The Deepest View of the Molecular Gas in a Star-forming Galaxy at Cosmic Noon (z ~ 2)

About 10 Gyr ago (z~2), typical or "main-sequence" star-forming galaxies were rich in molecular gas, feeding their star formation activity to all-time highs. I will present in the poster the latest results about the molecular gas properties of BX610, a normal, massive star-forming galaxy at z~2, for which we have obtained the most detailed map of the molecular gas based on very deep ALMA observations (~20 hr) of the CO(4-3) and [CI](1-0) transitions, and the dust continuum. This observation corresponds to the deepest integration on a single high-z source by ALMA so far, allowing us to study with a unique resolution the environmental properties of different regions of the galaxy. We also combine these observations with deep VLT/SINFONI Hα observations to obtain the complete picture of the molecular gas and star-formation properties. We observe that the excitation of the molecular gas decreases with galactocentric radius; while line ratios in the outskirts are consistent with those for MS galaxies at z~1, values in the central regions of BX610 are similar to those found in local starbursts. When comparing the star formation rates (SFR) derived from extinction-corrected Hα line emission and the 630 um ALMA dust continuum, we find that Hα is highly extinguished in the central region. Combining the SFR tracers, molecular gas, and stellar mass, we find that the molecular gas depletion time decreases in the central region, and the molecular gas fraction is high \((\sim 80\%)\) and remains almost constant with radius. Together, the ALMA and VLT observations presented here offer an unprecedented view of star formation activity and the molecular gas properties of a high redshift galaxy.