539 research outputs found
Electron Detectors for Electron-Beam Testing of Ultra Large Scale Integrated Circuits
The increasing density of components in integrated circuits imposes severe constraints on conventional electron beam testers. The use of electron detectors consisting of combined electrostatic and magnetic fields has demonstrated improved performance over conventional electrostatic detectors. Such detectors also ease many of the practical difficulties associated with electron beam testing of Ultra Large Scale Integration (ULSI) circuits. A detector using a single pole magnetic lens will be described and compared to detectors which use only electrostatic fields. The single pole lens detector has demonstrated superior performance to the electrostatic detector in terms of local field error and imaging resolution, allowing accurate measurements to be made on sub-micron structures
The Magnitude-Size Relation of Galaxies out to z ~ 1
As part of the Deep Extragalactic Evolutionary Probe (DEEP) survey, a sample
of 190 field galaxies (I_{814} <= 23.5) in the ``Groth Survey Strip'' has been
used to analyze the magnitude-size relation over the range 0.1 < z < 1.1. The
survey is statistically complete to this magnitude limit. All galaxies have
photometric structural parameters, including bulge fractions (B/T), from Hubble
Space Telescope images, and spectroscopic redshifts from the Keck Telescope.
The analysis includes a determination of the survey selection function in the
magnitude-size plane as a function of redshift, which mainly drops faint
galaxies at large distances. Our results suggest that selection effects play a
very important role. A first analysis treats disk-dominated galaxies with B/T <
0.5. If selection effects are ignored, the mean disk surface brightness
(averaged over all galaxies) increases by ~1.3 mag from z = 0.1 to 0.9.
However, most of this change is plausibly due to comparing low luminosity
galaxies in nearby redshift bins to high luminosity galaxies in distant bins.
If this effect is allowed for, no discernible evolution remains in the disk
surface brightness of bright (M_B < -19) disk-dominated galaxies. A second
analysis treats all galaxies by substituting half-light radius for disk scale
length, with similar conclusions. Indeed, at all redshifts, the bulk of
galaxies is consistent with the magnitude-size envelope of local galaxies,
i.e., with little or no evolution in surface brightness. In the two highest
redshift bins (z > 0.7), a handful of luminous, high surface brightness
galaxies appears that occupies a region of the magnitude-size plane rarely
populated by local galaxies. Their wide range of colors and bulge fractions
points to a variety of possible origins.Comment: 19 pages, 12 figures. Accepted for publication in the Astrophysical
Journa
The convergence method to calculate particles fluxes in x rays spectrometry techniques. Application in nuclear compounds
A method to calculate particle fluxes applicable in most of the spectroscopy
techniques is described. Flux intensities of backscattered or absorbed
electrons and emitted photons are calculated using a method of convergence to
solve the Invariant Embedding equations that are used to describe the particle
trajectories inside a solid sample. Our results are found to be helpful to
carry out a procedure for quantitative characterization using instrument such
as Electron Probe Microanalysis or other probes. Examples of application to
calculate the composition of ternary alloys are given and are compared with the
same calculations using another procedure.Comment: 15 page
On the "Mandelbrot set" for a pair of linear maps and complex Bernoulli convolutions
We consider the "Mandelbrot set" for pairs of complex linear maps,
introduced by Barnsley and Harrington in 1985 and studied by Bousch, Bandt and
others. It is defined as the set of parameters in the unit disk such
that the attractor of the IFS is
connected. We show that a non-trivial portion of near the imaginary axis is
contained in the closure of its interior (it is conjectured that all non-real
points of are in the closure of the set of interior points of ). Next we
turn to the attractors themselves and to natural measures
supported on them. These measures are the complex analogs of
much-studied infinite Bernoulli convolutions. Extending the results of Erd\"os
and Garsia, we demonstrate how certain classes of complex algebraic integers
give rise to singular and absolutely continuous measures . Next we
investigate the Hausdorff dimension and measure of , for
in the set , for Lebesgue-a.e. . We also obtain partial results on
the absolute continuity of for a.e. of modulus greater
than .Comment: 22 pages, 5 figure
The Color-Magnitude Relation in CL 1358+62 at z=0.33: Evidence for Significant Evolution in the S0 Population
We use a large mosaic of HST WFPC2 images to measure the colors and
morphologies of 194 spectroscopically confirmed members of the rich galaxy
cluster CL1358+62 at z=0.33. We study the color-magnitude (CM) relation as a
function of radius in the cluster. The intrinsic scatter in the restframe B-V
CM relation of the elliptical galaxies is very small: ~0.022 magnitudes. The CM
relation of the ellipticals does not depend significantly on the distance from
the cluster center. In contrast, the CM relation for the S0 galaxies does
depend on radius: the S0s in the core follow a CM relation similar to the
ellipticals, but at large radii (R>0.7Mpc) the S0s are systematically bluer and
the scatter in the CM relation approximately doubles to ~0.043 magnitudes. The
blueing of the S0s is significant at the 95% confidence level. These results
imply that the S0 galaxies in the outer parts of the cluster have formed stars
more recently than the S0s in the inner parts. A likely explanation is that
clusters at z=0.33 continue to accrete galaxies and groups from the field and
that infall extinguishes star formation. The apparent homogeneity of the
elliptical galaxy population implies that star formation in recently accreted
ellipticals was terminated well before accretion occurred. We have constructed
models to explore the constraints that these observations place on the star
formation history of cluster galaxies. We conclude that the population of S0s
in clusters is likely to evolve as star forming galaxies are converted into
passively evolving galaxies. Assuming a constant accretion rate after z=0.33,
we estimate ~15% of the present day early-type galaxy population in rich
clusters was accreted between z=0.33 and z=0. The ellipticals (and the
brightest S0s) are probably a more stable population, at least since z=0.6.Comment: Accepted for publication in the ApJ. 20 pages, 12 figures. Full
version and plates available at http://www.astro.rug.nl/~dokkum/papers.htm
Redshift z ~ 1 Field Galaxies Observed with the Keck Telescope and the HST
We report results based on 35 new spectroscopic redshifts obtained with the
Keck Telescope for field galaxies that also have photometry and morphology from
survey images taken by the refurbished HST. A sample of 24 redshifts for
galaxies fainter than I = 22 has a median redshift of z ~ 0.81. This result is
inconsistent with the lower median redshift of z ~ 0.6 predicted by the
``maximal merger models'' of Carlberg (1996), which otherwise fit existing
data. The data match an extrapolation of the CFRS, as well as predictions of
certain mild luminosity-evolution models. Nearly half of the redshifts lie in
two structures at z ~ 0.81 and z ~ 1.0, showing the presence of high density
concentrations spanning scales of ~ 1/h Mpc, i.e., the size of groups. We find
emission lines or the presence of possible neighbors in 7 of 9 otherwise
luminous galaxies with red central regions at redshifts beyond z ~ 0.7. We also
note a diversity of morphological types among blue galaxies at z ~ 1, including
small compact galaxies, ``chains,'' and ``blue nucleated galaxies.'' These
morphologies are found among local, but generally less luminous, galaxies.
Distant blue galaxies also include apparently normal late-type spirals. These
findings could imply modest bursts of star formation caused by mergers or
interactions of small, gas-rich galaxies with each other or with larger,
well-formed galaxies. This first glimpse of very faint z ~ 1 field galaxies of
diverse colors and morphologies suggests that a mixture of physical processes
is at work in the formation and evolution of faint field galaxies.Comment: 20 pages (31 with table and GIF figures). Full text and postscript
figures are available at http://www.ucolick.org/~nicole/pubs/pubs.html#gs1
and http://tarkus.pha.jhu.edu/deep/publications.html . Accepted by The
Astrophysical Journa
Optical Rotation Curves of Distant Field Galaxies: Sub-L* Systems
Moderate-resolution spectroscopic observations from the Keck 10m telescope
are used to derive internal kinematics for eight faint disk galaxies in the
fields flanking the Hubble Deep Field. The spectroscopic data are combined with
high-resolution F814W WFPC2 images from the Hubble Space Telescope which
provide morphologies and scale-lengths, inclinations and orientations. The
eight galaxies have redshifts 0.15 < z < 0.75, magnitudes 18.6 < I_814 < 22.1
and luminosities -21.8 < M_B < -19.0 (H_0 = 75 and q_0 = 0.05). Terminal disk
velocities are derived from the spatially-resolved velocity profiles by
modeling the effects of seeing, slit width, slit misalignment with galaxy major
axis, and inclination for each source. These data are combined with the sample
of Vogt et al. (1996) to provide a high-redshift Tully-Fisher relation that
spans three magnitudes. This sample was selected primarily by morphology and
magnitude, rather than color or spectral features. We find no obvious change in
the shape or slope of the relation with respect to the local Tully-Fisher
relation. The small offset of < 0.4 B mag with respect to the local relation is
presumably caused by luminosity evolution in the field galaxy population, and
does not correlate with galaxy mass. A comparison of disk surface brightness
between local and high-redshift samples yields a similar offset, ~0.6 mag.
These results provide further evidence for only a modest increase in luminosity
with lookback time.Comment: Text is 9 pages (13 with figures, images in JPG format here for
brevity). Full text and postscript figures are available at
http://www.ucolick.org/~nicole/pubs/pubs.html#vfp2 and
http://tarkus.pha.jhu.edu/deep/publications.html . Accepted for publication
by The Astrophysical Journal Letter
Optical Rotation Curves of Distant Field Galaxies I : Keck Results at Redshifts to z ~ 1
Spatially resolved velocity profiles are presented for nine faint field
galaxies in the redshift range 0.1 < z < 1, based on moderate-resolution
spectroscopy obtained with the Keck 10 m telescope. These data were augmented
with high-resolution HST images from WFPC2, which provided V and I photometry,
galaxy type, orientation, and inclination. The effects of seeing, slit width,
and slit misalignment with respect to galaxy major axis were modeled along with
inclination for each source, in order to derive a maximum circular velocity
from the observed rotation curve. The lowest redshift galaxy, though highly
elongated, shows a distorted low-amplitude rotation curve that suggests a
merger in progress seen perpendicular to the collision path. The remaining
rotation curves appear similar to those of local galaxies in both form and
amplitude, implying that some massive disks were in place at z ~ 1. The key
result is that the kinematics of these distant galaxies show evidence for only
a modest increase in luminosity of delta M_B < 0.6 compared to
velocity-luminosity (Tully-Fisher) relations for local galaxies.Comment: Text is 16 pages (21 with table and figures, in GIF format here for
brevity). Full text and postscript figures are available at
http://www.ucolick.org/~nicole/pubs/pubs.html#vfp and
http://tarkus.pha.jhu.edu/deep/publications.html . Accepted for publication
by The Astrophysical Journal Letter
Strong Lensing Analysis of A1689 from Deep Advanced Camera Images
We analyse deep multi-colour Advanced Camera images of the largest known
gravitational lens, A1689. Radial and tangential arcs delineate the critical
curves in unprecedented detail and many small counter-images are found near the
center of mass. We construct a flexible light deflection field to predict the
appearance and positions of counter-images. The model is refined as new
counter-images are identified and incorporated to improve the model, yielding a
total of 106 images of 30 multiply lensed background galaxies, spanning a wide
redshift range, 1.0z5.5. The resulting mass map is more circular in
projection than the clumpy distribution of cluster galaxies and the light is
more concentrated than the mass within . The projected mass profile
flattens steadily towards the center with a shallow mean slope of
, over the observed range,
r, matching well an NFW profile, but with a relatively high
concentration, . A softened isothermal profile
(\arcs) is not conclusively excluded, illustrating that
lensing constrains only projected quantities. Regarding cosmology, we clearly
detect the purely geometric increase of bend-angles with redshift. The
dependence on the cosmological parameters is weak due to the proximity of
A1689, , constraining the locus, .
This consistency with standard cosmology provides independent support for our
model, because the redshift information is not required to derive an accurate
mass map. Similarly, the relative fluxes of the multiple images are reproduced
well by our best fitting lens model.Comment: Accepted by ApJ. For high quality figures see
http://wise-obs.tau.ac.il/~kerens/A168
The Hubble Space Telescope Extragalactic Distance Scale Key Project. X. The Cepheid Distance to NGC 7331
The distance to NGC 7331 has been derived from Cepheid variables observed
with HST/WFPC2, as part of the Extragalactic Distance Scale Key Project.
Multi-epoch exposures in F555W (V) and F814W (I), with photometry derived
independently from DoPHOT and DAOPHOT/ALLFRAME programs, were used to detect a
total of 13 reliable Cepheids, with periods between 11 and 42 days. The
relative distance moduli between NGC 7331 and the LMC, imply an extinction to
NGC 7331 of A_V = 0.47+-0.15 mag, and an extinction-corrected distance modulus
to NGC 7331 of 30.89+-0.14(random) mag, equivalent to a distance of 15.1 Mpc.
There are additional systematic uncertainties in the distance modulus of +-0.12
mag due to the calibration of the Cepheid Period-Luminosity relation, and a
systematic offset of +0.05+-0.04 mag if we applied the metallicity correction
inferred from the M101 results of Kennicutt et al 1998.Comment: To be published in The Astrophysical Journal, 1998 July 1, v501 note:
Figs 1 and 2 (JPEG files) and Fig 7 (multipage .eps file) need to be
viewed/printed separatel
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