The co transition from diffuse molecular gas to dense clouds

Rice, Johnathan S.

Permalink

https://hdl.handle.net/2142/96886 Copy

Description

Title

The co transition from diffuse molecular gas to dense clouds

Author(s)

Rice, Johnathan S.

Contributor(s)

Federman, Steven

Issue Date

2017-06-20

Keyword(s)

Atacama Large Millimeter/submillimeter Array (ALMA)'s molecular view

Abstract

The atomic to molecular transitions occurring in diffuse interstellar gas surrounding molecular clouds are affected by the local physical conditions (density and temperature) and the radiation field penetrating the material. Our optical observations of CH, CH$^{+}$, and CN absorption from McDonald Observatory and the European Southern Observatory are useful tracers of this gas and provide the velocity structure needed for analyzing lower resolution ultraviolet observations of CO and H$_{2}$ absorption from Far Ultraviolet Spectroscopic Explorer. We explore the changing environment between diffuse and dense gas by using the column densities and excitation temperatures from CO and H$_{2}$ to determine the gas density. The resulting gas densities from this method are compared to densities inferred from other methods such as C$_{2}$ and CN chemistry. The densities allow us to interpret the trends from the combined set of tracers. Groupings of sight lines, such as those toward h and $chi$ Persei or Chameleon provide a chance for further characterization of the environment. The Chameleon region in particular helps illuminate CO-dark gas, which is not associated with emission from H~small{I} at 21 cm or from CO at 2.6 mm. Expanding this analysis to include emission data from the GOT C+ survey allows the further characterization of neutral diffuse gas, including CO-dark gas.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Permalink

http://hdl.handle.net/2142/96886

DOI

https://doi.org/10.15278/isms.2017.TF03

Copyright and License Information

Copyright 2017 Johnathan S. Rice

Owning Collections