1. New advances in photoionization codes, how and what for? New advances in photoionization codes: Barbara Ercolano, UCL How and What for?

2. New advances in photoionization codes, how and what for? Emission line spectrum Ionising source Atomic data Chemical composition Gas density distribution Processes stationary Static medium Spherical symmetry Photoionization models – How?

3. New advances in photoionization codes, how and what for? Lexington 2000 codes (Pequignot et al. 2001, PASP 247, 533) Cloudy (G. Ferland) Harrington (P. Harrington) Ion (H. Netzer) Mappings (R. Sutherland) (Infant) Mocassin (B. Ercolano) Nebu (D. Pequignot) Nebula (R. Rubin) XStar (T. Kallman) Ercolano et al., 2003, MNRAS 340, 1136

4. New advances in photoionization codes, how and what for? Lexington 2000 codes (Pequignot et al. 2001, PASP 247, 533) Cloudy (G. Ferland) Harrington (P. Harrington) Ion (H. Netzer) Mappings (R. Sutherland) (Infant) Mocassin (B. Ercolano) Nebu (D. Pequignot) Nebula (R. Rubin) XStar (T. Kallman) Ercolano et al., 2003, MNRAS 340, 1136

5. New advances in photoionization codes, how and what for? Ercolano et al., 2003, MNRAS 340, 1136

6. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates Time-dependence effects Inclusion of dust RT Expansion to PDR Development of 3-D Codes

7. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates –Collision strengths & transition probs –Radiative+Dielectronic recombination –Recombination data for ORLs (R. Bastin) –Data for cold (0.5-2kK) ionized plasma (as suggested by ORL analyses)

8. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates Time-dependence effects Inclusion of dust RT Expansion to PDR Development of 3-D Codes

9. New advances in photoionization codes, how and what for? (Henney et al., 2005 ApJ, 621,328) Shock ionization (Mappings III) Source variation (PNe in recombination) Short gas-flow time scales –Cloudy (Henney et al., 2005 ApJ, 621,328) Time-dependent effects

10. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates Time-dependence effects Inclusion of dust RT Expansion to PDR Development of 3-D Codes

11. New advances in photoionization codes, how and what for? Gas and Dust Interactions: the dust thermal balance Absorption of resonance emission lines Dust-gas collisions Absorption of UV photons Photoelectric emission from grains Cloudy (Van Hoof et al., 2004, MNRAS 350, 1330) Mocassin (Ercolano et al., 2005, MNRAS submitted) Radiation from grains Dust Heating Dust Cooling

12. New advances in photoionization codes, how and what for? Effects of dust grains on emission lines ratios Cloudy (Van Hoof et al., 2004, MNRAS 350, 1330)

13. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates Time-dependence effects Inclusion of dust RT Expansion to PDR Development of 3-D Codes

14. New advances in photoionization codes, how and what for? Self-consistent Photoionization+PDR Radiation field on PDR comes from ionised region Dust dominates the opacity in the PDR Must include a chemical network PNe emission line spectra modified by PDRs Cloudy (Shaw et al., 2005, ApJ 624, 794;Abel et al., 2005, ApJ 609, 247) Mocassin+UCL_PDR (Ercolano et al., in prep.)

15. New advances in photoionization codes, how and what for? New advances – How ? Atomic data updates Time-dependence effects Inclusion of dust RT Expansion to PDR Development of 3-D Codes

16. New advances in photoionization codes, how and what for? 3D codes: What for? NGC6543 – The Cat’s eye Nebula NGC2392 – The Eskimo Nebula MyCn18 – The etched hourglass nebula Images from www.hubblesite.org NGC7009 – The Saturn Nebula Central region of Abell 30

17. New advances in photoionization codes, how and what for? Projected model images of NGC 3918 in three infrared fine- structure lines observed by the ISO SWS Ercolano et al., 2003, MNRAS 340, 1153

18. New advances in photoionization codes, how and what for? 3D photoionization codes chronology 1990 Baessgen et al., A&A, 201, 237 –Fixed grid resolution, 6 most abundant elements included, OTS diffuse field 1997 São Paolo, Gruenwald et al., ApJ, 480, 283 – More flexible grid, 12 elements included, iterative techniques for the diffuse field 2003 MOCASSIN, Ercolano et al., MNRAS, 340, 1136 –Flexible grids, 30 elements included, Monte Carlo RT, diffuse field treated self-consistently 2004 Wood, Mathis & Ercolano, MNRAS 348, 1337 –Monte Carlo RT - tailored for the study of Galactic HII regions (2004 Nebu-3D, Morisset et al., MNRAS, 360, 499 ) –A quick pseudo-3D photoionization code

19. New advances in photoionization codes, how and what for? 2D Projections [NII] [OIII] [OI] Sahai et al., 1999, AJ 118,468 H  Neal et al. (in prep)

20. New advances in photoionization codes, how and what for? 2D Projections [NII] [OIII] [OI] H  Neal et al. (in prep) Sahai et al., 1999, AJ, 118, 468

21. New advances in photoionization codes, how and what for? The future for 3D photoionization Study of diffuse field dominated regions – the Helix knots and tails? Chemical inhomogeneities – ORL/CEL discrepancy? (Y. Tsamis) Realistic models of spatially resolved objects Interface with hydro-codes

22. New advances in photoionization codes, how and what for? CAVEAT: Horses for courses!!! 1D codes allow faster computations –Parameter space explored more efficiently –Large grids of models can be produced quickly “Never use a sledge-hammer to squash a fly!!!“ (Anonymous referee) 1D codes can be used in the case of –Spatially unresolved objects –Diffuse field unimportant (Nebu 3D) … Moores law on the other hand….

23. New advances in photoionization codes, how and what for? Overview Photoionization Codes: What for? Photoionization Codes: How? New Advances: How? 3D codes: How & What for? Near & near-ish future

24. New advances in photoionization codes, how and what for? Photoionization models – What for? Interpretation of spectroscopic observations to determine –Properties of ionizing star(s) –Gas density and elemental abundances –Electron temperature and ionization structure Testing physical assumptions, atomic physics and astrophysical knowledge –e.g. charge exchange process, low temperature dielectronic recombination

25. New advances in photoionization codes, how and what for? 3D (analytical) photoionization: How? São Paolo code: –Descendent of 1D Aangaba (Gruenwald & Viegas, 1992), descendant of ‘early NEBU’ (Pèquignot et al, 1988) –Stellar and diffuse fields accounted for Local radiation field is calculated taking into account attenuation from intervening cells – Several PNe modelled (Monteiro et al., 2000,2004,2005) Distance determinations

26. New advances in photoionization codes, how and what for? Discrete description of radiation field (energy packets) Simulating the individual absorption/emission/scattering events Packets trajectories determined stochastically according to the local opacities and emissivities. Gas properties determined by imposing ionisation balance and thermal equilibrium 3D (MonteCarlo) photoionisation: How?

27. New advances in photoionization codes, how and what for? Gas and Dust Interactions: the dust thermal balance Dust Heating Gas HeatingDust Cooling Gas Cooling Absorption of resonance emission lines Dust-gas collisions Absorption of UV photons Photoelectric emission from grains Cloudy (Van Hoof et al., 2004) ; Mocassin (Ercolano et al., submitted) Radiation from grains

28. New advances in photoionization codes, how and what for? MO nte CA rlo S imulation S of I onised N ebulae (Version 2.01.16) … can treat … Bipolar, irregular geometries etc.. Density &/or chemical inhomogeneities Multiple ionising sources 3D gas &/or dust radiative transfer … can provide … Emission line intensity tables Spectral energy distributions (SEDs) 3D (gas &/or dust) temperature distributions 3D ionization structures Emission line(s), continuum band projections through any line of sight

29. New advances in photoionization codes, how and what for? Heating and cooling contributions in knot J3 of Abell 30 Positive x Negative x Positive z photo: heating by photoionization dust: heating by photoelectric emission from dust grains coll: cooling by collisionally excited lines rec: cooling by recombination ff: cooling by free-free radiation  d /  g (core)= 0.077  d /  g (env)= 0.107 Ercolano et al., 2003 MNRAS 344, 1145