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b"Several lines of evidence suggest that the most active phase of galaxy\\nevolution, especially in the most massive systems, was largely \\ncompleted by $z\\\\sim 1$. This results, e.g., from the observation that\\nthe most massive galaxies at low redshift have very old stellar\\npopulations ($\\\\sim 10$ Gyr) and very little gas to fuel subsequent\\nstar formation. Similarly, active galactic nuclei (AGN) were more\\nnumerous and brighter in the early universe. Ultimately, the direct\\nobservation of high-redshift galaxies will be the only way to\\nunderstand which processes shaped the universe we see today, in \\nspite of the rich ``fossil'' data sets we have of the Milky Way and\\nneighboring galaxies. Thanks to the new $8-10$ m telescope class and\\nnovel instrumentation, including SPIFFI/SINFONI on the VLT, individual\\ngalaxies at redshifts $z\\\\sim 1-3$ ($2-6$ Gyr after the Big Bang)\\nare now within the reach of astronomical spectrographs. \\n\\n\\nMethodologically, this thesis focuses on the analysis of spectrally\\nand spatially resolved optical emission lines, first of all \\\\ha\\\\ and\\n[OIII]\\\\lam5007, which are shifted into the near-infrared. {\\\\sc Spiffi\\n/ Sinfoni}\\nis very suited to such a programme, because it records the spectra of\\na contiguous field of view of up to 8\\\\arcsec$\\\\times$8\\\\arcsec. The\\ninternal kinematic and chemical gradients within a galaxy can thus be\\nmeasured in a single observation. Galaxies in the early universe had\\nparticularly high star-formation rates, so that many targets are\\nbright optical line emitters. Internal kinematics are measured\\nthrough the Doppler effect, line profiles and widths indicate the\\npresence of an AGN, galactic ``superwinds'' and the relationship of\\nchaotic to ordered motion. Star-formation rates are measured from the\\nluminosity of the Balmer lines, especially \\\\ha. Characteristic line\\nratios indicate the presence of an AGN, chemical composition, and\\nelectron densities in the ISM, and they allow to distinguish shocks\\nand photoionization.\\n\\nThis thesis is a pilot study: It comprises 9\\ngalaxies that fulfill a variety of selection criteria: they are\\neither bright UV or submillimeter emitters, or they are radio-loud. \\nPerhaps the most fundamental result is that gravity (dominated by dark\\nmatter) is the main driver of early galaxy evolution, but it\\nis not the only important process. Star formation and AGN cause\\nhydrodynamical feedback processes, which might be a sign of\\nself-regulated galaxy evolution. It is found that star-formation\\nrelated feedback had similar properties at low and high redshift, but\\nthat AGN-driven gas expulsion might have played a major role in the\\nhigh-redshift evolution of galaxies, that is without low-redshift\\nequivalent. Another important result is the rotation curve we find in\\nthe central kiloparsec of a gravitationally lensed UV-selected\\ngalaxy. Velocity gradients of $\\\\sim 100$ \\\\kms\\\\ have been observed in\\nmany high-redshift galaxies, but the interpretation as rotation curves\\nis generally not unique. Given the relatively coarse spatial\\nresolution of high-redshift galaxy data, two nearby galaxies, maybe\\ninteracting or undergoing a merger, might blend\\tinto one smooth\\nvelocity gradient. Galaxy mergers are an important ingredient of the\\n``hierarchical model'', the current paradigm of structure formation,\\nand therefore nearby galaxy pairs were likely more common at high\\nredshift than they are today. The large similarity of the lensed\\nrotation curve with those of nearby galaxies might be a first sign\\nthat galaxies evolved inside-out."