37,019 research outputs found
A large scale extinction map of the Galactic Anticenter from 2MASS
We present a 127deg x 63deg extinction map of the Anticenter of the Galaxy,
based on and colour excess maps from 2MASS. This 8001 square degree
map with a resolution of 4 arcminutes is provided as online material. The
colour excess ratio / is used to determine the power law index of
the reddening law (\beta) for individual regions contained in the area (e.g.
Orion, Perseus, Taurus, Auriga, Monoceros, Camelopardalis, Cassiopeia). On
average we find a dominant value of \beta=1.8+-0.2 for the individual clouds,
in agreement with the canonical value for the interstellar medium. We also show
that there is an internal scatter of \beta values in these regions, and that in
some areas more than one dominant \beta value is present. This indicates large
scale variations in the dust properties. The analysis of the A_V values within
individual regions shows a change in the slope of the column density
distribution with distance. This can either be attributed to a change in the
governing physical processes in molecular clouds on spatial scales of about 1pc
or an A_V dilution with distance in our map.Comment: 18 pages, 29 Figures, 1 Table, Accepted for publication by MNRAS, A
version with higher resolution figures can be found at
http://astro.kent.ac.uk/~df
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The importance of strategic financial leadership in the UK public sector in a time of financial austerity
Given the severity of financial pressures on public authorities, this report is concerned with how finance managers in public services are coping with the demands placed on them and how they can demonstrate improved value by providing more effective strategic financial leadership. It considers how they are applying managerial approaches and solutions to the challenges of austerity and the role that the public sector finance function can play in this process
The Progenitor of the New COMPTEL/ROSAT Supernova Remnant in Vela
We show that (1) the newly discovered supernova remnant (SNR), GRO
J0852--4642/RX J0852.0--4622, was created by a core-collapse supernova of a
massive star, and (2) the same supernova event which produced the Ti
detected by COMPTEL from this source is probably also responsible for a large
fraction of the observed Al emission in the Vela region detected by the
same instrument. The first conclusion is based on the fact that the remnant is
currently expanding too slowly given its young age for it to be caused by a
Type Ia supernova. If the current SNR shell expansion speed is greater than
3000 km/s, a Type II supernova with a moderate kinetic energy
exploding at about 150 pc away is favored. If the SNR expansion speed is lower
than 2000 km s, as derived naively from the X-ray data, a much more
energetic supernova is required to have occurred at pc away in a
dense environment at the edge of the Gum nebula. This progenitor has a
preferred ejecta mass of and therefore, it is probably a Type
Ib or Type Ic supernova. However, the required high ambient density of in this scenario is difficult to reconcile with the regional CO
data. A combination of our estimates of the age/energetics of the new SNR and
the almost perfect positional coincidence of the new SNR with the centroid of
the COMPTEL Al emission feature of the Vela region strongly favors a
causal connection. If confirmed, this will be the first case where both
Ti and Al are detected from the same young SNR and together they
can be used to select preferred theoretical core-collapse supernova models.Comment: Revised, 10 pages, 2 figures, to appear in ApJ Lett Vol.514 on April
1, 199
The Gravitomagnetic Influence on Gyroscopes and on the Lunar Orbit
Gravitomagnetism--a motional coupling of matter analogous to the Lorentz
force in electromagnetism--has observable consequences for any scenario
involving differing mass currents. Examples include gyroscopes located near a
rotating massive body, and the interaction of two orbiting bodies. In the
former case, the resulting precession of the gyroscope is often called ``frame
dragging,'' and is the principal measurement sought by the Gravity Probe-B
experiment. The latter case is realized in the earth-moon system, and the
effect has in fact been confirmed via lunar laser ranging (LLR) to
approximately 0.1% accuracy--better than the anticipated accuracy of the
Gravity-Probe-B result. This paper shows the connnection between these
seemingly disparate phenomena by employing the same gravitomagnetic term in the
equation of motion to obtain both gyroscopic precession and modification of the
lunar orbit. Since lunar ranging currently provides a part in a thousand fit to
the gravitomagnetic contributions to the lunar orbit, this feature of
post-Newtonian gravity is not adjustable to fit any anomalous result beyond the
0.1% level from Gravity Probe-B without disturbing the existing fit of theory
to the 36 years of LLR data.Comment: 4 pages; accepted for publication in Physical Review Letter
Field Dependent Phase Diagram of the Quantum Spin Chain (CH3)2NH2CuCl3
Although (CH3)2NH2CuCl3 (MCCL) was first examined in the 1930's [1], there
are open questions regarding the magnetic dimensionality and nature of the
magnetic properties. MCCL is proposed to be a S=1/2 alternating ferromagnetic
antiferromagnetic spin chain alternating along the crystalline a-axis [2,3].
Proposed ferromagnetic (JFM =1.3 meV) and antiferromagnetic (JAFM =1.1 meV)
exchange constants make this system particularly interesting for experimental
study. Because JFM and JAFM are nearly identical, the system should show
competing behavior between S=1/2 (AFM) and S=1(FM) effects. We report low
temperature magnetic field dependent susceptibility, chi(H), and specific heat,
Cp, of MCCL. These provide an initial magnetic-field versus temperature phase
diagram. A zero-field phase transition consistent with long range magnetic
order is observed at T=0.9 K. The transition temperature can be reduced via
application of a magnetic field. We also present comparisons to a FM/AFM dimer
model that accounts for chi(T,H=0) and Cp(H,T).Comment: 2 pages, 1 figure included in text. Submitted to proceedings of 24th
International Conference on Low Temperature Physics, August 200
High-resolution saturation spectroscopy of singly-ionized iron with a pulsed uv laser
We describe the design and realization of a scheme for uv laser spectroscopy
of singly-ionized iron (Fe II) with very high resolution. A buffer-gas cooled
laser ablation source is used to provide a plasma close to room temperature
with a high density of Fe II. We combine this with a scheme for pulsed-laser
saturation spectroscopy to yield sub-Doppler resolution. In a demonstration
experiment, we have examined an Fe II transition near 260 nm, attaining a
linewidth of about 250 MHz. The method is well-suited to measuring transition
frequencies and hyperfine structure. It could also be used to measure small
isotope shifts in isotope-enriched samples.Comment: 9 pages, 5 figures, updated Fig. 3. For submission to J. Phys.
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