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5 results on '"M. Birkinshaw"'

1. Compact Symmetric Objects. III. Evolution of the High-luminosity Branch and a Possible Connection with Tidal Disruption Events

Author

A. C. S Readhead, V. Ravi, R. D. Blandford, A. G. Sullivan, J. Somalwar, M. C. Begelman, M. Birkinshaw, I. Liodakis, M. L. Lister, T. J. Pearson, G. B. Taylor, P. N. Wilkinson, N. Globus, S. Kiehlmann, C. R. Lawrence, D. Murphy, S. O’Neill, V. Pavlidou, E. Sheldahl, A. Siemiginowska, and K. Tassis

Subjects
Active galactic nuclei, Active galaxies, Relativistic jets, Tidal disruption, Astrophysics, QB460-466
Abstract

We use a sample of 54 compact symmetric objects (CSOs) to confirm that there are two unrelated CSO classes: an edge-dimmed, low-luminosity class (CSO 1), and an edge-brightened, high-luminosity class (CSO 2). Using blind tests, we show that CSO 2s consist of three subclasses: CSO 2.0, having prominent hot spots at the leading edges of narrow jets and/or narrow lobes; CSO 2.2, without prominent hot spots and with broad jets and/or lobes; and CSO 2.1, which exhibit mixed properties. Most CSO 2s do not evolve into larger jetted active galactic nuclei (AGN), but spend their whole life cycle as CSOs of size ≲500 pc and age ≲5000 yr. The minimum energies needed to produce the radio luminosity and structure in CSO 2s range from ∼10 ^−4 M _⊙ c ^2 to ∼7 M _⊙ c ^2 . We show that the transient nature of most CSO 2s, and their birth rate, can be explained through ignition in the tidal disruption events of stars. We also consider possibilities of tapping the spin energy of the supermassive black hole, and tapping the energy of the accretion disk. Our results demonstrate that CSOs constitute a large family of AGN in which we have thus far studied only the brightest. More comprehensive CSO studies, with higher sensitivity, resolution, and dynamic range, will revolutionize our understanding of AGN and the central engines that power them.

Published
2024
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3. PERIODIC STRUCTURE IN THE MEGAPARSEC-SCALE JET OF PKS 0637–752

Author

L. E. H. Godfrey, J. E. J. Lovell, S. Burke-Spolaor, R. Ekers, G. V. Bicknell, M. Birkinshaw, D. M. Worrall, D. L. Jauncey, D. A. Schwartz, H. L. Marshall, J. Gelbord, E. S. Perlman, and M. Georganopoulos

Subjects
Physics, Angular distance, Astrophysics::High Energy Astrophysical Phenomena, Cosmic microwave background, Astronomy and Astrophysics, Quasar, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Plasma, Kinetic energy, Jet engine, law.invention, Knot (unit), Binary black hole, Space and Planetary Science, law, High Energy Physics::Experiment, Astrophysics::Galaxy Astrophysics
Abstract

We present 18 GHz Australia Telescope Compact Array imaging of the Mpc-scale quasar jet PKS 0637-752 with angular resolution ~0.58 arcseconds. We draw attention to a spectacular train of quasi-periodic knots along the inner 11 arcseconds of the jet, with average separation ~1.1 arcsec (7.6 kpc projected). We consider two classes of model to explain the periodic knots: those that involve a static pattern through which the jet plasma travels (e.g. stationary shocks); and those that involve modulation of the jet engine. Interpreting the knots as re-confinement shocks implies the jet kinetic power Q ~ 10^{46} erg/s, but the constant knot separation along the jet is not expected in a realistic external density profile. For models involving modulation of the jet engine, we find that the required modulation period is 2 x 10^3 yr < \tau < 3 x 10^5 yr. The lower end of this range is applicable if the jet remains highly relativistic on kpc-scales, as implied by the IC/CMB model of jet X-ray emission. We suggest that the quasi-periodic jet structure in PKS 0637-752 may be analogous to the quasi-periodic jet modulation seen in the microquasar GRS 1915+105, believed to result from limit cycle behaviour in an unstable accretion disk. If variations in the accretion rate are driven by a binary black hole, the predicted orbital radius is 0.7 < a < 30 pc, which corresponds to a maximum angular separation of ~0.1 - 5 mas.

Published
2012

5. Hot spots in Cygnus A at 89 GHz

Author

Melvyn Wright and M. Birkinshaw

Subjects
Physics, Space and Planetary Science, Radio galaxy, Linear polarization, Astronomy, Astronomy and Astrophysics, Hot spot (veterinary medicine), Astrophysics, Cygnus A
Abstract

On a utilise l'interferometre de Hat Creek a 89 GHz pour cartographier la radiosource Cyg A avec une resolution de 1,5''×2,8''. Les points chauds dans les lobes radio ont des spectres d'indice spectral 0,98±0,02, plus plats que l'emission des lobes de 1,34±0,05. La composante centrale a une densite de flux de 0,7±0,07 Jy. On n'a pas observe de variabilite a 89 GHz par la composante centrale au cours des 10 mois d'observation

Published
1984

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