Abstract

Cosmological surveys in the next decade will contain multiwavelength information of billions of galaxies. The challenge ahead is to target a larger number of galaxies, over bigger volumes, and at redshifts above 1. This is key to distinguishing different cosmological scenarios and/or gravity models and track accurately the build-up and formation history of galaxies with unprecedented detail. In this scenario, the role of galaxy formation is enhanced by the varied selection criteria of future surveys. Most future ground surveys, such as DESI, 4MOST, PFS and J-PAS, and space missions like Euclid and WFIRST are designed to target the so-called emission-line galaxies (ELGs). ELGs are abundant at high redshifts, and their distances can be precisely measured by identifying narrow strong emission lines in their spectra. ELGs, particularly at high redshift, are only recently been explored in detail thanks to the capabilities of modern optical and NIR multi-object spectrographs and Integral-Field Units such as MOSFIRE, KMOS, WEAVE, MOONS, MUSE and HETDEX. All these instruments are revealing the nature of star-forming ELGs with exquisite and unprecedented detail. At the same time, narrow-band multi-filter photometric surveys of ELGs such as HSC, PAU and J-PLUS are probing the statistical properties of this galaxy population over large volumes. The optimal exploitation of large surveys requires a significant improvement of the understanding of ELGs. This is the problem we address here. Coming surveys will observe millions of star-forming galaxies, providing an opportunity to establish their physical properties in a diverse range of cosmological environments. The distribution of ELGs on the underlying dark matter is not well determined yet and thus, there is a need to characterise these galaxies as tracers of dark matter. The main goal of this workshop is thus to bring together and foster collaborations between people working in i) Current and future cosmological surveys targeting ELGs; ii) Galaxy formation models and mock catalogues of ELGs, and iii) Detailed studies of ELGs in the optical + NIR at high redshift. As a result of this meeting, we expect an overall picture of ELGs in a cosmological context to emerge, including the identification of key questions to address in the immediate future to guarantee the optimal exploitation of datasets in the so-called golden age of galaxy surveys.