MMA Memo #128

Sensitivity of the MMA in Wide Field Imaging

M.A. Holdaway [1], M.P. Rupen [1]

June 16, 1995

Keywords: mosaicing, sensitivity, wide field imaging

The MMA D array used in mosaicing mode will provide a very sensitive and efficient means of imaging very large fields. With integration times per pointing of only 1 s, the MMA D array can achieve surface brightness sensitivity at 115 GHz and 1.3 km/s spectral resolution of 0.19 K at the full 7.2 arcsec resolution and 0.076 K when tapered to 14.4 arcsec resolution (14.4 arcsec is similar to the resolution obtained with a 50 m single dish at 115 GHz). Observing 1 s per pointing at 230 GHz with 1.3 km/s spectral resolution, sensitivities of 0.25 K at the full 3.6 arcsec resolution and 0.10 K when tapered to 7.2 arcsec resolution can be achieved. With these interesting sensitivity levels in only 1 s per pointing, mosaics of thousands of pointings will be desirable. Utilization of this powerful capability of the MMA will require continuous scan (On-The-Fly) mosaicing, smooth synchronous tracking by all antennas to a few arcseconds pointing accuracy, and correlator dump times of 0.3 s or less.

It can be argued that large single dishes equipped with large focal plane arrays should be more capable at imaging such large regions of the sky. When compared at the same resolution, the MMA is several times faster at wide field imaging than a ``straw man'' large single dish. Much more computer time will be required to process the MMA data than the single dish data, but the MMA images are likely to be of higher quality.

[1] NRAO/NM

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Last modified: 09 December, 1999