Dust Attenuation, Bulge Formation, and Inside-out Quenching of Star Formation in Star-forming Main Sequence Galaxies at z ̃ 2

We derive 2D dust attenuation maps at ̃1 kpc resolution from the UV continuum for 10 galaxies on the z ̃ 2 star-forming main sequence (SFMS). Comparison with IR data shows that 9 out of 10 galaxies do not require further obscuration in addition to the UV-based correction, though our sample does not include the most heavily obscured, massive galaxies. The individual rest-frame V-band dust attenuation (A V) radial profiles scatter around an average profile that gently decreases from ̃1.8 mag in the center down to ̃0.6 mag at ̃3-4 half-mass radii. We use these maps to correct UV- and Hα-based star formation rates (SFRs), which agree with each other. At masses ≲ {10}11 {M}☉ , the dust-corrected specific SFR (sSFR) profiles are on average radially constant at a mass-doubling timescale of ̃300 Myr, pointing at a synchronous growth of bulge and disk components. At masses ≳ {10}11 {M}☉ , the sSFR profiles are typically centrally suppressed by a factor of ̃10 relative to the galaxy outskirts. With total central obscuration disfavored, this indicates that at least a fraction of massive z ̃ 2 SFMS galaxies have started their inside-out star formation quenching that will move them to the quenched sequence. In combination with other observations, galaxies above and below the ridge of the SFMS relation have, respectively, centrally enhanced and centrally suppressed sSFRs relative to their outskirts, supporting a picture where bulges are built owing to gas “compaction” that leads to a high central SFR as galaxies move toward the upper envelope of the SFMS. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated under NASA contract NAS 5-26555 (programs GO9822, GO10092, GO10924, GO11694, GO12578, GO12060, GO12061, GO12062, GO12063, GO12064, GO12440, GO12442, GO12443, GO12444, GO12445, GO13669), and at the Very Large Telescope of the European Southern Observatory, Paranal, Chile (ESO Programme IDs 075.A-0466, 076.A-0527, 079.A-0341, 080.A-0330, 080.A-0339, 080.A-0635, 081.A-0672, 183.A-0781, 087.A-0081, 088.A-0202, 088.A-0209, 091.A-0126)