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  • ASTROPHYSICS  (10)
  • 1980-1984  (10)
Collection
Keywords
Years
Year
  • 1
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    Infrared emission line studies of the structure and excitation of H II regions (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Maps of five H II regions in one or more of the infrared fine-structure lines of Ne II (12.8 microns), Ar III (9.0 microns), and S IV (10.5 microns) have been obtained with angular resolutions ranging from 4 to 7 arcsec. The observations are used to discuss the morphology and excitation of these nebulae. Considerable diversity is found in the structures of the nebulae, probably resulting from differences in their ages and the circumstances of their formation. In all cases, more ionizing luminosity than would be provided by a single dominant ionizing star appears to be required, although uncertainties in the model nebulae make this conclusion uncertain.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 255
    Format: text
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  • 2
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    Identification of the emission feature near 3.5 microns in the pre-main-sequence star HD 97048 (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-34320)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 265
    Format: text
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  • 3
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    4.6 micron absorption features due to solid phase CO and cyano group molecules toward compact infrared sources (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Spectra obtained at a resolving power of 840, for seven protostellar sources in the region of the 4.67-micron fundamental vibrational band of CO, indicate that the deep absorption feature in W33A near 4.61 microns consists of three features which are seen in other sources, but with varying relative strength. UV-irradiation laboratory experiments with 'dirty ice' temperature cycling allow the identification of two of the features cited with solid CO and CO complexed to other molecules. Cyano group-containing molecules have a lower vapor pressure than CO, and can therefore survive in much warmer environments. The formation and location of the CO- and CN-bearing grain mantles and sources of UV irradiation in cold molecular clouds are discussed. Plausible UV light sources can produce the observed cyano group features, but only under conditions in which local heat sources do not cause evaporation of the CO molecules prior to their photoprocessing.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 276; 533-543
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  • 4
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    The centre of the Galaxy (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: X-ray, gamma-ray and IR observations of the Galaxy's nucleus show that it contains the densest concentration of stars in the Galaxy, as well as a quantity of ionized gas and warm dust, which is clumped into a small number of rapidly expanding individual clouds whose velocities approach + or - 300 km/sec. The detection of electron-positron anihilation radiation, and a peculiar radio point source very close to the galactic center, add to the belief that the nucleus may contain some unusual object, such as a black hole, which is responsible for the cloud velocities and dust-heating radiation observed. Attention is given to IR intensity contours of the region, as well as a review of the observational evidence for the presence of a black hole. It is noted that a massive black hole fails to account for the unusual ionizing radiation field detected.
    Keywords: ASTROPHYSICS
    Type: Nature; 301; Feb. 24
    Format: text
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  • 5
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    Observations of the motion and distribution of the ionized gas in the central parsec of the Galaxy. II (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Observations of infrared fine-structure line emission from compact clouds of ionized gas within Sgr A West are presented. These clouds have diameters of 0.1-0.5 pc, internal velocity dispersions of 100 km/s (FWHM), and line center velocities up to + or - 260 km/s. Their masses are not accurately determined but are probably between 0.1 and 10 solar masses. They are ionized by radiation like that of stars of effective temperature not greater than 35,000 K. The clouds are shown to have lifetimes of 10,000 yr and so must be generated and dissipated at a rate of a few per 1000 yr. From analysis of the distribution of the velocities of the clouds, a most probable mass distribution is derived which includes a central pointlike mass of several x 10 to the 6th solar masses in addition to several x 10 to the 6th solar masses of stars within 1 pc of the center.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 241
    Format: text
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  • 6
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    Infrared line and continuum views of G333.6-0.2 (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A 1-micron CCD picture and maps of the Ne II and Ar III fine-structure lines have been obtained in a region roughly one arcmin in size centered on the core of the compact H II region G333.6 - 0.2. The two emission-line maps show nearly identical intensity distributions, although much different fluxes. The maps are similar to the 1-micron picture smoothed to their angular resolutions. The infrared line of S IV also was detected and appears to have a spatial intensity distribution similar to that of the other fine-structure lines. The 1-micron picture reveals a small number of objects of nearly stellar appearance in the core, suggesting that G333.6 - 0.2 is powered by a compact cluster of sources. Stellar continuum radiation probably is responsible in part for the low equivalent width of the B-gamma line in the core.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 247
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  • 7
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    High spectral and spatial resolution observations of the 12.28 micron emission from H2 in the Orion Molecular Cloud (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The pure rotational S(2) line of H2 at 12.28 microns was sought in 44 positions in the Orion Molecular Cloud with 6-arcsec beams and 35 km/s spectral resolution; and it was detected in 27 positions. The lines are approximately symmetric and have full widths at half-maximum ranging from 100 km/s down to the resolution limit. The distribution of intensities and line shapes is largely consistent with that observed in the 2-micron hydrogen transitions; however, unexpectedly complex line profiles and point-to-point variations in line shapes appear, particularly in the region near IRc9.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 253
    Format: text
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  • 8
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    The abundances of neon, sulfur, and argon in planetary nebulae (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: New infrared observations of Ne II, Ar III, and S IV are used in optical observations of other ionization states of the considered elements to evaluate the abundances of neon, argon, and sulfur in 18 planetary nebulae. Attention is also given to one or more of the infrared lines in 18 other nebulae. It is pointed out that S IV was detected in approximately 90% of the observed objects, while Ar III was found in about 80%, and Ne II in roughly one-third. It is noted that optical observations typically include only a limited region of the nebula, while the infrared measurements frequently involve integration over the entire nebular image.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 249
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  • 9
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    Infrared/optical energy distributions of high-redshift quasars (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: (Previously announced in STAR as N83-11001)
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 265
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  • 10
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    The nature of the central parsec of the Galaxy (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Observations of infrared fine-structure line emission from compact clouds of ionized gas in the galactic center have been reported by Lacy et al (1979, 1980). These observations suggest the existence of a central black hole of nearly 3,000,000 solar masses and require mechanisms to generate, ionize, and dispose of the gas clouds. It is found that the best model to fulfill these requirements involves cloud generation through disruption of red giants by stellar collisions, ionization by a population of stars which is affected either by enhanced metal abundances or the death of the most massive stars, and gas disposal by star formation. Although the existence of a massive black hole cannot be ruled out, it would play no necessary role in this model and may cause the tidal disruption of stars at a rate such that their accretion into the black hole would produce more radiation than is observed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 262
    Format: text
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