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Gatley, I.

Publications and source records attributed to Gatley, I..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

An infrared study of the eclipsing dwarf nova U Geminorum

One series of data comprising the present J, H, K broadband IR photometry of the cataclysmic binary system U Geminorum over the course of two orbital cycles was obtained several days before an outburst, while a second was gathered when the system had almost completely returned to quiescence from that outburst. In quiescence, the M4-M5.5 red dwarf star supplies most of the IR luminosity of the system, while the light curves at this time are tidally induced ellipsoidal variations of the red dwarf which exhibit an amplitude such that the red dwarf must fill, or nearly fill, its Roche lobe. This shows directly that Roche lobe overflow is important in cataclysmic variable stars. The range of the disk IR colors after outbursts suggest that cool and optically thick gas, together with optically thin gas, supply most of the IR light of the disk.

Berriman, G.↗
NASA NTRS1983

Infrared observations of OB star formation in NGC 6334

Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within. Previously announced in STAR as N83-16263

Harvey, P. M.↗
NASA NTRS1983

Observations of the extinction and excitation of the molecular hydrogen emission in Orion

Observations have been made of two quadrupole purely rotational transitions of molecular hydrogen, the 0-0 S(7) and S(5) lines, and of several previously unobserved vibration-rotation hydrogen lines in the Orion molecular cloud. The line ratios indicate a 2.1-micron extinction of about 2 mag. A comparison of the populations of three vibrational levels shows a distribution of excitation temperatures between 1000 and 3000 K. These values are consistent with the theory that hydrogen is thermally excited in shock-heated gas which cools after passage of the shock front. The total luminosity of the hot molecular hydrogen is 200 plus or minus 80 solar luminosity, and the mass of the emitting gas is of the order 0.05 solar mass. The mass and cooling times of the hot hydrogen indicate that at least 10 solar mass of the material has been heated over the lifetime of the outflow.

Beckwith, S.↗
NASA NTRS1982

Submillimeter extensions of the solar limb determined from observations of the total eclipse of 1981 July 31

First results are presented of observations of a lunar occultation of the solar limb made from the Kuiper Airborne Observatory in the 30 micrometr, 50 micrometer, 100 micrometer, and 200 micrometer continuum during the total solar eclipse of 1981 July 31. The solar limb was extended at the longer wavelengths up to 1000 km higher than predicted from smooth plane-parallel chromospheric models. Results at both second and third contact show the infrared limb extensions to be approximately 0".8, 1"5, 2".5 and 3".0 above the visible limb in the observed bands, respectively. A possible interpretation proposes chromospheric fine structure inhomogeneities of greater density than presently incorporated in models of the middle chromosphere.

Lindsey, C.↗
NASA NTRS1982

Infrared observations of OB star formation in NGC 6334

Infrared photometry and maps from 2 to 100 microns are presented for three of the principal far infrared sources in NGC 6334. Each region is powered by two or more very young stars. The distribution of dust and ionized gas is probably strongly affected by the presence of the embedded stars; one of the sources is a blister H II region, another has a bipolar structure, and the third exhibits asymmetric temperature structure. The presence of protostellar objects throughout the region suggests that star formation has occurred nearly simultaneously in the whole molecular cloud rather than having been triggered sequentially from within.

Harvey, P. M.↗
NASA NTRS1982

Far-infrared mapping of the double-lobed H II region S106

Photometry of S106 at 50 and 100 microns, as well as its mapping with 35 arcsec resolution and a search for a nearby H2O maser source at 2 and 10 microns, have yielded data that are consistent with a 900 pc distance and an O9 (ZAMS) spectral type for a single, central exciting star. The correlation of dust temperature with optical emission, and anticorrelation of dust optical depth with optical emission, support models of S106 which envision an exciting star surrounded by a dusty disk having very low optical extinction along its approximately north-south axis. A local maximum in the dust column density was found to the west of the optical nebula, near the position of an H2O maser, although no local near- or far-IR flux maximum was detected.

Harvey, P. M.↗
NASA NTRS1982

Far-infrared observations of Sagittarius A - The luminosity and dust density in the central parsec of the Galaxy

Far-infrared observations of the central 4 arcmin of the Galaxy with 30-arcsec resolution made simultaneously at 30 microns, 50 microns, and 100 microns are presented. The 30-micron radiation peaks strongly at the position of the galactic center, as determined from the 2-micron surface brightness and the density of ionized gas. The 50- and 100-micron emission is much more extended along the plane and shows two emission lobes, one on either side of the 30-micron peak. At the position of the galactic center itself there is a local minimum in the 100-micron surface brightness. It is concluded that the dust density decreases inward over the central few parsecs of the Galaxy and that the dust density in the central parsec is so low that optical and ultraviolet radiation freely traverses this region. The total luminosity of the sources heating the dust which radiates the far-infrared emission from the central few parsecs is deduced to be between 1 x 10 to the 7th and 3 x 10 to the 7th solar luminosities.

Becklin, E. E.↗
NASA NTRS1982

Observations of NGC 604 over six decades in frequency

Maps in the near-infrared, H-alpha and radio continuum have been obtained of NGC 604, the brightest H II region complex in M33, as well as a measurement of the UV spectrum of the ionizing star cluster. The data show that NGC 604 consists of about ten components of typical size 10 pc, embedded in a much larger envelope with dimensions of 225 pc. At least one component is optically almost completely obscured; it is located close to another object that is only detected in the near-infrared and whose nature is uncertain.

Israel, F. P.↗
NASA NTRS1982

New far infrared observations of the central 30 arcmin of the Galaxy

Observations of the 55 micron and 125 micron emissions of the central 30 arcmin of the Galaxy were performed with 1 arcmin resolution with instrumentation on-board the Kuiper flying observatory. The flux distributions detected showed both wavelengths with peaks near the galactic center, some extension along the galactic plane, and the 125 micron feature located 30 arcsec south. An asymmetry was found around Sgr A, and the variation in dust temperature across the region was calculated from the ratio of the two wavelengths. The temperature peak was around Sgr A, with subsidiary peaks associated with the 55 micron emission. A common heating source was indicated by correlations between cm wavelength sources and the temperature maps. Additionally, the distributions of NH3 and formaldehyde were also correlated with the dust distribution at the center.

Dent, W. A.↗
NASA NTRS1981

Discovery of a protostar in the Large Magellanic Cloud

A near infrared search of the H II region/molecular cloud complex N159 in the Large Magellanic Cloud has revealed a very red (H-K = 2.1, K-L-prime = 2.7) compact object. The location, brightness, color and 2.1-2.4 micron spectrum of this source suggest that it is very young, and similar to the galactic infrared protostars. This is the first identification of an infrared protostar in an external galaxy. Its discovery provides direct evidence of current star formation in the Large Magellanic Cloud, and suggests that regions of star formation in external galaxies will appear similar to those in the Milky Way.

Gatley, I.↗
NASA NTRS1981

The largest H II regions in M101

Coordinated millimeter, infrared, and ultraviolet observations of the five brightest H II regions in M101 are presented. A CO complex has been found to be associated with NGC 5461 which is much more massive than any Milky Way counterpart. A narrow line width has been observed which suggests that the molecular complex may consist of numerous fragments with a volume filling fraction approximately 0.01. NGC 5461 also shows a 10 micron and 20 micron excess which is similar to that of galactic H II regions. The ultraviolet observations show that the 2200 A dust feature is greatly attenuated in all of the H II regions but least of all in NGC 5461. The near-infrared flux densities and B-gamma line strengths are consistent with the hypothesis that a significant fraction of the infrared emission is free-free.

Blitz, L.↗
NASA NTRS1981

Submillimeter observations of solar limb-brightening in the total solar eclipse of 31 July 1981

Eight flights of the Kuiper Airborne Observatory (KAO) were devoted to solar observation. The successful observation of a total solar eclipse was accomplished. The observations were made simultaneously at 30, 50, 100, and 200 microns. The successful adaptation of the KAO for solar observations thus provided the most detailed data to date in this spectral band. The results from a preliminary analysis of the KAO data are summarized: (1) the 200 micron limb is extended about 3 arc sec above the 30 micron limb, indicating the prescence of cool dense material up to the altitudes of spicules; (2) strong radial darkening of the quiet sun intensity profile appeared at 200 microns, probably an indication that hot material in the low chromosphere is recessed into vertical magnetic flux tubes embedded in a cooler nonmagnetic substrate, which obscures the heated material approaching the limb; (3) active regions were observed to undergo a strong increase in contrast above the quiet sun background at wave lengths of 100 microns and longer; and (4) the moon was mapped for use as a photometric standard for determining the absolute intensity of the sun in all four wavelength bands.

Becklin, E. E.↗
NASA NTRS1981

NGC 1097 - The structure of the central 3 kiloparsecs at 10 microns

It is found that the central, optically bright region of the spiral galaxy NGC 1097 is a strong 10 micron source. A striking correlation is seen between the optical and infrared surface brightnesses. The properties of these sources imply that young stars power the infrared emission. It is inferred that the central 30 arcsec of NGC 1097 has a large bolometric luminosity of about 10 to the 11th solar luminosities, most of which originates in a ring approximately 2 kpc in diameter. These observations strongly support the hypothesis that the infrared emission from galaxies is often associated with bursts of star formation.

Telesco, C. M.↗
NASA NTRS1981

Infrared studies of the S235 molecular cloud

Infrared observations from 7.8 to 200 microns have been obtained for the S235 molecular cloud. Far-infrared maps were obtained for a region of active star formation, as marked by the presence of compact H II regions, water masers, and compact near-infrared sources. The primary heating source for the far-infrared emission appears to be the compact H II region, S235A. Detailed examination of the gas energetics in the region supports the plausibility of the picture in which the gas is heated by collisions with warm dust grains. The ratio of far-infrared optical depth to (C-13)O column density is somewhat lower in this source than is commonly found. This effect may be caused by the presence of substantial (C-13)O in regions where the dust is not warm enough to emit substantial 50-100 micron radiation.

Evans, N. J., II↗
NASA NTRS1981

Far-infrared properties of dust in the reflection nebula NGC 7023

Thermal emission from dust in the reflection nebula NGC 7023 has been observed at wavelengths between 40 and 400 microns. The observed far-infrared emission comes from a region approximately 4 arcmin in diameter and shows spatial structure which correlates well with the distribution of reflected visible radiation. Temperature and optical depth maps indicate that the dust which emits the far-infrared radiation is heated by UV and visual radiation from the central star (HD 200775) and that the dust density increases steeply northwest of the star. The far-infrared data are not consistent with either the spherical or uniform slab geometries used in earlier analyses of optical observations. Comparisons of the far-infrared measurements with optical and UV measurements give a value between 2000 and 5000 for the ratio of extinction efficiency in the UV to that at 125 microns. This value is compared with the results of other observational studies and with theoretical grain models.

Whitcomb, S. E.↗