New advances in photoionization codes, how and what for?
New advances in photoionization codes:
Barbara Ercolano, UCL
How and What for?
New advances in photoionization codes, how and what for?
Ionising radiation transferThermal equilibriumIonisation balance
Electron temperature
Ionisation structure
Emission linespectrum
Ionising source
Atomic data
Chemical composition Gas density
distribution
Processes stationaryStatic medium
Spherical symmetry
Photoionization models – How?
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
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
New advances in photoionization codes, how and what for?
Ercolano et al., 2003, MNRAS 340, 1136
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
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)
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
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
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
New advances in photoionization codes, how and what for?
Gas and Dust Interactions: the dust thermal balance
Absorption of resonance
emission lines
Dust-gascollisions
Absorption of UV photons
Photoelectricemission
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
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)
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
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.)
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
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
New advances in photoionization codes, how and what for?
Projected model images of NGC 3918 in three Projected model images of NGC 3918 in three infrared fine-structure lines observed by the infrared fine-structure lines observed by the ISO ISO
SWSSWS
Ercolano et al., 2003, MNRAS 340, 1153
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
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)
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
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
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….
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
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
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
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?
New advances in photoionization codes, how and what for?
Gas and Dust Interactions: the dust thermal balance
Dust Heating
Gas Heating Dust Cooling
Gas Cooling
Absorption of resonance
emission lines
Dust-gascollisions
Absorption of UV photons
Photoelectricemission
from grains
Cloudy (Van Hoof et al., 2004); Mocassin (Ercolano et al., submitted)
Radiation from grains
New advances in photoionization codes, how and what for?
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
New advances in photoionization codes, how and what for?
Heating and cooling contributions in knot J3 of Heating and cooling contributions in knot J3 of Abell 30Abell 30
Positive x
Negative xPositive zphoto: heating by photoionization dust: heating by photoelectric emission from dust grainscoll: cooling by collisionally excited linesrec: cooling by recombinationff: cooling by free-free radiation
d/g(core)= 0.077
d/g(env)= 0.107
Ercolano et al., 2003 MNRAS 344, 1145