Now showing items 1-20 of 29

    • 230 GHz VLBI observations of M87: event-horizon-scale structure at the enhanced very-high-energy γ-ray state in 2012 

      Akiyama, Kazunori; Lu, Ru-Sen; Fish, Vincent; Doeleman, Sheperd S.; Broderick, Avery; Dexter, Jason; Hada, Kazuhiro; Kino, Motoki; Nagai, Hiroshi; Honma, Mareki; Johnson, Michael D.; Algaba, Juan; Asada, Keiichi; Brinkerink, Christiaan; Blundell, Raymond; Bower, Geoffrey; Cappallo, Roger; Crew, Geoffrey; Dexter, Matt; Dzib, Sergio; Freund, Robert; Friberg, Per; Gurwell, Mark Andrew; Ho, Paul; Inoue, Makoto; Krichbaum, Thomas; Loinard, Laurent; MacMahon, David; Marrone, Daniel; Moran, James M.; Nakamura, Masanori; Nagar, Neil; Ortiz-Leon, Gisela; Plambeck, Richard; Pradel, Nicolas; Primiani, Rurik A.; Rogers, Alan; Roy, Alan; SooHoo, Jason; Tavares, Jonathan-León; Tilanus, Remo; Titus, Michael; Wagner, Jan; Weintroub, Jonathan; Yamaguchi, Paul Isami; Young, Ken Harbour; Zensus, Anton; Ziurys, Lucy (IOP Publishing, 2015)
      We report on 230 GHz (1.3 mm) VLBI observations of M87 with the Event Horizon Telescope using antennas on Mauna Kea in Hawaii, Mt. Graham in Arizona and Cedar Flat in California. For the first time, we have acquired 230 ...
    • The Cambridge-Cambridge ROSAT Serendipity Survey - III. VLA observations and the evolution of radio-quiet and radio-loud objects 

      Ciliegi, P.; Elvis, Martin S.; Wilkes, Belinda Jane; Boyle, B. J.; McMahon, R. G.; Maccacaro, T. (Oxford University Press (OUP), 1995)
      We present the results of the VLA radio observations at 1.475 GHz (20 cm) of the active galactic nuclei (AGN) in the Cambridge-Cambridge ROSAT Serendipity Survey (CRSS), a sample of 123 faint X-ray sources with ...
    • Discovery of Candidate H2O Disk Masers in Active Galactic Nuclei and Estimations of Centripetal Accelerations 

      Greenhill, Lincoln Jared; Kondratko, Paul T.; Moran, James M.; Tilak, Avanti (IOP Publishing, 2009)
      Based on spectroscopic signatures, about one-third of known H2O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These “disk maser candidates” ...
    • The Discovery of H2O Maser Emission in Seven AGN and at High Velocities in the Circinus Galaxy 

      Greenhill, Lincoln Jared; Kondratko, P. T.; Lovell, J. E. J.; Kuiper, T. B. H.; Moran, James M.; Jauncey, D. L.; Baines, G. P. (IOP Publishing, 2002)
      We report the discovery of H2O maser emission at 1.35 cm wavelength in seven active galactic nuclei (at distances up to < 80 Mpc) during a survey conducted at the 70-m diameter antenna of the NASA Deep Space Network near ...
    • Discovery of Water Maser Emission in Eight AGNs with 70 m Antennas of NASA’s Deep Space Network 

      Kondratko, P. T.; Greenhill, Lincoln Jared; Moran, James M.; Lovell, J. E. J.; Kuiper, T. B. H.; Jauncey, D. L.; Cameron, L. B.; Gomez, J. F.; Garcia‐Miro, C.; Moll, E.; de Gregorio‐Monsalvo, I.; Jimenez‐Bailon, E. (IOP Publishing, 2006)
      We report the discovery of water maser emission in eight active galactic nuclei (AGN) with the 70-m NASA Deep Space Network (DSN) antennas at Tidbinbilla, Australia and Robledo, Spain. The positions of the newly discovered ...
    • Discovery of Water Maser Emission in Five AGNs and a Possible Correlation Between Water Maser and Nuclear 2–10 keV Luminosities 

      Kondratko, Paul T.; Greenhill, Lincoln Jared; Moran, James M. (IOP Publishing, 2006)
      We report the discovery of water maser emission in five active galactic nuclei (AGN) with the 100-m Green Bank Telescope (GBT). The positions of the newly discovered masers, measured with the VLA, are consistent with the ...
    • Double-peaked narrow-line signatures of dual supermassive black holes in galaxy merger simulations 

      Blecha, L.; Loeb, A.; Narayan, Ramesh (Oxford University Press (OUP), 2013)
      We present a first attempt to model the narrow-line (NL) region of active galactic nuclei (AGN) in hydrodynamic simulations of galaxy mergers, using a novel physical prescription. This model is used to determine the origin ...
    • Evidence for a Geometrically Thick Self‐Gravitating Accretion Disk in NGC 3079 

      Kondratko, Paul T.; Greenhill, Lincoln Jared; Moran, James M. (IOP Publishing, 2005)
      We have mapped, for the first time, the full velocity extent of the water maser emission in NGC 3079. The largely north-south distribution of emission, aligned with a kpc-scale molecular disk, and the segregation of blue- ...
    • Fine-Scale Structure of the Quasar 3C 279 Measured with 1.3 mm Very Long Baseline Interferometry 

      Lu, Ru-Sen; Fish, Vincent L.; Akiyama, Kazunori; Doeleman, Sheperd S.; Algaba, Juan C.; Bower, Geoffrey C.; Brinkerink, Christiaan; Chamberlin, Richard; Crew, Geoffrey; Cappallo, Roger J.; Dexter, Matt; Freund, Robert; Friberg, Per; Gurwell, Mark Andrew; Ho, Paul T. P.; Honma, Mareki; Inoue, Makoto; Jorstad, Svetlana G.; Krichbaum, Thomas P.; Loinard, Laurent; MacMahon, David; Marrone, Daniel P.; Marscher, Alan P.; Moran, James M.; Plambeck, Richard; Pradel, Nicolas; Primiani, Rurik A.; Tilanus, Remo P. J.; Titus, Michael; Weintroub, Jonathan; Wright, Melvyn; Young, Ken Harbour; Ziurys, Lucy M. (American Astronomical Society, 2013)
      We report results from five day very long baseline interferometry observations of the well-known quasar 3C 279 at 1.3mm (230 GHz) in 2011. The measured nonzero closure phases on triangles including stations in Arizona, ...
    • First Detection of Millimeter/Submillimeter Extragalactic H2O Maser Emission 

      Humphreys, E. M. L.; Greenhill, L. J.; Reid, M. J.; Beuther, H.; Moran, James M.; Gurwell, Mark Andrew; Wilner, David J.; Kondratko, P. T. (IOP Publishing, 2005)
      We report the first detection of an extragalactic millimeter wavelength H2O maser at 183 GHz towards NGC 3079 using the Submillimeter Array (SMA), and a tentative submillimeter wave detection of the 439 GHz maser towards ...
    • The Geometry of and Mass Accretion Rate through the Maser Accretion Disk in NGC 4258 

      Herrnstein, J. R.; Moran, James M.; Greenhill, Lincoln Jared; Trotter, Adam S. (IOP Publishing, 2005)
      A maximum likelihood analysis of the NGC 4258 maser positions and velocities reveals a ∼ 2 σ deviation from Keplerian motion in the projected rotation curve of the high-velocity features, corresponding to a ∼ 9 km s−1, or ...
    • Giant gamma-ray bubbles from Fermi-LAT: active galactic nucleus activity or bipolar galactic wind? 

      Su, Meng; Slatyer, Tracy R.; Finkbeiner, Douglas (IOP Publishing, 2010)
      Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50° above and below the Galactic center (GC), with a width of about 40° in longitude. The gamma-ray emission associated with these bubbles has a ...
    • A Green Bank Telescope Search for Water Masers in Nearby Active Galactic Nuclei 

      Braatz, J. A.; Henkel, C.; Greenhill, Lincoln Jared; Moran, James M.; Wilson, A. S. (IOP Publishing, 2004)
      Using the Green Bank Telescope, we have conducted a survey for 1.3 cm water maser emission toward the nuclei of nearby active galaxies, the most sensitive large survey for H2O masers to date. Among 145 galaxies observed, ...
    • Host Galaxies, Clustering, Eddington Ratios, and Evolution of Radio, X-Ray, and Infrared-selected AGNs. 

      Hickox, Ryan C.; Jones, Christine; Forman, William R.; Murray, Stephen; Kochanek, Christopher S.; Eisenstein, Daniel; Jannuzi, Buell T.; Dey, Arjun; Brown, Michael J. I.; Stern, Daniel; Eisenhardt, Peter R.; Gorjian, Varoujan; Brodwin, Mark; Narayan, Ramesh; Cool, Richard J.; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E. (IOP Publishing, 2009)
      We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the ...
    • No Precise Localization for Frb 150418: Claimed Radio Transient Is Agn Variability 

      Williams, Peter Kelsey George; Berger, Edo (American Astronomical Society, 2016)
      Keane et al. have recently claimed to have obtained the first precise localization for a Fast Radio Burst (FRB) thanks to the identification of a contemporaneous fading slow (∼week-timescale) radio transient. They use this ...
    • Optical and Radio Properties of Extragalactic Sources Observed by the FIRST Survey and the Sloan Digital Sky Survey 

      Ivezić, Željko; Menou, Kristen; Knapp, Gillian R.; Strauss, Michael A.; Lupton, Robert H.; Vanden Berk, Daniel E.; Richards, Gordon T.; Tremonti, Christy; Weinstein, Michael A.; Anderson, Scott; Bahcall, Neta A.; Becker, Robert H.; Bernardi, Mariangela; Blanton, Michael; Eisenstein, Daniel; Fan, Xiaohui; Finkbeiner, Douglas; Finlator, Kristian; Frieman, Joshua; Gunn, James E.; Hall, Pat B.; Kim, Rita S. J.; Kinkhabwala, Ali; Narayanan, Vijay K.; Rockosi, Constance M.; Schlegel, David; Schneider, Donald P.; Strateva, Iskra; SubbaRao, Mark; Thakar, Aniruddha R.; Voges, Wolfgang; White, Richard L.; Yanny, Brian; Brinkmann, Jonathan; Doi, Mamoru; Fukugita, Masataka; Hennessy, Gregory S.; Munn, Jeffrey A.; Nichol, Robert C.; York, Donald G. (IOP Publishing, 2002)
      We discuss the optical and radio properties of ~30,000 FIRST (radio, 20 cm, sensitive to 1 mJy) sources positionally associated within 1farcs5 with a Sloan Digital Sky Survey (SDSS) (optical, sensitive to r* ~ 22.2) source ...
    • Optical spectroscopic observations of gamma-ray blazars candidates I: preliminary results 

      Paggi, A.; Milisavljevic, Danny; Masetti, N.; Jiménez-Bailón, E.; Chavushyan, V.; Massaro, F.; Giroletti, M.; Smith, Howard A.; Margutti, R.; Tosti, G.; Martínez-Galarza, J. R.; Otí-Floranes, H.; Landoni, M.; Grindlay, Jonathan E.; Funk, S. (IOP Publishing, 2014)
      A significant fraction (~30%) of the γ-ray sources listed in the second Fermi/LAT (2FGL) catalog is still of unknown origin, being not yet associated with counterparts at lower energies. Using the available information at ...
    • Panchromatic properties of 99 000 galaxies detected by SDSS, and (some by) ROSAT, GALEX, 2MASS, IRAS, GB6, FIRST, NVSS and WENSS surveys 

      Obrić, M.; Ivezić, Ž; Best, P. N.; Lupton, R. H.; Tremonti, C.; Brinchmann, J.; Agüeros, M. A.; Knapp, G. R.; Gunn, J. E.; Rockosi, C. M.; Schlegel, D.; Finkbeiner, Douglas; Gaćeša, M.; Smolčić, V.; Anderson, S. F.; Voges, W.; Jurić, M.; Siverd, R. J.; Steinhardt, W.; Jagoda, A. S.; Blanton, M. R.; Schneider, D. P. (Oxford University Press (OUP), 2006)
      We discuss the panchromatic properties of 99 088 galaxies selected from the Sloan Digital Sky Survey (SDSS) Data Release 1 ‘main’ spectroscopic sample (a flux-limited sample for 1360 deg2). These galaxies are positionally ...
    • Radio and Millimeter Monitoring of Sgr A*: Spectrum, Variability, and Constraints on the G2 Encounter 

      Bower, Geoffrey C.; Markoff, Sera; Dexter, Jason; Gurwell, Mark Andrew; Moran, James M.; Brunthaler, Andreas; Falcke, Heino; Fragile, P. Chris; Maitra, Dipankar; Marrone, Dan; Peck, Alison; Rushton, Anthony; Wright, Melvyn C. H. (IOP Publishing, 2015)
      We report new observations with the Very Large Array, Atacama Large Millimeter Array, and Submillimeter Array at frequencies from 1.0 to 355 GHz of the Galactic Center black hole, Sagittarius A*. These observations were ...
    • Recoiling black holes: prospects for detection and implications of spin alignment 

      Blecha, Laura; Sijacki, Debora; Kelley, Luke Zoltan; Torrey, Paul; Vogelsberger, Mark; Nelson, Dylan; Springel, Volker; Snyder, Gregory; Hernquist, Lars Eric (Oxford University Press (OUP), 2015)
      Supermassive black hole (BH) mergers produce powerful gravitational wave emission. Asymmetry in this emission imparts a recoil kick to the merged BH, which can eject the BH from its host galaxy altogether. Recoiling BHs ...