Studying AGN with high- resolution X-ray spectroscopy Jelle Kaastra SRON Nahum Arav, Ehud Behar,...
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Transcript of Studying AGN with high- resolution X-ray spectroscopy Jelle Kaastra SRON Nahum Arav, Ehud Behar,...
Studying AGN with high-resolution X-ray spectroscopy
Jelle Kaastra
SRONNahum 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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Introduction:The influence of AGN outflows
• Dispersal heavy elements into IGM & ICM• Ionisation structure IGMevolution 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 ξ=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 ξ=L/nr2 with L ionising
luminosity, n density and r distance from ionising source; ξ essentially ratio photon density / gas density
Question 1:Structure 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
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Ionisation parameter ξ
Em
issi
on m
easu
re
Col
umn
dens
ity Discrete components
Continuousdistribution
Temperature
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Separate components in pressure equilibrium?
• Not all components in press. eq. (same Ξ)
• Division into ξ comps often poorly defined
Continuous NH(ξ) 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 ξ=L/nr²
• L obtained from spectrum
only the product nr² known, not r or n
• Is gas accelerating, decelerating?
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) r~1 pc
• Only applies for some sources, low ξ 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 ξ=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
trnr
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Reverberation: NGC 3783
• RGS data (Behar et al. 2003): no change in
Warm absorber n<300 cm-3, r>10 pc.• EPIC data (Reeves et al. 2003): change in
Warm absorber (larger columns) n>108 cm-3, r<0.02 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
General data analysis issues
• Excellent quality many new steps developed• RGS: full usage multi-pointing mode, refinements
combining spectra with variable hot pixels, λ-scale, effective area, reducing response 2Gb8 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)
14
.
• 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
Fe-K line & variability(Ponti et al.; talk Petrucci et al.)
3-10 keV flux
Line
Int
ensi
ty
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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!
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,Lyβ, & Lyγ 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 can’t 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,
NH<5x1018 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(ξ)
• 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 Lyα O VII triplet
Photoionisation modelling RGS spectrum(Detmers 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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Mehdipour et al. 2011
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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?
A B C
D
E
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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 ξ and NH.
C
D
B
E
Where is the gas?
• Needs t-dependent model• For each of the 5 components: if L increases, ξ
must increase (as ξ=L/nr2)• From 10 continuum model fits predicted ξ
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
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: >10 pc (lack of response)
• Component E: > 1 pc? (lack of response?)
• See also Kriss (talk this afternoon) and poster Ebrero
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Mass loss through the wind
2cML acc
vLvnr )/(2
accloss MM
vnrmM ploss2
2
)/(
cm
v
p
v (km/s) -100 -1000
ξ=1 0.001 0.0001
ξ=1000 1.0 0.1
35
Conclusions
• Deep, multi-wavelength monitoring campaigns (AGN) are rewarding:
• High quality spectra, not limited by statistics
• “Continuous” light curves, allowing to monitor the variations