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news:constraining_the_cold_neutral_medium_with_lofar [2015/02/23 14:33] (current)
salome created
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 +**Raymond van Oonk**, Astron & Leiden astrophysics department.
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 +**Constraining the Cold Neutral medium with LOFAR**
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 +4pm, HG00.071
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 +The interstellar medium (ISM) is the repository of stellar ejecta and the birthsite of new stars and, hence, a key factor in the evolution of galaxies. Cold, diffuse, atomic clouds are an important component of the ISM, but so far this phase has been difficult to study, because its main tracer, the HI 21 cm line, does not constrain the basic physical information of the gas (e.g., temperature,​ density) well. LOFAR has opened up the opportunity to study this component of the ISM through low-frequency carbon radio recombination lines (CRRL). These CRRLs provide a sensitive probe of the physical conditions in cold, diffuse clouds. The superb sensitivity,​ large field of view, high frequency resolution and wide coverage of LOFAR allows for efficient surveys of the sky, that will revolutionize the field of low-frequency recombination line studies. By observing these lines we will be able to determine the thermal balance, chemical enrichment and ionization rate of the cold, atomic medium from degree-scales down to scales corresponding to individual clouds and filaments in our Galaxy. Furthermore,​ being sensitive only to the cold, atomic gas, observations of low-frequency CRRLs will aid in disentangling the warm and cold constituents of the HI 21 cm emission.