Science with Simbol-X

0.1 MB·

by  F. Fiore

Mem.S.A.It.Vol.75,282
(cid:13)c SAIt 2004 Memoriedella
S
ien
e with Simbol-X
F.Fiore1,M.Arnaud2,U.Briel3,M.Cappi4,A.Comastri5,A.Decourchelle2,R.Della
Ceca6,P.Ferrando7,C.Feruglio1,R.Gilli5,P.Giommi8,A.Goldwurm7,P.Grandi4,
P.Laurent7,F.Lebrun7,G.Malaguti4,S.Mereghetti9,G.Micela10,G.Pareschi6,
8 E.Piconcelli1,S.Puccetti8,J.P.Roques11,G.Tagliaferri6,andC.Vignali12
0
0
2 1 INAF-OARoma,ViaFrascati33,I-00040Monteporzio,Italy
2 LaboratoireAIM,DAPNIA/Serviced’Astrophysique-CEA/DSM-CNRS-Universite´
n
ParisDiderot,Baˆt.709,CEA-Saclay,F-91191Gif-sur-YvetteCedex,France
a
3 MaxPlanckInstitu¨tfu¨rExtraterrestrischePhysik,85748Garching,Germany
J
4 INAF-IASF-Bo,viaGobetti101,40129Bologna,Italy
2
5 INAF-OABo,viaRanzani1,Bologna,Italy

6 INAF-OABrera,viaBianchi46,23807Merate,Italy
]
h 7 UMR7164,LaboratoireAPC&DSM/DAPNIA/Serviced’AstrophysiqueCEA/Saclay,
p 91191Gif-sur-YvetteCedex,France
- 8 ASIASDCc/oESRIN,00044Frascati,Italy
o 9 INAF-IASF-Mi,ViaBassini15,20133Milano,Italy
r 10 INAF-OAPa,PalazzodeiNormanni,90134Palermo,Italy
t
s 11 CESR,BP4346,31028ToulouseCedex,France
a 12 DipartimentodiAstronomia,Universita´diBologna,viaRanzani1,Bologna,Italy
[

1
v Abstract. Simbol-X isaFrench-Italianmission, withaparticipation of German labora-
9 tories, for X-ray astronomy inthe wide0.5-80 keV band. Taking advantage of emerging
0 technology inmirror manufacturing andspacecraft formation flying, Simbol-X willpush
4 grazing incidence imaging up to ∼ 80 keV, providing an improvement of roughly three
0 ordersofmagnitudeinsensitivityandangularresolutioncomparedtoallinstrumentsthat
. have operated so far above 10 keV. This will open a new window in X-ray astronomy,
1
0 allowingbreakthrough studiesonblackholephysicsandcensusandparticleacceleration
8 mechanisms.WedescribebrieflythemainscientificgoalsoftheSimbol-Xmission,giving
0 afewexamplesaimedathighlightingkeyissuesoftheSimbol-Xdesign.
:
v Keywords.BlackHoles–ParticleAcceleration–HardX–rays
i
X
r
a 1. Introduction of the isotropic, extragalactic Cosmic X-Ray
Background (CXB), discovered by Riccardo
AseminalresultobtainedwithHEAO-1atthe
Giacconi, Bruno Rossi and collaborators dur-
end of the 70’ is the precise measure of the
ing one of the first rocket-borne X–ray ex-
spectrum (from a few keV up to ∼ 100 keV)
periments in 1962. The HEAO1 data showed
thattheCXBenergydensityhasabroadmax-
Sendoffprintrequeststo:F.Fiore
Fioreetal.:SciencewithSimbol-X 283
imum around 30 keV, where it is about 5 most any type of X-ray source, from Galactic
times higher than at 1 keV and 50% higher and extragalactic compact sources, supernova
than at 10 keV. It was soon realized that remnant(SNR),youngstellarobjectsandclus-
the CXB is most likely due to the contribu- tersofgalaxies,rightinthedomainwhereac-
tion of many discrete sources at cosmologi- cretionprocessesandaccelerationmechanisms
cal distances (Setti&Woltjer1979). Most of havetheirmainsignatures.Thispapersumma-
these sourcesare activegalacticnuclei,AGN, rizesthemainscientificgoalsoftheSimbol-X
implying that the CXB energy density pro- mission,puttingtheemphasisonthe coresci-
vides an integral estimate of the mass accre- enceobjectives.
tion rate in the Universe, and therefore of
the super-massiveblackhole (SMBH) growth
2. Mainscientificobjectivesofthe
andmassdensity.Unfortunately,theintegrated
light fromall sourcesdetected in HEAO1 all- Simbol-Xmission
skysurveycoulddirectlyexplainonlylessthan
Taking advantage of emerging technology in
1%oftheCXB. Indeed,theuseofcollimated
mirror manufacturing (Pareschi et al. these
detectors on board first UHURU and Ariel-V,
proceedings) and spacecraft formation fly-
and then HEAO1 in the 1970 decade led to
ing(LaMarleetal.2007),Simbol-Xwillpush
the discovery of < 1000 X-ray sources in the
grazing incidence imaging up to ∼ 80 − 100
wholesky.
keV, providing an improvement of roughly
X-ray imaging observations, performed threeordersofmagnitudeinsensitivityandan-
first by Einstein and ROSAT in the soft X- gular resolution compared to all instruments
ray band below ∼ 3 keV, and then by ASCA, thathaveoperatedsofarabove10keV(Fig.3
BeppoSAX, XMM–Newton and Chandra up inFerrandoetal.,theseproceedings,compares
to 8-10 keV, detected tens of thousandsof X- the predicted Simbol-X sensitivity to that of
ray sources, and resolved nearly 100% of the previousexperimentsin the 1-100keV band).
CXB below a few keV and up to 50% at 6- The verywide discoveryspace thatSimbol-X
8 keV. These observations increased by or- will uncover is particularly significant for the
dersofmagnitudethediscoveryspaceforcom- advancementoftwolargeandcrucialareasin
pact objects (both Galactic neutron stars and high-energyastrophysicsandcosmology:
blackholesandAGN)andforthermalplasma
sources.However,theystillleaveopenfunda- 1. Blackholephysicsandcensus
mentalissues,suchaswhatismakingmostof 2. Particleaccelerationmechanisms.
theenergydensityoftheCXBat∼30keV.
Above10keVthemostsensitiveobserva- Thesetwobroadtopicsdefinethecoresci-
tionshavebeenperformedsofarbycollimated entificobjectivesofSimbol-X.
instruments, like the BeppoSAX PDS, and Because of the tight links between galaxy
bycodedmasksinstruments,likeINTEGRAL bulges and their central SMBH, obtaining
IBIS and Swift BAT. Only a few hundred a complete and unbiased census of SMBH,
sources are know in the whole sky in the 10- through direct observations at the energies
100 keV band, a situation recalling the pre– where the Cosmic X-ray Background (CXB)
Einstein era at software energies. A new win- energy density peaks, is crucial for our un-
dowinX-rayastronomyabove10keVmustbe derstanding of the formationand evolution of
opened,producinganincreaseofthediscovery galaxies and their nuclei. Furthermore, BH
spacesimilartothatobtainedwiththefirstX- environment is the only known place in the
rayimagingmissions.Thiswillbeachievedby Universewheregeneralrelativitycanbetested
Simbol-X,aformationflightmissioncurrently beyondtheweak-fieldlimit.
under preparation by France and Italy, with a About particle acceleration, we are still
participation from German laboratories. Very lacking firm evidences of hadron acceleration
much like the Einstein Observatory, this mis- in astronomical sites (despite clearly seeing
sionwillhavethecapabilitiestoinvestigateal- huge electron accelerations), and we are still
284 Fioreetal.:SciencewithSimbol-X
searching for the origin of the high-energy ourselvestoprovideafewexamples,highlight-
photons and cosmic rays. Hard X-rays ob- ing the key issues about the Simbol-X design
servations,possibly combinedwith γ–ray and with respect to possible competitors, and the
TeVobservations,areinvaluabletoolstoiden- synergieswithotherlargeobservationalinfras-
tifytheprocessesatworkinaccelerationsites tructuresthatarealreadyproducingdataorthat
suchasSNRandjets.Toachieveitscorescien- will producedata at the time of the Simbol-X
tificobjectivesSimbol-Xshould: mission(2013-2018).
1.1 resolveatleast50%oftheCXBintheen-
ergyrangewhereitpeaks,thusprovidinga 2.1.ThecosmicX-raybackgroundand
morecompletecensusofSMBH; thecensusofSMBHblackholes
1.2 solve the puzzle on the origin of the hard
The CXB is currently regarded as the inte-
X-ray emission from the Galactic centre,
gratedoutputoftheaccretionprocesseswhich
whichharborstheclosestSMBH;
took place during the cosmic history. These
1.3 constrain the physics and the geometryof
processesledtothegrowthofSMBHingalac-
theaccretionflowontobothSMBHandso-
ticnuclei(e.g.Marconietal.2004),whichwe
larmassBH;
observeinanactivephaseinAGNandinaqui-
1.4 mapthemessyenvironmentaroundSMBH
escent phase through their dynamical effects
characterized by the coexistence of gas
components with different dynamical, on their surroundings, at the centre of nearby
galaxiesandindeedinourown.
physicalandgeometricalproperties;
AGN making most of the CXB below a
2.1 constrainaccelerationprocessesintherel-
ativisticJetsofblazarsandGRB; few keV have a spectrum much softer than
the CXB energy density spectrum, implying
2.2 probe acceleration mechanisms in the
thatthemaximumat30keVwouldbemissed
strong electromagnetic and gravitational
fieldsofpulsars; by a factor about 3. A simple solution of this
“paradox” was proposed again by Setti and
2.3 measure the maximum energy of electron
Woltjer (1989), and requires a population of
accelerationinsupernovaremnantsshocks,
andsearchforhadronaccelerationinthese AGN highly obscured in soft X-rays by pho-
sites; toelectric absorption. The size of this pop-
2.4 search for and map the non-thermalemis- ulation should be 2-3 times that of the un-
sion in clusters of galaxies, and if con- obscured AGN to reproduce the CXB spec-
trum (see Comastri et al. these proceedings).
firmed,determineits originandits impact
onclustersevolution. ChandraandXMM-Newtonsurveyshavebeen
able to detect many obscured, Compton-thin
In addition to these top priorityobjectives AGN(N <1024cm−2).However,duetotheir
H
Simbol-Xwillbecapableofperformingbreak- limitedbandpass,ChandraandXMMdiscov-
throughstudiesonseveralotherareaslike: ered only a handful of Compton-thick AGN
(CT; N > 1024 cm−2). Therefore,at present,
1. theequationofstateandthemagneticfield H
onlyafewCTAGNareknownbeyondthelo-
ofneutronstars;
cal Universe (see Della Ceca et al. these pro-
2. nucleosynthesisinyoungSNR;
ceedings).
3. theformationofstarsandplanets;
According to both the most up-to-
4. non-thermalemissionofactivestars;
date AGN synthesis models for the CXB
5. shocks in the intracluster medium pervad-
(Gillietal.2007), the volume density of CT
inggroupsandclustersofgalaxies;
AGN should be of the same order of magni-
6. extended thermal plasmas in Galactic and
tudeofthatoftheunobscuredandmoderately
extragalacticsources.
obscured AGN. High sensitivity, hard X-ray
Of course we cannot discuss here in de- observations like those that Simbol-X will be
tailallabovetopics,theseareexhaustivelypre- abletoperforminthe10-60keVbandholdthe
sented in all papers in this volume. We limit key to uncover, and study in detail, this long
Fioreetal.:SciencewithSimbol-X 285
Fig.1. The combined CZT+SDD 1M sec image of the CDFS in the 10-40 keV band (the exposure in
the SDD camera is half of the total elapsed time to account for dead time). Red contours are Chandra
countrates,circlesidentifythehighlyobscured,infraredselectedsources.FortheChandrasourceswehave
computed the10-40keV fluxesextrapolating the2-10keVfluxesusingaspectralmodel consistentwith
theChandrahardnessratios.FortheIRselectedsourcesweconvertedtheir24µmfluxesusingtypicalIRto
X-rayunabsorbedfluxratios,α =0.8andN intherange1024−1025cm−2.
E H
soughtpopulationof CT AGN, thusdetecting tional biases. To these purposesthe following
directly most SMBH accretion luminosity in observationalstrategiescanbeenvisaged:
the Universe. Obtaining a complete census of
accreting SMBH through the cosmic epochs [1.] A spectral survey of local CT Seyfert
is a crucialstep to constrainnuclearaccretion 2 galaxies and moderately obscured QSOs
efficiency and feedbackson the host galaxies, previously discovered by BeppoSAX, XMM,
which are key ingredients toward the under- INTEGRAL, Swift and Suzaku. This may be
standing of galaxy formation and evolution. accompanied by a survey of infrared bright
The Simbol-X main contributionsin this field galaxies which have not shown strong X-ray
will be the discovery and the characterization emission below 10 keV, to search for highly
ofthesourcesmakingthemaincontributionto CT objects. These observationswill allow the
the peak of the CXB. Simbol-X will allow us precisemeasureoftheabsorbingcolumnden-
toevaluatetheluminosityfunctionofobscured sity,andthereforethedeterminationoftheN
H
AGN and its evolution, and to measure the distributionofalargesampleAGNsample,in-
fraction of obscured AGN as a function of cludingCTobjects(DellaCecaetal.thesepro-
luminosity and redshift with little observa- ceedings).Theywillalso allow usto putcon-
286 Fioreetal.:SciencewithSimbol-X
straintsonthephysicalstatusoftheabsorbing Main key issue in this field is the sharp
gasandonitscoveringfraction. image quality of the Simbol-X mirror (a
[2.]Deepobservationstosearchforhigher Point Spread Function, PSF, with half power
redshiftCTAGN. diameter, HPD< 20 arcsec, Pareschi et al.
theseproceedings).Otherimportantfactorsare
[3.] A serendipitous survey over a large
the relatively large field of view (∼ 12 ar-
areatosearchforhighluminosityCTAGN.
cmin diameter) and the low internal back-
[4.] A survey of candidate CT AGN
ground(see Laurentet al. these proceedings).
selected using their infrared emission and
Alreadymentionedsynergiesarewithmidand
Spitzer/Herschel surveys, see Feruglio et al.
far infrared space observatories like Spitzer,
theseproceedings.
HerschelandJWST.
These observations will quantify the ob-
scured AGN volume density as a function of
the Cosmic time and univocally confirm and 2.2.AGNmassiveoutflows:AGN
identifytheIRselectedCTAGNashardX-ray feedbackatwork
AGN,contributingtotheCXB.
In addition of obtaining a complete census of
SMBH, the other key observational ingredi-
2.1.1. TheCDFS:acasestudy ent to obtain a better understandingof galaxy
formation and evolution is the quantification
AsanexampleofwhatSimbol-Xcanachieve of the effects of AGN feedbackson their host
in the field extragalactic deep survey, Fig. 1 galaxies.
showsa simulationofa 1Msecobservationof AGNcaninteractwiththeinterstellarmat-
the Chandra Deep Field South area in the 10- ter of their host galaxies through at least two
40 keV band. We have included in the sim- main channels: radiation field and outflows.
ulation two source populations: 1) the X-ray Winds and jets, both non-relativistic and rel-
sources detected by Chandra below 10 keV; ativistic, are common in AGN, see Cappi et
2)thecandidateCTAGNselectedinthemid- al.andTavecchioetal.theseproceedings.The
infraredby Fioreetal. (2007).Forthe former two key parameters are the mass outflow rate
sources we extrapolated their flux in the 10- and the velocity structure of the outflow, be-
40 keV band using a spectral model consis- causetheygivetheenergyandthemomentum
tent with the Chandrahardnessratios. For the involved in the flow. Blue-shifted X-ray ab-
IRselectedCTAGNweconvertedtheir24µm sorptionlinesdetectedbyChandraandXMM
fluxes to X-ray unobscured fluxes using typi- indicate very high velocities, up to a fraction
caltemplates(Fioreetal.2007).Wethancom- of the speed of light, in a few sources. A
putedobserved10-40keVfluxesbyassuming comprehensive survey of absorption features
α =0.8andN intherange1024−1025cm−2. in sizeable AGN samples in different bins of
E H
Note as a few IR selected AGN are detected redshift and luminosity is however still lack-
alsobyChandra,butseveralotherscanbede- ing. Furthermore,the sensitivity of XMM de-
tectedonlybySimbol-Xabove10keV.Asin- creasessharplyabove9-10keV,hamperingthe
gle Simbol-X 1Msec observationwill be able possibility of detecting highvelocityoutflows
to resolve about 50% of the CXB in the 10- innearbyAGN.Simbol-Xwillbe2to5times
40 keV band.We will be able to probenearly moresensitivetoironabsorptionfeaturesthan
all kind of AGN, from unobscured to moder- XMM-Newton below 10 keV, and will open
ately obscuredto CT AGN.Sincethefraction thewindowabove10keV.Thiswillallowthe
ofCTAGNrisessteeplybelow10−14 ergcm−2 characterizationofoutflowsofanyvelocityin
s−1(10-40keVband)pushingthefluxlimitjust statisticalsamples.Thestudyofthevariability
below this value would strongly increase the of the absorptionlines will set a scale for the
chance to discover relativaly large samples of sizeandlocationoftheabsorbinggas,andfor
theseelusiveobjects(seeComastrietal.these its density, thus providing information on the
proceedingsforfurtherdetails). massinvolvedintheoutflow.
Fioreetal.:SciencewithSimbol-X 287
Keyissue inthistopicisthe highSimbol- to estimate the expected IC emission through
Xthroughputbetween7an20keV.Otherim- theirsynchrotronemission observedin the X-
portant issues are the good energy resolution rayrange.CombininghardX-rayandγ-rayob-
provided by the MPC detector and the broad servationsholdsthekeytouncoverpiondecay
band coverage, allowing a good constraint on emission.
thesourcecontinuum. Key issue in this field is a broad energy
band, extendingfrom ∼ 1 keV to ∼ 100 keV.
This will allow the separation of thermal and
2.3.Accelerationmechanismsin
non-thermalemissionandthemeasureofE .
cut
supernovaremnant
Extremely important here is to have a large
field of view,to coverlargefractionsofSNR.
Non-thermal emission was originally discov-
Obvious synergies are with TeV Cherenkov
eredbyASCAintheshell-likesupernovarem-
telescopesandwithGLASTandAgile.
nant(SNR)SN1006(Koyamaetal.1995).We
knowtodaythatmostoftheyoungSNRshow
non-thermalemissionatsomelevel.Theseare 3. Conclusions
the bestcandidatesites forthe accelerationof
Thanks to the emerging technology in X-ray
Cosmic Rays up to 1015 eV or even higher
mirrors (e.g. multilayer coating, see Pareschi
energies. Indeed, if the maximum energy of
etal.theseproceedings)andspacecraftforma-
electron (E ) is of this order, a strong syn-
max tionflying,Simbol-Xwillprovidealargecol-
chrotron emission is expected in the X-rays
lecting area (of the order of 100-1000 cm−2)
band,with a cut-offatanenergyE depend-
cut from a fraction of keV up to ∼ 80 keV, thus
ing on E and on the strength of the mag-
max overcomingthe “10keV limit” forhighaccu-
netic field. The magnetic field necessary for
racyimagingandspectroscopyof allpastand
theirscatteringmaybegeneratedorincreased
current X-ray observatories. This, together to
by the accelerated particles themselves (the
the good image quality (PSF HPD< 20 arc-
socalledstreaminginstability).Evidencesthat
sec,FWHM< 10arcsec),relativelylargefield
this effect is at work were claimed thanks to
of view (12 arcmin diameter), good detector
Chandra observations of the thickness of the
quantum efficiency, resolution and low inter-
X-rayrimsaroundthe SN shockin the Tycho
nalbackground,willallowbreakthroughstud-
SNR(Cassam-Chena¨ıetal.2007).Thebright-
iesonblackholephysicsandcensus,andpar-
nessprofileoftherimsisconsistentwithmag-
ticleaccelerationmechanisms.
neticfieldsafewhundredtimeslargerthanthe
ISM field. However, this interpretation of the Acknowledgements. Weacknowledgesupportfrom
Chandra data is not unique. The direct mea- ASI-INAF contracts I/023/05/0, I/088/06/0 and
sure of E willthenhelp understandingboth PRIN-MURgrant2006-02-5203
cut
whichisthemaximumenergyofelectronand
themechanismofdiffusiveshockacceleration References
in SNR shells (see Decourchelle et al. these
proceedings). Aharonian,F.A.etal.2006,A&A,449,223
Although we have plenty of evidences of Cassam-Chena¨ı, G., Hughes, J. P., Ballet, J.,
electronaccelerationincosmicsources,direct &Decourchelle,A.2007,ApJ,665,315
proofs of proton and ion acceleration are still Fiore, F. et al. 2007, ApJ in press, astro-
lacking. A direct signature of proton acceler- ph/0507.2864
ation is GeV-TeV emission due to pion de- Gilli,R.,Comastri,A.,&Hasinger,G.2007,
cay. HESS and MAGIC have revealed TeV A&A,
emissionfromafewsupernovaremnants(e.g. Koyama,K.etal.1995,Nature,378,255
Aharonian et al. 2006). A large fraction of LaMarleetal.2007,SPIE6686
the TeV photons are probably due to Inverse Marconi,A.etal.2004,MNRAS,351,169
Compton (IC) emission. To disentangle be- Setti,G.,Woltjer,L.,1979,A&A,76,L1
tween pion decay and IC emission one needs Setti,G.,Woltjer,L.,1989,A&A,224,L21