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Gabriele PontiMarie Curie Fellow at

University of Southampton

High energy evidence for past activity from Sgr A* or its surroundings

R. Terrier, A. Goldwurm, G. Belanger and G. Trap

Sgr A* today: a dormant AGN

Sgr A* low luminosityLedd = 51044 erg s-1

LSgrA*~31033 - 1035 erg s-1

~10-9

Chandra

MSgrA*=4.4106 M Sun

Sgr A* today: in a broader context

Sgr A* low luminosityLedd = 51044 erg s-1

LSgrA*~31033 - 1035 erg s-1

~10-9

Image from Gallo 2010

MSgrA*=3.6106 M Sun

How was the Sgr A* accretion rate in the past?

Are we testimony of a peculiar moment of Sgr A*?

deep in quiescence!

Sgr A*during normal flare

The idea: Molecular clouds as mirrors of past activity

Sunyaev et al. 1993; 1998

Sgr A* sits on the centre of the Central Molecular Zone (CMZ)

107-108 MSun of MC in the central 300 pc

MC are mirrors of the GC past activity

How do the Sgr A* light fronts appears to us at infinity?

Galactic plane from above

Toward the Earth

Sgr A*

The idea: Molecular clouds as mirrors of past activity

Sunyaev et al. 1993; 1998

Sgr A* sits on the centre of the Central Molecular Zone (CMZ)

107-108 MSun of MC in the central 300 pc

MC are mirrors of the GC past activity

Iso-delay light fronts are parabola!

The idea: Molecular clouds as mirrors of past activity

Sunyaev et al. 1993; 1998

Sgr A* sits on the centre of the Central Molecular Zone (CMZ)

107-108 MSun of MC in the central 300 pc

MC are mirrors of the GC past activity

Light fronts appears to us as Parabola

Tool to study history of GC emission

Galactic plane from above

Toward the Earth

Sgr A*

d

rnH

Reflection spectrum from neutral material

Slab of neutral reflecting material

Source

A reflection spectrum should contain:

Fe Kα+β emission linesCompton humpFeK edge

Link between source incident flux and reflection intensity

Open problems:

Sunyaev et al. 1993

GRANAT: Hard X-ray/MC

Which is the origin of the Hard X-ray emission from MC?

ASCA: Fe K from some MC

Koyama et al. 1996

Chandra: Fe K toward SgrA*

Murakami et al. 2001

Chandra: Sgr A cont. variability

Muno et al. 2007

INTEGRAL: MC - reflection

Revnivtsev et al. 2004

FeK: constant intensity!

Multi-instruments: Sgr B2 variability

Inui et al. 2009

Are MC reflecting GC radiation?

Sgr B2 consistent withreflection

But weak detection of variability

Yusef-Zadeh et al. 2002; 2007

Alternatives to reflection: Cosmic Rays

HESS TeV contours on FeK map

Contours 850-micron; FeK map (red); 20 cm (green)

Aharonian et al. (2006)

Cosmic ray electrons

Cosmic ray protons

X-ray from MC: Reflection or Cosmic Rays?

Sgr A* flare ~1.51039 erg s-1 ~ 100 yr ago

Internal source

External source: Sgr A*, X-ray binary, Sgr A East

Low energy cosmic ray electrons or protons

Low energy cosmic ray electrons: Yusef-Zadeh et al. 02; 07 Valinia et al. 00; Low energy cosmic ray protons: Dogiel et al. (2009)Supernovae ejecta: Bykov 02

~ 10 years (~1.2 Ms) of XMM-Newton monitoring of the 15’ region around Sgr A* study the time variability of MC in Sgr A disentangle the models

~ 5 years Suzaku

I will present the new results on the field based on: ~ 7 years (~20 Ms) of INTEGRAL monitoring of the GC region study of the high energy Sgr B2 emission - accurate light curve

The INTEGRAL view of Sgr B2Terrier, Ponti et al. 2010

variability 4.8

Decay time ~8.21.2 yr~core light crossing time

FeK (xmm)

No point source

The INTEGRAL view of Sgr B2Terrier, Ponti et al. 2010

LSgrA*=2-51039 erg s-1

~75-150 years ago

Parallax measurement 120 pc in front of Sgr A*Reid et al. 09

Spectral shape: both low energy cosmic ray electrons and reflection! But low energy cosmic ray electrons huge cosmic ray electron luminosity (~91039 ergs s-1)

Fe K emission in the GC:

CS emission in the GC to locate MC

Where are the MC?Which Fe K emitter are associated to a MC?

Molecular lines as tracers: MC in GC have high densities, CO auto-absorbedUniform and complete scan of the CMZ CS Tsuboi et al. (1999)

Problems:i) Projection - depth in the line of sightii) MC velocity field not Newtonian

BUT Coherent structures similar velocities

TMB = 2.85 K km s-1 1.31022 cm-1

TMB = 75 K km s-1 3.41023 cm-1nH CS= (7.51011Tex TMB dv) /10-2

X-ray spectra of MCModel: wabs*(apec+edge*(PL+Ga+Ga))

Fe K+: E=6.411±0.002 keV, =28±5 eV, norm=7.5±0.510-5 ph cm-2 s-1

EW=955 eV; PL=1.9±0.4, nH~741022 cm-1, =0.030.05

G0.11-0.11

Model: wabs*(apec+edge*(PL+Ga+Ga))

Fe K+: E=6.409±0.002 keV, =28±4 eV, norm=4.7±0.310-5 ph cm-2 s-1

EW=750 eV; PL=1±0.4; nH~431022 cm-1, =0.260.12

the bridge

G0.11-0.11

3,8 4,8

Decay time ~few yr~core light crossing time

Inferring Sgr A*’s luminositySgr B2NH= 81023 cm-2 Dproj= 100 pc but 130 pc in front of

Sgr A* (Reid et al. 2009)

Radius = 7 pcnormFeK= 1.710-4 ph cm-2 s-1

L2-10 keV SgrA* ~ 1.41039 erg s-1 (Revnivtsev et al. 2004)

t = 100 yrG0.11-0.11NH=21022 cm-2 (Amo-Baladron et

al. 2009)

Dproj=25 pcRadius=3.7 pcnormFeK=0.910-4 ph cm-2 s-1

LSgrA* > 1039 erg s-1 t > 75 years

Assuming FlareSgr A* = 1.41039 erg s-1 10 pc behind Sgr A* 100 yr ago

Galactic plane from above

Sgr A*

Toward the Earth

Other constraints on Sgr A* activity50 km s-1

NH=91022 cm-2

Dproj=6 pcRadius=4.7 pcnormFeK<1.110-5 ph cm-2 s-1

LSgrA* < 81035 erg s-1 t < 60-90 years

Coil et al. (2000)

Galactic plane from above

Toward the Earth

The bridge

Bridge 2

Bridge 1

Bridge 3

Bridge 4

11,3 9,1

0,5

2,6 8,6

0,8

0,4

13,3 Bridge 5Bridge 6 Bridge 7

Super-luminal motion?

Regions causally disconnected!! No propagation of single event Cosmic ray - internal source excluded! Many un-correlated variations Similar variation - distant source L15pc~1.31038 erg s-1 - Binary in peculiar position close to bridge Flare Sgr A* (Sunyaev & Churazov 1998)

Bridge 1Bridge 2 Bridge 3Bridge 4

Direction toward Sgr A*

How can a superluminal echo happen?

Projector

To change slide 1 s

Wall

Velocity of the variation observed on the screen = 1 m/s

Wall distant 1 m from the projector

How can a superluminal echo happen?

Projector

To change slide 1 s

Wall

If the wall is distant 600000 km from the projectorThe variation appears on the screen at v=2c!

Because the real “physical” variation happens at the level of the projector and not of the wall

Possible past activity of Sgr A*Galactic plane from above

Toward the Earth

BridgeNH=91022 cm-2

Dproj=15 pcRadius=1.1 pcnormFeK=1.110-5 ph cm-2 s-1

LSgrA* ~ 1.31038 erg s-1

Assuming L~1.41039 erg s-1

60 pc Sgr A* activity 400 yr

Basic unknown: MC distance!

Assuming a luminosity of 1039 erg s-1 MC distance Consistent with unique outburst

Nothing special about 1039 erg s-1 if MC are more distant higher Sgr A* luminosity

The in-glorious past of Sgr A*

1041

1040

1039

1038

ergs s-1

153 pc 307 pc 460 pc

The projected distance between Sgr A* and MC1, MC2 and the bridge are unknownHOWEVERtheir physical properties indicate that they are within the CMZ (~300 pc from Sgr A)

Assuming they are illuminated by Sgr A*, it is possible to pose a limit to its recent luminosity

If the CMZ is filled with “similar” MC Sgr A* never reached L>1041 ergs s-1, since the end of the Roman Empire

Sgr A* barely exited from the quiescent state, since the Romans

d

rnH

Sgr A*

Suzaku detection of Ar, Ca, Cr, Mn Kα emission

Nobukawa et al. 2010 discover Kα emission from Ar, Ca, Cr and Mn in the MC X-ray spectrum

Reflection: all elements consistent with ~2 Solar

Cosmic electrons: consistent but ~4 Solar

Can irradiation from external sources explain the emission from ALL MC?

Fukuoka et al. 2009

G0.174-0.233 EW FeK = 950 eV Reflection

G0.162-0.217 EW FeK = 360 eV LECRE

Summary:

Observe Fe K/Gamma-ray fading of Sgr B2

Observe another MC (G0.11-0.11) reflecting the same flare (~100 years ago)

50 km s-1 has no Fe K line Sgr A* luminosity < 81035 erg s-1 in the last 60-90 years

Observe an apparent superluminal motion (in the bridge MC) Cosmic rays or Internal source excluded the illuminating source has to be far from the arm ( >2-4 times the apparent displacement) Sgr A* activity - best interpretation (but luminosity required is few1039 erg s-1 binary not excluded)

Kα emission lines require abundances 2 Solar

MC emission consistent with a single Sgr A* period of activity of few hundreds years and lasted until ~100 years ago As observed 1/3 of MC should be FeK bright

Which is the mechanism that produces such outbursts? 106 times quiescence for >20 yr Partial stellar capture? (Yu et al. 2011)

What is going to happen if Sgr A* goes to Eddington? To the GC surrounding material? To the Earth?

Study of the past activity of Sgr A*

New questions: