Compact starbursts in z 3-6 submillimeter galaxies revealed by ALMA

الأصل · EN

We report the source size distribution, as measured by ALMA millimetric continuum imaging, of a sample of 13 AzTEC-selected submillimeter galaxies (SMGs) at zₚhoto 3-6. Their infrared luminosities and star-formation rates (SFR) are LᵢR 2-6 x 10¹2 Lₛun and 200-600 Mₛun yr-1, respectively. The size of z 3-6 SMGs ranges from 0".10 to 0".38 with a median of 0".20+0".03-0".05 (FWHM), corresponding to a median circularized effective radius (Rc,e) of 0.67+0.13-0.14 kpc, comparable to the typical size of the stellar component measured in compact quiescent galaxies at z 2 (cQGs) --- R 1 kpc. The median surface SFR density of our z 3-6 SMGs is 100+42-26 Mₛun yr-1 kpc-2, comparable to that seen in local merger-driven (U)LIRGsrather than in extended disk galaxies at low and high redshifts. The discovery of compact starbursts in z > 3 SMGs strongly supports a massive galaxy formation scenario wherein z 3-6 SMGs evolve into the compact stellar components of z 2 cQGs. These cQGs are then thought to evolve into the most massive ellipticals in the local Universe, mostly via dry mergers. Our results thus suggest that z > 3 SMGs are the likely progenitors of massive local ellipticals, via cQGs, meaning that we can now trace the evolutionary path of the most massive galaxies over a period encompassing 90% of the age of the Universe.