1,217 research outputs found
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.
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
QSO hosts and environments at z=0.9 to 4.2: JHK images with adaptive optics
We have observed nine QSOs with redshifts 0.85 to 4.16 at near-IR wavelengths
with the adaptive optics bonnette of the Canada-France-Hawaii telescope.
Exposure times ranged from 1500 to 24000s (mostly near 7000s) in J, H, or K
bands, with pixels 0.035 arcsec on the sky. The FWHM of the co-added images at
the location of the quasars are typically 0.16 arcsec. Including another QSO
published previously, we find associated QSO structure in at least eight of ten
objects, including the QSO at z = 4.16. The structures seen in all cases
include long faint features which appear to be tidal tails. In four cases we
have also resolved the QSO host galaxy, but find them to be smooth and
symmetrical: future PSF removal may expand this result. Including one object
previously reported, of the nine objects with more extended structure, five are
radio-loud, and all but one of these appear to be in a dense small group of
compact galaxy companions. The radio-quiet objects do not occupy the same dense
environments, as seen in the NIR. In this small sample we do not find any
apparent trends of these properties with redshift, over the range 0.8 < z <
2.4. The colors of the host galaxies and companions are consistent with young
stellar populations at the QSO redshift. Our observations suggest that adaptive
optic observations in the visible region will exhibit luminous signatures of
the substantial star-formation activity that must be occurring.Comment: 22 pages including 10 tables, plus 11 figures. To appear in A
Deep Galaxy survey at 6.75 micron with the ISO satellite
Deep 6.75um mid-IR ISOCAM observations were obtained of the Canada-France
Redshift Survey (CFRS) 1415+52 field with the Infrared Space Observatory. The
identification of the sources with optical counterparts is described in detail,
and a classification scheme is devised which depends on the S/N of the
detection and the inverse probability of chance coincidence. 83% of the 54
ISOCAM sources are identified with Iab<23.5 counterparts. The (I-K)ab colors,
radio properties, spectrophotometric properties and frequency of nuclear
activity of these counterparts differ on average from those of typical CFRS
galaxies. CFRS spectra are available for 21 of the sources which have Iab <=
22.5 (including 7 stars). Most of the strongest sources are stars or AGN. Among
the non--stellar counterparts with spectra, 40% are AGNs, and 53% are galaxies
that display star formation activity and/or significant contributions of A
stars. The ISOCAM sources also display an IR excess, even when compared with
heavily-reddened local starburst galaxies. An upper limit of 30% of
extragalactic ISO sources could be at z>1 of the 44 S6.75um > 150uJy sources
which are non-stellar (7 "spectroscopic" and 3 "photometric" stars excluded)Comment: 13 pages, 12 figures. Accepted for publication in A
The Canada-France redshift survey; 10, the quasar sample
Six objects with broad emission lines and redshifts from 0.48 to 2.07 were discovered among 736 extragalactic objects in the Canada-France Redshift Survey (CFRS). Although the luminosities of half of the objects are such that they are in the Seyfert regime (M_B > -23), all would be designated as quasars in traditional surveys. Since the only selection criterion was that 17.5 1
Hubble Space Telescope imaging of the CFRS and LDSS redshift surveys - IV. Influence of mergers in the evolution of faint field galaxies from z~1
HST images of a sample of 285 galaxies with measured z from the CFRS and
Autofib-LDSS redshift surveys are analysed to derive the evolution of the
merger fraction out to z~1. We have performed visual and machine-based merger
identifications, as well as counts of bright pairs of galaxies with magnitude
differences less than 1.5 mag. We find that the pair fraction increases with z,
with up to ~20% of the galaxies being in physical pairs at z~0.75-1. We derive
a merger fraction varying with z as (1+z)^{3.2 +/- 0.6}, after correction for
line-of-sight contamination, in excellent agreement with the merger fraction
derived from the visual classification of mergers for which m = 3.4 +/- 0.6.
After correcting for seeing effects on the ground-based selection of survey
galaxies, we conclude that the pair fraction evolves as (1+z)^{2.7 +/- 0.6}.
This implies that an average L* galaxy will have undergone 0.8 to 1.8 merger
events from z=1 to 0, with 0.5 to 1.2 merger events occuring in a 2 Gyr time
span at z~0.9. This result is consistent with predictions from semi-analytical
models of galaxy formation. From the simple co-addition of the observed
luminosities of the galaxies in pairs, physical mergers are computed to lead to
a brightening of 0.5 mag for each pair on average, and a boost in star
formation rate of a factor of 2, as derived from the average [O II] equivalent
widths. Mergers of galaxies are therefore contributing significantly to the
evolution of both the luminosity function and luminosity density of the
Universe out to z~1.Comment: 14 pages, 6 PS figures included. Accepted for publication in MNRA
The Canada France Redshift Survey VIII: Evolution of the clustering of galaxies from z~1
We have used the projected two-point correlation function, , to
investigate the spatial distribution of the 591 galaxies with secure redshifts
between in the five CFRS fields.
The slope of the two-point correlation function for the sample as a whole is
, very similar to the local slope, and is
therefore not strongly evolving with redshift. However, the amplitude of the
correlation function decreases strongly with increasing redshift, so that at
it is a factor of 10 lower (for ) than for a
similarly-selected local galaxy population, on scales Mpc
(). As a whole, the CFRS data is adequately represented by
Mpc for , and Mpc for .
Unless the galaxy population at high redshift is quite different from any
population seen locally, an unlikely possibility, then this implies growth of
clustering as described by the evolutionary parameter to be between
.
No difference in the clustering of red and blue galaxies is seen at , although at lower redshifts, , blue galaxies are
somewhat less strongly correlated than the redder galaxies, as seen in local
samples. This effect could be the equivalent for field galaxies to the
Butcher-Oemler effect seen in clusters of galaxies. The cross-correlation
functions between red and blue samples have comparable amplitudes to the
auto-correlation functions of each.
The distribution and power spectrum of pair separations does not indicateComment: 17 pages, 10 figure
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