4,302 research outputs found
Companions of Qsos at Redshift 1.1
We discuss broad- and narrow-band imaging of 7 arcmin fields of 14 QSOs with
redshift ~1.1. The narrow-band filters were chosen to detect redshifted [O II]
3727A, and the broad bands are R and I, which correspond to rest wavelengths
{}~3300A and ~3800A. In 100 arcsec subfields surrounding the QSOs, we detect an
excess of typically 15 detected objects over the background of 25. Several of
the QSO subfields also contain an excess of blue (R-I < 1.0) galaxies compared
with the other subfields. Finally, several of the QSO subfields contain an
excess of galaxies with significant narrow-band flux compared with the other
subfields, and many of these are also blue. Most of the QSOs are radio-quiet in
a region of sky overpopulated with z=1.1 QSOs, and 3 others are radio-loud from
other parts of the sky. We suggest that most of these z=1.1 QSOs are in compact
groups of starbursting galaxies. In our data, there is no significant
difference between radio-loud and radio-quiet QSOs. We discuss cosmic
evolutionary implications.Comment: 9 pages Plain Tex, 8 figures upon request, SISSA-DAO-94-00
Quantum cascade lasers with an integrated polarization mode converter
We discuss the design, fabrication and characterization of waveguide polarization mode converters for quantum cascade lasers operating at 4.6 ÎĽm. We have fabricated a quantum cascade laser with integrated polarization mode converter that emits light of 69% Transverse Electrical (TE) polarization from one facet and 100% Transverse Magnetic (TM) polarization from the other facet
Algebraic Torsion in Contact Manifolds
We extract a nonnegative integer-valued invariant, which we call the "order
of algebraic torsion", from the Symplectic Field Theory of a closed contact
manifold, and show that its finiteness gives obstructions to the existence of
symplectic fillings and exact symplectic cobordisms. A contact manifold has
algebraic torsion of order zero if and only if it is algebraically overtwisted
(i.e. has trivial contact homology), and any contact 3-manifold with positive
Giroux torsion has algebraic torsion of order one (though the converse is not
true). We also construct examples for each nonnegative k of contact 3-manifolds
that have algebraic torsion of order k but not k - 1, and derive consequences
for contact surgeries on such manifolds. The appendix by Michael Hutchings
gives an alternative proof of our cobordism obstructions in dimension three
using a refinement of the contact invariant in Embedded Contact Homology.Comment: 53 pages, 4 figures, with an appendix by Michael Hutchings; v.3 is a
final update to agree with the published paper, and also corrects a minor
error that appeared in the published version of the appendi
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
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Food-chain transfer of zinc from contaminated Urtica dioica and Acer pseudoplatanus L. to Microlophium carnosum and Drepanosiphum platanoidis Schrank
This study examines the food-chain transfer of Zn from two plant species, Urtica dioica (stinging nettle) and Acer pseudoplatanus (sycamore maple), into their corresponding aphid species, Microlophium carnosum and Drepanosiphum platanoidis. The plants were grown in a hydroponic system using solutions with increasing concentrations of Zn from 0.02 to 41.9 mg Zn/l. Above-ground tissue concentrations in U. dioica and M. carnosum increased with increasing Zn exposure (p < 0.001). Zn concentrations in A. pseudoplatanus also increased with solution concentration
from the control to the 9.8 mg Zn/l solution, above which concentrations remained constant. Zn concentrations in both D. platanoidis and the phloem tissue of A. pseudoplatanus were not affected by the Zn concentration in the watering solution. It appears that A. pseudoplatanus was able to limit Zn transport in the phloem, resulting in constant Zn exposure to the aphids. Zn concentrations in D. platanoidis were around three times those in M. carnosum.
Concentrations of Zn in two aphid species are dependant on species and exposure
Galaxy morphology in the rich cluster Abell 2390
We have analysed images of the field of A2390 obtained with the CFHT and HST.
The analysis fits models to bulge and disk components to several hundred
galaxies, with about equal samples from the cluster and field. We also have
assessed and graded asymmetries in the images. The cluster galaxies are
compared in different cluster locations and also compared with field galaxies.
We find that the central old population galaxies are bulge-dominated, while
disk systems have young populations and are found predominantly in the outer
cluster. S0 and bulgy disk galaxies are found throughout, but concentrate in
regions of substructure. Disks of cluster blue galaxies are generally brighter
and smaller than those in the field. We find that the cluster members have a
higher proportion of interacting galaxies than the field sample. Interactions
in the cluster and in the field, as well as cluster infall, appear to inhibit
star-formation in galaxies.Comment: 20 pages including 10 of tables, plus 7 figures; To appear in the
Astronomical Jorurna
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