Showing papers by "Charles H. Townes published in 1987"
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TL;DR: In this article, a review of recent observations and theoretical models of the Galactic center (GC) is given, including the stellar cluster, radio continuum emission and interstellar clouds, the Sgr A complex, and X-ray and gamma emission.
Abstract: Recent observations and theoretical models of the Galactic center (GC) are reviewed An overview of phenomena seen in the GC is given, including the stellar cluster, radio continuum emission and interstellar clouds, the Sgr A complex, and X-ray and gamma emission Also discussed are the energetics and physical conditions in the central 4 pc (star burst or central source?); the circumnuclear ring, ionized streamers, and relativistic and hot gas in the cavity; the mass distribution and the possibility of a massive black hole, and the central 01 pc (Sgr A and IRS 16) Diagrams, graphs, photographs, and tables of numerical data are provided
209 citations
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Harvard University1, Bell Labs2, Kirtland Air Force Base3, Sandia National Laboratories4, University of Washington5, United States Military Academy6, Columbia University7, Massachusetts Institute of Technology8, Cornell University9, Lawrence Berkeley National Laboratory10, University of Illinois at Urbana–Champaign11, University of Arizona12, California Institute of Technology13, Stanford University14, PARC15, Lawrence Livermore National Laboratory16, University of California, Berkeley17, University of California, Los Angeles18
100 citations
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15 Apr 1987
TL;DR: In this paper, the authors present new measurements of CO submillimeter (J = 7..-->..6) and far-infrared lines in the Galactic center and derive the physical conditions of the dense, warm molecular gas at different positions in the Sgr a circum-nuclear ring.
Abstract: We present new measurements of CO submillimeter (J = 7 ..-->..6) and far-infrared (J = 14 ..-->.. 13, J = 21 ..-->.. 20) lines in the Galactic center. The new data, together with earlier CO measurements, are used to derive the physical conditions of the dense, warm molecular gas at different positions in the Sgr a circum-nuclear ring. From the inner edge of the ring at Rapprox.1.7 pc to Rapprox.6 pc the gas pressure decreases proportional to R/sup -1.6//sup +- //sup 0.4/. The best fit excitation curves indicate that both density and temperature decrease with distance from the center. There is also an azimuthal excitation gradient in the ring. If the molecular gas is directly heated from the center by UV radiation or mass outflow the decrease of excitation is a natural consequence of the R/sup -2/ dependence of the energy density. In the more likely scenario of shock heating fed by the large turbulence of the gas throughout the ring, the excitation gradient may reflect variations in gas density and heating efficiency.
1 citations