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Gatley, I.

Publications and source records attributed to Gatley, I..

65 records · Page 4
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NASA NTRS1978

Far-infrared observations of H II regions in M33

Three H II regions in M33, namely, IC 133, NGC 595, and NGC 604, have been observed at far-infrared wavelengths. Only NGC 604, the strongest radio source of the three, was detected. The far-infrared radiation appears to be thermal emission from dust. The amount of dust known to be present in NGC 604 from comparison of optical and radio data is sufficient to account for the observed far-infrared emission. The total power radiated in the far-infrared is comparable to the total luminosity of the exciting stars of the H II region.

Gatley, I.↗
NASA NTRS1978

Far-infrared observations of H II regions near the galactic center

This paper presents and discusses far-infrared observations of nine H II regions within 1 deg of the galactic center, including Sgr A, Sgr B2, Sgr C, and G0.5-0.0. The far-infrared luminosity, color temperature, and optical depth of these regions and the ratio of infrared flux to radio-continuum flux lie in the range characteristic of spiral-arm H II regions. The far-infrared results are therefore consistent with the idea that the galactic-center H II regions are ionized by luminous early-type stars. Steep systematic gradients in far-infrared color temperature and optical depth are seen along the galactic plane between Sgr B2 and G0.5-0.0; the appearance of this area is similar to that of regions of star formation in the spiral arms.

Gatley, I.↗
NASA NTRS1978

Detection of molecular hydrogen emission from five planetary nebulae

The v = 1 to 0 S(1) line of molecular hydrogen has been detected in five planetary nebulae. They are the Ring Nebula (M57, NGC 6720), BD+30 deg 3639, Hb 12, CRL 618, and CRL 2688. A region in the northeast of the Ring Nebula has been mapped in both the v = 1 to 0 S(1) molecular hydrogen line and the Brackett gamma line of atomic hydrogen. The H2 emission is not spatially correlated with the B-gamma, but is correlated with the (OI) emission as determined from interference filter photographs.

Beckwith, S.↗
NASA NTRS1977

Airborne far-infrared observations of the galactic center region

Maps of a region 10 arcmin in diameter around the galactic center made simultaneously in three wavelength bands at 30, 50, and 100 microns with about 1 arcmin resolution are presented, and the distribution of far-IR luminosity and color temperature across this region is derived. The position of highest far-IR surface brightness coincides with the peak of the late-type stellar distribution and with the H II region Sgr A West. The high spatial and temperature resolution of the data is used to identify features of the far-IR maps with known sources of near-IR, radio continuum, and molecular emission. The emission mechanism and energy sources for the far-IR radiation are analyzed qualitatively, and it is concluded that all of the observed far-IR radiation from the galactic-center region can be attributed to thermal emission from dust heated both by the late-type stars and by the ultraviolet sources which ionize the H II regions. A self-consistent model for the far-IR emission from the galactic-center region is presented. It is found that the visual extinction across the central 10 pc of the Galaxy is only about 3 mag and that the dust density is fairly uniform in this region. An upper limit of 10 million suns is set on the luminosity of any still unidentified source of 0.1- to 1-micron radiation at the galactic center.

Gatley, I.↗
NASA NTRS1977

Infrared observations of Nova Cygni 1975

Infrared photometry from 1 to 20 microns and spectroscopy at about 2 microns are presented for Nova Cygni 1975 for the period from 2 days before to 1 yr after maximum light. The data can be explained by a simple model in which the expanding gas expelled during the explosion is always a plasma at approximately 10,000 K. Initially the gas is optically thick; this phase clearly defines the time of onset of the nova. Later, as the gas continues to expand, it becomes optically thin. The temporal dependence of the observed flux suggests that in this phase the expanding cloud is in the form of a shell. After about 300 days, long-wavelength emission which may be attributable to thermal reradiation from dust is observed.

Ennis, D.↗
NASA NTRS1976

Infrared studies of an ionization front region in the Orion Nebula

A ridge or bar of emission at 10 microns has been found which is parallel and adjacent to the H I-H II interface in the Orion Nebula 2 arcmin southeast of the Trapezium. The emission is interpreted as coming from heated dust whose density at the interface is an order of magnitude higher than that inside the H II region. The source of luminosity for this emission is shown to be the Trapezium stars. The unique geometry of the bar with respect to the heat source is used to evaluate the dust density in the bar and the size of the dust grains.

Becklin, E. E.↗
NASA NTRS1976

One arc-minute resolution maps of the Orion Nebula at 20, 50, and 100 microns

The paper presents maps of the central regions of the Orion Nebula which are based on observations made at wavelengths of 20, 50, and 100 microns with a resolution of 1 arcmin. The 50- and 100-micron observations were made with the NASA 91-cm Airborne Infrared Telescope. The principal far-IR features observed include a sharp emission peak near the position of the IR cluster, about 1 arcmin northwest of the Trapezium; a ridge of emission that is elongated north-south about this peak; and a barlike feature running northeast to southwest about 2 arcmin southeast of the Trapezium. The following conclusions are reached about the nature of the far-IR emission: (1) the total luminosity (between 10 and 1000 microns) of the IR cluster exceeds the solar luminosity by a factor of at least 120,000; (2) heating by both the IR cluster and the Trapezium stars is important in producing the central emission ridge; (3) the IR cluster is located within the molecular cloud; (4) the Trapezium stars are no more than 0.1 pc from that cloud; and (5) the bar of emission southeast of the Trapezium can be identified with an optically visible ionization front.

Werner, M. W.↗
NASA NTRS1974

Infrared observations of Comet Kohoutek /1973f/

Comet Kohoutek has been observed at wavelengths between 1.25 and 12.5 microns before and after perihelion passage extending to comet-sun distances of 1 AU. The luminosity and the variation of brightness with comet-sun distance in the infrared are extraordinarily similar to those of Comet Ikeya-Seki (1965f). Apart from an apparent 'silicate' emission feature near 10 microns, the spectrum of the comet between 3.5 and 12.5 microns is close to that expected from emission by grey particles. Hotter particles and scattered sunlight produce the bulk of the 1.25- to 3.5-micron emission.

Gatley, I.↗
NASA NTRS1974

A new infrared complex and molecular cloud in Orion

A new complex of infrared sources about one minute across has been discovered in Orion. Associated with this cluster is an extended molecular cloud producing intense CO emission. Its measured infrared luminosity is less than 500 times the luminosity of the sun. The complex is hypothesized to be composed of pre-main-sequence sources. Several arguments suggest that these stars heat dust in the larger molecular cloud and thus cause the strong CO emission. The complex is not associated with a known visible or radio continuum feature, and searches over a 0.7 x 0.7-deg field show no other comparable unknown 2.2-micron sources.

Gatley, I.↗
NASA NTRS1974

Infrared observations of Phobos from Mariner 9

Radiometric measurements of Phobos at 10 and 20 microns show that the surface is covered by a material whose conductivity is extremely low, around .000001 cal per cm per sec per deg K. It is concluded that Phobos is covered with a layer of dust at least 1 mm thick.

Gatley, I.↗