A full spectral survey was carried out towards the giant molecular cloud complex, Sagittarius B2 (Sgr B2), using the Infrared Space Observatory (ISO) Long Wavelength Spectrometer (LWS) Fabry–Pérot ...mode. This provided complete wavelength coverage in the range 47–196 μm (6.38–1.53 THz) with a spectral resolution of 30–40 km s−1. This is a unique data set covering wavelengths inaccessible from the ground. It is an extremely important region of the spectrum as it contains both the peak of the thermal emission from dust, and crucial spectral lines of key atomic (O i, C ii, O iii, N ii and N iii) and molecular species (NH3, NH2, NH, H2O, OH, H3O+, CH, CH2, C3, HF and H2D+). In total, 95 spectral lines have been identified and 11 features with absorption depth greater than 3σ remain unassigned. Most of the molecular lines are seen in absorption against the strong continuum, whereas the atomic and ionic lines appear in emission (except for absorption in the O i 63 μm and C ii 158 μm lines). Sgr B2 is located close to the Galactic Centre and so many of the features also show a broad absorption profile due to material located along the line of sight. A full description of the survey data set is given with an overview of each detected species and final line lists for both assigned and unassigned features.
This essay by the distinguished German art historian Max Imdahl (1925-88) outlines Imdahl's career and art historical practice, which provide fascinating insights into the development of the ...discipline in postwar Germany. Imdahl was founding member of the Institute of Art History at the new Ruhr-University in Germany's most industrialized region; he also pioneered seminars on contemporary art for trade union members of the local chemical industry, and his advocacy of contemporary art led to his advisory role for "documenta 6." While revealing the controversial status of contemporary art in mid-twentieth-century Germany, he considers it as a possible hermeneutic interpretive condition of traditional art. Imdahl is further concerned with the process involved in interpreting works of art, including the relationship between image and verbal expression. He introduces a new term-Ikonik-to define the comprehension of an image that is derived exclusively from the process of viewing. His analysis of various works of art by Giotto, Ruisdael, Barnett Newman and others demonstrates how Ikonik differs from Sedlemayr's "structural analysis" and relates to Panofsky's concepts (Iconography, Iconology). He concludes that Ikonik is a fundamental presupposition for addressing the cognitive structure imminent in an image.
We have carried out a high spectral resolution (λ/Δλ∼ 6800-9700) line survey towards the Orion Kleinmann-Low (KL) cluster from 44 to 188 μm. The observations were taken with the Long Wavelength ...Spectrometer (LWS) in Fabry-Pérot mode, on board the Infrared Space Observatory (ISO). A total of 152 lines are clearly detected and a further 34 features are present as possible detections. The spectrum is dominated by the molecular species H2O, OH and CO, along with O i and C ii lines from photodissociation region (PDR) or shocked gas and O iii and N iii lines from the foreground M42 H ii region. Several isotopic species, as well as NH3, are also detected. HDO and H3O+ are tentatively detected for the first time in the far-infrared (FIR) range towards Orion KL. A basic analysis of the line observations is carried out, by comparing with previous measurements and published models and deriving rotational temperatures and column densities in the case of the molecular species.
Analysis of the O i and C ii fine structure lines indicates that although a shock model can reproduce the observed O i surface brightness levels, it falls short of the observed C ii level by more than a factor of 30. A PDR model can reproduce the O i 63.2 μm and C ii surface brightness levels within 35 per cent, although overpredicting the LWS O i 145.5 μm-emission by a factor of 2.7. The 70 water lines and 22 OH lines detected by the survey appear with mainly P Cygni profiles at the shortest survey wavelengths and with mainly pure emission profiles at the longest survey wavelengths. The emission and absorption velocity peaks of the water and OH lines indicate that they are associated with gas expanding in the outflow from the KL cluster. The estimated column densities are (2-5) × 1014 cm−2 for H2O and (2.5-5.1) × 1016 cm−2 for OH. The 26 detected CO lines confirm the presence of three distinct components, with temperature and column density combinations ranging from 660 K, 6 × 1017 cm−2 to 360 K, 2 × 1019 cm−2. Comparison of the surface brightnesses and integrated fluxes of the CO lines measured in the 80-arcsec LWS beam with those measured previously by the Kuiper Airborne Observatory (KAO) in a 44-arcsec beam shows similar surface brightnesses in the different beams for the lowest-J CO lines and similar integrated fluxes in the different beams for the highest-J CO lines, indicating that emission from the former lines has a uniform surface brightness within the LWS beam, while the latter lines originate from a region less than 44 arcsec in diameter. The complexity of the region requires more sophisticated models for the interpretation of all the line observations.
The ISO LWS far-infrared spectrum of the ultraluminous galaxy Mrk 231 shows OH and H sub(2)O lines in absorption from energy levels up to 300 K above the ground state, and emission in the O i 63 mum ...and C ii 158 mum lines. Our analysis shows that OH and H sub(2)O are radiatively pumped by the far-infrared continuum emission of the galaxy. The absorptions in the high- excitation lines require high far-infrared radiation densities, allowing us to constrain the properties of the underlying continuum source. The bulk of the far-infrared continuum arises from a warm (image K), optically thick medium of effective diameter 200-400 pc. In our best-fit model of total luminosity image, the observed OH and H sub(2)O high-lying lines arise from a luminous region with radius image100 pc. The high surface brightness of this component suggests that its infrared emission is dominated by the AGN. The derived column densities image cm super(-2) and image cm super(-2) may indicate X-ray dominated region (XDR) chemistry, although significant starburst chemistry cannot be ruled out. The lower-lying OH, C ii 158 mum, and O i 63 mum lines arise from a more extended (image350 pc) starburst region. We show that the C ii deficit in Mrk 231 is compatible with a high average abundance of C super(+) because of an extreme overall luminosity to gas mass ratio. Therefore, a C ii deficit may indicate a significant contribution to the luminosity by an AGN, and/or by extremely efficient star formation.
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