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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

IRAS observations of active galactic nuclei

IRAS data has been analyzed for 35 radio galaxies and 42 radio-loud quasars, using the coadded survey database. The detection rate is 50 percent with more than 40 percent detected in more than one band. Quasars generally have smooth energy spectra over four or five decades in frequency, consistent with incoherent synchrotron emission from 1 cm to 1 micron. Radio galaxies by contrast have discontinuous spectra, with a large range in the spectral index at IRAS wavelengths. The energy budget shows that the majority of the power per unit bandwidth emerges in the infrared (1-100 microns). The fraction of bolometric luminosity emitted in the infrared is 20-30 percent for the quasars and 40-60 percent for the radio galaxies.

Impey, Chris↗
NASA NTRS1986

Search for brown dwarfs in the IRAS data bases

The results of two searches for brown dwarfs using IRAS data bases are reviewed. From one survey, it is concluded that all of the 5776 high-latitude point sources in the IRAS Point Source Catalog can be positionally associated with stars or galaxies by simple comparisons with optical catalogs and atlases. Only one object near the north Galactic pole possesses an optical/IR color cool enough to be considered as a candidate; it is found to be an unusual carbon star of 1300 K with a probable distance far out in the Galactic halo. The more sensitive Serendipitous Survey, which detected objects about five times fainter than the other survey, also found no brown dwarfs. This survey found fewer ordinary stars than the number extrapolated from the less sensitive survey.

Low, F. J.↗
NASA NTRS1987

IRAS colors of normal stars

Using stars from the Bright Star Catalog, supplemented by cool dwarf stars from the Gliese catalog, that were detected by IRAS, the authors define empirically the median intrinsic visual-to-infrared color indices for 'normal' stars as a function of IRAS wavelength, spectral type and luminosity class. Anomalously red stars are discussed. Two otherwise undistinguished F giant stars are found with significant excesses at 12 microns. Be stars differ markedly from nonemission B stars in their V-(12) indices due to contamination of the former by free-free emission. Both B and Be stars show large dispersions in V-(25) colors that are associated with the heating of local, but strictly interstellar, dust clouds by some of the non-emission B stars. The derived sequences of stellar colors are closely approximated by either simple blackbody predictions or by model-atmosphere calculations.

Cohen, Martin↗
NASA NTRS1987

IRAS constraints on the sizes of Pluto and Charon

Thermal emission models indicate that Charon contributes a significant amount of the infrared radiation detected by IRAS during the observation of mutual eclipse events. The IRAS observations also show that the most probable diameters for Pluto and Charon are 2200 and 1300 (+ or - 150) km. These results are consistent with there being some atmosphere on Pluto.

Tedesco, Edward F.↗
NASA NTRS1987

New CO and HCN sources associated with IRAS carbon stars

Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

NGUYEN-Q-RIEU↗
NASA NTRS1987

Constraints for models of Be stars derived from UV and IRAS observations

The effect of different geometrical models (disk and circumstellar shell) on the mass loss determinations of Be stars is investigated. The characteristics of the disk and circumstellar shell models are described. The models are applied to the analysis of the column density derived from the UV lines and emission measurements derived from IRAS observations of 10 Be stars, and the mass loss rate for these stars are calculated. It is observed that the mass loss rates obtained from the circumstellar shell model are a factor of 0.01 smaller than those of the disk model; the mass of the IR emitting region is three times larger in the shell model than that in the disk model; and the radial outflow velocity of the IR emitting region for the shell model is of the order of 0.01 km/sec and for the disk model of the order of 10 km/sec. It is noted that the UV and IRAS observations can be analyzed using the two models if the proper geometry is considered.

Lamers, H. J. G. L. M.↗
NASA NTRS1987

The IRAS view of the extragalactic sky

The IR-observable characteristics of the extragalactic sky are reviewed, summarizing the results of recent studies based on the IRAS survey, which covers over 96 percent of the sky to about 500 mJy at 12, 25, and 60 microns and to about 1.5 Jy at 100 microns. The numerical and morphological data are described; possible mechanisms for the IR emission are discussed; and the object classes are considered separately. Consideration is given to spiral and disk galaxies, barred and ring galaxies, irregular and dwarf galaxies, blue compact galaxies, elliptical and S0 galaxies, AGN observations (BL Lacs and OVV quasars, Seyfert galaxies, and quasars), highly luminous IR galaxies, and the cosmological implications of the IRAS findings. Diagrams, graphs, and tables are provided.

Soifer, B. T.↗
NASA NTRS1987

OH megamasers in high-luminosity IRAS galaxies

OH megamaser emission and H I and CO profiles from the distant infrared galaxies IRAS 10173 + 0828, III Zw 035, and Zw 475.056 are reported. The OH isotropic luminosities at 1667 MHz are 463, 534, and 6.6 solar luminosities, respectively. Far-infrared pumping efficiencies of the OH greater than 1 percent are found in IRAS 10173 + 0828 and III Zw 035. These two galaxies show anomalously large 1667/1665 MHz emission line ratios. OH megamasers reside in the nuclei of superluminous far-infrared galaxies that have a high content of molecular gas, high efficiency of star formation, and in some instances, a striking deficiency of atomic hydrogen.

Mirabel, I. F.↗
NASA NTRS1988

High-resolution spectroscopy of the 3 micron emission features in NGC 7027 and IRAS 21282+5050

High-resolution 3 micron spectra of NGC 7027 and IRAS 21282+5050 are presented. The well-known 3.29 micron emission feature has very similar shapes in the two objects, but a small shift is present between them. The emission features at 3.46 and 3.52 microns recently found in IRAS 21282+5050 are also present in the spectrum of NGC 7027. In addition, there may be two other weak features at 3.55 and 3.58 microns in NGC 7027. These emission features might be related to saturated hydrocarbons. The spectra provide further constraints on the origin of the 'unidentified' emission features.

Nagata, Tetsuya↗
NASA NTRS1988

The circumstellar water fountains of IRAS 16342-3814 - A very high velocity bipolar outflow

Maser emission from OH and H2O is observed to be present over an exceptionally wide range of velocities in the cold, stellar infrared source IRAS 16342-3814. OH emission at 1612, 1665, and 1667 MHz spans 130 km/s, a range far larger than in any other known OH/IR star. The H2O emission features appear as two widely separated doublets with a full velocity spread of 259 km/s. Several lines of evidence point to the conclusion that IRAS 16342-3814 is an evolved star with a bipolar outflow, related to objects such as OH 231.8 + 4.2 and M1 - 92. The H2O masers are interpreted as streams or clumps of molecular gas forced out the polar axes by, or as part of, a wind from an accretion disk, while the OH masers appear to arise from lower velocity material at intermediate latitudes.

Likkel, Lauren↗
NASA NTRS1987

A very deep IRAS survey at the north ecliptic pole

The data from approximately 20 hours observation of the 4- to 6-square degree field surrounding the north ecliptic pole have been combined to produce a very deep IR survey at the four IRAS bands. Scans from both pointed and survey observations were included in the data analysis. At 12 and 25 microns the deep survey is limited by detector noise and is approximately 50 times deeper than the IRAS Point Source Catalog (PSC). At 60 microns the problems of source confusion and Galactic cirrus combine to limit the deep survey to approximately 12 times deeper than the PSC. These problems are so severe at 100 microns that flux values are only given for locations corresponding to sources selected at 60 microns. In all, 47 sources were detected at 12 microns, 37 at 25 microns, and 99 at 60 microns. The data-analysis procedures and the significance of the 12- and 60-micron source-count results are discussed.

Houck, J. R.↗
NASA NTRS1988

Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 5: The point source catalog declination range -30 deg greater than delta greater than -50 deg

The Infrared Astronomical Satellite (IRAS) was launched January 26, 1983. During its 300-day mission, IRAS surveyed over 96 pct of the celestial sphere at four infrared wavelengths, centered approximately at 12, 25, 60, and 100 microns. This is Volume 5, The Point Source Catalog Declination Range -30 deg greater than delta greater than -50 deg.

Source record↗
NASA NTRS1988

Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 2: The point source catalog declination range 90 deg greater than delta greater than 30 deg

The Infrared Astronomical Satellite (IRAS) was launched January 26, 1983. During its 300-day mission, IRAS surveyed 96 pct of the celestial sphere at four infrared wavelengths, centered approximately at 12, 25, 60, and 100 microns. This is Volume 2, The Point Source Catalog Declination Range 90 deg greater than delta greater than 30 deg.

Source record↗
NASA NTRS1988

Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 3: The point source catalog declination range 30 deg greater than delta greater than 0 deg

The Infrared Astronomical Satellite (IRAS) was launched January 26, 1983. During its 300-day mission, IRAS surveyed over 96 pct of the celestial sphere at four infrared wavelengths, centered approximately at 12, 25, 60, and 100 microns. This is Volume 3, The Point Source Catalog Declination Range 30 deg greater than delta greater than 0 deg.

Source record↗
NASA NTRS1988

A catalog of IRAS observations of large optical galaxies

A catalog is presented of IRAS observations of 85 galaxies with blue-light isophotal diameters greater than 8 arcmin. The observations, data processing, and data measurement techniques are described, and total IRAS flux densities and integrated infrared emission properties of the sample are reported. Infrared brightness profiles of the detected galaxies and infrared surface brightness contour maps of the galaxies for which structural features were resolved are displayed. A classification scheme based on the degree of central concentration and spatial structure of the 60 micron emission of the best-resolved galaxies is proposed. The 60 micron and blue-light isophotal diameters of the largest galaxies are compared.

Rice, W.↗
NASA NTRS1988

IUE-IRAS studies of the infrared cirrus

The 60 and 100 micron cirrus emission around 256 lines of sight in the IRAS all-sky survey was measured, and the flux averages were used to study the distribution, variations, and correlations of the IRAS infrared cirrus fluxes with various interstellar parameters. It was found that the 60 and 100 micron fluxes correlate with the depletion of Si and show a trend with the depletion of Fe for 51 lines of sight toward the Galactic halo. No correlation was found with the abundances of Si, Mn, Fe, S, or Zn or with abundance ratios for the full sample of 256 stars. An abundance ratio of about 3 x 10 to the 7th by number relative to H was derived from 60 and 100 micron flux ratios and the H column along the line of sight; this ratio appears to decrease by a factor of 10 into the halo.

Van Steenberg, Michael E.↗
NASA NTRS1989

The double-nucleus galaxy IRAS 02580-1136 - A merging system

CCD imaging, infrared photometry, and optical spectroscopy lead to the conclusion that IRAS 02580-1136 consists of two colliding galaxies and is possibly an ongoing merger. Visually, the IRAS source displays two distinct brightness concentrations. These two nuclei, referred to as A and B, have a projected linear separation of 7 kpc and a radial-velocity difference of 180 km/s. Nucleus A belongs to a bulgelike structure and has an optical spectrum typical of a Seyfert 2. It is argued that it harbors a 99 percent dust-obscured low-luminosity Seyfert I source that powers most of the far-infrared radiation. Nucleus B is either a galactic bulge or a low-luminosity elliptical with a heavily reddened compact H II region at its center.

Heisler, Charlene A.↗