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At least 307 records · Page 17
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NASA NTRS1987

Interferometric CO observations of the ultraluminous IRAS galaxies ARP 220, IC 694/NGC 3690, NGC 6420 and NGC 7469

High resolution CO observations of the IRAS galaxies Arp 220, IC 694/NGC 3690, NGC 6240 and NGC 7469 were made with the Millimeter Wave Interferometer of the Owen Valley Radio Observatory. These yield spatial information on scales of 1 to 5 kpc and allow the separation of compact condensations from the more extended emission in the galaxies. In the case of the obviously interacting system IC 694/NGC 3690 the contributions of each component can be discerned. For that galaxy, and also for Arp 220, the unusually high lumonisities may be produced by nonthermal processes rather than by intense bursts of star formation.

Sargent, A. I.↗
NASA NTRS1987

IRAS observations of starburst galaxies

Far infrared properties of Starburst galaxies were analyzed using IRAS observations at 25, 60, and 100 micrometers. Seventy-nine of 102 Starburst galaxies from the list of Balzano were detected. These galaxies have high IR luminosities of up to a few 10 to the 12th power L sub 0 and concentrate in a small area of the IR color - color diagram. The IR power law spectral indices, alpha, lie within the ranges -2.5 <alpha(60,25)< -1.5 and -1.5 <alpha(100,60)< 0. These observed indices can be interpreted in terms of a cold disk component and a warm component. More than 80% of the 60 micrometer emission comes from the warm component. The fraction of the 60 micrometer emission attributable to the warm component can be used as an activity indicator.

Sekiguchi, Kazuhiro↗
NASA NTRS1987

The luminosity function of the brightest galaxies in the IRAS survey

Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume.

Soifer, B. T.↗
NASA NTRS1987

Systematic identification of IRAS point sources

A large scale program was initiated to identify IRAS point sources. At ROE the ideal facilities are at hand to undertake such a large program, viz. the rapid scanning capabilities of the COSMOS measuring machine to exploit the depth and resolution of the U.K. Schmidt Telescope J survey plates. Sources in 44 Schmidt plate areas were identified including 1300 sources and covering 1100 square degrees. The identification comprise 700 galaxy identifications and 600 stellar identifications. There are also about 40 sources with no obvious identification but which can be most easily explained by cirrus, confusion between two sources or sources just outside the 2 sigma error box. A major aim with the galaxy identification is to provide a data base from which sound statistical analyses can be made. Accurate blue magnitudes and morphological classifications for each identification were produced.

Savage, A.↗
NASA NTRS1987

Near-infrared observations of IRAS minisurvey galaxies

Near infrared photometry at J, H, and K was obtained for 82 galaxies from the IRAS minisurvey. The near infrared colors of these galaxies cover a larger range in J-H and H-K than do normal field spiral galaxies, and evidence is presented of a tighter correlation between the near and far infrared emission in far infrared bright galaxies than exists between the far infrared and the visible emission. These results suggest the presence of dust in the far infrared bright galaxies, with hot dust emission contributing to the 2.2 micron emission, and extinction by dust affecting both the near infrared colors and the visible luminosities. In addition, there is some indication that the infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.

Carico, David P.↗
NASA NTRS1987

The properties of highly luminous IRAS galaxies

From a complete sample of 154 galaxies identified with IRAS sources in a 304 sq deg area centered on the South Galactic Pole, a subsample of 58 galaxies with L sub IR/L sub B > 3 was chosen. Low resolution spectra were obtained for 30% of the subsample and redshifts and relative emission line intensities were derived. As a class these galaxies are very luminous with < L sub IR > = 2.9 x 10 to the 11th power L sub 0 and (L sub IR) max = 1.3 x 10 to the 12th power L sub 0. CCD images and JHK photometry were obtained for many of the subsample. The galaxies are for the most part newly identified and are optically faint, with a majority showing evidence of a recent interaction. Radio continuum observations of all galaxies of the subsample were recently obtained at 20 cm VLA with about 75% being detected in a typical integration time of about 10 minutes.

Wolstencroft, R. D.↗
NASA NTRS1987

Spatial deconvolution of IRAS galaxies at 60 UM

Using IRAS in a slow scan observing mode to increase the spatial sampling rate and a deconvolution analysis to increase the spatial resolution, several bright galaxies were resolved at 60 micron. Preliminary results for M 82, NGC 1068, NGC 3079 and NGC 2623 show partially resolved emission from 10 to 26 arcsec., full width at half maximum, and extended emission from 30 to 90 arcsec. from the center. In addition, the interacting system, Arp 82, along with Mark 231 and Arp 220 were studied using the program ADDSCAN to average all available survey mode observations. The Arp 82 system is well resolved after deconvolution and its brighter component is extended; the two most luminous objects are not resolved with an upper limit of 15 arcsec. for Arp 220.

Low, Frank J.↗
NASA NTRS1987

Spectrophotometery of Brackett lines in very luminous IRAS galaxies

Observation of the Brackett-alpha and Brackett-gamma hydrogen recombination lines were made in a sample of galaxies chosen from the IRAS catalog to have high luminosities at infrared wavelengths. Most have strong Brackett line emission indicating large numbers of high mass stars; the formation of these stars may hence be the underlying source for the galaxies' luminosities. However, there are at least two exceptions that may not be explained in this manner: NGC 6240 and Arp 220. Additional evidence indicates that each of these exceptions may be more closely related to Seyfert-type galaxies or other active galactic nuclei.

Depoy, D. L.↗
NASA NTRS1986

Preliminary analysis of the IRAS solar system dust data

The structure of the solar system dust cloud as revealed by IRAS all-sky survey data is discussed. Fourier analysis was used to separate the smooth, large-scale zodiacal background from the narrower dust lanes. The geometry of the background zodiacal cloud appears to show features associated with both the forced inclinations and the forced eccentricities of the dust particle orbits. The ecliptic latitude of the peak of the background zodiacal emission varies nearly sinusoidally with ecliptic longitude with an amplitude of 2.1 + or -0.2 degrees. However, there are marked displacements, both in latitude and longitude, between the leading or ascending curve and the trailing or descending curve, implying that the curves exhibit significant deviations from a simple sinusoidal variation. It is suggested that the plane of symmetry of the background cloud is inclined to the ecliptic by 1.47 + or -0.10 degrees with a descending node of 230 + or -4 degrees, and that the sun is not at the center of symmetry of the cloud.

Dermott, S. F.↗
NASA NTRS1986

The IRAS view of the extragalactic sky

The global properties of the IR emissions from optically bright galaxies observed with the IRAS are described. A histogram of the morphological types of the galaxies is presented. Analysis of the ratio of far IR to blue luminosity (IR/B) reveals that the ratio covers a large range of about five orders of magnitude; 'normal galaxies' in the IR/B ratio of about 0.1-1.0 and galaxies with an IR/B ratio of greater than 1 are observed. The IR/B ratios for galaxies as a function of the 100 micron-60 micron flux density ratio are examined and it is detected that the galaxies which are more active in the IR display a warmer color temperature.

Soifer, B. T.↗
NASA NTRS1986

Far-infrared data for symbiotic stars. I - The IRAS pointed observations

In the present IRAS-pointed observations of eight symbiotic stars, five S-type ones have IR energy distributions that are similar to those of normal M giants, and free-free emission may furnish a fraction of the observed 12- and 25-micron flux in three of them. Three D-type symbiotics have IR energy distributions consistent with those of Mira variables only if the giants are heavily reddened. The binaries' hot components appear to lie outside the dust shell enshrouding the Mira companions.

Kenyon, Scott J.↗
NASA NTRS1986

Lunar occultations of IRAS point sources, 1986-1990

A complete listing is given for objects in the IRAS Point Source Catalog which will be occulted by the moon over the course of 1986-1990. A total of 14,148 ASCII card images is encompassed by the complete listing of objects having geocentric events during this period. The results contained in this complete listing are illustrated in two of the present tables for the brightest objects at 12 and 100 micron wavelengths.

Simon, M.↗
NASA NTRS1986

IRAS observations of R Coronae Borealis - Detection and study of a fossil shell

IRAS observations of the extreme hydrogen-deficient supergiant R CrB are presented and discussed. The star is surrounded by an enormous cool dust cloud which is tentatively identified as a fossil remnant of the hydrogen-rich envelope of the star. The angular extent of the emission corresponds to a linear extent of 8 pc, 20 times larger than the largest previously known shell around a late-type star. The radiating material is distributed very symmetrically over a wide range of radial distances from the star. The dust temperature is nearly constant throughout the extended shell. The total mass in the shell is about 0.3 solar mass. The ejection process appears to have occurred in a spherically symmetric fashion with a nearly constant mass loss rate and expansion velocity over a period of about 150,000 yr, terminating about 26,000 yr ago.

Gillett, F. C.↗
NASA NTRS1986

Near-infrared observations of IRAS minisurvey galaxies

Near-infrared photometry was obtained for 82 galaxies from the Infrared Astronomy Satellite (IRAS) minisurvey, a sample of infrared selected galaxies. The near-infrared colors of these galaxies are similar to those of normal field spiral galaxies, but cover a larger range in J - H and H - K. There is evidence of a tighter correlation between the near and far infrared emission than exists between far-infrared and the visible emission. These results suggest that hot dust emission contributes to the 2.2 micron luminosity, and extinction by dust affects both the near-infrared colors and the visible luminosities. In addition, there is an indication that the far-infrared emission in many of the minisurvey galaxies is coming from a strong nuclear component.

Carico, David P.↗
NASA NTRS1987

Ground-based observations of IRAS candidates for late asymptotic giant branch stars

Ground-based IR photometric observations were obtained for 16 of the IRAS Circular No. 9 sources which have been suggested to be candidates of OH/IR stars. Five of these sources are confirmed to be OH/IR stars and three others as carbon stars. Two are young objects in an early stage of star formation and one, possibly two, are planetary nebulae. Two sources of very low color temperatures (about 180 K) are also found, and may represent objects in transition between the asymptotic giant branch and planetary nebula phases.

Kwok, Sun↗
NASA NTRS1987

IRAS surface brightness maps of reflection nebulae in the Pleiades

Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.

Castelaz, Michael W.↗
NASA NTRS1987

IRAS 00521-7054 - An unusually warm galaxy

IRAS 00521 - 7054 is a galaxy that lies behind the Small Magellanic Cloud. Its infrared energy distribution is quite unusual in that it has exceptionally red 0.6-10-micron colors, while its 12-100-micron spectrum is among the warmest known for a galaxy or quasar, with a peak at 25 microns and an integrated luminosity of close to 10 to the 12th solar luminosity. Its optical spectrum is characteristic of a Seyfert 2 galaxy: low-ionization forbidden lines and H-alpha have FWHM 500 km/s, with some evidence for a much broader component of the H-alpha line. A plausible model is that a central nonthermal source is the dominant source of luminosity, but it is heavily obscured by dust and is thus observed indirectly through reradiation of its flux by the surrounding material. This galaxy may then be a good example of an object in the process of developing into a 'classical' quasar.

Frogel, Jay A.↗
NASA NTRS1987

Observation of the HH 1 and 2 region with IRAS

Infrared Astronomical Satellite (IRAS) observations of the region in Orion containing HH 1 and 2 reveal for the first time the large-scale distribution of newly formed stars. New infrared sources discovered in these observations are discussed, and attempts are made to untangle the complex infrared morphology of this field. A major finding of this study is that HH 1 is near the peak of an intense and broad plateau of 60 and 100 micron emission that spatially corresponds well with the boundaries of a previously detected molecular cloud. Other findings include the detection of an emitting circum-HH object dust complex around HH 2, 25 micron emission associated with the putative HH 1 and 2 exciting source discovered with the VLA, a new luminous far-infrared source, and numerous infrared source complexes, some in blank optical fields and others in fields containing optical emission-line stars.

Pravdo, Steven H.↗