Physical and Chemical Structure of Disk and Envelope of a Class 0/I protostar L1527
Lizxandra Flores-Rivera
Tuesday December 1st, 15:45
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 (less equal than 75 au) the protostar, and then (ii) computing the resulting astrochemical abundances for 292 chemical species. Our resulting model reproduce the disk and envelope kinematics based on a comparison between observed and modeled C^{18}O PV diagram. 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.