18,091 research outputs found
Faraday rotation variations along radio jets: the magnetic field in galaxy and group halos
Our modelling of FR I radio jets as decelerating, relativistic flows allows
us to derive their orientations accurately. We present images of Faraday
rotation for two of these these objects (3C 31 and NGC 315) and show that the
fluctuations of rotation measure (RM) are larger in the fainter (receding)
jets, as expected if the rotation occurs in the hot galaxy/group halos. The gas
density is much lower in NGC 315 and the RM fluctuations are only just
detectable.Comment: 3 pages, 2 figures, requires an.cls. To appear in the Proceedings of
the International Conference: "The Origin and Evolution of Cosmic Magnetism";
Bologna 29 August - 2 September 2005; eds R. Beck, G. Brunetti, L. Feretti,
and B. Gaensler (Astronomische Nachrichten, 2006
Relativistic jet models for two low-luminosity radio galaxies: evidence for backflow?
We show that asymmetries in total intensity and linear polarization between
the radio jets and counter-jets in two lobed Fanaroff-Riley Class I (FR I)
radio galaxies, B2 0206+35 (UGC 1651) and B2 0755+37 (NGC 2484), can be
accounted for if these jets are intrinsically symmetrical, with decelerating
relativistic outflows surrounded by mildly relativistic backflows. Our
interpretation is motivated by sensitive, well-resolved Very Large Array
imaging which shows that both jets in both sources have a two-component
structure transverse to their axes. Close to the jet axis, a centrally-darkened
counter-jet lies opposite a centrally-brightened jet, but both are surrounded
by broader collimated emission that is brighter on the counter-jet side. We
have adapted our previous models of FR I jets as relativistic outflows to
include an added component of symmetric backflow. We find that the observed
radio emission, after subtracting contributions from the extended lobes, is
well described by models in which decelerating outflows with parameters similar
to those derived for jets in plumed FR I sources are surrounded by backflows
containing predominantly toroidal magnetic fields. These return to within a few
kpc of the galaxies with velocities of roughly 0.25c and radiate with a
synchrotron spectral index close to 0.55. We discuss whether such backflow is
to be expected in lobed FR I sources and suggest ways in which our hypothesis
can be tested by further observations.Comment: 22 pages, 17 figures, accepted for publication in MNRA
Adiabatic relativistic models for the jets in the radio galaxy 3C 31
We present a general approach to the modelling of the brightness and
polarization structures of adiabatic, decelerating relativistic jets, based on
the formalism of Matthews & Scheuer (1990). We compare the predictions of
adiabatic jet models with deep, high-resolution observations of the radio jets
in the FR I radio galaxy 3C 31. Adiabatic models require coupling between the
variations of velocity, magnetic field and particle density. They are therefore
more tightly constrained than the models previously presented for 3C 31 by
Laing & Bridle (2002). We show that adiabatic models provide a poorer
description of the data in two crucial respects: they cannot reproduce the
observed magnetic-field structures in detail, and they also predict too steep a
brightness decline along the jets for plausible variations of the jet velocity.
We find that the innermost regions of the jets show the strongest evidence for
non-adiabatic behaviour, and that the adiabatic models provide progressively
better descriptions of the jet emission at larger distances from the galactic
nucleus. We briefly discuss physical processes which might contribute to this
non-adiabatic behaviour. In particular, we develop a parameterized description
of distributed particle injection, which we fit to the observed total
intensities. We show that particles are preferentially injected where bright
X-ray emission is observed, and where we infer that the jets are
over-pressured.Comment: 16 pages, 11 figures, accepted for publication in MNRA
'The world is full of big bad wolves': investigating the experimental therapeutic spaces of R.D. Laing and Aaron Esterson
In conjunction with the recent critical assessments of the life and work of R.D. Laing, this paper seeks to demonstrate what is revealed when Laingâs work on families and created spaces of mental health care are examined through a geographical lens. The paper begins with an exploration of Laingâs time at the Tavistock Clinic in London during the 1960s, and of the co-authored text with Aaron Esterson entitled, Sanity, Madness and the Family (1964). The study then seeks to demonstrate the importance Laing and his colleague placed on the time-space situatedness of patients and their worlds. Finally, an account is provided of Laingâs and Estersonâs spatial thinking in relation to their creation of both real and imagined spaces of therapeutic care
Anglim\u27s Encyclopedia of religion and the law in America, 2nd ed. (Book Review)
A review of Anglim, C.T. (2009). Encyclopedia of religion and the law in America, 2nd ed. Amenia, NY: Grey House Publishing. 847 pp. $165.00. ISBN 978159237298
- âŠ