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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: