4,766 research outputs found
Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217
As the number of observed brown dwarf outflows is growing it is important to
investigate how these outflows compare to the well studied jets from young
stellar objects. A key point of comparison is the relationship between outflow
and accretion activity and in particular the ratio between the mass outflow and
accretion rates (/). The brown dwarf candidate
ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric
study of brown dwarfs, to be driving an asymmetric outflow with the
blue-shifted lobe having a position angle of 20. The aim here
is to further investigate the properties of ISO-ChaI 217, the morphology and
kinematics of its outflow, and to better constrain
(/). The outflow is spatially resolved in the
lines and is detected out to 1\farcs6
in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry
between the two lobes is confirmed although the velocity asymmetry is less
pronounced with respect to our previous study. Using thirteen different
accretion tracers we measure log() [M/yr]= -10.6
0.4. As it was not possible to measure the effect of extinction on the ISO-ChaI
217 outflow was derived for a range of values of A, up to
a value of A = 2.5 mag estimated for the source extinction. The logarithm
of the mass outflow () was estimated in the range -11.7 to -11.1
for both jets combined. Thus / [\Msun/yr] lies
below the maximum value predicted by magneto-centrifugal jet launching models.
Finally, both model fitting of the Balmer decrements and spectro-astrometric
analysis of the H line show that the bulk of the H I emission comes
from the accretion flow.Comment: accepted by Astronomy & Astrophysic
An Economic Evaluation of Irish Salmon Fishing General Summary of Results. ESRI Memorandum Series No. 99 1974
The purpose of the study was to investigate the economies of salmon fishing in Ireland. Essentially, it set out to answer the question "how valuable was the Irish salmon industry to the economy in 1970?" In order to answer this
question, the study tried to evaluate the economic impact of angling and commercial fishing on the various districts, determine the capacity of the industry for future development and provide information to assist in the more effective marketing of salmon and sea-trout angling. Although the survey was confined to 1970, its findings may be updated for subsequent years by means of the regularly published data on catches and numbers of licences, and by appropriate price indices
An Economic Evaluation of Irish Salmon Fishing, II: The Irish Anglers. General Research Series Paper No. 75, June 1974
The first part of the study, which dealt with salmon
anglers from outside the Republic, has already been completed and the results
published [i]. The terms of reference of the study together with some background
information were given in the latter publication. This second part is
concerned with Irish salmon anglers and particularly with assessing the extent
and regional distribution of the economic effects of their activities. In both
these papers, we attempt to find out what Sort of peoplethe ang!ers are; where
and how Often they fish, and, particularly, how much they spend and where this
expenditure takes place. The concluding part of the study will deal with commercial
fishermen and fishery operators, and in that paper we also hope to
amalgamate our information on angling and on commercial fishing into a
comprehensive picture of Irish salmon fishing
An Economic Evaluation of Irish Salmon Fishing, III: The Commercial Fishermen. ESRI General Research Series Paper No. 78, November 1974
This is the third report of a study entitled An Economic Evaluation of Irish Salmon and Sea-Trout Fishing which was sponsored by the Department of Agriculture and Fishseries and conducted by the Economic and Social Research
Institute. The first report was concerned with the visiting anglers (i.e. salmon
anglers from outside the Republic) [I] while the second report dealt with the
Irish anglers [2]. The terms of reference of the study together with some
background information on the life history of the salmon and on methods of
evaluation were given in the previous reports. This third study deals with
commercial salmon fishermen, their methods of operation, the time spent
fishing, their alternative occupations and particularly with the income arising
from salmon fishing. The report also gives information relating to the owners
of angling waters and the opinions of these and of the commercial fishermen
on certain aspects of salmon fishing. In the final section of the paper an attempt
is made to collate the results of the three studies so as to provide some basis
on which policy issues can be considered
A segmentation approach to delineate zones for differential nitrogen intervention.
Multi-source and -temporal data integration is expected to support the delineation of within-field management zones that may better conform to unique combinations of crop yield variations. This work addresses the evaluation of zone delineation approaches based on image classification and segmentation methods. An object based segmentation is introduced using ancillary data from multivariate analysis of yield maps. A simple economic evaluation is conducted to compare delineation methods aiming variable-rate Nitrogen applications. Advantages and penalties are suggested for 2, 3, and 4 management zones. Results show that a procedure combining multiresolution, watershed and region grow segmentation algorithms has systematically resulted in greater net worth. It is suggested that segmentation methods have potential application for zone management delineations supporting contiguous patter
Chemical composition and mixing in giant HII regions: NGC3603, 30Doradus, and N66
We investigate the chemical abundances of NGC3603 in the Milky Way, of
30Doradus in the Large Magellanic Cloud, and of N66 in the Small Magellanic
Cloud. Mid-infrared observations with the Infrared Spectrograph onboard the
Spitzer Space Telescope allow us to probe the properties of distinct physical
regions within each object: the central ionizing cluster, the surrounding
ionized gas, photodissociation regions, and buried stellar clusters. We detect
[SIII], [SIV], [ArIII], [NeII], [NeIII], [FeII], and [FeIII] lines and derive
the ionic abundances. Based on the ionic abundance ratio (NeIII/H)/(SIII/H), we
find that the gas observed in the MIR is characterized by a higher degree of
ionization than the gas observed in the optical spectra. We compute the
elemental abundances of Ne, S, Ar, and Fe. We find that the alpha-elements Ne,
S, and Ar scale with each other. Our determinations agree well with the
abundances derived from the optical. The Ne/S ratio is higher than the solar
value in the three giant HII regions and points toward a moderate depletion of
sulfur on dust grains. We find that the neon and sulfur abundances display a
remarkably small dispersion (0.11dex in 15 positions in 30Doradus), suggesting
a relatively homogeneous ISM, even though small-scale mixing cannot be ruled
out.Comment: Accepted for submission to ApJ. The present version replaces the
submitted one. Changes: new title, new figure, the text was modified in the
discussio
A fast stroboscopic spectral method for rotating systems in numerical relativity
We present a numerical technique for solving evolution equations, as the wave
equation, in the description of rotating astrophysical compact objects in
comoving coordinates, which avoids the problems associated with the light
cylinder. The technique implements a fast spectral matching between two domains
in relative rotation: an inner spherical domain, comoving with the sources and
lying strictly inside the light cylinder, and an outer inertial spherical
shell. Even though the emphasis is placed on spectral techniques, the matching
is independent of the specific manner in which equations are solved inside each
domain, and can be adapted to different schemes. We illustrate the strategy
with some simple but representative examples.Comment: 16 pages, 15 figure
Chaos in an Exact Relativistic 3-body Self-Gravitating System
We consider the problem of three body motion for a relativistic
one-dimensional self-gravitating system. After describing the canonical
decomposition of the action, we find an exact expression for the 3-body
Hamiltonian, implicitly determined in terms of the four coordinate and momentum
degrees of freedom in the system. Non-relativistically these degrees of freedom
can be rewritten in terms of a single particle moving in a two-dimensional
hexagonal well. We find the exact relativistic generalization of this
potential, along with its post-Newtonian approximation. We then specialize to
the equal mass case and numerically solve the equations of motion that follow
from the Hamiltonian. Working in hexagonal-well coordinates, we obtaining
orbits in both the hexagonal and 3-body representations of the system, and plot
the Poincare sections as a function of the relativistic energy parameter . We find two broad categories of periodic and quasi-periodic motions that we
refer to as the annulus and pretzel patterns, as well as a set of chaotic
motions that appear in the region of phase-space between these two types.
Despite the high degree of non-linearity in the relativistic system, we find
that the the global structure of its phase space remains qualitatively the same
as its non-relativisitic counterpart for all values of that we could
study. However the relativistic system has a weaker symmetry and so its
Poincare section develops an asymmetric distortion that increases with
increasing . For the post-Newtonian system we find that it experiences a
KAM breakdown for : above which the near integrable regions
degenerate into chaos.Comment: latex, 65 pages, 36 figures, high-resolution figures available upon
reques
First upper limit analysis and results from LIGO science data: stochastic background
I describe analysis of correlations in the outputs of the three LIGO
interferometers from LIGO's first science run, held over 17 days in August and
September of 2002, and the resulting upper limit set on a stochastic background
of gravitational waves. By searching for cross-correlations between the LIGO
detectors in Livingston, LA and Hanford, WA, we are able to set a 90%
confidence level upper limit of h_{100}^2 Omega_0 < 23 +/- 4.6.Comment: 7 pages; 1 eps figures; proceeding from 2003 Edoardo Amaldi Meeting
on Gravitational Wave
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