Paper presented by Susmita Chakravorty at the 17th International Conference on Atomic Processes in Plasmas, Queen's University Belfast, 19-22 July 2011.

1. Dielectronic recombination
and stability of warm gas in AGN
Susmita Chakravorty
Harvard University, Harvard-Smithsonian CfA
Ajit Kembhavi
Martin Elvis
Gary Ferland
N. R. Badnell
2008 MNRAS, 384L, 24
The 17th International Conference on
Atomic Processes in Plasmas
Queen’s University, Belfast
22nd July 2011

3. What is an Active Galactic Nuclei : Its properties
 Small Angular size
Sun’s Diameter ~ 1.392 X 106 km
AGN ~ Size of a star
 Highly luminous (≥galactic)
Milky Way ~ 1044 ergs/sec
AGN ~ 1042 – 1048 ergs/sec

5. What is an Active Galactic Nuclei : Its properties
Broad Band Continuum

6. Broad Band Continuum
Radio far-IR optical EUV X-ray

7. Broad Band Continuum

8. in Radio
Emission lines
in Optical
Edge on
Radio Galaxy
Infrared Type II Seyfert Galaxy
Type II Quasar
UV and X-rays
Gamma Rays Type I Seyfert Galaxy
(Inverse Compton) Type I Quasar
BL Lac Object

9. in Radio
Emission lines
in Optical
Edge on
Radio Galaxy
Infrared Type II Seyfert Galaxy
Type II Quasar
UV and X-rays
Gamma Rays Type I Seyfert Galaxy
(Inverse Compton) Type I Quasar
BL Lac Object

10. in Radio
Emission lines
in Optical
Edge on
Radio Galaxy
Infrared Type II Seyfert Galaxy
Type II Quasar
UV and X-rays
Gamma Rays Type I Seyfert Galaxy
(Inverse Compton) Type I Quasar
BL Lac Object

11. 100 pc
0.1 pc
Type II Seyfert Galaxy
Type I Seyfert Galaxy Type II Quasar
Type I Quasar

12. 100 pc
0.1 pc
Type II Seyfert Galaxy
Type I Seyfert Galaxy Type II Quasar
Type I Quasar

13. Broad Band Continuum
Radio far-IR optical EUV X-ray

14. Signatures of warm absorber
 Absorption Edges in Soft X-ray Spectra
CV CVI OVII OVIII FeXVII NeX
392 490 740 870 1260 1360 (eV)
C (V & VI) O (V - VIII) Fe (XVII - XXII)
Ne (IX & X) Mg (XI & XII) Si (XIII - XVI)
 (eV)

15. Properties of the warm absorber
• Partially ionized gas in our line of sight to AGN
• Absorption features are blue shifted relative to optical
emission lines, indicating outflow
• Column Density (NH) ~ 1022±1 cm-2
• Ionization Parameter  ~ 10 – 1000 erg cm s-1
• Temperature ~ 105 K – 106.5 K = L/nR2
• Density (nH) ~ 109 cm-3 (105 - 1012) /T ~ (prad)ion/p
• Distance from the source ~ 0.01 – 100 pc

16. Why do we care?
• Mass loss rate is a substantial fraction of the accretion rate, or
exceeds it.
• The X-ray warm absorber could coexists with a UV absorber.
• Distance from the source ~ 0.01 – 100 pc
We need to understand warm absorber nature
• Is the Warm Absorber in thermodynamic equilibrium?
• If so, does the gas have multiphase nature?

17. Stability Curve

18. Stability Curve
= L/nR2
/T ~ (prad)ion/p
T
Curve – phase diagram
P

19. CLOUDY
http://www.nublado/org/
Inputs
Radiation Field
Geometry
Neutral Composition
Density
Thickness

20. CLOUDY
http://www.nublado/org/
Inputs Process
Basic Assumption
Radiation Field Atomic processes reached
time-steady state
Geometry n(X i )(X i )  n(X i  1 )neG (X i 1, T)
Neutral Composition Thermal balance achieved
 Coll   IC  (Ph  C ) / n
Density
Working principle
Thickness ni  
  njRji  Source  ni   Rij  Sink   0
 ji 
t ji  

21. CLOUDY
http://www.nublado/org/
Inputs
Radiation Field
Geometry Teq
Neutral Composition
Density
Thickness
Output  Thermal state & Ionic composition of cloud

22. Stability Curve
Each point in the curve have thermal
and ionic composition information
Stable
= L/nR2
/T ~ (prad)ion/p
Unstable Curve – phase diagram
High temperature
low density
2-Phase phase
medium
Stable
Low temperature
high density
phase

23. Stability Curve
Important Heating and Cooling Processes

24. Stability Curve
Important Heating and Cooling Processes
WA
WA
WA

25. Stability Curve
Important Heating and Cooling Processes
Bremsstrahlung
Compton Cooling
Compton Heating
WA
Photoionization
Cooling by recombination
of metals
Bremsstrahlung
WA
WA

26. Dielectronic recombination
and stability of warm gas in AGN
Susmita Chakravorty et. al,
2008 MNRAS, 384L, 24
C84 1993 to 1996
(Reynolds – Fabian, ‘95)
&
C07, 2007

27. Dielectronic recombination
and stability of warm gas in AGN
Susmita Chakravorty et. al,
2008 MNRAS, 384L, 24
C84 1993 to 1996
(Reynolds – Fabian, ‘95)
&
C07, 2007
Version 5 Nphases log(/T) Mlog(/T)
~105K ~106K
C84 45 2 0.05 0.47 0.05
C07 74 2 0.22 0.46 0.07

28. Cause : Heating and Cooling agents
He+1
Si+10, Si+11, Si+12
Fe+21, Fe+22, Fe+23
O+6, O+7
Fe+17 to Fe+25

29. Cause : Column Densities

30. Cause : Column Densities
He+1
Si+10, Si+11
All of Fe, but
Fe+21, Fe+22, Fe+23
It’s the cooling agents which make a difference

31. Dielectronic recombination
(the most likely candidate?)
 Quantum mechanical calculations
 Experimental estimates
 Revisited by Badnell and coworkers
(2000 - 2007)
 Rates are substantially larger for quite
a few ions.
 The cooling agents are among the
species analysed.
 The differences in stability curves are
due to these changes.
 It is therefore necessary to revisit
older calculations.

32. Dielectronic recombination
(the most likely candidate?)
 Quantum mechanical calculations
 Experimental estimates
 Revisited by Badnell and coworkers
(2000 - 2007)
 Rates are substantially larger for quite
a few ions.
Savin et.al. 1999, ApJS, 123, 687
 The cooling agents are among the
species analysed.
 The differences in stability curves are
due to these changes.
 It is therefore necessary to revisit
older calculations.

33. Future directions
 Extensive quantitative study looking for
other possible causes.
 Check the reliability at lower
temperatures – still a very active domain
of update in atomic data base.