Browsing FAS Scholarly Articles by Keyword "galaxies: jets"

Now showing items 1-15 of 15

    • 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 ...

    • Black Hole Spin and the Radio Loud/Quiet Dichotomy of Active Galactic Nuclei 

      Tchekhovskoy, Alexander; Narayan, Ramesh; McKinney, Jonathan C. (IOP Publishing, 2010)
      Radio loud active galactic nuclei (AGNs) are on average 1000 times brighter in the radio band compared to radio quiet AGNs. We investigate whether this radio loud/quiet dichotomy can be due to differences in the spin of ...

    • Bondi Flow from a Slowly Rotating Hot Atmosphere 

      Narayan, Ramesh; Fabian, Andrew C. (Oxford University Press (OUP), 2011)
      A supermassive black hole in the nucleus of an elliptical galaxy at the centre of a cool-core group or cluster of galaxies is immersed in hot gas. Bondi accretion should occur at a rate determined by the properties of the ...

    • A Chandra Observation of 3C 288—Reheating ohe Cool Core of a 3 Kev Cluster from a Nuclear Outburst at Z = 0.246 

      Lal, D. V.; Kraft, Ralph P.; Forman, William R.; Hardcastle, M. J.; Jones, C.; Nulsen, Paul; Evans, D. A.; Croston, J. H.; Lee, Julia C (IOP Publishing, 2010)
      We present results from a 42 ks Chandra/ACIS-S observation of the transitional FR I/FR II radio galaxy 3C 288 at z = 0.246. We detect ~3 keV gas extending to a radius of ~0.5 Mpc with a 0.5-2.0 keV luminosity of 6.6 × 1043 ...

    • Efficiency of Magnetic to Kinetic Energy Conversion in a Monopole Magnetosphere 

      Tchekhovskoy, Alexander; McKinney, Jonathan C.; Narayan, Ramesh (IOP Publishing, 2009)
      Unconfined relativistic outflows from rotating, magnetized compact objects are often well modeled by assuming that the field geometry is approximately a split-monopole at large radii. Earlier work has indicated that such ...

    • Efficient generation of jets from magnetically arrested accretion on a rapidly spinning black hole 

      Tchekhovskoy, Alexander; Narayan, Ramesh; McKinney, Jonathan C. (Oxford University Press (OUP), 2011)
      We describe global, 3D, time‐dependent, non‐radiative, general‐relativistic, magnetohydrodynamic simulations of accreting black holes (BHs). The simulations are designed to transport a large amount of magnetic flux to the ...

    • 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, ...

    • Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a mean-field magnetic dynamo 

      Sadowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Abarca, David; Zhu, Yucong; McKinney, Jonathan C. (Oxford University Press (OUP), 2014)
      We present a sub-grid model that emulates the magnetic dynamo operating in magnetized accretion disks. We have implemented this model in the general relativisic radiation magnetohydrodynamic (GRRMHD) code KORAL, using ...

    • Numerical Simulation of Hot Accretion Flows. III. Revisiting Wind Properties Using the Trajectory Approach 

      Yuan, Feng; Gan, Zhaoming; Narayan, Ramesh; Sadowski, Aleksander; Bu, Defu; Bai, Xue-Ning (IOP Publishing, 2015)
      Previous MHD simulations have shown that wind must exist in black hole hot accretion flows. In this paper, we continue our study by investigating the detailed properties of wind and the mechanism of wind production. For ...

    • Numerical simulations of super-critical black hole accretion flows in general relativity 

      Sadowski, A.; Narayan, Ramesh; McKinney, J. C.; Tchekhovskoy, A. (Oxford University Press (OUP), 2014)
      A new general relativistic radiation magnetohydrodynamical code KORAL is described, which employs the M1 scheme to close the radiation moment equations. The code has been successfully verified against a number of tests. ...

    • Powerful radiative jets in supercritical accretion discs around non-spinning black holes 

      Sadowski, Aleksander; Narayan, Ramesh (Oxford University Press (OUP), 2015)
      We describe a set of simulations of super-critical accretion onto a non-rotating supermassive BH. The accretion flow is radiation pressure dominated and takes the form of a geometrically thick disk with twin low-density ...

    • 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 ...

    • Simulations of ultrarelativistic magnetodynamic jets from gamma-ray burst engines 

      Tchekhovskoy, Alexander; McKinney, Jonathan C.; Narayan, Ramesh (Oxford University Press (OUP), 2008)
      Long-duration gamma-ray bursts (GRBs) require an engine capable of driving a jet of plasma to ultrarelativistic bulk Lorentz factors of up to several hundred and into narrow opening angles of a few degrees. We use global ...

    • Stability of Relativistic Force-Free Jets 

      Narayan, Ramesh; Li, Jason; Tchekhovskoy, Alexander (IOP Publishing, 2009)
      We consider a two-parameter family of cylindrical force-free equilibria, modeled to match numerical simulations of relativistic force-free jets. We study the linear stability of these equilibria, assuming a rigid impenetrable ...

    • Tidal disruption and magnetic flux capture: powering a jet from a quiescent black hole 

      Kelley, L. Z.; Tchekhovskoy, A.; Narayan, Ramesh (Oxford University Press (OUP), 2014)
      The transient Swift J1644+57 is believed to have been produced by an unlucky star wandering too close to a supermassive black hole (BH) leading to a tidal disruption event. This unusual flare displayed highly super-Eddington ...