OBSERVING THE END OF COLD FLOW ACCRETION USING HALO ABSORPTION SYSTEMS

Abstract

The radio continuum emission from the Galaxy has a rich mix of thermal and\nnon-thermal emission. This very richness makes their interpretation challenging\nsince the low radio opacity means that a radio image represents the sum of all\nemission regions along the line-of-sight. These challenges make the existing\nnarrow-band radio surveys of the Galactic plane difficult to interpret: e.g. a\nsmall region of emission might be a supernova remnant (SNR) or an HII region,\nor a complex combination of both. Instantaneous wide bandwidth radio\nobservations in combination with the capability for high resolution spectral\nindex mapping, can be directly used to disentangle these effects.\n Here we demonstrate simultaneous continuum and spectral index imaging\ncapability at the full continuum sensitivity and resolution using newly\ndeveloped wide-band wide-field imaging algorithms. Observations were done in\nthe L- and C-Band with a total bandwidth of 1 and 2 GHz respectively. We\npresent preliminary results in the form of a full-field continuum image\ncovering the wide-band sensitivity pattern of the EVLA centered on a large but\npoorly studied SNR (G55.7+3.4) and relatively narrower field continuum and\nspectral index maps of three fields containing SNR and diffused thermal\nemission. We demonstrate that spatially resolved spectral index maps\ndifferentiates regions with emission of different physical origin (spectral\nindex variation across composite SNRs and separation of thermal and non-thermal\nemission), superimposed along the line of sight. The wide-field image centered\non the SNR G55.7+3.4 also demonstrates the excellent wide-field wide-band\nimaging capability of the EVLA.\n