Matteo Guainazzi (European Space Astronomy Centre) WHY CAN’T WE?
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Transcript of Matteo Guainazzi (European Space Astronomy Centre) WHY CAN’T WE?
Matteo Guainazzi (European Space Astronomy Centre)
WHY CAN’T WE?
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Outline
Why do we astrophysically care? Where do we stand now? What do we (observationally) need
to make a step forward?
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Why do we care?
SMBH spin distribution in the local Universe may carry the imprinting of the accretion history
Stellar-mass BH spin reflects the progenitor collapse history
BH spin may ultimately power relativistic jets General Relativity effects on the accretion flow
depend on the BH spin BH spin may be telling us how energy can be
extracted from a black hole SMBH high spin may drive high-speed BH recoils
[BH = Black Hole; SMBH = Super-Massive Black Hole ]
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
SMBH Accretion history
In AGN the distribution of BH spin traces the accretion history Mergers only
a≈0.7 Mergers+coherent
a≈1 Mergers+chaotic
a≈0 In XRBs the BH
spin is natal
(Berti & Volonteri 2008; Fanidakis et al. 2009; courtesy G.Miniutti)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
SMBH spin driving the AGN evolution?
Blanford-Znajek effect Blanford-Payne effect
BH
Jets
Accretion disk
≈ time
(Garofalo et al. 2010)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Frequencies in a relativistic disk(Nowak & Lehr 1998; Merloni et al. 1999) (Aschenbach et al. 2004)
[Kepler frequency]
[epicyclic frequencies]
[Lense-Thirring frequency]
SgrA*
• a, M can be determined if one knows/assumes the r where each frequency occurs (HFQPOs)• Aschenbach (2004): parametric resonance model predicting a different “Thorne limit” (a=0.99616), whoseμQSO black hole masses are consistent with dynamical measurements
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
How to measure the BH spin
Retrograde disk
Prograde disk
(Bardeen et al. 1972; courtesy G.Matt)
a≈0
a≈1
[we actually measure alower limit to the BH spin]
(Barcons et al. 2011)
=In
nerm
ost
Sta
ble
Cir
cula
r O
rbit
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Relativistic X-ray spectroscopy: XRB
In XRB the thermal emission of the accretion disk peaks ≈1 keV, and is directly observable
(courtesy J.McClintock) (Noble et al. 2011)
a = 0.0, 0.2, 0.4
[NT=Novikov & Thorne 1973]
One needs accurate measurements of the inclination angle i and of the distance D to get RISCO, and accurate
measurements of the mass to get a
Flux
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Relativistic X-ray spectroscopy: AGN
Weak field limitStrong field limit
(Fabian 2000; courtesy G.Miniutti)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Current measurements
Error bars are purely statistical.Let’s have a look at the systematics
(de la Calle-Pérez et al.2010; Fabian et al. 2010; Brenneman et al. 2011; Tang et al. 2011 … and many others)
XRB: full range of prograde spins (Mc Clintock et al. 2011)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Systematic errors on a: disk structure
Bleeding of the Fe emitting region beyond the ISCOSmall effect to due strong rise in ξ[i.e., decrease in n]
(Reynolds & Fabian 2008)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Systematic errors on a: spectral fitting
NGC3783 – Suzaku – a>0.98 NGC3783 – Suzaku – a<0.31
(Brenneman et al. 2012) (Patrick et al. 2012)
Same data, different analyzers and model
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Systematic errors on a: spectral fitting
a > 0.98 a < 0.31
(Patrick et al. 2012)
χ2=1340/1237χ2=1329/1234
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Systematic errors on a: spectral fitting again
Multi-epoch fitting of Suzaku and XMM-
Newton data
Model “A” Model “B”
Fairall 9 a≈0.52, i≈48º, Z/Zsolar>8.3a>0.96, i≈36º, Z/Zsolar≈0.75
Same data, same analyzer, different models. Why these differences? How can we solve them?
(Lohfink et al. 2012)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Clues to a solution I.: high-energy focusing
Multi-epoch fitting of Suzaku and XMM-
Newton data
Model “A” Model “B”
Fairall 9 a≈0.52, i≈48º, Z/Zsolar>8.3a>0.96, i≈36º, Z/Zsolar≈0.75
Same data, same analyzer, different models. Why these differences? How can we solve them?
(Lohfink et al. 2012)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Why so difficult?
AGN X-ray spectra are complex
AGN are X-ray variable
(Risaliti & Elvis 2002)
NGC4051
(McHardy et al. 2005)
EPIC-pn Fe Kα “line photons” (in Mkn766):• [~3% of the local continuum] • ~30 in 1 hour• ~800 in 1 day
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Clues to a solution II: - high-resolution
Ionized absorber: log(NH)=24, log(ξ)=3, Cf=0.5Reflection from ~pc-scale optically thick gasIonized reflection (disk, NLR?)Relic. Fe line: a=0.998, i=30º, EW=150 eV, q=3Total spectrum
(Bianchi et al. 2010; Barcons et al. 2011)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Measuring black holes in AGN | Matteo Guainazzi | “Testing Gravity with Astrophysical and Cosmological Observations, IPMU, 23/1/2012
Clues to a solution III.: area(Barcons et al. 2011) (Iwasawa et al. 2004)
Simulations XMM-Newton
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Accretion disk occultation
Receding disk profileApproaching disk profileTotal profile
Occulting cloudNH=3×1023 cm-2
Simulation with a 2m2 X-ray observatory(Risaliti et al. 2011)
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Conclusions
BH spin in XRB: teen-ager level of maturity three complementary methods: continuum spectroscopy, line spectroscopy and
timing cross-calibration, good consistency (e.g.: CygX-1, Fabian et al. 2012) Measurements available on ≈10 objects
BH spin in AGN: infant level of maturity Only via disk reflection spectroscopy Measurements on ≈20 objects Results still dominated by ≈100% systematic uncertainties
We need: Broad band coverage (NuSTAR already helps) High-resolution in the Fe-K band (Astro-H will soon help) Area/X-ray polarimetry[see Karas’ talk] (none will help in the next decade)
Rewarding scientific pursuit X-ray band is the only one where BH spin can be directly measured SMBH spins are unique tracers of the accretion history We can’t understand accretion physics without knowing the BH spin (and other
way round) Unique window to test GR in the high-field limit
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Testing GR with broad lines(Johanssen & Psaltis 2011, 2012)
Contours of the required line accuracy
θ= 30º
MCG-6-30-15, 300ks SXS: σ≅5%
Eventually, if we are able to describe very accurately the relativistically broadened profile of the iron line, and if we believe we accurately understand the accretion flow, we may even be able to constrain alternative GR formulations
M.Guainazzi, “How can X-rays help us understanding astrophysical black holes?”, AXRO2012, Prague, 11/12/2012
Conclusions
BH spin in XRB: adolescent science three complementary methods: continuum spectroscopy, line spectroscopy and
timing cross-calibration, good consistency (CygX-1, Fabian et al. 2012) Measurements available on ≈10 objects
BH spin in AGN: infant science Only via disk reflection spectroscopy Measurements on ≈20 objects Results still dominated by ≈100% systematic uncertainties
We need: Broad band coverage (NuSTAR already helps) High-resolution in the Fe-K band (Astro-H will soon help) Area/X-ray polarimetry[see Karas’ talk] (none will help in the next decade)
Rewarding scientific pursuit X-ray band is the only one where BH spin can be directly measured SMBH spins are unique tracers of the accretion history We can’t understand accretion physics without knowing the BH spin (and other
way round) Unique window to test GR in the high-field limit