Molecular and Atomic Hydrogen Cloud Correlations in the Interstellar Medium of the Galaxy

ORAL

Abstract

A key question in Galactic astrophysics is how the cold, relatively dense clouds that form new stars are assembled from the warmer, more diffuse interstellar medium (ISM). We are investigating the relationship between neutral atomic hydrogen (HI) and molecular hydrogen (H2) gas to find where molecules may be actively forming in cooling clouds prior to star formation. We use HI 21cm-line self-absorption (HISA) to identify the coldest atomic gas that is most likely associated with forming molecules, and we use carbon monoxide (CO) 2.6mm line emission as a proxy for H2, which does not have suitable ground-state transitions for direct mapping. We have measured the fraction of HISA with CO emission and CO with HISA in a variety of different Galactic plane survey data sets. We see a stronger correspondence of HISA and CO in the inner parts of the Galaxy, and a weaker correspondence elsewhere. However, this trend may arise from chance alignments of unrelated clouds being more likely in the inner Galaxy rather than true physical correlation.

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Authors

  • Ward Howard

    Union University

  • Steven Gibson

    Western KY University

  • Chris Neu

    Florida State University, NHMFL, Institut Neel, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China, Florida State University, Department of Physics, Florida State University, Tallahassee, FL, Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, Florida State University, National High Magnetic Field Laboratory, Institute of Physics, Chinese Academy of Sciences, China, Austin Peay State University, University of Pardubice, Davidson College, Covenant College, Lookout Mtn, GA 30750, Russian Academy of Sciences, Moscow, RU, University of Tennessee Space Institute, Tullahoma, TN, USA, Sandia National Laboratories,* Albuquerque, NM, Arkansas State University, Jonesboro, AK, None, Mississippi State University, Mississippi State University Department of Physics and Astronomy, Florida State University and the National High Magnetic Field Laboratory, Faculte des Sciences et Techniques and Universite Aix-Marseille, MIT Haystack Observatory, Departments of Chemistry and Physics, University of Tennessee of Chattanooga, Departments of Chemistry and Physics, University of Tennessee at Chattanooga, Western Kentucky University, Thomas Jefferson National Accelerator Facility, Newport News, VA, Fermilab, University of Virginia and Fermilab, Indiana University Bloomington, Indiana University Health Proton Therapy Center, University of North Florida, National Superconducting Cyclotron Laboratory, Michigan State University, Flordia State University, Louisiana State University, Washington University, Argonne National Laboratory, Lawrence Berkeley National Laboratory, Department of Physics, Florida State University., JINR, Tsinghua University, LBNL, LBNL/Vanderbilt University, Vanderbilt University, Florida A\&M University, Georgia Institute of Technology, Department of Physics, Virginia Tech, Gatton Academy, Exeter University, Florida International University, Office of Research, University of North Florida, Physics Department, University of North Florida, NSCL, Michigan State University, Physics Department, Florida State University, University of Tennessee-Knoxville, Neel Institut, Kazan Federal University, Bielefeld University, Ben Gurion University, LCIB - CEA, University of Georgia, Lawrence Livermore National Laboratory, Livermore, CA 94550, NHMFL, Tallahassee, USA, Department of Chemistry, University of Waterloo, Ontario, Canada, NHMFL, Tallahassee FL 32310 USA, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany, Wigner Research Center for Physics, Budapest, Hungary, Experimental physics II, University of Augsburg, Germany, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, National High Magnetic Field Laboratory Florida State University, Tallahassee, Florida 32310, IM2NP-CNRS (UMR 7334) and Universite Aix-Marseille, National High Magnetic Field Laboratory Applied Superconductivity Center, Heifei National Lab for Physical Science at Microscale, USTC, Institute of Physics, Chinese Academy of Sciences, Department of Electrical Engineering, Rice University, National High Magnetic Field Laboratory, National High Magnetic Field Laboratory/FSU, University of Virginia

  • Chris Neu

    Florida State University, NHMFL, Institut Neel, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, China, Florida State University, Department of Physics, Florida State University, Tallahassee, FL, Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, Florida State University, National High Magnetic Field Laboratory, Institute of Physics, Chinese Academy of Sciences, China, Austin Peay State University, University of Pardubice, Davidson College, Covenant College, Lookout Mtn, GA 30750, Russian Academy of Sciences, Moscow, RU, University of Tennessee Space Institute, Tullahoma, TN, USA, Sandia National Laboratories,* Albuquerque, NM, Arkansas State University, Jonesboro, AK, None, Mississippi State University, Mississippi State University Department of Physics and Astronomy, Florida State University and the National High Magnetic Field Laboratory, Faculte des Sciences et Techniques and Universite Aix-Marseille, MIT Haystack Observatory, Departments of Chemistry and Physics, University of Tennessee of Chattanooga, Departments of Chemistry and Physics, University of Tennessee at Chattanooga, Western Kentucky University, Thomas Jefferson National Accelerator Facility, Newport News, VA, Fermilab, University of Virginia and Fermilab, Indiana University Bloomington, Indiana University Health Proton Therapy Center, University of North Florida, National Superconducting Cyclotron Laboratory, Michigan State University, Flordia State University, Louisiana State University, Washington University, Argonne National Laboratory, Lawrence Berkeley National Laboratory, Department of Physics, Florida State University., JINR, Tsinghua University, LBNL, LBNL/Vanderbilt University, Vanderbilt University, Florida A\&M University, Georgia Institute of Technology, Department of Physics, Virginia Tech, Gatton Academy, Exeter University, Florida International University, Office of Research, University of North Florida, Physics Department, University of North Florida, NSCL, Michigan State University, Physics Department, Florida State University, University of Tennessee-Knoxville, Neel Institut, Kazan Federal University, Bielefeld University, Ben Gurion University, LCIB - CEA, University of Georgia, Lawrence Livermore National Laboratory, Livermore, CA 94550, NHMFL, Tallahassee, USA, Department of Chemistry, University of Waterloo, Ontario, Canada, NHMFL, Tallahassee FL 32310 USA, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany, Wigner Research Center for Physics, Budapest, Hungary, Experimental physics II, University of Augsburg, Germany, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, National High Magnetic Field Laboratory Florida State University, Tallahassee, Florida 32310, IM2NP-CNRS (UMR 7334) and Universite Aix-Marseille, National High Magnetic Field Laboratory Applied Superconductivity Center, Heifei National Lab for Physical Science at Microscale, USTC, Institute of Physics, Chinese Academy of Sciences, Department of Electrical Engineering, Rice University, National High Magnetic Field Laboratory, National High Magnetic Field Laboratory/FSU, University of Virginia