Description
In this work we present 74MHz observations in the region 26{deg}>l>-15{deg}, -5{deg}<b<5{deg} report the detection of 92 absorption features associated with known HII regions; and derive the brightness temperature of the Galactic cosmic-ray electron synchrotron emission emanating from the column behind these regions. For the 42 HII regions with known distances, the average emissivity of the column behind the HII region is derived. The 74MHz emissivity values range between 0.3 and 1.0K/pc for a model assuming uniform distribution of emissivity. Methods for using this type of data to model the three-dimensional distribution of cosmic-ray emissivity and the possibility of using this method to break the HII region kinematic distance degeneracy are discussed.
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