46,807 research outputs found
THE CANADA-FRANCE REDSHIFT SURVEY V: Global Properties of the Sample
The photometric and spectroscopic data of the CFRS survey of objects with
17.5 < I_{AB} < 22.5 are combined and analysed. The overall completeness is
85%. The redshift histogram of the sample is presented for 591 field galaxies
with secure redshifts. The median redshift is z = 0.56, and the highest
redshift observed is z = 1.3; 25 galaxies have z > 1 The distributions of
magnitudes and colors demonstrate that galaxies at these high redshifts have
very similar colors to those observed locally. The survey thus represents a
major improvement in our knowledge of field galaxies at large look-back times.
Only ~1% of the galaxies are as compact as stars (on images with FWHM ~ 0.9")
and comparisons of the photometric and spectroscopic data show that only one
galaxy was initially incorrectly classified spectroscopically as a star, and
only two stars were misclassified as galaxies. It is demonstrated that the
redshift distributions in the five fields are statistically consistent with
each other, once the reduction in the effective number of independent galaxies
due to small-scale clustering in redshift is taken into account.
The photometric properties of the spectroscopically-unidentified objects
indicate that most are likely to be galaxies rather than stars. At least half
of these must have the same redshift distribution as the identified galaxies,
and a combination of magnitudes, colors and compactness of the remaining
unidentified galaxies is used to predict their redshifts. The majority are
probably ordinary galaxies at the high redshift end of our sample, including
some quiescent galaxies at z > 1.0, rather than some new or unusual population.Comment: 20 uuencoded postscript pages (first part) with 12 figures (second
part). Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html and
coming soon on a CFRS homepage. Accepted June 19, scheduled for Dec 10 issue
of Ap
Investigation into the selection of viewing configurations for three-component planar Doppler velocimetry measurements.
A method for the calculation of three orthogonal velocity components in planar
Doppler velocimetry (PDV) using four or more measured velocity components (to
the three typically used) is presented. The advantages and disadvantages are
assessed by use of a Monte Carlo simulation and experimental measurements of the
velocity field of a rotating disk. The addition of a fourth velocity component
has been shown to lead to reductions in the final errors of up to 25%. The
selection of viewing configurations for experiments is discussed by simulation
of the level of errors in measured velocity components and investigation of the
final level of errors in the orthogonal velocity components. Experimental
measurements of the velocity field of a rotating disk are presented,
demonstrating the effect of the viewing configuration on the final level of
error
Effects of pH on Growth of Salvinia molesta Mitchell
Growth of giant salvinia (
Salvinia molesta
Mitchell) under
different pH regimes was examined at the Lewisville Aquatic
Ecosystem Research Facility (LAERF) in Lewisville, Texas.(PDF has 5 pages.
THE CANADA-FRANCE REDSHIFT SURVEY II: Spectroscopic Program; Data for the 0000-00 and 1000+25 Fields
This paper describes the methods used to obtain the spectroscopic data and
construct redshift catalogs for the Canada-France deep Redshift Survey (CFRS).
The full data set consists of more than one thousand spectra, of objects with
17.5 < I_{AB} < 22.5, obtained from deep multi-slit data with the MARLIN and
MOS-SIS spectrographs at the CFHT. The final spectroscopic catalog contains 200
stars, 591 galaxies with secure redshifts in the range 0 < z < 1.3, 6 QSOs, and
146 objects with very uncertain or unknown redshifts, leading to an overall
success rate of identification of 85%. Additionally, 67 objects affected by
observational problems have been placed in a supplemental list.
We describe here the instrumental set up, and the observing procedures used
to efficiently gather this large data set. New optimal ways of packing spectra
on the detector to significantly increase the multiplexing gain offered by
multi-slit spectroscopy are described. Dedicated data reduction procedures have
been developed under the IRAF environment to allow for fast and accurate
processing.
Very strict procedures have been followed to establish a reliable list of
final spectroscopic measurements. Fully independent processing of the data has
been carried out by three members of the team for each data set associated with
a multi-slit mask, and final redshifts were
assigned only after the careful comparison of the three independent
measurements. A confidence class scheme was established. We strongly emphasize
the benefits of such procedures.
Finally, we present the spectroscopic data obtained for 303 objects in the
0000-00 and 1000+25 fields. The success rate in spectroscopic identification isComment: 16 uuencoded postcript pages with figures 4,5,8,9 and 12. Other
(large) figures available from the authors. Large data table not yet
released. Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html
and coming soon on a CFRS homepage. Accepted June 19, scheduled for the Dec
10 issue of Ap
Constraints On Porosity And Mass Loss In O-Star Winds From The Modeling Of X-Ray Emission Line Profile Shapes
We fit X-ray emission line profiles in high resolution XMM-Newton and Chandra grating spectra of the early O supergiant zeta Pup with models that include the effects of porosity in the stellar wind. We explore the effects of porosity due to both spherical and flattened clumps. We find that porosity models with flattened clumps oriented parallel to the photosphere provide poor fits to observed line shapes. However, porosity models with isotropic clumps can provide acceptable fits to observed line shapes, but only if the porosity effect is moderate. We quantify the degeneracy between porosity effects from isotropic clumps and the mass-loss rate inferred from the X-ray line shapes, and we show that only modest increases in the mass-loss rate (less than or similar to 40%) are allowed if moderate porosity effects (h(infinity) less than or similar to R-*) are assumed to be important. Large porosity lengths, and thus strong porosity effects, are ruled out regardless of assumptions about clump shape. Thus, X-ray mass-loss rate estimates are relatively insensitive to both optically thin and optically thick clumping. This supports the use of X-ray spectroscopy as a mass-loss rate calibration for bright, nearby O stars
The CANADA-FRANCE REDSHIFT SURVEY I: Introduction to the Survey, Photometric Catalogs and Surface Brightness Selection Effects
The Canada-France Redshift Survey has been undertaken to provide a large
well-defined sample of faint galaxies at high redshift in which the selection
criteria match as closely as possible those of samples of nearby galaxies. The
survey is designed to have a median redshift of z ~ 0.6 corresponding to a
look-back time of half the present age of the Universe for Omega ~ 1. Such a
survey can then be used for studying many different aspects of the evolution of
galaxies over the interval 0 < z < 1. In this paper we describe the selection
of the fields, the multicolor imaging observations and the construction and
validation of the photometric catalogs. Particular attention is paid to
quantifying the unavoidable selection effects in surface brightness and their
impact on the survey is assessed in the context of the properties of known
populations of galaxies. The photometric catalogs contain several thousand
objects brighter than I_{AB}< 22.5 and are essentially complete for central
surface brightnesses as faint as 24.5 mag arcsec.
This should be sufficient to include both normal surface brightness galaxies
and prototypes of extreme low surface brightness galaxies.Comment: 17 pages, 2 tables, 10 postscript figures (in 2 parts), uses
aaspp.sty Also available at http://www.dao.nrc.ca/DAO/SCIENCE/science.html
and coming soon on a CFRS homepag
Legal capacities required for prevention and control of noncommunicable diseases
Law lies at the centre of successful national strategies for prevention and control of noncommunicable diseases. By law we mean international agreements, national and subnational legislation, regulations and other executive instruments, and decisions of courts and tribunals. However, the vital role of law in global health development is often poorly understood, and eclipsed by other disciplines such as medicine, public health and economics. This paper identifies key areas of intersection between law and noncommunicable diseases, beginning with the role of law as a tool for implementing policies for prevention and control of leading risk factors. We identify actions that the World Health Organization and its partners could take to mobilize the legal workforce, strengthen legal capacity and support effective use of law at the national level. Legal and regulatory actions must move to the centre of national noncommunicable disease action plans. This requires high-level leadership from global and national leaders, enacting evidence-based legislation and building legal capacities
Use of combinatorial analysis for the study of new material for solar cells applications
This paper presents a combinatorial method for the deposition and
characterization of new metallic precursors for photovoltaic materials.
Onedimensional thin film alloy “libraries” were electrodeposited on Mo-coated
glass. The library elements were deposited in two consecutive baths and then
heated in a reducing atmosphere to promote interdiffusion of the elements. At
the end of this process, the libraries possessed a composition gradient along
their lengths, with single elements at their two opposite ends and one or more
alloys and/or a solid state solution in between. This continuous range of
compositions can therefore be considered a collection of specific precursors
that can be interrogated by examining their corresponding locations, with the
crystallographic structure along the library changing in accordance with the
phase diagram for the metals. The libraries were then sulphurised or selenised
by heating in a sulphur-rich or selenium rich atmosphere; this converted the
metallic precursors in a continuous range of materials, candidates for potential
solar cells absorbers. The libraries were analysed by X-ray diffraction and
energy dispersive X-ray spectrometry. The X-ray diffraction results show phase
changes across the libraries, which can be correlated with the original
precursor concentration at that particular p
The Gravitational Lens CFRS03.1077
An exquisite gravitational arc with a radius of 2.1" has been discovered
around the z = 0.938 field elliptical galaxy CFRS03.1077 during HST
observations of Canada-France Redshift Survey (CFRS) fields. Spectroscopic
observations of the arc show that the redshift of the resolved lensed galaxy is
z = 2.941. This gravitational lens-source system is well-fitted using the
position angle and ellipticity derived from the visible matter distribution and
an isothermal mass profile with a mass corresponding to sigma =387+-5 km/s.
Surprisingly, given the evidence for passive evolution of elliptical galaxies,
this is in good agreement with an estimate based on the fundamental plane for z
= 0 ellipticals. This, perhaps, indicates that this galaxy has not shared in
the significant evolution observed for average elliptical galaxies at z ~ 1. A
second elliptical galaxy with similar luminosity from the CFRS survey, CFRS
14.1311 at z=0.807, is also a lens but in this case the lens model gives a much
smaller mass-to-light ratio, i.e., it appears to confirm the expected
evolution. This suggests that this pair of field elliptical galaxies may have
very different evolutionary histories, a significant result if confirmed.
Clearly, CFRS03.1077 demonstrates that these "Einstein rings" are powerful
probes of high redshift galaxies.Comment: 11 pages, 5 figures, accepted by Ap.
- …