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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1994

Radio continuum and far-infrared observations of low surface brightness galaxies

We present Very Large Array (VLA) radio continuum and Infrared Astronomy Satellite (IRAS) far-infrared (FIR) observations of 16 low luminosity galaxies of mostly low surface brightness. All galaxies had previously claimed single dish radio continuum detections. However, at the frequencies of our observations (1.49 and 8.48 GHz), we find significant radio emission for two objects only. We show that the other previously claimed detections are due to confusion with physically unrelated background sources. This implies a low radio continuum detection rate for these galaxies. Re-reduced IRAS scans yield significant far-infrared flux densities in at least one IRAS band for 6 of the 16 galaxies. These, together with the FIR and radio continuum upper limits, are consistent with the well established radio/FIR relation, where most of our galaxies populate the low-luminosity end. From the radio continuum and FIR flux densities and their upper limits we estimate the current star formation rates and demonstrate that the galaxies are currently passive in forming stars, in agreement with previous optical investigations. There is an indication that the galaxies were forming stars more intensively averaged over their lifetime than they are presently.

Hoeppe, G.↗
NASA NTRS1994

The origin of the far-infrared luminosity within the spiral galaxy M101

High resolution 60 and 100 micron images obtained with the Infared Astronomical Satellite (IRAS) are compared with H alpha images in order to investigate the origin of the far-infrared luminosity within the late-type spiral galaxy M101. There is a good correspondence between the far-infrared and H-alpha morphology. The far-infrared and H-alpha luminosities have been measured at 129 independent locations on the star forming disk of M101. After correcting the H-alpha luminosity for extinction and extrapolating the IRAS (40-120 microns) luminosity to 1000 microns we find that the far-infrared luminosity is commensurate with that expected from the O and B stars which are required to ionize the hydrogen gas, at all locations within M101. Additionally, the IRAS HiRes 60 and 100 micron images reveal that the dust temperature peaks coincide identically with the location of H II regions. The far-infrared luminosity of M101 is radiated primarily by dust with temperatures well in excess of that expected for cirrus, but similar to that observed for Galactic and extragalactic H II regions.

Devereux, Nicholas A.↗
NASA NTRS1990

Evidence against a simple two-component model for the far-infrared emission from galaxies

Two of the first Infrared Astronomy Satellite (IRAS) results were that galaxies have a wide range of values for the ratio of 60 micron to 100 micron flux density (0.2 less than or equal to S sub 60/S sub 100 less than or equal to 1.0) and that this ratio is correlated with L sub fir, L sub b, L sub fir being the total far-infrared luminosity and L sub b being the luminosity at visible wavelengths (de Jong et al. 1984; Soifer et al. 1984). From these results arose the following simple model for the far-infrared emission from galaxies (de Jong et al. 1984), which has remained the standard model ever since. In this model, the far-infrared emission comes from two dust components: warm dust (T approx. equals 50 K) intermingled with, and heated by, young massive OB stars in molecular clouds and HII regions, and colder dust (T approx. equals 20 K) associated with the diffuse atomic hydrogen in the interstellar medium and heated by the general interstellar radiation field. As the number of young stars in a galaxy increases, S sub 60/S sub 100 increases, because there is a greater proportion of warm dust, and so does L sub fir/L sub b, because most of the radiation from the young stars is absorbed by the dust, leading to a swifter increase in far-infrared emission than in visible light. Although this model explains the basic IRAS results, it is inelegant. It uses two free parameters to fit two data (the 60 and 100 micron flux densities)-and there are now several observations that contradict it. Despite these major problems with the two-component model, it is not clear what should be put in its place. When considering possible models for the far-infrared emission from galaxies, the observational evidence for our own galaxy must be considered. Researchers suspect that the study by Boulanger and Perault (1988) of the far-infrared properties of the local interstellar medium may be particularly relevant. They showed that molecular clouds are leaky - that most of the light from OB stars in molecular clouds does not heat the dust in the clouds, but instead leaks out. The consequence of this is that that while most of the far-infrared emission from the solar neighborhood is from dust associated with diffuse HI, this dust is mostly heated by young stars.

Eales, Stephen A.↗
NASA NTRS1986

Far-infrared properties of optically selected quasars

The far-infrared properties of 10, optically selected quasars were studied on the basis of pointed IRAS observations and ground-based near-infrared and radio measurements. Nine of these quasars were detected in at least three IRAS bands. The flat spectral energy distributions characterizing these optically selected quasars together with large 60-100-micron luminosities suggest that the infrared emission is dominated by nonthermal radiation. Seven of the nine quasars with far-infrared detections were found to have low-frequency turnovers.

Edelson, R. A.↗
NASA NTRS1984

Far-infrared studies of Herbig-Haro objects and their exciting stars

Far-infrared (40-160 micron) observations of Herbig-Haro objects and their probable exciting stars are presented. The importance of these far-infrared observations is epitomized by the fact that, on average, 70 percent of the bolometric luminosity of a typical candidate star is radiated beyond the longest detected ground-based wavelength, even for those objects observed out to 20 micron from the ground. Extended far-infrared emission characterizes some of these regions. Some Herbig-Haro nebulae are themselves conspicuous 100 micron peaks (e.g., HH 1 and HH 25). A bipolar structure is found at 100 micron in the vicinity of the Cohen-Schwartz star. All the exciting stars must be low-mass objects (approximately less than 3 solar mass). It is argued that they might be approximately 1 solar mass protostars still in their accretion phase.

Cohen, M.↗
NASA NTRS1979

Far-infrared observations of the Carina I and II H II regions

Far-infrared (35-175 microns) mapping and photometry are presented of the Carina I and II H II regions in the Carina Nebula (NGC 3372). The far-infrared source associated with Carina I has a half-power width of 2.7 arcmin and has no compact high-surface-brightness condensations, unlike many northern H II regions such as W51 or W49. The peak emission region is offset from the radio continuum peak in the direction of a dust lane to the west. It is proposed that the H II regions and far-IR source are both powered by the O-star cluster Tr 14 about 4 arcmin to the east. The H II region then represents an ionization front at the boundary of the dense cloud west of Tr 14, and the far-infrared emission is due to thermal radiation from the heated dust in the dark cloud. A similar model may also be applicable to the Carina II region.

Harvey, P. M.↗
NASA NTRS1988

Far-infrared observations of a luminous dust-shrouded source in the nucleus of NGC 4945

High-resolution far-infrared observations of the galaxy NGC 4945 have been obtained from the Kuiper Airborne Observatory. Using new observational techniques and nonlinear deconvolution routines, it is found that virtually all of the far-infrared luminosity originates from a nuclear source no larger than 12 arcsec x 9 arcsec (225 pc x 170 pc) in extent. This size constraint, coupled with the far-infrared dust temperature, indicates that the source is deeply embedded in dust: the lower limit for the 100 micron optical depth is 0.35, which is by far the largest yet measured in an external galaxy. Published optical spectra of NGC 4945 reveal a heavily obscured nonthermal source which exhibits broad line profiles typical of a Seyfert 2 active nucleus; it is concluded that the far-infrared emission is probably due to thermal radiation from dust grains surrounding the nonthermal nuclear source. A compact cluster of massive young stars may also contribute to the infrared luminosity, but the evidence for such star-forming activity is weak.

Brock, David↗
NASA NTRS1995

Smithsonian stratospheric far-infrared spectrometer and data reduction system

The Smithsonian far-infrared spectrometer (FIRS) is a remote sensing Fourier transform spectrometer that measures the mid- and far-infrared thermal emission spectrum of the stratosphere from balloon and aircraft platforms. The spectrometer has had nine successful balloon flights from 1987 to 1994, flying at float altitudes of 36 - 39 km and collecting 131 hours of midlatitude stratospheric limb spectra. The spectrometer also flew on a NASA CD-8 aircraft, as part of the second Airborne Arctic Stratospheric Expedition (AASE-2), collecting 140 hours of overhead spectra at latitudes ranging from the equator to the north pole. We present here a brief description of the instrument, a discussion of data reduction procedures, an estimation of both random and systematic errors, an outline of the procedure for retrieving mixing ratio profiles, and an explanation of the method of deriving temperature and pressure from the far- and mid-infrared spectra.

Johnson, D. G.↗
NASA NTRS1984

High Sensitivity, High Angular Resolution Far-infrared Photometry from the KAO

Most of the luminosity of embedded sources is reemitted in the far-infrared continuum. Measurements in the far-infrared are essential to understand the energetics of the interstellar medium, and of star formation regions in particular. Measurements from the KAO, are made in diffraction limited beams that sample a spatial scale considerably smaller than that given by IRAS. The KAO instrument technology has matured to the point that the single scan limiting flux of IRAS at 100 micro can be reached in a diffraction limited beam in a single typical KAO observing leg. The far-infrared photometer system and selections of recent observations are presented.

Lester, D.↗
NASA NTRSDate not supplied

Parallel Plate Capacitor Aluminum KIDs for Future Far-Infrared Space-Based Observatories

Future space-based far-infrared astrophysical observatories will require exquisitely sensitive detectors consistent with the low optical backgrounds. The PRobe far-Infrared Mission for Astrophysics (PRIMA) will deploy arrays of thousands of superconducting kinetic inductance detectors (KIDs) sensitive to radiation between 25 and 265 μm. Here, we present laboratory characterization of prototype, 25 – 80 μm wavelength, low-volume, aluminum KIDs designed for the low-background environment expected with PRIMA. A compact parallel plate capacitor is used to minimize the detector footprint and suppress TLS noise. A novel resonant absorber is designed to enhance response in the band of interest. We present noise and optical efficiency measurements of these detectors taken with a low background cryostat and a cryogenic blackbody. A microlens-hybridized KID array is found to be photon noise limited down to about 50 aW with a limiting detector NEP of about 6.5×10 −19 W/Hz 1/2 . A fit to an NEP model shows that our optical system is well characterized and understood down to 50 aW. We discuss future plans for low-volume aluminum KID array development as well as the testbeds used for these measurements.

Far-Infrared↗
NASA NTRS1989

The far-infrared structure of the luminous interacting galaxy Arp 299

The strongly interacting galaxies NGC 3690 and IC 694 (or Arp 299) exhibit extensive star formation, a large infrared luminosity, and possible nuclear activity. To determine the origin of the infrared luminosity in this system, high-resolution far-infrared profiles have been obtained in which two distinct sources can clearly be discerned; these observations reveal that 60 percent of the far-infrared luminosity comes from an unresolved source in the center of IC 694, with the remaining 40 percent originating in a compact source in NGC 3690. A new high-resolution 20-micron image of the Arp 299 system is compared with the far-infrared profiles, revealing that NGC 3690 is substantially hotter than IC 694 in the thermal infrared; the observed temperature gradient is opposite to that which is expected if the putative active nucleus in IC 694 generates a significant fraction of the total luminosity.

Joy, Marshall↗
NASA NTRS1976

Far-infrared observations of M20 /NGC 6514/

A far-infrared map of M20 shows a total flux of 26 kJy at an effective wavelength of 69 microns and a size of 8 arcmin FWHM. In the region near M20, two compact far-infrared sources were also detected; one source coincides with W28 C, and the other is not identified with any radio source.

Wright, E. L.↗
NASA NTRS1995

Far-Infrared Water Line Emissions from Circumstellar Outflows

We have modeled the far-infrared water line emission expected from circumstellar outflows from oxygen-rich late-type stars, as a function of the mass-loss rate and the terminal outflow velocity. For each mass-loss rate and terminal outflow velocity considered, we computed self-consistently the gas density, temperature, outflow velocity, and water abundance as a function of distance from the star. We then used an escape probability method to solve for the equilibrium level populations of 80 rotational states of water and thereby obtained predictions for the luminosity of a large number of far-infrared rotational transitions of water. In common with previous models, our model predicts that water will be copiously produced in the warm circumstellar gas and that water rotational emission will dominate the radiative cooling. However, our use of a realistic radiative cooling function for water leads to a lower gas temperature than that predicted in previous models. Our predictions for the far-infrared water line luminosities are consequently significantly smaller than those obtained in previous studies. Observations to be carried out by the Infrared Space Observatory will provide a crucial test of the models presented here.

Chen, Wesley↗
NASA NTRS1995

The distribution of far-infrared light in the 'Dusty Hand' galaxy NGC 2146

The Kuiper Airborne Observatory (KAO) has been used to obtain high spatial resolution 50 and 100 micrometers observations of the peculiar galaxy NGC 2146. We find that the far-infrared luminosity of NGC 2146 arises in a 21 arcsecs x less than or = 16 arcsecs (1.5 kpc x less than or equal 1.1 kpc) region (FWHM) elongated along the major axis. This limit is consistent with the size of the central radio continuum and (12)CO (1-0) sources. The far-infrared distribution is slightly more compact than that of the H-alpha; this difference is consistent with observed pattern of extinction in this galaxy. From a study of the energetics in this galaxy, we conclude that young massive stars are largely responsible for powering the far-infrared luminosity of NGC 2146. The far-infrared and CO (1-0) distributions differ from the reddening morphology as seen in optical images and in the Br-gamma/H-alpha ratio. The starlight and the ionized gas appear most highly reddened at the prominent dust lane 15 arcsecs to the west of the nucleus, while the CO and far-infrared emission peak near the nucleus. This result dust lane lies in front of the main body of the galaxy.

Smith, Beverly J.↗
NASA NTRS2004

Arrays of Bolometers for Far-infrared and Submillimeter Astronomy

We describe 12 x 32 arrays of semiconducting cryogenic bolometers designed for use in far-infrared and submillimeter cameras. These 12 x 32 arrays are constructed from 1 x 32 monolithic pop-up detectors developed at NASA Goddard Space Flight Center. The pop-up technology allows the construction of large arrays with high filling factors that provide efficient use of space in the focal planes of far-infrared and submillimeter astronomical instruments. This directly leads to a significant decrease in observing time. The prototype array is currently operating in SHARC II, a facility instrument in use at the Caltech Submillimeter Observatory (CSO). The elements of this array employ a bismuth absorber coating and quarter wave backshort to optimize the bolometer absorption for a passband centered at 350 microns. However, this resonant structure also provides good bolometer performance at 450 and 850 microns, the two additional SHARC II passbands. A second array is to be installed in the High-resolution Airborne Widebandwidth Camera (HAWC), a far-infrared imaging camera for the Stratospheric Observatory for Infrared Astronomy (SOFIA). This array is currently in the final stage of construction, and its completion is expected in early 2004. HAWC is scheduled for commissioning in 2005. The HAWC array employs titanium-gold absorbers and is optimized for uniform absorption from 40 to 300 microns to accommodate all four of its far-infrared passbands. We describe the details of the array construction including the mechanical design and electrical characterization of the constituent linear arrays, comparing the SHARC II and HAWC cases. We also summarize the overall characteristics of the final two-dimensional arrays. Finally, we show examples of array performance in the form of images obtained with SHARC II.

Chuss, D. T.↗
NASA NTRS1987

Radio continuum, far infrared and star formation

A very tight correlation was found between the radio emission and the far infrared emission from galaxies. This has been found for various samples of galaxies and is explained in terms of recent star formation. The tight correlation would imply that the total radio emission is a good tracer of star formation. The correlation between the radio power at 5 GHz and the far infrared luminosity is shown. The galaxies are of various morphological types and were selected from the various IRAS circulars, hence the sample is an infrared selected sample. The far infrared luminosities were corrected for the dust temperature. This is significant because it decreases the dispersion in the correlation.

Wielebinski, R.↗
NASA NTRS1984

Far-infrared observations of galactic nuclei

Measurements of far-infrared continuum emission from the central regions of 30 late-type galaxies, 24 of which were previously unreported, are given. Photometry covering wavelengths from 40 to 160 microns has been obtained, yielding information on luminosities, temperatures, and dust masses for most. Good correlations of the far-infrared luminosity with blue colors, reddening, and molecular line radiation are found, supporting the identification of the sources with the molecular cloud component in these galaxies, and strengthening the identification of the energy sources as the young massive stars formed from those clouds. Comparisons with 10-micron data indicate that such data are useful for statistical studies, but have too much scatter to use directly in the analysis of individual sources. Strong correlation with nonthermal radio continuum emission and radio-to-optical flux ratios suggest that massive star formation underlies a wide range of galactic activity.

Rickard, L. J.↗
NASA NTRS2004

Maximizing Science Capability for Far-Infrared Space Missions

The far-infrared and submillimeter region (20 microns-800 microns) has perhaps the greatest potential of all wavelengths for advancement in astronomy. When viewed in terms of the cosmic backgrounds, the far-IR is extremely important: half of the total luminosity in the Universe is emitted at rest wavelengths approximately 80-100 microns. At the highest known galaxy redshifts (z approximately equal to 6) this energy is redshifted to approximately 600 microns. Existing and planned missions have a broad range of capabilities, defined in terms of their spectral coverage, spectral resolution, angular resolution, mapping speed, and sensitivity. In this 5-dimensional parameter space, the far-IR is substantially be-hind most other wavelength bands. The opportunity for future missions with great discovery potential is evident. Such missions will be well-suited to answering fundamental questions about the history of energy release in the Universe, the formation and evolution of galaxies, and formation of stellar and protoplanetary systems. We discuss the parameter space that can be filled by a few well-chosen space missions, specifically a submillimeter all-sky survey and a far-IR to submillimeter observatory. Ultimately, a long baseline submillimeter interferometer is necessary to provide sensitivity and angular resolution.

Benford, Dominic↗