53,803 research outputs found
More Evidence for an Oscillation Superimposed on the Hubble Flow
In a recent investigation evidence was presented for a low-level sinusoidal
oscillation superimposed on top of the Hubble flow. This oscillation was in
V, in a sample of type Ia Supernovae sources with accurate distances,
and it was found to have a wavelength close to 40 Mpc. It became easily visible
after the removal of several previously identified discrete velocity
components. Its amplitude like that of the Hubble velocity showed an increase
with distance, as would be expected for a constant-amplitude space oscillation.
Here we report that this oscillation is also present in distance clumping in
these sources, with the same wavelength, but in phase quadrature. The discrete
velocity components do not play a role in detecting the distance clumping
wavelength. Assuming that time proceeds from high cosmological redshift to low,
the blue-shifted velocity peaks, which represent the contraction stage of the
velocity oscillation, then lead the density peaks. With the discrete velocity
components removed we also find evidence for at least one other, weaker
velocity oscillation. It is found to have a wavelength similar to one reported
in density clumping by previous investigators. In those cases the source
samples were much larger.Comment: 7 pages, with 6 figures, accepted for publication in Astrophysics and
Space Scienc
On The Depolarization Asymmetry Seen in Giant Radio Lobes
The depolarization asymmetry seen in double-lobed radio sources, referred to
as the Laing-Garrington (L-G) effect where more rapid depolarization is seen in
the lobe with no visible jet as the wavelength increases, can be explained
either by internal differences between the two lobes, or by an external Faraday
screen that lies in front of only the depolarized lobe. If the jet
one-sidedness is due to relativistic beaming the depolarization asymmetry must
be due to an intervening Faraday screen. If it is intrinsic the depolarization
asymmetry must be related to internal differences in the lobes. We assume in
this paper that the speed in the outer jet of several Fanaroff-Riley Class 1
(FRI) sources exhibiting the L-G effect is close to the 0.1c reported by
several other investigators. For these sources we find that the jet
one-sidedness cannot be explained by beaming and therefore must be intrinsic.
In these FRI sources the L-G effect must be due to differences that originate
inside the lobes themselves. Although it is not known if the flow in the outer
jets of FRII sources also slows to this speed it is suggested that the
explanation of the L-G effect is likely to be the same in both types. This
argument is strengthened by the recent evidence that FRII galaxies have very
large viewing angles, which in turn implies that the L-G model cannot work
regardless of the jet velocity. It may therefore be too soon to completely rule
out internal depolarization in the lobes as the true explanation for the L-G
effect.Comment: 8 pages with 4 figures. Accepted for publication in Ap&S
Harmonising Databases for the Cross National Study of Internal Migration: Lessons from Australia and Britain
This project involves the development of a Web interface to origin-destination statistics from the 1991 Census (in a form that will be compatible with planned 2001 outputs). It provides the user with a set of screen-based tools for setting the parameters governing each data extraction (data set, areas, variables) in the form of a query. Traffic light icons are used to signal what the user has set so far and what remains to be done. There are options to extract different types of flow data and to generate output in different formats. The system can now be used to access the interaction flow data contained in the 1991 Special Migration Statistics Sets 1 and 2 and Special Workplace Statistics Set C. WICID has been demonstrated at the Origin-Destination Statistics Roadshows organised by GRO Scotland and held during May/June 2000 and the Census Offices have expressed interest in using the software in the Census Access Project
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