  We present first results from the SXDF-ALMA 1.5 arcmin^2 deep survey at 1.1
mm using Atacama Large Millimeter Array (ALMA). The map reaches a 1sigma depth
of 55 uJy/beam and covers 12 Halpha-selected star-forming galaxies at z = 2.19
or z=2.53. We have detected continuum emission from three of our
Halpha-selected sample, including one compact star-forming galaxy with high
stellar surface density, NB2315-07. They are all red in the rest-frame optical
and have stellar masses of log (M*/Msun)>10.9 whereas the other blue,
main-sequence galaxies with log(M*/Msun)=10.0-10.8 are exceedingly faint, <290
uJy (2sigma upper limit). We also find the 1.1 mm-brightest galaxy, NB2315-02,
to be associated with a compact (R_e=0.7+-0.1 kpc), dusty star-forming
component. Given high gas fraction (44^{+20}_{-8}% or 37^{+25}_{-3}%) and high
star formation rate surface density (126^{+27}_{-30} Msun yr^{-1}kpc^{-2}), the
concentrated starburst can within less than 50^{+12}_{-11} Myr build up a
stellar surface density matching that of massive compact galaxies at z~2,
provided at least 19+-3% of the total gas is converted into stars in the galaxy
centre. On the other hand, NB2315-07, which already has such a high stellar
surface density core, shows a gas fraction (23+-8%) and is located in the lower
envelope of the star formation main-sequence. This compact less star-forming
galaxy is likely to be in an intermediate phase between compact dusty
star-forming and quiescent galaxies.
