Spitzer Mid-IR Spectroscopy of Infrared Luminous Galaxies at z > 1

Lin Yan

The superb sensitivity of Spitzer Space Telescope and its instruments have enabled us for the first time to carry out systematic studies at the mid-IR wavelength of galaxies at the significant cosmological distance. I will present the early results from the Spitzer GO programs on mid-IR spectroscopy of high-z Infrared luminous galaxies. The new discovery of a large population of IR luminous galaxies at z~2 will be presented. The detailed mid-IR spectral diagnostics for the sample of ultra-luminous galaxies at z~2 will be discussed, including source energetics and the diversity of mid-to-far IR SEDs. Finally, we will discuss the implications of our results for the galaxy and AGN evolution history.