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Low, F. J.

Publications and source records attributed to Low, F. J..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A comparison of high resolution radio and far-infrared maps of M 17

New 3.5-cm radio and 69-micron far-infrared maps of M17, both made with an angular resolution of about 1.5 arcmin, are presented. Each map has three distinct maxima. Two of the maxima on the far-IR map agree in position with the corresponding maxima on the radio map. However, the positions of the brightest peak in the radio and far-infrared maps, located in the SW part of M17, differ by 4.6 + or - 2.2 s in right ascension and +44 + or - 20 sec in declination, with the far-infrared peak lying between the radio peak and the dense molecular cloud southwest of the H II region. It is believed that the positional offset of the radio and far-infrared peak is physically significant. The origin of the far-infrared radiation appears to be thermal emission from dust at the interface of the ionized gas and molecular cloud. This interface region is probably heated by radiation from the H II region.

Wilson, T. L.↗
NASA NTRS1979

Discovery of a compact far-infrared source, IR 12.4+0.5

Results are reported for far-IR, CO, 8-GHz, 15-GHz, H2O, and near-IR observations of a compact far-IR source (designated IR 12.4+0.5) in the M17 molecular cloud, as well as for CO and near-IR observations of a CO peak (designated MC 12.8+0.5) 24 arcmin to the NE of IR 12.4+0.5. The observed far-IR signal from IR 12.4+0.5 is found to correspond to a flux of 2400 Jy at 69 microns for a color temperature of 70 K, and the FWHM size of the source is estimated to be about 36 arcsec. The CO data for both sources and the observed reddening of background giants are shown to indicate high column densities; the existence of internal heat sources is inferred from the measured CO temperatures and the far-IR emission. It is concluded that the two sources are probably sites of very recent or ongoing star formation and that IR 12.4+0.5 is consistent with the 'cocoon star' model of early star formation.

Wright, E. L.↗
NASA NTRS1979

A linear scanning balloon-borne telescope for far-infrared astronomy

A low-background balloon-borne far-infrared (30-300 microns) telescope, utilizing a linear scan mode has dramatically increased the efficiency of mapping large extended areas over more conventional systems. The system consists of a 20 cm linear scanned mirror mounted as an off-axis (Herchelian) telescope designed to achieve an emissivity of 1% or less, a ten position cooled aperture-filter wheel, a cooled Pfund optical system with a composite diamond-germanium bolometer mounted in a spherical cavity, a minimum phase shift ultra-low frequency amplifier, and a 4 micron thick mylar dewar window. This system was used to produce detailed far-infrared maps of the galactic plane. The system specifications and operating parameters will be discussed and preliminary data shown.

Nishimura, T.↗
NASA NTRS1979

Germanium and germanium-diamond bolometers operated at 4.2K, 2.0K, 1.2K, 0.3K and 0.1K

The design, construction, and performance of state of the art germanium and germanium-diamond bolometers operated at 4.2, 2.0, 1.2, and 0.3 K are discussed. These detectors have a broad range of applications, and are particularly important for the long wavelength (far infrared to millimeter) regions. Current results may be extrapolated to lower temperatures and higher levels of performance. A system which will operate at 0.1 K using a He-4-He-3 dilution refrigerator is under development.

Johnson, C.↗
NASA NTRS1979

Tests of low background photo conductors

In support of two infrared astronomy space projects, the IRAS satellite and the IRT on Spacelab 2, low-background tests were carried out on the performance and characterization of Si:Ga, Si:As, Si:Sb and Ge:Ga photoconductive detectors. These test results represent a useful appraisal of this family of detectors when operated at 1.8-4.2 K and at background power levels of 10 to the -14th to 10 to the -13th W. In addition to detector performance data, results are also presented on cryogenically cooled MOSFET amplifiers operated in the source follower and in the balanced-dc-TIA configurations.

Young, E. T.↗
NASA NTRS1979

A small helium-cooled infrared telescope for Spacelab 2

A helium cooled telescope of 15 cm aperture is being designed and constructed jointly by the University of Arizona, the Smithsonian Astrophysical Observatory and the Marshall Space Flight Center for high sensitivity infrared astronomical observations from Spacelab 2. A focal plane array of ten detectors provide a total field of view of 3 deg and cover the wavelength regions 4.5-8.5, 6-7, 9-16, 18-30 and 80-120 microns. A highly redundant all sky survey will be conducted by repeated scanning of the sky during many orbits of the spacecraft. High redundancy will allow discrimination among variable and constant celestial sources and several types of variable nearby sources. The principal astronomical result of the survey will be the absolute flux measurement of low surface brightness, large scale celestial infrared emissions but it will also extend existing IR sky surveys by a factor of 10 in point source sensitivity. The experiment will also make significant engineering measurements of contaminants in the Shuttle environment, test the technology of storage and utilization of large quantities of superfluid helium in space and test mechanical designs for future infrared telescopes for the Space Shuttle.

Gautier, T. N., III↗
NASA NTRS1978

Far-infrared observations of Uranus, Neptune, and Ceres

During a single flight of our 102 cm balloon-borne telescope and 40-250 micron photometer we observed Uranus, Neptune, Ceres, Venus, Mars, and Saturn. Effective temperatures for Uranus (58.5 plus or minus 2 K) and Neptune (59.7 plus or minus 4 K) were determined, thus confirming the absence of a substantial internal heat source for Uranus and the presence of one for Neptune. Ceres has a brightness temperature of 195 plus or minus 12 K at an effective wavelength of 60 microns.

Stier, M. T.↗
NASA NTRS1978

A new, compact far-infrared source in the W31 region

In a survey of the W31 region, a compact far-infrared source was detected at the position of the radio continuum source G 10.6-0.4. Associated with this infrared source and in close coincidence with its position is an H II region with a compact core and extended halo as well as OH and H2O masers. An extended molecular cloud, centered on these sources, has also been detected. The compact source and associated masers may be located at the H II region-molecular-cloud interface in a thin shocked layer of neutral gas driven into the molecular cloud by the expansion of the H II region. The compact H II region is depleted of dust and must be surrounded by a very dense shell of dust and gas (hydrogen number density in excess of 200,000 per cu cm). The source probably represents an early stage of stellar evolution.

Fazio, G. G.↗
NASA NTRS1977

A high-resolution far-infrared survey of the W31 region

A 1-m balloon-borne telescope was used to conduct a far-infrared survey of the W31 region at an effective wavelength of 69 microns with a resolution of 1 arcmin. Within this region seven far-infrared sources were observed. Five of these sources were associated with thermal radio emission. For each of these sources the infrared luminosity is much greater than the Ly-alpha luminosity, a situation requiring either dust absorption of Lyman-continuum photons or a large nonionizing stellar luminosity. Two faint infrared sources had no radio counterparts. Far-infrared radiation was not detected from two known radio sources and from one midinfrared source in this region.

Wright, E. L.↗
NASA NTRS1977

Far-infrared scans of the Galactic plane

Results are reported for balloon-borne scans of the Galactic plane between longitudes of 348 and 32.5 deg, which were made in two broad spectral bands from 60 to 300 microns and from 150 to 300 microns. These results indicate that there are many bright H II regions embedded in a diffuse underlying band of emission in the examined longitude range, that the color temperatures range from 30 to 90 K, and that the width of the plane is at least 2 deg of arc in both spectral bands. A lower-limit IR luminosity of the order of 1 billion suns is computed for both the bright complex of sources at the nucleus and the underlying diffuse emission out to about + or -15 deg of arc from the nucleus. The strong relationship between far-IR emission and radio continuum expected for discrete sources is illustrated, and the results are compared with those of previous studies. It is concluded that the total far-IR luminosity of the central part of the Galaxy is understandable solely in terms of known distributions of stars and dust.

Low, F. J.↗
NASA NTRS1977

New infrared-CO source in M8

A far-infrared map of the M8 region at 69 microns with a 1-arcmin resolution shows an unresolved source 19 arcmin east of the main component. This source is a strong near-infrared emitter, with K = 4.8 and K - L = 2.6 mag. An intense peak in (C-12)O emission (brightness temperature about 36 K) coincides with the new infrared source. Comparison of millimeter-wave and infrared observations suggest that this source is an extremely young compact H II region. Evidence for a depletion of dust opacity inside the H II region is also found.

Wright, E. L.↗
NASA NTRS1976

The effective temperature of Uranus

Uranus was observed in the spectral region from 40 to 250 microns with a 102-cm balloon-borne telescope, and the results were interpreted in terms of model atmosphere calculations to yield an effective temperature of 58 plus or minus 3 K; this sets an upper limit of about 28 per cent on the relative contribution of an internal heat source to the total thermal radiation. On the same flight, the brightness temperatures of Venus (215 plus or minus 13 K) and Jupiter (135 plus or minus 6 K) were also measured, thus reconfirming the existence of an internal heat source for Jupiter.

Fazio, G. G.↗
NASA NTRS1976

Jupiter at five microns

The paper summarizes the information obtained in recent maps of Jupiter at 5 microns, a frequency at which the gases in Jupiter have a relatively low opacity. It is highly possible that 5-micron hot spots are breaks in the cloud deck permitting observation of the hot lower layers of the atmosphere. Many 5-micron sources coincide with blue visual features, but the details of the correspondence need further investigation. Large-scale changes in the appearance of the planet occur at 5 microns on time scales of months; these changes are sufficiently dramatic to produce detectable variations in the whole-disk flux from the planet. Their correspondence to large-scale changes in visual features is not yet determined.

Armstrong, K. R.↗
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 NTRS1976

A far-infrared map of the Ophiuchus dark cloud region

An extensive area of the Ophiuchus dark cloud has been mapped at far-infrared (40-50 microns) wavelengths with high angular resolution (1 arcmin) using a 102-cm balloon-borne telescope. Three sources were detected and resolved. Two of the sources were identified with strong 2-micron sources that were also associated with radio continuum emission. The far-infrared flux is consistent with radiation from dust heated by an early B star. Previous 2-micron observations have indicated the presence of a large number of early B stars embedded in the dark cloud; the far-infrared observations indicate, however, that although some early B stars are in the dark cloud, most of the 2-micron sources are either behind the cloud or are stars not on the main sequence.

Fazio, G. G.↗
NASA NTRS1976

Far infrared observations with a 1-m balloon-borne telescope

Properties of a balloon-borne inertially guided telescope designed to perform high-resolution mapping of far-IR sources are reviewed. Scientific results obtained to date are presented in terms of the sensitivity and angular resolution achieved. The objects observed and mapped include Orion A, W3, M43, OMC-2, NGC 7538, the infrared star IRC+10216, Uranus, and M82. Several modifications of the telescope are described which have markedly increased its IR sensitivity and its efficiency in acquiring sources.

Fazio, G. G.↗
NASA NTRS1975

A high-resolution map of the W3 region at far-infrared wavelengths

The area in the vicinity of the H II region W3 is mapped at an effective wavelength of 69 microns with high angular resolution (1 min) using the 102-cm balloon-borne telescope. The main continuum source, W3, shows a partially resolved complex structure with a FWHM size of 1.8 min. The radio sources W3(OH) and G133.8 + 1.4 are also observed as well as three faint sources not associated with known radio emission.

Fazio, G. G.↗