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= ), whose μ QSO 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 a lower limit to the BH spin] (Barcons et al. 2011) =Innermost Stable Circular Orbit

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 R ISCO, 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 limit Strong 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 … 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 ISCO Small 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>0.98NGC3783 – 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 > 0.98a < 0.31 (Patrick et al. 2012) χ 2 =1340/1237 χ 2 =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/Z solar >8.3 a>0.96, i≈36º, Z/Z solar ≈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/Z solar >8.3 a>0.96, i≈36º, Z/Z solar ≈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 complexAGN are X-ray variable (Risaliti & Elvis 2002) NGC4051 (McHardy et al. 2005) EPIC-pn Fe K α “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(N H )=24, log( ξ )=3, C f =0.5 Reflection from ~pc-scale optically thick gas Ionized reflection (disk, NLR?) Rel ic. Fe line: a=0.998, i=30º, EW=150 eV, q=3 Total 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 profile Approaching disk profile Total profile Occulting cloud N H =3×10 23 cm -2 Simulation with a 2m 2 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 , 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