759 research outputs found
A Comparison of Ultraviolet, Optical, and X-Ray Imagery of Selected Fields in the Cygnus Loop
During the Astro-1 and Astro-2 Space Shuttle missions in 1990 and 1995, far
ultraviolet (FUV) images of five 40' diameter fields around the rim of the
Cygnus Loop supernova remnant were observed with the Ultraviolet Imaging
Telescope (UIT). These fields sampled a broad range of conditions including
both radiative and nonradiative shocks in various geometries and physical
scales. In these shocks, the UIT B5 band samples predominantly CIV 1550 and the
hydrogen two-photon recombination continuum. Smaller contri- butions are made
by emission lines of HeII 1640 and OIII] 1665. We present these new FUV images
and compare them with optical Halpha and [OIII], and ROSAT HRI X-ray images.
Comparing the UIT images with those from the other bands provides new insights
into the spatial variations and locations of these different types of emission.
By comparing against shock model calculations and published FUV spectroscopy at
select locations, we surmise that resonance scattering in the strong FUV
permitted lines is widespread in the Cygnus Loop, especially in the bright
optical filaments typically selected for observation in most previous studies.Comment: 21 pages with 10 figures. See http://www.pha.jhu.edu/~danforth/uit/
for full-resolution figure
Statistical summary of air quality data for metropolitian Cleveland, Ohio, 1967 - 1972: Total suspended particulates, nitrogen dioxide, and sulfur dioxide
Air-quality data for metropolitan Cleveland, Ohio, from 1967 through 1972 were collated and statistically analyzed. Total suspended particulates (TSP) departed from lognormal distribution in 1972. Nitrogen dioxide and sulfur dioxide, departed significantly from lognormal distributions in 1972. In Cleveland the Ohio standards were not met. However, the data indicate a general improvement in air quality. Unusually high precipitation (43% above the average in 1972) may be responsible in lowering these values from the 1971 levels. The mean values of TSP, NO2, and SO2 are 104, 191, and 83 microgram/cu m respectively
ASCA Observations of the Supernova Remnant IC 443: Thermal Structure and Detection of Overionized Plasma
We present the results of X-ray spatial and spectral studies of the
``mixed-morphology'' supernova remnant IC 443 using ASCA. IC 443 has a
center-filled image in X-ray band, contrasting with the shell-like appearance
in radio and optical bands. The overall X-ray emission is thermal, not from a
synchrotron nebula. ASCA observed IC 443 three times, covering the whole
remnant. From the image analysis, we found that the softness-ratio map reveals
a shell-like structure. At the same time, its spectra require two (1.0 keV and
0.2 keV) plasma components; the emission of the 0.2 keV plasma is stronger in
the region near the shell than the center. These results can be explained by a
simple model that IC 443 has a hot (1.0 keV) interior surrounded by a cool (0.2
keV) outer shell. From the emission measures, we infer that the 0.2 keV plasma
is denser than the 1.0 keV plasma, suggesting pressure equilibrium between the
two. In addition, we found that the ionization temperature of sulfur, obtained
from H-like K to He-like K intensity ratio, is 1.5 keV,
significantly higher than the gas temperature of 1.0 keV suggested from the
continuum spectrum. The same can be concluded for silicon. Neither an
additional, hotter plasma component nor a multi-temperature plasma successfully
accounts for this ratio, and we conclude that the 1.0 keV plasma is
overionized. This is the first time that overionized gas has been detected in a
SNR. For the gas to become overionized in the absence of a photoionizing flux,
it must cool faster than the ions recombine. Thermal conduction from the 1.0
keV plasma to the 0.2 keV one could cause the 1.0 keV plasma to become
overionized, which is plausible within an old (3 yr) SNR.Comment: 11 pages, 15 figures, 2 tables, accepted for publication in The
Astrophysical Journa
XMM-Newton observations of the supernova remnant IC443: I. soft X-ray emission from shocked interstellar medium
The shocked interstellar medium around IC443 produces strong X-ray emission
in the soft energy band (E<1.5 keV). We present an analysis of such emission as
observed with the EPIC MOS cameras on board the XMM-Newotn observatory, with
the purpose to find clear signatures of the interactions with the interstellar
medium (ISM) in the X-ray band, which may complement results obtained in other
wavelenghts. We found that the giant molecular cloud mapped in CO emission is
located in the foreground and gives an evident signature in the absorption of
X-rays. This cloud may have a torus shape and the part of torus interacting
with the IC443 shock gives rise to 2MASS-K emission in the southeast. The
measured density of emitting X-ray shocked plasma increases toward the
northeastern limb, where the remnant is interacting with an atomic cloud. We
found an excellent correlation between emission in the 0.3-0.5 keV band and
bright optical/radio filament on large spatial scales. The partial shell
structure seen in this band therefore traces the encounter with the atomic
cloud.Comment: 10 pages, 10 figures, accepted for publication in ApJ (20 September
2006, v649). For hi-res figures, see
http://www.astropa.unipa.it/Library/OAPA_preprints/ic443ele1.ps.g
Preliminary analysis of an extensive one year survey of trace elements and compounds in the suspended particulate matter in Cleveland, Ohio
Beginning in 1971 a cooperative program has been carried on by the City of Cleveland Division of Air Pollution Control and NASA Lewis Research Center to study the trace element and compound concentrations in the ambient suspended particulate matter in Cleveland Ohio as a function of source, monitoring location and meteorological conditions. The major objectives were to determine the ambient concentration levels at representative urban sites and to develop a technique using trace element and compound data in conjunction with meteorological conditions to identify specific pollution sources which could be developed into a practical system that could be readily utilized by an enforcement agency
Comparing Galaxy Morphology at Ultraviolet and Optical Wavelengths
We have undertaken an imaging survey of 34 nearby galaxies in far-ultraviolet
(FUV, ~1500A) and optical (UBVRI) passbands to characterize galaxy morphology
as a function of wavelength. This sample, which includes a range of classical
Hubble types from elliptical to irregular with emphasis on spirals at low
inclination angle, provides a valuable database for comparison with images of
high-z galaxies whose FUV light is redshifted into the optical and near-
infrared bands. Ultraviolet data are from the UIT Astro-2 mission. We present
images and surface brightness profiles for each galaxy, and we discuss the
wavelength-dependence of morphology for different Hubble types in the context
of understanding high-z objects. In general, the dominance of young stars in
the FUV produces the patchy appearance of a morphological type later than that
inferred from optical images. Prominent rings and circumnuclear star formation
regions are clearly evident in FUV images of spirals, while bulges, bars, and
old, red stellar disks are faint to invisible at these short wavelengths.
However, the magnitude of the change in apparent morphology ranges from
dramatic in early--type spirals with prominent optical bulges to slight in
late-type spirals and irregulars, in which young stars dominate both the UV and
optical emission. Starburst galaxies with centrally concentrated, symmetric
bursts display an apparent ``E/S0'' structure in the FUV, while starbursts
associated with rings or mergers produce a peculiar morphology. We briefly
discuss the inadequacy of the optically-defined Hubble sequence to describe FUV
galaxy images and estimate morphological k-corrections, and we suggest some
directions for future research with this dataset.Comment: Accepted for publication in the ApJS. 15 pages, 17 JPEG figures, 10
GIF figures. Paper and full resolution figures available at
http://nedwww.ipac.caltech.edu/level5/Kuchinski/frames.htm
Isolated X-ray -- infrared sources in the region of interaction of the supernova remnant IC 443 with a molecular cloud
The nature of the extended hard X-ray source XMMU J061804.3+222732 and its
surroundings is investigated using XMM-Newton, Chandra, and Spitzer
observations. This source is located in an interaction region of the IC 443
supernova remnant with a neighboring molecular cloud. The X-ray emission
consists of a number of bright clumps embedded in an extended structured
non-thermal X-ray nebula larger than 30" in size. Some clumps show evidence for
line emission at ~1.9 keV and ~3.7 keV at the 99% confidence level. Large-scale
diffuse radio emission of IC 443 passes over the source region, with an
enhancement near the source. An IR source of about 14" x 7" size is prominent
in the 24 um, 70 um, and 2.2 um bands, adjacent to a putative Si K-shell X-ray
line emission region. The observed IR/X-ray morphology and spectra are
consistent with those expected for J/C-type shocks of different velocities
driven by fragmented supernova ejecta colliding with the dense medium of a
molecular cloud. The IR emission of the source detected by Spitzer can be
attributed to both continuum emission from an HII region created by the ejecta
fragment and line emission excited by shocks. This source region in IC 443 may
be an example of a rather numerous population of hard X-ray/IR sources created
by supernova explosions in the dense environment of star-forming regions.
Alternative Galactic and extragalactic interpretations of the observed source
are also discussed.Comment: The Astrophysical Journal, v. 677 (April 2008), in pres
The Ultraviolet Imaging Telescope: Instrument and Data Characteristics
The Ultraviolet Imaging Telescope (UIT) was flown as part of the Astro
observatory on the Space Shuttle Columbia in December 1990 and again on the
Space Shuttle Endeavor in March 1995. Ultraviolet (1200-3300 Angstroms) images
of a variety of astronomical objects, with a 40 arcmin field of view and a
resolution of about 3 arcsec, were recorded on photographic film. The data
recorded during the first flight are available to the astronomical community
through the National Space Science Data Center (NSSDC); the data recorded
during the second flight will soon be available as well. This paper discusses
in detail the design, operation, data reduction, and calibration of UIT,
providing the user of the data with information for understanding and using the
data. It also provides guidelines for analyzing other astronomical imagery made
with image intensifiers and photographic film.Comment: 44 pages, LaTeX, AAS preprint style and EPSF macros, accepted by PAS
- …