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  • Astronomy  (4)
  • CO abundance  (1)
  • formation  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Cosmic evolution of the biogenic elements and compounds (1993)
    Springer
    The astronomy and astrophysics review 5 (1993), S. 1-35 
    Details
    ISSN: 1432-0754
    Keywords: Galaxy ; evolution-Stars ; abundances, mass loss-Interstellar medium ; dust, molecules-Solar System ; formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary This paper traces the evolution of the biogenic elements H, C, N, O, P and S from their creation by cosmic nucleosynthesis to their inclusion in living systems on the surface of the Earth. Evidence for the presence of significant prebiotic molecules in interstellar clouds and in primitive meteorites is reviewed. The possible relevance of this discovery to the origin of life on Earth is assessed in the light of evidence suggesting that such molecules could not easily be synthesized in a primitive CO2-dominated terrestrial atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872922
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Carbon monoxide frosts in the interstellar medium (1991)
    Springer
    The astronomy and astrophysics review 2 (1991), S. 167-189 
    Details
    ISSN: 1432-0754
    Keywords: Interstellar dust ; grain mantles ; CO abundance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary The presence of solid carbon monoxide (CO) on interstellar grains was confirmed observationally in 1984 with the detection of infrared absorption at 4.67μm wavelength in several molecular clouds. Subsequent observations suggest that solid CO is ubiquitous in the quiescent molecular cloud environment. In some lines of sight, the degree of frosting on to grains is sufficient to reduce appreciably the abundance of CO remaining in the gas, a result of considerable astrophysical significance: in addition to its importance as a tracer of molecular material, CO is vital to the production of many polyatomic molecules by gas phase reaction schemes, and its depletion could have a dramatic effect on the abundances of more complex carbon-bearing molecules. The infrared spectrum of solid CO provides an important diagnostic of the chemical composition and thermal evolution of grain mantles, leading to the prediction that CO2 is also present in solid form. As it is now some six years since observations of interstellar solid CO were first reported, this is an appropriate time to review the topic and to suggest some directions for future research. The introduction (Sect. 1) attempts to place the subject in its broader astrophysical context. The infrared observations and their implications are discussed in detail in Sect. 2. The question of the degree of CO depletion implied by the observations of both solid state and gas phase CO is re-examined in Sect. 3. We assess the possibility of CO detection by means of solid state absorption or luminescence in the ultraviolet in Sect. 4. Future prospects are summarised in the final section.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00872766
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  • 3
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    The Extinction Properties of Heavily-Reddened Lines of Sight in the Galaxy (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: Recent studies of the 3.4 micron C-H stretch absorption feature indicate a strong correlation between it and the 10 micron silicate band over a wide range of extinctions (A(sub v) = 3.9-31 magnitudes), but the relationships between their optical depths and the visual extinction are particularly poorly constrained at intermediate extinctions between 15 and 20 magnitudes. The objective prism survey published by Stephenson may help to alleviate this difficulty. It lists more than 400 extremely red stars lacking molecular absorption bands, suggesting that these are hot blue stars reddened by long path lengths of the Galactic ISM. The intrinsic properties of these stars are unfortunately only loosely constrained, and JHK photometry therefore does not accurately determine the interstellar extinction. Using the POSS I plates, we have attempted to produce self-consistent spectral types, luminosity classes and extinctions for the stars which Stephenson claims to be most heavily reddened. 14 out of 25 sources studied are consistent with OB supergiants. The results are highly sensitive to upper limits in the blue plate, and are not always consistent with Stephenson's claims of much higher reddening than that of a typical member of the Cygnus OB2 association. For the most heavily-reddened sources studied, a B-magnitude based on the faintest measurable value on the blue plate yielded a lower limit of about 9 magnitudes on the extinction.
    Keywords: Astronomy
    Type: From Stardust to Planetesimals: Contributed Papers; 101-104; NASA-CP-3343
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  • 4
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    Processing of Icy Mantles in Protostellar Envelopes (1996)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The 4.5-4.8 micron spectral region provides two potential diagnostics of radiative or thermal processing of interstellar ices in the environs of embedded stars in molecular clouds. A broad absorption feature centered at 4.62 micron is seen in the spectra of several young stellar objects (YSO's) and attributed to C-N triple bonds in a nitrile or isonitrile. As CN-bearing solids in the laboratory are produced by energetic radiative processing of ices containing nitrogen, detection of this feature in YSO's is taken as evidence for (1) the presence of nitrogen in the unprocessed cloud ices, and (2) evolution of the ice in the vicinity of the embedded source. The adjacent feature at 4.67 micron, identified with solid CO, provides not only quantitative information on CO itself but also indirect evidence for the presence of other species; its position and profile are sensitive to the molecular environment of the CO molecules in the ice mantle, and may be used to constrain both the composition and thermal/radiative history of the ice. One important example is the possibility to detect CO2, which is produced easily in the laboratory by UV irradiation of CO-rich or CH3OH-rich ices. CO embedded in a CO2 matrix gives a characteristic spectral signature distinct from other CO-bearing mixtures investigated to date. We have obtained CO absorption profiles of three young stellar objects in order to investigate their ice mantle composition.
    Keywords: Astronomy
    Type: From Stardust to Planetesimals: Contributed Papers; 131-134; NASA-CP-3343
    Format: text
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  • 5
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    Interstellar Extinction, Polarization, and Grain Alignment in High-Latitude Clouds (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: From new near-infrared photometry and optical and near-infrared polarimetry, we determine the ratio of total-to-selective extinction and the wavelength of maximum polarization for a sample of stars behind molecular clouds at high Galactic latitude. In general, we find that at high latitude, these parameters have values comparable to those observed closer to the Galactic plane. One notable exception is the line of sight towards HD 210121, where unusually small values of these parameters suggest an abundance of small grains in the foreground cloud.
    Keywords: Astronomy
    Type: From Stardust to Planetesimals: Contributed Papers; 97-100; NASA-CP-3343
    Format: text
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  • 6
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    Infrared Observations of Hot Gas and Cold Ice Toward the Low Mass Protostar Elias 29 (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: We have obtained the full 1-200 micrometer spectrum of the low luminosity (36 solar luminosity Class I protostar Elias 29 in the rho Ophiuchi molecular cloud. It provides a unique opportunity to study the origin and evolution of interstellar ice and the interrelationship of interstellar ice and hot core gases around low mass protostars. We see abundant hot CO and H2O gas, as well as the absorption bands of CO, CO2, H2O and "6.85 micrometer" ices. We compare the abundances and physical conditions of the gas and ices toward Elias 29 with the conditions around several well studied luminous, high mass protostars. The high gas temperature and gas/solid ratios resemble those of relatively evolved high mass objects (e.g. GL 2591). However, none of the ice band profiles shows evidence for significant thermal processing, and in this respect Elias 29 resembles the least evolved luminous protostars, such as NGC 7538 : IRS9. Thus we conclude that the heating of the envelope of the low mass object Elias 29 is qualitatively different from that of high mass protostars. This is possibly related to a different density gradient of the envelope or shielding of the ices in a circumstellar disk. This result is important for our understanding of the evolution of interstellar ices, and their relation to cometary ices.
    Keywords: Astronomy
    Type: Rept-2000-9
    Format: application/pdf
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