The evolution and the interplay of the luminous and dark matter content of massive (compact) galaxies

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The assembly of massive galaxies is a key test for the models of galaxy formation and evolution. At high redshift, when the Universe was a fraction of its current age, we observe massive galaxies with no signatures of active star formation that are several times smaller than their similarly massive non-star-forming counterparts in the nearby universe. Some observational and theoretical studies have suggested that ultra-compact massive systems should completely disappear as the universe ages. ******Spectroscopic measurements reveal galaxy's distance and its nature. High-resolution images show how compact galaxies really are. Using both observational facets simultaneously, I discovered a population of dense non-star-forming (i.e., quiescent) galaxies at distances when the universe was more than half of its current age. This extreme, relatively close galaxy population bridges the gap between distant and local universe and provides an insight into the transitional channels between massive compact galaxies and extended stellar systems we observe in the Milky Way's neighbourhood. The abundance of compact massive systems in mature universe presents an opportunity to study properties of extreme galaxies that are not easily accessible at larger distances and earlier cosmic times. Using massive quiescent compact galaxy samples I have shown that ultra-dense galaxies preferentially reside in dense regions of galaxy clusters, and that they span a range of galaxy ages: from systems that have just stopped forming stars to the ones that have been "red and dead" for a few billion years. ******Building on these compelling results, I will employ dense spectroscopic surveys, high-resolution large-area space- and/or ground-based imaging, and strong gravitational lensing to: 1) trace the assembly of massive compact systems, 2) explore the relations between compact and extended massive galaxies, and 3) study the interplay between compact galaxy light profiles and their dark matter halo evolution. Dense spectroscopic surveys of all galaxies (above certain brightness limit) detected in high-resolution images will provide complete galaxy samples that include both typical galaxies and the most extreme, rare objects. In addition to mapping out the temporal evolution of extreme systems, these datasets will enable the search for links between the assembly of typical galaxies and the transformations we observe in the most extreme systems. The mass distribution (luminous and dark matter) of strong lensing galaxy clusters bends the light from a distant source producing multiple images, arcs and/or rings. By reconstructing the observed shapes of lensing arcs we can map the distribution of the total mass within galaxy cluster. A sample of ultra-dense galaxies in strong lensing clusters will unveil the role that the environment of massive compact galaxies plays in sculpting their dark matter and light profiles.