Physical and Chemical Structure of the Disk and Envelope of the Class
  0/I Protostar L1527
  Sub-millimeter spectral line and continuum emission from the protoplanetary
disks and envelopes of protostars are powerful probes of their structure,
chemistry, and dynamics. Here we present a benchmark study of our modeling
code, RadChemT, that for the first time uses a chemical model to reproduce ALMA
C$^{18}$O (2-1) and CARMA $^{12}$CO (1-0) and N$_{2}$H$^{+}$ (1-0) observations
of L1527, that allow us to distinguish the disk, the infalling envelope and
outflow of this Class 0/I protostar. RadChemT combines dynamics, radiative
transfer, gas chemistry and gas-grain reactions to generate models which can be
directly compared with observations for individual protostars. Rather than
individually fit abundances to a large number of free parameters, we aim to
best match the spectral line maps by (i) adopting a physical model based on
density structure and luminosity derived primarily from previous work that fit
SED and 2D imaging data, updating it to include a narrow jet detected in CARMA
and ALMA data near ($\leq 75$au) the protostar, and then (ii) computing the
resulting astrochemical abundances for 292 chemical species.
  Our model reproduces the C$^{18}$O and N$_{2}$H$^{+}$ line strengths within a
factor of 3.0; this is encouraging considering the pronounced abundance
variation (factor $> 10^3$) between the outflow shell and CO snowline region
near the midplane. Further, our modeling confirms suggestions regarding the
anti-correlation between N$_{2}$H$^{+}$ and the CO snowline between 400 au to
2,000 au from the central star. Our modeling tools represent a new and powerful
capability with which to exploit the richness of spectral line imaging provided
by modern submillimeter interferometers.
