SPARX -- Simulation Package for Astronomical Radiative Xfer

We developed a multi-dimensional molecular line RT engine and enabling parallel computing on the cluster.

Transcript

1. SPARX - A Radiative Transfer Package Sheng-Yuan Liu, I-Ta Hsieh, Eric Chung 2nd ASIAA ICSM Workshop (2014)
2. Radiative Transfer - what and why? • How radiation propagates in medium • Intensity (Iv ) is a function of not only location and frequency but also direction, time, polarization, etc, and it is (mostly) what we observe • v and jv are functions of composition, temperature, excitation of the medium Tex physical/chemical structure Tex radiation Tex observable Tex unknown Tex R.T.
3. (types of) Radiative Transfer Calculation • embedded in • (thermal-)(chemo-)(magneto-)hydrodynamical simulations for accounting physical processes such as radiative heating and cooling, ionization, dissociation, etc. -> calculation self-consistent but computationally time consuming • post-processing of (thermal-)(chemo-)(magneto-)hydrodynamical simulation to generate “synthetic/simulated images for making predictions and/or comparison -> “SPARX” among other continuum/line radiative transfer tools
4. Implementation of Radiative Transfer Calculation • SPARX - Simulation Platform for Astrophysical Radiative X-fer • (sub/millimeter) molecular line and continuum • Input : physical/chemical structure (n, d, v, dv, Xmol ) • Output : image cube (hence channel maps and spectra) • Accelerated Monte Carlo Algorithm (Hogerheijde &Van dar Tak 2002) Iterating between :
5. Implementation of Radiative Transfer Calculation • SPARX • C-based core routines + python-based interface • 1-D spherical / 2-D polar / 3-D Cartesian coordinate systems • multi-level grid • parallelization with load balancing • MIRIAD subroutines required/integrated for imaging purpose • molecular lines, including treatments for • overlapping (hyperfine splitting) transitions • Zeeman splitting due to magnetic field • millimeter continuum, including polarized emission due to grain alignment by magnetic field s
6. Verification and Application one-dimension (1-D) spherical system Modified inside-out collapse of Shu’s singular isothermal sphere a test problem constructed in Rawlings et al. (1992)
7. Verification and Application one-dimension (1-D) spherical system Modified inside-out collapse of Shu’s singular isothermal sphere
8. Verification and Application 0 0.5 1 1.5 2 2.5 3 3.5 -1 -0.5 0 0.5 1 Brightness temperature (K) velocity (km/s) Spectrum of HCO+ J=1-0 spherical 1D spherical 3D nested Cartesian one-dimension (1-D) spherical system Modified inside-out collapse of Shu’s singular isothermal sphere
9. Verification and Application one-dimension (1-D) spherical system ALMA Cycle 2 NGC1333 4A Di Francisco et al. (2001) in collaboration with Yu-Nung Su NGC 1333 - a primary source for studying gas accretion/infall
10. Verification and Application one-dimension (1-D) spherical system -100 -50 0 50 100 -10 -5 0 5 10 Kelvin km/s beam size=0.3" 312-211 515-414 533-432 -30 -20 -10 0 10 20 30 -10 -5 0 5 10 km/s beam size=3" -15 -10 -5 0 5 10 15 -10 -5 0 5 10 km/s beam size=10" 103 106 106 106 109 109 10 100 1000 10000 10 100 1000 cm-3 K radius (AU) Density and Temperature H2 density temperature 0.1 1 10 10 100 1000 10000 km/s radius (AU) infall velocity 1x10-10 1x10-9 1x10-8 1x10-7 10 100 1000 10000 radius (AU) H2 CO Abundance ALMA Cycle 2 NGC1333 4A in collaboration with Yu-Nung Su H2CO
11. Verification and Application two-dimension (2-D) polar system Li & Shu (1996) in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid Magnetic field is there; (starless) cores are often not round
12. Verification and Application two-dimension (2-D) polar system in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid
13. Verification and Application two-dimension (2-D) polar system in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid
14. Verification and Application two-dimension (2-D) polar system Tafalla et al. (2006); Levin et al. (2001); Kirk, Ward Thompson, Crutcher (2006) in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid
15. Verification and Application two-dimension (2-D) polar system in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid 1e-15 1e-14 1e-13 1e-12 1e-11 1e-10 1e-09 1e-08 1e-07 0 0.05 0.1 0.15 0.2 0.25 0.3 relative abundance radius(pc) HCO+ abundance 1e4 years 1e5 years 1e6 years Tafalla et. al. Chemical modeling by Oscar Morata
16. Verification and Application two-dimension (2-D) polar system in collaboration with CHARMS group Magnetized (Singular Isothermal) Toroid By 2013 summer student Yun-Ting Cheng
17. Verification and Application three-dimension (3-D) Cartesian system Binary-induced spiral-like molecular envelope around mass-losing AGB stars in collaboration with Hyosun Kim Kim and Taam (2012); Kim et al. (2013)
18. Verification and Application three-dimension (3-D) Cartesian system Binary-induced spiral-like molecular envelope around mass-losing AGB stars Kim et al. (2013) in collaboration with Hyosun Kim
19. Verification and Application three-dimension (3-D) Cartesian system Binary-induced spiral-like molecular envelope around mass-losing AGB stars Kim et al. (2013) in collaboration with Hyosun Kim Discriminating orbit inclination angle through kinematic signatures face-on edge-on
20. Code Limitation and Development • Limitation • molecular collision rates required; limited set of molecules with “known” collisional rates (fundamental to all similar types of molecular line NLTE RT calculations) • Development • “friendlier” user interface • packaging and deployment of single-machine version • visualization • parameter space search • additional physical/radiative processes TeUsers and Science Application Cases Are Welcome! (Code developers are welcome, too!)