2,820 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
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
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
The new very small angle neutron scattering spectrometer at Laboratoire Leon Brillouin
The design and characteristics of the new very small angle neutron scattering
spectrometer under construction at the Laboratoire Leon Brillouin is described.
Its goal is to extend the range of scattering vectors magnitudes towards
2x10{-4} /A. The unique feature of this new spectrometer is a high resolution
two dimensional image plate detector sensitive to neutrons. The wavelength
selection is achieved by a double reflection supermirror monochromator and the
collimator uses a novel multibeam design
THE CANADA-FRANCE REDSHIFT SURVEY IX: HST Imaging of High-Redshift Field Galaxies
HST B and I images are presented of 32 CFRS galaxies with secure redshifts in
the range 0.5 < z < 1.2. These galaxies exhibit the same range of morphological
types as seen locally, i.e., ellipticals, spirals and irregulars. The galaxies
look far less regular in the images (rest-frame ultraviolet) than at longer
wavelengths, underlining the fact that optical images of galaxies at still
higher redshift should be interpreted with caution. Quantitative analyses of
the galaxies yield disk sizes, bulge fractions, and colors for each component.
At these redshifts, galaxy disks show clear evidence for surface brightness
evolution. The mean rest-frame central surface brightness of the disks of
normal late-type galaxies is mu_{AB}(B)=20.2 \pm 0.25 mag arcsec^{-2}, about
1.2 mag brighter than the Freeman (1970) value. Some degree of peculiarity is
measurable in 10 (30%) of the galaxies and 4 (13%) show clear signs of
interaction/mergers. There are 9 galaxies (30%) dominated by blue compact
components. These components, which appear to be related to star formation,
occur most often in peculiar/asymmetric galaxies (some of which appear to be
interacting), but a few are in otherwise normal galaxies. Thus, of the galaxies
bluer than present-day Sb, one-third are "blue nucleated galaxies", and half
are late-type galaxies with disks which are significantly brighter than normal
galaxies at z=0. Taken together, these two effects must be responsible for much
of the observed evolution of the luminosity function of blue galaxies.Comment: uuencoded compressed postscript, 8 pages, 1 table + 5 figures in a
separate part. Also available at http://www.astro.utoronto.ca/~lilly/CFRS/ .
Accepted for publication in ApJ Letter
The CANADA-FRANCE REDSHIFT SURVEY XIII: The luminosity density and star-formation history of the Universe to z ~ 1
The comoving luminosity density of the Universe is estimated from the CFRS
faint galaxy sample in three wavebands (2800A, 4400A and 1 micron) over the
redshift range 0 < z < 1. In all three wavebands, the comoving luminosity
density increases markedly with redshift. For a (q_0 = 0.5, Omega = 1.0)
cosmological model, the comoving luminosity density increases as at 1 micron, as at 4400A and as at 2800A, these exponents being reduced by 0.43 and 1.12 for (0.05,0.1)
and (-0.85,0.1) cosmological models respectively. The variation of the
luminosity density with epoch can be reasonably well modelled by an actively
evolving stellar population with a Salpeter initial mass function (IMF)
extending to 125 M_sun, a star-formation rate declining with a power 2.5, and a
turn-on of star-formation at early epochs. A Scalo (1986) IMF extending to the
same mass limit produces too many long-lived low mass stars. This rapid
evolution of the star-formation rate and comoving luminosity density of the
Universe is in good agreement with the conclusions of Pei and Fall (1995) from
their analysis of the evolving metallicity of the Universe. One consequence of
this evolution is that the physical luminosity density at short wavelengths has
probably declined by two orders of magnitude since z ~ 1.Comment: uuencoded compressed tar file containing 8 page Tex file, 2
postscript figures and 2 tables. Ap J Letters, in press. Also available at
http://www.astro.utoronto.ca/~lilly/CFRS/papers.htm
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