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Why can’t we?

Why can’t we?. Matteo Guainazzi (European Space Astronomy Centre). Outline. Why do we astrophysically care? Where do we stand now? What do we (observationally) need to make a step forward?. Why do we care?.

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Why can’t we?

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  1. Why can’t we? MatteoGuainazzi(European Space Astronomy Centre)

  2. Outline • Why do we astrophysicallycare? • Where do we stand now? • What do we (observationally) need to make a step forward?

  3. 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 ]

  4. SMBH Accretion history (Berti & Volonteri 2008; Fanidakis et al. 2009; courtesy G.Miniutti) • 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

  5. SMBH spin driving the AGN evolution? (Garofalo et al. 2010) ≈ time Blanford-Payne effect Blanford-Znajek effect Accretion disk Jets BH

  6. Frequencies in a relativistic disk (Aschenbach et al. 2004) (Nowak & Lehr 1998; Merloni et al. 1999) SgrA* [Kepler frequency] [epicyclic frequencies] [Lense-Thirring frequency] • a, M can be determined if one knows/assumes the rwhere 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

  7. How to measure the BH spin (Barcons et al. 2011) (Bardeen et al. 1972; courtesy G.Matt) Retrograde disk =Innermost Stable Circular Orbit a≈0 Prograde disk a≈1 [we actually measure a lower limit to the BH spin]

  8. Relativistic X-ray spectroscopy: XRB (Noble et al. 2011) (courtesy J.McClintock) In XRB the thermal emission of the accretion disk peaks ≈1 keV, and is directly observable a = 0.0, 0.2, 0.4 Flux [NT=Novikov & Thorne 1973] One needs accurate measurements of the inclination angle iand of the distance D to get RISCO, and accurate measurements of the mass to get a

  9. Relativistic X-ray spectroscopy: AGN (Fabian 2000; courtesy G.Miniutti) Weak field limit Strong field limit

  10. Current measurements (de la Calle-Pérez et al.2010; Fabian et al. 2010; Brenneman et al. 2011; Tang et al. 2011 … and many others) Error bars are purely statistical. Let’s have a look at the systematics XRB: full range of progradespins (Mc Clintock et al. 2011)

  11. Systematic errors on a: disk structure (Reynolds & Fabian 2008) Bleeding of the Fe emitting region beyond the ISCO Small effect to due strong rise in ξ [i.e., decrease in n]

  12. Systematic errors on a: spectral fitting (Patrick et al. 2012) (Brenneman et al. 2012) NGC3783 – Suzaku – a>0.98 NGC3783 – Suzaku – a<0.31 Same data, different analyzers and model

  13. Systematic errors on a: spectral fitting (Patrick et al. 2012) a > 0.98 a < 0.31 χ2=1340/1237 χ2=1329/1234

  14. Systematic errors on a: spectral fitting again (Lohfink et al. 2012) Fairall 9 a>0.96, i≈36º, Z/Zsolar≈0.75 a≈0.52, i≈48º, Z/Zsolar>8.3 Model “A” Model “B” Multi-epoch fitting of Suzakuand XMM-Newton data Same data, same analyzer, different models. Why these differences? How can we solve them?

  15. Clues to a solution I.: high-energy focusing (Lohfink et al. 2012) Fairall 9 a>0.96, i≈36º, Z/Zsolar≈0.75 a≈0.52, i≈48º, Z/Zsolar>8.3 Model “A” Model “B” Multi-epoch fitting of Suzakuand XMM-Newton data Same data, same analyzer, different models. Why these differences? How can we solve them?

  16. Why so difficult? (McHardy et al. 2005) (Risaliti & Elvis 2002) AGN X-ray spectra are complex AGN are X-ray variable NGC4051 • EPIC-pn Fe Kα “line photons” (in Mkn766): • [~3% of the local continuum] • ~30 in 1 hour • ~800 in 1 day

  17. Clues to a solution II: - high-resolution (Bianchi et al. 2010; Barcons et al. 2011) Ionized absorber: log(NH)=24, log(ξ)=3, Cf=0.5 Reflection from ~pc-scale optically thick gas Ionized reflection (disk, NLR?) Relic. Fe line: a=0.998, i=30º, EW=150 eV, q=3 Total spectrum

  18. Clues to a solution III.: area (Barcons et al. 2011) (Iwasawa et al. 2004) Measuring black holes in AGN | Matteo Guainazzi | “Testing Gravity with Astrophysical and Cosmological Observations, IPMU, 23/1/2012 Simulations XMM-Newton

  19. Accretion disk occultation (Risaliti et al. 2011) Simulation with a 2m2 X-ray observatory Occulting cloud NH=3×1023 cm-2 Receding disk profile Approaching disk profile Total profile

  20. 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[seeKaras’ 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

  21. Testing GR with broad lines (Johanssen & Psaltis 2011, 2012) Contours of the required line accuracy 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 θ= 30º MCG-6-30-15, 300ks SXS: σ≅5%

  22. 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[seeKaras’ 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

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