With the development of multiwavelength observations and theory, we are making rapid progress in understanding high redshift evolution of the most massive galaxies and the complex interplay of their components - stars, interstellar gas, dark matter halos and supermassive black-holes. After summarizing the general picture emerging from recent developments about the spheroid/black-hole relation and numerical simulations to explain it, AGN optical and X-Ray surveys, SCUBA/MAMBO surveys of high-z ultra-luminous infrared galaxies (ULIRGS, often called submillimeter galaxies, SMGs) and CO follow-up at IRAM-PdB, etc., I will focus on the importance of extensive studies of large samples of SMGs. Particularly numerous, up to one per arcmin², they are thought to trace the formation of massive galaxies, mostly elliptical, and large-scale structures at high redshift (z~1-4). However, the small number of such known sources, a few hundreds, still makes cosmological studies of this population difficult. Much larger surveys are necessary for statistical studies, tracing their spatial distribution along early large scale structures and identifying the most extraordinary, mm-brightest ones. The latter are particularly important either as strong lensed cases, or as the most luminous (far-infrared) galaxies in the Universe, with L_FIR > 10^13 Lo (hyper-luminous infrared galaxies, HLIRGs), without present day equivalent, which could trace the srongest density peaks with the first massive dark matter halos. Waiting for such surveys of several deg² with the new generation of mm/submm cameras, and several tens of deg² with Herschel, one should realize that such a very large sample of several tens thousand SMGs has already been detected by the wide surveys of Spitzer, in particular by SWIRE (50 deg²). However, in the absence of sensitive survey above 25 micron, the identification of such SMGs among the millions of SWIRE sources. I will discuss possible multi-wavelength strategies to identify them among SWIRE sources in order to trace the formation of the most massive elliptical galaxies, and their dark matter halos. It is clear that the most extraordinary among these sources will be major targets for follow-up molecular studies with millimeter interferometers and for detailed studies with ALMA and JWST.

Finally, I will stress the importance of millimeter studies to understand the connection between the AGN activity and black-hole growth with the major starbursts of such objects, taking as example our IRAM MAMBO+CO survey of bright high-z QSOs. It is now established that the regular SMG phase is accompanied by a modest X-AGN activity, which well explains the black-hole growth up to ~10⁷-10⁸ Mo (Oliver et al. 2005). It is important to build a sample of rarer, more extreme starbursts and AGN, large enough to well trace the short phases of the last growth of 10⁹ Mo black-holes. Spitzer wide surveys with mm/submm follow-up will be again essential for such a purpose, by taking advantage of the extreme Spitzer sensitivity to mid-IR emission of the various classes of AGN.

Page created on May 17, 2005.