  Resolving physical and chemical structures in the vicinity of a protostar is
of fundamental importance for elucidating their evolution to a planetary
system. In this context, we have conducted 1.2 mm observations toward the
low-mass protostellar source B335 at a resolution of 0."03 with ALMA. More than
20 molecular species including HCOOH, NH2 CHO, HNCO, CH3 OH, CH2 DOH, CHD2 OH,
and CH3 OD are detected within a few 10 au around the continuum peak. We find a
systematic chemical differentiation between oxygen-bearing and nitrogen-bearing
organic molecules by using the principal component analysis for the image cube
data. The distributions of the nitrogen-bearing molecules are more compact than
those of the oxygen-bearing ones except for HCOOH. The temperature distribution
of the disk/envelope system is revealed by a multi-line analysis for each of
HCOOH, NH2 CHO, CH3 OH, and CH2 DOH. The rotation temperatures at the radius of
0."06 along the envelope direction of CH3OH and CH2DOH are derived to be
150-165 K. On the other hand, those of HCOOH and NH2CHO, which have a smaller
distribution, are 75-112 K, and are significantly lower than those for CH3OH
and CH2DOH. This means that the outer envelope traced by CH3OH and CH2DOH is
heated by additional mechanisms rather than the protostellar heating. We here
propose the accretion shock as the heating mechanism. The chemical
differentiation and the temperature structure on a few au scale provide us with
key information to further understand chemical processes in protostellar
sources.
