Showing papers by "Michael W. Werner published in 1992"
TL;DR: Forbidden O I 63-micron and forbidden Si II 35micron fine-structure line emission in M17SW was mapped, and the intensities of the forbidden OI 63 and 146 microns, forbidden SI II 35 microns and forbidden C II 158 microns were measured at four positions as discussed by the authors.
Abstract: Forbidden O I 63-micron and forbidden Si II 35-micron fine-structure line emission in M17SW was mapped, and the intensities of the forbidden O I 63 and 146 microns, forbidden Si II 35 microns, and forbidden C II 158 microns were measured at four positions. New 50- and 100-micron continuum maps of the M17SW cloud at comparable resolution to the FIR line observations are presented. Analysis in terms of a homogeneous model yields an incident UV field of 56,000 habings, a density of 30,000 cu cm, and a temperature of about 300 K for the atomic gas. It is concluded that the M17SW photodissociation region is clumpy in nature. The observed forbidden Si II and high-J CO imply the presence of high-density clumps. The clumps dominate the emission in the forbidden O I, Si II, and high-level CO lines, while the forbidden C II, C I, and low-level CO arise mostly in the interclump gas. The extended (about 15 pc) forbidden C II and forbidden C I emission is attributed to the halo gas.
81 citations
TL;DR: In this article, high signal-to-noise 50-and 90-micron continuum maps of the central 5 x 4 arcmin of the Galaxy made from observations on the Kuiper Airborne Observatory are presented.
Abstract: High signal-to-noise 50- and 90-micron continuum maps of the central 5 x 4 arcmin of the Galaxy made from observations on the Kuiper Airborne Observatory are presented. Dust and luminosity distribution models which are consistent with the data are presented. These data are consistent with a flared disk of dust, centered on the position of Sgr A*, having a central cavity wth a radius of 1 pc. Strong evidence is found for a large amount of dust between the northern and eastern ionized arms located within the cavity. It is argued that this 'tongue' of dust is optically thick at UV and visible wavelengths. Both smooth and clumped dust distributions, consistent with the disk and central cavity, are considered. For the smooth distribution, the dust heating is found to be consistent with the data only for a central UV source of a few x 10 exp 6 solar luminosities.
81 citations
TL;DR: In this article, the authors measured the polarization of the 100 micron continuum emission at 14 positions in the dense, warm molecular cloud associated with the arched filaments, or the "bridge", of the radio arc near the Galactic center.
Abstract: The polarization of the 100 micron continuum emission has been measured at 14 positions in the dense, warm molecular cloud associated with the arched filaments, or the 'bridge', of the radio arc near the Galactic center. At all positions the percent polarization is found to be quite large, ranging up to 6.5 percent. The polarization is interpreted in terms of thermal emission by magnetically aligned dust grains. The directions of the polarization vectors then indicate that the magnetic field is (1) parallel to the long dimension of the thermal radio filaments, and (2) very uniform on scales of 1-10 pc. Of several explanations for the inferred field geometry, the simplest is that it results from the unusually large dynamical shear in the emitting cloud.
37 citations
TL;DR: The NASA Kuiper Airborne Observatory was used to observe far-infrared continuum brightness fluctuations in the lower chromosphere due to solar 5 minute oscillations on the quiet sun as discussed by the authors.
Abstract: The NASA Kuiper Airborne Observatory was used to observe far-infrared continuum brightness fluctuations in the lower chromosphere due to solar 5 minute oscillations on the quiet sun. Brightness measurements made at 50, 100, 200, and 400 microns show a strong correlation with visible-line Doppler measurements from photospheric and chromospheric altitudes. The motion of the chromosphere is nearly in phase over a large range of heights, while the infrared brightness lags the Doppler velocity by phases varying from significantly less than 90 deg at low altitudes to nearly 90 deg at higher altitudes. It is proposed that this is the result of a nonadiabatic response of the chromospheric gas to compression and may indicate an important mechanism for wave dissipation. Thermal relaxation times ranging from about 40 s at 340 km above the tau(5000) = 1 photosphere to about 300 s at 600 km are proposed.
11 citations
TL;DR: The Space Infrared Telescope Facility (SIRTF) as discussed by the authors is a one meter class cryogenically cooled observatory for infrared astronomy, and the characteristics of the Infrared Array Camera, Infrared Spectrograph, and Multiband Imaging Photometer on SIRTF are summarized and compared with those of IRAS.
Abstract: SIRTF (Space Infrared Telescope Facility), a one meter class cryogenically cooled observatory for infrared astronomy, is briefly discussed. The characteristics of the Infrared Array Camera, Infrared Spectrograph, and Multiband Imaging Photometer on SIRTF are summarized and the SIRTF characteristics are compared with those of IRAS. The key scientific aims and capabilities of SIRTF are outlined.
8 citations
TL;DR: The Space Infrared Telescope Facility (SIRTF) as discussed by the authors uses a large area, 2D infrared array detectors to provide wide-field (7 arcmin) and diffraction-limited imaging over the spectral region from 2 to 30 microns.
8 citations
TL;DR: SIRTF as mentioned in this paper is a one metre class, cryogenically cooled observatory for infrared astronomy, which will achieve a 100- to 10,000-fold increase in sensitivity relative to previous facilities for observations between 3 and 700 microns.
Abstract: SIRTF will be a one metre class, cryogenically cooled observatory for infrared astronomy. It will achieve a 100- to 10,000-fold increase in sensitivity relative to previous facilities for observations between 3 and 700 microns. Three focal-plane instruments will provide photometric, imaging, and spectroscopic capabilities using large-format detector arrays. A five year lifetime in a 100,000 km orbit is planned. On-target efficiency should approach 85%, and roughly 85% of the time will be devoted to General Observer use. SIRTF will build on the successes of IRAS and COBE and on those to be obtained with ISO. SIRTF will complete NASA’s planned family of Great Observatories. Table I compares anticipated capabilities of SIRTF with those of IRAS.
4 citations