SUB-KILOPARSEC ALMA IMAGING OF COMPACT STAR-FORMING GALAXIES AT z similar to 2.5: REVEALING THE FORMATION OF DENSE GALACTIC CORES IN THE PROGENITORS OF COMPACT QUIESCENT GALAXIES

摘要

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 mu m dust continuum maps of six massive, compact, dusty star-forming galaxies at z similar to 2.5. These galaxies are selected for their small rest-frame optical sizes (r(e,F160W) similar to 1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z similar to 2. The deep observations yield high far-infrared (FIR) luminosities of = L-IR = 10(12.3-12.8) L-circle dot and star formation rates (SFRs) of SFR = 200-700 M-circle dot yr(-1), consistent with those of typical star-forming "main sequence" galaxies. The high spatial resolution (FWHM similar to 0.'' 12-0.'' 18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+ IR) SFR. We find that the dusty, nuclear IR-SFR overwhelmingly dominates the bolometric SFR up to r similar to 5 kpc, by a factor of over 100x from the unobscured UV-SFR. Furthermore, the effective radius of the mean SFR profile (r(e,SFR) similar to 1 kpc) is similar to 30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Delta t = +/- 100 Myr, is a 4x increase of the stellar mass density within the central 1 kpc and a 1.6x decrease of the half-mass-radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.