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The warm and hot gas between galaxies and within their halo is a reservoir of matter from which proto-galaxies can form. MOSAIC will provide an unprecedented map of the distant 3D structures of this gas as well as evaluating for the first time the distribution of the different baryonic components of the matter. | ||
Detailed simulations show that MOSAIC will play an important role in the mapping of the intergalactic medium. An ambitious galaxy survey with MOSAIC will provide a 3D map of the IGM at z > 3, complementing similar surveys that will focus on lower redshifts. In synergy with the missions like Euclid and JWST, MOSAIC will enable us to probe the full redshift evolution of galaxy growth in the cosmic web throughout the cosmic period of intense star formation.
Several fundamental questions about the inner part of our Galaxy, the Bulge, are still without answer because this region is dense and with high extinction so that present telescopes can catch only the few brightest stars there. With MOSAIC we will be able to observe unevolved stars, the largest population in the bulge. In particular, for the first time, we will be able to observe in the Bulge stars that, as our Sun, are sill on the Main Sequence. This stellar population will reveal us the kinematic and metallicity of the Bulge, and, hosting the large majority of the stars, will allow us to better estimate the mass of our Galaxy. With a good knowledge on the complete sequence of the stellar evolution in the Bulge, we will derive also stellar ages. We will then have the possibility to draw a picture on the formation and past history of our Galaxy and to understand its actual shape. | ||

Lithium is the heaviest nucleus produced in the Big Bang Nucleosynthesis (BBN). The other sources of Li production operate on long time-scales (> than 2 Gyr) so that lithium observed in the old stars must come from the BBN. The lithium abundance measured in the stellar atmospheres is almost the same for all the old unevolved stars but it is one third of the standard BBN prediction. Is this a sign of "new physics", beyond the standard model? Has lithium been uniformly destroyed in all the stars? All the theories predicting lithium destruction fail to explain at the same time the homogeneity and such a large destruction. Is this behaviour unique to our Galaxy? Only with MOSAIC we will be able to observed for the first time, lithium in several external galaxies and answer this question. | ||

MOSAIC on ELT will carry out the first statistically significant survey of the chemo-dynamical properties of dwarf galaxies at 1 < z < 3, when the Universe was less than half its current age. The unrivalled visual acuity, sensitivity and multiplexity of the spectrograph will allow the study of spatially-resolved chemical inhomogeneities in large samples of high-z dwarfs. Their chemical maps, further complemented with detailed kinematic information of the ionised gas across the galaxy shall uncover the presence of infall-driven, turbulent star formation, as well as reveal the imprints of energetic outflows from supernovae. The dwarf irregular galaxy IC1613 Credit: NASA/JPL-Caltech/SSC | ||

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