62 research outputs found
Far-Infrared Heterodyne Spectrometer for SOFIA
This report summarizes work done under NASA Grant NAG2-1062 awarded to the University of Colorado. The project goal was to evaluate the scientific capabilities and technical requirements for a far-infrared heterodyne spectrometer suitable for the SOFIA Airborne Observatory, which is now being developed by NASA under contract to the Universities Space Research Association (USRA). The conclusions detailed below include our specific recommendations for astronomical observations, as well as our intended technical approach for reaching these scientific goals. These conclusions were presented to USRA in the form of a proposal to build this instrument. USRA subsequently awarded the University of Colorado a 3-year grant (USRA 8500-98-010) to develop the proposed Hot-Electron micro-Bolometer (HEB) mixer concept for high frequencies above 3 THz, as well as other semiconductor mixer technologies suitable for high sensitivity receivers in the 2-6 THz frequency band
Far Infrared Line Profiles from Photodissociation Regions and Warm Molecular Clouds
This report summarizes the work done under NASA Grant NAG2-1056 awarded to the University of Colorado. The aim of the project was to analyze data obtained over the past several years with the University of Colorado far-infrared heterodyne spectrometer (Betz Boreiko 1993) aboard the Kuiper Airborne Observatory. Of particular interest were observations of CO and ionized carbon (C II) in photodissociation regions (PDRS) at the interface between UV-ionized H II regions and the neutral molecular clouds supporting star formation. These data, obtained with a heterodyne spectrometer having a resolution of 3.2 MHz, which is equivalent to a velocity resolution of 0.2 km/s at 60 microns and 1.0 km/s at 300 microns, were analyzed to obtain physical parameters such as density and temperature in the observed PDR. The publication resulting from the work reported here is appended. No inventions were made nor was any federally owned property acquired as a result of the activities under this grant
Far Infrared Line Profiles from Photodissociation Regions and Warm Molecular Clouds
This report summarizes the work done under NASA Grant NAG2-1056 awarded to the University of Colorado. The aim of the project was to analyze data obtained over the past several years with the University of Colorado far-infrared heterodyne spectrometer aboard the Kuiper Airborne Observatory. Of particular interest were observations of CO and ionized carbon (C II) in photodissociation regions (PDRS) at the interface between UV-ionized H II regions and the neutral molecular clouds supporting star formation. These data, obtained with a heterodyne spectrometer having a resolution of 3.2 MHz, which is equivalent to a velocity resolution of 0.2 km s(exp -1) at 60 microns and 1.0 km s(exp -1) at 300 microns, were analyzed to obtain physical parameters such as density and temperature in the observed PDR
Far Infrared Line Profiles from Photodissociation Regions and Warm Molecular Clouds
This report summarizes the work done under NASA Grant NAG2-1056 awarded to the University of Colorado. The aim of the project was to analyze data obtained over the past several years with the University of Colorado far-infrared heterodyne spectrometer (Betz & Boreiko 1993) aboard the Kuiper Airborne Observatory. Of particular interest were observations of CO and ionized carbon (C II) in photodissociation regions (PDRs) at the interface between UV-ionized H II regions and the neutral molecular clouds supporting star formation. These data, obtained with a heterodyne spectrometer having a resolution of 3.2 MHz, which is equivalent to a velocity resolution of 0.2 km/s at 60 microns and 1.0 km/s at 300 microns, were analyzed to obtain physical parameters such as density and temperature in the observed PDR. The publication resulting from the work reported here is appended. No inventions were made nor was any federally owned property acquired as a result of the activities under this grant
Heterodyne Spectroscopy of the 63 m O I Line in M42
We have used a laser heterodyne spectrometer to resolve the emission line
profile of the 63 micron 3P1 - 3P2 fine-structure transition of O I at two
locations in M42. Comparison of the peak antenna temperature with that of the
158 micron C II fine-structure line shows that the gas kinetic temperature in
the photodissociation region near theta1C is 175 - 220 K, the density is
greater than 2x10 ^5 cm-3, and the hydrogen column density is about 1.5x10 ^22
cm-2. A somewhat lower temperature and column density are found in the IRc2
region, most likely reflecting the smaller UV flux. The observed width of the O
I line is 6.8 km/s (FWHM) at theta1C, which is slightly broadened over the
intrinsic linewidth by optical depth effects. No significant other differences
between the O I and C II line profiles are seen, which shows that the narrow
emission from both neutral atomic oxygen and ionized carbon comes from the PDR.
The O I data do not rule out the possibility of weak broad-velocity emission
from shock-excited gas at IRc2, but the C II data show no such effect, as
expected from non-ionizing shock models.Comment: 11 pages including 2 postscript figures, uses aaspp4.st
The 12C/13C Isotopic Ratio in Photodissociated Gas in M42
We have observed the 158 micron 2P3/2-2P1/2 fine-structure line of 12C II
simultaneously with the F=2-1 and F=1-0 hyperfine components of this transition
in 13C II in the Orion photodissociation region near theta1C . The line
profiles were fully resolved using a heterodyne spectrometer with 0.5 km/s
resolution. The relative intensities of these lines give a 12C/13C isotopic
ratio of R=58 (+6,-5) for the most probable 12C II peak optical depth tau=1.3 .
The constrained range of tau(12C II) between 1.0 and 1.4 corresponds to a range
of 12C/13C between 52 and 61. The most probable value of 58 agrees very well
with that obtained from a relationship between the isotopic ratio and
galactocentric distance derived from CO measurements, but is lower than the
specific value of 67(+-3) obtained for Orion from CO data. An isotopic ratio as
low as 43, as previously suggested based on optical absorption measurements of
the local interstellar medium, is excluded by the C II data at about the 2
sigma level.Comment: 11 pages, 2 postscript figures, uses aaspp4 macro
Mid-J CO emission from the Orion BN/KL explosive outflow
High spatial resolution low-J 12CO observations have shown that the
wide-angle outflow seen in the Orion BN/KL region correlates with the famous H2
fingers. Recently, high-resolution large-scale mappings of mid- and higher-J CO
emissions have been reported toward the Orion molecular cloud 1 core region
using the APEX telescope. Therefore, it is of interest to investigate this
outflow in the higher-J 12CO emission, which is likely excited by shocks. The
observations were carried out using the dual-color heterodyne array CHAMP+ on
the APEX telescope. The images of the Orion BN/KL region were obtained in the
12CO J=6-5 and J=7-6 transitions with angular resolutions of 8.6 and 7.4
arcsec, respectively. The results show a good agreement between our higher-J
12CO emission and SMA low-J 12CO data, which indicates that this wide-angle
outflow in Orion BN/KL is likely the result of an explosive event that is
related to the runaway objects from a dynamically decayed multiple system. From
our observations, we estimate that the kinetic energy of this explosive outflow
is about 1-2x10^47 erg. In addition, a scenario has been proposed where part of
the outflow is decelerated and absorbed in the cloud to explain the lack of CO
bullets in the southern part of BN/KL, which in turn induces the methanol
masers seen in this region.Comment: 5 pages, 4 figure
Muon capture by 3He nuclei followed by proton and deuteron production
The paper describes an experiment aimed at studying muon capture by
nuclei in pure and mixtures at various densities. Energy distributions of
protons and deuterons produced via and are measured for the
energy intervals MeV and MeV, respectively. Muon capture
rates, and are obtained using two different analysis methods. The
least--squares methods gives , . The Bayes theorem
gives ,
. The experimental
differential capture rates, and , are compared with theoretical
calculations performed using the plane--wave impulse approximation (PWIA) with
the realistic NN interaction Bonn B potential. Extrapolation to the full energy
range yields total proton and deuteron capture rates in good agreement with
former results.Comment: 17 pages, 13 figures, accepted for publication in PR
The APEX-CHAMP+ view of the Orion Molecular Cloud 1 core - Constraining the excitation with submillimeter CO multi-line observations
A high density portion of the Orion Molecular Cloud 1 (OMC-1) contains the
prominent, warm Kleinmann-Low (KL) nebula that is internally powered by an
energetic event plus a farther region in which intermediate to high mass stars
are forming. Its outside is affected by ultraviolet radiation from the
neighboring Orion Nebula Cluster and forms the archetypical photon-dominated
region (PDR) with the prominent bar feature. Its nearness makes the OMC-1 core
region a touchstone for research on the dense molecular interstellar medium and
PDRs. Using the Atacama Pathfinder Experiment telescope (APEX), we have imaged
the line emission from the multiple transitions of several carbon monoxide (CO)
isotopologues over the OMC-1 core region. Our observations employed the 2x7
pixel submillimeter CHAMP+ array to produce maps (~ 300 arcsec x 350 arcsec) of
12CO, 13CO, and C18O from mid-J transitions (J=6-5 to 8-7). We also obtained
the 13CO and C18O J=3-2 images toward this region. The 12CO line emission shows
a well-defined structure which is shaped and excited by a variety of phenomena,
including the energetic photons from hot, massive stars in the nearby Orion
Nebula's central Trapezium cluster, active high- and intermediate-mass star
formation, and a past energetic event that excites the KL nebula. Radiative
transfer modeling of the various isotopologic CO lines implies typical H2
densities in the OMC-1 core region of ~10^4-10^6 cm^-3 and generally elevated
temperatures (~ 50-250 K). We estimate a warm gas mass in the OMC-1 core region
of 86-285 solar masses.Comment: 11 pages, 9 figures, accepted by A&
The origin of the [C II] emission in the S140 PDRs - new insights from HIFI
Using Herschel's HIFI instrument we have observed [C II] along a cut through
S140 and high-J transitions of CO and HCO+ at two positions on the cut,
corresponding to the externally irradiated ionization front and the embedded
massive star forming core IRS1. The HIFI data were combined with available
ground-based observations and modeled using the KOSMA-tau model for photon
dominated regions. Here we derive the physical conditions in S140 and in
particular the origin of [C II] emission around IRS1. We identify three
distinct regions of [C II] emission from the cut, one close to the embedded
source IRS1, one associated with the ionization front and one further into the
cloud. The line emission can be understood in terms of a clumpy model of
photon-dominated regions. At the position of IRS1, we identify at least two
distinct components contributing to the [C II] emission, one of them a small,
hot component, which can possibly be identified with the irradiated outflow
walls. This is consistent with the fact that the [C II] peak at IRS1 coincides
with shocked H2 emission at the edges of the outflow cavity. We note that
previously available observations of IRS1 can be well reproduced by a
single-component KOSMA-tau model. Thus it is HIFI's unprecedented spatial and
spectral resolution, as well as its sensitivity which has allowed us to uncover
an additional hot gas component in the S140 region.Comment: accepted for publication in Astronomy and Astrophysics (HIFI special
issue
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