1,078 research outputs found
The abortion-crime link: evidence from England and Wales
We use panel data from 1983 to 1997 for the 42 police force areas in England and Wales to test the hypothesis that legalizing abortion contributes to lower crime rates. We provide an advance on previous work by focusing on the impact of possible endogeneity of effective abortion rates with respect to crime. Our use of U.K. data allows us to exploit regional differences in the provision of free abortions to identify abortion rates. When we use a similar model and estimation methodology, we are able to replicate the negative association between abortion rates and reported crime found by Donohue and Levitt for the U.S. However, when we allow for the potential endogeneity of effective abortion rates with respect to crime, we find no clear connection between the two.
Elastic and Raman scattering of 9.0 and 11.4 MeV photons from Au, Dy and In
Monoenergetic photons between 8.8 and 11.4 MeV were scattered elastically and
in elastically (Raman) from natural targets of Au, Dy and In.15 new cross
sections were measured. Evidence is presented for a slight deformation in the
197Au nucleus, generally believed to be spherical. It is predicted, on the
basis of these measurements, that the Giant Dipole Resonance of Dy is very
similar to that of 160Gd. A narrow isolated resonance at 9.0 MeV is observed in
In.Comment: 31 pages, 11 figure
A spectral line survey in the 2 mm and 1.3 mm windows toward the carbon rich envelope of IRC +10216
We present the results of our spectral line surveys in the 2 mm and 1.3 mm
windows toward the carbon rich envelope of IRC +10216. Totally 377 lines are
detected, among which 360 lines are assigned to 57 known molecules (including
29 rare isotopomers and 2 cyclic isomers). Only 17 weak lines remain
unidentified. Rotational lines of isotopomers 13CCH and HN13C are detected for
the first time in IRC +10216. The detection of the formaldehyde lines in this
star is also confirmed. Possible abundance difference among the three 13C
substituted isotopic isomers of HC3N is reported. Isotopic ratios of C and O
are confirmed to be non-solar while those of S and Si to be nearly solar.
Column densities have been estimated for 15 molecular species. Modified
spectroscopic parameters have been calculated for NaCN, Na13CN, KCN and SiC2.
Transition frequencies from the present observations were used to improve the
spectroscopic parameters of Si13CC, 29SiC2 and 30SiC2.Comment: 17 pages of text, 18 pages of 14 tables, 35 pages of 4 figures, a
typo corrected in Abstrac
Mass loss rates of a sample of irregular and semiregular M-type AGB-variables
We have determined mass loss rates and gas expansion velocities for a sample
of 69 M-type irregular (IRV; 22 objects) and semiregular (SRV; 47 objects)
AGB-variables using a radiative transfer code to model their circumstellar CO
radio line emission. We believe that this sample is representative for the mass
losing stars of this type. The (molecular hydrogen) mass loss rate distribution
has a median value of 2.0E-7 solar masses per year. M-type IRVs and SRVs with a
mass loss rate in excess of 5E-7 solar masses per year must be very rare, and
among these mass losing stars the number of sources with mass loss rates below
a few 10E-8 solar masses per year must be small. We find no significant
difference between the IRVs and the SRVs in terms of their mass loss
characteristics. Among the SRVs the mass loss rate shows no dependence on the
period. Likewise the mass loss rate shows no correlation with the stellar
temperature. The gas expansion velocity distribution has a median of 7.0 km/s.
The mass loss rate and the gas expansion velocity correlate well, a result in
line with theoretical predictions for an optically thin, dust-driven wind. In
general, the model produces line profiles which acceptably fit the observed
ones.
We have compared the results of this M-star sample with a similar C-star
sample analysed in the same way. The mass loss rate characteristics are very
similar for the two samples. On the contrary, the gas expansion velocity
distributions are clearly different. In particular, the number of low-velocity
sources is much higher in the M-star sample. We found no example of the sharply
double-peaked CO line profile, which is evidence of a large, detached CO-shell,
among the M-stars. About 10% of the C-stars show this phenomenon.Comment: 16 pages, 11 figures, accepted by A&
Discovery of SiCSi in IRC+10216: A missing link between gas and dust carriers of SiC bonds
We report the discovery in space of a disilicon species, SiCSi, from
observations between 80 and 350 GHz with the IRAM 30m radio telescope. Owing to
the close coordination between laboratory experiments and astrophysics, 112
lines have now been detected in the carbon-rich star CWLeo. The derived
frequencies yield improved rotational and centrifugal distortion constants up
to sixth order. From the line profiles and interferometric maps with the
Submillimeter Array, the bulk of the SiCSi emis- sion arises from a region of 6
arcseconds in radius. The derived abundance is comparable to that of SiC2. As
expected from chemical equilibrium calculations, SiCSi and SiC2 are the most
abundant species harboring a SiC bond in the dust formation zone and certainly
both play a key role in the formation of SiC dust grains.Comment: To be published in the Astrophysical Journal Letters; Accepted May 6
201
Modelling CO emission from Mira's wind
We have modelled the circumstellar envelope of {\it o} Ceti (Mira) using new
observational constraints. These are obtained from photospheric light scattered
in near-IR vibrational-rotational lines of circumstellar CO molecules at 4.6
micron: absolute fluxes, the radial dependence of the scattered intensity, and
two line ratios. Further observational constraints are provided by ISO
observations of far-IR emission lines from highly excited rotational states of
the ground vibrational state of CO, and radio observations of lines from
rotational levels of low excitation of CO. A code based on the Monte-Carlo
technique is used to model the circumstellar line emission.
We find that it is possible to model the radio and ISO fluxes, as well as the
highly asymmetric radio-line profiles, reasonably well with a spherically
symmetric and smooth stellar wind model. However, it is not possible to
reproduce the observed NIR line fluxes consistently with a `standard model' of
the stellar wind. This is probably due to incorrectly specified conditions of
the inner regions of the wind model, since the stellar flux needs to be larger
than what is obtained from the standard model at the point of scattering, i.e.,
the intermediate regions at approximately 100-400 stellar radii (2"-7") away
from the star. Thus, the optical depth in the vibrational-rotational lines from
the star to the point of scattering has to be decreased. This can be
accomplished in several ways. For instance, the gas close to the star (within
approximately 2") could be in such a form that light is able to pass through,
either due to the medium being clumpy or by the matter being in radial
structures (which, further out, developes into more smooth or shell-like
structures).Comment: 18 pages, 3 figures, accepted for publication in Ap
Hubble Space Telescope Survey of Interstellar ^12CO/^13CO in the Solar Neighborhood
We examine 20 diffuse and translucent Galactic sight lines and extract the
column densities of the ^12CO and ^13CO isotopologues from their ultraviolet
A--X absorption bands detected in archival Space Telescope Imaging Spectrograph
data with lambda/Deltalambda geq 46,000. Five more targets with Goddard
High-Resolution Spectrograph data are added to the sample that more than
doubles the number of sight lines with published Hubble Space Telescope
observations of ^13CO. Most sight lines have 12-to-13 isotopic ratios that are
not significantly different from the local value of 70 for ^12C/^13C, which is
based on mm-wave observations of rotational lines in emission from CO and H_2CO
inside dense molecular clouds, as well as on results from optical measurements
of CH^+. Five of the 25 sight lines are found to be fractionated toward lower
12-to-13 values, while three sight lines in the sample are fractionated toward
higher ratios, signaling the predominance of either isotopic charge exchange or
selective photodissociation, respectively. There are no obvious trends of the
^12CO-to-^13CO ratio with physical conditions such as gas temperature or
density, yet ^12CO/^13CO does vary in a complicated manner with the column
density of either CO isotopologue, owing to varying levels of competition
between isotopic charge exchange and selective photodissociation in the
fractionation of CO. Finally, rotational temperatures of H_2 show that all
sight lines with detected amounts of ^13CO pass through gas that is on average
colder by 20 K than the gas without ^13CO. This colder gas is also sampled by
CN and C_2 molecules, the latter indicating gas kinetic temperatures of only 28
K, enough to facilitate an efficient charge exchange reaction that lowers the
value of ^12CO/^13CO.Comment: 1-column emulateapj, 23 pages, 9 figure
The geometry of the close environment of SV Psc as probed by VLTI/MIDI
Context. SV Psc is an asymptotic giant branch (AGB) star surrounded by an
oxygen-rich dust envelope. The mm-CO line profile of the object's outflow shows
a clear double-component structure. Because of the high angular resolution,
mid-IR interferometry may give strong constraints on the origin of this
composite profile.
Aims. The aim of this work is to investigate the morphology of the
environment around SV Psc using high-angular resolution interferometry
observations in the mid-IR with the Very Large Telescope MID-infrared
Interferometric instrument (VLTI/MIDI).
Methods. Interferometric data in the N-band taken at different baseline
lengths (ranging from 32-64 m) and position angles (73- 142{\deg}) allow a
study of the morphology of the circumstellar environment close to the star. The
data are interpreted on the basis of 2-dimensional, chromatic geometrical
models using the fitting software tool GEM-FIND developed for this purpose.
Results. The results favor two scenarios: (i) the presence of a highly
inclined, optically thin, dusty disk surrounding the central star; (ii) the
presence of an unresolved binary companion at a separation of 13.7 AU and a
position angle of 121.8{\deg} NE. The derived orbital period of the binary is
38.1 yr. This detection is in good agreement with hydrodynamic simulations
showing that a close companion could be responsible for the entrainment of the
gas and dust into a circumbinary structure.Comment: 10 pages, 12 figure
How large are the level sets of the Takagi function?
Let T be Takagi's continuous but nowhere-differentiable function. This paper
considers the size of the level sets of T both from a probabilistic point of
view and from the perspective of Baire category. We first give more elementary
proofs of three recently published results. The first, due to Z. Buczolich,
states that almost all level sets (with respect to Lebesgue measure on the
range of T) are finite. The second, due to J. Lagarias and Z. Maddock, states
that the average number of points in a level set is infinite. The third result,
also due to Lagarias and Maddock, states that the average number of local level
sets contained in a level set is 3/2. In the second part of the paper it is
shown that, in contrast to the above results, the set of ordinates y with
uncountably infinite level sets is residual, and a fairly explicit description
of this set is given. The paper also gives a negative answer to a question of
Lagarias and Maddock by showing that most level sets (in the sense of Baire
category) contain infinitely many local level sets, and that a continuum of
level sets even contain uncountably many local level sets. Finally, several of
the main results are extended to a version of T with arbitrary signs in the
summands.Comment: Added a new Section 5 with generalization of the main results; some
new and corrected proofs of the old material; 29 pages, 3 figure
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