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Abstract
We present a partial-sky survey of the radio continuum at 2.3 GHz within the scope
of the Galactic Emission Mapping (GEM) project, an observational program conceived
and developed to reveal the large-scale properties of Galactic synchrotron radiation
through a set of self-consistent surveys of the radio continuum between 408 MHz and
10 GHz. The GEM experiment uses a portable and double-shielded 5.5-m radiotelescope
in altazimuthal configuration to map 60-degree-wide declination bands from different
observational sites by circularly scanning the sky at zenithal angles of 30 deg from
a constantly rotating platform. The observations were accomplished with a total power
receiver, whose front-end High Electron Mobility Transistor (HEMT) amplifier was matched
directly to a cylindrical horn at the prime focus of the parabolic reflector. The
Moon was used to calibrate the antenna temperature scale and the preparation of the
map required direct subtraction and destriping algorithms to remove ground contamination
as the most significant source of systematic error. We used 484 hours of total intensity
observations from two locations in Colombia and Brazil to yield 66% sky coverage from
DEC = -51.73 deg to DEC = +34.78 deg. The zero-level uncertainty of the combined survey
is 103 mK with a temperature scale error of 5% after direct correlation with the Rhodes/HartRAO
survey at 2326 MHz on a T-T plot. The sky brightness distribution into regions of
low and high emission in the GEM survey is consistent with the appearance of a transition
region as seen in the Haslam 408 MHz and WMAP K-band surveys. Preliminary results
also show that the temperature spectral index between 408 MHz and the 2.3 GHz band
of the GEM survey has a weak spatial correlation with these regions; but it steepens
significantly from high to low emission regions with respect to the WMAP K-band survey.