A three-dimensional Monte Carlo photoionization code for modelling diffuse ionized gas

We have developed a three-dimensional Monte Carlo photoionization code tailored for the study of Galactic H II regions and the percolation of ionizing photons in diffuse ionized gas. We describe the code, our calculation of photoionization, heating and cooling, and the approximations we have employed for the low-density H II regions we wish to study. Our code gives results in agreement with the Lexington H II region benchmarks. We show an example of a two-dimensional shadowed region and point out the very significant effect that diffuse radiation produced by recombinations of He has on the temperature within the shadow.

[1]  C. Walker,et al.  The edges of molecular clouds: Fractal boundaries and density structure , 1991 .

[2]  A. Dalgarno,et al.  TWO-PHOTON DECAY OF THE SINGLET AND TRIPLET METASTABLE STATES OF HELIUM- LIKE IONS. , 1969 .

[3]  William H. Press,et al.  Numerical Recipes in C, 2nd Edition , 1992 .

[4]  R. Benjamin,et al.  Improving Predictions for Helium Emission Lines , 1998, astro-ph/9810087.

[5]  Haffner,et al.  Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies. , 1999, The Astrophysical journal.

[6]  L. Lucy.  Monte Carlo transition probabilities , 2001 .

[7]  G. Ferland,et al.  CLOUDY 90: Numerical Simulation of Plasmas and Their Spectra , 1998 .

[8]  MOCASSIN: a fully three-dimensional Monte Carlo photoionization code , 2002, astro-ph/0209378.

[9]  Kenneth R. Sembach,et al.  INTERSTELLAR ABUNDANCES FROM ABSORPTION-LINE OBSERVATIONS WITH THE HUBBLE SPACE TELESCOPE , 1996 .

[10]  Frank J. Kerr,et al.  Atlas of Galactic Neutral Hydrogen , 1997 .

[11]  R. McCray,et al.  X-ray nebular models , 1982 .

[12]  M. Livio,et al.  The Analysis of Emission Lines: Frontmatter , 1995 .

[13]  Lyman Spitzer,et al.  Physical processes in the interstellar medium , 1998 .

[14]  D. A. Verner,et al.  Atomic data for astrophysics. II. New analytic fits for photoionization cross sections of atoms and ions , 1996 .

[15]  W. Reach,et al.  Radio Recombination Lines from Inner Galaxy Diffuse Gas. I. High-Sensitivity Observations: He +/H + and Carbon , 1996 .

[16]  Anil K. Pradhan,et al.  The Analysis of Emission Lines: Atomic Data for the Analysis of Emission Lines , 1995 .

[17]  CAN REFLECTION FROM GRAINS DIAGNOSE THE ALBEDO , 2002, astro-ph/0204044.

[18]  D. G. Hummer.  Total Recombination and Energy Loss Coefficients for Hydrogenic Ions at Low Density for 10 , 1994 .

[19]  K. Wood,et al.  Escape of Ionizing Radiation from High-Redshift Galaxies , 1999, astro-ph/9911316.

[20]  B. Ciardi,et al.  Lyman continuum escape from an inhomogeneous interstellar medium , 2001, astro-ph/0111532.

[21]  G. Ferland,et al.  THE [NE III]-[O II] SPECTRUM AS AN IONIZATION INDICATOR IN NEBULAE , 1991 .

[22]  The Lexington Benchmarks for Numerical Simulations of Nebulae , 2016, 1603.08902.

[23]  A NEW GENERATION OF PHOTOIONIZATION CODES: THREE-DIMENSIONAL MODELS. THE BIPOLAR PLANETARY NEBULA IC 4406 , 1997 .

[24]  D. G. Hummer,et al.  Recombination of helium-like ions – I. Photoionization cross-sections and total recombination and cooling coefficients for atomic helium , 1998 .

[25]  Gary J. Ferland,et al.  Rate coefficients for charge transfer between hydrogen and the first 30 elements , 1996 .

[26]  J. Mathis,et al.  The Warm Ionized Medium in the Milky Way and Other Galaxies , 2000, astro-ph/0010191.

[27]  T. Arny,et al.  The Ionization Structure of Planetary Nebulae — IX LUMINOUS FILAMENTS , 1972 .

[28]  L. Binette,et al.  Galaxies: The Third Dimension , 2002 .

[29]  David M. Meyer,et al.  Evidence of Interstellar Na I Structure at Scales Down to 15 AU in Low-Density Gas , 2000 .

[30]  D. A. Verner,et al.  Atomic data for astrophysics. I. Radiative recombination rates for H-like, He-like, Li-like, and Na-like ions over a broad range of temperature , 1996 .

[31]  D. Cox,et al.  The diffuse ionized interstellar medium : structures resulting from ionization by O stars , 1993 .

[32]  K. Wood,et al.  Radiative Equilibrium and Temperature Correction in Monte Carlo Radiation Transfer , 2001, astro-ph/0103249.

[33]  John H. Black,et al.  The physical state of primordial intergalactic clouds , 1981 .

[34]  D. Osterbrock,et al.  Astrophysics of Gaseous Nebulae and Active Galactic Nuclei , 1989 .

[35]  M. Seaton.  Radiative Recombination of Hydrogenic Ions , 1959 .

[36]  William H. Press,et al.  Numerical recipes in C , 2002 .

[37]  G. Ferland,et al.  Spectroscopic Challenges of Photoionized Plasmas , 2001 .

[38]  J. Mathis.  The Spectrum of Portions of Diffuse Nebulae Shadowed from the Central Star , 1976 .

[39]  W. Mathews,et al.  THEORETICAL CONTINUOUS SPECTRA OF GASEOUS NEBULAE. , 1970 .

[40]  B. Elmegreen.  Intercloud Structure in a Turbulent Fractal Interstellar Medium , 1997 .

[41]  D. G. Hummer,et al.  Recombination line intensities for hydrogenic ions-IV. Total recombination coefficients and machine-readable tables for Z=1 to 8 , 1995 .

[42]  Anthony Howard Minter,et al.  Observation of Turbulent Fluctuations in the Interstellar Plasma Density and Magnetic Field on Spatial Scales of 0.01 to 100 Parsecs , 1996 .

[43]  B. Ciardi,et al.  Cosmological reionization around the first stars: Monte Carlo radiative transfer , 2000, astro-ph/0005181.

[44]  S. Lazarian.  Velocity and density spectra of the small magellanic cloud , 2001, astro-ph/0102191.

[45]  A. F. Casa,et al.  The Escape of Ionizing Photons from OB Associations in Disk Galaxies: Radiation Transfer through Superbubbles , 1999, astro-ph/9903331.

[46]  M. Brocklehurst.  The Line Spectra of Helium in Gaseous Nebulae , 1972 .

[47]  D. Weinberg,et al.  Cosmological Simulations with TreeSPH , 1995, astro-ph/9509107.

[48]  J. Shull,et al.  Photoionization of disk galaxies: An explanation of the sharp edges in the H I distribution , 1994 .

[49]  T. M. Bania,et al.  The Structure of Four Molecular Cloud Complexes in the BU-FCRAO Milky Way Galactic Ring Survey , 2001 .

[50]  P. Shapiro,et al.  Shadows behind Neutral Clumps in Photoionized Regions , 1998 .

[51]  R. J. Reynolds,et al.  A Comparison of Diffuse Ionized and Neutral Hydrogen Away from the Galactic Plane: H alpha -emitting H i Clouds , 1995 .

[52]  John W. Armstrong,et al.  Electron Density Power Spectrum in the Local Interstellar Medium , 1995 .