Search NASA⌕ Search

Engineering topics

Kerr, F. J.

Publications and source records attributed to Kerr, F. J..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Dust energetics in the gas phases of the interstellar medium - The origin of the Galactic large-scale far-infrared emission observed by IRAS

The large-scale Galactic properties within the most massive gas phases of the ISM are derived along with the distribution of total Galactic FIR luminosity among the three phases. Most of the Galaxy's total FIR luminosity is found to be emitted by cold dust associated with diffuse H I clouds and molecular gas. The total FIR luminosity of dust associated with extended low-density H II regions accounts for less than 10 percent of the Galaxy's total FIR output. The absence of a significant variation with longitude in the observed temperature of the dust associated with H I gas suggests that diffuse neutral clouds contain very small dust grains that are stochastically heated by the interstellar radiation field. The results are consistent with a model in which most of the FIR luminosity of molecular clouds arises from dust that is associated with giant molecular clouds and heated by embedded and nearby OB stars. H II regions in the inner Galaxy have a mean IR excess ratio of about 2.5, suggesting that the dust in these regions is heated primarily by directly absorbed stellar photons.

Sodroski, T. J.↗
NASA NTRS1987

Large-scale Galactic dust morphology and physical conditions from IRAS observations

In this paper, the zodiacal component is subtracted from the 60 and 100 micron Galactic plane emission by applying an empirical model derived from IRAS data in regions of the sky not dominated by the Galaxy. The corrected observations are used to derive the large-scale physical conditions such as temperature, optical depth, and total FIR brightness of the dust residing in the Galactic disk. (C-12)O, H I, and 5 GHz radio continuum observations are also used to compare the large-scale properties of the gas and dust distributions in the Galaxy. Possible scenarios to explain the findings are suggested.

Sodroski, T. J.↗
NASA NTRS1987

The large scale gas and dust distribution in the galaxy: Implications for star formation

Infrared Astronomy Observations are presented for the diffuse infrared (IR) emissions from the galactic plane at wavelengths of 60 and 100 microns and the total far infrared intensity and its longitudinal variations in the disk were derived. Using available CO, 5 GHz radio-continuum, and HI data, the IR luminosity per hydrogen mass and the ingrared excess (IRE) ratio in the Galaxy were derived. The longitudinal profiles of the 60 and 100 micron emission were linearly decomposed into three components that are associated with molecular (H2), neutral (HI), and ionized (HII) phases in the interstellar medium (ISM), and the relevant dust properties were derived in each phase. Implications of the findings for various models of the diffuse IR emisison and for star formation in the galactic disk are discussed.

Sodroski, T. J.↗
NASA NTRS1972

An upper limit on the OH abundance in the intercloud medium.

A search for weak OH emission at 1665 and 1667 MHz was carried out in three high-latitude directions containing no compact clouds of H I or dust. No OH emission was detected down to low limits, and the comparison of our upper limits with the known H I and dust-column densities reinforces the suggestion that OH tends to be concentrated to regions of high dust or gas density.

Knapp, G. R.↗
NASA NTRS1972

Upper limits on the atomic hydrogen abundance in 12 globular clusters.

Description of 21-cm neutral-hydrogen line observations of 12 globular clusters performed with negative results by means of the NRAO 140-ft telescope. Limits on the atomic hydrogen content yielded by these observations over a range of 11 to 85 solar masses are presented.-

Kerr, F. J.↗
NASA NTRS1971

Colin Gum and the discovery of the Gum nebula

The research of Colin Gum in the field of astronomy is reviewed. It includes a radio survey at 200 MHz, a photographic survey for HII regions in the Southern Milky Way from longitude 220 deg to 20 deg, and a catalogue of 85 physically separate regions. He suggested that certain faint nebulosities were part of a large, nearby H II region excited by gamma Velorum and zeta Puppis. He was also concerned with 21-cm studies.

Kerr, F. J.↗
NASA NTRS1971

A discussion of the ground-based radio observations

It is reasserted that the Gum nebula is not a single nebula but appears to be composed of several different entities. All the surveys of the southern sky in the continuum, recombination line, H I, and OH were considered. The large amount of high frequency radio emission from the small nebula is noted. The outer part of the Gum nebula has not been seen in any radio observations so far. Only the inner part has been observed to date. It is not justifiable to work out any parameters for the whole nebula by taking an average over the whole solid angle subtended by the big nebula. There appears to be a large difference in density between the small nebula and the big one.

Kerr, F. J.↗