Showing papers by "Michael W. Werner published in 1985"
TL;DR: In this paper, the authors used radio recombination line and CO line data for G25.4NW and G30.8-0.2 to understand star formation in the molecular ring at 5 kpc in the galactic radius.
Abstract: Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy HII regions G30.8-0.0 (in the W43 complex) and G25.4-0.2, along with radio and molecular line measurements at selected positions. The purpose of this study is an effort to understand star formation in the molecular ring at 5 kpc in galactic radius. Measurements at several far infrared wavelengths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. Using radio recombination line and CO line data for G25.4-0.2, the distance ambiguity for this source is resolved. The large distance previously ascribed to the entire complex is found to apply to only one of the two main components. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright HII regions. Using the revised distances of 4.3 kpc for G25.4SE and 12 kpc for G25.4NW, it is found that the latter, which is apparently the fainter of the two sources, is actually the more luminous. The ratio of total luminosity to ionizing luminosity is very similar to that of HII regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated.
48 citations
TL;DR: In this paper, the far-infrared fine structure lines of O III have been obtained for six planetary nebulae, and a simultaneous solution was obtained for electron temperature and density, as well as means of evaluating the importance of inhomogeneities.
Abstract: Observations of the far-infrared fine structure lines of O III have been obtained for six planetary nebulae. The infrared measurements are combined with optical O III line fluxes to probe physical conditions in the gas. From the observed line intensity ratios, a simultaneous solution was obtained for electron temperature and density, as well as means of evaluating the importance of inhomogeneities. Densities determined from the far-infrared O III lines agree well density diagnostics from other ions, indicating a fairly homogeneous density in the emitting gas. Temperatures are determined separately from the O III 4363/5007 A and 5007 A/52 micron intensity ratios and compared. Systematically higher values are derived from the former ratio, which is expected from a nebula which is not isothermal. Allowance for the presence of temperature variations within these nebulae raises their derived oxygen abundances, determinations to be reconciled with the solar value.
42 citations
TL;DR: In this paper, an unambiguous infrared identification of a sample of OH/IR stars in the galactic disk and in the vicinity of the galactic center is presented, where simultaneous OH and broadband infrared photometric measurements are used to derive quantitative relations between the infrared and OH fluxes and the properties of the circumstellar shells, providing observational evidence that these stars represent an evolutionary sequence of increasing mass loss rate.
Abstract: Unambiguous infrared identifications of a sample of OH/IR stars in the galactic disk and in the vicinity of the galactic center are presented. Simultaneous OH and broadband infrared photometric measurements are used to derive quantitative relations between the infrared and OH fluxes and the properties of the circumstellar shells, providing observational evidence that these stars represent an evolutionary sequence of increasing mass loss rate. These relations are used to explain the observed time variations of the silicate absorption feature with changing bolometric luminosity in OH/IR stars. It appears that the ratio of the OH flux to the number of pump photons is not constant, but is also a function of the mass loss rate.
17 citations
TL;DR: The first detection of the [OI] 145 μm and [CII] 158 μm lines in a planetary nebula was made by Melnick et al. as discussed by the authors.
Abstract: We have made observations of the far-infrared, fine structure emission lines [01] 63 μm, [01] 145 μm, and [CII] 158 μm in the proto-planetary nebulae AFGL 2688 and AFGL 618, and the classical planetary nebulae IC 418 and NGC 7027. The observations were made with the UC Berkeley tandem Fabry-Perot spectrometer aboard the Kuiper Airborne Observatory in October, 1983. Apertures of 30″ (63 μm) and 45″ (145 μm and 158 μm) were used. We detected all three lines in NGC 7027, but obtained only upper limits to the 63 μm emission from the other three nebulae and the 158 μm emission from AFGL 618. The line fluxes in NGC 7027 are: [OI] 63 μm, 3.2 ± 1.0 × 10–17 W cm-2; [OI] 145 μm, 1.2 ± 0.4 × 10–18 W cm-2; [CII] 158 μm, 3.4 ± 1.0 × 10–18 W cm-2. The [01] 63 μm line has been detected previously in NGC 7027 by Melnick et al. (1981) but these observations represent the first detections of the [OI] 145 μm and [CII] 158 μm lines in a planetary nebula.
1 citations
01 Jan 1985
TL;DR: In this article, the authors review the early work in this still largely unexploited field and report results in each of the areas listed above, and preview the dramatic advances forthcoming in this area from the IRAS satellite and the further progress which will come from the next generation of infrared and submillimeter telescopes.
Abstract: Broad-band photometric observations at far infrared and submillimeter wavelengths (30 μm < λ < 1mm) provide a unique probe of circumstellar shells in evolved objects and of the mass loss processes which produce them. The problems which these observations explore include: dust properties and dust-to-gas ratios in the outflowing material, the mass and structure of the circumstellar shell, and the pumping mechanism for maser emission. This contribution reviews the early work in this still largely unexploited field and reports results in each of the areas listed above. We also preview the dramatic advances forthcoming in this area from the IRAS satellite and the further progress which will come from the next generation of infrared and submillimeter telescopes.
1 citations
01 Jan 1985
TL;DR: The Space Infrared Telescope Facility (SIRTF) as discussed by the authors is a superfluid-helium-cooled, 0.85-meter infrared telescope to be placed in orbit in 1993.
Abstract: The scientific and technical background and prospects for the space infrared telescope facility (SIRTF) are described. This facility is a superfluid-helium-cooled, 0.85-meter infrared telescope to be placed in orbit in 1993. It is designed to carry out photometry over the wavelength range 2 to 700 micrometers, and diffraction-limited imagery in either broad or narrow spectral bands over the range 1.8 to 200 micrometers. It is proposed that SIRTF measure spectra in the range 2.5 to 200 micrometers with resolving power between 50 and 1000 and that the focal plane contain about 20,000 detector elements, both discrete and in arrays. The SIRTF observatory is designed to be a long-lived facility providing opportunities for general investigations by the entire scientific community. For following up the all-sky survey carried out by the Infrared Astronomical Satellite (IRAS), SIRTF is ideal. It can do a deep survey to flux levels 5000 times fainer than IRAS and can obtain spectra of even the faintest IRAS sources.
1 citations