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  • 1
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    A multi-wavelength study of 30 Doradus: The Interstellar Medium in a low-metallicity galaxy (1995)
    In:  Other Sources
    Details
    Publication Date: 2013-08-29
    Description: We report maps of the 158 micron (C II) line, the 63 micron and 146 micron (C I) lines, the 2.2 micron Br gamma line, and the 2.6 mm CO (1-0) line toward the 30 Doradus complex in the Large Magellanic Cloud. The maps of all tracers emphasize the shell-like structure of the 30 Doradus region which is seen edge-on. The fact that the molecular gas as traced by CO (1-0) and the photo dissociated gas as traced by (C II) are co-extensive over tens of parsecs can only be explained by a highly fragmented structure of the interstellar medium which allows UV radiation to penetrate deep into the molecular cloud. Clumpiness is also the key to understanding the extremely high (C II)/CO line intensity ratios.
    Keywords: ASTRONOMY
    Type: Astronomical Society of the Pacific, Airborne Astronomy Symposium on the Galactic Ecosystem: From Gas to Stars to Dust, Volume 73; p 141-150
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  • 2
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    Toward astrometric tracking with the infrared spatial interferometer (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Infrared interferometric demonstrations with the University of California, Berkeley's infrared spatial interferometer (ISI) on Mt. Wilson explore the potential of infrared and optical astrometry for deep space tracking, reference frame development, and DSN science. Astrometric data taken and analyzed over the last five years from the ISI have shown that instrumental and atmospheric effects limit current demonstrations. The benefits of sensitivity upgrades, which were performed in 1991 and 1992, have been demonstrated by comparing point-to-point phase fluctuations for the fall 1989 and fall 1992 observing epochs. This comparison showed that point-to-point phase fluctuations due to tropospheric and quantum noise, for optimal integration times of 0.2 sec, are approaching the 0.1-cycle level needed to reliably connect the interferometric phase. The increase in sensitivity, coupled with that arising from very recent hardware upgrades, will greatly enhance phase-connection capabilities necessary for astrometry in the presence of atmospheric refractivity fluctuations. The current data set suggests that atmospheric fluctuations on Mt. Wilson during the best seeing are dominated by a low-lying component, approximately 25 m high, which may be minimized with in situ calibration in the future. During poor seeing conditions that currently prohibit the interferometric phase connection necessary for astrometry, fluctuations seem to be generated by atmospheric inhomogeneities at much higher altitudes above Mt. Wilson. Data taken over the last year suggest that the ISI will soon be able to achieve 50- to 100-nrad astrometry in a single observing session, employing current ground-based laser distance interferometer calibrations to minimize atmospheric effects.
    Keywords: ASTRONOMY
    Type: The Telecommunications and Data Acquisition Report; p 1-9
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  • 3
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    The optical depth of the 158 micrometer (C-12 II) line: Detection of the F=1 yields 0 (C-13 III) hyperfine-structure component (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The first detection of the F = 1 yields 0 hyperfine component of the 158 micrometer (C-13 II) fine structure line in the interstellar medium is reported. A twelve point intensity map was obtained of the (C-13 II) distribution over the inner 190 inch (right ascension) by 190 inch (declination) regions of the Orion nebula using an imaging Fabry-Perot interferometer. The (C-12 II)/(C-13 II) line intensity ratio varied significantly over the region mapped. It is highest (86 plus or minus 9) in the core of the Orion H II region and significantly lower (62 plus or minus 7) in the outer regions of the map, reflecting higher optical depth in the (C-12 II) line here. It is suggested that this enhanced optical depth is the result of limb brightening of the optically thin (C-13 II) line at the edges of the bowl-shaped H II region blister. If the C-12/C-13 abundance ratio is 43, the (C-12 II) line in the inner regions of the Orion nebula, has a low optical depth: tau sub 12 approximately = 0.75 plus or minus 0.25. The optical depth together with the large brightness temperature of the (C-12 II) line (approximately 160 K) requires that the excitation temperature of the P-2 sub 3/2 level be approximately 310 K, in very good agreement with the previous analysis of the physical conditions of the Orion interface region based on fine structure line intensity ratios and photodissociation region models. If the C-12/C-13 abundance ratio is 67, the line optical depth is somewhat larger (tau sub 12 approximately = 1.85), and the transition excitation temperature is somewhat smaller (approximately 190 K) than that predicted by these models. The present results therefore support values approximately = 43 for the C-12/C-13 abundance ratio in the Orion nebula.
    Keywords: ASTRONOMY
    Type: NASA-CR-190255 , NAS 1.26:190255 , MPE-PREPRINT-211
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  • 4
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    Far-infrared Spectroscopy of Galaxies: the 158 Micron C(+) Line (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-18
    Description: The C II 158 micron fine structure line in six gas rich galaxies was investigated. These data are combined with other measurements of the C II line (in various galactic sources) and are compared to studies of the CO J = approaches O rotational line at 2.6 mm, the H I 21 cm line, and the far infrared continuum emission in the same objects.
    Keywords: ASTRONOMY
    Type: NASA. Ames Research Center Airborne Astron. Symp.; p 292-297
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  • 5
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    Recent astronomical results from the infrared spatial interferometer and their implications for LOUISA (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new heterodyne interferometer for the atmospheric window from 9 to 12 microns was developed during the past five years. This instrument, called the Infrared Spatial Interferometer (ISI), was designed to use earth rotation aperture synthesis techniques developed in radio interferometry. It was moved to Mt. Wilson, California, in January 1988 and first fringes were obtained in June of that year. Systematic observations of some of the brighter late-type stars began shortly after the first fringes were obtained. We describe the basic principles and design of the ISI and give an overview of some of the initial results obtained from these observations. The implications of our work to the proposed Lunar Optical/UV/IR Synthesis Array (LOUISA) are discussed. We also analyze the conditions for the maximum signal-to-noise ratio of such an interferometer as a function of wavelength. The optimum wavelength is found to depend on the assumed scaling relation between telescope area and wavelength.
    Keywords: ASTRONOMY
    Type: New Mexico Univ., A Lunar Optical-Ultraviolet-Infrared Synthesis Array (LOUISA); p 75-92
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  • 6
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    Far-infrared emission lines of CO and OH in the Orion-KL molecular shock (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations of far infrared rotational emission lines which arise in the shocked gas associated with Orion-Kl are presented, including detections of the CO J = 34 yields 33, J = 31 yields 30, J = 26 yields 25, and OH sup 2 PI sub (3/2) J sup P = 7/2(-) yields 5/2(+) emission lines, as well as improved measurements of the CO J = 22 yields 21 and OH sup 2 PI sub (3/2) J = 5/2 yields 3/2 lines. These lines are observed to have velocity widths of Del V approx. 20 to 30 km/sec, somewhat less than either the 2 micro H sub 2 lines or the high velocity plateau component of the millimeter wave CO lines seen in this object. An H sub 2 column density of approx. 3 x 10 to the 21st power, a total mass of approx. 1 solar mass and characteristic temperature and density T approx. 750 K and approx. 2 x 10 to the 6th power per cu cm can be derived from the CO intensities. The density is too low by at least an order of magnitude for the observed infrared H sub 2 and far infrared CO emission to be accounted for by a purely hydrodynamic shock, and support is lent to hydromagnetic shock models. From the present measurements, the relative abundance of CO is estimated to be CO H sub 2 = 1.2 x .0001, corresponding to 20% of the cosmic abundance of C existing in the form of CO. The average relative abundance of OH in the shocked gas is O/H sub 2 or = 5 x 10 to the -7th power. An upper limit to the intensity of the HD J = 1 yields 0 line is used to derive an upper limit of tau or = 3 for the D/H relative abundance in the Orion cloud core.
    Keywords: ASTRONOMY
    Type: NASA-TM-86721 , REPT-85222 , NAS 1.15:86721
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  • 7
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    Far-IR spectroscopy of the galactic center: Neutral and ionized gas in the central 10 pc of the galaxy (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 3P1 - 3P2 fine structure line emission from neutral atomic oxygen at 63 microns in the vicinity of the galactic center was mapped. The emission is extended over more than 4' (12 pc) along the galactic plane, centered on the position of Sgr A West. The line center velocities show that the O I gas is rotating around the galactic center with an axis close to that of the general galactic rotation, but there appear also to be noncircular motions. The rotational velocity at R is approximately 1 pc corresponds to a mass within the central pc of about 3 x 10(6) solar mass. Between 1 and 6 pc from the center the mass is approximately proportional to radius. The (O I) line probability arises in a predominantly neutral, atomic region immediately outside of the ionized central parsec of out galaxy. Hydrogen densities in the (O I) emitting region are 10(3) to 10(6) cm(-3) and gas temperatures are or = 100 K. The total integrated luminosity radiated in the line is about 10(5) solar luminosity, and is a substantial contribution to the cooling of the gas. Photoelectric heating or heating by ultraviolet excitation of H2 at high densities (10(5) cm(-3)) are promising mechanisms for heating of the gas, but heating due to dissipation of noncircular motions of the gas may be an alternative possibility. The 3P1 - 3P0 fine structure line of (O III) at 88 microns toward Sgr A West was also detected. The (O III) emission comes from high density ionized gas (n 10(4) cm(-3)), and there is no evidence for a medium density region (n 10(3) cm(-3)), such as the ionized halo in Sgr A West deduced from radio observations. This radio halo may be nonthermal, or may consist of many compact, dense clumps of filaments on the inner edges of neutral condensations at R or = 2 pc.
    Keywords: ASTRONOMY
    Type: NASA-CR-166510 , NAS 1.26:166510
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  • 8
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    Detection of shocked atomic gas in the Kleinmann-Low nebula (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 63 micrometer (3)p(1)-(3)P(2) fine structure line emission of neutral atomic oxygen at the center of the Orion nebula with a resolution of 30" is presented. There are three main emission peaks. One is associated with the region of strongest thermal radio continuum radiation close to the Trapezium cluster, and probably arises at the interface between the HII region and the dense Orion molecular cloud. The other two line emission peaks, associated with the Kleinmann Low nebula, are similar in both distribution and velocity to those of the 2 micrometer S(1) line of molecular hydrogen and of the high velocity wings of rotational CO emission. The OI emission from the KL nebula can be produced in the shocked gas associated with the mass outflows in this region and is an important coolant of the shocked gas.
    Keywords: ASTRONOMY
    Type: NASA-TM-85967 , A-9774 , NAS 1.15:85967
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  • 9
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    Spatial heterodyne interferometry of VY Canis Majoris, Alpha Orionis, Alpha Scorpii, and R Leonis at 11 microns (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
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  • 10
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    Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.
    Keywords: ASTRONOMY
    Type: NASA-CR-145629
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