Cosmological surveys with the Spitzer Space Telescope

NASA's Spitzer Space Telescope (formerly known as the Space Infrared Telescope Facility SIRTF) is now on normal science operation and open to the international community. One of the Guaranteed Time Observer programs consists in a series of surveys using the two imaging instruments on Spitzer: MIPS (observing at 24, 70, and 160 microns) and IRAC (3.6, 4.5, 5.6 and 8 microns). The program includes observations to various depths, from wide field shallow, to very deep confusion limited surveys. We are also conducting a series of supporting programs (including also data from the spectrograph on Spitzer, IRS) to help interpret what we see in the deep surveys, e.g., the characterization of the spectral energy distributions of about 150 QSOs, and an extensive study of low-metallicity nearby star-forming galaxies. GTC first light is scheduled when the first well-established results from our Cosmological Surveys program will be released, offering us an incomparable facility to perform spectroscopic and photometric follow-ups of mid- and far-infrared selected sources. Moreover, the combination of the GTC, Spitzer and the Large Millimeter Telescope (LMT) facilities will allow us to study the galaxy populations in the Universe with a sensitivity and a coverage of the electromagnetic spectrum that have no precedents until today.