PoS(AASKA14)151 , 7 , 6 , 2 http://pos.sissa.it/ 9 , Gianni Bernardi 2 , 1 Joint Institute for VLBI in 10 3 Rhodes University, 6 , Mickäel Coriat 5 , 4 FÖMI Satellite Geodetic Observatory, 8 Max-Planck-Institut für Radioastronomie 10 , Matt Jarvis , Hans-Rainer Klöckner 3 6 , 9 University of the Western Cape, 5 Square Kilometre Array South Africa, 2 , Zsolt Paragi 2 , 1 , Ian Heywood ∗ 8 Hz). We also discuss how targets for pointed gravitational wave experiments (that cannot µ University of Oxford, 4 roger.deane [at] ast.uct.ac.za Speaker. be resolved by VLBI)which could can potentially be modulated be by found theof presence using direct of imaging the a at close-pair large-scale binary high radio-jet SMBH angulartiming system. arrays resolution; morphology, will The low-surface allow combination brightness the SKA radio-jet to tracers; tracevirial black and radius hole pulsar down binary to evolution from the separations sub-parsec ofwill level. a ensure galaxy This that large the dynamic SKA range plays in a binary leading SMBH role in separation this observational frontier. Galaxies and supermassive black holeshierarchical merging (SMBHs) and accretion. are Through this believed paradigm, to multipleto SMBH be evolve systems relatively common are through in expected the a Universe. process However,on to date of multiple there are SMBHs poor observational systems constraints influence with (« separations 1 comparable kpc). to Inwill this a make chapter, SMBH we leading gravitational discuss contributions how sphere towards deep understandinggalaxy of continuum how evolution. observations multiple In addition, with black these the hole observations SKA will systemsof provide impact constraints stochastic on gravitational and wave an background understanding detections in(nHz the - pulsar timing array sensitivity band ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. University of Cape Town, Harvard-Smithsonian Center for Astrophysics, c CSIRO Astronomy and Space Science, E-mail: 1 Europe, 7

Sandor Frey Advancing Astrophysics with the Square KilometreJune Array 8-13, 2014 Giardini Naxos, Sicily, Italy Roger Deane Multiple supermassive black hole systems: SKA’s future leading role PoS(AASKA14)151 we show 1 Roger Deane 1-100 kpc scales, , most notably by a ∼ ). In Fig. 1 2.1 2 we plot what could be considered as the strongest candidate binary SMBH systems. 1 We call a SMBH system dual if the separation of its components is larger than their radii of gravitational influence, The prevalence and evolution of multiple SMBH systems are predicted to have a broad range Binary supermassive black hole (SMBH) systems have long been predicted to be common in In Fig. 1 Hz frequencies (Wyithe & Loeb 2003, Sesana 2013). Numerical simulations of the large-scale µ and binary otherwise (see Merritt 2013). While there may be a degreetrates of how few subjectivity candidates on there which are, sources despitehas should our been appear expectations made in to in this the the contrary. figure, past Nonetheless,in it decade progress illus- the considering literature that at only three theIn systems time the in the this next first figure decade, SKA could large-scale science bepopulating surveys found case the with was the sub-kpc published SKA parameter (Carilli willsensitivity, space & make negligible Rawlings, in significant dust 2004). contributions particular, and towards driven gascretion attenuation by that at appears superior to GHz angular take frequencies, place resolution in and kpc-scale and the dual and enhanced triple nuclear AGN (see ac- Sec. of astrophysical impacts, which have important galaxy evolution implications. Gravitational per- the approximate angular resolution at 1-2al. GHz 2014, of these proceedings), SKA1-MID/SUR which and illustrates SKA-VLBI itswhen (see advantage considering to Paragi search the et for wide-area these surveys systems, the particularly SKA will perform in1.2 this frequency Impact band. on Galaxy Evolution the Universe (Begelman, Blandford &range Rees, of 1980). astrophysical impacts, Simulationsas including suggest they shallowing that eject the they stars inner via haveand density three-body a an profiles interactions broad increase during of in in-spiral galacticangular (e.g. bulge halos momentum star (e.g. Graham formation Blecha 2004, et and Merritt al.binary black 2011, 2006); van hole SMBHs Wassenhove et accretion are al. 2012). through expected Furthermore, disruption to sub-parsec of dominate cold the gas stochasticstructure formation gravitational of wave the background Universe reveal atet a al., nHz- process 2005). of Since hierarchical every galaxy galaxygalaxy is merging merger expected (e.g. should to include Springel host a a merger SMBHrange of (Kormendy of SMBHs. & predicted Richstone Despite binary 1995), this SMBH each forecastedRecently, impacts, ubiquity there our and has observations the been of broad a these resurgence systems in remain effort very to limited. find more dual/binary AGN Multiple supermassive black hole systems 1. Introduction hard X-ray census of the localarchives Universe for (Koss et double al. flat-spectrum 2012); sources ainfrared, (Burke-Spolaor large-scale adaptive-optics-assisted search 2011); followup through and VLBI imaging 2D data ofselected spectroscopic double-peaked from and SDSS narrow (e.g. near- emission Rosario line et AGN al.et 2010, al. 2011; McGurk 2011). et al. Thishowever, 2011; to has Fu date resulted et there al. in are 2011, an only Comerford et four increase strong al. in candidate the sub-kpc 2003, number binary/dual Rodriguez of AGNdiscuss et systems dual how al. (Komossa the AGN SKA on 2006, will Fabbiano take et a leading al. role 2011, in1.1 exploring Deane this Observational et observational status al. frontier. 2014). In this chapter we PoS(AASKA14)151 × 4 ∼ s r CDM cos- Roger Deane Λ radio-jet morphology GW GW transients? mergers via EM/ direct imaging pulsar timing arrays 100 parsec down to the sub-pc gravi- ∼ 3 ´ c 2005). Therefore, this appears to be an important consideration SKA1-MID/SUR SKA-VLBI SKA-VLBI binary SMBHs can decrease from

6 decades of binary SMBH orbital separation and are elaborated on later in this & M Sgr A* Schwarzschild radius 8 10 ∼ Sample of the strongest dual/binary AGN candidates as revealed by direct imaging at X-ray pc). Source names can be found in Deane et al. (2014) 7 − Figure 1: (squares), optical/infrared (triangles) andspatially-unresolved radio candidates (stars) based wavelengths. on their Thecurve. double-peaked two broad emission sub-pc The lines triangles grey and denotebe and quasi-periodic possible two light blue with curves SKA1-MID/SUR indicate andthe SKA-VLBI. the SKA The spatial labels will resolution on explore the (for right frequency provide range a 1-2 rough sketch GHz) on that how will contribution. The projected separation10 lower limit is set to the Schwarzschild radius of Sgr A* ( turbations from binary systems aremation expected rates, to and increase hence both impact SMBHMcConnell the accretion & well-correlated and Ma nuclear bulge 2013). black star hole for- Additionalof to scatter recoiling spheroid in mass black this ratio holes relation (e.g. (e.g. mayseparations of result Blecha from et the potential al.tational ejection 2011). radiation dominated regime Hydrodynamical on simulations a timescale suggestWassenhove of et a that al. few 2012). the Myr As if the sufficient orbital gasto separation is eject decreases, present of (e.g. the binary order van SMBH 1-4 system(Merritt times is 2006). their predicted combined This mass mass from isgalaxies the sufficient (Merritt galaxy/bulge to & via flatten Milosavljevi three-body the interactions innerin density the slope, attempts as to is reconcile measured theoretically in motivated nearby central matter density cusps in a Multiple supermassive black hole systems mology versus the observationallyMashchenko supported et cores al. which have 2006). flat The central anisotropic density gravitational profiles wave (e.g. emission from binary coalescence PoS(AASKA14)151 ´ c 95, . 0 − 9 . 0 Hz, Sesana Roger Deane µ ∼ e 1-10 ∼ 1 parsec (Merritt & Milosavljevi ∼ 4 7 at formation, the expected characteristic strain at 1 nHz is . 0 ∼ 0 e 5, while the effect is minimal at higher frequencies ( ∼ While binary SMBHs are expected to dominate the low-frequency stochastic gravitational The combination of depth, area and angular resolution of SKA continuum surveys will result wave background, very little is knownsuch about as the the properties typical of binary low in-spiralkpc separation rate, scales. binaries eccentricity themselves, evolution These and are environmentaltational important coupling wave to at spectral sub- constrain normalization as and shape. theypredictions assume directly Indeed, that determine stochastic nature gravitational the solves wave low-frequencytimate the background gravi- that so-called binaries ‘last take parsec of problem’. orderejection This a of arises Hubble most from time the to matter merge es- within via binary gravitational radiation, orbital following separations the of Multiple supermassive black hole systems is predicted to result infrom large the recoil host velocities and galaxy shouldstrong centre individual enable (e.g. candidates the (e.g. measurement Madau Civano of ettical & AGN al. galaxies Quataert offset suggests 2010), this a 2004). offset detailed (where analysis measured) However,rates of is (Lena apart 14 not et nearby as from al. large cored a as 2014). ellip- predicted number for of plausible merger 1.3 Linking with pulsar timing array experiments 2005). Statistics from a large samplethe of binaries question will of measure stalled the in-spiral binaries.the rate sophisticated and However, directly simulations eccentricity address that evolution have will developed inet require the al. further recent 2011, successes past Kulkarni (e.g. in et Mayer al.tions et 2012, of al. van 2007, the Wassenhove Blecha et molecular al. gas.have 2012) an Stellar as initial well scattering eccentricity as driven detailed of modelssuppressed ALMA predict by observa- a that factor if of typical binary2013, SMBHs Ravi et al. 2014).eccentricity Moreover, (although, the perhaps presence not of to significanteccentric the gas systems extremely masses are high appears predicted to values toholes in increase reach emit the the the sharp stellar pericentre spikes of driven their of case). increasingly gravitational eccentric Such wave orbit. radiation For eccentricities as of the black in an unprecedented view of the faint radio Universe, and by extension, multiple SMBH systems. the characteristic strain will increaseThis by implies that 2-3 the orders highly eccentric of innerular magnitude binaries (e.g. for that result Hoffman a in & constant simulated Loeb tripleexperiments semi-major 2007) systems (for axis. in may a partic- result small in fraction detectableitational of sources wave their for hotspots, orbit). pointed it While gravitational isspectrum wave this likely may at to be nHz decrease promising the frequencies forple amplitude by detecting of of significant grav- the SKA-discovered factors. stochastic binaries; gravitational the Therefore,molecular wave gas continued the dynamics progress at combination high on of angular sophisticatedcharacteristic a resolution binary simulations; with large in-spiral ALMA as evolution sam- are and well important resultant in nHz as Spolaor understanding gravitational (2013) wave the for spectrum. an See excellent Burke- reviewby on linking the pulsar multi-messenger timing astrophysics array that results will be with ushered electromagnetic in probes. 2. Motivation: why the SKA will lead PoS(AASKA14)151 suggests 3 Roger Deane wide-area SKA surveys will undoubt- 1 − ) . Following this (admittedly simplistic, yet 2 5 Jy beam µ 1 . Projected separations of candidate triple active galactic nuclei. The axes denote the lowest and Despite this increased discovery efficiency that would be enabled by the SKA, Fig. It has been shown that galaxy-galaxy interactions are extremely efficient at triggering both lowest separations between AGN. The solid black line indicates a ratio of unity. The dashed lines isolate nd edly enable the efficient discovery of a large population of sub-kpc binary/dual AGN. plausible) argument would lead uscreasing to orbital expect separation, the provided efficiency sufficient of angularthe resolution binary and sub-arcsecond SMBHs survey angular to sensitivity. increase resolution If correct, with and de- that direct imaging is unlikely toexperiments yield in a the large pulsar number timing of candidates arraylarge-scale radio-jet for band. morphology pointed However, may gravitational as provide wave we annot alternative discuss method in resolvable to the at discover following close-pair VLBI section, binaries resolution.so the the We lower note frequency that limitfrequency the limit in SKA results the is in pulsar roughly likely a timing to factor band be of will a 8 larger increase 50+ cosmological in year volume time. project ‘surveyed’, so and a Halving future the lower Figure 2: the sub-10kpc systems, whichcorrespond is to roughly the the total effectiveresolution limits stellar integrated a fair radius radio AGN radio of luminosity luminositywithin an comparison. of triple Nonetheless, elliptical the systems, the galaxy. plot particularly AGN supports in enhanced plusquasar The the accretion systems) the sub-10kpc colours indicate systems. host upper The radio galaxy, twoDeane luminosity since black et limits al. circled low from (2014), points archival angular with (which observations. references are Figure therein. triple reproduced from However, there are a number oftheir attributes detailed of study with these the hitherto SKA. exotic systems that will2.1 further enable Enhanced radio-jet triggering in dual and triple AGN nuclear star formation (e.g. Scudder etet al. al. 2012; Patton 2011), et and al. thatThese 2013) results these and are trends AGN consistent activity continue (e.g. with wellhove Ellison predictions into et from the al. hydrodynamical post-merger 2012, simulations phase Blecha (e.g. et (Ellisonprevalent al. amongst van et binary 2011) Wassen- al. and and triple this 2013). SMBHs implies (see that Fig. radio-jet triggering should become more 2 Multiple supermassive black hole systems PoS(AASKA14)151 for all 140 parsec Roger Deane 1 kpc ∼ 1 parsec) on a . , indicating the < 4 binary SMBHs can

M 8 10 ∼ 1 kpc) binary candidates via the large- 10 Myr), suggesting that these helical ∼ << pulsar timing array sensitivity pulsar timing and circular orbits. This plot demonstrates that even 6

M with an updated lower frequency limit and come to a 9 3 , this may not be necessary to find so-called gravitational wave 2.2 100 parsec down to the gravitational radiation dominated regime ( ∼ This plot shows the derived maximum gravitational wave frequency from a binary SMBH system 1 kpc) binary SMBH could in principle be discovered using the rotationally-symmetric , it may be able to select excellent close-pair ( << Even though SKA1-MID/SUR is only likely to detect dual AGN separations of redshifts scale radio-jet morphology, particularly given the unprecedentedA low surface number brightness of sensitivity. studiesBegelman have et investigated al. the 1980, Kaastra binary &binary SMBH Roos SMBH 1992). imprint in Deane on et SDSS radio-jet al. J1502+1115"S"-shaped (2014) using morphology radio show VLBI evidence (e.g. emission of observations, centered a on as thepair well VLBI ( as flat-spectrum cores. rotationally-symmetric This suggestsmodulation that imprinted the close- onto the radioresolved jets. binary candidates The (0402+379 radio and jetsbinary SDSS orbits for 1502+1115) may the are have two shown a lowest intion, significant separation, Fig. influence hydrodynamical spatially- on simulations their suggest morphology.decrease As that from discussed the in separations the of introduc- timescale of a few Myr, particularlyThis if is sufficient comparable gas to is presentrelics the (e.g. may typical provide van lifetime arcsecond-scale Wassenhove of et signpostsbe al. radio of resolvable 2012). jets using close-pair VLBI. ( binaries, If some that is of the which case, this may may not be even a way to find gravitational wave ‘hotspots’ hotspots. generation of astronomers may re-plot Fig. different conclusion. 2.2 Radio-jet morphology as a proxy Figure 3: that can be spatially-resolvedseparation by equal SKA1-MID/SUR to and 2 PSF SKA-VLBI. FWHM, We masses assume of binaries 10 with an angular Multiple supermassive black hole systems high sensitivity VLBI isarrays, unlikely however, to as discover discussed sources in in Sec. the frequency band detectable by pulsar timing PoS(AASKA14)151 -arcsecond Point-source Roger Deane µ 40 < JVLA 1.4 GHz map of Right panel: . The grey ellipse shows the JVLA 5 GHz residuals σ 2 ± 1-3 decades); and by the required ∼ Left panel: 200 km) are required to map the substantial ∼ ) to highlight the complex, potentially helical- 1 − SDSS J1502+1115 7 JVLA 1.4 GHz 7 parsec) binary SMBH system known. The colour scale is clipped ∼ ) and increasing/decreasing in steps of noise = 0.21 mJy beam σ 4 σ ± ( (1 1 1 − Hz) gravitational waves, limited roughly by the length of time astronomers − µ 0402+379 Jy beam µ 60 1 binary SMBH that generates gravitational waves in the pulsar timing array band. ± . The above figures show the low surface brightness emission associated with the two lowest sepa- 0 . As described in Janssen et al. (2014, these proceedings), detection of the stochastic gravita- z time to achieve sufficient timing residuals signal-to-noise (of the full network of pulsars) at the high tional wave background is likelylow-frequency by (nHz- the end ofhave been the accurately decade. timing millisecond pulsars Pulsar at timing the low arrays end are ( sensitive to 1.4 GHz jet emission at higher resolution. Figure from Deane et al. (in prep.). 2.3 Binary SMBH insights from pulsar timing arrays like large-scale radio-jet emission centered(shown on by the black VLBI ellipse cores inthe centre). which innermost, are VLBI few-parsec within observations scale the resolve jets. out 1.4 Intermediate all GHz baselines emission PSF ( but FWHM the twosubtracted radio JVLA cores 5 and GHzVLBI residuals components revealing (within rotationally the symmetric red "S"-shapedSMBH rectangle). radio in emission There the also system centred appear to on starting to the at be west small-scale (J1502P, jets redJVLA centred cross). 5 on GHz Over-plotted the PSF, are third while the theet JVLA white al. (2014). ellipse 5 shows GHz the contours 5 (black) GHz EVN PSF. Modified figure to Fig.where 1c a in nearby Deane system with sufficientlygravitational high wave mass background black (e.g. holes Sesana may 2014,useful stand Simon in out et above understanding al. the 2014). electromagnetic stochastic radio-jet Such counterparts morphology targets of would may be gravitational be very wave alarly sources. promising given the tool expected in Therefore, SKA binaryto imaging SMBHs ‘static’ fidelity searches jets and (negligible of sensitivity variation the at overparsec-scale future, the VLBI-scales. jets timescale particu- (e.g. of The Agudo years), above et however, al. applies jet monitoring 2012) variations position is of an angles additional may probe, be particularlytechniques measured given may the identify at promising cadence high targets that for angular millimetreangular resolution. VLBI observations resolution with These (e.g. two Doeleman radio etof jet al., a 2008). morphology This would in principle enable the direct imaging Figure 4: ration binary SMBH candidates (0402+379 andmorphology J1502+1115). This may is reveal to illustrate the how arcsec-scale presence radio-jet of low separation binaries. Multiple supermassive black hole systems 0402+379, the lowest separationbetween ( 2-20 mJy beam PoS(AASKA14)151 6) orders of Roger Deane & per square degree at 10 kpc) down to the 4 ∼ 10 ∼ 200 km) and VLBI capability for > nHz frequency, environment coupling ∼ 8 Jy sources. Here SKA-VLBI refers to combining µ 50 & ). Therefore, the spectral shape of the nHz detected stochastic 1.3 ), we expect several orders of magnitude increase in the number of known binary illustrates, very few of the expected population of low separation binary SMBHs have σ 5 1 ). >

M 2 weeks). This frequency range is thought to be dominated by binary SMBHs and therefore, 7 ∼ As Fig. Assuming the above indicative estimate on the sub-kpc AGN prevalence, we should in prin- What sets the SKA apart from the major multi-wavelength facilities of the future is the dy- While pulsar timing arrays, radio-jet morphology and direct imaging of flat-spectrum sources For binary separations and masses that correspond to 10 & been identified. Extrapolations to theunconstrained. number However, of theoretical systems expectations the suggest SKA thathost will 0.1-1 binary detect percent SMBHs, are of at therefore galactic highly least halos& at may Loeb intermediate 2012). to Given high thedensity redshift enhanced of AGN (e.g. radio triggering AGN Volonteri at et to low be al. separation, detected 2003, as with well Kulkarni the as SKA the continuum high surveysSMBHs. number ( We make no attempt tomessage extrapolate from is small that number both statistics, sincerobust phases the statistics of overwhelming of the sub-kpc SKA binary/dualconstraints will AGN on open the to binary up be SMBH a performed coalescence ratemulti-wavelength massive for and tracers discovery the correlations to with be space first their explored. time. and host This galaxies will revolutionaryis This via view allow critically other of will binary dependent enable SMBHs on in the high Universe sensitivity on long baselines ( ciple be able tosensitivity. detect This simple a extrapolation therefore large predicts fraction that SKA1-MID/SUR of will make those of with order a radio counterparts with SKA1-MID/SUR magnitude when considering the virialsub-pc separations radius of of binaries a in the large gravitational elliptical radiation galaxy dominated zone. ( 3. Predictions for the SKA 1.4 GHz; high angular resolution followup ofexisting the VLBI networks with the SKA in both phases. 3.1 SKA1 impact namic range of binary black hole separation that it will probe. This will be several ( gravitational wave background must bedetected reconciled AGN fraction with at the sub-kpc merger scales.E-ELT, rate as Measurements well and of as stellar constraints ALMA-derived core of molecular deficits radio- gasfor with kinematics the SKA-discovered will binaries. JWST be and Variability critical and ancillary transientbetween data events products LSST may and indicate SKA mergers and isproceedings, a also and synergy references expected therein). in this particular pursuit (see Fender et al. 2014, these are very different probes of binary SMBHs,Each these should approaches in will have principle to contribute form to a an consistent overall picture. understanding of the binary in-spiral evolution. Multiple supermassive black hole systems end ( such a detection will prove the existence( of a population of sub-pc separation systems of high mass is thought to be particularlyboth important of in which determining have the significantbackground in-spiral (as effects rate discussed on in and Sec. the orbital spectral eccentricity shape – of the stochastic gravitational wave PoS(AASKA14)151 ) 2 ) may 2 ) and so 10 deg 1 & Roger Deane , and circular 10 deg

M >> 9 pos 10 σ × 200 km) for the majority > 2 decrease in the number of dual √ will SKA2-VLBI resolve SMBH binaries that we have shown the maximum gravitational wave 9 3 In Fig. 06 (Rodriguez et al. 2006). This increased sample size at low separation . 0 ∼ z 1 kpc). The preliminary evidence that radio-jet triggering is enhanced in dual << 20 pc at all redshifts and map associated jets with high fidelity. The wide-area ( ∼ SKA1 is also expected to participate in VLBI sessions with existing networks (e.g. European SKA2 will naturally lead to a significant increase in the sample of known parsec-scale binary This suggests that SKA2 (particularly when combined with existing VLBI arrays) will com- This contribution discusses how the SKA will constrain the black hole merger rate at low frequency of a binary that has a 10 milliarcsecond separation, mass of 2 and African VLBI Networks; Paragifore et al. already 2014, provide these the proceedings).angular opportunity SKA1-MID/SUR resolution to will for there- a perform few high weeks per sensitivity year. observations at3.2 milli-arcsecond SKA2 impact AGN, through the dramatic increase in sensitivity on longer baselines ( will become a dominant driver ofwill this only field. impact the A science 50 output percentAGN through detected, decrease the assuming in rough a SKA1-MID/SUR factor comparable sensitivity of baseline distribution. of the available telescope observing time. SKA2-VLBItions of will be able to resolve binaries with separa- pletely revolutionize this field oncerameter again space (following and SKA1-MID/SUR) bridge in pulsar theuum timing low surveys. array separation results This pa- with naturally what leads is to gleaned the from question: mas-scale contin- will be key in bridgingfrom the black pulsar hole timing coalescence arrays. ratespectral and The shape environment latter to coupling be requires with measured the the fromis pulsar stochastic results complete. timing gravitational arrays, In wave which addition, background may these be surveys nHz of possible will AGN by provide positions, the a time large enabling sample SKA2 a ofor statistical high the precision study presence measurements of of the binary SMBHs offset (e.g. AGN predicted Orosz & by Frey gravitational 2013, recoil Paragi et al., these proceedings). can be detected by pulsar timing arrays? Multiple supermassive black hole systems few to a few hundred dual AGN detectionsin per size, square degree. but This also will in beSKA1-MID/SUR a selection will unique since be sample not able it only to will probe be these unbiased scales by (1-100 dust kpc) and at all gas redshifts obscuration. (see Fig. Furthermore, mas-resolution surveys will open aof completely systems new of parameter comparable space and and lowerseparation discover separation binary a that at large the number current record holder: 0402+379, the 7 pc orbit. This demonstrates that even SKA2-VLBIarray is sensitivity unlikely frequency to band discover at binaries 1-2 in GHz.veys the and This pulsar searching places timing greater for emphasis low on separation higher (sub-pc)We frequency binaries note sur- using the the large-scale exciting radio-jet possibility morphology. timing that array experiments, the however, SKA the associated may positional discover uncertainties such ( systems purely through pulsar separations ( prohibit electromagnetic counterpart determination. 4. Summary and triple SMBH systems; negligible dust and gas attenuation at GHz frequencies; and unmatched PoS(AASKA14)151 Roger Deane , PoS(AASKA14)037 , PoS(AASKA14)051 10 ´ c Ž., et al., 2007, ApJ, 656, 680 Advancing Astrophysics with the Square Kilometre Array 0.0pt Advancing Astrophysics with the Square Kilometre Array SKA", in proc. Kaastra J. 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