ALMA Astrochemical Observations of the Infrared-Luminous Merger NGC 3256
  In external galaxies, molecular composition may be influenced by extreme
environments such as starbursts and galaxy mergers. To study such molecular
chemistry, we observed the luminous-infrared galaxy and merger NGC 3256 using
the Atacama Large Millimeter/sub-millimeter Array. We covered most of the 3-mm
and 1.3-mm bands for a multi-species, multi-transition analysis. We first
analyzed intensity ratio maps of selected lines such as HCN/HCO$^+$, which
shows no enhancement at an AGN. We then compared the chemical compositions
within NGC 3256 at the two nuclei, tidal arms, and positions with influence
from galactic outflows. We found the largest variation in SiO and CH$_3$OH,
species that are likely to be enhanced by shocks. Next, we compared the
chemical compositions in the nuclei of NGC 3256, NGC 253, and Arp 220; these
galactic nuclei have varying star formation efficiencies. Arp 220 shows higher
abundances of SiO and HC$_3$N than NGC 3256 and NGC 253. Abundances of most
species do not show strong correlation with the star formation efficiencies,
although the CH$_3$CCH abundance seems to have a weak positive correlation with
the star formation efficiency. Lastly, the chemistry of spiral arm positions in
NGC 3256 is compared with that of W 51, a Galactic molecular cloud complex in a
spiral arm. We found higher fractional abundances of shock tracers, and
possibly also higher dense gas fraction in NGC 3256 compared with W 51.
