e - pair production. We have considered a scenario in which the photons are partly converted into light Axion Like Particles (ALPs) in the local magnetic field of an (extragalactic) source. Then, while the unconverted fraction of photons undergo absorption, the ALP component travel to our galaxy where is converted back to photons by the galactic magnetic field resulting in a sort of cosmic light shining through wall effect. In particular, we have considered two scenarios: 1) conversion in the turbulent magnetic field inside a galaxy cluster; and 2) conversion of photons in the coherent magnetic field at parsec scales in a Blazar jet. Afterwards, we have also analyzed mock data coming from a hypothetical Imaging Air Cherenkov Telescopes (IACT) array with characteristics similar to the Cherenkov Telescope Array (CTA) and we have investigated the dependence of the sensitivity to detect a gamma ray excess on the magnetic field parameters.

  17. A radio view of high-energy emitting AGNs

    NASA Astrophysics Data System (ADS)

    Schulz, Robert Frank

    2016-07-01

    Active galactic nuclei (AGNs) are among the most energetic objects in the Universe. These galaxies that are dominated in part or even throughout the electromagnetic spectrum by emission from their central, compact region. AGNs are extensively studied by multi-wavelength observations. In the standard picture, the main driver of an AGN is a supermassive black hole (SMBH) in its centre that is surrounded by an accretion disk. Perpendicular to the disk, in the vicinity of highly magnetized SMBH relativistic outflows of plasma, so-called jets, can form on either side that can reach far beyond the host galaxy. Only about 10% of all AGNs are dominated by emission from these jets due to relativistic beaming effects and these so-called blazars dominate the extragalactic gamma-ray sky. It is commonly accepted that the low-energy emission (radio to UV/X-ray) is due to synchrotron emission from the jet. The high-energy emission is considered to stem from inverse-Compton scattering of photons on the jet particles, but different sources for these photons are discussed (internal or external to the AGN) and other models for the high-energy emission have also been proposed. The nature of the high-energy emission is strongly linked to the location of the emission region in the jet which requires a detailed understanding of the formation and evolution of jets. Radio observations especially using very long baseline interferometry (VLBI) provide the best way to gain direct information on the intrinsic properties of jets down to sub-pc scales, close to their formation region. In this thesis, I focus on the properties of three different AGNs, IC 310, PKS2004-447, and 3C 111 that belong to the small non-blazar population of gamma-ray-loud AGNs. I study them in detail with a variety of radio astronomical instruments with respect to their high-energy emission and in the context of the large monitoring programmes MOJAVE (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) and

  18. Compact magnetograph

    NASA Technical Reports Server (NTRS)

    Title, A. M.; Gillespie, B. A.; Mosher, J. W.

    1982-01-01

    A compact magnetograph system based on solid Fabry-Perot interferometers as the spectral isolation elements was studied. The theory of operation of several Fabry-Perot systems, the suitability of various magnetic lines, signal levels expected for different modes of operation, and the optimal detector systems were investigated. The requirements that the lack of a polarization modulator placed upon the electronic signal chain was emphasized. The PLZT modulator was chosen as a satisfactory component with both high reliability and elatively low voltage requirements. Thermal control, line centering and velocity offset problems were solved by a Fabry-Perot configuration.

  19. Radio emission evolution of nonstationary sources in the Hedgehog model

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.; Mikhaylutsa, V. P.

    1980-01-01

    Correlations are obtained for numerical calculation of flux F sub v and polarized radiation intensity of a cloud of arbitrary geometry, consisting of ultrarelativistic electrons that dissipate in a radial magnetic field of the nucleus at a random angle to the observer. It is possible that some of the variable extragalactic objects that were previously described by the Shklovskiy model are young formations in the examined model. Radio astronomical observations would permit a determination of their distance, age, and lifetime.

  20. Neutrinos from flat-spectrum radio quasars

    NASA Technical Reports Server (NTRS)

    Mannheim, K.; Stanev, T.; Biermann, P. L.

    1992-01-01

    The GRO observation (Hartman et al., 1992) of a very strong flux of gamma rays with an energy index close to 2 from the distant quasar 3C279 and other extragalactic flat-spectrum radio sources is in very good agreement with models that advocate the important role of very high energy protons and nuclei in the energy transport in AGN. Protons and nuclei cool by interactions on the nonthermal fields in the nuclear jet of the AGN and generate gamma ray and neutrino fluxes. Ultra high energy neutrinos could be observed with sensitive air shower experiments in outbursts as powerful as the one seen by GRO.

  1. Fast radio bursts and white hole signals

    NASA Astrophysics Data System (ADS)

    Barrau, Aurélien; Rovelli, Carlo; Vidotto, Francesca

    2014-12-01

    Quantum gravity effects could make a black hole explode in a time shorter than the Hawking radiation time, via local tunneling through a white hole solution. Here we estimate the size of a primordial black hole exploding today via this process, using a simple generic model. Fast radio bursts, strong signals with millisecond duration, which are probably of extragalactic origin and have an unknown source, have wavelengths not far from the expected size of the exploding hole. We also discuss the high-energy component of the signal. These results suggest a new window for quantum gravity phenomenology.

  2. FANATIC: an SIS radiometer for radio astronomy from 660 to 695 GHz

    NASA Astrophysics Data System (ADS)

    Harris, A. I.; Schuster, K.-F.; Genzel, R.; Plathner, B.; Gundlach, K.-H.

    1994-09-01

    FANATIC is a compact radiometer optimized for radio astronomy from about 660 to 695 GHz (lambda 455 - 432 micron). We observed a large number of molecular and atomic spectral lines from galactic and extragalactic sources during FANATIC's first run on the James Clerk Maxwell Telescope in early March 1994. Double sideband receiver temperatures during observations were about 800 K (25 h nu/k). The heart of the receiver is a two-junction Nb/AlO(x)/Nb SIS array fed by a sandwiched V-antenna. The junction array and antenna are fabricated together at IRAM's Grenoble SIS laboratory. Each junction has a normal resistance of Rn approximately 10 Ohm, an area of approximately 2 sq micron, an individual radial stub circuit to resonate the capacitance, and a lambda/4 transformer to match to the antenna. The solid-state local oscillator is a mm-wave Gunn oscillator followed by a doubler and tripler. The LO diplexer is a Martin-Puplett interferometer, which insures that there is always abundant LO power for operation and speedy tuning. The receiver and telescope coupling optics, LO, dewar, and calibration system fit on an 0.6 x 0.8 m optical breadboard.

  3. FANATIC: An SIS Radiometer for Radio Astronomy in the 660-690 GHz Band

    NASA Astrophysics Data System (ADS)

    Harris, A. I.; Schuster, K.-F.; Gundlach, K.-H.; Plathner, B.

    1994-05-01

    FANATIC is a compact radiometer optimized for radio astronomy from about 660 to 690 GHz (455-435 micron). We observed a large number of molecular and atomic spectral lines from galactic and extragalactic sources during FANATIC's first run on the James Clerk Maxwell Telescope in early March 1994. Double sideband receiver temperatures during observations were about 800 K (25 hv/k). The heart of the receiver is a two-junction Nb/AlOx/Nb SIS array fed by a sandwiched V-Antenna. The junction array and antenna are fabricated together at IRAM's Grenoble SIS laboratory. Each junction has a normal resistance of Rn~10 ohm, an area of ~2 um^2 , an individual radial stub circuit to resonate the capacitance, and a 1/4-wavelength transformer to match to the antenna. The solid-state local oscillator is a mm-wave Gunn oscillator followed by a doubler and tripler. The LO diplexer is a Martin-Puplett interferometer, which insures that there is always abundant LO power for operation and speedy tuning. The receiver and telescope coupling optics, LO, dewar, and calibration system fit on an 0.6 x 0.8 m optical breadboard.

  4. The galactic position dependence of fast radio bursts and the discovery of FRB011025

    SciTech Connect

    Burke-Spolaor, Sarah; Bannister, Keith W.

    2014-09-01

    We report the detection of a dispersed fast radio burst (FRB) in archival intermediate-latitude Parkes Radio Telescope data. The burst appears to be of the same physical origin as the four purported extragalactic FRBs reported by Thornton et al. This burst's arrival time precedes the Thornton et al. bursts by 10 years. We consider that this survey, and many other archival low-latitude (|gb| < 30°) pulsar surveys, have been searched for FRBs but produced fewer detections than the comparatively brief Thornton et al. search. Such a rate dependence on Galactic position could provide critical supporting evidence for an extragalactic origin for FRBs. To test this, we form an analytic expression to account for Galactic position and survey setup in FRB rate predictions. Employing a sky temperature, scattering, and dispersion model of the Milky Way, we compute the expected number of FRBs if they are isotropically distributed on the sky with respect to the Galactic position (i.e., local), and if they are of extragalactic origin. We demonstrate that the relative detection rates reject a local origin with a confidence of 99.96% (∼3.6σ). The extragalactic predictions provide a better agreement; however, there are still strong discrepancies with the low-latitude detection rate at a confidence of 99.69% (∼2.9σ). However, for the extragalactic population, the differences in predicted versus detected population may be accounted for by a number of factors, which we discuss.

  5. Radio wave.

    PubMed

    Elkin, V

    1992-01-01

    In developing countries with high rates of poverty and illiteracy, radio is emerging as an excellent medium for delivering information on health issues, family planning, nutrition, and agricultural development. Since radio does not require wired electricity, it can reach remote rural populations. Surveys have found that between 50-75% of poor rural households in developing countries own radios, and the majority listen to educational radio at least once a week. A program that reaches the urban poor outside of Lima, Peru, has been instrumental in controlling the spread of cholera. A Bolivian station broadcasts 8 hours of literacy, health, agricultural, and cultural programming a day to an audience of more than 2 million Aymara Indians. Small village radio stations with a broadcast range of 15 miles can be established for under US$400 and can generally achieve sustainability through local fundraising events such as raffles. In many cases, listeners have become broadcasters at their local radio stations. PMID:12286181

  6. Rotation Measures of Extragalactic Sources behind the Southern Galactic Plane: New Insights into the Large-Scale Magnetic Field of the Inner Milky Way

    NASA Astrophysics Data System (ADS)

    Brown, J. C.; Haverkorn, M.; Gaensler, B. M.; Taylor, A. R.; Bizunok, N. S.; McClure-Griffiths, N. M.; Dickey, J. M.; Green, A. J.

    2007-07-01

    We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253deg<=l<=356deg, |b|<=1.5deg), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius-Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms. In the best-fitting model, the magnetic field in the fourth Galactic quadrant is directed clockwise in the Sagittarius-Carina spiral arm (as viewed from the north Galactic pole), but is oriented counterclockwise in the Scutum-Crux arm. This contrasts with recent analyses of pulsar RMs alone, in which the fourth-quadrant field was presumed to be directed counterclockwise in the Sagittarius-Carina arm. Also in contrast to recent pulsar RM studies, our joint modeling of pulsar and extragalactic RMs demonstrates that large numbers of large-scale magnetic field reversals are not required to account for observations.

  7. A radio optical reference frame. I - Precise radio source positions determined by Mark III VLBI - Observations from 1979 to 1988 and a tie to the FK5

    NASA Technical Reports Server (NTRS)

    Ma, C.; Shaffer, D. B.; De Vegt, C.; Johnston, K. J.; Russell, J. L.

    1990-01-01

    Observations from 600 Mark III VLBI experiments from 1979 to 1988, resulting in 237,681 acceptable pairs of group delay and phase delay rate observations, have been used to derive positions of 182 extragalactic radio sources with typical formal standard errors less than 1 mas. The sources are distributed fairly evenly above delta = -30 deg, and 70 sources have delta greater than 0 deg. Analysis with different troposphere models, as well as internal and external comparisons, indicates that a coordinate frame defined by this set of radio sources should be reliable at the 1 mas level. The right ascension zero point of this reference frame has been aligned with the FK5 by using the optical positions of 28 extragalactic radio sources whose positions are on the FK5 system. Because of known defects in the knowledge of astronomical constants, daily nutation offsets in longitude and obliquity were determined relative to an arbitrary reference day in the set of experiments.

  8. Radio receivers

    NASA Astrophysics Data System (ADS)

    Bankov, V. N.; Barulin, L. G.; Zhodzishskii, M. I.; Malyshev, I. V.; Petrusinskii, V. V.

    The book is concerned with the design of microelectronic radio receivers and their components based on semiconductor and hybrid integrated circuits. Topics discussed include the hierarchical structure of radio receivers, the synthesis of structural schemes, the design of the principal functional units, and the design of radio receiver systems with digital signal processing. The discussion also covers the integrated circuits of multifunctional amplifiers, analog multipliers, charge-transfer devices, frequency filters, piezoelectronic devices, and microwave amplifiers, filters, and mixers.

  9. VSOP Space VLBI and Geodetic VLBI Investigations of Southern Hemisphere Radio Sources

    NASA Astrophysics Data System (ADS)

    Tingay, S. J.; Reynolds, J. E.; Tzioumis, A. K.; Jauncey, David L.; Lovell, J. E. J.; Dodson, R.; Costa, M. E.; McCulloch, P. M.; Edwards, P. G.; Hirabayashi, H.; Murphy, D. W.; Preston, R. A.; Piner, B. G.; Nicolson, G. D.; Quick, J. F. H.; Kobayashi, H.; Shibata, K. M.

    2002-08-01

    We present images from VLBI Space Observatory Programme (VSOP) observations of 14 compact extragalactic southern hemisphere radio sources, including a description of the observations, the data reduction techniques, and the parameters of the resulting images and model fits. These images provide the highest resolution information to date for many of these objects. Comparisons are made between VSOP and previous ground-based VLBI results, including images from data extracted from the geodetic VLBI archive at the United States Naval Observatory. From the VSOP data, we find that the two radio galaxies observed have lower peak brightness temperatures than the 12 quasars. Also, these data show (1) no evidence for obvious differences between the brightness temperature distributions of gamma-ray-loud and gamma-ray-quiet radio-loud active galactic nuclei and (2) no evidence for obvious correlations between brightness temperature and spectral index, radio polarization, flux density, or month timescale modulation index. These results are consistent with previous work by Lister, Tingay, & Preston, who found that the only observable significantly correlated with VSOP-derived brightness temperature is intraday variability, which is strongly correlated with many relativistic beaming indicators. For one source, PKS 1127-145, we undertake a detailed investigation of the milliarcsecond-scale component positions as a function of time, taking data from the literature and the current work, to estimate proper motions. As a result, we suggest that two components previously reported as stationary, C1 and C2, have apparent transverse speeds of (9.1+/-3.8) and (5.3+/-2.3) h-1c, respectively. We also make the first investigation of the apparent motion in the nearest GHz-peaked spectrum radio galaxy, PKS 1718-649, finding an upper limit on the apparent separation speed of 0.08c. Comparison of geodetic VLBI and VSOP data show no significant detection of component motion in PKS 0208-512, (2

  10. Radio-planetary from tie from Phobos-2 VLBI data

    NASA Technical Reports Server (NTRS)

    Hildebrand, C. E.; Iijima, B. A.; Kroger, P. M.; Folkner, W. M.; Edwards, C. D.

    1994-01-01

    In an ongoing effort to improve the knowledge of the relative orientation (the 'frame tie') of the planetary ephemeris reference frame used in deep navigation and a second reference frame that is defined by the coordinates of a set of extragalactic radio sources, VLBI observations of the Soviet Phobos-2 spacecraft and nearby (in angle) radio sources were obtained at two epochs in 1989, shortly after the spacecraft entered orbit about Mars. The frame tie is an important systematic error source affecting both interplanetary navigation and the process of improving the theory of the Earth's orientation. The data from a single Phobos-2 VLBI session measure one component of the direction vector from Earth to Mars in the frame of the extragalactic radio sources (the 'radio frame'). The radio frame has been shown to be stable and internally consistent with an accuracy of 5 nrad. The planetary ephemeris reference frame has an internal consistency of approximately 15 nrad. The planetary and radio source reference frames were aligned prior to 1989 and measurements of occulations of the radio source 3C273 by the Moon. The Phobos-2 VLBI measurements provide improvement in the accuracy of two of the three angles describing a general rotation between the planetary and radio reference frames. A complete set of measurements is not available because data acquisition was terminated prematurely by loss of spacecraft. The analysis of the two Phobos-2 VLBI data sets indicates that, in the directions of the two rotation components determined by these data, the JPL planetary ephemeris DE200 is aligned with the radio frame as adopted by the International Earth Rotation Service within an accuracy of 20-40 nrad, depending on direction. The limiting errors in the solutions for these offsets are spacecraft trajectory (20 nrad), instrumental biases (19 nrad), and dependence of quasar coordinates on observing frequency (24 nrad).

  11. The new class of FR 0 radio galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, R. D.; Capetti, A.; Giovannini, G.

    2016-02-01

    Are the FRI and FRII radio galaxies representative of the radio-loud (RL) AGN population in the local Universe? Recent studies on the local low-luminosity radio sources cast lights on an emerging population of compact radio galaxies which lack extended radio emission. In a pilot JVLA project, we study the high-resolution images of a small but representative sample of this population. The radio maps reveal compact unresolved or slightly resolved radio structures on a scale of 1-3 kpc. We find that these RL AGN live in red massive early-type galaxies, with large black hole masses (≳ 108 M⊙), and spectroscopically classified as Low Excitation Galaxies, all characteristics typical of FRI radio galaxies which they also share the same nuclear luminosity with. However, they are more core dominated (by a factor of ˜ 30) than FRIs and show a clear deficit of extended radio emission. We call these sources ``FR0'' to emphasize their lack of prominent extended radio emission. A posteriori, other compact radio sources found in the literature fulfill the requirements for a FR0 classification. Hence, the emerging FR0 population appears to be the dominant radio class of the local Universe. Considering their properties we speculate on their possible origins and the possible cosmological scenarios they imply.

  12. Cosmic ray nuclei from extragalactic and galactic pulsars

    NASA Astrophysics Data System (ADS)

    Fang, Ke

    2013-02-01

    In an extragalactic newly-born pulsar, nuclei striped off the star surface can be accelerated to extreme energies and leave the source through dense supernova surroundings. The escaped ultrahigh energy cosmic rays can explain both UHE energy spectral and atmospheric depth observations. In addition, assuming that Galactic pulsars accelerate cosmic rays with the same injection composition, very high energy cosmic rays from local pulsars can meet the flux measurements from above the knee to the ankle, and at the same time, agree with the detected composition trend.

  13. Spectroscopic limits to an extragalactic far-ultraviolet background.

    PubMed

    Martin, C; Hurwitz, M; Bowyer, S

    1991-10-01

    We use a spectrum of the lowest intensity diffuse far-ultraviolet background obtained from a series of observations in a number of celestial view directions to constrain the properties of the extragalactic FUV background. The mean continuum level, IEG = 280 +/- 35 photons cm-2 s-1 angstrom-1 sr-1, was obtained in a direction with very low H I column density, and this represents a firm upper limit to any extragalactic background in the 1400-1900 angstroms band. Previous work has demonstrated that the far-ultraviolet background includes (depending on a view direction) contributions from dust-scattered Galactic light, high-ionization emission lines, two-photon emission from H II, H2 fluorescence, and the integrated light of spiral galaxies. We find no evidence in the spectrum of line or continuum features that would signify additional extragalactic components. Motivated by the observation of steep BJ and U number count distributions, we have made a detailed comparison of galaxy evolution models to optical and UV data. We find that the observations are difficult to reconcile with a dominant contribution from unclustered, starburst galaxies at low redshifts. Our measurement rules out large ionizing fluxes at z = 0, but cannot strongly constrain the QSO background light, which is expected to be 0.5%-4% of IEG. We present improved limits on radiative lifetimes of massive neutrinos. We demonstrated with a simple model that IGM radiation is unlikely to make a significant contribution to IEG. Since dust scattering could produce a significant part of the continuum in this lowest intensity spectrum, we carried out a series of tests to evaluate this possibility. We find that the spectrum of a nearby target with higher NH I, when corrected for H2 fluorescence, is very similar to the spectrum obtained in the low H I view direction. This is evidence that the majority of the continuum observed at low NH I is also dust reflection, indicating either the existence of a hitherto

  14. Space distribution of extragalactic sources - Cosmology versus evolution

    NASA Technical Reports Server (NTRS)

    Cavaliere, A.; Maccacaro, T.

    1990-01-01

    Alternative cosmologies have been recurrently invoked to explain in terms of global spacetime structure the apparent large increase, with increasing redshift, in the average luminosity of active galactic nuclei. These models interestingly seek to avoid the complexities of the canonical interpretation in terms of intrinsic population evolutions in a Friedmann universe. However, a problem of consistency for these cosmologies is pointed out, since they have to include also other classes of extragalactic sources, such as clusters of galaxies and BL Lac objects, for which there is preliminary evidence of a different behavior.

  15. A search for the near-infrared extragalactic background light

    NASA Astrophysics Data System (ADS)

    Matsumoto, T.; Akiba, M.; Murakami, H.

    1988-09-01

    The diffuse celestial light at 1 - 5 μm was observed over a large portion of the sky including the Galactic pole with a rocket-borne infrared telescope cooled by solid nitrogen. After subtracting the foreground components, there still remains an appreciable amount of isotropic diffuse radiation with complex spectral feature. A part of this isotropic radiation may be contaminated by the environmental emission due to rocket engine exhaust; however, the 2.2 μm data is free from contamination and possibly attributed to an extragalactic origin.

  16. A grid of model HII regions for extragalactic studies

    NASA Astrophysics Data System (ADS)

    Stasińska, G.

    1990-06-01

    An extensive grid of model HII regions has been computed with the photoionization code PHOTO. This grid is mainly intended to provide a tool for extragalactic HII regions studies. The abundances vary from twice to 1/100th solar. The ionizing stars effective temperatures reach 55,000 K, and their number varies from 1 to 10,000. Computed line intensities in the infrared, visible and ultraviolet ranges are displayed, together with the mean ionic fractions and the mean electron temperatures for ions of interest.

  17. Cosmological tests and the evolution of extragalactic objects

    NASA Astrophysics Data System (ADS)

    Orlov, V. V.; Raikov, A. A.

    2016-05-01

    The results of several cosmographic tests of the standard ΛCDM model taking into account evolution and a "tired-light" model without evolution are compared. Physical tests and observations of the microwave background are also considered. Arguments supporting each of these models are presented. The general conclusion is that it is not possible to unambiguously identify a preferred cosmological model based on the currently available observational data. The nature of the redshift of spectral lines emitted by extragalactic objects is discussed. Possibilities for further studies are also briefly noted.

  18. A lower-limit flux for the extragalactic background light

    NASA Astrophysics Data System (ADS)

    Kneiske, T. M.; Dole, H.

    2010-06-01

    Context. The extragalactic background light (EBL) contains information about the evolution of galaxies from very early times up to the present. The spectral energy distribution is not known accurately, especially in the near- and mid-infrared range. Upper limits and absolute measurements come from direct observations which might be be polluted by foreground emission, while indirect upper limits can also be set by observations of high energy gamma-ray sources. Galaxy number counts integrations of observable galaxies, missing possible faint sources, give strict lower limits. Aims: A model is constructed, which reproduces the EBL lower limit flux. This model can be used for a guaranteed minimum correction of observed spectra of extragalactic gamma-ray sources for extragalactic absorption. Methods: A forward evolution model for the metagalactic radiation field is used to fit recent observations of satelites like Spitzer, ISO, Hubble and GALEX. The model is applied to calculate the Fazio-Stecker relation, and to compute the absorption factor at different redshifts and corrected blazar spectra. Results: A strict lower-limit flux for the evolving extragalactic background light (and in particular the cosmic infrared background) has been calculated up to a redshift of five. The computed flux is below the existing upper limits from direct observations, and agrees with all existing limits derived from very-high energy gamma-ray observations. The corrected spectra still agree with simple theoretical predictions. The derived strict lower-limit EBL flux is very close to the upper limits from gamma-ray observations. This is true for the present day EBL, but also for the diffuse flux at higher redshift. Conclusions: If future detections of high redshift gamma-ray sources require a lower EBL flux than derived here, the physics assumptions used to derive the upper limits have to be revised. The lower-limit EBL model is not only needed for absorption features in active galactic

  19. Educational Radio.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    This report summarizes information about the history, technology, and operation of educational radio in the U.S. Also presented are the Federal Communications Commission's (FCC) rules and regulations concerning the licensing and channel assignment of educational radio, and its auxiliary special broadcast services. Included are the application…

  20. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Schaffer, R. D.; Gorenstein, M. V.

    1981-01-01

    The activities of the Deep Space Network in support of Radio Astronomy Operations during April and May 1981 are reported. Work in progres in support of an experiment selected for use of the DSN by the Radio Astronomy Experiment Selection Panel, Twin Quasi-Stellar Object VLBI, is reported.

  1. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Taylor, R. M.; Manchester, R. N.

    1980-01-01

    The activities of the Deep Space Network in support of radio and radar astronomy operations during July and August 1980 are reported. A brief update on the OSS-sponsored planetary radio astronomy experiment is provided. Also included are two updates, one each from Spain and Australia on current host country activities.

  2. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Shaffer, R. D.; Wolken, P. R.; Gulkis, S.

    1981-01-01

    The activities of the Deep Space Network in support of radio astronomy operations during the first quarter of 1981 are reported. Results of the use of a low noise maser are presented, as well as updates in DSN support of experiments sanctioned by the Radio Astronomy Experiment Selection Panel.

  3. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Shaffer, R. D.; Wolken, P. R.; Niell, A. E.

    1981-01-01

    The activities of the DSN in support of Radio and Radar Astronomy Operations during September through December 1980 are described. Emphasis is on a report of an experiment selected for use of the DSN by the radio Astronomy Experiment Selection Panel: that of VLBI observations of the energetic galactic object SS-433.

  4. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars. PMID:17836594

  5. College Radio.

    ERIC Educational Resources Information Center

    Sauls, Samuel J.

    As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

  6. Radio Brightness Temperatures and Angular Dimensions of Recently Predicted Vl-Bi Small-Scale Structures

    NASA Astrophysics Data System (ADS)

    Opher, R.

    1990-11-01

    RESUMEN. Muestro que analisis recientes publicados de fuentes de radio galacticas y extragalacticas predicen estructuras en pequera escala en fuentes de radio extendidas, remanentes de supernova, vientos protoestelares, nubes moleculares, distorsiones del fondo de 3 K, enanas blancas magnetizadas, estrellas de tipo tardio y el Sol. Discuto las temperatu- ras de brillo de radio de estas estructuras y sus ditnensiones. Muestro que estas estructuras son detectables con las sensibilidades actuales de VLBI (o en el futuro cercano). ABSTRACT. I show that recently published analysis of galactic and extragalactic radio sources make predictions of small-scale structures in extended radio sources, supernovae remnants, protostellar winds, molecu- lar clouds, distortions of the 3 K background, magnetized white dwarf binaries, late-type stars and the sun. I discuss the radio brightness temperatures of these structures and their dimensions. I show that these structures are detectable with present (or near future) VLBI sensitivities. : RADIO SOURCES-EXTENDED

  7. Force-free equilibria of magnetized jets. [pressure confined extragalactic radio hydromagnetics

    NASA Technical Reports Server (NTRS)

    Koenigl, A.; Choudhuri, A. R.

    1985-01-01

    Force-free equilibrium configurations of magnetic-pressure-dominated magnetized supersonic jets confined by slowly varying external pressure are investigated analytically. For the case where internal dissipation mechanisms are active, the lowest-energy field configuration is found to be the superposition of an axisymmetric mode and a helical mode with a wavelength equal to 5 times the jet radius, and the pressure below which the nonaxisymmetric mode becomes energetically favorable is given as 2700 times the product of the 4th power of the magnetic helicity per unit length and the -6th power of the magnetic flux. A model of the total and polarized emission of such a configuration is developed and applied to the extended well-collimated astronomically resolved jet NGC 6251. The model is shown to reproduce significant features such as transverse oscillations of the ridge line, width oscillations and emission knots, the projected magnetic-field configuration, oscillations of the degree of polarization, and the distribution of the Faraday rotation measure.

  8. DENSITY OF WARM IONIZED GAS NEAR THE GALACTIC CENTER: LOW RADIO FREQUENCY OBSERVATIONS

    SciTech Connect

    Roy, Subhashis

    2013-08-10

    We have observed the Galactic center (GC) region at 0.154 and 0.255 GHz with the Giant Metrewave Radio Telescope. A total of 62 compact likely extragalactic (EG) sources are detected. Their scattering sizes decrease linearly with increasing angular distance from the GC up to about 1 Degree-Sign . The apparent scattering sizes of the sources are more than an order of magnitude less than predicted earlier by the NE2001 model of Galactic electron distribution within 359. Degree-Sign 5 < l < 0. Degree-Sign 5 and -0. Degree-Sign 5 < b < 0. Degree-Sign 5 (Hyperstrong Scattering Region) of the Galaxy. High free-free optical depths ({tau}) are observed toward most of the extended non-thermal sources within 0. Degree-Sign 6 from the GC. Significant variation of {tau} indicates that the absorbing medium is patchy at an angular scale of {approx}10' and n{sub e} is {approx}10 cm{sup -3}, which matches the NE2001 model. This model predicts the EG sources to be resolved out from 1.4 GHz interferometric surveys. However, out of 10 EG sources expected in the region, 8 likely EG are present in the 1.4 GHz catalog. Ionized interfaces of dense molecular clouds to the ambient medium are most likely responsible for strong scattering and low radio frequency absorption. However, dense GC clouds traced by CS J = 1-0 emission are found to have a narrow distribution of {approx}0. Degree-Sign 2 across the Galactic plane. Angular distribution of most EG sources seen through the so-called Hyperstrong Scattering Region are random in b, and typically {approx}7 out of 10 sources will not be seen through the dense molecular clouds, which explains why most of them are not scatter broadened at 1.4 GHz.

  9. The radio properties of infrared-faint radio sources

    NASA Astrophysics Data System (ADS)

    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. Compaction behavior of roller compacted ibuprofen.

    PubMed

    Patel, Sarsvatkumar; Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2008-06-01

    The effect of roller compaction pressure on the bulk compaction of roller compacted ibuprofen was investigated using instrumented rotary tablet press. Three different roller pressures were utilized to prepare granules and Heckel analysis, Walker analysis, compressibility, and tabletability were performed to derive densification, deformation, course of volume reduction and bonding phenomenon of different pressure roller compacted granules. Nominal single granule fracture strength was obtained by micro tensile testing. Heckel analysis indicated that granules prepared using lower pressure during roller compaction showed lower yield strength. The reduction in tabletability was observed for higher pressure roller compacted granules. The reduction in tabletability supports the results of granule size enlargement theory. Apart from the granule size enlargement theory, the available fines and relative fragmentation during compaction is responsible for higher bonding strength and provide larger areas for true particle contact at constant porosity for lower pressure roller compacted granules. Overall bulk compaction parameters indicated that granules prepared by lower roller compaction pressure were advantageous in terms of tabletability and densification. Overall results suggested that densification during roller compaction affects the particle level properties of specific surface area, nominal fracture strength, and compaction behavior. PMID:18280716

  11. Extra-galactic high-energy transients: event rate density and luminosity function

    NASA Astrophysics Data System (ADS)

    Sun, Hui; Zhang, Bing; Li, Zhuo

    2015-08-01

    Several types of extra-galactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (GRBs), short-duration GRBs, supernova shock breakouts (SBOs), and tidal disruption events (TDEs) without or with a relativistic jet. In this paper, we apply a unified method to systematically study the reshift-dependent event rate densities and luminosity functions of these extra-galactic high-energy transients. We consider star formation history as the tracer of the redshift distribution for long GRBs and SBOs. For short GRBs, we consider the compact star merger model to introduce several possible merger delay time distribution models. For TDEs, we consider the mass distribution of supermassive black holes as a function of redshift. We derive some empirical formulae for the redshift-dependent event rate density for different types of transients. Based on the observed events, we derive the local specific event rate density, ρ0,L ∝ dρ0/dL for each type of transient, which represents its luminosity function. All the transients are consistent with having a single power law luminosity function, except the high luminosity long GRBs (HL-lGRBs), whose luminosity function can be well described by a broken power law. The total event rate density for a particular transient depends on the luminosity threshold, and we obtain the following values in units of Gpc-3 yr-1: 2.82^{+0.41}_{-0.36} for HL-lGRBs above 4×1049 erg s-1 218^{+130}_{-86} for low luminosity long GRBs above 6×1046 erg s-1 3.18^{+0.88}_{-0.70}, 2.87^{+0.80}_{-0.64}, and 6.25^{+1.73}_{-1.38} above 5×1049 erg s-1 for short GRBs with three different merger delay models (Gaussian, log-normal, and power law); 2.0^{+2.6}_{-1.3}×104 above 9×1043 erg s-1 for SBOs, 3.0^{+1.0}_{-0.8}×105 for normal TDEs above 1042 erg s-1 and 6.2^{+8.2}_{-4.0} above 3×1047 erg s-1for TDE jets as discovered by Swift. Intriguingly, the global specific event rate densities

  12. The Astronomy Workshop Extragalactic: Web Tools for Use by Students

    NASA Astrophysics Data System (ADS)

    Hayes-Gehrke, Melissa N.; Bolatto, A. D.

    2014-01-01

    The Astronomy Workshop Extragalactic (http://carma.astro.umd.edu/AWE) is a collection of interactive web tools that were developed for use in undergraduate and high school classes and by the general public. The focus of the tools is on concepts encountered in extragalactic astronomy, which are typically quite difficult for students to understand. Current tools explore Olbers' Paradox; the appearance of galaxies in different wavelengths of light; the Doppler Effect; cosmological redshift; gravitational lensing; Hubble's Law; cosmological parameters; and measuring masses of black holes by observing stellar orbits. The tools have been developed by undergraduate students under our supervision and we are planning to continue to add more tools. This project was inspired by the Astronomy Workshop (http://janus.astro.umd.edu) by Doug Hamilton which has web tools exploring more general astronomical concepts. We would like to thank the NSF for support through the CAREER grant NSF-AST0955836, and the Research Corporation for Science Advancement for a Cottrell Scholar award.

  13. The UKIDSS Deep eXtra-Galactic Survey

    NASA Astrophysics Data System (ADS)

    Swinbank, A. M.

    The UKIDSS Deep eXtra-Galactic (DXS) will image an area of 35 sq.deg. at high Galactic latitudes in the J and K-band filters to a depth K = 21.0 (with 5 sq.deg. also imaged in H-band). When completed in 2012, the DXS will have used 118 nights to survey 4 of the best-studied extra-galactic fields: XMM-LSS, the Lockman Hole, SSA22 and ELAIS-N1. The principal goals of the DXS are to identify and measure the abundance of galaxy clusters at 0.8 < z < 1.5; to measure galaxy clustering in well defined samples at z > 1 (and hence measure the evolution of bias, a key test of hierarchical models); and to provide a multi-wavelength census of the luminosity density in star formation and AGN. Here, we describe some of the recent science highlights. Specifically, the discovery of a supercluster at z = 0.9 which spans >30 Mpc and has properties similar to local super-clusters (such as Hercules) and some of the first wide-field (˜3-sq.deg.) clustering measurements in EROs and DRGs.

  14. The Extragalactic Distance Database: All Digital H I Profile Catalog

    NASA Astrophysics Data System (ADS)

    Courtois, Hélène M.; Tully, R. Brent; Fisher, J. Richard; Bonhomme, Nicolas; Zavodny, Maximilian; Barnes, Austin

    2009-12-01

    An important component of the Extragalactic Distance Database is a group of catalogs related to the measurement of H I line profile parameters. One of these is the All Digital H I catalog which contains an amalgam of information from new data and old. The new data result from observations with Arecibo and Parkes Telescopes and with the Green Bank Telescope, including continuing input since the award of the NRAO Cosmic Flows Large Program. The old data have been collected from archives, wherever available, particularly the Cornell University Digital H I Archive, the Nançay Telescope extragalactic H I archive, and the Australia Telescope H I archive. The catalog currently contains information on ~15, 000 profiles relating to ~13, 000 galaxies. The channel-flux per channel files, from whatever source, is carried through a common pipeline. The derived parameter of greatest interest is W m50, the profile width at 50% of the mean flux. After appropriate adjustment, the parameter Wmx is derived, the line width that statistically approximates the peak-to-peak maximum rotation velocity before correction for inclination, 2V maxsini. .

  15. Dust and molecules in extra-galactic planetary nebulae

    NASA Astrophysics Data System (ADS)

    Garcia-Hernandez, Domingo Aníbal

    2015-08-01

    Extra-galactic planetary nebulae (PNe) permit the study of dust and molecules in metallicity environments other than the Galaxy. Their known distances lower the number of free parameters in the observations vs. models comparison, providing strong constraints on the gas-phase and solid-state astrochemistry models. Observations of PNe in the Galaxy and other Local Group galaxies such as the Magellanic Clouds (MC) provide evidence that metallicity affects the production of dust as well as the formation of complex organic molecules and inorganic solid-state compounds in their circumstellar envelopes. In particular, the lower metallicity MC environments seem to be less favorable to dust production and the frequency of carbonaceous dust features and complex fullerene molecules is generally higher with decreasing metallicity. Here, I present an observational review of the dust and molecular content in extra-galactic PNe as compared to their higher metallicity Galactic counterparts. A special attention is given to the level of dust processing and the formation of complex organic molecules (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors) depending on metallicity.

  16. Compact Reactor

    SciTech Connect

    Williams, Pharis E.

    2007-01-30

    Weyl's Gauge Principle of 1929 has been used to establish Weyl's Quantum Principle (WQP) that requires that the Weyl scale factor should be unity. It has been shown that the WQP requires the following: quantum mechanics must be used to determine system states; the electrostatic potential must be non-singular and quantified; interactions between particles with different electric charges (i.e. electron and proton) do not obey Newton's Third Law at sub-nuclear separations, and nuclear particles may be much different than expected using the standard model. The above WQP requirements lead to a potential fusion reactor wherein deuterium nuclei are preferentially fused into helium nuclei. Because the deuterium nuclei are preferentially fused into helium nuclei at temperatures and energies lower than specified by the standard model there is no harmful radiation as a byproduct of this fusion process. Therefore, a reactor using this reaction does not need any shielding to contain such radiation. The energy released from each reaction and the absence of shielding makes the deuterium-plus-deuterium-to-helium (DDH) reactor very compact when compared to other reactors, both fission and fusion types. Moreover, the potential energy output per reactor weight and the absence of harmful radiation makes the DDH reactor an ideal candidate for space power. The logic is summarized by which the WQP requires the above conditions that make the prediction of DDH possible. The details of the DDH reaction will be presented along with the specifics of why the DDH reactor may be made to cause two deuterium nuclei to preferentially fuse to a helium nucleus. The presentation will also indicate the calculations needed to predict the reactor temperature as a function of fuel loading, reactor size, and desired output and will include the progress achieved to date.

  17. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  18. Millijansky radio variability in SDSS stripe 82

    SciTech Connect

    Hodge, J. A.; Becker, R. H.; White, R. L.; Richards, G. T.

    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.

  19. Radio detections of southern ultracool dwarfs

    NASA Astrophysics Data System (ADS)

    Lynch, C.; Murphy, T.; Ravi, V.; Hobbs, G.; Lo, K.; Ward, C.

    2016-04-01

    We report the results of a volume-limited survey using the Australia Telescope Compact Array to search for transient and quiescent radio emission from 15 Southern hemisphere ultracool dwarfs. We detect radio emission from 2MASSW J0004348-404405 increasing the number of radio loud ultracool dwarfs to 22. We also observe radio emission from 2MASS J10481463-3956062 and 2MASSI J0339352-352544, two sources with previous radio detections. The radio emission from the three detected sources shows no variability or flare emission. Modelling this quiescent emission we find that it is consistent with optically thin gyrosynchrotron emission from a magnetosphere with an emitting region radius of (1-2)R*, magnetic field inclination 20°-80°, field strength ˜10-200 G, and power-law electron density ˜104-108 cm-3. Additionally, we place upper limits on four ultracool dwarfs with no previous radio observations. This increases the number of ultracool dwarfs studied at radio frequencies to 222. Analysing general trends of the radio emission for this sample of 15 sources, we find that the radio activity increases for later spectral types and more rapidly rotating objects. Furthermore, comparing the ratio of the radio to X-ray luminosities for these sources, we find 2MASS J10481463-3956062 and 2MASSI J0339352-352544 violate the Güdel-Benz relation by more than two orders of magnitude.

  20. The radio sources CTA 21 and OF+247: The hot spots of radio galaxies

    NASA Astrophysics Data System (ADS)

    Artyukh, V. S.; Tyul'bashev, S. A.; Chernikov, P. A.

    2013-06-01

    The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ˜ 10-1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ˜ 10-3 G, and the density of relativistic electrons is n e ˜ 10-3 cm-3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, < E H > = < E e > ˜ 10-7-10-6 erg cm-3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.

  1. Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Beskin, V. S.; Chernov, S. V.; Gwinn, C. R.; Tchekhovskoy, A. A.

    2015-10-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  2. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Shaffer, R. D.

    1983-01-01

    Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.

  3. The Infrared Database of Extragalactic Observables from Spitzer (IDEOS)

    NASA Astrophysics Data System (ADS)

    Spoon, Henrik

    During the cryogenic phase of the successful Spitzer mission the Infrared Spectrograph (IRS) performed approximately 15,000 observations of galactic and extragalactic sources. Among these are low-resolution spectra of more than 4200 galaxies beyond the Local Group. Results have been published in a great number of papers, led not only by hardcore infrared observers but increasingly also by non-native infrared astronomers. As the PI team of the IRS instrument, we are especially proud of the achievements of the IRS spectrograph, and we feel a special obligation to enhance the legacy value of its many observations. Last Summer we completed the Cornell Atlas of Spitzer-IRS Sources (CASSIS), containing homogeneously, expert-reduced low-resolution IRS spectra for over 11,000 observations. The spectra are available for download from our newly created CASSIS web portal. Here we propose to continue these efforts by fitting the low-resolution extragalactic spectra in the CASSIS atlas and create an Infrared Database of Extragalactic Observables from Spitzer (IDEOS) of homogeneously measured mid-infrared spectroscopic observables of more than 4200 galaxies beyond the Local Group. IDEOS will provide astronomers with widely varying scientific interests access to diagnostics that were previously available only for limited samples, or available on-the- fly only to expert users. The completion of IDEOS will coincide with the completion of ALMA. By their nature, CASSIS galaxies are attractive targets for high S/N ALMA observations. IDEOS will provide easily-accessible mid-IR selection criteria for compilation of ALMA target lists for probing significant questions on the AGN environment, the nature of starburst activity, or the AGN/starburst connection. The virtual observatory accessibility will also greatly automate the collation of synoptic results, particularly in the compilation of SEDs and in the cross-matching of targets for trend plots of spectroscopic observables. IDEOS will

  4. Panchromatic Views of Large-Scale Extragalactic Jets

    SciTech Connect

    Cheung, C.C.; /KIPAC, Menlo Park

    2007-06-01

    Highlights of recent observations of extended jets in AGN are presented. Specifically, we discuss new spectral constraints enabled by Spitzer, studies of the highest-redshift (z{approx}4) radio/X-ray quasar jets, and a new VLBA detection of superluminal motion in the M87 jet associated with a recent dramatic X-ray outburst. Expanding on the title, inverse Compton emission from extended radio lobes is considered and a testable prediction for the gamma-ray emission in one exemplary example is presented. Prospects for future studies with ALMA and low-frequency radio interferometers are briefly described.

  5. Galactic and extragalactic contributions to the astrophysical muon neutrino signal

    NASA Astrophysics Data System (ADS)

    Neronov, Andrii; Semikoz, Dmitry

    2016-06-01

    In a previous study, we have shown that spectral and anisotropy properties of IceCube astrophysical neutrino signals reveal evidence for a sizeable Galactic contribution to the neutrino flux in the Southern Hemisphere. We check if the Galactic contribution is detectable in the astrophysical muon neutrino flux observed from a low positive declinations region of the Northern sky. Estimating the Galactic neutrino flux in this part of the sky from γ -ray and Southern sky neutrino data, we find that the Northern sky astrophysical muon neutrino signal shows an excess over the Galactic flux. This points to the presence of an additional hard spectrum (extragalactic or large-scale Galactic halo) component of the astrophysical neutrino flux. We show that the Galactic flux component should still be detectable in the muon neutrino data in a decade-long IceCube exposure.

  6. THE EXTRAGALACTIC DISTANCE DATABASE: COLOR-MAGNITUDE DIAGRAMS

    SciTech Connect

    Jacobs, Bradley A.; Tully, R. Brent; Rizzi, Luca; Shaya, Edward J.; Makarov, Dmitry I.; Makarova, Lidia

    2009-08-15

    The color-magnitude diagrams/tip of the red giant branch (CMDs/TRGB) section of the Extragalactic Distance Database contains a compilation of observations of nearby galaxies from the Hubble Space Telescope. Approximately 250 (and increasing) galaxies in the Local Volume have CMDs and the stellar photometry tables used to produce them available through the Web. Various stellar populations that make up a galaxy are visible in the CMDs, but our primary purpose for collecting and analyzing these galaxy images is to measure the TRGB in each. We can estimate the distance to a galaxy by using stars at the TRGB as standard candles. In this paper, we describe the process of constructing the CMDs and make the results available to the public.

  7. Extragalactic plus Galactic Model for IceCube Neutrino Events

    NASA Astrophysics Data System (ADS)

    Palladino, Andrea; Vissani, Francesco

    2016-08-01

    The hypothesis that high-energy cosmic neutrinos are power law distributed is critically analyzed. We propose a model with two components that better explains the observations. The extragalactic component of the high-energy neutrino flux has a canonical {E}ν -2 spectrum while the galactic component has a {E}ν -2.7 spectrum; both of them are significant. This model has several implications, which can be tested by IceCube and ANTARES over the next several years. Moreover, the existence of a diffuse component, close to the Galactic plane and that yields (20–30)% of IceCube’s events, is interesting for the future km3 neutrino telescopes located in the Northern Hemisphere and for gamma-ray telescopes aiming to measure events up to a few 100 TeV from the southern sky.

  8. Evolution of the luminosity function of extragalactic objects

    NASA Technical Reports Server (NTRS)

    Petrosian, V.

    1985-01-01

    A nonparametric procedure for determination of the evolution of the luminosity function of extragalactic objects and use of this for prediction of expected redshift and luminosity distribution of objects is described. The relation between this statistical evolution of the population and their physical evolution, such as the variation with cosmological epoch of their luminosity and formation rate is presented. This procedure when applied to a sample of optically selected quasars with redshifts less than two shows that the luminosity function evolves more strongly for higher luminosities, indicating a larger quasar activity at earlier epochs and a more rapid evolution of the objects during their higher luminosity phases. It is also shown that absence of many quasars at redshifts greater than three implies slowing down of this evolution in the conventional cosmological models, perhaps indicating that this is near the epoch of the birth of the quasar (and galaxies).

  9. On Testing the Equivalence Principle with Extragalactic Bursts

    NASA Astrophysics Data System (ADS)

    Nusser, Adi

    2016-04-01

    An interesting test of Einstein’s equivalence principle (EEP) relies on the observed lag in the arrival times of photons emitted from extragalactic transient sources. Attributing the lag between photons of different energies to the gravitational potential of the Milky Way (MW), several authors derive new constraints on deviations from EEP. It is shown here that potential fluctuations from the large-scale structure are at least two orders of magnitude larger than the gravitational potential of the MW. Combined with the larger distances, for sources at redshift z≳ 0.5 the rms of the contribution from these fluctuations exceeds the MW by more than four orders of magnitude. We provide actual constraints for several objects based on a statistical calculation of the large-scale fluctuations in the standard ΛCDM cosmological model.

  10. A Multi-ionic Kinematic Investigation of NGC 595, a Giant Extragalactic H II Region in M33

    NASA Astrophysics Data System (ADS)

    Lagrois, Dominic; Joncas, Gilles

    2009-08-01

    Spectro-interferometric observations of the Hα, [O III], and [S II] optical emission lines are combined with radio observations of the 21 cm line in order to obtain a reliable kinematic image of NGC 595, the second largest giant extragalactic H II region in M33. The Hα and [O III] observations reveal that the nebula is exposed to two distinct kinematical regimes. While symmetric, broad velocity profiles dominate a sizeable fraction of the ionized extent, evidence for line splitting is detected in a small region near the most massive stars of the star cluster. A quantitative investigation proposes that two expanding wind-blown bubbles could be held responsible for the observed line splitting. The kinematics of the ionized material presenting one-component velocity profiles likely indicates that Champagne flows are present at the periphery of the molecular component leading to accelerated ionized material in the ambient interstellar medium. In areas not dominated by the photoionization of the molecular clouds, the H+ and S+ material shows a kinematical behavior roughly in agreement with the atomic gas. Mean nonthermal line widths show relatively large, supersonic values especially in [O III]. Models of structure functions indicate that the Hα and [O III] components could be exposed to different turbulent motions which could explain the broadening excess observed for the latter ion. On the full ionized extent of the nebula, the S+ material shows narrower line widths than the two other ions. Combined with the absence of line splitting, these peculiar characteristics indicate that the [S II] component is likely located at the periphery of the nebula and probably does not coexist with Hα and [O III]. The shape of the [S II] structure function is in agreement with a relatively low number of large-scale velocity gradients which partially explains the narrower profiles observed. The mean electron density in the nebula is estimated at 162 ± 106(1σ) cm-3, in agreement

  11. FLUX AND PHOTON SPECTRAL INDEX DISTRIBUTIONS OF FERMI-LAT BLAZARS AND CONTRIBUTION TO THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

    SciTech Connect

    Singal, J.; Petrosian, V.; Ajello, M.

    2012-07-01

    We present a determination of the distributions of the photon spectral index and gamma-ray flux-the so-called log N-log S relation-for the 352 blazars detected with a greater than approximately 7{sigma} detection threshold and located above {+-}20 Degree-Sign Galactic latitude by the Large Area Telescope of the Fermi Gamma-ray Space Telescope in its first year catalog. Because the flux detection threshold depends on the photon index, the observed raw distributions do not provide the true log N-log S counts or the true distribution of the photon index. We use the non-parametric methods developed by Efron and Petrosian to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the two variables. We demonstrate the robustness of our procedures using a simulated data set of blazars and then apply these to the real data and find that for the population as a whole the intrinsic flux distribution can be represented by a broken power law with high and low indices of -2.37 {+-} 0.13 and -1.70 {+-} 0.26, respectively, and the intrinsic photon index distribution can be represented by a Gaussian with mean of 2.41 {+-} 0.13 and width of 0.25 {+-} 0.03. We also find the intrinsic distributions for the sub-populations of BL Lac and flat spectrum radio quasar type blazars separately. We then calculate the contribution of Fermi blazars to the diffuse extragalactic gamma-ray background radiation. Under the assumption that the flux distribution of blazars continues to arbitrarily low fluxes, we calculate the best-fit contribution of all blazars to the total extragalactic gamma-ray output to be 60%, with a large uncertainty.

  12. Radio emission from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, Gloria; Giacani, Elsa

    2015-09-01

    The explosion of a supernova releases almost instantaneously about 10^{51} ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from an SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critically discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analysis of the prospects for future research with the latest-generation radio telescopes.

  13. Isotropic diffuse and extragalactic γ-ray background: emission from extragalactic sources vs dark matter annihilating particles

    NASA Astrophysics Data System (ADS)

    Di Mauro, Mattia; Fermi-LAT Collaboration

    2016-05-01

    The isotropic diffuse γ-ray background (IGRB) has been detected by various experiments and recently the Fermi-LAT Collaboration has precisely measured its spectrum in a wide energy range. The origin of the IGRB is still unclear and we show in this paper the significative improvements that have been done, thanks to the new Fermi-LAT catalogs, to solve this mystery. We demonstrate that the γ-ray intensity and spectrum of the IGRB is fully consistent with the unresolved emission from extragalactic point sources, namely Active Galactic Nuclei and Star Forming Galaxies. We show also that the IGRB can be employed to derive sever constraints for the γ-ray emission from diffuse processes such as annihilation of Dark Matter (DM) particles. Our method is able to provide low bounds for the thermal annihilation cross section for a wide range of DM masses.

  14. The Extragalactic Background Light Absorption Feature in the Blazar Component of the Extragalactic Gamma-ray Background

    NASA Astrophysics Data System (ADS)

    Venters, Tonia M.; Pavlidou, Vasiliki; Reyes, Luis C.

    2009-10-01

    High-energy photons from cosmological emitters suffer attenuation due to pair production interactions with the extragalactic background light (EBL). The collective emission of any high-energy emitting cosmological population will exhibit an absorption feature at the highest energies. We calculate this absorption feature in the collective emission of blazars for various models of the blazar gamma-ray luminosity function (GLF) and the EBL. We find that models of the blazar GLF that predict higher relative contributions of high-redshift blazars to the blazar collective spectrum result in emission that is more susceptible to attenuation by the EBL, and hence result in more prominent absorption features, allowing for better differentiation amongst EBL models. We thus demonstrate that observations of such an absorption feature will contain information regarding both the blazar GLF and the EBL, and we discuss tests for EBL models and the blazar GLF that will become possible with upcoming Fermi observations.

  15. Search for gamma-rays from M31 and other extragalactic objects

    NASA Technical Reports Server (NTRS)

    Cawley, M. F.; Fegan, D. J.; Gibbs, K.; Liebing, D. F.; Stenger, V. J.; Gorham, P. W.; Lamb, R. C.; Porter, N. A.; Weeles, T. C.

    1985-01-01

    Although the existence of fluxes of gamma-rays of energies 10 to the 12th power eV is now established for galactic sources, the detection of such gamma-rays from extragalactic sources has yet to be independently confirmed in any case. The detection and confirmation of such energetic photons is of great astrophysical importance in the study of production mechanisms for cosmic rays, and other high energy processes in extragalactic objects. Observations of m31 are discussed. It is reported as a 10 to the 12th power eV gamma-ray source. Flux limits on a number of other extragalactic objects chosen for study are given.

  16. Forbidden O II studies of galactic planetary nebulae and extragalactic H II complexes

    NASA Astrophysics Data System (ADS)

    Odell, C. R.; Castaneda, H. O.

    1984-08-01

    The 3727-A doublet ratio of forbidden O II was observed in five planetary nebulae and nine extragalactic groupings of H II regions (H II Complexes). The theoretical relation between this doublet ratio and nebular density was rederived using the most up-to-date atomic parameters, permitting columnar densities to be determined for all objects. The structure of extragalactic H II Complexes is discussed, and a preferred model advanced. A new method of distance determination for extragalactic systems is proposed and evaluated in the context of the presently available data.

  17. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Kellermann, Kenneth I.; Heeschen, David; Backer, Donald C.; Cohen, Marshall H.; Davis, Michael; Depater, Imke; Deyoung, David; Dulk, George A.; Fisher, J. R.; Goss, W. Miller

    1991-01-01

    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations.

  18. Planck 2013 results. XXVIII. The Planck Catalogue of Compact Sources

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Argüeso, F.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Battaner, E.; Beelen, A.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Carvalho, P.; Catalano, A.; Challinor, A.; Chamballu, A.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clemens, M.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Negrello, M.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; O'Dwyer, I. J.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Pearson, T. J.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Türler, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Varis, J.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Walter, B.; Wandelt, B. D.; Yvon, D.; Zacchei, A.; Zonca, A.

    2014-11-01

    The Planck Catalogue of Compact Sources (PCCS) is the catalogue of sources detected in the first 15 months of Planck operations, the “nominal” mission. It consists of nine single-frequency catalogues of compact sources, both Galactic and extragalactic, detected over the entire sky. The PCCS covers the frequency range 30-857 GHz with higher sensitivity (it is 90% complete at 180 mJy in the best channel) and better angular resolution (from 32.88' to 4.33') than previous all-sky surveys in this frequency band. By construction its reliability is >80% and more than 65% of the sources have been detected in at least two contiguous Planck channels. In this paper we present the construction and validation of the PCCS, its contents and its statistical characterization.

  19. Kinetic Alfven Waves and the Depletion of the Thermal Population in Extragalactic Jets

    NASA Astrophysics Data System (ADS)

    Jafelice, L. C.; Opher, R.

    1990-11-01

    RESUMEN. Chorros Extragalacticos (CE) y Fuentes Radio Extendidas (FRE) son locales de ricos y complejos procesos de plasma magnetizado. Recien tes observaciones indican que esas fuentes son estructuradas en filamen tos. Nos concentramos aqui en el analisis de dos problemas: 1) el prob[e ma de injecci6n,queespropuesto porlas teorias de aceleraci6n de p ? las en plasmas de CE e FRE, que necesitan partfculas que ya tengan ener gfas moderadamente relativisticas para que los procesos de Fermi sean efectivos; y 2) la reciente evidencia observacional de la ausencia de partfculas termicas en CE. El presente modelo pone en evidencia que ambos problemas estan 1ntimamente relacionados uno con el otro. Jafelice y Opher (1987a) (Astrophys. Space Sci. 137, 303) muestram que es espera da una abundante generaci6n de olas Alf cineticas (OAC) en CE y FRE. En el presente trabajo estudiamos Ia cadena de procesos: a) OAC aceleran electrons termicos al largo del campo magnetico de fondo producien- do electrones supratermicos fugitivos; b) que generan olas Langmuir; y c) las cuales por su vez aceleran una fraccion de los electrones fugi- tivos hasta energias moderadamente relativfsticas. Mostramos que supo - niendo que no haya otra fuente de poblaci6n termica a no ser la , la secuencia de procesos arriba puede encargarse delconsumo de los elec- trones termicos en una escala de tiempo %< que el tiempo de vida de la fuente. ABSTRACT: Extragalactic Jets (EJ) and Extended Radio Sources (ERS) are sites of rich and complex magnetized plasma processes.Recent observa - tions indicate that these sources are filamentary structured. We concentrate here on the analysis of two problems:i) the injection problem, faced by theories of particle acceleration in EJ and ERS plasmas, which need particles with already moderately relativistic energies for the Fer mi processes `to be effective; and 2) the recent observational evidence of the abscence of thermal particles within EJ. The present model makes

  20. Scientific instrumentation of the Radio-Astronomy-Explorer-2 satellite

    NASA Technical Reports Server (NTRS)

    Alexander, J. K.; Kaiser, M. L.; Novaco, J. C.; Grena, F. R.; Weber, R. R.

    1975-01-01

    The instrumentation of the RAE-2 spacecraft is described. The instruments include a pair of long travelling-wave antennas, a 37-m dipole, two radiometers making one frequency scan every 144 sec, and two rapid-sampling total-power burst receivers which cover the range from 0.025 to 13.1 MHz in 32 discrete steps. Effects of terrestrial noise on RAE-1 and RAE-2 observations are discussed, and it is noted that RAE-2 is uniquely capable of observing repeated lunar occultations of strong radio sources at very low frequencies. Some observational programs are briefly noted, including observations of the galactic background distribution, measurements of lunar occultations of solar radio bursts, and searches for more radio sources among the planets, galactic objects, and extragalactic sources.

  1. Fermi gamma-ray imaging of a radio galaxy.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Davis, D S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Finke, J; Focke, W B; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Georganopoulos, M; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F-W; Sambruna, R; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stawarz, Ł; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wallace, E; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M; Hardcastle, M J; Kazanas, D

    2010-05-01

    The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields. PMID:20360067

  2. The γ-ray radiation of the Galaxy and extragalactic sources.

    NASA Astrophysics Data System (ADS)

    Zhong, Jianxia

    1992-06-01

    This paper gives a systematic review on the developing history and present study of γ-ray astronomy, and presents γ-ray sources, as well as the diffuse γ-ray radiation of the Galaxy and extragalactic sources.

  3. IONIZED OUTFLOWS FROM COMPACT STEEP SPECTRUM SOURCES

    SciTech Connect

    Shih, Hsin-Yi; Stockton, Alan; Kewley, Lisa E-mail: stockton@ifa.hawaii.edu

    2013-08-01

    Massive outflows are known to exist, in the form of extended emission-line regions (EELRs), around about one-third of powerful FR II radio sources. We investigate the origin of these EELRs by studying the emission-line regions around compact-steep-spectrum (CSS) radio galaxies that are younger (10{sup 3}-10{sup 5} yr old) versions of the FR II radio galaxies. We have searched for and analyzed the emission-line regions around 11 CSS sources by taking integral field spectra using Gemini Multi-Object Spectrograph on Gemini North. We fit the [O III] {lambda}5007 line and present the velocity maps for each detected emission-line region. We find, in most cases, that the emission-line regions have multi-component velocity structures with different velocity dispersions and/or flux distributions for each component. The velocity gradients of the emission-line gas are mostly well aligned with the radio axis, suggesting a direct causal link between the outflowing gas and the radio jets. The complex velocity structure may be a result of different driving mechanisms related to the onset of the radio jets. We also present the results from the line-ratio diagnostics we used to analyze the ionization mechanism of the extended gas, which supports the scenario where the emission-line regions are ionized by a combination of active galactic nucleus radiation and shock excitation.

  4. Review of Space VLBI RadioAstron studies of AGN

    NASA Astrophysics Data System (ADS)

    Gurvits, Leonid; Kovalev, Yuri

    2016-07-01

    Space VLBI offers an unrivalled resolution in studies of the AGN phenomena. Since 2011, the Russia-led SVLBI mission RadioAstron conducts observations at 92, 18, 6 and 1.3 cm with baselines an order of magnitude longer than the Earth diameter, therefore offering an order of magnitude "sharper" view at the brightest radio sources than achieved with Earth-based VLBI systems. In our presentation we will review the current status of the RadioAstron's scientific programme. Over the first 4.5 years of the in-orbit operations, the mission achieved successful VLBI detections of extragalactic continuum radio sources at all four observing bands. To date, detections on SVLBI baselines have been obtained for more than 150 AGN's at projected baselines up to 350 000 km (about 28 Earth diameters, ED). The highest resolution achieved is 14 microarcscends from 1.3 cm observations. RadioAstron is an international project; it conducts observations with up to 30 Earth-based radio telescopes located on different continents. We will review results of total intensity and polarisation imaging with extreme angular resolution of blazars and nearby active galaxies. We will also discuss typical and maximum brightness temperatures of blazar cores from the AGN Survey obtained with RadioAstron. Physical implications for the AGN jets formation, magnetic field and emission mechanism will be discussed on the basis of the results obtained to date.

  5. 3D-Spectroscopy of Extragalactic Planetary Nebulae as Diagnostic Probes for Galaxy Evolution

    NASA Astrophysics Data System (ADS)

    Kelz, A.; Monreal-Ibero, A.; Roth, M. M.; Sandin, C.; Schönberner, D.; Steffen, M.

    In addition to study extragalactic stellar populations in their integrated light, the detailed analysis of individual resolved objects has become feasible, mainly for luminous giant stars and for extragalactic planetary nebulae (XPNe) in nearby galaxies. A recently started project at the Astrophysical Institute Potsdam (AIP), called ``XPN--Physics'', aims to verify if XPNe are useful probes to measure the chemical abundances of their parent stellar population. The project involves theoretical and observational work packages.

  6. The X-ray log N-log S relation. [background radiation in extragalactic media

    NASA Technical Reports Server (NTRS)

    Boldt, Elihu

    1989-01-01

    Results from various surveys are reviewed as regards X-ray source counts at high galactic latitudes and the luminosity functions determined for extragalactic sources. Constraints on the associated log N-log S relation provided by the extragalactic X-ray background are emphasized in terms of its spatial fluctuations and spectrum as well as absolute flux level. The large number of sources required for this background suggests that there is not a sharp boundary in the redshift distribution of visible matter.

  7. Direct And Reprocessed Gamma-Ray Emission of Kpc-Scale Jets in FR I Radio Galaxies

    SciTech Connect

    Stawarz, L.; Kneiske, T.M.; Kataoka, J.; /Tokyo Inst. Tech. /KIPAC, Menlo Park

    2007-10-09

    We discuss the contribution of kiloparsec-scale jets in FR I radio galaxies to the diffuse {gamma}-ray background radiation. The analyzed {gamma}-ray emission comes from inverse-Compton scattering of starlight photon fields by the ultrarelativistic electrons whose synchrotron radiation is detected from such sources at radio, optical and X-ray energies. We find that these objects, under the minimum-power hypothesis (corresponding to a magnetic field of 300 {micro}G in the brightest knots of these jets), can contribute about one percent to the extragalactic {gamma}-ray background measured by EGRET. We point out that this result already indicates that the magnetic fields in kpc-scale jets of low-power radio galaxies are not likely to be smaller than 10 {micro}G on average, as otherwise the extragalactic {gamma}-ray background would be overproduced.

  8. A model for extremely powerful extragalactic water masers

    SciTech Connect

    Wu, Ying-Cheng; Alcock, C.

    1988-08-01

    The reasons for the differences between extremely powerful extragalatic water masers (EPEWMs) and strong Galactic H/sub 2/O masers are discussed. This model quite successfully explains many important characteristics of EPEWMs; the rapid time variations, the broad range and random velocity distribution, the extremely high luminosities, the various heights or widths of features in spectra, the strong infrared radiation from the galaxies, how an active nucleus contributes to an EPEWM, how some parts of EPEWMs producing strong features are pumped, why this pump mechanism can work, and why EPEWMs are different from strong Galactic H/sub 2/O masers. Recent observations of extragalactic water masers which have extremely high luminosities raise the possibility that the stimulated emission rate in the maser emission line in these regions is much higher than in Galactic masers. It is possible that the local stimulated emission rate exceeds the local bandwidth for the radiation. In this case the standard expression relating the photon emission rate to the profile averaged mean intensity does not apply. A new expression for the photon emission rate is derived.

  9. Gamma ray astrophysics, the extragalactic background light, and new physics

    SciTech Connect

    Serpico, Pasquale D.; /Fermilab

    2008-09-01

    Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. However, recent observations of cosmologically distant emitters by ground based gamma-ray telescopes might be indicative of a higher-than-expected degree of transparency of the universe. One mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility, focusing on photon-ALP conversion in the magnetic fields in and round gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the Galactic Magnetic Field. As case example, we consider the spectrum observed from a HESS source. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

  10. Evolutionary models for giant extragalactic HII regions at different metallicities.

    NASA Astrophysics Data System (ADS)

    Garcia-Vargas, M. L.; Bressan, A.; Diaz, A. I.

    1995-07-01

    We present theoretical evolutionary models for ionizing star clusters and their associated giant HII regions up to an age of 5.4Myr and metallicities between 1/20 and 2.5 times solar. These young clusters can provide the high energy photons needed to keep the regions ionized. We discuss in some detail the Wolf-Rayet and red supergiant phases, sometimes present in the early stages of the evolution of a star cluster. The spectral features characteristic of these stars, when detected and measured on the spectra of giant extragalactic HII regions (GEHR), can be used to constrain the age of the ionizing stellar population. The emergent ionizing continua of the clusters are used as input for the photoionization code CLOUDY to obtain the corresponding emission line spectra in the optical and infrared ranges. The effect of the metallicity is taken into account in the stellar evolution and atmosphere models as well as in the nebular gas producing a consistent set of models. These models can provide estimates of the mass, age and metallicity of the dominant stellar population ionizing a given GEHR solely from the analysis of its optical emission line spectrum.

  11. POLARIZED RADIO SOURCES: A STUDY OF LUMINOSITY, REDSHIFT, AND INFRARED COLORS

    SciTech Connect

    Banfield, Julie K.; George, Samuel J.; Taylor, A. Russ; Stil, Jeroen M.; Kothes, Roland; Scott, Douglas

    2011-05-20

    The Dominion Radio Astrophysical Observatory Deep Field polarization study has been matched with the Spitzer Wide-Area Infrared Extragalactic Survey of the European Large Area Infrared Space Observatory Survey North 1 field. We have used Very Large Array observations with a total intensity rms of 87 {mu}Jy beam{sup -1} to match SWIRE counterparts to the radio sources. Infrared color analysis of our radio sample shows that the majority of polarized sources are elliptical galaxies with an embedded active galactic nucleus. Using available redshift catalogs, we found 429 radio sources of which 69 are polarized with redshifts in the range of 0.04 < z < 3.2. We find no correlation between redshift and percentage polarization for our sample. However, for polarized radio sources, we find a weak correlation between increasing percentage polarization and decreasing luminosity.

  12. Precise optical positions of radio sources in the FK 4-system. II - Results from 28 sources on the northern hemisphere and a preliminary comparison of the optical-radio reference frame

    NASA Astrophysics Data System (ADS)

    de Vegt, C.; Gehlich, U. K.

    1982-09-01

    Precise optical positions of 28 optical counterparts of extragalactic radio sources in the northern hemisphere have been derived using different long focus telescopes. The source positions are referred to the FK 4-system by the AGK 3 RN reference star catalogue as a primary reference frame; a system of secondary reference stars of intermediate brightness mυ = 12-14 has been obtained from the 23-cm astrograph of the Hamburg Observatory. A preliminary comparison of the optical and quasi absolute radio reference frame has been performed using a provisional averaged catalogue of radio positions. Significant systematic differences with local amplitudes up to 0".2 have been found, mainly in declination.

  13. The Radio JOVE Project - Shoestring Radio Astronomy

    NASA Technical Reports Server (NTRS)

    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

  14. Mouse Embryo Compaction.

    PubMed

    White, M D; Bissiere, S; Alvarez, Y D; Plachta, N

    2016-01-01

    Compaction is a critical first morphological event in the preimplantation development of the mammalian embryo. Characterized by the transformation of the embryo from a loose cluster of spherical cells into a tightly packed mass, compaction is a key step in the establishment of the first tissue-like structures of the embryo. Although early investigation of the mechanisms driving compaction implicated changes in cell-cell adhesion, recent work has identified essential roles for cortical tension and a compaction-specific class of filopodia. During the transition from 8 to 16 cells, as the embryo is compacting, it must also make fundamental decisions regarding cell position, polarity, and fate. Understanding how these and other processes are integrated with compaction requires further investigation. Emerging imaging-based techniques that enable quantitative analysis from the level of cell-cell interactions down to the level of individual regulatory molecules will provide a greater understanding of how compaction shapes the early mammalian embryo. PMID:27475854

  15. Core shifts, magnetic fields and magnetization of extragalactic jets

    NASA Astrophysics Data System (ADS)

    Zdziarski, Andrzej A.; Sikora, Marek; Pjanka, Patryk; Tchekhovskoy, Alexander

    2015-07-01

    We study the effect of radio-jet core shift, which is a dependence of the position of the jet radio core on the observational frequency. We derive a new method of measuring the jet magnetic field based on both the value of the shift and the observed radio flux, which complements the standard method that assumes equipartition. Using both methods, we re-analyse the blazar sample of Zamaninasab et al. We find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, ≃0.1-0.2 divided by the bulk Lorentz factor, Γj. Larger values, e.g. 1/Γj, would imply magnetic fields much above equipartition. A small jet opening angle implies in turn the magnetization parameter of ≪1. We determine the jet magnetic flux taking into account this effect. We find that the transverse-averaged jet magnetic flux is fully compatible with the model of jet formation due to black hole (BH) spin-energy extraction and the accretion being a magnetically arrested disc (MAD). We calculate the jet average mass-flow rate corresponding to this model and find it consists of a substantial fraction of the mass accretion rate. This suggests the jet composition with a large fraction of baryons. We also calculate the average jet power, and find it moderately exceeds the accretion power, dot{M} c^2, reflecting BH spin energy extraction. We find our results for radio galaxies at low Eddington ratios are compatible with MADs but require a low radiative efficiency, as predicted by standard accretion models.

  16. Exploring the Progenitors of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Burke-Spolaor, Sarah; Kramer, Michael; Bhat, Ramesh; Kulkarni, S. R.; Keller, Stefan; Champion, David; Flynn, Chris; Kasliwal, Mansi

    2014-10-01

    Fast Radio Bursts (FRBs) are millisecond bursts that are broadly evidenced to arise from extragalactic, but yet unknown, progenitors. They have presented a true mystery in that so far no progenitor theory can adequately account for their observed properties. We request observations that will glean basic information on FRB progenitors. Our observations will execute a specific test of whether FRBs originate in nearby galaxies. We have also designed our target field and time request to enable a thorough exploration of optical counterparts before, during, and after any detected FRB episode. Additionally, with a number depending on the typical distance to FRBs, our observations will raise the running list of total FRB discoveries by 10-60%.

  17. Space Telecommunications Radio System STRS Cognitive Radio

    NASA Technical Reports Server (NTRS)

    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.

  18. Radio continuum polarimetric imaging of high redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Owen, F. N.; Harris, D. E.

    1994-01-01

    Multifrequency images of total and polarized radio continuum emission from the two high redshift radio galaxies 0902+343 (z = 3.40) and 0647+415 (4C 41.17, z = 3.80) are presented. These images represent the most sensitive polarimetric study of high redshift ratio galaxies to date. The emission from both galaxies is substantially polarized, up to 30% in some regions, and both sources sit behind deep 'Faraday screens,' producing large rotation measures, over 10(exp 3) rad/sq. m in magnitude, and large rotation measure gradients across the sources. Such large rotation measures provide further evidence that high redshift radio galaxies are situated in very dense environments. Drawing the analogy to a class of low redshift powerful radio galaxies with similarly large rotation measures, we suggest that 0902+343 and 0647+415 are situated at the centers of dense, x-ray 'colling flow' clusters, and that the cluster gas is substantially magnetized. The remarkable similarity between the optical and radio morphologies of 0647+415 on scales as small as 0.1 sec is presented. We consider, and reject, both synchrotron and inverse Compton radiation as possible sources of the optical emission. We also consider both scattering of light out of a 'cone' of radiation from an obscured nucleus, and jet-induced star formation, and find that both models encounter difficulties in explaining this remarkably close radio-optical alignment. High resolution spectral index images reveal compact, flat spectrum components in both sources. We suggest that these components are the active nuclei of the galaxies. Lastly, high resolution images of 0902+343 show that the southernmost component forms a 'ring' of 0.2 sec radius. We discuss the possibility that this ring is the result of gravitational lensing, along the lines proposed by Kochanek & Lawrence (1990).

  19. PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

    SciTech Connect

    Luan, Jing; Goldreich, Peter

    2014-04-20

    Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10{sup 3} pc cm{sup –3}. Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period.

  20. The infrared properties of the GPS and CSS radio sources

    NASA Astrophysics Data System (ADS)

    O'Dea, C. P.

    2016-02-01

    I review the results of three Spitzer studies of GHz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio galaxies. The luminosity of the IR continuum and the high ionization lines confirm that some GPS/CSS can have central engines which are similar to those of the extended powerful radio sources. This is consistent with the hypothesis that some GPS/CSS can evolve to become the large-scale sources. Warm H_2 is common in the GPS/CSS sources consistent with feedback via jet-ISM interaction. The GPS/CSS seem to have higher star formation rates than typical (2JY + 3CRR) radio sources. This should be confirmed with a larger sample. If compact sources interact with dense, clumpy star forming clouds and if the interaction with the dense medium sufficiently enhances the radio power, these star forming galaxies with enhanced radio emission will be selected for the current bright samples of GPS and CSS sources. This will increase the number of GPS and CSS sources which are observed to be forming stars. If radio sources have longer lives and/or star formation is more common in large radio galaxies, the need for a new population of star forming compact sources with enhanced radio emission is reduced.

  1. Reversible DNA compaction.

    PubMed

    González-Pérez, Alfredo

    2014-01-01

    In this review we summarize and discuss the different methods we can use to achieve reversible DNA compaction in vitro. Reversible DNA compaction is a natural process that occurs in living cells and viruses. As a result these process long sequences of DNA can be concentrated in a small volume (compacted) to be decompacted only when the information carried by the DNA is needed. In the current work we review the main artificial compacting agents looking at their suitability for decompaction. The different approaches used for decompaction are strongly influenced by the nature of the compacting agent that determines the mechanism of compaction. We focus our discussion on two main artificial compacting agents: multivalent cations and cationic surfactants that are the best known compacting agents. The reversibility of the process can be achieved by adding chemicals like divalent cations, alcohols, anionic surfactants, cyclodextrins or by changing the chemical nature of the compacting agents via pH modifications, light induced conformation changes or by redox-reactions. We stress the relevance of electrostatic interactions and self-assembly as a main approach in order to tune up the DNA conformation in order to create an on-off switch allowing a transition between coil and compact states. The recent advances to control DNA conformation in vitro, by means of molecular self-assembly, result in a better understanding of the fundamental aspects involved in the DNA behavior in vivo and serve of invaluable inspiration for the development of potential biomedical applications. PMID:24444152

  2. High flux compact neutron generators

    SciTech Connect

    Reijonen, J.; Lou, T.-P.; Tolmachoff, B.; Leung, K.-N.; Verbeke, J.; Vujic, J.

    2001-06-15

    Compact high flux neutron generators are developed at the Lawrence Berkeley National Laboratory. The neutron production is based on D-D or D-T reaction. The deuterium or tritium ions are produced from plasma using either a 2 MHz or 13.56 MHz radio frequency (RF) discharge. RF-discharge yields high fraction of atomic species in the beam which enables higher neutron output. In the first tube design, the ion beam is formed using a multiple hole accelerator column. The beam is accelerated to energy of 80 keV by means of a three-electrode extraction system. The ion beam then impinges on a titanium target where either the 2.4 MeV D-D or 14 MeV D-T neutrons are generated. The MCNP computation code has predicted a neutron flux of {approximately}10{sup 11} n/s for the D-D reaction at beam intensity of 1.5 A at 150 kV. The neutron flux measurements of this tube design will be presented. Recently new compact high flux tubes are being developed which can be used for various applications. These tubes also utilize RF-discharge for plasma generation. The design of these tubes and the first measurements will be discussed in this presentation.

  3. Extragalactic circuits, transmission lines, and CR particle acceleration

    NASA Astrophysics Data System (ADS)

    Kronberg, Philipp P.; Lovelace, Richard V. E.

    2015-08-01

    A non-negligible fraction of a Supermassive Black Hole's (SMBH) rest mass energy gets transported into extragalactic space by a remarkable process in jets which are incompletely understood. What are the physical processes which transport this energy? It is likely that the energy flows electromagnetically, rather than via a particle beam flux. The deduced electromagnetic fields may produce particles of energy as high as ˜ 1020 eV. The energetics of SMBH accretion disk models and the electromagnetic energy transfer imply that a SMBH should generate a 1018 - 1019 Ampères current close to the black hole and its accretion disk. We describe the so far best observation-based estimate of the magnitude of the current flow along the axis of the jet extending from the nucleus of the active galaxy in 3C303. The current is measured to be I ˜ 1018 Ampères at ˜ 40 kpc away from the AGN. This indicates that organised current flow remains intact over multi-kpc distances. The electric current I transports electromagnetic power into free space, P = I2Z, where Z ˜ 30 Ohms is related to the impedance of free space, and this points to the existence of cosmic electric circuit. The associated electric potential drop, V = IZ, is of the order of that required to generate Ultra High Energy Cosmic Rays (UHECR). We also explore further implications, including disruption/deflection of the power flow and also why such measurements, exemplified by those on 3C303, are currently very difficult to make and to unambiguously interpret. This naturally leads to the topic of how such measurements can be extended and improved in the future. We describe the analogy of electromagnetically dominated jets with transmission lines. High powered jets in vacuo can be understood by approximate analogy with a waveguide. The importance of inductance, impedance, and other laboratory electrical concepts are discussed in this context.

  4. 3-D Relativistic MHD Simulations of Extragalactic Jets

    NASA Astrophysics Data System (ADS)

    Nishikawa, K.-I.; Koide, S.; Sakai, J.-I.; Frank, J.; Christodoulou, D. M.; Sol, H.; Mutel, R. L.

    1997-12-01

    We present the numerical simulations of relativistic jets propagating initially oblique to the field lines of a magnetized ambient medium. Our simulations incorporate relativistic MHD in a four-dimensional spacetime and clearly show that (a) relatively weak, oblique fields (at 1/16 of the equipartition value) have only a negligible influence on the propagating jet and they are passively pushed away by the relativistically moving head; (b) oblique fields in equipartition with the ambient plasma provide more resistance and cause bending at the jet head, but the magnitude of this deflection and the associated backflow are small compared to those identified by previous studies with a 2-D slab model. The new results are understood as follows: Relativistic simulations have consistently shown that these jets are effectively heavy and so they do not suffer substantial momentum losses and are not decelerated as efficiently as their nonrelativistic counterparts. In addition, the ambient magnetic field, however strong, can be pushed aside with relative ease by the beam, provided that the degrees of freedom associated with all three spatial dimensions are followed self-consistently during the simulations. The effect is analogous to pushing Japanese ``noren'' or vertical Venetian blinds out of the way while the slats are allowed to bend in 3-D space rather than as a 2-D slab structure. Applied to relativistic extragalactic jets from blazars, the new results are encouraging since superluminal outflows exhibit bending near their sources and their environments are profoundly magnetized---but observations do not provide support for irregular kinematics such as large-scale vortical motions and pronounced reverse flows near the points of origin.

  5. Silicate features in Galactic and extragalactic post-AGB discs

    NASA Astrophysics Data System (ADS)

    Gielen, C.; Bouwman, J.; van Winckel, H.; Lloyd Evans, T.; Woods, P. M.; Kemper, F.; Marengo, M.; Meixner, M.; Sloan, G. C.; Tielens, A. G. G. M.

    2011-09-01

    Aims: In this paper we study the Spitzer and TIMMI2 infrared spectra of post-AGB disc sources, both in the Galaxy and the LMC. Using the observed infrared spectra we determine the mineralogy and dust parameters of the discs, and look for possible differences between the Galactic and extragalactic sources. Methods: Modelling the full spectral range observed allows us to determine the dust species present in the disc and different physical parameters such as grain sizes, dust abundance ratios, and the dust and continuum temperatures. Results: We find that all the discs are dominated by emission features of crystalline and amorphous silicate dust. Only a few sample sources show features due to CO2 gas or carbonaceous molecules such as PAHs and C60 fullerenes. Our analysis shows that dust grain processing in these discs is strong, resulting in large average grain sizes and a very high crystallinity fraction. However, we do not find any correlations between the derived dust parameters and properties of the central source. There also does not seem to be a noticeable difference between the mineralogy of the Galactic and LMC sources. Even though the observed spectra are very similar to those of protoplanetary discs around young stars, showing similar mineralogy and strong grain processing, we do find evidence for differences in the physical and chemical processes of the dust processing. Based on observations obtained at the European Southern Observatory (ESO), La Silla, observing program 072.D-0263 and 077.D-0555, and on observations made with the Spitzer Space Telescope (program id 3274 and 50092), which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.Appendix A is available in electronic form at http://www.aanda.org

  6. Star Formation History, Dust Attenuation, and Extragalactic Background Light

    NASA Astrophysics Data System (ADS)

    Khaire, Vikram; Srianand, Raghunathan

    2015-05-01

    At any given epoch, the extragalactic background light (EBL) carries imprints of integrated star formation activities in the universe until that epoch. On the other hand, in order to estimate the EBL when direct observations are not possible, one requires an accurate estimation of the star formation rate density (SFRD) and the dust attenuation ({{A}ν }) in galaxies. Here, we present a “progressive fitting method” that determines the global average SFRD(z) and {{A}ν }(z) for any given extinction curve by using the available multiwavelength, multiepoch galaxy luminosity function measurements. Using the available observations, we determine the best-fit combinations of SFRD(z) and {{A}ν }(z), in a simple fitting form, up to z∼ 8 for five well-known extinction curves. We find, irrespective of the extinction curve used, the z at which the SFRD(z) peaks is higher than the z above which {{A}ν }(z) begins to decline. For each case, we compute the EBL from ultraviolet to the far-infrared regime and the optical depth ({{τ }γ }) encountered by the high-energy γ-rays due to pair production upon collisions with these EBL photons. We compare these with measurements of the local EBL, γ-ray horizon, and {{τ }γ } measurements using Fermi-Large Area Telescope. All these and the comparison of independent SFRD(z) and {{A}ν }(z) measurements from the literature with our predictions favor an extinction curve similar to that of the Large Magellanic Cloud Supershell.

  7. A Search for Fast Radio Bursts in GALFACTS data

    NASA Astrophysics Data System (ADS)

    Cohen, Tyler; Salter, Christopher J.; Ghosh, Tapasi

    2016-01-01

    Fast Radio Bursts (FRBs) are transient radio sources whose high dispersion measures suggest they are of extra-galactic origin. They are particularly difficult to detect because, unlike other fast radio transients, they are non-recurring events. At present, 11 such bursts have been detected, 10 by the Parkes Radio Telescope and one by Arecibo Observatory. The G-ALFA Continuum Transit Survey (GALFACTS) is the highest resolution, full-Stokes, radio-continuum survey of the foreground sky. The Arecibo radio telescope is the largest single-aperture telescope in the world, offering the superior point-source sensitivity necessary to detect additional FRBs. GALFACTS utilizes Arecibo's ALFA receiver, an L-band 7-beam feed array, to produce a high-time (1 ms), low-spectral (MHz) resolution (HTLS) data stream between 1225 and 1525 MHz. We used ``Red_Transient", a robust search pipeline developed by A.A. Deshpande, to de-disperse the HTLS data with the intention of detecting FRBs in the ~30% of the total sky surveyed by GALFACTS. Concurrently, the student produced a similar search pipeline to calibrate HTLS data and validate detections by ``Red_Transient". Here, we present the results of initial processing runs on the first several days of GALFACTS observations. Currently, no FRB detections have been found. However, the detection of pulses from the known pulsar J1916+1312 indicates that ``Red_Transient" is capable of detecting fast transient signals present in the data stream.

  8. Synergy with new radio facilities: from LOFAR to SKA

    NASA Astrophysics Data System (ADS)

    Morganti, R.

    2016-06-01

    A number of new radio telescopes are coming on-line paving the way to the Square Kilometre Array. Their new capabilities, e.g. large field of view, broad instantaneous band and fast response, offer new possibilities for the science. I will briefly give an overview of the facilities that are becoming available. Many of them have open time and some are planning large surveys that will be made available to the entire astronomical community, providing an important legacy. I will then focus on some of the results obtained with the Low Frequency Array (LOFAR) on topics where a strong synergy with XMM is (or should be) present. In particular, I will focus on pulsars (e.g. fast switching mode pulsars) and accreting systems among the galactic objects. For the extragalactic objects, the combination radio/X-ray is key for understanding the energetics and, therefore, the impact that radio AGN have on their surroundings. I will in particular focus on results from observations of radio galaxies and clusters. Fast response to transient objects in the radio sky is also receiving a lot of attention with LOFAR (and other radio telescopes).

  9. RADIO ALTIMETERS

    DOEpatents

    Bogle, R.W.

    1960-11-22

    A radio ranging device is described which utilizes a superregenerative oscillator having alternate sending and receiving phases with an intervening ranging interval between said phases, means for varying said ranging interval, means responsive to an on-range noise reduction condition for stopping said means for varying the ranging interval and indicating means coupled to the ranging interval varying means and calibrated in accordance with one-half the product of the ranging interval times the velocity of light whereby the range is indicated.

  10. Millimeter and submillimeter observations of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Knapp, G. R.; Patten, Brian M.

    1991-01-01

    Radio galaxies are often observed to be strong long wavelength infrared sources. Twenty-six radio galaxies with strong compact cores were observed at wavelengths near 1 mm with the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. The detections and upper limits establish the presence of excess infrared emission for almost all of the galaxies in the sample. The exceptions are the BL Lac objects, which have smooth continuous spectra from radio to infrared wavelengths. The spectral energy distributions of the infrared emission from the radio galaxies favor a thermal origin due to emission from cool interstellar dust. The amounts of dust inferred to be present approach those observed in large spirals.

  11. Analysis of the Capability and Limitations of Relativistic Gravity Measurements Using Radio Astronomy Methods

    NASA Technical Reports Server (NTRS)

    Shapiro, I. I.; Counselman, C. C., III

    1975-01-01

    The uses of radar observations of planets and very-long-baseline radio interferometric observations of extragalactic objects to test theories of gravitation are described in detail with special emphasis on sources of error. The accuracy achievable in these tests with data already obtained, can be summarized in terms of: retardation of signal propagation (radar), deflection of radio waves (interferometry), advance of planetary perihelia (radar), gravitational quadrupole moment of sun (radar), and time variation of gravitational constant (radar). The analyses completed to date have yielded no significant disagreement with the predictions of general relativity.

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

    NASA Astrophysics Data System (ADS)

    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).

  13. Inferring the distances of fast radio bursts through associated 21-cm absorption

    NASA Astrophysics Data System (ADS)

    Margalit, Ben; Loeb, Abraham

    2016-07-01

    The distances of fast radio burst (FRB) sources are currently unknown. We show that the 21-cm absorption line of hydrogen can be used to infer the redshifts of FRB sources, and determine whether they are Galactic or extragalactic. We calculate a probability of ˜10 per cent for the host galaxy of an FRB to exhibit a 21-cm absorption feature of equivalent width ≳10 km s-1. Arecibo, along with several future radio observatories, should be capable of detecting such associated 21-cm absorption signals for strong bursts of ≳several Jy peak flux densities.

  14. NEW CONSTRAINTS ON THE GALACTIC HALO MAGNETIC FIELD USING ROTATION MEASURES OF EXTRAGALACTIC SOURCES TOWARD THE OUTER GALAXY

    SciTech Connect

    Mao, S. A.; McClure-Griffiths, N. M.; Gaensler, B. M.; Brown, J. C.; Van Eck, C. L.; Stil, J. M.; Taylor, A. R.; Haverkorn, M.; Kronberg, P. P.; Shukurov, A.

    2012-08-10

    We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100 Degree-Sign -117 Degree-Sign , within 30 Degree-Sign of the Galactic plane. For |b| < 15 Degree-Sign , we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15 Degree-Sign < |b| < 30 Degree-Sign , we find median RMs of -15 {+-} 4 rad m{sup -2} and -62 {+-} 5 rad m{sup -2} in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2 {mu}G (7 {mu}G) at a height 0.8-2 kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.

  15. The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Venters, Tonia M.; Pavlidou, Vasiliki

    2011-01-01

    The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies, We calculate the spectral shapes of the contributions to the EGB arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) assuming blazar spectra can be described as broken power laws, We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

  16. The Real Impact of Extragalactic Jets on Their Environments: Measuring the Advance Speed of Hotspots with HST

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen

    2014-10-01

    We propose moderately deep imaging of two nearby radio galaxies, M87 and Pictor A, in which the terminal shock of the jet as it impacts the IGM (aka 'hotspot') has previously been imaged in the optical with HST. The primary goal of this program is to leverage the 20 year imaging baselines afforded by Hubble archival data and state-of-the-art precision astrometry in order to measure, for the first time, the proper motions of a terminal shock/hotspot. This is the most direct method of constraining the velocity of the working surface, and when combined with existing multi-wavelength data, yields an estimate of the momentum carried by the jet, an important, but difficult-to-measure physical characteristic necessary for understanding the impact of extragalactic jets on their hosts and environments. In addition, the proposed imaging will allow us to study the inner kpc-scale jets of M87 and Pictor A, as well as the counter-jet and counter-hotspot of Pictor A.

  17. Compaction behavior of isomalt after roll compaction.

    PubMed

    Quodbach, Julian; Mosig, Johanna; Kleinebudde, Peter

    2012-01-01

    The suitability of the new isomalt grade galenIQ™ 801 for dry granulation and following tableting is evaluated in this study. Isomalt alone, as well as a blend of equal parts with dibasic calcium phosphate, is roll compacted and tableted. Particle size distribution and flowability of the granules and friability and disintegration time of the tablets are determined. Tensile strength of tablets is related to the specific compaction force during roll compaction and the tableting force. In all cases, the tensile strength increases with raising tableting forces. The specific compaction force has a different influence. For isomalt alone the tensile strength is highest for tablets made from granules prepared at 2 kN/cm and 6 kN/cm and decreases at higher values, i.e., >10 kN/cm. Tensile strength of the blend tablets is almost one third lower compared to the strongest tablets of pure isomalt. Friability of pure isomalt tablets is above the limit. Disintegration time is longest when the tensile strength is at its maximum and decreases with higher porosity and lower tensile strengths. Isomalt proves to be suitable for tableting after roll compaction. Even though the capacity as a binder might not be as high as of other excipients, it is a further alternative for the formulation scientist. PMID:24300366

  18. Compaction Behavior of Isomalt after Roll Compaction

    PubMed Central

    Quodbach, Julian; Mosig, Johanna; Kleinebudde, Peter

    2012-01-01

    The suitability of the new isomalt grade galenIQ™ 801 for dry granulation and following tableting is evaluated in this study. Isomalt alone, as well as a blend of equal parts with dibasic calcium phosphate, is roll compacted and tableted. Particle size distribution and flowability of the granules and friability and disintegration time of the tablets are determined. Tensile strength of tablets is related to the specific compaction force during roll compaction and the tableting force. In all cases, the tensile strength increases with raising tableting forces. The specific compaction force has a different influence. For isomalt alone the tensile strength is highest for tablets made from granules prepared at 2 kN/cm and 6 kN/cm and decreases at higher values, i.e., >10 kN/cm. Tensile strength of the blend tablets is almost one third lower compared to the strongest tablets of pure isomalt. Friability of pure isomalt tablets is above the limit. Disintegration time is longest when the tensile strength is at its maximum and decreases with higher porosity and lower tensile strengths. Isomalt proves to be suitable for tableting after roll compaction. Even though the capacity as a binder might not be as high as of other excipients, it is a further alternative for the formulation scientist. PMID:24300366

  19. Radio Sources Associated with Intermediate X-ray Luminosity Objects in Merging Galaxy Systems

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Ulvestad, J. S.; Oegerle, William R. (Technical Monitor)

    2002-01-01

    We present new, high-resolution 6, 3.6, and 2 cm radio images of a time-ordered sequence of merging galaxy systems. The new data have a resolution of less than 100pc and a sensitivity comparable to a few x Cas A. We detect compact radio sources in all systems, generally embedded in more diffuse radio emission at the longer wavelengths. Several of the compact radio sources are coincident with compact Intermediate-luminosity X-ray Objects (IXOs) in these systems, and many more are within the 3$/sigma$ Chandra position errors for other IXOs. The fraction of radio identifications and the nature of the radio sources changes as a function of merger stage. These data suggest that the IXOs are associated with complexes of supernova remnants, and therefore with star formation that has occurred within the last $/sim$10$circumflex7$ yr, but are not located in HII regions where copious star formation is occurring currently.

  20. Evolution of luminous IRAS galaxies: Radio imaging

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Hutchings, J. B.

    1993-01-01

    In a recent study of IRAS galaxies' optical morphologies, we found that luminous IR sources lie in the IR color-luminosity plane in groups which separate out by optical spectroscopic type and also by degree of tidal disturbance. We found that the most luminous steep-IR-spectrum sources are generally galaxies in the initial stages of a major tidal interaction. Galaxies with active nuclei were generally found to have flatter IR spectra, to cover a range of IR luminosity, and to be in the later stages of a tidal interaction. We proposed a sequence of events by which luminous IR sources evolve: they start as interacting or merging galaxies, some develop active nuclei, and most undergo extensive star-formation in their central regions. Another way to study these objects and their individual evolution is to study their radio morphologies. Radio emission may arise at a detectable level from supernovae in star-forming regions and/or the appearance of an active nucleus can be accompanied by a nuclear radio source (which may develop extended structure). Therefore, the compact radio structure may trace the evolution of the inner regions of IRAS-luminous sources. If the radio sources are triggered by the interactions, we would expect to find the radio morphology related to the optical 'interactivity' of the systems. Here, we explore using the radio emission of IRAS galaxies as a possible tracer of galaxy evolution. We present and discuss observations of the compact radio morphology of 111 luminous IRAS-selected active galaxies covering a wide range of IR and optical properties.

  1. TRACING MOLECULAR GAS MASS IN EXTREME EXTRAGALACTIC ENVIRONMENTS: AN OBSERVATIONAL STUDY

    SciTech Connect

    Zhu Ming; Xilouris, Emmanuel M.; Kuno, Nario; Lisenfeld, Ute E-mail: padeli@astro.uni-bonn.d E-mail: kuno@nro.nao.ac.j

    2009-12-01

    We present a new observational study of the {sup 12}CO(1-0) line emission as an H{sub 2} gas mass tracer under extreme conditions in extragalactic environments. Our approach is to study the full neutral interstellar medium (H{sub 2}, H I, and dust) of two galaxies whose bulk interstellar medium (ISM) resides in environments that mark (and bracket) the excitation extremes of the ISM conditions found in infrared luminous galaxies, the starburst NGC 3310, and the quiescent spiral NGC 157. Our study maintains a robust statistical notion of the so-called X = N(H{sub 2})/I {sub CO} factor (i.e., a large ensemble of clouds is involved) while exploring its dependence on the very different average ISM conditions prevailing within these two systems. These are constrained by fully sampled {sup 12}CO(3-2) and {sup 12}CO(1-0) observations, at a matched beam resolution of half-power beam width approx15'', obtained with the James Clerk Maxwell Telescope (JCMT) on Mauna Kea (Hawaii) and the 45 m telescope of the Nobeyama Radio Observatory in Japan, combined with sensitive 850 mum and 450 mum dust emission and H I interferometric images which allow a complete view of all the neutral ISM components. Complementary {sup 12}CO(2-1) observations were obtained with the JCMT toward the center of the two galaxies. We found an X factor varying by a factor of 5 within the spiral galaxy NGC 157 and about two times lower than the Galactic value in NGC 3310. In addition, the dust emission spectrum in NGC 3310 shows a pronounced submillimeter 'excess'. We tried to fit this excess by a cold dust component but very low temperatures were required (T {sub C} approx 5-11 K) with a correspondingly low gas-to-dust mass ratio of approx5-43. We furthermore show that it is not possible to maintain the large quantities of dust required at these low temperatures in this starburst galaxy. Instead, we conclude that the dust properties need to be different from Galactic dust in order to fit the submillimeter

  2. Keck HIRES Spectroscopy of Extragalactic H II Regions: C and O Abundances from Recombination Lines

    NASA Astrophysics Data System (ADS)

    Esteban, César; Bresolin, Fabio; Peimbert, Manuel; García-Rojas, Jorge; Peimbert, Antonio; Mesa-Delgado, Adal

    2009-07-01

    We present very deep spectrophotometry of 14 bright extragalactic H II regions belonging to spiral, irregular, and blue compact galaxies. The data for 13 objects were taken with the High Resolution Echelle Spectrometer on the Keck I telescope. We have measured C II recombination lines in 10 of the objects and O II recombination lines in eight of them. We have determined electron temperatures from line ratios of several ions, especially those of low ionization potential. We have found a rather tight linear empirical relation between T e([N II]) and T e([O III]). We have found that O II lines give always larger abundances than [O III] lines. Moreover, the difference of both O++ abundance determinations—the so-called abundance discrepancy factor—is very similar in all the objects, with a mean value of 0.26 ± 0.09 dex, independent of the properties of the H II region and of the parent galaxy. Using the observed recombination lines, we have determined the O, C, and C/O radial abundance gradients for three spiral galaxies: M33, M101, and NGC 2403, finding that C abundance gradients are always steeper than those of O, producing negative C/O gradients across the galactic disks. This result is similar to that found in the Milky Way and has important implications for chemical evolution models and the nucleosynthesis of C. Most of 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. Part of the observations were made with the 4.2 m William Herschel Telescope (WHT), operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  3. Radio Jove: Jupiter Radio Astronomy for Citizens

    NASA Astrophysics Data System (ADS)

    Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

    2014-01-01

    Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

  4. Radio tracking system

    NASA Technical Reports Server (NTRS)

    Breidenthal, J. C.; Komarek, T. A.

    1982-01-01

    The principles and techniques of deep space radio tracking are described along with the uses of tracking data in navigation and radio science. Emphasis is placed on the measurement functions of radio tracking.

  5. Star formation history, dust correction, and the extragalactic background light

    NASA Astrophysics Data System (ADS)

    Khaire, Vikram; Srianand, Raghunathan

    2016-01-01

    The intensity of the extragalactic background light (EBL) from X-rays to infrared wavelengths is of a fundamental importance to study the physics of the intergalactic medium and the distant γ-ray sources. At any given epoch, it carries an imprint of the integrated cosmic star formation rate and quasar activity till that epoch. The EBL cannot be observed directly because of its low surface brightness beyond the local universe and one has to rely on the theoretical estimates. To obtain the EBL theoretically, one requires an accurate estimate of the cosmic star formation rate density (SFRD), and the quasar emissivity. The estimates of SFRD are known to be degenerate with the amount of dust correction. To resolve this degeneracy, we present a novel 'progressive fitting method', which uses observed multi-wavelength and multi-epoch galaxy luminosity function measurements and determines a unique combination of the average SFRD(z) and dust attenuation AFUV(z) in the far ultraviolet band (FUV band; central wavelength~1500 Angstrom) for a given extinction curve. Using this method and the available observations, we determine the combinations of SFRD(z) and AFUV(z) up to z~8 for five well known extinction curves. The comparison with the independent SFRD(z), AFUV(z) and local infrared emissivity measurements from the literature with our predictions favor an extinction curve similar to that of Large Magellanic Cloud Supershell (LMC2). We update the quasar emissivity using the recent quasar luminosity function (QLF) measurements which show a factor of ~2 increase as compared to the previous QLFs at z<2. We show, the EBL estimated using this updated quasar emissivity and the SFRD(z) for LMC2 extinction curve resolves the problem of 'photon underproduction crisis' at low redshift. The EBL consistently reproduces the recent measurements of γ-ray horizon and the pair-production optical depths of γ-rays from the Fermi Large Area Telescope. The effect of the updated EBL on the

  6. The reproducible radio outbursts of SS Cygni

    NASA Astrophysics Data System (ADS)

    Russell, T. D.; Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; O'Brien, T. J.; Page, K. L.; Templeton, M. R.; Körding, E. G.; Knigge, C.; Rupen, M. P.; Fender, R. P.; Heinz, S.; Maitra, D.; Markoff, S.; Migliari, S.; Remillard, R. A.; Russell, D. M.; Sarazin, C. L.; Waagen, E. O.

    2016-08-01

    We present the results of our intensive radio observing campaign of the dwarf nova SS Cyg during its 2010 April outburst. We argue that the observed radio emission was produced by synchrotron emission from a transient radio jet. Comparing the radio light curves from previous and subsequent outbursts of this system (including high-resolution observations from outbursts in 2011 and 2012) shows that the typical long and short outbursts of this system exhibit reproducible radio outbursts that do not vary significantly between outbursts, which is consistent with the similarity of the observed optical, ultraviolet and X-ray light curves. Contemporaneous optical and X-ray observations show that the radio emission appears to have been triggered at the same time as the initial X-ray flare, which occurs as disk material first reaches the boundary layer. This raises the possibility that the boundary region may be involved in jet production in accreting white dwarf systems. Our high spatial resolution monitoring shows that the compact jet remained active throughout the outburst with no radio quenching.

  7. The reproducible radio outbursts of SS Cygni

    NASA Astrophysics Data System (ADS)

    Russell, T. D.; Miller-Jones, J. C. A.; Sivakoff, G. R.; Altamirano, D.; O'Brien, T. J.; Page, K. L.; Templeton, M. R.; Körding, E. G.; Knigge, C.; Rupen, M. P.; Fender, R. P.; Heinz, S.; Maitra, D.; Markoff, S.; Migliari, S.; Remillard, R. A.; Russell, D. M.; Sarazin, C. L.; Waagen, E. O.

    2016-08-01

    We present the results of our intensive radio observing campaign of the dwarf nova SS Cyg during its 2010 April outburst. We argue that the observed radio emission was produced by synchrotron emission from a transient radio jet. Comparing the radio light curves from previous and subsequent outbursts of this system (including high-resolution observations from outbursts in 2011 and 2012) shows that the typical long and short outbursts of this system exhibit reproducible radio outbursts that do not vary significantly between outbursts, which is consistent with the similarity of the observed optical, ultraviolet and X-ray light curves. Contemporaneous optical and X-ray observations show that the radio emission appears to have been triggered at the same time as the initial X-ray flare, which occurs as disc material first reaches the boundary layer. This raises the possibility that the boundary region may be involved in jet production in accreting white dwarf systems. Our high spatial resolution monitoring shows that the compact jet remained active throughout the outburst with no radio quenching.

  8. SEYFERT GALAXIES: NUCLEAR RADIO STRUCTURE AND UNIFICATION

    SciTech Connect

    Lal, Dharam V.; Shastri, Prajval; Gabuzda, Denise C.

    2011-04-10

    A radio study of a carefully selected sample of 20 Seyfert galaxies that are matched in orientation-independent parameters, which are measures of intrinsic active galactic nucleus power and host galaxy properties, is presented to test the predictions of the unified scheme hypothesis. Our sample sources have core flux densities greater than 8 mJy at 5 GHz on arcsec scales due to the feasibility requirements. These simultaneous parsec-scale and kiloparsec-scale radio observations reveal (1) that Seyfert 1 and Seyfert 2 galaxies have an equal tendency to show compact radio structures on milliarcsecond scales, (2) the distributions of parsec-scale and kiloparsec-scale radio luminosities are similar for both Seyfert 1 and Seyfert 2 galaxies, (3) there is no evidence for relativistic beaming in Seyfert galaxies, (4) similar distributions of source spectral indices in spite of the fact that Seyferts show nuclear radio flux density variations, and (5) the distributions of the projected linear size for Seyfert 1 and Seyfert 2 galaxies are not significantly different as would be expected in the unified scheme. The latter could be mainly due to a relatively large spread in the intrinsic sizes. We also find that a starburst alone cannot power these radio sources. Finally, an analysis of the kiloparsec-scale radio properties of the CfA Seyfert galaxy sample shows results consistent with the predictions of the unified scheme.

  9. RADIO VARIABILITY IN SEYFERT NUCLEI

    SciTech Connect

    Mundell, C. G.; Ferruit, P.; Nagar, N.; Wilson, A. S.

    2009-09-20

    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 ({approx}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 {approx}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

  10. ACOUSTIC COMPACTION LAYER DETECTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The depth and strength of compacted layers in fields have been determined traditionally using the ASAE standardized cone penetrometer method. However, an on-the-go method would be much faster and much less labor intensive. The soil measurement system described here attempts to locate the compacted...

  11. A very low frequency radio astronomy observatory on the Moon

    NASA Technical Reports Server (NTRS)

    Douglas, James N.; Smith, Harlan J.

    1988-01-01

    Because of terrestrial ionospheric absorption, very little is known of the radio sky beyond 10 m wavelength. An extremely simple, low cost very low frequency radio telescope is proposed, consisting of a large array of short wires laid on the lunar surface, each wire equipped with an amplifier and a digitizer, and connected to a common computer. The telescope could do simultaneous multifrequency observations of much of the visible sky with high resolution in the 10 to 100 m wavelength range, and with lower resolution in the 100 to 1000 m range. It would explore structure and spectra of galactic and extragalactic point sources, objects, and clouds, and would produce detailed quasi-three-dimensional mapping of interstellar matter within several thousand parsecs of the Sun.

  12. MACHO (MAssive Compact Halo Objects) Data

    DOE Data Explorer

    The primary aim of the MACHO Project is to test the hypothesis that a significant fraction of the dark matter in the halo of the Milky Way is made up of objects like brown dwarfs or planets: these objects have come to be known as MACHOs, for MAssive Compact Halo Objects. The signature of these objects is the occasional amplification of the light from extragalactic stars by the gravitational lens effect. The amplification can be large, but events are extremely rare: it is necessary to monitor photometrically several million stars for a period of years in order to obtain a useful detection rate. For this purpose MACHO has a two channel system that employs eight CCDs, mounted on the 50 inch telescope at Mt. Stromlo. The high data rate (several GBytes per night) is accommodated by custom electronics and on-line data reduction. The Project has taken more than 27,000 images with this system since June 1992. Analysis of a subset of these data has yielded databases containing light curves in two colors for 8 million stars in the LMC and 10 million in the bulge of the Milky Way. A search for microlensing has turned up four candidates toward the Large Magellanic Cloud and 45 toward the Galactic Bulge. The web page for data provides links to MACHO Project data portals and various specialized interfaces for viewing or searching the data. (Specialized Interface)

  13. Dynamical compactness and sensitivity

    NASA Astrophysics Data System (ADS)

    Huang, Wen; Khilko, Danylo; Kolyada, Sergiĭ; Zhang, Guohua

    2016-05-01

    To link the Auslander point dynamics property with topological transitivity, in this paper we introduce dynamically compact systems as a new concept of a chaotic dynamical system (X , T) given by a compact metric space X and a continuous surjective self-map T : X → X. Observe that each weakly mixing system is transitive compact, and we show that any transitive compact M-system is weakly mixing. Then we discuss the relationships between it and other several stronger forms of sensitivity. We prove that any transitive compact system is Li-Yorke sensitive and furthermore multi-sensitive if it is not proximal, and that any multi-sensitive system has positive topological sequence entropy. Moreover, we show that multi-sensitivity is equivalent to both thick sensitivity and thickly syndetic sensitivity for M-systems. We also give a quantitative analysis for multi-sensitivity of a dynamical system.

  14. The High Time Resolution Radio Sky

    NASA Astrophysics Data System (ADS)

    Thornton, D.

    2013-11-01

    Pulsars are laboratories for extreme physics unachievable on Earth. As individual sources and possible orbital companions can be used to study magnetospheric, emission, and superfluid physics, general relativistic effects, and stellar and binary evolution. As populations they exhibit a wide range of sub-types, with parameters varying by many orders of magnitude signifying fundamental differences in their evolutionary history and potential uses. There are currently around 2200 known pulsars in the Milky Way, the Magellanic clouds, and globular clusters, most of which have been discovered with radio survey observations. These observations, as well as being suitable for detecting the repeating signals from pulsars, are well suited for identifying other transient astronomical radio bursts that last just a few milliseconds that either singular in nature, or rarely repeating. Prior to the work of this thesis non-repeating radio transients at extragalactic distances had possibly been discovered, however with just one example status a real astronomical sources was in doubt. Finding more of these sources was a vital to proving they were real and to open up the universe for millisecond-duration radio astronomy. The High Time Resolution Universe survey uses the multibeam receiver on the 64-m Parkes radio telescope to search the whole visible sky for pulsars and transients. The temporal and spectral resolution of the receiver and the digital back-end enable the detection of relatively faint, and distant radio sources. From the Parkes telescope a large portion of the Galactic plane can be seen, a rich hunting ground for radio pulsars of all types, while previously poorly surveyed regions away from the Galactic plane are also covered. I have made a number of pulsar discoveries in the survey, including some rare systems. These include PSR J1226-6208, a possible double neutron star system in a remarkably circular orbit, PSR J1431-471 which is being eclipsed by its companion with

  15. Identifying the source of perytons at the Parkes radio telescope

    NASA Astrophysics Data System (ADS)

    Petroff, E.; Keane, E. F.; Barr, E. D.; Reynolds, J. E.; Sarkissian, J.; Edwards, P. G.; Stevens, J.; Brem, C.; Jameson, A.; Burke-Spolaor, S.; Johnston, S.; Bhat, N. D. R.; Kudale, P. Chandra S.; Bhandari, S.

    2015-08-01

    `Perytons' are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion of an astrophysical pulse that has propagated through tenuous cold plasma. In fact, their similarity to FRB 010724 had previously cast a shadow over the interpretation of `fast radio bursts' (FRBs), which otherwise appear to be of extragalactic origin. Until now, the physical origin of the dispersion-mimicking perytons had remained a mystery. We have identified strong out-of-band emission at 2.3-2.5 GHz associated with several peryton events. Subsequent tests revealed that a peryton can be generated at 1.4 GHz when a microwave oven door is opened prematurely and the telescope is at an appropriate relative angle. Radio emission escaping from microwave ovens during the magnetron shut-down phase neatly explains all of the observed properties of the peryton signals. Now that the peryton source has been identified, we furthermore demonstrate that the microwave ovens on site could not have caused FRB 010724. This and other distinct observational differences show that FRBs are excellent candidates for genuine extragalactic transients.

  16. A New Determination of the Extragalactic Diffuse X-Ray Background from EGRET Data

    NASA Technical Reports Server (NTRS)

    Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf

    2004-01-01

    We use the GALPROP model for cosmic-ray propagation to obtain a new estimate of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed EGRET intensities in the energy range 30 MeV - 50 GeV. On this basis we re-evaluate the extragalactic gamma-ray background. We find that for some energies previous work underestimated the Galactic contribution at high latitudes and hence overestimated the background. Our new background spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.

  17. Soviet radio telescopes and solar radio astronomy

    NASA Astrophysics Data System (ADS)

    Alekseev, V. A.; Gel'Freikh, Georgii B.; Zaitsev, Valerii V.; Iliasov, Iurii P.; Kaidanovskii, N. L.

    Soviet radio telescopes of different type and purpose are described, with particular emphasis on very long baseline interferometry. Soviet radio-astronomy studies of solar radio emission and the interplanetary medium are also discussed, with particular attention given to the investigation of the sun's supercorona and the interplanetary plasma.

  18. The Low-frequency Radio Catalog of Flat-spectrum Sources

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    A well known property of the γ-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-γ-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with γ-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified γ-ray sources allowed us to extend the radio-γ-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of γ-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

  19. THE LOW-FREQUENCY RADIO CATALOG OF FLAT-SPECTRUM SOURCES

    SciTech Connect

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

    2014-07-01

    A well known property of the γ-ray sources detected by Cos-B in the 1970s, by the Compton Gamma-Ray Observatory in the 1990s, and recently by the Fermi observations is the presence of radio counterparts, particularly for those associated with extragalactic objects. This observational evidence is the basis of the radio-γ-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with γ-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified γ-ray sources allowed us to extend the radio-γ-ray connection in the MHz regime. We also showed that blazars below 1 GHz maintain flat radio spectra. Thus, on the basis of these new results, we assembled a low-frequency radio catalog of flat-spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey and of the Westerbork in the southern hemisphere catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of γ-ray sources. First, we found NVSS counterparts of Westerbork Synthesis Radio Telescope radio sources, and then we selected flat-spectrum radio sources according to a new spectral criterion, specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28,358 radio sources and their logN-logS distributions. Finally, a comparison with the Green Bank 6 cm radio source catalog was performed to investigate the spectral shape of the low-frequency flat-spectrum radio sources at higher frequencies.

  20. Compaction properties of isomalt.

    PubMed

    Bolhuis, Gerad K; Engelhart, Jeffrey J P; Eissens, Anko C

    2009-08-01

    Although other polyols have been described extensively as filler-binders in direct compaction of tablets, the polyol isomalt is rather unknown as pharmaceutical excipient, in spite of its description in all the main pharmacopoeias. In this paper the compaction properties of different types of ispomalt were studied. The types used were the standard product sieved isomalt, milled isomalt and two types of agglomerated isomalt with a different ratio between 6-O-alpha-d-glucopyranosyl-d-sorbitol (GPS) and 1-O-alpha-d-glucopyranosyl-d-mannitol dihydrate (GPM). Powder flow properties, specific surface area and densities of the different types were investigated. Compactibility was investigated by compression of the tablets on a compaction simulator, simulating the compression on high-speed tabletting machines. Lubricant sensitivity was measured by compressing unlubricated tablets and tablets lubricated with 1% magnesium stearate on an instrumented hydraulic press. Sieved isomalt had excellent flow properties but the compactibility was found to be poor whereas the lubricant sensitivity was high. Milling resulted in both a strong increase in compactibility as an effect of the higher surface area for bonding and a decrease in lubricant sensitivity as an effect of the higher surface area to be coated with magnesium stearate. However, the flow properties of milled isomalt were too bad for use as filler-binder in direct compaction. Just as could be expected, agglomeration of milled isomalt by fluid bed agglomeration improved flowability. The good compaction properties and the low lubricant sensitivity were maintained. This effect is caused by an early fragmentation of the agglomerated material during the compaction process, producing clean, lubricant-free particles and a high surface for bonding. The different GPS/GPM ratios of the agglomerated isomalt types studied had no significant effect on the compaction properties. PMID:19327398

  1. Stabilization of compactible waste

    SciTech Connect

    Franz, E.M.; Heiser, J.H. III; Colombo, P.

    1990-09-01

    This report summarizes the results of series of experiments performed to determine the feasibility of stabilizing compacted or compactible waste with polymers. The need for this work arose from problems encountered at disposal sites attributed to the instability of this waste in disposal. These studies are part of an experimental program conducted at Brookhaven National Laboratory (BNL) investigating methods for the improved solidification/stabilization of DOE low-level wastes. The approach taken in this study was to perform a series of survey type experiments using various polymerization systems to find the most economical and practical method for further in-depth studies. Compactible dry bulk waste was stabilized with two different monomer systems: styrene-trimethylolpropane trimethacrylate (TMPTMA) and polyester-styrene, in laboratory-scale experiments. Stabilization was accomplished by wetting or soaking compactible waste (before or after compaction) with monomers, which were subsequently polymerized. Three stabilization methods are described. One involves the in-situ treatment of compacted waste with monomers in which a vacuum technique is used to introduce the binder into the waste. The second method involves the alternate placement and compaction of waste and binder into a disposal container. In the third method, the waste is treated before compaction by wetting the waste with the binder using a spraying technique. A series of samples stabilized at various binder-to-waste ratios were evaluated through water immersion and compression testing. Full-scale studies were conducted by stabilizing two 55-gallon drums of real compacted waste. The results of this preliminary study indicate that the integrity of compacted waste forms can be readily improved to ensure their long-term durability in disposal environments. 9 refs., 10 figs., 2 tabs.

  2. Extragalactic foreground contamination in temperature-based CMB lens reconstruction

    SciTech Connect

    Osborne, Stephen J.; Hanson, Duncan; Doré, Olivier E-mail: dhanson@physics.mcgill.ca

    2014-03-01

    We discuss the effect of unresolved point source contamination on estimates of the CMB lensing potential, from components such as the thermal Sunyaev-Zel'dovich effect, radio point sources, and the Cosmic Infrared Background. We classify the possible trispectra associated with such source populations, and construct estimators for the amplitude and scale-dependence of several of the major trispectra. We show how to propagate analytical models for these source trispectra to biases for lensing. We also construct a ''source-hardened'' lensing estimator which experiences significantly smaller biases when exposed to unresolved point sources than the standard quadratic lensing estimator. We demonstrate these ideas in practice using the sky simulations of Sehgal et al., for cosmic-variance limited experiments designed to mimic ACT, SPT, and Planck. We find that for radio sources and SZ the bias is significantly reduced, but for CIB it is essentially unchanged. However, by using the high-frequency, all-sky CIB measurements from Planck and Herschel it may be possible to suppress this contribution.

  3. Layered sensing with radio (LSWR)

    NASA Astrophysics Data System (ADS)

    Mitra, Atindra K.

    2010-04-01

    An alternative approach to a Layered Sensing System-of-Systems methodology, denoted as LSWR (Layered Sensing With Radio), is outlined in this paper. This is a novel Broadcast-TV-Driven layered sensing technique that shows potential for finding embedded objects within, for example, buildings via leveraging and combining existing commercial satellite technologies with COTS (Commercial Off-the-Shelf) wireless network technologies and state-of-the-art wireless sensor mote technologies. Specifically, compact sensor mote technologies are employed in a cost-effective manner to interface with and control low-cost satellite radio/broadcast tuners. With this approach, initial concepts of this type are investigated via the analysis of compact custom sensor node technology (i.e. wireless sensor mote interfaced with satellite broadcast tuner) integrated onto a UGV (unmanned ground vehicle) robot arm for purposes developing prototype UGV robot systems with passive integrated RF sensors that support, for example, networked thru-wall embedded object detection. The primary category of commercial satellite signal considered for analysis within this paper is known as DVB (Digital Video Broadcast).

  4. Gravitational Radiation from Compact Binary Pulsars

    NASA Astrophysics Data System (ADS)

    Antoniadis, John

    An outstanding question in modern Physics is whether general relativity (GR) is a complete description of gravity among bodies at macroscopic scales. Currently, the best experiments supporting this hypothesis are based on high-precision timing of radio pulsars. This chapter reviews recent advances in the field with a focus on compact binary millisecond pulsars with white-dwarf (WD) companions. These systems—if modeled properly—provide an unparalleled test ground for physically motivated alternatives to GR that deviate significantly in the strong-field regime. Recent improvements in observational techniques and advances in our understanding of WD interiors have allowed for a series of precise mass measurements is such systems. These masses, combined with high-precision radio timing of the pulsars, result to stringent constraints on the radiative properties of gravity, qualitatively very different from what was available in the past.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. HerMES: disentangling active galactic nuclei and star formation in the radio source population

    NASA Astrophysics Data System (ADS)

    Rawlings, J. I.; Page, M. J.; Symeonidis, M.; Bock, J.; Cooray, A.; Farrah, D.; Guo, K.; Hatziminaoglou, E.; Ibar, E.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Seymour, N.; Vaccari, M.; Wardlow, J. L.

    2015-10-01

    We separate the extragalactic radio source population above ˜50 μJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC (Infrared Array Camera) and Multiband Imaging Photometer for Spitzer (MIPS) and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that radio sources which have likely been selected on their star formation have a high AGN fraction. Below a 1.4 GHz flux density of 1 mJy, along with finding a strong contribution to the source counts from pure star-forming sources, we find that hybrid sources constitute 20-65 per cent of the sources. This result suggests that hybrid sources have a significant contribution, along with sources that do not host a detectable AGN, to the observed flattening of the source counts at ˜1 mJy for the extragalactic radio source population.

  7. The lack of large compact symmetric objects

    NASA Astrophysics Data System (ADS)

    Augusto, P.

    2009-02-01

    In recent years, `baby' (< 103 yr) and `young' (103-105 yr) radio galaxies have been found and classified, although their numbers are still small (tens). Also, they have many different names, depending on the type of survey and scientific context in which they were found: compact steep spectrum sources (CSS), giga-Hertz peaked spectrum sources (GPS) and compact-medium symmetric objects (C-MSO). The latter have the radio galaxy structure more obvious and correspond to the `babies' (CSOs; < 1 kpc) and `young' (MSOs; 1-15 kpc) radio galaxies. The log-size distribution of CSOs shows a sharp drop at 0.3 kpc. This trend continues through flat-spectrum MSOs (over the full 1-15 kpc size range). In order to find out if this lack of large CSOs and flat-spectrum MSOs is due to poor sampling (lack of surveys that probe efficiently the 0.3-15 kpc size range) and/or has physical meaning (e.g. if the lobes of CSOs expand as they grow and age, they might become CSSs, `disappearing' from the flat-spectrum MSO statistics), we have built a sample of 157 flat-spectrum radio sources with structure on ˜0.3-15 kpc scales. We are using new, archived and published data to produce and inspect hundreds of multi-frequency multi-instrument maps and models. We have already found 13 new secure CSO/MSOs. We expect to uncover ˜30-40 new CSOs and MSOs, most on the 0.3-15 kpc size range, when our project is complete.

  8. The Radio Amateur's Handbook.

    ERIC Educational Resources Information Center

    Blakeslee, Douglas, Ed.

    The objectives of this basic reference work for the radio amateur are to present radio theory and practice in terms of application and to reflect both the fundamentals and the rapidly-advancing technology of radio communications so that the radio amateur will have a guide to what is practical, meaningful, proven, and useful. Twenty-three chapters…

  9. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  10. Extragalactic Jets: Some Unanswered Questions and the Prospects for GLAST

    NASA Astrophysics Data System (ADS)

    Blandford, R.

    2008-06-01

    An introduction to AGN jets is presented, paying particular attention to general questions that are currently being addressed or are likely to be addressed using imminent observational capabilities in the gamma ray and radio bands. It is argued that it should become possible to locate the sites of radio and gamma ray emission and to define the jet kinematical structure in a far more prescriptive fashion. Astrophysical arguments should then suffice to affirm (or refute) the common presumptions that synchrotron and inverse Compton emission dominate other processes and that the working substance changes from electromagnetic field to a pair plasma to an ionic plasma as the jet propagates away from the central black hole. Our understanding of jet dynamics can also improve through better characterization of the properties of the surrounding medium which should help decide if magnetic pinching is important and lead to more accurate measurements of jet powers, thrusts, discharges and currents. Combining jet and disk observations should test a ``Central Dogma'', namely that intrinsic AGN behavior is mainly dictated by the mass supply rate in units of the Eddington rate and the spin of the hole in units of its maximum allowed value, with the overall scale of power, variation etc determined by the hole mass. The connection between observed jet properties and the physical processes occurring around black holes is likely to remain conjectural for a while, though relevant numerical simulations are improving rapidly. Finally, the environmental impact of jets should become much clearer along with the role of AGN in the co-evolution of their host galaxies.

  11. Dark Matter and Extragalactic Gas Clouds in the NGC 4532/DDO 137 System

    NASA Technical Reports Server (NTRS)

    Hoffman, G. L.; Lu, N. Y.; Salpeter, E. E.; Connell, B. M.

    1998-01-01

    H I synthesis mapping of NGC 4532 and DDO 137, a pair of Sm galaxies on the edge of the Virgo cluster, is used to determine rotation curves for each of the galaxies and to resolve the structure and kinematics of three extragalactic H I clouds embedded in an extended envelope of diffuse HI discovered in earlier Arecibo studies of the system.

  12. Compact microchannel system

    DOEpatents

    Griffiths, Stewart

    2003-09-30

    The present invention provides compact geometries for the layout of microchannel columns through the use of turns and straight channel segments. These compact geometries permit the use of long separation or reaction columns on a small microchannel substrate or, equivalently, permit columns of a fixed length to occupy a smaller substrate area. The new geometries are based in part on mathematical analyses that provide the minimum turn radius for which column performance in not degraded. In particular, we find that straight channel segments of sufficient length reduce the required minimum turn radius, enabling compact channel layout when turns and straight segments are combined. The compact geometries are obtained by using turns and straight segments in overlapped or nested arrangements to form pleated or coiled columns.

  13. Dark compact planets

    NASA Astrophysics Data System (ADS)

    Tolos, Laura; Schaffner-Bielich, Jürgen

    2015-12-01

    We investigate compact objects formed by dark matter admixed with ordinary matter made of neutron-star matter and white-dwarf material. We consider non-self annihilating dark matter with an equation of state given by an interacting Fermi gas. We find new stable solutions, dark compact planets, with Earth-like masses and radii from a few Km to few hundred Km for weakly interacting dark matter which are stabilized by the mutual presence of dark matter and compact star matter. For the strongly interacting dark matter case, we obtain dark compact planets with Jupiter-like masses and radii of few hundred Km. These objects could be detected by observing exoplanets with unusually small radii. Moreover, we find that the recently observed 2 M⊙ pulsars set limits on the amount of dark matter inside neutron stars which is, at most, 1 0-6 M⊙ .

  14. An evolutionary sequence of young radio galaxies

    NASA Astrophysics Data System (ADS)

    Collier, J. D.; Norris, R. P.; Filipović, M. D.; Tothill, N. F. H.

    2016-02-01

    We have observed the faintest sample of Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources to date, using the Australia Telescope Compact Array. We test the hypothesis that GPS and CSS sources are the youngest radio galaxies, place them into an evolutionary sequence along with a number of other young active galactic nuclei (AGN) candidates, and search for evidence of the evolving accretion mode and its relationship to star formation. GPS/CSS sources have very small radio jets that have been recently launched from the central supermassive black hole and grow in linear size as they evolve, which means that the linear size of the jets is an excellent indicator of the evolutionary stage of the AGN. We use high-resolution radio observations to determine the linear size of GPS/CSS sources, resolve their jets and observe their small-scale morphologies. We combine this with other multi-wavelength age indicators, including the spectral age, colours, optical spectra, and spectral energy distribution of the host galaxy, in an attempt to assemble all age indicators into a self-consistent model. We observe the most compact sources with Very Large Baseline Interferometry, which reveals their parsec-scale structures, giving us a range of source sizes and allowing us to test what fraction of GPS/CSS sources are young and evolving.

  15. Compact baby Skyrmions

    SciTech Connect

    Adam, C.; Klimas, P.; Sanchez-Guillen, J.; Wereszczynski, A.

    2009-11-15

    For the baby Skyrme model with a specific potential, compacton solutions, i.e., configurations with a compact support and parabolic approach to the vacuum, are derived. Specifically, in the nontopological sector, we find spinning Q-balls and Q-shells, as well as peakons. Moreover, we obtain compact baby skyrmions with nontrivial topological charge. All these solutions may form stable multisoliton configurations provided they are sufficiently separated.

  16. Compact, low power radio frequency cavity for femtosecond electron microscopy

    SciTech Connect

    Lassise, A.; Mutsaers, P. H. A.; Luiten, O. J.

    2012-04-15

    Reported here is the design, construction, and characterization of a small, power efficient, tunable dielectric filled cavity for the creation of femtosecond electron bunches in an existing electron microscope without the mandatory use of femtosecond lasers. A 3 GHz pillbox cavity operating in the TM{sub 110} mode was specially designed for chopping the beam of a 30 keV scanning electron microscope. The dielectric material used is ZrTiO{sub 4}, chosen for the high relative permittivity ({epsilon}{sub r}= 37 at 10 GHz) and low loss tangent (tan {delta}= 2 x 10{sup -4}). This allows the cavity radius to be reduced by a factor of six, while the power consumption is reduced by an order of magnitude compared to a vacuum pillbox cavity. These features make this cavity ideal as a module for existing electron microscopes, and an alternative to femtosecond laser systems integrated with electron microscopes.

  17. Radio frequency detection assembly and method for detecting radio frequencies

    SciTech Connect

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  18. The Planck Compact Source Catalogues: present and future.

    NASA Astrophysics Data System (ADS)

    López-Caniego, Marcos

    2015-08-01

    The Planck Collaboration has produced catalogues of radio and sub-mm compact sources at the nine Planck frequencies, Galactic cold clumps catalogues and SZ cluster catalogues. But new catalogues are foreseen. A multifrequency compact source catalogue will be produced selecting sources at radio frequencies and following them across all Planck bands. Multifrequency catalogues can be difficult to produce in experiments like Planck with a large frequency coverage and very different resolutions across bands, but the science that can be extracted from such a catalogue compensates the effort. In addition, for those sources where a clear identification can be made, we will attempt to include flux density information from Herschel and other experiments, in particular for those blazars that are bright in radio, sub-mm and even in gamma-ray frequencies, as seen by Fermi. Moreover, Planck is making available to the community the single survey frequency maps that will allow astronomers to study the long-term variability of their favourite sources. New functionalities will be added to the Planck Legacy Archive, for example a timeline-cutting tool that will allow one to extract maps from the Planck timelines for specific periods of time allowing short-term variability studies of compact sources (e.g., flares). The unique frequency coverage of Planck make these catalogues very valuable for other experiments using the Planck compact source catalogues. For example, experiments like QUIJOTE use Planck selected sources to study the impact of polarized radio source emission on their cosmological fields and other CMB experiments will use Planck polarized compact source information for calibration.

  19. On the origin of radio emission in radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Laor, Ari; Behar, Ehud

    2008-10-01

    The radio emission in radio-loud quasars originates in a jet carrying relativistic electrons. In radio-quiet quasars (RQQs) the relative radio emission is ~103 times weaker, and its origin is not established yet. We show here that there is a strong correlation between the radio luminosity (LR) and X-ray luminosity (LX) with LR ~ 10-5 LX, for the radio-quiet Palomar-Green (PG) quasar sample. The sample is optically selected, with nearly complete radio and X-ray detections, and thus this correlation cannot be due to direct selection biases. The PG quasars lie on an extension of a similar correlation noted by Panessa et al., for a small sample of nearby low-luminosity type 1 active galactic nuclei (AGN). A remarkably similar correlation, known as the Güdel-Benz relation, where LR/LX ~ 10-5, holds for coronally active stars. The Güdel-Benz relation, together with correlated stellar X-ray and radio variability, implies that the coronae are magnetically heated. We therefore raise the possibility that AGN coronae are also magnetically heated, and that the radio emission in RQQ also originates in coronal activity. If correct, then RQQ should generally display compact flat cores at a few GHz due to synchrotron self-absorption, while at a few hundred GHz we should be able to see directly the X-ray emitting corona, and relatively rapid and large amplitude variability, correlated with the X-ray variability, is likely to be seen. We also discuss possible evidence that the radio and X-ray emission in ultraluminous X-ray sources and Galactic black holes may be of coronal origin as well.

  20. Dark Matter Searches in the Gamma-ray Extragalactic Background via Cross-correlations with Galaxy Catalogs

    NASA Astrophysics Data System (ADS)

    Cuoco, Alessandro; Xia, Jun-Qing; Regis, Marco; Branchini, Enzo; Fornengo, Nicolao; Viel, Matteo

    2015-12-01

    We compare the measured angular cross-correlation between the Fermi-Large Area Telescope γ-ray sky and catalogs of extragalactic objects with the expected signal induced by weakly interacting massive particle (WIMP) dark matter (DM). We include a detailed description of the contribution of astrophysical γ-ray emitters such as blazars, misaligned active galactic nucleus (AGN), and star-forming galaxies, and perform a global fit to the measured cross-correlation. Five catalogs are considered: Sloan Digital Sky Survey (SDSS)-DR6 quasars, Two Micron All Sky Survey galaxies, NRAO VLA Sky Survey radio galaxies, SDSS-DR8 Luminous Red Galaxies, and the SDSS-DR8 main galaxy sample. To model the cross-correlation signal, we use the halo occupation distribution formalism to estimate the number of galaxies of a given catalog in DM halos and their spatial correlation properties. We discuss uncertainties in the predicted cross-correlation signal arising from the DM clustering and WIMP microscopic properties, which set the DM γ-ray emission. The use of different catalogs probing objects at different redshifts significantly reduces, though not completely, the degeneracy among the different γ-ray components. We find that the presence of a significant WIMP DM signal is allowed by the data but not significantly preferred by the fit, although this is mainly due to a degeneracy with the misaligned AGN component. With modest substructure boost, the sensitivity of this method excludes thermal annihilation cross sections at 95% level for WIMP masses up to few tens of GeV. Constraining the low-redshift properties of astrophysical populations with future data will further improve the sensitivity to DM.

  1. The asymmetric radio structure and record jet of giant quasar 4C 34.47

    NASA Astrophysics Data System (ADS)

    Hocuk, S.; Barthel, P. D.

    2010-11-01

    Context. Unification models for active galactic nuclei, AGN, predict that all quasars (radio sources associated with quasi-stellar objects) should be at a substantial angle with the sky plane. Aims: We test the predictions of the orientation unification model with the morphological and polarization properties of a giant quasar. Methods: The giant double-lobed radio source 4C 34.47, which is associated with quasi-stellar object B1721+343, is mapped at arcsecond scale resolution, and the data are subsequently analyzed within the context of current models for extragalactic radio sources. Results: Quasar 4C 34.47 displays a straight one-sided jet, measuring a record length of 380 kpc in its double-lobed radio structure. Assuming an intrinsically symmetric two-sided jet structure the radio source jet axis must be at least 33° away from the sky plane, that is within 57° from the line of sight. The radio polarization properties indicate that this giant source has largely outgrown the depolarizing halo that is generally associated with the host galaxies of powerful radio sources. The measured small depolarization asymmetry nevertheless agrees with its inferred orientation. Conclusions: All data for this giant radio source agree with its preferred orientation as predicted within the unification scheme for powerful radio sources. Seen under a small aspect angle the radio source is large, but not excessively large. The global properties of 4C 34.47 do not differ from other giant (old) FR2 radio sources: it is a slowly expanding low-luminosity radio source.

  2. The Tidbinbilla-U.K. Schmidt radio quasar identification program

    NASA Technical Reports Server (NTRS)

    Jauncey, D. L.; Batty, M. J.; Savage, A.; Gulkis, S.

    1983-01-01

    A program is under way at Tidbinbilla to measure accurate (up to 2 arcsec r.m.s) radio positions for compact sources in the Parkes 2.7 GHz survey south of declination -30 deg. Optical identifications are being made on the basis of radio-optical position coincidence alone, without regard to colour or morphology, using the U.K. Schmidt IIIa-J sky survey to a limiting magnitude of 22.5. This program is aimed at producing an evaluation of the radio quasar redshift distribution with particular emphasis on those objects with redshifts greater than 3.0.

  3. Fast Radio Burst Discovered in the Arecibo Pulsar ALFA Survey

    NASA Astrophysics Data System (ADS)

    Spitler, L. G.; Cordes, J. M.; Hessels, J. W. T.; Lorimer, D. R.; McLaughlin, M. A.; Chatterjee, S.; Crawford, F.; Deneva, J. S.; Kaspi, V. M.; Wharton, R. S.; Allen, B.; Bogdanov, S.; Brazier, A.; Camilo, F.; Freire, P. C. C.; Jenet, F. A.; Karako-Argaman, C.; Knispel, B.; Lazarus, P.; Lee, K. J.; van Leeuwen, J.; Lynch, R.; Ransom, S. M.; Scholz, P.; Siemens, X.; Stairs, I. H.; Stovall, K.; Swiggum, J. K.; Venkataraman, A.; Zhu, W. W.; Aulbert, C.; Fehrmann, H.

    2014-08-01

    Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4 GHz Pulsar Arecibo L-band Feed Array (ALFA) survey with the Arecibo Observatory with a DM = 557.4 ± 2.0 pc cm-3, pulse width of 3.0 ± 0.5 ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation of dispersion through an ionized medium. Despite its low Galactic latitude (b = -0.°2), the burst has three times the maximum Galactic DM expected along this particular line of sight, suggesting an extragalactic origin. A peculiar aspect of the signal is an inverted spectrum; we interpret this as a consequence of being detected in a sidelobe of the ALFA receiver. FRB 121102's brightness, duration, and the inferred event rate are all consistent with the properties of the previously detected Parkes bursts.

  4. Fast radio burst discovered in the Arecibo pulsar ALFA survey

    SciTech Connect

    Spitler, L. G.; Freire, P. C. C.; Lazarus, P.; Lee, K. J.; Cordes, J. M.; Chatterjee, S.; Wharton, R. S.; Brazier, A.; Hessels, J. W. T.; Lorimer, D. R.; McLaughlin, M. A.; Crawford, F.; Deneva, J. S.; Kaspi, V. M.; Karako-Argaman, C.; Allen, B.; Bogdanov, S.; Camilo, F.; Jenet, F. A.; Knispel, B.; and others

    2014-08-01

    Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4 GHz Pulsar Arecibo L-band Feed Array (ALFA) survey with the Arecibo Observatory with a DM = 557.4 ± 2.0 pc cm{sup –3}, pulse width of 3.0 ± 0.5 ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation of dispersion through an ionized medium. Despite its low Galactic latitude (b = –0.°2), the burst has three times the maximum Galactic DM expected along this particular line of sight, suggesting an extragalactic origin. A peculiar aspect of the signal is an inverted spectrum; we interpret this as a consequence of being detected in a sidelobe of the ALFA receiver. FRB 121102's brightness, duration, and the inferred event rate are all consistent with the properties of the previously detected Parkes bursts.

  5. Relating the Planetary Ephemerides and the Radio Reference Frame

    NASA Technical Reports Server (NTRS)

    Niell, A. E.; Newhall, X. X.; Preston, R. A.; Berge, G. L.; Muhleman, D. O.; Rudy, D. J.; Campbell, J. K.; Esposito, P. B.; Standish, E. M.

    1985-01-01

    The positions of Venus, Mars, and Jupiter were obtained in the VLBI radio reference frame by measuring the position of a satellite (natural or artificial) of each planet relative to an extragalactic source in the radio catalogue. From the results for Mars and Venus it is concluded that the offset in right ascension of the radio frame from the dynamical equinox defined in DE200 is 0.00 sec +/- 0.04 sec. The observations for Jupiter imply a correction to its position from DE200 of -0.18 sec +/- 0.04 sec in right ascension and -0.06 +/- 0.05 sec in declination on 1983 April 29. The right ascension of Jupiter relative to the inner planets has been measured independently using Doppler tracking data near Jupiter encounter from Pioneers 10 and 11 and from Voyagers 1 and 2 by tying the tracking station positions, through previous spacecraft missions, to the DE200 ephemerides of the inner planets. This technique yielded a correction to Jupiter's right ascension of -0.22 +/- 0.05 sec, in good agreement with the results from the direct radio measurements.

  6. Dominance of outflowing electric currents on decaparsec to kiloparsec scales in extragalactic jets

    NASA Astrophysics Data System (ADS)

    Christodoulou, Dimitris M.; Gabuzda, Denise C.; Knuettel, Sebastian; Contopoulos, Ioannis; Kazanas, Demosthenes; Coughlan, Colm P.

    2016-06-01

    Context. Helical magnetic fields embedded in the jets of active galactic nuclei (AGNs) are required by the broad range of theoretical models that advocate for electromagnetic launching of the jets. In most models, the direction of the magnetic field is random, but if the axial field is generated by a Cosmic Battery generated by current in the direction of rotation in the accretion disk, there is a correlation between the directions of the spin of the AGN accretion disk and of the axial field, which leads to a specific direction for the axial electric current, azimuthal magnetic field, and the resulting observed transverse Faraday-rotation (FR) gradient across the jet, due to the systematic change in the line-of-sight magnetic field. Aims: We consider new observational evidence for the presence of a nested helical magnetic-field structure such as would be brought about by the operation of the Cosmic Battery, and make predictions about the expected behavior of transverse FR gradients observed on decaparsec and kiloparsec scales. Methods: We have jointly considered 27 detections of transverse FR gradients on parsec scales, four reports of reversals in the directions of observed transverse FR gradients observed on parsec-decaparsec scales, and five detections of transverse FR gradients on decaparsec-kiloparsec scales, one reported here for the first time. We also consider seven tentative additional examples of transverse FR gradients on kiloparsec scales, based on an initial visual inspection of published Very Large Array FR maps of 85 extragalactic radio sources, for three of which we have carried out quantitative analyses in order to quantitatively estimate the significances of the gradients. Results: The data considered indicate a predominance of transverse FR gradients in the clockwise direction on the sky (i.e., net axial current flowing inward in the jet) on parsec scales and in the counter-clockwise direction on the sky (i.e., net axial current flowing outward

  7. The ATCA-SPT Survey of Southern Extragalactic Sky

    NASA Astrophysics Data System (ADS)

    Tothill, Nick; Filipovic, Miroslav; Walsh, Wilfred; Norris, Ray; Stark, Antony A.; Marrone, Dan; Crawford, Evan; Huynh, Minh; McIntyre, Vince; Vieira, Joaquin; Holzapfel, William; Murphy, Eric; Malkan, Matthew; Collier, Jordan; Seymour, Nick; O'Brien, Andrew; Spilker, Justin

    2013-10-01

    We request an additional 11 hours over 2 days to complete our previous proposal. Approximately 22.5 hours of scheduled time were lost in the previous semester: 16.5 hours lost due to strong mid-week RFI that saturated the data; and 6 hours to a ToO observation on 30 May 2013. As the RFI was generally constrained to the end of our observations where we had the most hour angle coverage, most of the affected observations were recovered within our allocated time. We require this additional 11 hours (inclusive of overheads) to complete our field to attain our goal of uniform sensitivity with good tangential uv-coverage. We propose to map the 100-square degree SPT deep field to an rms noise of 40 microJy/beam at a wavelength of 16cm. We expect to detect 30,000 to 40,000 sources, of which we expect at least 10,000 to be dusty star-forming galaxies detected by Herschel. We will also find large samples of AGN, lensed submm galaxies, and other populations. The combination of ATCA, SPT and SPIRE data will allow us to estimate redshifts, probe the FIR-Radio Correlation, and examine the structure of dark matter halos by comparison with CMB lensing maps. The ATCA maps will also deliver accurate galaxy positions, which will be used to break the confusion of Herschel-SPIRE maps of the field, to obtain optical/IR identifications, and to obtain spectroscopic redshifts. This will in turn allow us to analyse the CIB.

  8. Photometric and kinematic studies of extragalactic globular cluster systems

    NASA Astrophysics Data System (ADS)

    Dowell, Jessica

    Globular clusters (GCs) are old, luminous, compact collections of stars found in galaxy halos that formed during the early stages of galaxy formation. Because of this, GCs serve as excellent tracers of the formation, structure, and merger history of their host galaxies. My dissertation will examine both the photometric and kinematic properties of GC systems and their relationship to their host galaxies. In the first section, I will present the analysis of the GC systems of two spiral galaxies, NGC 891 and NGC 1055. I will discuss the photometric methods used to detect GCs using wide-field BVR imaging and to quantify the global properties of the system such as the total number of GCs and their radial distribution. My results for these two GC systems were compared to those of other galaxies. I will also present the results of spectroscopic follow-up for two giant galaxies: the S0 galaxy NGC 4594 (M104), and the elliptical galaxy NGC 3379 (M105). I measured the radial velocities of GCs in these two galaxies, and combined them with published results to determine the mass distribution and mass-to-light (M/L) ratio profile for each galaxy out to large effective radius (7-9 Re). For both galaxies, I found that the M/L profiles increase with radius and do not flatten, which suggests that the dark matter halos in these galaxies extend to the edge of my data. I also looked for evidence of rotation in the GC systems, and found that neither system exhibits significant rotation around the host galaxy. I examined the velocity dispersion profile of each GC system and found kinematic differences between the red and blue GC subpopulations. Finally, I compared my results to mass estimates for these galaxies from other kinematic tracers and considered them in the context of galaxy formation models.

  9. Flat spectrum multicomponent radio sources - Cosmic conspiracy or geometry

    SciTech Connect

    Pacholczyk, A.G.

    1981-01-01

    Compact radio sources which do not exhibit currently large flux density variations, are often characterized by spectra nearly flat over a wide range of wavelengths. Cotton et al. (1980) recently reported the results of the VLBI multifrequency interferometric and total flux density observations of a typical representative of the flat spectrum class of sources, a BL Lacertae object PKS 0735+178. If 0735+178 is indeed representative of flat spectrum sources, then some mechanism causing the component production and energy loss to be balanced must be operative among this type of radio source to maintain a flat spectrum over at least certain periods of time. This effect is referred to as 'cosmic conspiracy'. It is suggested that the flatness of spectra of this class of radio sources may be related to a specific symmetry in the radio structure, namely, to a predominantly linear, one-dimensional evolution of radio radiating material, rather than spherical, three-dimensional evolution.

  10. GPS/CSS radio sources and their relation to other AGN

    NASA Astrophysics Data System (ADS)

    Sadler, E. M.

    2016-02-01

    We are entering a new era of sensitive, large-area and multi-frequency radio surveys that will allow us to identify Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) radio sources over a wide range in radio luminosity and study them within the context of the overall radio-source populations to which they belong. ``Classical'' GPS/CSS objects are extremely luminous radio sources with a compact double morphology, commonly thought to represent the earliest stages in the life cycle of powerful radio galaxies (e.g. O'Dea 1998). It is now becoming easier to identify GPS/CSS candidates with much lower radio luminosity - particularly in the nearby Universe. These less powerful objects, with typical 1.4 GHz radio luminosities of 1023 to 1025 W Hz-1, include peaked-spectrum radio sources with a core-jet morphology on parsec scales as well as high-frequency GPS-like peaked components embedded within lower-frequency extended emission. In the latter case, the presence of a young GPS component may not be evident from low-frequency data alone. Many radio galaxies in the local Universe have a compact (FR-0) morphology, and appear to lack extended radio emission on kiloparsec scales. The relationship of these FR-0 objects to the classical GPS/CSS radio sources remains unclear - some of them may represent short-lived episodes of AGN activity that will not lead to an extended FR-1 or FR-2 radio galaxy. Future wide-band radio surveys will shed more light on this - such surveys should ideally be coordinated to cover the full frequency range from 100 MHz to 100 GHz in order to sample all stages of GPS/CSS evolution in an unbiased way.

  11. High Resolution Radio Imaging of the Merging Galaxies NGC3256 and NGC4194

    NASA Technical Reports Server (NTRS)

    Neff, S. G.; Campion, S. D.; Ulvestad, J. S.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    We present new 6cm and 4cm radio continuum images of the central regions of the merging galaxy systems NGC3256 and NGC4194. NGC3256 is imaged with a resolution of approx. 1 in. or approx. 190pc; NGC4194 is imaged with a resolution of approx. 0.3 in. or approx. 50pc. In both systems, we detect numerous compact radio sources embedded in more diffuse radio emission. We detect 65 compact sources in NGC3256 at 6cm and we detect 46 compact sources in NGC4194, both to a limiting luminosity of approx. 5 x 10(exp 18) W/ Hz or approx. 5 times the luminosity of Cas A. Most of the compact radio sources are loosely associated with active star forming regions but not with specific optical emission sources. Several compact radio sources in NGC3256 are near positions of compact X-ray sources detected by Lira et al.. In both NGC3256 and NGC4194, we are able to measure reliable spectral indices for the stronger sources. We find in NGC3256 approx. 20% have nominally flat radio spectral indices (indicating they are dominated by thermal radio emission from HII regions) while approx. 80% have nominally steep spectral indices (indicating they are dominated by nonthermal emission from supernova remnants). In NGC4194, half the compact radio sources have flat spectral indices and half have steep indices. For the flat-spectrum sources, we estimate the number of young massive stars and the associated ionized gas masses. For the steep-spectrum sources, we estimate supernova rates. We compare these results with those from other well-studied merging galaxy systems. We gratefully acknowledge use of the NRAO Very Large Array (VLA) and the VLA Archive. NRAO is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  12. Tomography of the Fermi-LAT γ-Ray Diffuse Extragalactic Signal via Cross Correlations with Galaxy Catalogs

    NASA Astrophysics Data System (ADS)

    Xia, Jun-Qing; Cuoco, Alessandro; Branchini, Enzo; Viel, Matteo

    2015-03-01

    Building on our previous cross-correlation analysis (Xia et al. 2011) between the isotropic γ-ray background (IGRB) and different tracers of the large-scale structure of the universe, we update our results using 60 months of data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi). We perform a cross-correlation analysis both in configuration and spherical harmonics space between the IGRB and objects that may trace the astrophysical sources of the IGRB: QSOs in the Sloan Digital Sky Survey (SDSS) DR6, the SDSS DR8 Main Galaxy Sample, luminous red galaxies (LRGs) in the SDSS catalog, infrared-selected galaxies in the Two Micron All Sky Survey (2MASS), and radio galaxies in the NRAO VLA Sky Survey (NVSS). The benefit of correlating the Fermi-LAT signal with catalogs of objects at various redshifts is to provide tomographic information on the IGRB, which is crucial in separating the various contributions and clarifying its origin. The main result is that, unlike in our previous analysis, we now observe a significant (>3.5σ) cross-correlation signal on angular scales smaller than 1° in the NVSS, 2MASS, and QSO cases and, at lower statistical significance (∼3.0σ), with SDSS galaxies. The signal is stronger in two energy bands, E > 0.5 GeV and E > 1 GeV, but it is also seen at E > 10 GeV. No cross-correlation signal is detected between Fermi data and the LRGs. These results are robust against the choice of the statistical estimator, estimate of errors, map cleaning procedure, and instrumental effects. Finally, we test the hypothesis that the IGRB observed by Fermi-LAT originates from the summed contributions of three types of unresolved extragalactic sources: BL Lacertae objects (BL Lacs), flat spectrum radio quasars (FSRQs), and star-forming galaxies (SFGs). We find that a model in which the IGRB is mainly produced by SFGs (72-37+23% with 2σ errors), with BL Lacs and FSRQs giving a minor contribution, provides a good fit to

  13. Resonance and Radio

    ERIC Educational Resources Information Center

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

  14. Triggered Jovian radio emissions

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1985-01-01

    Certain Jovian radio emissions seem to be triggered from outside, by much weaker radio waves from the sun. Recently found in the Voyager observations near Jupiter, such triggering occurs at hectometric wavelengths during the arrival of solar radio bursts, with the triggered emissions lasting sometimes more than an hour as they slowly drifted toward higher frequencies. Like the previous discovery of similar triggered emissions at the earth, this suggests that Jupiter's emissions might also originate from natural radio lasers.

  15. Photometric and Kinematic Studies of Extragalactic Globular Cluster Systems

    NASA Astrophysics Data System (ADS)

    Windschitl-Dowell, Jessica L.

    2015-01-01

    Globular clusters (GCs) are compact, luminous collections of stars created during the early stages of galaxy formation. As a result, the properties of GC systems provide important clues about the formation, merger history, and structure of their host galaxies. In particular, kinematic studies of GCs can be used to investigate the dark matter distribution in galaxy halos and provide observational evidence that can be used to constrain models of galaxy formation. I will present our study of the GC systems of two spiral galaxies, NGC 891 and NGC 1055, and show how we used wide-field BVR imaging from the WIYN 3.5-m telescope to detect the GC population and measure the global properties of the system. We quantified the radial distribution of the GC system and total number of GCs in these galaxies and compared the results to those of other galaxies.I will also present the results of spectroscopic follow-up for two giant galaxies: the S0 galaxy NGC 4594 (M104), and the elliptical galaxy NGC 3379 (M105). Using spectra taken with AAT/AAOmega, WIYN/HYDRA, and MMT/Hectospec, I measured the radial velocities of GCs, and combined them with published results to determine the mass distribution and V-band mass-to-light (M/LV) ratio profile for each galaxy out to large effective radius (7-9 Re). I compared our results to mass estimates from other kinematic tracers and also considered them in the context of galaxy formation models. For both galaxies, I found that the M/LV profiles increase with radius and do not flatten, which suggests that the dark matter halos in these galaxies extend to the edge of our data. I also looked for evidence of rotation within the GC systems, and found that neither system exhibits significant rotation around the host galaxy. Finally, I examined the velocity dispersion of each GC system as a function of radius and found kinematic differences between the red, metal-rich and blue, metal-poor GC subpopulations.

  16. Commercial Radio as Communication.

    ERIC Educational Resources Information Center

    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…

  17. BLAZAR HALOS AS PROBE FOR EXTRAGALACTIC MAGNETIC FIELDS AND MAXIMAL ACCELERATION ENERGY

    SciTech Connect

    Dolag, K.; Kachelriess, M.; Ostapchenko, S.; Tomas, R.

    2009-09-20

    High-energy photons from blazars interact within tens of kpc with the extragalactic photon background, initiating electromagnetic pair cascades. The charged component of such cascades is deflected by extragalactic magnetic fields (EGMFs), leading to halos even around initially point-like sources. We calculate the intensity profile of the resulting secondary high-energy photons for different assumptions on the initial source spectrum and the strength of the EGMF, employing also fields found earlier in a constrained simulation of structure formation including magnetohydrodynamics processes. We find that the observation of halos around blazars like Mrk 180 probes an interesting range of EGMF strengths and acceleration models: in particular, blazar halos test if the photon energy spectrum at the source extends beyond {approx}100 TeV and how anisotropic this high-energy component is emitted.

  18. Anisotropies of ultrahigh energy cosmic ray nuclei diffusing from extragalactic sources

    NASA Astrophysics Data System (ADS)

    Harari, Diego; Mollerach, Silvia; Roulet, Esteban

    2015-09-01

    We obtain the dipolar anisotropies in the arrival directions of ultrahigh energy cosmic ray nuclei diffusing from nearby extragalactic sources. We consider mixed-composition scenarios in which different cosmic ray nuclei are accelerated up to the same maximum rigidity, so that E extragalactic turbulent fields as well as the effects of photodisintegrations and other energy losses. Dipolar anisotropies at the level of 5% to 10% at energies ˜10 EeV are predicted for plausible values of the source density and magnetic fields.

  19. Blazar Gamma-Rays, Shock Acceleration, and the Extragalactic Background Light

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.; Baring, Matthew G.; Summerlin, Errol J.

    2007-01-01

    The observed spectra of blazars, their intrinsic emission, and the underlying populations of radiating particles are intimately related. The use of these sources as probes of the extragalactic infrared background, a prospect propelled by recent advances in TeV-band telescopes, soon to be augmented by observations by NASA's upcoming Gamma-Ray Large Area Space Telescope (GLAST), has been a topic of great recent interest. Here, it is demonstrated that if particles in blazar jets are accelerated at relativistic shocks, then GAMMA-ray spectra with indices less than 1.5 can be produced. This, in turn, loosens the upper limits on the near infrared extragalactic background radiation previously proposed. We also show evidence hinting that TeV blazars with flatter spectra have higher intrinsic TeV GAMMA-ray luminosities and we indicate that there may be a correlation of flatness and luminosity with redshift.

  20. Sharp edges to neutral hydrogen disks in galaxies and the extragalactic radiation field

    NASA Technical Reports Server (NTRS)

    Maloney, Philip

    1993-01-01

    It is shown that the very sharp truncation of the neutral hydrogen distribution seen in NGC 3198 (and probably M33) is well modeled as the result of ionization of the atomic gas by the extragalactic radiation field. Below a critical column density of about a few times 10 exp 19/sq cm the gas is dominantly ionized and undetectable in the 21-cm line. It is inferred from the photoionization models that the total disk gas distribution in NGC 3198 is actually fairly axisymmetric. The critical column density for ionization is not a strong function of galaxy mass or mass distribution; thus, all galaxies should show a cutoff at approximately the same column density. Specific models of 3198 suggest that the extragalactic ionizing photon flux is 5000-10,000 photons/sq cm s.

  1. Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

    NASA Technical Reports Server (NTRS)

    Venters, T. M.; Pavlidou, V.

    2013-01-01

    The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

  2. Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Venters, T. M.; Pavlidou, V.

    2012-01-01

    The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

  3. Extragalactic Science with the Next Generation of Ground Based TeV {gamma}-Ray Telescopes

    SciTech Connect

    Krawczynski, Henric

    2008-12-24

    The ground based Cherenkov telescope experiments H.E.S.S., MAGIC, and VERITAS, and the space borne Fermi Gamma-Ray Space Telescope are currently exploring the galactic and extragalactic Universe in {gamma}-rays. At the time of writing this article, a large number of Active Galactic Nuclei have been studied in great detail and the {gamma}-ray observations have had a major impact on our understanding of the structure of jets from these objects. In this contribution, the status of ground based {gamma}-ray observations of AGN and other extragalactic source classes is reviewed as of October, 2008. After discussing source classes that could be detected with next generation ground based experiments like AGIS, CTA, and HAWC, the potential impact of the observations on the fields of high energy astrophysics, structure formation, observational cosmology, and fundamental physics is reviewed. We close with a discussion of the technical requirements that arise from the science drivers.

  4. MIMO communications within the HF band using compact antenna arrays

    NASA Astrophysics Data System (ADS)

    Gunashekar, S. D.; Warrington, E. M.; Feeney, S. M.; Salous, S.; Abbasi, N. M.

    2010-12-01

    Measurements have been made over a 255 km radio path between Durham and Leicester in the UK in order to investigate the potential applicability of multiple input multiple output (MIMO) techniques to communications within the HF band. This paper describes the results from experiments in which compact heterogeneous antenna arrays have been employed. The results of these experiments indicate that traditional spaced HF antenna arrays can be replaced by compact, active, heterogeneous arrays in order to achieve the required levels of decorrelation between the various antenna elements. An example case study is also presented which highlights the importance of the variable nature of the ionosphere in the context of HF-MIMO radio links.

  5. The likelihood ratio as a tool for radio continuum surveys with Square Kilometre Array precursor telescopes

    NASA Astrophysics Data System (ADS)

    McAlpine, K.; Smith, D. J. B.; Jarvis, M. J.; Bonfield, D. G.; Fleuren, S.

    2012-06-01

    In this paper we investigate the performance of the likelihood ratio method as a tool for identifying optical and infrared counterparts to proposed radio continuum surveys with Square Kilometre Array (SKA) precursor and pathfinder telescopes. We present a comparison of the infrared counterparts identified by the likelihood ratio in the VISTA Deep Extragalactic Observations (VIDEO) survey to radio observations with 6, 10 and 15 arcsec resolution. We cross-match a deep radio catalogue consisting of radio sources with peak flux density >60 ?Jy with deep near-infrared data limited to Ks≲ 22.6. Comparing the infrared counterparts from this procedure to those obtained when cross-matching a set of simulated lower resolution radio catalogues indicates that degrading the resolution from 6 arcsec to 10 and 15 arcsec decreases the completeness of the cross-matched catalogue by approximately 3 and 7 per cent respectively. When matching against shallower infrared data, comparable to that achieved by the VISTA Hemisphere Survey, the fraction of radio sources with reliably identified counterparts drops from ˜89 per cent, at Ks≲ 22.6, to 47 per cent with Ks≲ 20.0. Decreasing the resolution at this shallower infrared limit does not result in any further decrease in the completeness produced by the likelihood ratio matching procedure. However, we note that radio continuum surveys with the MeerKAT and eventually the SKA, will require long baselines in order to ensure that the resulting maps are not limited by instrumental confusion noise.

  6. Extragalactic radiation and the ultra-high-energy cosmic-ray spectrum

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1989-01-01

    The effect of extragalactic microwave and submillimeter-radiation fields on the ultrahigh-energy cosmic-ray spectrum is reexamined. It is found that the general characteristics of the spectrum can be derived from fairly simple analytical arguments. It is shown that the various spectral features obtained by numerical calculations can be explored by simpler and more general means. This approach is illustrated using a newly derived lifetime-energy relation based on the new submillimeter observations.

  7. Limestone compaction: an enigma

    USGS Publications Warehouse

    Shinn, Eugene A.; Halley, Robert B.; Hudson, J. Harold; Lidz, Barbara H.

    1977-01-01

    Compression of an undisturbed carbonate sediment core under a pressure of 556 kg/cm2 produced a “rock” with sedimentary structures similar to typical ancient fine-grained limestones. Surprisingly, shells, foraminifera, and other fossils were not noticeably crushed, which indicates that absence of crushed fossils in ancient limestones can no longer be considered evidence that limestones do not compact.

  8. Compact optical transconductance varistor

    SciTech Connect

    Sampayan, Stephen

    2015-09-22

    A compact radiation-modulated transconductance varistor device having both a radiation source and a photoconductive wide bandgap semiconductor material (PWBSM) integrally formed on a substrate so that a single interface is formed between the radiation source and PWBSM for transmitting PWBSM activation radiation directly from the radiation source to the PWBSM.

  9. COMPACT SCHOOL AND $$ SAVINGS.

    ERIC Educational Resources Information Center

    BAIR, W.G.

    A REVIEW OF THE CRITERIA FOR CONSIDERING THE USE OF A TOTAL ENERGY SYSTEM WITHIN A SCHOOL BUILDING STATES THE WINDOWLESS, COMPACT SCHOOL OFFERS MORE EFFICIENT SPACE UTILIZATION WITH LESS AREA REQUIRED FOR GIVEN STUDENT POPULATION AND LOWER OPERATION COSTS. THE AUTHOR RECOMMENDS THAT THESE BUILDINGS BE WINDOWLESS TO REDUCE HEAT COSTS, HOWEVER, AT…

  10. Inhomogeneous extragalactic magnetic fields and the second knee in the cosmic ray spectrum

    SciTech Connect

    Kotera, Kumiko; Lemoine, Martin

    2008-01-15

    Various experiments indicate the existence of a second knee around energy E=3x10{sup 17} eV in the cosmic ray spectrum. This feature could be the signature of the end of the galactic component and of the emergence of the extragalactic one, provided that the latter cuts off at low energies. Recent analytical calculations have shown that this cutoff could be a consequence of the existence of extragalactic magnetic fields (Refs. [M. Lemoine, Phys. Rev. D 71, 083007 (2005).][R. Aloisio and V. Berezinsky, Astrophys. J. 625, 249 (2005).]): low energy protons diffuse on extragalactic magnetic fields and cannot reach the observer within a given time. We study the influence of inhomogeneous magnetic fields on the magnetic horizon, using a new semianalytical propagation code. Our results indicate that, at a fixed value of the volume averaged magnetic field , the amplitude of the low energy cutoff is mainly controlled by the strength of magnetic fields in the voids of the large-scale structure distribution.

  11. Escape model for Galactic cosmic rays and an early extragalactic transition

    NASA Astrophysics Data System (ADS)

    Giacinti, G.; Kachelrieß, M.; Semikoz, D. V.

    2015-04-01

    We show that the cosmic ray (CR) knee can be entirely explained by energy-dependent CR leakage from the Milky Way, with an excellent fit to all existing data. We test this hypothesis calculating the trajectories of individual CRs in the Galactic magnetic field. We find that the CR escape time τesc(E ) exhibits a knee-like structure around E /Z =few×1015 eV for small coherence lengths and strengths of the turbulent magnetic field. The resulting intensities for different groups of nuclei are consistent with the ones determined by KASCADE and KASCADE-Grande, using simple power laws as injection spectra. The transition from Galactic to extragalactic CRs is terminated at ≈2 ×1018 eV , while extragalactic CRs contribute significantly to the subdominant proton flux already for ≳2 ×1016 eV . The natural source of extragalactic CRs in the intermediate energy region up to the ankle are in this model normal and starburst galaxies. The escape model provides a good fit to ln (A ) data; it predicts that the phase of the CR dipole varies strongly in the energy range between 1 ×1017 and 3 ×1018 eV , while our estimate for the dipole magnitude is consistent with observations.

  12. Stochastic conversions of TeV photons into axion-like particles in extragalactic magnetic fields

    SciTech Connect

    Mirizzi, Alessandro; Montanino, Daniele E-mail: daniele.montanino@le.infn.it

    2009-12-01

    Very-high energy photons emitted by distant cosmic sources are absorbed on the extragalactic background light (EBL) during their propagation. This effect can be characterized in terms of a photon transfer function at Earth. The presence of extragalactic magnetic fields could also induce conversions between very high-energy photons and hypothetical axion-like particles (ALPs). The turbulent structure of the extragalactic magnetic fields would produce a stochastic behaviour in these conversions, leading to a statistical distribution of the photon transfer functions for the different realizations of the random magnetic fields. To characterize this effect, we derive new equations to calculate the mean and the variance of this distribution. We find that, in presence of ALP conversions, the photon transfer functions on different lines of sight could have relevant deviations with respect to the mean value, producing both an enhancement or a suppression in the observable photon flux with respect to the expectations with only absorption. As a consequence, the most striking signature of the mixing with ALPs would be a reconstructed EBL density from TeV photon observations which appears to vary over different directions of the sky: consistent with standard expectations in some regions, but inconsistent in others.

  13. Isotropic extragalactic flux from dark matter annihilations: lessons from interacting dark matter scenarios

    NASA Astrophysics Data System (ADS)

    Moliné, Ángeles; Schewtschenko, Jascha A.; Palomares-Ruiz, Sergio; Bœhm, Céline; Baugh, Carlton M.

    2016-08-01

    The extragalactic γ-ray and neutrino emission may have a contribution from dark matter (DM) annihilations. In the case of discrepancies between observations and standard predictions, one could infer the DM pair annihilation cross section into cosmic rays by studying the shape of the energy spectrum. So far all analyses of the extragalactic DM signal have assumed the standard cosmological model (ΛCDM) as the underlying theory. However, there are alternative DM scenarios where the number of low-mass objects is significantly suppressed. Therefore the characteristics of the γ-ray and neutrino emission in these models may differ from ΛCDM as a result. Here we show that the extragalactic isotropic signal in these alternative models has a similar energy dependence to that in ΛCDM, but the overall normalisation is reduced. The similarities between the energy spectra combined with the flux suppression could lead one to misinterpret possible evidence for models beyond ΛCDM as being due to CDM particles annihilating with a much weaker cross section than expected.

  14. Extragalactic Transients Discovered by the All-Sky Automated Survey for Supernovae

    NASA Astrophysics Data System (ADS)

    Brown, Jonathan; Warren-Son Holoien, Thomas; ASAS-SN

    2016-01-01

    Even in the modern era, only human eyes can scan the entire optical sky for the violent, variable, and transient events that shape our universe. The "All-Sky Automated Survey for Supernovae" (ASAS-SN or "Assassin") is changing this by monitoring the extra-galactic sky down to V~17 mag every 2-3 days using multiple telescopes, hosted by Las Cumbres Observatory Global Telescope Network, in the northern and southern hemispheres. The primary goal of ASAS-SN is to discover bright, nearby supernovae (SNe), we are discovering more than 60% of supernovae with V<17. Since June 2013, we have discovered 224 supernovae, 133 in 2015 alone (as of September 30, 2015). ASAS-SN has also discovered many other interesting extragalactic transients, including the three closest tidal disruption events (TDEs) ever discovered at optical wavelengths. The nearby nature of ASASSN discoveries allows detailed follow-up across a wide wavelength coverage; here we present some of these data on recent ASAS-SN extragalactic transients.

  15. Extragalactic Transients Discovered by the All-Sky Automated Survey for SuperNovae

    NASA Astrophysics Data System (ADS)

    Warren-Son Holoien, Thomas; ASAS-SN Team

    2015-01-01

    Even in the modern era, only human eyes scan the entire optical sky for the violent, variable, and transient events that shape our universe. The "All Sky Automated Survey for SuperNovae" (ASAS-SN or "Assassin") is changing this by monitoring the extra-galactic sky down to V~17 mag every 2-3 days using multiple telescopes in the northern and southern hemispheres, hosted by Las Cumbres Observatory Global Telescope Network. The primary goal of ASAS-SN is a complete survey of bright, nearby supernovae (SNe), and since April 2013 ASAS-SN has discovered over 40 new Type-Ia SNe and over 15 new core collapse SNe, including roughly half of all the SNe currently visible with V<17 mag. ASAS-SN also discovers many other interesting extragalactic transients, the most exciting of which was the recent tidal disruption event (TDE) ASASSN-14ae at ~200 Mpc, the closest TDE ever discovered at optical wavelengths. The brightness of these nearby events allows detailed follow-up at many wavelengths. Here we present some of these data on recent ASAS-SN extragalactic transients.

  16. Effects of the galactic magnetic field upon large scale anisotropies of extragalactic cosmic rays

    SciTech Connect

    Harari, D.; Mollerach, S.; Roulet, E. E-mail: mollerach@cab.cnea.gov.ar

    2010-11-01

    The large scale pattern in the arrival directions of extragalactic cosmic rays that reach the Earth is different from that of the flux arriving to the halo of the Galaxy as a result of the propagation through the galactic magnetic field. Two different effects are relevant in this process: deflections of trajectories and (de)acceleration by the electric field component due to the galactic rotation. The deflection of the cosmic ray trajectories makes the flux intensity arriving to the halo from some direction to appear reaching the Earth from another direction. This applies to any intrinsic anisotropy in the extragalactic distribution or, even in the absence of intrinsic anisotropies, to the dipolar Compton-Getting anisotropy induced when the observer is moving with respect to the cosmic rays rest frame. For an observer moving with the solar system, cosmic rays traveling through far away regions of the Galaxy also experience an electric force coming from the relative motion (due to the rotation of the Galaxy) of the local system in which the field can be considered as being purely magnetic. This produces small changes in the particles momentum that can originate large scale anisotropies even for an isotropic extragalactic flux.

  17. First `Winged' and `X'-shaped Radio Source Candidates

    SciTech Connect

    Cheung, C.C.

    2007-01-22

    A small number of double-lobed radio galaxies (17 from our own census of the literature) show an additional pair of low surface brightness ''wings'', thus forming an overall ''X''-shaped appearance. The origin of the wings in these radio sources is unclear. They may be the result of back-flowing plasma from the currently active radio lobes into an asymmetric medium surrounding the active nucleus, which would make these ideal systems in which to study thermal/non-thermal plasma interactions in extragalactic radio sources. Another possibility is that the wings are the aging radio lobes left over after a (rapid) realignment of the central supermassive black-hole/accretion disk system due perhaps to a merger. Generally, these models are not well tested; with the small number of known examples, previous works focused on detailed case studies of selected sources with little attempt at a systematic study of a large sample. Using the VLA-FIRST survey database, we are compiling a large sample of winged and X-shaped radio sources for such studies. As a first step toward this goal, an initial sample of 100 new candidate objects of this type are presented in this paper. The search process is described, optical identifications from available literature data, and basic radio data are presented. From the limited resolution FIRST images ({approx} 5''), we can already confidently classify a sufficient number of these objects as having the characteristic wing lengths >80% of the active lobes to more than double the number of known X-shaped radio sources. We have also included as candidates, radio sources with shorter wings (<80% wing to lobe length ratios), or simply ''winged'' sources, as it is probable that projection effects are important. Finally, among the candidates are four quasars (z=0.37 to 0.84), and several have morphologies suggestive of Fanaroff-Riley type-I (low-power) radio galaxies. While followup observations are necessary to confirm these identifications, this

  18. Radio-Quiet Quasars in the VIDEO Survey: Evidence for AGN-powered radio emission below 1 mJy

    NASA Astrophysics Data System (ADS)

    White, Sarah; Jarvis, Matt; Haeussler, Boris; Maddox, Natasha

    2015-01-01

    Several lines of evidence suggest that the interaction between active galactic nucleus (AGN) activity and star formation is responsible for the co-evolution of black hole mass with galaxy bulge mass. Therefore studying this interplay is crucial to our understanding of galaxy formation and evolution. The new generation of radio surveys are able to play a key role in this area, as both processes produce radio emission.We use a combination of optical and near-infrared photometry to select a sample of 72 quasars from the VISTA Deep Extragalactic Observations (VIDEO) Survey, over 1 deg2. The depth of VIDEO allows us to study very low accretion rates and/or lower-mass black holes. 26% of the candidate quasar sample has been spectroscopically confirmed using the Southern African Large Telescope and the VIMOS VLT Deep Survey. We then use a radio-stacking technique to sample below the nominal flux-density threshold of existing Very Large Array data at 1.4 GHz. In agreement with other work, we show that a power-law fit to the radio number counts is inadequate, with an upturn in the counts being observed at these faint luminosities. Previous authors attribute this to an emergent star-forming population. However, by comparing radio emission from our quasars with that from a control sample of galaxies, we suggest that this emission is predominantly caused by accretion activity. Further support for an AGN origin is provided by a comparison of two independent estimates of star formation rate. These findings have important implications for modelling radio populations below 1 mJy, which is necessary for the development of the Square Kilometre Array.

  19. Progress in Compact Toroid Experiments

    SciTech Connect

    Dolan, Thomas James

    2002-09-01

    The term "compact toroids" as used here means spherical tokamaks, spheromaks, and field reversed configurations, but not reversed field pinches. There are about 17 compact toroid experiments under construction or operating, with approximate parameters listed in Table 1.

  20. 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

    SciTech Connect

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

    2011-10-10

    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 {mu}Jy at the field center and redshift {approx}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 {approx}> 3 x 10{sup 24} W Hz{sup -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 {approx}30% of the sample and {approx}60% of all AGNs, and outnumbering radio-loud AGNs at {approx}< 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.

  1. 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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    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 × 1024 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.

  2. Deep galaxy count predictions in the radio, infrared, and X-ray spectral bands

    NASA Technical Reports Server (NTRS)

    Treyer, Marie-Agnes; Silk, Joseph

    1993-01-01

    The existence of a dominant population of strongly evolving starburst sources at moderate redshift is a plausible explanation for the excess number of faint blue galaxies detected in deep sky surveys. Multiwavelength observations at faint magnitudes would allow the existence of such a population to be confirmed. We use observed luminosity correlations and physical properties of known starburst galaxies to predict their contribution to the deep radio, infrared, and X-ray counts, as well as to the diffuse extragalactic background radiation in these various spectral bands.

  3. Electromagnetic Counterparts of Gravitational Wave Sources: Mergers of Compact Objects

    NASA Astrophysics Data System (ADS)

    Kamble, Atish; Kaplan, David L. A.

    2013-01-01

    Mergers of compact objects are considered prime sources of gravitational waves (GW) and will soon be targets of GW observatories such as the Advanced-LIGO and VIRGO. Finding electromagnetic counterparts of these GW sources will be important to understand their nature. We discuss possible electromagnetic signatures of the mergers. We show that the BH-BH mergers could have luminosities which exceed Eddington luminosity from unity to several orders of magnitude depending on the masses of the merging BHs. As a result these mergers could be explosive, release up to 1051 erg of energy and shine as radio transients. At any given time we expect about a few such transients in the sky at GHz frequencies, which could be detected to be about 300 Mpc. It has also been argued that these radio transients would look alike radio supernovae with comparable detection rates. Multi-band follow-up could, however, distinguish between the mergers and supernovae.

  4. Research in geodesy and geophysics based upon radio-interferometric observations of extragalactic radio sources. Final report, December 1984-December 1985

    SciTech Connect

    Clark, T.A.; Davis, J.L.; Gwinn, C.R.; Herring, T.A.; Ryan, J.W.

    1986-10-01

    This report consists of a collection of reprints and preprints. Subjects included: description of Mk-III system for very-long-baseline interferometry (VLBI); geodetic results from the Mk-I and Mk-III systems for VLBI; effects of modeling atmospheric propagation on estimates of baseline length and station height; an improved model for the dry propagation delay; corrections to IAU 1980 nutation series based on VLBI data and geophysical interpretation of those corrections; and a review of the contributions of VLBI to geodynamic studies.

  5. Engineering Prototype for a Compact Medical Dielectric Wall Accelerator

    NASA Astrophysics Data System (ADS)

    Zografos, Anthony; Hening, Andy; Joshkin, Vladimir; Leung, Kevin; Pearson, Dave; Pearce-Percy, Henry; Rougieri, Mario; Parker, Yoko; Weir, John; Blackfield, Donald; Chen, Yu-Jiuan; Falabella, Steven; Guethlein, Gary; Poole, Brian; Hamm, Robert W.; Becker, Reinard

    2011-12-01

    A compact accelerator system architecture based on the dielectric wall accelerator (DWA) for medical proton beam therapy has been developed by the Compact Particle Acceleration Corporation (CPAC). The major subsystems are a Radio Frequency Quadrupole (RFQ) injector linac, a pulsed kicker to select the desired proton bunches, and a DWA linear accelerator incorporating a high gradient insulator (HGI) with stacked Blumleins to produce the required acceleration energy. The Blumleins are switched with solid state laser-driven optical switches integrated into the Blumlein assemblies. Other subsystems include a high power pulsed laser, fiber optic distribution system, electrical charging system, and beam diagnostics. An engineering prototype has been constructed and characterized, and these results will be used within the next three years to develop an extremely compact 150 MeV system capable of modulating energy, beam current, and spot size on a shot-to-shot basis. This paper presents the details the engineering prototype, experimental results, and commercialization plans.

  6. Compact Spreader Schemes

    SciTech Connect

    Placidi, M.; Jung, J. -Y.; Ratti, A.; Sun, C.

    2014-07-25

    This paper describes beam distribution schemes adopting a novel implementation based on low amplitude vertical deflections combined with horizontal ones generated by Lambertson-type septum magnets. This scheme offers substantial compactness in the longitudinal layouts of the beam lines and increased flexibility for beam delivery of multiple beam lines on a shot-to-shot basis. Fast kickers (FK) or transverse electric field RF Deflectors (RFD) provide the low amplitude deflections. Initially proposed at the Stanford Linear Accelerator Center (SLAC) as tools for beam diagnostics and more recently adopted for multiline beam pattern schemes, RFDs offer repetition capabilities and a likely better amplitude reproducibility when compared to FKs, which, in turn, offer more modest financial involvements both in construction and operation. Both solutions represent an ideal approach for the design of compact beam distribution systems resulting in space and cost savings while preserving flexibility and beam quality.

  7. Compact waveguide splitter networks.

    PubMed

    Qian, Yusheng; Song, Jiguo; Kim, Seunghyun; Hu, Weisheng; Nordin, Gregory P

    2008-03-31

    We demonstrate compact waveguide splitter networks in siliconon- insulator (SOI) rib waveguides using trench-based splitters (TBSs) and bends (TBBs). Rather than a 90 degrees geometry, we use 105 degrees TBSs to facilitate reliable fabrication of high aspect ratio trenches suitable for 50/50 splitting when filled with SU8. Three dimensional (3D) finite difference time domain (FDTD) simulation is used for splitter and bend design. Measured TBB and TBS optical efficiencies are 84% and 68%, respectively. Compact 105 degrees 1 x 4, 1 x 8, and 1 x 32 trench-based splitter networks (TBSNs) are demonstrated. The measured total optical loss of the 1 x 32 TBSN is 9.15 dB. Its size is only 700 microm x 1600 microm for an output waveguide spacing of 50 microm. PMID:18542598

  8. Discovery of Carbon Radio Recombination Lines in M82

    NASA Astrophysics Data System (ADS)

    Morabito, Leah K.; Oonk, J. B. R.; Salgado, Francisco; Toribio, M. Carmen; Tielens, Xander; Röttgering, Huub

    2015-02-01

    Cold, diffuse HI clouds are a key component of the interstellar medium (ISM), and play an important role in the evolution of galaxies. Carbon radio recombination lines (CRRLs) trace this ISM stage, and with the enormous sensitivity of LOFAR we have already begun to map and constrain the physical properties of this gas in our own Galaxy. Using LOFAR's low band antenna, we have observed M 82 and present the first ever extragalactic detection of CRRLs. We stack 22 lines to find a 8.5-sigma detection. The line peak to continuum ratio is ~0.003, with a FWHM of 31 km s-1. The CRRL feature is consistent with an origin in the cold, neutral medium in the direction of the nucleus of M 82.

  9. Interstellar Scintillation and the Radio Counterpart of the Fast Radio Burst FRB 150418

    NASA Astrophysics Data System (ADS)

    Akiyama, Kazunori; Johnson, Michael D.

    2016-06-01

    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 μJy to 100 μJy 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 & 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 ≳ 109 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. Interstellar Scintillation and the Radio Counterpart of the Fast Radio Burst FRB 150418

    NASA Astrophysics Data System (ADS)

    Akiyama, Kazunori; Johnson, Michael D.

    2016-06-01

    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 μJy to 100 μJy 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 & 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 ≳ 109 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.

  11. Compact power reactor

    DOEpatents

    Wetch, Joseph R.; Dieckamp, Herman M.; Wilson, Lewis A.

    1978-01-01

    There is disclosed a small compact nuclear reactor operating in the epithermal neutron energy range for supplying power at remote locations, as for a satellite. The core contains fuel moderator elements of Zr hydride with 7 w/o of 93% enriched uranium alloy. The core has a radial beryllium reflector and is cooled by liquid metal coolant such as NaK. The reactor is controlled and shut down by moving portions of the reflector.

  12. Compact heat exchangers

    SciTech Connect

    Kays, W.M.; London, A.L.

    1984-01-01

    This third edition is an update of the second edition published in 1964. New data and more modern theoretical solutions for flow in the simple geometries are included, although this edition does not differ radically from the second edition. It contains basic test data for eleven new surface configurations, including some of the very compact ceramic matrices. Al dimensions are given in both the English and the Systeme International (SI) system of units.

  13. Compact infrared detector

    NASA Technical Reports Server (NTRS)

    Gupta, A.; Hong, S.; Moacanin, J.

    1981-01-01

    Broadband IR detector integrated into compact package for pollution monitoring and weather prediction is small, highly responsive, and immune to high noise. Sensing material is transparent sheet metalized with reflecting coating and overcoated with black material on same side. Pulse produced by chopping of infrared source beam creates transient "thermal lens" that temporarily defocuses laser beam probe. Detector monitoring beam measures defocusing which parallels infrared intensity.

  14. Granule consolidation during compaction.

    PubMed

    Rubinstein, M H

    1976-03-01

    The deformation of small cylindrical aggregates of dibasic calcium phosphate was measured during compaction. An analogy between these aggregates and cylindrical granules was proposed. No change in the original shape of the aggregates occurred; the cylindrical shape was maintained even at high compaction pressures. Relaxation of the aggregates occurred at pressures higher than 420 MNm-2 (60.9 x 10(3) lb in.-2) when removed from the compacts, but no relaxation took place at pressures below this value. In addition, the aggregates relaxed by an increase in thickness only; there was no corresponding change in diameter. Up to a pressure of 200 MNm-2 (29.0 x 10(3) lb in.-2), an increase in aggregate diameter occurred, which was accompanied by a reduction in thickness. This change produced only a small reduction in volume, which was attributable to interparticulate slippage resulting in a closer packed arrangement. At a pressure of 200 MNm-2, the aggregate diameter no longer increased because solid bridges were formed between the particles and the die wall, preventing further spreading. From 200 to 420 MNm-2, failure of the material occurred by plastic deformation, which produced only a decrease in aggregate thickness. From 420 to 800 MNm-2 (116.0 x 10(3) lb in.-2), a structure was formed that could support the applied load without further reduction of thickness, and this structure was shown to behave elastically. PMID:1263085

  15. Survey for Radio Nebulae Around Ultraluminous X-ray Sources

    NASA Astrophysics Data System (ADS)

    Miller, Neal A.; Heil, Martha Nicole; Mushotzky, Richard

    2016-01-01

    The nature of ultraluminous X-ray sources (ULX) is an ongoing debate. As such sources appear to violate the Eddington Limit for the expected masses of stellar remnants, ULX may represent a class of super-Eddington objects, "intermediate" mass black holes (IMBH) emitting at sub-Eddington levels, or a diverse population including examples of both. Most initial efforts to search for radio emission associated with ULX did so with high angular resolution in hopes of applying the "fundamental plane of black hole activity" which relates X-ray luminosity, radio luminosity, and black hole mass. The predicted radio flux densities for such compact radio emission are quite low meaning that even non-detections leave open much of the mass range associated with IMBH. However, a small number of ULX have been associated with extended radio emission and these radio nebulae have sizes and energetics that differentiate them from more common classes of extended objects such as HII regions and supernova remnants. We report here on the results of a cohesive study to identify and characterize ULX radio nebula associated with unbiased samples of ULX. This study has two prongs: one relying upon archival Very Large Array data and one using new, dedicated Jansky Very Large Array observations. Several new candidate ULX radio nebulae are identified and characterized, and along with limits from non-detections we discuss implications for the overall population of ULX.

  16. Photon mass limits from fast radio bursts

    NASA Astrophysics Data System (ADS)

    Bonetti, Luca; Ellis, John; Mavromatos, Nikolaos E.; Sakharov, Alexander S.; Sarkisyan-Grinbaum, Edward K.; Spallicci, Alessandro D. A. M.

    2016-06-01

    The frequency-dependent time delays in fast radio bursts (FRBs) can be used to constrain the photon mass, if the FRB redshifts are known, but the similarity between the frequency dependences of dispersion due to plasma effects and a photon mass complicates the derivation of a limit on mγ. The dispersion measure (DM) of FRB 150418 is known to ∼ 0.1%, and there is a claim to have measured its redshift with an accuracy of ∼ 2%, but the strength of the constraint on mγ is limited by uncertainties in the modelling of the host galaxy and the Milky Way, as well as possible inhomogeneities in the intergalactic medium (IGM). Allowing for these uncertainties, the recent data on FRB 150418 indicate that mγ ≲ 1.8 ×10-14 eVc-2 (3.2 ×10-50 kg), if FRB 150418 indeed has a redshift z = 0.492 as initially reported. In the future, the different redshift dependences of the plasma and photon mass contributions to DM can be used to improve the sensitivity to mγ if more FRB redshifts are measured. For a fixed fractional uncertainty in the extra-galactic contribution to the DM of an FRB, one with a lower redshift would provide greater sensitivity to mγ.

  17. 3C 57 as an atypical radio-loud quasar: implications for the radio-loud/radio-quiet dichotomy

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Martínez-Carballo, M. A.; Marziani, P.; del Olmo, A.; Stirpe, G. M.; Zamfir, S.; Plauchu-Frayn, I.

    2015-06-01

    Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar `main sequence' with both extreme optical Fe II emission (R_{Fe II} ˜ 1) and a large C IV λ1549 profile blueshift (˜-1500 km s-1). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year time-scale consistent with compact steep-spectrum (or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/LEdd quasars, we suggest that 3C 57 is an evolved RL quasar (i.e. large blackhole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong Fe II emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low-redshift source and resultant unusually high Eddington ratio giving rise to the atypical C IV λ1549.

  18. Dichotomy in the population of young AGN: Optical, radio, and X-ray properties

    NASA Astrophysics Data System (ADS)

    Kunert-Bajraszewska, M.

    2016-02-01

    There are numerous examples of radio sources with various sizes which surprisingly exhibit very similar morphology. This observational fact helped to create a standard evolutionary model in which young and small radio-loud active galactic nuclei (AGN), called gigahertz-peaked spectrum (GPS) sources and compact steep spectrum (CSS) sources, become large-scale radio objects. However, many details of this evolutionary process are still unclear. We explored evolution scenarios of radio-loud AGN using new radio, optical and X-ray data of so far unstudied low luminosity compact (LLC) sources and we summarize the results in this paper. Our studies show that the evolutionary track is very ``individualized'' although we can mention common factors affecting it. These are interaction with the ambient medium and AGN power. The second feature affects the production of the radio jets which, if they are weak, are more vulnerable for instabilities and disruption. Thus not all GPS and CSS sources will be able to develop large scale morphologies. Many will fade away being middle-aged (105 yr). It seems that only radio strong, high excitation compact AGN can be progenitors of large-scale FR II radio sources.

  19. Stellar radio emission (Review)

    NASA Astrophysics Data System (ADS)

    Zhelezniakov, V. V.

    The current understanding of the radio-emission characteristics of 'ordinary' main sequence stars as well as giants and supergiants is examined. Particular consideration is given to radio emission from supergiants, Young T Tauri stars, magnetic Ap stars, flare stars of UV Ceti type, Alpha Sco, and RS CVn objects. It is noted that the study of stellar radio emission is in its initial stage. Further progress in this area depends on successes in finding new radio sources, associated, for example, with magnetic stars, and on an intensified investigation of the frequency spectra and polarization of already-discovered radio stars. It is also noted that, although the current knowledge of solar physics can help in understanding stellar radio emission, models and ideas developed for solar conditions should not be mechanically transferred to other stars by a simple change in scale.

  20. The TexOx-1000 redshift survey of radio sources I: the TOOT00 region

    NASA Astrophysics Data System (ADS)

    Vardoulaki, Eleni; Rawlings, Steve; Hill, Gary J.; Mauch, Tom; Inskip, Katherine J.; Riley, Julia; Brand, Kate; Croft, Steve; Willott, Chris J.

    2010-01-01

    We present optical spectroscopy, near-infrared (mostly K-band) and radio (151-MHz and 1.4-GHz) imaging of the first complete region (TOOT00) of the TexOx-1000 (TOOT) redshift survey of radio sources. The 0.0015-sr (~5 deg2) TOOT00 region is selected from pointed observations of the Cambridge Low-Frequency Survey Telescope at 151 MHz at a flux density limit of ~=100 mJy, approximately five times fainter than the 7C Redshift Survey (7CRS), and contains 47 radio sources. We have obtained 40 spectroscopic redshifts (~85 per cent completeness). Adding redshifts estimated for the seven other cases yields a median redshift zmed ~ 1.25. We find a significant population of objects with Fanaroff-Riley type I (FRI) like radio structures at radio luminosities above both the low-redshift FRI/II break and the break in the radio luminosity function. The redshift distribution and subpopulations of TOOT00 are broadly consistent with extrapolations from the 7CRS/6CE/3CRR data sets underlying the SKADS Simulated Skies Semi-Empirical Extragalactic Data base, S3-SEX.