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