Molecular Distributions of the Disk/Envelope System of L483: Principal
  Component Analysis for the Image Cube Data
  Unbiased understandings of molecular distributions in a disk/envelope system
of a low-mass protostellar source are crucial for investigating physical and
chemical evolution processes. We have observed 23 molecular lines toward the
Class 0 protostellar source L483 with ALMA and have performed principal
component analysis (PCA) for their cube data (PCA-3D) to characterize their
distributions and velocity structures in the vicinity of the protostar. The sum
of the contributions of the first three components is 63.1 %. Most
oxygen-bearing complex-organic-molecule lines have a large correlation with the
first principal component (PC1), representing the overall structure of the
disk/envelope system around the protostar. Contrary, the C18O and SiO emissions
show small and negative correlations with PC1. The NH2CHO lines stand out
conspicuously at the second principal component (PC2), revealing more compact
distribution. The HNCO lines and the high excitation line of CH3OH have a
similar trend for PC2 to NH2CHO. On the other hand, C18O is well correlated
with the third principal component (PC3). Thus, PCA-3D enables us to elucidate
the similarities and the differences of the distributions and the velocity
structures among molecular lines simultaneously, so that the chemical
differentiation between the oxygen-bearing complex organic molecules and the
nitrogen-bearing ones is revealed in this source. We have also conducted PCA
for the moment 0 maps (PCA-2D) and that for the spectral line profiles
(PCA-1D). While they can extract part of characteristics of the molecular-line
data, PCA-3D is essential for comprehensive understandings. Characteristic
features of the molecular-line distributions are discussed on NH2CHO.
