Dielectronic recombination and stability of warm gas in AGN
Upcoming SlideShare
Loading in...5
×
 

Dielectronic recombination and stability of warm gas in AGN

on

  • 477 views

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

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

Statistics

Views

Total Views
477
Views on SlideShare
398
Embed Views
79

Actions

Likes
0
Downloads
0
Comments
0

1 Embed 79

http://astroatom.wordpress.com 79

Accessibility

Categories

Upload Details

Uploaded via as Adobe PDF

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Processing…
Post Comment
Edit your comment

Dielectronic recombination and stability of warm gas in AGN Dielectronic recombination and stability of warm gas in AGN Presentation Transcript

  • Dielectronic recombinationand 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
  • 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
  • What is an Active Galactic Nuclei : Its properties Broad Band Continuum
  • Broad Band ContinuumRadio far-IR optical EUV X-ray
  • Broad Band Continuum
  • in Radio Emission lines in Optical Edge on Radio Galaxy Infrared Type II Seyfert Galaxy Type II QuasarUV and X-rays Gamma Rays Type I Seyfert Galaxy (Inverse Compton) Type I Quasar BL Lac Object
  • in Radio Emission lines in Optical Edge on Radio Galaxy Infrared Type II Seyfert Galaxy Type II QuasarUV and X-rays Gamma Rays Type I Seyfert Galaxy (Inverse Compton) Type I Quasar BL Lac Object
  • in Radio Emission lines in Optical Edge on Radio Galaxy Infrared Type II Seyfert Galaxy Type II QuasarUV and X-rays Gamma Rays Type I Seyfert Galaxy (Inverse Compton) Type I Quasar BL Lac Object
  • 100 pc 0.1 pc Type II Seyfert Galaxy Type I Seyfert Galaxy Type II Quasar Type I Quasar
  • 100 pc 0.1 pc Type II Seyfert Galaxy Type I Seyfert Galaxy Type II Quasar Type I Quasar
  • Broad Band ContinuumRadio far-IR optical EUV X-ray
  • 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)
  • Properties of the warm absorber• Partially ionized gas in our line of sight to AGN• Absorption features are blue shifted relative to opticalemission 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
  • 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 pcWe need to understand warm absorber nature• Is the Warm Absorber in thermodynamic equilibrium?• If so, does the gas have multiphase nature?
  • Stability Curve
  • Stability Curve = L/nR2 /T ~ (prad)ion/pT Curve – phase diagram P
  • CLOUDY http://www.nublado/org/ Inputs Radiation Field GeometryNeutral Composition Density Thickness
  • 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  
  • CLOUDY http://www.nublado/org/ Inputs Radiation Field Geometry TeqNeutral Composition Density Thickness Output  Thermal state & Ionic composition of cloud
  • 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 mediumStable Low temperature high density phase
  • Stability CurveImportant Heating and Cooling Processes
  • Stability CurveImportant Heating and Cooling Processes WA WA WA
  • Stability Curve Important Heating and Cooling Processes Bremsstrahlung Compton Cooling Compton Heating WAPhotoionization Cooling by recombination of metals Bremsstrahlung WA WA
  • Dielectronic recombinationand stability of warm gas in AGN Susmita Chakravorty et. al, 2008 MNRAS, 384L, 24 C84 1993 to 1996 (Reynolds – Fabian, ‘95) & C07, 2007
  • 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, 2007Version 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
  • 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
  • Cause : Column Densities
  • Cause : Column Densities He+1 Si+10, Si+11 All of Fe, but Fe+21, Fe+22, Fe+23It’s the cooling agents which make a difference
  • 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.
  • 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.
  • 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.