2,215 research outputs found
Black Holes and Vacuum Cleaners: Using Metaphor, Relevance, and Inquiry in Labels for Space Images
This study extended research on the development of explanatory labels for
astronomical images for the non-expert lay public. The research questions
addressed how labels with leading questions/metaphors and relevance to everyday
life affect comprehension of the intended message for deep space images, the
desire to learn more, and the aesthetic appreciation of images. Participants
were a convenience sample of 1,921 respondents solicited from a variety of
websites and through social media who completed an online survey that used four
high-resolution images as stimuli: Sagittarius A*, Solar Flare, Cassiopeia A,
and the Pinwheel Galaxy (M101). Participants were randomly assigned initially
to 1 of 3 label conditions: the standard label originally written for the
image, a label with a leading question containing a metaphor related to the
information for the image, or a label that contained a fact about the image
relevant to everyday life. Participants were randomly assigned to 1 image and
compared all labels for that image. Open-ended items at various points asked
participants to pose questions to a hypothetical astronomer. Main findings were
that the relevance condition was significantly more likely to increase wanting
to learn more; the original label was most likely to increase overall
appreciation; and, smart phone users were more likely to want to learn more and
report increased levels of appreciation. Results are discussed in terms of the
need to examine individual viewer characteristics and goals in creating
different labels for different audiences.Comment: 50 pages, 7 tables, 2 figures, accepted by the journal "Psychology of
Aesthetics, Creativity, and the Arts
The Chandra X-ray Observatory: An Astronomical Facility Available to the World
The Chandra X-ray observatory, one of NASA's "Great Observatories," provides high angular and spectral resolution X-ray data which is freely available to all. In this review I describe the instruments on chandra along with their current calibration, as well as the chandra proposal system, the freely-available Chandra analysis software package CIAO, and the Chandra archive. As Chandra is in its 6th year of operation, the archive already contains calibrated observations of a large range of X-ray sources. The Chandra X-ray Center is committed to assisting astronomers from any country who wish to use data from the archive or propose for observation
The Impact of Accurate Extinction Measurements for X-ray Spectral Models
Interstellar extinction includes both absorption and scattering of photons
from interstellar gas and dust grains, and it has the effect of altering a
source's spectrum and its total observed intensity. However, while multiple
absorption models exist, there are no useful scattering models in standard
X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created
by scattering from dust grains, are detected around even moderately absorbed
sources and the impact on an observed source spectrum can be significant, if
modest, compared to direct absorption. By convolving the scattering cross
section with dust models, we have created a spectral model as a function of
energy, type of dust, and extraction region that can be used with models of
direct absorption. This will ensure the extinction model is consistent and
enable direct connections to be made between a source's X-ray spectral fits and
its UV/optical extinction.Comment: 8 pages, 4 figure
Global Hot Gas in and around the Galaxy
The hot interstellar medium traces the stellar feedback and its role in
regulating the eco-system of the Galaxy. I review recent progress in
understanding the medium, based largely on X-ray absorption line spectroscopy,
complemented by X-ray emission and far-UV OVI absorption measurements. These
observations enable us for the first time to characterize the global spatial,
thermal, chemical, and kinematic properties of the medium. The results are
generally consistent with what have been inferred from X-ray imaging of nearby
galaxies similar to the Galaxy. It is clear that diffuse soft X-ray
emitting/absorbing gas with a characteristic temperature of K
resides primarily in and around the Galactic disk and bulge. In the solar
neighborhood, for example, this gas has a characteristic vertical scale height
of kpc. This conclusion does not exclude the presence of a
larger-scale, probably much hotter, and lower density circum-Galactic hot
medium, which is required to explain observations of various high-velocity
clouds. This hot medium may be a natural product of the stellar feedback in the
context of the galaxy formation and evolution.Comment: 11 pages, invited talk in the workshop "The Local Bubble and Beyond
II
Searching for the 3.5 keV Line in the Stacked Suzaku Observations of Galaxy Clusters
We perform a detailed study of the stacked Suzaku observations of 47 galaxy
clusters, spanning a redshift range of 0.01-0.45, to search for the
unidentified 3.5 keV line. This sample provides an independent test for the
previously detected line. We detect only a 2sigma-significant spectral feature
at 3.5 keV in the spectrum of the full sample. When the sample is divided into
two subsamples (cool-core and non-cool core clusters), cool-core subsample
shows no statistically significant positive residuals at the line energy. A
very weak (2sigma-confidence) spectral feature at 3.5 keV is permitted by the
data from the non-cool core clusters sample. The upper limit on a neutrino
decay mixing angle from the full Suzaku sample is consistent with the previous
detections in the stacked XMM-Newton sample of galaxy clusters (which had a
higher statistical sensitivity to faint lines), M31, and Galactic Center at a
90% confidence level. However, the constraint from the present sample, which
does not include the Perseus cluster, is in tension with previously reported
line flux observed in the core of the Perseus cluster with XMM-Newton and
Suzaku.Comment: ApJ in press, 9 pages, 3 figure
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