  (Abridged) We present the analysis of the first 18 months of data obtained
with the COSMOSOMAS experiment at the Teide Observatory (Tenerife). Three maps
have been obtained at 12.7, 14.7 and 16.3 GHz covering 9000 square degrees each
with a resolution of ~1 degree and with sensitivities 49, 59 and 115 muK per
beam respectively. These data in conjuction with the WMAP first year maps have
revealed that the Cosmic Microwave Background (CMB) is the dominant
astronomical signal at high galatic latitude in the three COSMOSOMAS channels
with an average amplitude of 29.7+/- 1.0 \muK (68% c.l. not including
calibration errors). This value is in agreement with the predicted CMB signal
in the COSMOSOMAS maps using the best fit Lambda-CDM model to the WMAP power
spectrum. Cross-correlation of COSMOSOMAS data with the DIRBE map at 100 \mu m
shows the existence of a common signal with amplitude 7.4+/- 1.1, 7.5+/- 1.1,
and 6.5+/-2.3 muK in the 12.7, 14.7 and 16.3 GHz COSMOSOMAS maps at
|b|>30^\deg. Using the WMAP data we find this DIRBE correlated signal rises
from high to low frequencies flattening below ~20 GHz. At higher galactic
latitudes the average amplitude of the correlated signal with the DIRBE maps
decreases slightly. The frequency behaviour of the COSMOSOMAS/WMAP correlated
signal with DIRBE is not compatible with the expected tendency for thermal
dust. A study of the H-alpha emission maps do not support free-free as a major
contributor to that signal. Our results provide evidence of a new galactic
foreground with properties compatible with those predicted by the spinning dust
models.
