8,273 research outputs found
External Shear in Quadruply Imaged Lens Systems
We use publicly available N-body simulations and semi-analytic models of
galaxy formation to estimate the levels of external shear due to structure near
the lens in gravitational lens systems. We also describe two selection effects,
specific to four-image systems, that enhance the probability of observing
systems to have higher external shear. Ignoring additional contributions from
"cosmic shear" and assuming that lens galaxies are not significantly flattened,
we find that the mean shear at the position of a quadruple lens galaxy is 0.11,
the rms shear is roughly 0.15, and there is roughly a 45% likelihood of
external shear greater than 0.1. This is much larger than previous estimates
and in good agreement with typical measured external shear. The higher shear
primarily stems from the tendency of early-type galaxies, which are the
majority of lenses, to reside in overdense regions.Comment: 5 pages, 2 figures, ApJ in press, minor revision
Construction of Parseval wavelets from redundant filter systems
We consider wavelets in L^2(R^d) which have generalized multiresolutions.
This means that the initial resolution subspace V_0 in L^2(R^d) is not singly
generated. As a result, the representation of the integer lattice Z^d
restricted to V_0 has a nontrivial multiplicity function. We show how the
corresponding analysis and synthesis for these wavelets can be understood in
terms of unitary-matrix-valued functions on a torus acting on a certain vector
bundle. Specifically, we show how the wavelet functions on R^d can be
constructed directly from the generalized wavelet filters.Comment: 34 pages, AMS-LaTeX ("amsproc" document class) v2 changes minor typos
in Sections 1 and 4, v3 adds a number of references on GMRA theory and
wavelet multiplicity analysis; v4 adds material on pages 2, 3, 5 and 10, and
two more reference
Harmonic analysis of iterated function systems with overlap
In this paper we extend previous work on IFSs without overlap. Our method
involves systems of operators generalizing the more familiar Cuntz relations
from operator algebra theory, and from subband filter operators in signal
processing.Comment: 37 page
Confirming EIS Clusters. Optical and Infrared Imaging
Clusters of galaxies are important targets in observationally cosmology, as
they can be used both to study the evolution of the galaxies themselves and to
constrain cosmological parameters. Here we report on the first results of a
major effort to build up a sample of distant galaxy clusters to form the basis
for further studies within those fields. We search for simultaneous
overdensities in color and space to obtain supporting evidence for the reality
of the clusters. We find a confirmation rate for EIS clusters of 66%,
suggesting that a total of about 80 clusters with z>=0.6 are within reach using
the EIS cluster candidates.Comment: 4 pages, 2 figures, to appear in the proceedings of the IGRAP
International Conference 1999 on 'Clustering at high Redshift
The Extinction and Distance of Maffei 1
We have obtained low- and high-resolution spectra of the core of the
highly-reddened elliptical galaxy Maffei 1. From these data, we have obtained
the first measurement of the Mg2 index, and have measured the velocity
dispersion and radial velocity with improved accuracy. To evaluate the
extinction, a correlation between the Mg2 index and effective V-I colour has
been established for elliptical galaxies. Using a new method for correcting for
effective wavelength shifts, we find A_V = 4.67 +/- 0.19 mag, which is lower by
0.4 mag than previously thought. To establish the distance, the Fundamental
Plane for elliptical galaxies has been constructed in I. The velocity
dispersion of Maffei 1, measured to be 186.8 +/- 7.4 km/s, in combination with
modern wide-field photometry in I, leads to a distance of 2.92 +/- 0.37 Mpc.
The Dn-sigma relation, which is independently calibrated, gives 3.08 +/- 0.85
Mpc and 3.23 +/- 0.67 Mpc from photometry in B and K`, respectively. The
weighted mean of the three estimates is 3.01 +/- 0.30 Mpc. The distance and
luminosity make Maffei 1 the nearest giant elliptical galaxy. The radial
velocity of Maffei 1 is +66.4 +/- 5.0 km/s, significantly higher than the
accepted value of -10 km/s. The Hubble distance corresponding to the mean
velocity of Maffei 1, Maffei 2 and IC342 is 3.5 Mpc. Thus, it is unlikely that
Maffei 1 has had any influence on Local Group dynamics
Abundance Analysis of HE2148-1247, A Star With Extremely Enhanced Neutron Capture Elements
Abundances for 27 elements in the very metal poor dwarf star HE2148-1247 are
presented, including many of the neutron capture elements. We establish that
HE2148-1247 is a very highly s-process enhanced star with anomalously high Eu
as well, Eu/H about half Solar, demonstrating the large addition of heavy
nuclei at [Fe/H] = -2.3 dex. Ba and La are enhanced by a somewhat larger factor
and reach the solar abundance, while Pb significantly exceeds it. Ba/Eu is ten
times the solar r-process ratio but much less than that of the s-process,
indicating a substantial r-process addition as well. C and N are also very
highly enhanced. We have found that HE2148-1247 is a radial velocity variable.
The C, N and the s-process element enhancements thus presumably were produced
through mass transfer from a former AGB binary companion. The large enhancement
of heavy r-nuclides also requires an additional source as this is far above any
inventory in the ISM at such low [Fe/H]. We further hypothesize that accretion
onto the white dwarf from the envelope of the star caused accretion induced
collapse of the white dwarf, forming a neutron star, which then produced heavy
r-nuclides and again contaminated its companion. (abridged)Comment: Accepted by the Astrophysical Journal. Companion paper by Qian and
Wasserburg follow
The Evolution of Early-Type Galaxies in Distant Clusters II: Internal Kinematics of 55 Galaxies in the z=0.33 Cluster CL1358+62
We define a large sample of galaxies for use in a study of the fundamental
plane in the intermediate redshift cluster CL1358+62 at . We have
analyzed high resolution spectra for 55 members of the cluster. The data were
acquired with the Low Resolution Imaging Spectrograph on the Keck I 10m
telescope. A new algorithm for measuring velocity dispersions is presented and
used to measure the internal kinematics of the galaxies. This algorithm has
been tested against the Fourier Fitting method so the data presented here can
be compared with those measured previously in nearby galaxies. We have measured
central velocity dispersions suitable for use in a fundamental plane analysis.
The data have high and the resulting random errors on the dispersions are
very low, typically . Uncertainties due to mismatch of the stellar
templates has been minimized through several tests and the total systematic
error is of order \about 5%. Good seeing enabled us to measure velocity
dispersion profiles and rotation curves for most of the sample and although a
large fraction of the galaxies display a high level of rotation, the gradients
of the total second moment of the kinematics are all very regular and similar
to those in nearby galaxies. We conclude that the data therefore can be
reliably corrected for aperture size in a manner consistent with nearby galaxy
samples.Comment: 30 pages, 13 figures; for publication in the ApJ (accepted on 23
August 1999
Characterization of constricted fruit (ctf) Mutant Uncovers a Role for AtMYB117/LOF1 in Ovule and Fruit Development in Arabidopsis thaliana
Pistil and fruit morphogenesis is the result of a complex gene network that is not yet fully understood. A search for novel genes is needed to make a more comprehensive model of pistil and fruit development. Screening for mutants with alterations in fruit morphology generated by an activation tagging strategy resulted in the isolation of the ctf (constricted fruit) mutant. It is characterized by a) small and wrinkled fruits, with an enlarged replum, an amorphous structure of the septum and an irregular distribution of ovules and seeds; b) ectopic carpelloid structures in sepals bearing ovule-like structures and c) dwarf plants with curled rosette leaves. The overexpressed gene in ctf was AtMYB117, also named LOF1 (LATERAL ORGAN FUSION1). AtMYB117/LOF1 transcripts were localized in boundary regions of the vegetative shoot apical meristem and leaf primordia and in a group of cells in the adaxial base of petioles and bracts. Transcripts were also detected in the boundaries between each of the four floral whorls and during pistil development in the inner of the medial ridges, the placenta, the base of the ovule primordia, the epidermis of the developing septum and the outer cell layers of the ovule funiculi. Analysis of changes of expression of pistil-related genes in the ctf mutant showed an enhancement of SHATTERPROOF1 (SHP1) and SHP2 expression. All these results suggest that AtMYB117/LOF1 is recruited by a variety of developmental programs for the establishment of boundary regions, including the development of floral organs and the initiation of ovule outgrowth
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