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At least 253 records · Page 14

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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 NTRS1982

BRDF measurements of sunshield and baffle materials for the IRAS telescope

Measurements of the far-infrared bidirectional reflectance distribution functions (BRDF) of four samples of Martin Black coating and one sample of gold coated aluminum from the telescope to be flown on the Infrared Astronomy Satellite (IRAS) are presented. At incidence angles near 35 deg Martin Black is a diffuse reflector at wavelengths as long as 36 microns. The gold coated aluminum sample from the IRAS sunshield has a visible grain which causes a strong diffraction enhancement of the BRDF at large nonspecular angles. This enhancement from the sunshield will increase the stray light level inside the telescope.

Smith, S. M.↗

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.↗

NASA NTRS1982

A high resolution submillimeter map of OMC-1

The 400 micron emission from the central region of OMC-1 has been mapped with 35 resolution. This region contains two emission peaks with sizes of about 0.5 arcmin, separated by approximately 1.5 arcmin which probably represent distinct density condensations in the molecular cloud. Comparison of observations with earlier far-infrared observations shows the two condensations to have similar optical depths and dust masses. A bar of 400 micron emission is found about 15 arcsec SE of the ionization front near Theta 2 A Ori, indicating a sharp increase in dust density in the neutral matter outside the ionized region.

Keene, J.↗

NASA NTRS1982

Imaging antenna arrays

Many millimeter and far-infrared imaging systems are limited in sensitivity and speed because they depend on a single scanned element. Because of recent advances in planar detectors such as Schottky diodes, superconducting tunnel junctions, and microbolometers, an attractive approach to this problem is a planar antenna array with integrated detectors. A planar line antenna array and optical system for imaging has been developed. The significant advances are a 'reverse-microscope' optical configuration and a modified bow-tie antenna design. In the 'reverse-microscope' configuration, a lens is attached to the bottom of the substrate containing the antennas. Imaging is done through the substrate. This configuration eliminates the troublesome effects of substrate surface waves. The substrate lens has only a single refracting surface, making possible a virtually aplanatic system, with little spherical aberration or coma. The array is characterized by an optical transfer function that is easily measured. An array with 19 dB crosstalk levels between adjacent antennas has been tested and it was found that the array captured 50 percent of the available power. This imaging system was diffraction limited.

Rutledge, D. B.↗

NASA NTRS1983

The exciting stars of Herbig-Haro objects

Accurate astrometry and infrared photometry are presented for 16 objects that are believed to represent the exciting stars for Herbig-Haro (HH) objects in their vicinities. These identifications are made on the bases of steeply rising energy distributions, proper motions of HH objects, alignment of sources with HH objects, or far-infrared emission. Exciting stars for the following HH objects are newly discovered or recognized: HH 17; HH 31; HH 32; HH 33 and 40; HH 34; HH 38 and 43; HH group 14 in NGC 2264; RNO 40; RNO 43; and GGD 33a, 33b, and 35. Geometrical alignments of some sources with HH objects support the view that young stars are capable of channeling kinetic energy into small solid angles, as does the fact that some sources are slightly displaced from the apices of fan nebulae (HH 17, R Mon, Haro 6-10). These exciting stars span a wide range of bolometric luminosity, although all are likely to be very young.

Cohen, M.↗

NASA NTRS1983

The variation of dust temperatures in Maffei 2

We report far-infrared photometry for the central regions of Maffei 2. The fitted dust temperatures show a definite decline away from the nucleus. This supports the hypothesis that the molecular clouds close to the nucleus represent a different population from the disk clouds.Extragalactic studies that assume constant temperatures to convert CO integrated intensity to molecular hydrogen surface mass density may be in serious error.

Rickard, L. J.↗

NASA NTRS1983

HL Tauri and its circumstellar disk

New far infrared observations of HL Tau which support the identification of an edge-on disk surrounding the star are presented. A bolometric luminosity for the star of 7.2 solar luminosities and a ratio of infrared to optical luminosity of 630 are indicated. A circumstellar A(V) of about 7.0 mag is produced, consistent with the silicate optical depth to the star. Data on HL Tau's effective temperature and radius and its position on the HR diagram suggest that the star has recently completed its accretion phase and is only 100,000 yr old. The column masses of ice and silicates are combined with the disk dimensions to build a simple model of the disk for comparison with the primitive solar nebula. Estimates of the far-infrared emitting mass provide independent probes of the mass in larger grains around HL Tau.

Cohen, M.↗

NASA NTRS1982

Sub-Kelvin temperatures in space

It is pointed out that the use of temperatures below 1 K in space would provide a significant improvement in several areas of research. The sensitivity of bolometers, for instance, can be improvead by as much as a factor of 50, if the operating temperature is lowered from 1.5 K to 0.3 K. A decrease in temperature to 0.1 K can provide even an improvement up to three orders of magnitude. Detectors based on the utilization of such improvements could be employed for far-infrared (100-1000 microns) photometry and spectroscopy in the low-background conditions of space. The study of critical phenomena in He-3/He-4 mixtures is also of interest, taking into account investigations at the tricritical point (0.87 K), which represents the junction of a first-order and a second-order transition. Tests in space are needed because gravity-related effects make adequate tests on earth impossible. He-3 refrigeration can be used to attain temperatures below 1 K. Adiabatic demagnetization can produuce temperatures below 0.3 K.

Kittel, P.↗

NASA NTRS1983

Three holes bound to a double acceptor - Be(+) in germanium

A double acceptor binding three holes has been observed for the first time with photoconductive far-infrared spectroscopy in beryllium-doped germanium single crystals. This new center, Be(+), has a hole binding energy of about 5 meV and is only present when free holes are generated by ionization of either neutral shallow acceptors or neutral Be double acceptors. The Be(+) center thermally ionizes above 4 K. It disappears at a uniaxial stress higher than about a billion dyn/sq cm parallel to (111) as a result of the lifting of the valence-band degeneracy.

Haller, E. E.↗

NASA NTRS1983

High-resolution infrared spectroscopy of planetary atmospheres

Various techniques for high-resolution infrared spectroscopy of planetary atmospheres are reviewed. Resolving powers of a million are now possible at 1-5 microns with Fourier transform spectrometers and at 10 microns with heterodyne spectrometers. The extension of high-resolution spectroscopy to the far-infrared is currently under development. The role of ground-based high-resolution spectroscopy compared to observations by spacecraft is discussed.

Tokunaga, A. T.↗

NASA NTRS1983

Images in the rocket ultraviolet - The starburst in the nucleus of M83

Ultraviolet images of the SAB(s)c I-II galaxy M83 (NGC 5236) obtained with a rocketborne telescope in broad bandpasses centered at 1540 A and 2360 A show a bright resolved nuclear source which accounts for approximately 20 percent of the flux of the galaxy in both bandpasses. Low-resolution International Ultraviolet Explorer spectra of this source reveal an energy distribution similar to that of the starburst nucleus of NGC 7714. Strong blueshifted absorption lines can be interpreted as evidence for a nuclear wind powered by supernovae. Observations from UV, X-ray, optical, and far-infrared bandpasses are consistent with a starburst approximately one-sixth as strong as that in M82. A scaling of the M82 models of Rieke et al. (1980) predicts that the nucleus of M83 contains 10 to the 6th - 3 x 10 to the 7th solar masses in young stars and has a supernova rate of approximately 0.01 per yr.

Bohlin, R. C.↗

NASA NTRS1983

Analysis of 12-700 micron reflectance spectra of three optical black samples

Normal incidence, specular reflectance spectra of three samples of optical black coatings have been measured in 10 filter passbands at effective wavelengths between 12 and 700 microns. Strong absorption, due to amorphous silicate material in the coatings, is found in the 15-50 micron region of each spectrum. Reflecting-layer model calculations are fitted by a nonlinear least-squares routine to the spectra at wavelengths beyond the absorption band to determine far-infrared optical parameters. It is found that, with a similar wavelength dependence, the absorption coefficient of a new black coating (ECP 2200) made by the Minnesota Mining and Manufacturing Company (3M) is less than 1/10 that of the discontinued coating, 3M Black Velvet Nextel. It is also shown that the extinction effect of a very rough substrate is negligible compared with the effects of increased upper surface roughness and coating thickness attendant upon fully covering a very rough substrate.

Smith, S. M.↗

NASA NTRS1983

Use of Space Station for Earth and Planetary Exploration

The Earth and Planetary Exploration program attempts to develop an understanding of the earth as a planet by utilizing the capability of instruments in space to explore the earth. Studies of the solar system are conducted to gain an understanding of its origin and evolution. The facilities for planetary observations will be greatly extended by making use of a Space Station. Special demands related to the appropriate utilization of a Space Station observatory are discussed, taking into account the employment of ultraviolet spectroscopy for the study of planetary atmospheres and comets, advantages provided by infrared spectroscopy, far-infrared and submillimeter spectroscopy and radiometery, and the search for other planetary systems. The capabilities provided by the Space Station for an investigation of earth resources are explored. Attention is given to vegetation research and observations, land cover dynamics, hydrologic cycle research, geological research, suitable instruments, and a study of crustal dynamics.

Piotrowski, W. L.↗