8,631 research outputs found
--PhotoZ: Photometric Redshifts by Inverting the Tolman Surface Brightness Test
Surface brightness is a fundamental observational parameter of galaxies. We
show, for the first time in detail, how it can be used to obtain photometric
redshifts for galaxies, the -PhotoZ method.
We demonstrate that the Tolman surface brightness relation, , is a powerful tool for determining galaxy redshifts from
photometric data.
We develop a model using and a color percentile (ranking) measure to
demonstrate the -PhotoZ method. We apply our method to a set of galaxies
from the SHELS survey, and demonstrate that the photometric redshift accuracy
achieved using the surface brightness method alone is comparable with the best
color-based methods.
We show that the -PhotoZ method is very effective in determining the
redshift for red galaxies using only two photometric bands. We discuss the
properties of the small, skewed, non-gaussian component of the error
distribution.
We calibrate from the SDSS to redshift, and tabulate the
result, providing a simple, but accurate look up table to estimate the redshift
of distant red galaxies.Comment: Accepted for publication in the Astronomical Journa
Multi-Epoch Observations of HD69830: High Resolution Spectroscopy and Limits to Variability
The main-sequence solar-type star HD69830 has an unusually large amount of
dusty debris orbiting close to three planets found via the radial velocity
technique. In order to explore the dynamical interaction between the dust and
planets, we have performed multi-epoch photometry and spectroscopy of the
system over several orbits of the outer dust. We find no evidence for changes
in either the dust amount or its composition, with upper limits of 5-7% (1
per spectral element) on the variability of the {\it dust spectrum}
over 1 year, 3.3% (1 ) on the broad-band disk emission over 4 years,
and 33% (1 ) on the broad-band disk emission over 24 years. Detailed
modeling of the spectrum of the emitting dust indicates that the dust is
located outside of the orbits of the three planets and has a composition
similar to main-belt, C-type asteroids asteroids in our solar system.
Additionally, we find no evidence for a wide variety of gas species associated
with the dust. Our new higher SNR spectra do not confirm our previously claimed
detection of HO ice leading to a firm conclusion that the debris can be
associated with the break-up of one or more C-type asteroids formed in the dry,
inner regions of the protoplanetary disk of the HD69830 system. The modeling of
the spectral energy distribution and high spatial resolution observations in
the mid-infrared are consistent with a 1 AU location for the emitting
material
Monte Carlo Generation of Bohmian Trajectories
We report on a Monte Carlo method that generates one-dimensional trajectories
for Bohm's formulation of quantum mechanics that doesn't involve
differentiation or integration of any equations of motion. At each time,
t=n\delta t (n=1,2,3,...), N particle positions are randomly sampled from the
quantum probability density. Trajectories are built from the sorted N sampled
positions at each time. These trajectories become the exact Bohm solutions in
the limits N->\infty and \delta t -> 0. Higher dimensional problems can be
solved by this method for separable wave functions. Several examples are given,
including the two-slit experiment.Comment: 10 pages, 6 figure
Radiation effects on silicon solar cells Final report, Dec. 1, 1961 - Dec. 31, 1962
Displacement defects in silicon solar cells by high energy electron irradiation using electron spin resonance, galvanometric, excess carrier lifetime, and infrared absorption measurement
Attitudes Toward Breast Cancer Genetic Testing in Five Special Population Groups
Purpose: This study examined interest in and attitudes toward genetic testing in 5 different population groups.
Methods: The survey included African American, Asian American, Latina, Native American, and Appalachian women with varying familial histories of breast cancer. A total of 49 women were interviewed in person. Descriptive and nonparametric statistical techniques were used to assess ethnic group differences.
Results: Overall, interest in testing was high. All groups endorsed more benefits than risks. There were group differences regarding endorsement of specific benefits and risks: testing to “follow doctor recommendations” (p=0.017), “concern for effects on family” (p=0.044), “distrust of modern medicine” (p=0.036), “cost” (p=0.025), and “concerns about communication of results to others” (p=0.032). There was a significant inverse relationship between interest and genetic testing cost (p
Conclusion: Cost may be an important barrier to obtaining genetic testing services, and participants would benefit by genetic counseling that incorporates the unique cultural values and beliefs of each group to create an individualized, culturally competent program. Further research about attitudes toward genetic testing is needed among Asian Americans, Native Americans, and Appalachians for whom data are severely lacking. Future study of the different Latina perceptions toward genetic testing are encouraged
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