3,916 research outputs found
Spectral and Hodge theory of `Witt' incomplete cusp edge spaces
Incomplete cusp edges model the behavior of the Weil-Petersson metric on the compactified Riemann moduli space near the interior of a divisor. Assuming such a space is Witt, we construct a fundamental solution to the heat equation, and using a precise description of its asymptotic behavior at the singular set, we prove that the Hodge-Laplacian on differential forms is essentially self-adjoint, with discrete spectrum satisfying Weyl asymptotics. We go on to prove bounds on the growth of -harmonic forms at the singular set and to prove a Hodge theorem, namely that the space of -harmonic forms is naturally isomorphic to the middle-perversity intersection cohomology. Moreover, we develop an asymptotic expansion for the heat trace near
HOUSEHOLD EXPENDITURE ON MEAT VERSUS NONMEAT SOURCES OF PROTEIN IN THE UNITED STATES
Food Consumption/Nutrition/Food Safety,
The origin of the strings in the outer regions of Eta Carinae
The narrow optical filaments (`strings' or `spikes') emerging from the
Homunculus of Eta Carinae are modelled as resulting from the passage of
ballistic `bullets' of material through the dense circumstellar environment. In
this explanation, the string is the decelerating flow of ablated gas from the
bullet. An archive HST image and new forbidden line profiles of the most
distinct of the strings are presented and discussed in terms of this simple
model.Comment: 5 pages, 4 figure
Clumpy Ultracompact HII Regions I: Fully Supersonic Wind-blown Models
We propose that a significant fraction of the ultracompact HII regions found
in massive star-forming clouds are the result of the interaction of the wind
and ionizing radiation from a young massive star with the clumpy molecular
cloud gas in its neighbourhood. Distributed mass loading in the flow allows the
compact nebulae to be long-lived. In this paper, we discuss a particularly
simple case, in which the flow in the HII region is everywhere supersonic. The
line profiles predicted for this model are highly characteristic, for the case
of uniform mass loading. We discuss briefly other observational diagnostics of
these models.Comment: To appear in Monthly Notices of the Royal Astronomical Society. 5
pages LaTeX (uses mn.sty and epsf.sty macros) + 4 PS figures. Also available
via http://axp2.ast.man.ac.uk:8000/Preprints.htm
A high-speed bi-polar outflow from the archetypical pulsating star Mira A
Optical images and high-dispersion spectra have been obtained of the ejected
material surrounding the pulsating AGB star Mira A. The two streams of knots on
either side of the star, found in far ultra-viollet (FUV) GALEX images, have
now been imaged clearly in the light of Halpha. Spatially resolved profiles of
the same line reveal that the bulk of these knots form a bi-polar outflow with
radial velocity extremes of +- 150 km/s with respect to the central star. The
South stream is approaching and the North stream receding from the observer. A
displacement away from Mira A between the position of one of the South stream
knots in the new Halpha image and its position in the previous Palomar
Observatory Sky Survey (POSS I) red plate has been noted. If interpreted as a
consequence of expansion proper motions the bipolar outflow is tilted at 69deg
+- 2deg to the plane of the sky, has an outflow velocity of 160 +- 10 km/s and
is ~1000 y old.Comment: 8 pages, 5 figures. Accepted for pubication by A&
Unified Models of Molecular Emission from Class 0 Protostellar Outflow Sources
Low mass star-forming regions are more complex than the simple spherically
symmetric approximation that is often assumed. We apply a more realistic
infall/outflow physical model to molecular/continuum observations of three late
Class 0 protostellar sources with the aims of (a) proving the applicability of
a single physical model for all three sources, and (b) deriving physical
parameters for the molecular gas component in each of the sources.
We have observed several molecular species in multiple rotational
transitions. The observed line profiles were modelled in the context of a
dynamical model which incorporates infall and bipolar outflows, using a three
dimensional radiative transfer code. This results in constraints on the
physical parameters and chemical abundances in each source.
Self-consistent fits to each source are obtained. We constrain the
characteristics of the molecular gas in the envelopes as well as in the
molecular outflows. We find that the molecular gas abundances in the infalling
envelope are reduced, presumably due to freeze-out, whilst the abundances in
the molecular outflows are enhanced, presumably due to dynamical activity.
Despite the fact that the line profiles show significant source-to-source
variation, which primarily derives from variations in the outflow viewing
angle, the physical parameters of the gas are found to be similar in each core.Comment: MNRAS 12 pages, 16 figure
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