Phenomenological models for evolution of dusty galaxies and E/S0 galaxies , respectively , are developed to address two major questions concenring galaxy populations in deep infrared ( IR ) surveys : ( 1 ) Do normal late-type galaxies or starburst galaxies ( including galaxies with obscured AGNs ) dominate among sources in deep IR surveys ?
( 2 ) How much do E/S0 galaxies contribute to the counts in deep mid-infrared ( MIR : 3 – 20 \mu m ) surveys ?
Among three new models for evolution of dusty galaxies , it is assumed in Model S1 that starburst galaxies are the dominant population , and in Model S2 that normal galaxies dominate .
Model S3 is an intermediate model .
Comparing the model predictions with a wide range of observational data collected from the literature , we find that none of these models can be ruled out , given the uncertainties of the data .
We show that the most direct method to distinguish these models is to compare the predicted color distributions of IR galaxies with observations , which will soon be available from the SWIRE survey .
The models for E/S0 galaxies follow a simple passive evolution approach .
Among the three E/S0 models ( E1 , E2 and E3 ) investigated in this paper , Model E2 which is specified by a peak formation redshift z _ { peak } = 2 , and an e-folding formation time scale \omega = 2 Gyr , fits the data best .
This suggests a synchronization between the evolution of E/S0 galaxies and of starburst galaxies , in the sense that the peak of the formation function of E/S0s ( z _ { peak } = 2 ) is close to the peak of the evolution functions of starburst galaxies ( z _ { peak } = 1.4 ) .
We find that E/S0s contribute about 10 – 30 % of the counts in the MIR bands of < 10 \mu m , and up to 30 – 50 % of the optical/NIR counts in the bright end .
Their contributions to counts in the UV ( 2000Ã ) and in the longer wavelength IR ( \geq 12 \mu m ) bands are negligible .
Taking into account this contribution , new predictions for counts and confusion limits in the SIRTF bands are presented .