New advances in photoionization codes:

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New advances in photoionization codes
How and What for?

• Barbara Ercolano, UCL

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Photoionization models How?
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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
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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
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Ercolano et al., 2003, MNRAS 340, 1136
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New advances How ?

• Atomic data updates
• Time-dependence effects
• Inclusion of dust RT
• Expansion to PDR
• Development of 3-D Codes

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New advances How ?

• Atomic data updates
• Collision strengths transition probs
• RadiativeDielectronic recombination
• Recombination data for ORLs
• (R. Bastin)
• Data for cold (0.5-2kK) ionized plasma
• (as suggested by ORL analyses)

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New advances How ?

• Atomic data updates
• Time-dependence effects
• Inclusion of dust RT
• Expansion to PDR
• Development of 3-D Codes

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Time-dependent effects

• Shock ionization (Mappings III)
• Source variation (PNe in recombination)
• Short gas-flow time scales
• Cloudy (Henney et al., 2005 ApJ, 621,328)

(Henney et al., 2005 ApJ, 621,328)
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New advances How ?

• Atomic data updates
• Time-dependence effects
• Inclusion of dust RT
• Expansion to PDR
• Development of 3-D Codes

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Gas and Dust Interactions the dust thermal
balance
Dust Cooling
Photoelectric emission from grains
Absorption of resonance emission lines
Radiation from grains
Absorption of UV photons
Dust Heating
Dust-gas collisions
Cloudy (Van Hoof et al., 2004, MNRAS 350,
1330) Mocassin (Ercolano et al., 2005, MNRAS
submitted)
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Effects of dust grains on emission lines ratios
Cloudy (Van Hoof et al., 2004, MNRAS 350, 1330)
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New advances How ?

• Atomic data updates
• Time-dependence effects
• Inclusion of dust RT
• Expansion to PDR
• Development of 3-D Codes

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Self-consistent PhotoionizationPDR
PNe emission line spectra modified by PDRs
Radiation field on PDR comes from ionised region
Dust dominates the opacity in the PDR
Must include a chemical network
Cloudy (Shaw et al., 2005, ApJ 624, 794Abel et
al., 2005, ApJ 609, 247)
MocassinUCL_PDR (Ercolano et al., in prep.)
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New advances How ?

• Atomic data updates
• Time-dependence effects
• Inclusion of dust RT
• Expansion to PDR
• Development of 3-D Codes

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3D codes What for?
NGC6543 The Cats eye Nebula
NGC2392 The Eskimo Nebula
MyCn18 The etched hourglass nebula
NGC7009 The Saturn Nebula
Central region of Abell 30
Images from www.hubblesite.org
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Projected model images of NGC 3918 in three
infrared fine-structure lines observed by the ISO
SWS
Ercolano et al., 2003, MNRAS 340, 1153
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3D photoionization codes chronology

• 1990 Baessgen et al., AA, 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

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2D Projections

• NII

• Ha

Sahai et al., 1999, AJ 118,468

• OIII

• OI

Neal et al. (in prep)
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2D Projections

• NII

• Ha

Sahai et al., 1999, AJ, 118, 468

• OIII

• OI

Neal et al. (in prep)
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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

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CAVEAT Horses for courses!!!
Never use a sledge-hammer to squash a
fly!!! (Anonymous referee)

• 1D codes allow faster computations
• Parameter space explored more efficiently
• Large grids of models can be produced quickly

• 1D codes can be used in the case of
• Spatially unresolved objects
• Diffuse field unimportant (Nebu 3D)

Moores law on the other hand.
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Overview

• Photoionization Codes What for?
• Photoionization Codes How?
• New Advances How?
• 3D codes How What for?
• Near near-ish future

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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

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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

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3D (MonteCarlo) photoionisation How?

• Discrete description of radiation field (energy
  packets)
• Simulating the individual absorption/emission/scat
  tering events
• Packets trajectories determined stochastically
  according to the local opacities and
  emissivities.
• Gas properties determined by imposing ionisation
  balance and thermal equilibrium

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Gas and Dust Interactions the dust thermal
balance
Photoelectric emission from grains
Gas Heating
Dust Cooling
Radiation from grains
Absorption of resonance emission lines
Absorption of UV photons
Dust Heating
Gas Cooling
Dust-gas collisions
Cloudy (Van Hoof et al., 2004) Mocassin
(Ercolano et al., submitted)
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MOnteCArloSimulationSofIonisedNebulae(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

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Heating and cooling contributions in knot J3 of
Abell 30
Ercolano et al., 2003 MNRAS 344, 1145
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
rd/rg(core) 0.077
rd/rg(env) 0.107