The DESI Bright Galaxy Survey: from target selection to preliminary clustering

The Dark Energy Spectroscopic Instrument (DESI) will measure redshifts for 20 millions of high redshift (z > 0.5) galaxies and quasars under dark time conditions using a 5000-fibre spectrograph on the 4-meter Mayall Telescope in the US. However, under lunar conditions that are too bright for good observations of these faint objects, DESI will observe a complete magnitude-limited survey of lower redshift galaxies (z < 0.5 with a mediant z~0.2) called the Bright Galaxy Survey (BGS). The BGS will be 1) two magnitudes fainter than the limit of SDSS, 2) the densest galaxy sample to z~0.45 with an order of magnitude larger than SDSS-I and II and at z=0.3 ten times denser than the SDSS-III BOSS LOWZ galaxy sample. In this talk, I will present the target selection, catalogue and clustering properties of the DESI BGS targets from the final release of the Legacy Imaging Surveys. Then, I will mention examples of the science studies we plan to conduct with the BGS, from cosmological constraints to galaxy properties and their connection with the cosmic web.