Radio Recombination Lines with the Lovell Telescope

Radio Recombination Lines (RRLs) are the radio counterpart of optical Balmer lines, which provide an accurate tracer for free-free emission without the need for substantial dust corrections required by Hα surveys. Independent models based on Hα data and Far Infrared data (which does not directly trace RRL gas but is uninhibited by dust) are used to derive the observable RRL flux from a sample of 43 galaxies expected to be strong thermal emitters. Integration times are established for the Lovell Telescope at Jodrell Bank. M33, M77 and NGC 1569 are established as promising candidate galaxies from which RRLs have not been detected. A new FPGA-based spectrometer is being developed for the Lovell Telescope, specifically for RRL measurements. This will have sub-km/s resolution over > 1GHz bandwidth, and will be expanded to include a GPU-processing element to further increase resolution and bandwidth. This system will initially be used to make new extragalactic RRL detections and add northern hemisphere RRL data to the HIPASS-derived Galactic-plane RRL survey by Alves et al. 2014.