A Synchrotron Survey of SLUGS Galaxies with the Arecibo Observatory 305-m Telescope.

1. A Synchrotron Survey of SLUGS Galaxies with the Arecibo Observatory 305-m Telescope. R. F. Minchin1, S. Falony2, M. Baes2 1Arecibo Observatory 2Ghent University The Arecibo Observatory 305-m telescope has been used to observe a selection of galaxies from the Scuba Local Universe Galaxy Survey at 3, 5, 7 and 9 GHz. These observations, together with literature data from the NVSS at 1.4 GHz, are being used to characterize the synchrotron emission from these galaxies and to determine the contribution of the radio continuum emission to their 850 μm fluxes. If this is large, then it will affect the determination made of the cold dust masses of these galaxies, which form the main low-redshift comparison sample for high redshift sub-mm studies. We present here an initial analysis of the first set of galaxies surveyed. If I’m not here, then try at the Arecibo Observatory stand. rminchin@naic.edu For three quarters of the 36 galaxies in the sample that have been observed so far, the synchrotron contribution is negligible (less than 1 per cent). However, this leaves a quarter for which the contribution may be significant, around half of which (4/9) have a synchrotron contribution at 850 μm of more than 5 per cent. Observational Technique The observations were one of the commissioning experiments for the dual-board mode of the WAPP correlators. This mode allows 800 MHz of simultaneous bandwidth to be observed, giving a ~40% increase in continuum sensitivity over the previous 400-MHz mode. To determine the continuum flux, the telescope was driven across the source in both azimuth and elevation. The cuts were then analysed by fitting a Gaussian to each to determine both the measured peak flux and the telescope pointing offset. The fluxes were then corrected for pointing errors using 2D Gaussian models of the beam shape. Future Work The 36 galaxies here represent around 60% of the sample. The continuation of this project has been graded ‘A’ by the Arecibo Time Advisory Panel. This will allow us to finish the observations of these galaxies - observing each galaxy in all four bands - and to observe the rest of the SLUGS galaxies that are accessible to Arecibo. The percentage contribution to each of the 36 galaxies observed so far. The contribution has been calculated by a least-squares power-law fit to the flux observed at Arecibo and (for 1.4 GHz data) from the NVSS. Each source was observed in at least two Arecibo bands (2.6 GHz S-Low, 4.85 GHz C-Band, 7.1 GHz C-High, and 8.9 GHz X-Band), including at least one of the higher-frequency bands (C-High or X-Band). All galaxies will eventually be observed at all four Arecibo bands, allowing more complex fits to be made and the percentage contribution to the 850 μm flux to be more accurately calculated.