Studying AGN with high-resolution X-ray spectroscopy

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Studying AGN with high-resolution X-ray
spectroscopy

• Jelle Kaastra
• SRON
• Nahum Arav, Ehud Behar, Stefano Bianchi, Josh
  Bloom, Alex Blustin, Graziella Branduardi-Raymont,
  Massimo Cappi, Elisa Costantini, Mauro Dadina,
  Rob Detmers, Jacobo Ebrero, Peter Jonker, Chris
  Klein, Jerry Kriss, Piotr Lubinski, Julien
  Malzac, Missagh Mehdipour, Stéphane Paltani,
  Pierre-Olivier Petrucci, Ciro Pinto, Gabriele
  Ponti, Eva Ratti, Katrien Steenbrugge, Cor de
  Vries

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IntroductionThe influence of AGN outflows

• Dispersal heavy elements into IGM ICM
• Ionisation structure IGM
• ??evolution host galaxy
• How created? Structure? Mass energy?
  Confinement?
• Crucial to understanding central engine
• Accretion process
• Energy budget

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AGN outflows in a nutshell

• Photo-ionised gas
• v -100 to -1000 km/s
• Seen through line and continuum absorption
• Spectrum ? ionic column densities ? ionization
  parameter ?L/nr²

• Kaastra et al. 2000

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Photoionisation modelling

• Radiation impacts a volume (layer) of gas
• Different interactions of photons with atoms
  cause ionisation, recombination, heating
  cooling
• In equilibrium, ionisation state of the plasma
  determined by
• spectral energy distribution incoming radiation
• chemical abundances
• ionisation parameter ?L/nr2 with L ionising
  luminosity, n density and r distance from
  ionising source ? essentially ratio photon
  density / gas density

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Question 1Structure outflow

• Is it more like rather uniform density clouds in
  pressure equilibrium?
• Or is it more like coronal streamers, with
  lateral density stratification?

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Absorption measure distribution
Discrete components
Emission measure Column density
Continuous distribution
Ionisation parameter ?
Temperature
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Separate components in pressure equilibrium?

• Not all components in press. eq. (same ?)
• Division into ? comps often poorly defined
• ? Continuous NH(?) distribution?
• Others fit discrete components
• What's going on?

Steenbrugge et al. 2005
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Question 2 Where is the gas?

• Photo-ionization modeling ? ?L/nr²
• L obtained from spectrum
• ? only the product nr² known, not r or n
• Is gas accelerating, decelerating?

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Density estimates line ratios

• C III has absorption lines near 1175 Å from
  metastable level
• Combined with absorption line from ground (977 Å)
  this yields n
• ? n 3x104 cm-3 in NGC 3783 (Gabel et al. 2004)
  ? r1 pc
• Only applies for some sources, low ? gas
• X-rays have similar lines, but sensitive to
  higher n (e.g. O V, Kaastra et al. 2004) no
  convincing case yet

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Density estimates reverberation

• If L increases for gas at fixed n and r, then
  ?L/nr² increases
• ? change in ionisation balance
• ? column density changes
• ? transmission changes
• Gas has finite ionisation/recombination time tr
  (density dependent as 1/n)
• ? measuring delayed response yields tr?n?r

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Reverberation NGC 3783

• RGS data (Behar et al. 2003) no change in
• Warm absorber ? nlt300 cm-3, rgt10 pc.
• EPIC data (Reeves et al. 2003) change in
• Warm absorber (larger columns) ? ngt108 cm-3,
  rlt0.02 pc.

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Observation campaign Mrk 509

• Core 10 x 60 ks XMM, spaced 4 days (RGS, EPIC
  OM all used!)
• Simultaneous Integral 10 x 120 ks
• Followed by 180 ks Chandra LETGS, simultaneous
  with 10 orbits COS (HST)
• Preceded with Swift (UVOT, XRT) monitoring
• Supplemented with ground-based (WHT, Pairitel)
  photometry grism
• Period 4 Sept 13 Dec 2009 (100 days)
• 7 papers submitted/accepted, 8 in progress

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General data analysis issues

• Excellent quality ? many new steps developed
• RGS full usage multi-pointing mode, refinements
  combining spectra with variable hot pixels,
  ?-scale, effective area, reducing response 2Gb?8
  Mb, rebinning) See Kaastra et al. 2011 see
  auxilary programs in SPEX distribution
  www.sron.nl/spex
• PN Triggered by our campaign improved gain cal
• OM extended wavelength range optical grism
• HST/COS extensive efforts to improve data
  analysis for this high-quality spectrum
• SPEX allows simultaneous fitting high-res UV
  X-ray spectra

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Broad-band spectrum variability(Mehdipour et
al., Petrucci et al., talks this afternoon)
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Fe-K line variability(Ponti et al. talk
Petrucci et al.)
Line Intensity

• Broad and neutral Fe K emission well correlated
  with continuum emission on few days time-scales.
• No relativistic profile
• Origin outer disc or inner BLR

3-10 keV flux
.
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OM Grism spectrum
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UV-optical variability(OM, Swift)

• Source was in outburst (0.1 dex in UV) right in
  the middle of ourt campaign!

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ISM absorption(talk Pinto et al. on Monday)
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Abundances(Steenbrugge et al., poster G45)
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COS FUSE UV Absorption lines in Mrk 509(Kriss
et al., talk this afternoon)

• O VI,Lyß, Ly? from FUSE (Kriss et al. 2000)
• 14 velocity components seen in COS UV spectrum
• C IV doublet split by only 500 km/s, so grey
  regions cant be used for optical-depth
• Red lines velocities X-ray absorbers
  XMM-Newton/RGS
• Blue lines velocities X-ray absorbers
  Chandra/LETGS

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LETGS COS data(Ebrero et al., poster G14)

• X-rays outflow with 3 distinct ionization phases
  in form of multi-velocity wind. UV spectra
  absorption system with 13 kinematic components
• Analysis kinematic properties column densities
  absorbers ? UV-absorbing gas co-located with
  embedded in lower density high-ionization X-ray
  absorbing gas

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Stacked RGS spectrum

• Galactic O I edge
• Several narrow absorption lines
• Detection 31 individual ions
• Tight upper limits column densities 18 other ions
• Two main velocity components (40 and -300 km/s)
• Highly ionised ions in general higher velocity

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No O I from host galaxy
O I host galaxy (not detected, NHlt5x1018 cm-2)
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X-ray analysis in more detail

• Fit spectra using a power law modified
  blackbody (or even a spline) continuum
• Where needed, add emission lines BLR or NLR
  X-ray lines (no relativistic lines needed)
• Fit warm absorber using a model ? ionic or total
  column densities
• Using photo-ionisation model, derive absorption
  measure distribution NH(?)
• Spectral fits done with SPEX, global fits

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Sample high-resolution spectra
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Example of broad emission lines
O VIII Lya
O VII triplet
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Photoionisation modelling RGS spectrum(Detmers
et al. 2011)
Mehdipour et al. 2011

• Use time-averaged SED
• Test dependence on SED
• Proto-solar abundances
• Multiple ionisation, 3 velocity components
• Same ion may be present in more than one
  velocity/ionisation component!

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Discrete versus continuous absorption measure
distribution?

• Column densities well approximated by sum of 5
  components (see table)
• Higher column for higher ionisation parameter
• But what about a continuous model?

E
D
C
A
B
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Continuous model

• Fitted columns with continuous (spline) model
• Surprise comps C D pop-up as discrete
  components!
• Upper limits FWHM 35 80
• Component B ( A) too poor statistics to prove if
  continuous
• Component E also poorer determined correlation ?
  and NH.

D
E
C
B
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Where is the gas?

• Needs t-dependent model
• For each of the 5 components if L increases, ?
  must increase (as ?L/nr2)
• From 10 continuum model fits ? predicted ? change
  for each of 10 observations, compared to average
  spectrum
• If gas responds immediately, transmission outflow
  changes immediately

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Expected response absorbers for 0.1 dex
luminosity increase
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Time-dependent photo-ionisation

• Time evolution ion concentrations ni
• dni/dt Aij(t) nj
• Aij(t) contains t-dependent ionisation
  recombination rates

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Location photoionised gas(work in progress)

• Component A Rotating, low ionisation disk high
  velocity outflow, 3 kpc (direct imaging O III
  5007, Philips 1986)
• Component C gt10 pc (lack of response)
• Component E gt 1 pc? (lack of response?)
• See also Kriss (talk this afternoon) and poster
  Ebrero

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Mass loss through the wind
v (km/s) -100 -1000
?1 0.001 0.0001
?1000 1.0 0.1
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Conclusions

• Deep, multi-wavelength monitoring campaigns (AGN)
  are rewarding
• High quality spectra, not limited by statistics
• Continuous light curves, allowing to monitor
  the variations