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NASA NTRS1977

Submillimeter photometry of extragalactic objects

Submillimeter flux densities from five extragalactic objects have been measured, and upper limits set for three others. The galaxies NGC 253 and NGC 1068 have submillimeter spectra steeper than the cube of frequency. Of several source mechanisms considered for the far-infrared and submillimeter flux from NGC 1068, only thermal emission from dust at about 30 K is consistent with the data. The source of that flux, if thermal, must have a diameter of at least 5 arcsec. If one assumes radiation from dust, the masses of interstellar material derived for the central 80-arcsec diameter regions of NGC 253, NGC 1068, and NGC 5236 are, respectively, 800 million, 10 billion, and 3 billion solar masses. Measurements of submillimeter flux densities for 3C 273, BL Lac, NGC 1275, and NGC 5128 show no excess above values obtained by interpolation between radio and mid-infrared data.

Hildebrand, R. H.↗

NASA NTRS1976

Balloon-borne transform spectroscopy

The design and construction of a high-resolution far-infrared Fourier-transform spectrometer for use on the Smithsonian balloon-borne one-meter telescope is described. The instrument will operate at a resolution of about 0.1 kayser in the region from 25 to 150 microns. It will be used to obtain spectra of Jupiter, Venus, Orion, and other H II and molecular cloud regions, as well as the terrestrial stratosphere.

Traub, W. A.↗

NASA NTRS1978

The infrared emission of the Galactic center

Ground-based and airborne infrared observations of the Galactic center near Sgr A are presented. The principal results include: (1) A map at 56 microns (28-arcsec beam FWHM) which shows a ridge of emission in which are immersed two peaks, one at the infrared cluster and another 1 arcmin to the southwest. Early-type stars may produce much of the luminosity seen as thermally reradiated far-infrared flux. (2) A map of the infrared cluster at 34 microns (8.5-arcsec beam) which indicates that the distribution at this wavelength is similar to that at 21 microns, with most of the compact sources which emit at wavelengths shorter than 20 microns emitting relatively weakly at 34 microns. (3) A map at 10 microns which combines observations obtained with 1.5-, 2.3-, 3-, 5.5-, and 20-arcsec beams and shows for the first time the extended 10-micron structure, including the southwestern component, in relation to the cluster of compact sources. Most of the compact 10-micron sources have the structure and spectra to be expected if a luminous object is embedded in a tenuous dust cloud.

Rieke, G. H.↗

NASA NTRS1978

Mutual phenomena of Jupiter's five inner satellites in 1979

In this paper, we first predict eclipses and occultations of the Galilean satellites in 1979 and find that, although circumstances are generally poor, about 75 events are observable. We have then made a special point of including 40 eclipses of J5 (Amalthea) by the Galilean satellites in the hope that both visual and far-infrared light curves can be obtained - the former giving accurate astrometric information for J5, and the latter possible bearing on its surface structure or composition.

Aksnes, K.↗

NASA NTRS1978

The thermal structure of Saturn: Inferences from ground-based and airborne infrared observations

Spectroscopic and photometric infrared observations of Saturn are reviewed and compared to the expected flux from thermal structure models. Large uncertainties exist in the far-infrared measurements, but the available data indicate that the effective temperature of the disk of Saturn is 90 + or - 5 K. The thermal structure models proposed by Tokunaga and Cess and by Gautier et al. (model 'N') agree best with the observations. North-South limb scans of Saturn at 10 and 20 micrometers show that the temperature inversion is much stronger at the South polar region than at the equator.

Tokunaga, A.↗

NASA NTRS1979

Infrared continuum observations of the solar atmosphere

The far-infrared wavelengths (10 microns to 1 mm) were used to study the spatial and temporal structure of the solar atmosphere. Observational results were obtained on flares, faculae, sunspots, and on the center-to-limb intensity distribution, as well as on time variability within these regions. A program of precise monitoring of slow variations in the integrated solar luminosity was shown to be feasible, and initial steps to implement observations were completed.

Hudson, H.↗

NASA NTRS1978

The ammonia mixing ratio in Jupiter's stratosphere

The paper describes the theory that underlies the model calculations which show that the far-infrared bands of ammonia are very sensitive to the ammonia distribution above the Jovian atmospheric inversion layer. Observation of the J = 5 and J = 6 ammonia bands at moderate resolution might permit choice between a cold trap model or the irreversible uv photodestruction model for the ammonia distribution. The lack of prominent emission cores in the NH3 rotation-inversion lines only implies that the mixing ratio is low. The ammonia is uniformly mixed if the inversion temperature is low but, at a higher inversion temperature, emission cores will be observed unless the photodissociation is extremely efficient down to at least the inversion layer.

Goorvitch, D.↗

NASA NTRS1978

Status and summary of laser energy conversion

This paper presents a survey of the status of laser energy converters. Since the inception of these devices in the early 1970's, significant advances have been made in understanding the basic conversion processes. Numerous theoretical and experimental studies have indicated that laser energy can be converted at wavelengths from the ultraviolet to the far-infrared. These converters can be classified into five general categories: photovoltaics, heat engines, thermoelectronic, optical diode, and photochemical. The conversion can be directly into electricity (such as the photovoltaic, thermoelectronic, and optical diode) or it can go through an intermediate stage of conversion to mechanical energy, as in the heat engines. The photochemical converters result in storable energy such as hydrogen. Projected conversion efficiencies range from about 30% for the photochemical to nearly 75% for the heat engines.

Lee, G.↗

NASA NTRS1979

A liquid-helium-cooled grating spectrometer for far infrared astronomical observations

A liquid-helium-cooled grating spectrometer has been developed for low-resolution far-infrared spectrometric measurements of astronomical sources conducted by the 30-cm NASA Lear Jet telescope. Simple MOSFET coupled transimpedance preamplifiers were adopted for the spectrometer design. The infrared spectrometer has resolving powers from 10 to 150 over the wavelength range from 45 to 115 microns.

Houck, J. R.↗

NASA NTRS1978

Four-color infrared bolometer system for one-meter telescope

A far-infrared photometer has been developed as a focal plane instrument for a balloon-borne 102-cm telescope. The four gallium-doped Ge bolometers adopted for the system operate at 1.8 K in a liquid-helium dewar. Wavelength bands of the four-bolometer system are a narrow spectrum between 18 and 22 microns, and bands centered at 42, 70, and 140 microns. The responsivity and Johnson noise of the detectors limit the performance of the instrument.

Daneu, V.↗

NASA NTRS1979

A large-beam sky survey at millimeter and submillimeter wavelengths made from balloon altitudes

A survey has been made of a quarter of the celestial sphere from balloon altitudes with a telescope having a 1.6-deg beamwidth and two spectral bands: 3-10 kaysers and 10-25 kaysers. The limiting sensitivity of the survey was 10,000 Jy. The galactic disk was detected from 358 to 45 deg galactic longitude. The total far-infrared flux from several regions on the galactic plane measured in this survey is 5-10 times larger than that observed by others using smaller beamwidths and small-amplitude spatial chopping, indicating that a substantial part of the emission comes from extended sources. Two other extended sources were also observed, one in the Cygnus region and the other a spur running off the galactic plane at 130 deg galactic longitude toward the north celestial pole. In addition, lower limits for the spectral index of interstellar dust emission are presented.

Owens, D. K.↗

NASA NTRS1979

Two-micron spectrophotometry of the galaxy NGC 253

A very strong Brackett-gamma hydrogen emission line and the 2.3-micron CO stellar absorption feature have been measured in NGC 253. The presence and strength of the CO feature indicate that late-type giant stars produce most of the 2.2-micron continuum emission, while the rate of ionization implied by strength of the Brackett-gamma line indicates that much, perhaps all, of the luminosity detected at far-infrared wavelengths originates from a large number of OB stars. As compared with the corresponding region of the Galaxy, the number of massive young stars in the central 200 pc of NGC 253 is 30 times greater, but the total mass of stars is roughly the same.

Wynn-Williams, C. G.↗

NASA NTRS1979

Far infrared, near infrared, and radio molecular line studies of HFE 2, HFE 3, and FJM 6

Far-infrared, near-infrared, and radio molecular-line observations of the regions of HFE 2, HFE 3, and FJM 6 are described. At positions of high molecular column density nearest to the reported positions of these sources, their infrared emission cannot be confirmed at upper bounds below those of the original detection. Near-infrared observations of the FJM 6 region (which includes the Bok globule Barnard 361) reveal a number of stellar sources, most of which are behind the molecular cloud and are reddened by it. Visual extinction through B 361 estimated by star counts yields A sub V/N(/C-13/O) = 3.7 + or - 1.6) x 10 to the -16th mag sq cm. The gas temperature and the upper bound on the dust temperature in the FJM 6 region are consistent with cosmic-ray heating of the cloud, while the values of these parameters for the clouds in the HFE 2 and HFE 3 regions do not appear consistent with either cosmic-ray or radiative heating.

Fischer, J.↗

NASA NTRS1980

Detection of CO J = 21-20 /124.2 microns/ and J = 22-21 /118.6 microns/ emission from the Orion nebula

The first observation of far-infrared molecular line emission from the interstellar medium is reported. Strong emission from the J = 21-20 and J = 22-21 rotational transitions of carbon monoxide was detected in the Kleinmann-Low/shocked H2 region of the Orion Molecular Cloud. The results imply that the region is optically thin in these lines and that much of the carbon is in the form of CO. This work also represents the first use of an antimony-doped germanium photoconductor in an astronomical application.

Watson, D. M.↗

NASA NTRS1980

Infrared observations of the galactic nucleus

Infrared observations of the galactic nucleus and conclusions regarding the nature of the objects present there are reviewed. Observations of three sources of infrared radiation are discussed: near-infrared emission from cool stars, mid- and far-infrared emission from dust, and line emission from ionized gas. These observations provide information about the mass distribution, the stellar population, and the origin and ionization of the compact mid-infrared sources. The possibility of the existence of a massive central black hole is discussed.

Lacy, J. H.↗

NASA NTRS1980

New experimental possibilities and the future at far IR wavelengths

The observation of molecular phenomena in interstellar clouds through spectroscopy in the longer wavelength region of the infrared is discussed. This is a region where sensitivity is almost universally influenced by background continua; appropriate methods may be either coherent or incoherent, and work above most of the atmosphere is required for much of the spectral range. Thus far, only a very limited amount of molecular work has been done in the far-infrared, but rapid growth and important results are to be expected.

Townes, C. H.↗

NASA NTRS1981

Spectral response from blackbody measurements

Far-infrared and submillimeter detector responsivity and spectral response measurements can be performed simultaneously by sweeping the temperature of a cooled blackbody. Such measurements yield n simultaneous linear equations for n blackbody temperatures. Matrix inversion solutions are observed to fail due to a matrix ill-conditioned for inversion. However, an unconditionally convergent iterative solution can be performed. Results for a gallium-doped germanium detector are described.

Moore, W. J.↗

NASA NTRS1981

Hot-gas cold-dust pumping for water masers associated with H II regions

A collisional pump with an internal sink is proposed for the water masers associated with H II regions, where the population inversion occurs due to the absorption by cold ice-mantle grains in a highly dusty cloud of the far-infrared line radiation of hot water vapor. A new escape probability method is developed to calculate the transfer of line radiation in dusty medium. The pump mechanism explains the power of usual maser sources associated with H II regions and the enormous power of the sources associated with W49 N and external galaxies. Models of maser clouds have a radius of 5 x 10 to the 15th-10 to the 16th cm, an H2 number density of 4 x 10 to the 9th/cu cm, an expansion velocity of 10-30 km/s, a kinetic temperature of 350 K, and a grain temperature of 100 K. Giant maser sources require grains of the size about 1 micron. The apparent size of the emission spots (approximately 10 to the 13th cm) observed by VLBI is interpreted as due to a fluctuation in the cloud, and the assembly of the spots is spread within a size of 10 to the 16th cm. The temperature difference between the dust and gas is due to a relaxation process after an infrared burst accompanying protostar formation.

Deguchi, S.↗