These animations show how the appearance of the twin relativistic jets in the FR-I
radio galaxy 3C31 would change when the jets are observed at different angles to the
line of sight by a radio telescope with
(a) constant (5000:1) dynamic range and
(b)
constant sensitivity.
The relativistic jet model used to generate these displays is the best fit
to 8 GHz VLA data for 3C31 at 0.25 arcsec resolution by R.A.Laing and A.H.Bridle
(2002: MNRAS, 336, 328).
This best fit occurs for an angle of 52 degrees between the jet and the line of sight.
The inner region contains a jet with fast (0.8 -- 0.9c) outflow on the
axis and much slower flow at its edge. A discontinuity in the flow then occurs at which
the jet flares and its emissivity increases suddenly. The on-axis velocity stays fairly
constant at approximately 0.8c until the end of the flaring region, where it
drops abruptly to approximately 0.55c. The velocity then slowly decreases to
approximately 0.25c at the end of the modelled region. Throughout the flaring
and outer regions, the velocity at the edge of the jet is approximately 0.7 of
its on-axis value. The magnetic field in the flaring region is complex,
with an essentially isotropic structure at the edge of the jet, but a more
ordered toroidal+longitudinal configuration on-axis. In the outer region,
the radial field vanishes and the toroidal component becomes dominant.
The discontinuity between the inner and flaring regions can be associated
with a stationary shock structure. The inferred transverse
velocity profiles and field structure in the flaring region support the
idea that the jets decelerate by entraining the external medium from the galactic
atmosphere of 3C31.
The "constant-sensitivity" displays show what would be seen by an ideal
radio telescope that could detect the faintest levels of emission equally no matter
how bright the compact central component becomes due to relativistic beaming.
The "constant-dynamic-range" displays correspond better to standard radio astronomical
observations that have not been specially optimized to detect the faintest broad features
in the presence of strong compact features..
The jets appear identical when observed in the plane of the sky (90 degrees
to the line of sight), as at the start of each animation.
The animations illustrate how, at angles closer to the line of sight,
Both sets of animations are shown using both "flame" and "rainbow" color
coded transfer functions, as at the top of the page.
Other 3C31 links