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Wright, E. L.

Publications and source records attributed to Wright, E. L..

At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Was the Big Bang hot?

Techniques for verifying the spectrum defined by Woody and Richards (WR, 1981), which serves as a base for dust-distorted models of the 3 K background, are discussed. WR detected a sharp deviation from the Planck curve in the 3 K background. The absolute intensity of the background may be determined by the frequency dependence of the dipole anisotropy of the background or the frequency dependence effect in galactic clusters. Both methods involve the Doppler shift; analytical formulae are defined for characterization of the dipole anisotropy. The measurement of the 30-300 GHz spectra of cold galactic dust may reveal the presence of significant amounts of needle-shaped grains, which would in turn support a theory of a cold Big Bang.

Wright, E. L.↗
NASA NTRS1982

Thermalization of starlight by elongated grains - Could the microwave background have been produced by stars

The possibility of the microwave background being produced by stars after the big bang is considered. The critical problem for this hypothesis is the source of the long-wavelength opacity for observed wavelengths greater than 10 cm. It is shown that free-free opacity cannot thermalize the background. Spherical dust grains also fail, but needle-shaped conducting grains can provide sufficient opacity to produce the observed spectrum with a metal abundance Z approximately equal to 10 to the -7th.

Wright, E. L.↗
NASA NTRS1981

Quasar reddening, intergalactic dust, and the microwave background

Quasar reddening and distortion of the microwave background are calculated, assuming that dust in intervening galaxies and any possible intergalactic dust follow the extinction curve for dust in the Galaxy. Quasar reddening implies that the average line of sight has a visual extinction of 0.85 + or - 0.51 at z = 3; and this amount of dust is enough to distort the microwave background (given a very bright initial population of stars), but not enough to thermalize the added energy at wavelengths greater than 3 cm.

Wright, E. L.↗
NASA NTRS1981

Far-infrared observations of the H2O masers in NGC 281, NGC 2175, and S255/257

The H2O masers in NGC 281, NGC 2175, and S255/257 have been observed in four far-infrared bands from 40-140 microns with 30 arcsec and 50 arcsec beams. The far-IR positions are consistent with the H2O positions. The far-IR sources have luminosities of 10 to the 4 + or 0.5 solar luminosities, dust temperatures of 36-50 K, H densities greater than 10 to the 4.5, and apparent masses of 12-120 solar masses.

Wright, E. L.↗
NASA NTRS1980

The infrared echo of a supernova in a dust cloud

A simple model is given for the infrared light-echo from a supernova explosion in a molecular cloud. The color temperature is determined by the vaporization temperature of the dust grains, and the time scale is given by the light travel time across the distance to which grains are vaporized. For typical parameters, a supernova exploding in a cloud with a density of approximately 10,000/cu cm at a distance of 10 kpc produces a flux of approximately 60,000 Jy at 3.5 microns for 150 days.

Wright, E. L.↗
NASA NTRS1980

Search for far-infrared emission from young supernova remnants

A search has been conducted for 80-350 micron emission from the Tycho, Kepler, and Cas A supernova remnants. The bolometric fluxes are less than 5 x 10 to the -11th, 4 x 10 to the -12th, and 9 x 10 to the -12th W/sq m, respectively, for the entire radio shell, corresponding to luminosities less than 25,000, 1100, and 1500 solar luminosities (within 2 standard deviations). The ratio of dust to gas in Cas A is at least 10 times less than the 'normal' ratio.

Wright, E. L.↗
NASA NTRS1980

The far-infrared size of IRC +10216

IRC +10216, a carbon star undergoing extensive mass loss, has been observed with a broad-band far-infrared (40-250 micron) photometer on the CFA/UA 102 cm balloon-borne telescope. From repeated scans, the deconvolved FWHM size of IRC +10216 was determined to be 0.92 arcmin plus or minus 0.15 arcmin. Based on this size, models for the density distribution of the dust in the surrounding cloud indicate that there is more dust at large radii than would be predicted by a 1/r-squared density distribution and that the mass-loss rate of the central source was twice its current value only 2000 years ago.

Fazio, G. G.↗
NASA NTRS1979

Evidence for a variable far-infrared source in NGC 6334

NGC 6334 has been mapped with a 40-250 micron photometer with 1 arcmin resolution. Six sources of far-infrared radiation have been detected. The second-strongest source was not detected in an earlier (2.7 years) 40-350 micron survey of the same region. This source is interpreted as a variable far-infrared source. The new source, located at the position of OH and H2O maser sources, is extended (0.7 arcmin FWHM) and has a bolometric luminosity of 190,000 solar luminosities and may represent a hitherto unobserved transient stage of protostellar collapse.

Mcbreen, B.↗
NASA NTRS1979

Distortion of the microwave background by a hot intergalactic medium

The distortion of the cosmic microwave background by a hot, optically thin intergalactic medium (IGM) is calculated using the full frequency redistribution function. Even if the IGM produces all of the cosmic X-ray background, the distortion of the microwave background is not detectable in the present observational data.

Wright, E. L.↗
NASA NTRS1979

Millimetre and submillimetre measurements of the Crab Nebula

The flux from the central region of the Crab Nebula in three broad spectral passbounds with flux-weighted mean wavelengths of 300 microns, 400 microns and 1 mm has been measured. The inferred total flux densities for the entire nebula are consistent with an extrapolation of the power law spectrum found at longer wavelengths. Derivations of various flux densities are presented, and it is concluded that the luminosity of dust emission from the Crab Nebula varies between 1300 and 5000 suns as the temperature varies from 40 to 120 K, respectively.

Wright, E. L.↗
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

Rotationally excited HD toward Zeta Ophiuchi

Copernicus satellite measurements of HD in J-double prime = 1 and J-double prime = 0 toward Zeta Oph are reported. The ratio of the number densities of HD in the J = 0 and J = 1 states is determined to be 0.15 + or - 0.02 at the 1-sigma level. A value of approximately 24 x 10 to the -17th erg/cu cm per A at 1000 A is obtained for the UV energy density at the Zeta Oph cloud, and the mechanisms for excitation of HD are examined. A tight upper limit is derived for the abundance of HCl, which has been predicted to be present due to the interaction of ionized chlorine with neutral hydrogen. A calculation is performed which indicates that the cloud is 28 pc from the star. It is shown that the two-component cloud model of Black and Dalgarno (1977) with densities of 500 and 2500 H nuclei per cu cm for the outer regions and core, respectively, is in excellent agreement with the observations.

Wright, E. L.↗
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

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.↗