Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 1S050

THOR - The HI, OH, Recombination Line Survey of the Milky Way

Bihr, Simon (Max Planck Institute for Astronomy Heidelberg)
Beuther, Henrik (Max Planck Institute for Astronomy Heidelberg)
Johnston, Katharine (Max Planck Institute for Astronomy Heidelberg)
Ott, Juergen (NRAO Socorro)
Glover, Simon (Institute for Theoretical Astrophysics Heidelberg)
Carlhoff, Philipp (University of Cologne)
Brunthaler, Andreas (Max Planck Institute for Radioastronomy Bonn)
Goldsmith, Paul (Jet Propulsion Laboratory)
Schilke, Peter (University of Cologne)
Motte, Frederique (Laboratoire AIM, CEA/IRFU - CNRS/INSU - University of Paris)
Henning, Thomas (Max Planck Institute for Astronomy Heidelberg)

How do molecular clouds form from the diffuse atomic interstellar medium? To address this and further questions we are conducting the THOR survey, a galactic plane survey (l = 15 to 50dec and b = -1 to +1dec) of the 21cm HI line, four OH lines, and 20 recombination lines as well as the continuum from 1 to 2 GHz at a spatial resolution of ~20arcsec. We got granted 110 hours at the VLA in C-configuration. To test the configuration, we did a pilot study around the active star forming region W43 in 2012. The data analysis is work in progress and we combined our data with the VGPS survey (VLA Galactic plane survey - HI in D-configuration). This allows us to reconstruct all spatial scales down to 0.2-0.5pc. We will compare our data with CO data to study the cloud formation from the atomic to the molecular phase. We find significantly higher HI column densities for W43 than for other regions such as Perseus. The reason for these high column densities is debatable, but we speculate, that the strong interstellar radiation field of W43 prevents the formation of molecular hydrogen.

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