Molecular Clouds As Probes Of Milky Way Structure And Interstellar Turbulence
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Molecular Clouds as Probes of Milky Way Structure and Interstellar Turbulence
Abstract: The Galactic Ring Survey, a 13 CO survey of the first quadrant of the Milky Way, is used to probe the spiral structure of the Galaxy and to constrain the formation and turbulent structure of molecular clouds. A sample of 829 molecular clouds has been identified in the Galactic Ring Survey (GRS). Kinematic distances to 750 of these GRS clouds are derived. The Galactic surface mass density of molecular gas is subsequently computed from 13 CO and 12 CO emission detected in the GRS and the University of Massachusetts-Stony Brook surveys. The Galactic distribution of molecular clouds is strongly enhanced along the Scutum-Crux, Sagittarius, and Perseus arms. These molecular data are consistent with a four-arm model of the Galaxy, while the locations of the Scutum-Crux and Perseus arms are consistent with the distribution of the old stellar population inferred from infrared maps. Physical properties of molecular clouds such as size, mass, and density, are also derived in order to compare clouds located inside and outside spiral arms, and to constrain formation models. Molecular clouds located inside inferred spiral arms are found to be more massive, to have higher surface mass densities, and to be more strongly gravitationally bound than inter-arm clouds. This supports cloud formation models involving spiral structure and suggests that molecular clouds must have lifetimes of a few million years. The turbulent structure of molecular clouds is a fundamental component of star formation. The GRS is the first large scale, fully sampled 13 CO survey of the Galaxy allowing the observation of the sub-parsec-scale structure of molecular clouds. Principal Component Analysis applied to both GRS clouds and numerical simulations allows the derivation of turbulent energy spectra over scales ranging from 0.1 pc to 50 pc. The slope of the energy spectrum, E(k), versus the wavenumber, k, obtained for the GRS clouds is consistent with compressible, intermittent turbulence. The slopes and amplitudes of the energy spectra of the clouds are fairly constant over three decades of masses, which indicates that turbulence is driven on large scales by an external, Galactic pool of kinetic energy.
From Cosmological Structures to the Milky Way
Volume 18 continues the Reviews in Modern Astronomy with twelve invited reviews and highlight contributions which were presented during the International Scientific Conference of the Astronomical Society on the topic "From Cosmological Structures to the Milky Way", held in Prague, Czech Republic, September 20 to 25, 2004. The contributions to the meeting published in this volume discuss, among other subjects, X-ray astronomy, cosmology, star formation and the Galactic Centre.
Exploring the Cosmic Frontier
Author: A.P. Lobanov
language: en
Publisher: Springer Science & Business Media
Release Date: 2007-02-15
In the coming decades, astrophysical science will benefit enormously from the construction and operation of several major international ground- and space based facilities, such as ALMA, Herschel/Planck, and SKA in the far infrared to radio band, Extremely Large Telescopes, JWST and GAIA in the optical to near infrared regime, XEUS and Constellation-X in the X-ray, and GLAST in the Gamma-ray regime. These and other new instruments will have a major impact in a wide range of scientific topics including the cosmological epoch of reionization, galactic dynamics and nuclear activity, stellar astronomy, extra-solar planets, gamma-ray bursts, X-ray binaries, and many others. On May 18-21, 2004, the Max-Planck-Society’s Harnack-Haus in Dahlem, Berlin hosted the international symposium "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century". The symposium in Berlin was dedicated to exploring the complementarity and synergies between different branches of astrophysical research, by presenting and discussing the fundamental scientific problems that will be addressed by major future astrophysical facilities in the next few decades. This book contains 70 papers from the meeting and is intended to give a lasting account of a snapshot of an evolving scientific discourse and interaction throughout our field of research.