94 research outputs found
Processing Color in Astronomical Imagery
Every year, hundreds of images from telescopes on the ground and in space are
released to the public, making their way into popular culture through
everything from computer screens to postage stamps. These images span the
entire electromagnetic spectrum from radio waves to infrared light to X-rays
and gamma rays, a majority of which is undetectable to the human eye without
technology. Once these data are collected, one or more specialists must process
the data to create an image. Therefore, the creation of astronomical imagery
involves a series of choices. How do these choices affect the comprehension of
the science behind the images? What is the best way to represent data to a
non-expert? Should these choices be based on aesthetics, scientific veracity,
or is it possible to satisfy both? This paper reviews just one choice out of
the many made by astronomical image processors: color. The choice of color is
one of the most fundamental when creating an image taken with modern
telescopes. We briefly explore the concept of the image as translation,
particularly in the case of astronomical images from invisible portions of the
electromagnetic spectrum. After placing modern astronomical imagery and
photography in general in the context of its historical beginnings, we review
the standards (or lack thereof) in making the basic choice of color. We discuss
the possible implications for selecting one color palette over another in the
context of the appropriateness of using these images as science communication
products with a specific focus on how the non-expert perceives these images and
how that affects their trust in science. Finally, we share new data sets that
begin to look at these issues in scholarly research and discuss the need for a
more robust examination of this and other related topics in the future to
better understand the implications for science communications.Comment: 10 pages, 6 figures, published in Studies in Media and Communicatio
Replacement Gastrostomy Tube Causing Acute Pancreatitis: Case Series with Review of Literature
Context Percutaneous endoscopic gastrostomy (PEG) feedings are generally considered safe with few serious complications. Acute pancreatitis is a rare complication associated with replacement percutaneous endoscopic gastrostomy tubes.
Case report We report two cases of acute pancreatitis induced by migrated replacement percutaneous endoscopic gastrostomy tubes.
Conclusions Migration of a balloon into the duodenum can result in external manipulation of the ampulla of Vater thereby disturbing the flow of pancreatic secretions leading to acute pancreatitis. Recognition of this complication is important and should be included as potential etiology of acute pancreatitis in patients receiving percutaneous endoscopic gastrostomy feedings. Periodic examination and documentation of the distance of the balloon from the skin should be performed to document the position of the tubes or any inadvertent migration of the tubes. The use of Foley catheters as permanent replacement tubes should be considered medically inappropriate
High Energy Vision: Processing X-rays
Astronomy is by nature a visual science. The high quality imagery produced by the world’s observatories can be a key to effectively engaging with the public and helping to inspire the next generation of scientists. Creating compelling astronomical imagery can, however, be particularly challenging in the non-optical wavelength regimes. In the case of X-ray astronomy, where the amount of light available to create an image is severely limited, it is necessary to employ sophisticated image processing algorithms to translate light beyond human vision into imagery that is aesthetically pleasing while still being scientifically accurate. This paper provides a brief overview of the history of X-ray astronomy leading to the deployment of NASA’s Chandra X-ray Observatory, followed by an examination of the specific challenges posed by processing X-ray imagery. The authors then explore image processing techniques used to mitigate such processing challenges in order to create effective public imagery for X-ray astronomy. A follow-up paper to this one will take a more in-depth look at the specific techniques and algorithms used to produce press-quality imagery
The SMC SNR 1E0102.2-7219 as a Calibration Standard for X-ray Astronomy in the 0.3-2.5 keV Bandpass
The flight calibration of the spectral response of CCD instruments below 1.5
keV is difficult in general because of the lack of strong lines in the on-board
calibration sources typically available. We have been using 1E 0102.2-7219, the
brightest supernova remnant in the Small Magellanic Cloud, to evaluate the
response models of the ACIS CCDs on the Chandra X-ray Observatory (CXO), the
EPIC CCDs on the XMM-Newton Observatory, the XIS CCDs on the Suzaku
Observatory, and the XRT CCD on the Swift Observatory. E0102 has strong lines
of O, Ne, and Mg below 1.5 keV and little or no Fe emission to complicate the
spectrum. The spectrum of E0102 has been well characterized using
high-resolution grating instruments, namely the XMM-Newton RGS and the CXO
HETG, through which a consistent spectral model has been developed that can
then be used to fit the lower-resolution CCD spectra. We have also used the
measured intensities of the lines to investigate the consistency of the
effective area models for the various instruments around the bright O (~570 eV
and 654 eV) and Ne (~910 eV and 1022 eV) lines. We find that the measured
fluxes of the O VII triplet, the O VIII Ly-alpha line, the Ne IX triplet, and
the Ne X Ly-alpha line generally agree to within +/-10 % for all instruments,
with 28 of our 32 fitted normalizations within +/-10% of the RGS-determined
value. The maximum discrepancies, computed as the percentage difference between
the lowest and highest normalization for any instrument pair, are 23% for the O
VII triplet, 24% for the O VIII Ly-alpha line, 13% for the Ne IX triplet, and
19% for the Ne X Ly-alpha line. If only the CXO and XMM are compared, the
maximum discrepancies are 22% for the O VII triplet, 16% for the O VIII
Ly-alpha line, 4% for the Ne IX triplet, and 12% for the Ne X Ly-alpha line.Comment: 16 pages, 11 figures, to be published in Proceedings of the SPIE
7011: Space Telescopes and Instrumentation II: Ultraviolet to Gamma Ray 200
The Three-Dimensional Expansion of the Ejecta from Tycho's Supernova Remnant
We present the first three-dimensional measurements of the velocity of
various ejecta knots in Tycho's supernova remnant, known to result from a Type
Ia explosion. Chandra X-ray observations over a 12-year baseline from 2003 to
2015 allow us to measure the proper motion of nearly 60 "tufts" of Si-rich
ejecta, giving us the velocity in the plane of the sky. For the line of sight
velocity, we use two different methods: a non-equilibrium ionization model fit
to the strong Si and S lines in the 1.2-2.8 keV regime, and a fit consisting of
a series of Gaussian lines. These methods give consistent results, allowing us
to determine the red or blue shift of each of the knots. Assuming a distance of
3.5 kpc, we find total velocities that range from 2400 to 6600 km s,
with a mean of 4430 km s. We find several regions where the ejecta knots
have overtaken the forward shock. These regions have proper motions in excess
of 6000 km s. Some Type Ia supernova explosion models predict a velocity
asymmetry in the ejecta. We find no such velocity asymmetries in Tycho, and
discuss our findings in light of various explosion models, favoring those
delayed detonation models with relatively vigorous and symmetrical
deflagrations. Finally, we compare measurements with models of the remnant's
evolution that include both smooth and clumpy ejecta profiles, finding that
both ejecta profiles can be accommodated by the observations.Comment: Accepted for publication in ApJ. Some figures slightly degraded to
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