Dark Gas in the Interstellar Medium

POSTER

Abstract

Most of the interstellar material in disk galaxies, including our own, is too warm and tenuous to form new stars. Yet somehow, clouds cold and dense enough to collapse under their own gravity do occasionally coalesce. This mysterious process is enabled by the gas changing from predominantly free atoms to molecules that enhance radiative cooling. Molecular association is not directly observable, and the gas itself is often ``dark'' to standard probes like spectral line emission from neutral atomic hydrogen or carbon monoxide. But under the right circumstances, this dark gas can be revealed, e.g., as opaque hydrogen emission or absorption, or as infrared continuum radiation from dust grains mixed with hidden molecular hydrogen. We have mapped tracers of such gas over large areas of the Galactic disk at high resolution. We find dark gas clearly revealed in many areas. We present maps of sample features and discuss their properties and relation to Galactic structure.

Authors

  • Steven Gibson

    Western Kentucky University

  • J.K. Hwang

    Western Kentucky University, University of Pardubice, Francis Marion University, Clemson University Professor, Francis Marion University Professor, Undergraduate Administrator, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Austin Peay State University, University Strenwarte-Muenchen, Seoul National University, Gatton Academy for Science and Mathematics, Alabama A\&M University, Cygnus, Center for Nanophase Materials Science at Oak Ridge National Laboratory, Vanderbilt University, Fisk Univ, 2Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, NOVA Center, Western Kentucky University, Department of Physics, Florida A\&M University, Tallahassee, FL-32307, Correlated Electron Materials Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6061 USA, Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA, Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA, The Institute of Optics, University of Rochester, Rochester, NY 14627, USA, Universidade Estadual Paulista (UNESP), Clark Atlanta University, Deapartment of Physics \& Astronomy, Georgia State University, USA, Department of Electrical and Computer Engineering, McGill University, Montreal, QC H3A 2A7, Canada, Oak Ridge National Laboratory, University of South Alabama, Samford University, University of Rochester, University of North Carolina, Chapel Hill, Sandia National Laboratories, New Mexico State University, University of Tennessee Space Institute, Shanghai Jiao Tong University, Shanghai, China, University of Leeds, Leeds, UK, Georgia State University, Atlanta GA, University of Alabama at Birmingham, National High Magnetic Field Laboratory, Prairie View A\&M University, Brookhaven National Laboratory, University of Southern Indiana, Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, JINR(Dubna), Tsinghua Univ., LBNL, Vanderbilt Univ., Vanderbilt Univ./Univ. of Tennessee, Knoxville, Vanderbilt Univ./Univ. of Kentucky, GANIL, Vanderbilt Univ./Union Univ., JINR, ORAU, Tsinghua University, LNBL

  • J.K. Hwang

    Western Kentucky University, University of Pardubice, Francis Marion University, Clemson University Professor, Francis Marion University Professor, Undergraduate Administrator, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Austin Peay State University, University Strenwarte-Muenchen, Seoul National University, Gatton Academy for Science and Mathematics, Alabama A\&M University, Cygnus, Center for Nanophase Materials Science at Oak Ridge National Laboratory, Vanderbilt University, Fisk Univ, 2Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, NOVA Center, Western Kentucky University, Department of Physics, Florida A\&M University, Tallahassee, FL-32307, Correlated Electron Materials Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6061 USA, Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA, Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA, The Institute of Optics, University of Rochester, Rochester, NY 14627, USA, Universidade Estadual Paulista (UNESP), Clark Atlanta University, Deapartment of Physics \& Astronomy, Georgia State University, USA, Department of Electrical and Computer Engineering, McGill University, Montreal, QC H3A 2A7, Canada, Oak Ridge National Laboratory, University of South Alabama, Samford University, University of Rochester, University of North Carolina, Chapel Hill, Sandia National Laboratories, New Mexico State University, University of Tennessee Space Institute, Shanghai Jiao Tong University, Shanghai, China, University of Leeds, Leeds, UK, Georgia State University, Atlanta GA, University of Alabama at Birmingham, National High Magnetic Field Laboratory, Prairie View A\&M University, Brookhaven National Laboratory, University of Southern Indiana, Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, JINR(Dubna), Tsinghua Univ., LBNL, Vanderbilt Univ., Vanderbilt Univ./Univ. of Tennessee, Knoxville, Vanderbilt Univ./Univ. of Kentucky, GANIL, Vanderbilt Univ./Union Univ., JINR, ORAU, Tsinghua University, LNBL

  • J.K. Hwang

    Western Kentucky University, University of Pardubice, Francis Marion University, Clemson University Professor, Francis Marion University Professor, Undergraduate Administrator, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Austin Peay State University, University Strenwarte-Muenchen, Seoul National University, Gatton Academy for Science and Mathematics, Alabama A\&M University, Cygnus, Center for Nanophase Materials Science at Oak Ridge National Laboratory, Vanderbilt University, Fisk Univ, 2Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, NOVA Center, Western Kentucky University, Department of Physics, Florida A\&M University, Tallahassee, FL-32307, Correlated Electron Materials Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6061 USA, Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA, Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA, The Institute of Optics, University of Rochester, Rochester, NY 14627, USA, Universidade Estadual Paulista (UNESP), Clark Atlanta University, Deapartment of Physics \& Astronomy, Georgia State University, USA, Department of Electrical and Computer Engineering, McGill University, Montreal, QC H3A 2A7, Canada, Oak Ridge National Laboratory, University of South Alabama, Samford University, University of Rochester, University of North Carolina, Chapel Hill, Sandia National Laboratories, New Mexico State University, University of Tennessee Space Institute, Shanghai Jiao Tong University, Shanghai, China, University of Leeds, Leeds, UK, Georgia State University, Atlanta GA, University of Alabama at Birmingham, National High Magnetic Field Laboratory, Prairie View A\&M University, Brookhaven National Laboratory, University of Southern Indiana, Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, JINR(Dubna), Tsinghua Univ., LBNL, Vanderbilt Univ., Vanderbilt Univ./Univ. of Tennessee, Knoxville, Vanderbilt Univ./Univ. of Kentucky, GANIL, Vanderbilt Univ./Union Univ., JINR, ORAU, Tsinghua University, LNBL

  • J.K. Hwang

    Western Kentucky University, University of Pardubice, Francis Marion University, Clemson University Professor, Francis Marion University Professor, Undergraduate Administrator, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Austin Peay State University, University Strenwarte-Muenchen, Seoul National University, Gatton Academy for Science and Mathematics, Alabama A\&M University, Cygnus, Center for Nanophase Materials Science at Oak Ridge National Laboratory, Vanderbilt University, Fisk Univ, 2Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, NOVA Center, Western Kentucky University, Department of Physics, Florida A\&M University, Tallahassee, FL-32307, Correlated Electron Materials Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6061 USA, Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA, Department of Electrical and Computer Engineering, University of Rochester, Rochester, NY 14627, USA, The Institute of Optics, University of Rochester, Rochester, NY 14627, USA, Universidade Estadual Paulista (UNESP), Clark Atlanta University, Deapartment of Physics \& Astronomy, Georgia State University, USA, Department of Electrical and Computer Engineering, McGill University, Montreal, QC H3A 2A7, Canada, Oak Ridge National Laboratory, University of South Alabama, Samford University, University of Rochester, University of North Carolina, Chapel Hill, Sandia National Laboratories, New Mexico State University, University of Tennessee Space Institute, Shanghai Jiao Tong University, Shanghai, China, University of Leeds, Leeds, UK, Georgia State University, Atlanta GA, University of Alabama at Birmingham, National High Magnetic Field Laboratory, Prairie View A\&M University, Brookhaven National Laboratory, University of Southern Indiana, Center for Nanophase Materials Sciences at Oak Ridge National Laboratory, JINR(Dubna), Tsinghua Univ., LBNL, Vanderbilt Univ., Vanderbilt Univ./Univ. of Tennessee, Knoxville, Vanderbilt Univ./Univ. of Kentucky, GANIL, Vanderbilt Univ./Union Univ., JINR, ORAU, Tsinghua University, LNBL