1,831 research outputs found
Tradeable Emission Permits in Oligopoly
The paper considers an oligopolistic industry in which pollution is a by-product of production. Firms are assumed to have emission permits that restrict the amount that they pollute. These permits are assumed to be tradeable and the paper discusses a structure in which the same set of firms operates both in the product market as well as in the pollution permits market. The paper demonstrates that in such a structure allowing trade in emission permits is not necessarily beneficial. In particular it may lead to the choice of inferior production and abatement technologies, it may lead to a market equilibrium with lower output rates and higher prices and it may result in a shift of production from a low cost to a high cost firm.pollution control;oligopoly;trade;emission permit
Self-Consistent, Axisymmetric Two_Integral Models of Elliptical Galaxies with embedded Nuclear Discs
Recently, observations with the Hubble Space Telescope have revealed small
stellar discs embedded in the nuclei of a number of ellipticals and S0s. In
this paper we construct two-integral axisymmetric models for such systems. We
calculate the even part of the phase-space distribution function, and specify
the odd part by means of a simple parameterization. We investigate the
photometric as well as the kinematic signatures of nuclear discs, including
their velocity profiles (VPs), and study the influence of seeing convolution.
The rotation curve of a nuclear disc gives an excellent measure of the central
mass-to-light ratio whenever the VPs clearly reveal the narrow, rapidly
rotating component associated with the nuclear disc. Steep cusps and seeing
convolution both result in central VPs that are dominated by the bulge light,
and these VPs barely show the presence of the nuclear disc, impeding
measurements of the central rotation velocities of the disc stars. However, if
a massive BH is present, the disc component of the VP can be seen in the wing
of the bulge part, and measurements of its mean rotation provide a clear
signature of the presence of the BH. This signature is insensitive to the
uncertainties in the velocity anisotropy, which often lead to ambiguity in the
interpretation of a central rise in velocity dispersion as due to a central BH.Comment: 13 pages, uses mn.tex (included). MNRAS accepted. The 17 PS figures
(not enclosed) can be retrieved from
ftp://strw.leidenuniv.nl/pub/vdbosch/diskpaper
Tradeable Emission Permits in Oligopoly
The paper considers an oligopolistic industry in which pollution is a by-product of production. Firms are assumed to have emission permits that restrict the amount that they pollute. These permits are assumed to be tradeable and the paper discusses a structure in which the same set of firms operates both in the product market as well as in the pollution permits market. The paper demonstrates that in such a structure allowing trade in emission permits is not necessarily beneficial. In particular it may lead to the choice of inferior production and abatement technologies, it may lead to a market equilibrium with lower output rates and higher prices and it may result in a shift of production from a low cost to a high cost firm.
Mapping young stellar populations towards Orion with Gaia DR1
We use the first data release of the Gaia mission to explore the three
dimensional arrangement and the age ordering of the many stellar groups towards
the Orion OB association, aiming at a new classification and characterization
of the stellar population. We make use of the parallaxes and proper motions
provided in the Tycho Gaia Astrometric Solution (TGAS) sub-set of the Gaia
catalogue, and of the combination of Gaia and 2MASS photometry. In TGAS we find
evidence for the presence of a young population, at a parallax , loosely distributed around some known clusters: 25 Ori,
Ori and Ori, and NGC 1980 ( Ori). The low mass
counterpart of this population is visible in the color-magnitude diagrams
constructed by combining Gaia and 2MASS photometry. We study the density
distribution of the young sources in the sky. We find the same groups as in
TGAS, and also some other density enhancements that might be related to the
recently discovered Orion X group, the Orion dust ring, and to the
Ori complex. We estimate the ages of this population and we infer the presence
of an age gradient going from 25 Ori (13-15 Myr) to the ONC (1-2 Myr). We
confirm this age ordering by repeating the Bayesian fit using the Pan-STARRS1
data. The estimated ages towards the NGC 1980 cluster span a broad range of
values. This can either be due to the presence of two populations coming from
two different episodes of star formation or to a large spread along the line of
sight of the same population. Our results form the first step towards using the
Gaia data to unravel the complex star formation history of the Orion region in
terms of the different star formation episodes, their duration, and their
effects on the surrounding interstellar medium.Comment: 17 pages, 17 figure
The dynamical distance and intrinsic structure of the globular cluster omega Centauri
We determine the dynamical distance D, inclination i, mass-to-light ratio M/L
and the intrinsic orbital structure of the globular cluster omega Cen, by
fitting axisymmetric dynamical models to the ground-based proper motions of van
Leeuwen et al. and line-of-sight velocities from four independent data-sets. We
correct the observed velocities for perspective rotation caused by the space
motion of the cluster, and show that the residual solid-body rotation component
in the proper motions can be taken out without any modelling other than
assuming axisymmetry. This also provides a tight constraint on D tan i.
Application of our axisymmetric implementation of Schwarzschild's orbit
superposition method to omega Cen reveals no dynamical evidence for a
significant radial dependence of M/L. The best-fit dynamical model has a
stellar V-band mass-to-light ratio M/L_V = 2.5 +/- 0.1 M_sun/L_sun and an
inclination i = 50 +/- 4 degrees, which corresponds to an average intrinsic
axial ratio of 0.78 +/- 0.03. The best-fit dynamical distance D = 4.8 +/- 0.3
kpc (distance modulus 13.75 +/- 0.13 mag) is significantly larger than obtained
by means of simple spherical or constant-anisotropy axisymmetric dynamical
models, and is consistent with the canonical value 5.0 +/- 0.2 kpc obtained by
photometric methods. The total mass of the cluster is (2.5 +/- 0.3) x 10^6
M_sun. The best-fit model is close to isotropic inside a radius of about 10
arcmin and becomes increasingly tangentially anisotropic in the outer region,
which displays significant mean rotation. This phase-space structure may well
be caused by the effects of the tidal field of the Milky Way. The cluster
contains a separate disk-like component in the radial range between 1 and 3
arcmin, contributing about 4% to the total mass.Comment: 37 pages (23 figures), accepted for publication in A&A, abstract
abridged, for PS and PDF file with full resolution figures, see
http://www.strw.leidenuniv.nl/~vdven/oc
Kinematics of Metal-Poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Non-Kinematically Selected Stars
(Abbreviated) We present a detailed analysis of the space motions of 1203
solar-neighborhood stars with metal abundances [Fe/H] <= -0.6, on the basis of
a recently revised and supplemented catalog of metal-poor stars selected
without kinematic bias (Beers et al. 2000). This sample, having available
proper motions, radial velocities, and distance estimates for stars with a wide
range of metal abundances, is by far the largest such catalog to be assembled
to date. Unlike essentially all previous kinematically selected catalogs, the
metal-poor stars in our sample exhibit a diverse distribution of orbital
eccentricities, e, with no apparent correlation between [Fe/H] and e. This
demonstrates, clearly and convincingly, that the evidence offered by Eggen,
Lynden-Bell, and Sandage (1962) for a rapid collapse of the Galaxy, an apparent
correlation between the orbital eccentricity of halo stars with metallicity, is
basically the result of their proper-motion selection bias. However, even in
our non-kinematically selected sample, we have identified a small concentration
of high-e stars at [Fe/H] = -1.7, which may originate, in part, from infalling
gas during the early formation of the Galaxy. The implications of our results
for the formation of the Galaxy are also discussed, in particular in the
context of the currently favored CDM theory of hierarchical galaxy formation.Comment: 51 pages, including 17 figures, to appear in AJ (June 2000), full
paper with all figures embedded available at
http://pluto.mtk.nao.ac.jp/people/chiba/preprint/halo5
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