A. R. Hyland

Global aspects of the NGC 6334 star formation complex - An infrared survey

The results of a near-IR survey of the NGC 6334 massive H II region/molecular cloud region are presented. No widespread population of embedded stars is found in the cloud within the sensitivity limit. Three new possible premain-sequence objects are found. The mapping of near-IR extended emission is shown to be invaluable in pinpointing obscured H II regions. The locations of the youngest objects in NGC 6334 relative to evolved high-mass objects and H II regions show a likely causal link involving stellar winds or ionizing radiation, in the initiation of star formation. 53 refs.

The centers of star formation in NGC 6334 and their stellar mass distributions

Near-IR observations of specific sites of high-mass star formation activity in the giant H II region/molecular cloud complex NGC 6334 are presented. The observations reveal many faint red sources around the sites of recent high-mass star formation. Most of these sources are associated with the NGC 6334 molecular cloud and are not Galactic field sources. The red objects in FIR-I are identified as belonging to a very young, compact cluster of about 1 pc in spatial extent. In FIR-V an unexpectedly large number of bright red sources are detected which have CO absorption at 2.3 microns. It is proposed that they form a hitherto unrecognized population of high-luminosity premain sequence objects. Evidence is also found in FIR-V that the molecular outflow from the already known high-mass protostar has triggered intermediate-mass star formation via interaction with the local interstellar medium. Evidence is presented that the value of the mass function in the solar neighborhood applies to star formation regions on scales as small as 1 pc and of ages less than 10 million yr. 58 references.

Detection of highly ionized silicon in the planetary nebulae NGC 6302 and NGC 6537

Observations of two high-excitation helium-rich PNs are reported, showing Si VI and Si VII near-IR forbidden line emission from NGC 6302 and forbidden Si VI line emission from NGC 6537. The fluxes observed from NGC 6302 are 3.8 X 10 to the -11 ergs/sq cm sec for the forbidden Si VI line at 1.96 microns and 4.3 X 10 to the -11 ergs/ sq cm sec for the forbidden Si VII line at 2.48 microns. Abundances for Si (5+) and Si (6+) are derived and the central star temperatures are estimated using the abundance ratio. It is found that NGC 6302 probably has the hottest central star of any planetary that has been observed. 39 references.

Far-infrared emission from the AG Carinae ring

A maximum entropy deconvolution technique has been used to resolve far-infrared emission from cool dust associated with the galactic S Doradus variable AG Car. The 50 and 100 micron fluxes are shown to peak at about 9 arsec from Ag Car in the densest part of the ionized ring structure seen around the star. Similarities noted between AG Car and R71 suggest that circumstellar dust ring structures like that of AG Car may often be associated with evolved massive emission-line stars. The results indicate that the ring structure may be due to material that was lost by AG Car during a prior evolutionary state and has subsequently been swept up by the present hot supergiant wind. 42 references.

The spectral and spatial distribution of radiation from Eta Carinae. II High-resolution infrared maps of the Homunculus

The spectral and spatial distribution of radiation from Eta Carinae II and high-resolution infrared maps of the Homunculus are presented. It is found that at the resolution of 1.1 arcsec the source is resolved into two intensity peaks at four wavelengths from 3.6 to 11.2 microns. The separation of the two peaks with wavelength is discussed, concluding that they are produced by an asymmetrical distribution of dust formed by extensive mass loss from the central source. The extension of the wings of the source at various wavelengths provide confirmatory evidence for an enrichment of a grain species such as corundum, relative to silicate material in the outer regions of the source.

Far-infrared observations of young clusters embedded in the R Coronae Australis and rho Ophiuchi dark clouds

Multicolor far infrared maps in two nearby dark clouds, R Coronae Austrinae and rho Ophiuchi, were made in order to investigate the individual contribution of low mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low mass stars in Cr A and four in rho Oph was detected; their far infrared luminosities range from 2 far infrared luminosities L. up to 40 far infrared luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50% of the stars energy was radiated longward of 20 micrometers. meaningful limits to the far infrared luminosities of an additional eleven association members in Cr A and two in rho Oph were also obtained. The dust optical depth surrounding the star R Cr A appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of the results for the cloud energetics and star formation efficiency in these two clouds are discussed.

The 1 May 1982 stellar occultation by Uranus and the rings: Observations from Mount Stromlo Observatory

Abstract The 1 May 1982 occultation of KME 15 by Uranus and its rings was observed at λ = 2.2 μ m using the 1.9-m telescope of the Mount Stromlo Observatory. From model fits to the immersion and emersion ring profiles, accurate midtimes for rings 6, 5, 4, α, β, η, γ, σ, and ϵ, and ring widths, equivalent widths, and normal optical depths for all but ring 6 were obtained. The recently discovered ring 1986 U1R is not detectable in the data, setting an upper limit on the product of ring width and normal optical depth of ≤0.4 km at λ = 2.2 μ m. From the immersion and emersion atmosphere occultations, vertical temperature profiles were obtained by numerical inversion. Both profiles show mean temperatures near 130°K and a local maximum near the 8-μbar pressure level.

The infrared emission of G333.6-0.2 - An extremely nonspherical H II region

The southern H II region G333.6-0.2, which has a total luminosity of 3.3 million solar luminosities (for an assumed distance of 4 kpc) was mapped at 2.2, 10, 30, 50, and 100 microns. At all wavelengths, the surface brightness of the infrared radiation is unusually high and the structure of the source is compact and symmetrical. The present observations, along with previous data, suggest that G333.6-0.2 is excited by a single luminous object or a very compact cluster, which has formed on the front surface of a dense molecular cloud as seen from the earth. It is shown that the spectral and spatial characteristics of the infrared radiation can be understood in terms of this blister model.

A near-infrared study of the NGC 6334-IV region

High-angular-resolution, high-sensitivity maps at 1.2, 1.65, and 2.2 microns have been made of the NGC 6334-IV region. These maps show that the diffuse, bipolar 2-micron emission associated with a bipolar source in the region is probably excited by two sources between the lobes. The first is a highly obscured protostar with a luminosity of about 100,000 solar luminosities. The second possible source of excitation is the scattered free-free and bound-free emission from an H II region surrounding a second young star. The extinction to both these objects must be much higher along the line of sight from earth to them than from them to the bipolar lobes. This is consistent with an earlier interpretation of FIR observations (Harvey and Gatley, 1983) which suggested the presence of an edge-on dust disk around the two central luminosity sources. A rich cluster of lower luminosity IR sources has also been found associated with the two most luminous objects.

An active star formation site in RCW 108

Infrared observations of the bright optical knot in RCW 108 at wavelengths from 1.2 micron to 100 microns are presented. The near-infrared continuum observations reveal the existence of a compact young cluster, still partially embedded in the parent molecular cloud. Among the compact infrared sources are a protostellar object and possibly a T Tauri star. Full spatial imaging over the cluster area enables a mass function to be derived, which agrees well with those of other young clusters. The far-infrared data reveal a bright, compact source centered on the young cluster, with morphological indications of well-mixed dust and gas in the region. High optical depths are found in the mid- and far-infrared, with visual extinctions of up to 40 mag. The large-scale characteristics of this region of active star formation are discussed, and a morphological model for the cluster is proposed. 43 references.