1,267 research outputs found
Morphological Evolution of Distant Galaxies from Adaptive Optics Imaging
We report here on a sample of resolved, infrared images of galaxies at z~0.5
taken with the 10-m Keck Telescope's Adaptive Optics (AO) system. We regularly
achieve a spatial resolution of 0.05'' and are thus able to resolve both the
disk and bulge components. We have extracted morphological information for ten
galaxies and compared their properties to those of a local sample. The
selection effects of both samples were explicitly taken into account in order
to derive the unbiased result that disks at z~0.5 are ~0.6 mag arcsec^-2
brighter than, and about the same size as, local disks. The
no-luminosity-evolution case is ruled out at 90% confidence. We also find, in a
more qualitative analysis, that the bulges of these galaxies have undergone a
smaller amount of surface brightness evolution and have also not changed
significantly in size from z~0.5 to today. This is the first time this type of
morphological evolution has been measured in the infrared and it points to the
unique power of AO in exploring galaxy evolution.Comment: 27 pages, 7figures, 2 tables. Accepted for publication in the
Astrophysical Journa
Exploring the Structure of Distant Galaxies with Adaptive Optics on the Keck-II Telescope
We report on the first observation of cosmologically distant field galaxies
with an high order Adaptive Optics (AO) system on an 8-10 meter class
telescope. Two galaxies were observed at 1.6 microns at an angular resolution
as high as 50 milliarcsec using the AO system on the Keck-II telescope. Radial
profiles of both objects are consistent with those of local spiral galaxies and
are decomposed into a classic exponential disk and a central bulge. A
star-forming cluster or companion galaxy as well as a compact core are detected
in one of the galaxies at a redshift of 0.37+/-0.05. We discuss possible
explanations for the core including a small bulge, a nuclear starburst, or an
active nucleus. The same galaxy shows a peak disk surface brightness that is
brighter than local disks of comparable size. These observations demonstrate
the power of AO to reveal details of the morphology of distant faint galaxies
and to explore galaxy evolution.Comment: 5 pages, Latex, 3 figures. Accepted for publication in P.A.S.
A multi-specialty surgical course for residents transitioning from early to intermediate training.
Intermediate oncologic outcomes after uniportal video-assisted thoracoscopic thymectomy for early-stage thymoma
Propagation of Avalanches in Mn-acetate: Magnetic Deflagration
Local time-resolved measurements of fast reversal of the magnetization of
single crystals of Mn12-acetate indicate that the magnetization avalanche
spreads as a narrow interface that propagates through the crystal at a constant
velocity that is roughly two orders of magnitude smaller than the speed of
sound. We argue that this phenomenon is closely analogous to the propagation of
a flame front (deflagration) through a flammable chemical substance.Comment: 5 pages, 5 figure
Classical generalized constant coupling model for geometrically frustrated antiferromagnets
A generalized constant coupling approximation for classical geometrically
frustrated antiferromagnets is presented. Starting from a frustrated unit we
introduce the interactions with the surrounding units in terms of an internal
effective field which is fixed by a self consistency condition. Results for the
magnetic susceptibility and specific heat are compared with Monte Carlo data
for the classical Heisenberg model for the pyrochlore and kagome lattices. The
predictions for the susceptibility are found to be essentially exact, and the
corresponding predictions for the specific heat are found to be in very good
agreement with the Monte Carlo results.Comment: 4 pages, 3 figures, 2 columns. Discussion about the zero T value of
the pyrochlore specific heat correcte
Gaseous emissions during concurrent combustion of biomass and non-recyclable municipal solid waste
Background: Biomass and municipal solid waste offer sustainable sources of
energy; for example to meet heat and electricity demand in the form of combined
cooling, heat and power. Combustion of biomass has a lesser impact than solid
fossil fuels (e. g. coal) upon gas pollutant emissions, whilst energy recovery
from municipal solid waste is a beneficial component of an integrated,
sustainable waste management programme. Concurrent combustion of these fuels
using a fluidised bed combustor may be a successful method of overcoming some of
the disadvantages of biomass (high fuel supply and distribution costs,
combustion characteristics) and characteristics of municipal solid waste
(heterogeneous content, conflict with materials recycling). It should be
considered that combustion of municipal solid waste may be a financially
attractive disposal route if a 'gate fee' value exists for accepting waste for
combustion, which will reduce the net cost of utilising relatively more
expensive biomass fuels. Results: Emissions of nitrogen monoxide and sulphur
dioxide for combustion of biomass are suppressed after substitution of biomass
for municipal solid waste materials as the input fuel mixture. Interactions
between these and other pollutants such as hydrogen chloride, nitrous oxide and
carbon monoxide indicate complex, competing reactions occur between
intermediates of these compounds to determine final resultant emissions.
Conclusions: Fluidised bed concurrent combustion is an appropriate technique to
exploit biomass and municipal solid waste resources, without the use of fossil
fuels. The addition of municipal solid waste to biomass combustion has the
effect of reducing emissions of some gaseous pollutants
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