On why the Iron K-shell absorption in AGN is not a signature of the local Warm/Hot Intergalactic Medium

0.19 MB·English

by  James Reeves

Mon.Not.R.Astron.Soc.000,1–??(2003) Printed2February2008 (MNLATEXstylefilev2.2)
On why the Iron K-shell absorption in AGN is not a signature of the
local Warm/Hot Intergalactic Medium
1 2 3 4 5
James Reeves , Chris Done , Ken Pounds , Yuichi Terashima , Kiyoshi Hayashida
8
5 5 3
0 Naohisa Anabuki , Masahiro Uchino , Martin Turner
0 1AstrophysicsGroup,SchoolofPhysicalandGeographicalSciences,KeeleUniversity,Keele,Staffordshire,ST58EH,UK.
2 2DepartmentofPhysics,UniversityofDurham,SouthRoad,DurhamDH13LE,UK
n 3DepartmentofPhysicsandAstronomy,UniversityofLeicester,UniversityRoad,Leicester,LE17RH,UK.
a 4DepartmentofPhysics,EhimeUniversity,Matsuyama790-8577,Japan
J 5DepartmentofEarthandSpaceScience,OsakaUniversity,Toyonaka,Osaka560-0043,Japan

0
1
SubmittedtoMNRAS

]
h
p
ABSTRACT
-
Wepresentacomparisonbetweenthe2001XMM-Newtonand2005Suzakuobservationsof
o
r the quasar, PG1211+143 at z = 0.0809. Variability is observed in the 7 keV iron K-shell
t absorptionline(at7.6keV in thequasarframe),whichissignificantlyweakerin 2005than
s
a duringthe 2001 XMM-Newtonobservation.From a recombinationtimescale of < 4 years,
[ thisimpliesanabsorberdensityn>4×103cm−3,whiletheabsorbercolumnis5×1022 <

1 NH < 1×1024cm−2. Thusthesizescale ofthe absorberis too compact(pc scale) andthe
surface brightness of the dense gas too high (by 9-10 orders of magnitude) to arise from
v
7 localhotgas, such as the localbubble,groupor Warm/Hot IntergalacticMedium(WHIM),
8 as suggested by McKernan et al. (2004, 2005).Instead the iron K-shell absorptionmust be
5 associatedwithanAGNoutflowwithmildlyrelativisticvelocities.Finallyweshowthatthe
1 theassociationoftheabsorptioninPG1211+143withlocalhotgasissimplyacoincidence,
. the comparisonbetweenthe recession andiron K absorberoutflowvelocitiesin otherAGN
1
0 doesnotrevealaonetoonekinematiccorrelation.
8
Keywords: accretion,accretiondiscs–atomicprocesses–X-rays:galaxies
0
:
v
i
X
1 INTRODUCTION rest.Foranysingleobjecttheapproximatematchbetweenthepu-
r
a tativeblueshiftedoutflowvelocityandthegalaxyredshiftcouldbe
ThecosmologicalrequirementthathalfthebaryonsintheUniverse coincidental, but McKernan et al (2004; 2005) pointed out three
areinawarm/hotintergalacticmedium(WHIM)hasmotivatedUV AGNshowingthistrend,withredshiftsspanning∼ 0.008−0.15
andX–rayabsorptionlinestudiestodetectthisotherwiseinvisible (MCG–6–30–15, PG1211+143 and PDS 456). However, the de-
gas,usingabsorptionagainstabrightAGNtoprobethelineofsight rivedcolumnsofN ∼ 1023 cm−2 arehighevenforanintrinsic
H
material (Bregman 2007). However, most AGN (except blazars) AGNoutflow(Poundsetal2003,hereafterP03;Reevesetal2003).
haveintrinsiccolumnsofwarmabsorbinggasintheirnuclei,and Iftheseareinsteadoflocaloriginthenitrequiresatremendously
thefactthatthisisgenerallyconnectedtoanuclearoutflow(Blustin significantchangetoourunderstanding oftheGalactichaloenvi-
etal2005)complicatesseparatingthisintrinsicabsorptionfromex- ronment(McKernanetal2004;2005).
trinsicline–of–sightmaterialusingvelocityinformation.Nonethe- HereweusenewSuzakudatatoshowthatthehighlyionised
less, various studies have looked for absorption lines (predomi- FeabsorptioninPG1211+143isvariableonatimescaleofyears.
nantly OVII/VIII) as signatures of the WHIM, though all current ThisconclusivelydemonstratesthatitisintrinsictotheAGN,and
detections are more likely to be associated with material in our notassociatedwithourGalaxyorLocalGroup.Wecollaterecent
Galactic halo or Local Group (Bregman & Lloyd–Jones 2007). resultstoshowthatthisisalsothecaseformostotherAGNwith
Thesehavevelocitieswithinafewhundredkm/softhelocalstan- strongFeK absorption lines, showing that powerful outflowsare
dard of rest, and indicate columns of OVII/VIII > 1016 cm−2, associatedwithluminousaccretionflows.
equivalenttoHydrogencolumnsofN ∼1019cm−2.
H
Muchmorecontroversialwasthepotentialassociationofsub-
stantially higher columns of gas to such local material. McK-
2 THEIONISEDABSORPTIONINPG1211+143
ernan et al (2004; 2005) noticed that several AGN with strong
He– or H–like Fe absorption features had these lines at energies ChandraandXMM–Newtongratingsgavethefirsthighresolution
which were approximately consistent with the local standard of X–ray spectra of the warm absorbers in AGN (e.g. Blustin et al
2 J. Reeves et al.
2005, McKernan, Yaqoob & Reynolds 2007). However, only the
ChandraHETGScancovertheFeKregion,andthishasverysmall
effective area. Thus most of the information on these absorption
loinneXsMarMef-rNomewtthoen.laTrgheeseeffsehcotiwveedartehaa,tmsoomdeeraptoewreesrofulultAioGnNCChDav’es eV)−1 0−3
k 1
strongabsorptionlinesat7keV(observedframe)associatedwith s −1 2×
largecolumnsofhighlyionisediron(PG1211+143:P03;Pounds m −2
&Page2006,hereafterPP06;PDS456:Reevesetal2003). s c
TheresultsonPG1211+143,ataredshiftofz=0.0809,were on
ot
initiallycontroversial.P03claimedthatthedipinthespectrumat h
P
l∼ike7FkeeVKwαa(s6a.9n7abkseoVr,ptliaobn–flriname,ew).hGicihvethneythienistoiaulrlcyeidreednstihfiieftdtHhi–s keV (2 10−3
requiresanoutflowvelocityof∼24,000km/si.e.0.08cassuming
anoriginintheAGN.Other,weakerbutstillsignificantabsorption
lines in the CCD spectra at 2.68 and 1.47 keV could also be in-
0.5 1 2 5 10
terpretedasarisingfrommaterialwiththesameoutflowvelocityif Energy (keV)
thesearefromH–likeSandMgKα,respectively.(P03,PP06).The
higherresolutionRGSinstrumentalsoshowslinesfromlowerZel- Figure1.Fluxedspectrafromthe2001XMM-Newton(redcrosses),2004
ementsatlowenergies.P03identifiedthesewithtransitionswhich XMM-Newton (green circles) and 2005 Suzaku (black crosses) observa-
required similarly high velocities as the high ionisation material, tionsofPG1211+143,comparedtoaΓ = 2continuum.Thespectraare
plottedintheobservedframe(atz = 0).Thedownturnatlowerenergies
whileKaspi&Behar(2006)useddifferentidentificationstoobtain
isduetotheGalacticcolumnof2.8×1020cm−2.StrongsoftX-rayex-
alowervelocityoutflowsolutionfortheselines.
cessesbelow1keVareobservedinall3spectra,whicharemostprominent
Nonetheless, theoriginof theRGSfeaturesisnot themajor
inthe2001and2005observations.Thedeepabsorptionfeatureat7keVis
issue. Only the CCD’son XMM-Newton can show the existence
detectedinthe2001XMM-Newtonobservation,butnotinthe2004XMM-
ofmaterialwhichissohighlyionisedthatheavyelements(S,Mg, Newtonand2005Suzakuobservations.Thespectrahavebeenre-binnedby
Fe)arepredominantlyHe–orH–like.Surprisingly,Kaspi&Behar afactor×2forclarity.
(2006) identifiedtheSandMgK-shelllineswithweakerHe-like
Kβlines(withlittlevelocityoffset),insteadoftheblue-shiftedH-
likeKαtransitions,whichbegsthequestionastowhythecorre- responsefiles(rmfs)andancillaryresponsefiles(arfs)weregener-
spondingstrongerKαlinesarenotseen.Theseauthorsalsomodel atedusingthe XISRMFGENand XISSIMARFGENscriptsincluding
theFeKabsorptioninthe2001XMM-Newtondatawithanedge correctionforthehydrocarboncontaminationontheopticalblock-
at7.27keV(restframe)ofopticaldepthτ ∼ 0.5,corresponding ingfilter(Ishisakietal.2007).AnetXISsourceexposureof97.5
toalargecolumn(NH > 1023cm−2)ofverylowionisationstate ks was obtained for each of the 4 XIS chips. The 3 front illumi-
matter (Fe VII/VIII);this should have substantial low energy ab- natedXISchips(XIS0,2,3)wereusedinthispaper,astheyhave
sorptionwhichisclearlynotpresentinthedata.Asweshowbelow, thegreatestsensitivityatironK.Thesechipswerefoundtoproduce
accountingforanylowionisationabsorption(viapartialcovering) consistentspectrawithinthestatisticalerrors,sothespectraandre-
inaselfconsistentphotoionisationmodeldoesnotremovethere- sponseswerecombinedtomaximisesignaltonoise.Thenetsource
quirementfortheblue-shiftedhighlyionisedironKabsorber. countrateforthe3XIScombinedwas0.7984±0.003countss−1,
Theonlyself–consistentoptionforthefeaturesaround7keV withbackgroundonly3%ofthesourcerate.TheXISsourcespec-
intheXMM-NewtondataisKαabsorptionlinesfromH–orHe– trumwasbinnedtoaminimumof100countsperbintoenablethe
like iron. This requires a large blueshift (0.08c or 0.14c respec- useofχ2minimisation.Errorsarequotedto90%confidencefor1
tively)iftheabsorptionisintrinsictotheAGN,withtheimplica- parameter(i.e.∆χ2 =2.7).
tionbeingthatthekineticenergyassociatedwiththismaterialcan
dominatetheAGNenergetics(Pounds&Reeves2007).
3.2 XMM-NewtonAnalysis
XMM-NewtonobservedPG1211+143twice,on2001June15for
3 DATAREDUCTION 53ksand2004June21for57ksbutthissecondexposurewasaf-
fectedbyhigh particlebackground, resultinginonly 25ksof us-
3.1 SuzakuAnalysis abledata.TheEPIC-pnspectrausedinthispaperareidenticalto
thosedescribedinPP06andPounds&Reeves(2007),whichwere
PG1211+143 wasobserved bySuzaku (Mitsuda etal. 2007) be-
processedusingtheXMM-NewtonSASv6.5software.TheEPIC-
tween24-27November 2005.Inthispaper wediscussdatataken
MOSspectraareconsistentwiththeEPIC-pn,withthesame7keV
withthe4XIS(X-rayImagingSpectrometer;Koyamaetal.2007)
absorptionfeaturepresentintheironKband,asdiscussedbyPP06.
CCDs.Eventsfilesfromofficialversion2.0oftheSuzakupipeline
processingwereused.ThePG1211+143Suzakueventfileswere
screenedusingidenticalcriteriatothosedescribedinReevesetal.
(2007)fortheSuzakuobservationofMCG-5-23-16.
4 ACOMPARISONBETWEENSUZAKUAND
Subsequently source spectra from the XIS CCDs were ex-
XMM-NEWTONOBSERVATIONS
tractedfromcircularregionsof2′ radiuscentredonthesource,in
the off-axis HXD nominal pointing position. Background spectra The 2001–2005 spectra from 0.4-10 keV are plotted in Figure 1,
wereextractedfrom4′circlesoffsetfromthesourceregion,avoid- relative to a Γ = 2 power-law continuum. The CCD’s on both
ingthecalibration sourceson thecorners of theCCDchips. XIS XMM-NewtonandSuzakuhavesimilarresponsessothedataare
IronK-shellabsorptionisnot fromtheWHIM 3
directlycomparable.AGalacticcolumnof2.8×1020cm−2isin-
cludedinallthespectralfits.Fromthespectra,itisclearthatthere
islittlechangeintheoverallspectralshapeornormalisation.All3 5
observationsshowastrongsoftX-rayexcessbelow1keV,though 1.
it is marginally more prominent during the 2001 XMM-Newton
and2005 Suzaku observations. However thedeep ironKabsorp-
tionfeatureobservedat7keVin2001(Poundsetal.2003)whichis
o
readilyapparentevenonthisbroadbandspectralplot,isnotpresent ati
R
atthesamestrengthineitherthe2004or2005 data.Thisfeature 1
hasvariedsignificantly,rulingoutalocaloriginfortheabsorber.
To quantify this, we use only the 2001 XMM-Newton and
2005 Suzakuobservations asthesehavethebest signal–to–noise.
We fit the datasets simultaneously over the 2–10keV bandpass
toavoidthecomplexity associated withthe soft X–rayexcess. A
5
power law withfixedGalacticabsorption gives averysimilarin- 0. 5 6 7 8
dexbetweenthetwodatasetsasthecontinuaareverysimilar(see Observed Energy (keV)
Fig1),buttheoverallfitispoor(χ2/dof =374/154and369/249
fortheXMM-NewtonandSuzakudata,respectively).Fig.2shows Figure2.Data/ModelratioresidualsatironKtoasimplepower-lawfitto
theratioofthedatatothemodelforthisfit,whereaswellasthe the2–10keVspectrumofPG1211+143.The2001XMM-Newtonobser-
obvious absorption feature in the XMM-Newton data, it is clear vationisinred,2005Suzakuinblack.Theabsorptionfeatureat7keV(7.6
thatbothspectrahaveironemissionat∼6.5keV.AddingaGaus- keVQSOrestframe)isapparentintheXMM-Newtondata,butnotinthe
Suzakuobservations,showingthattheironKabsorptionhasvariedover4
sian line (with intrinsic width constrained to be equal across the
years.BroadironKαemissionispresentinallobservationsat6keV(6.5
two datasets) gives a line energy and equivalent width consistent
keVrestframe),aswellascurvature at4-6keV whichcanbemodelled
between the two datasets, at 6.5 keV and 250 eV respectively.
eitherbyaverybroad,redshiftedlineorbycontinuumcomplexity.
The intrinsic line width is resolved with a FWHM velocity of
25000kms−1i.e.typicalofradii ∼< 100R fromtheblackhole.
g
However, there is still significant curvature in the spectrum, ingfractionismuchlargerintheXMM-Newtonspectrum(80per
asshownbythepoorcombinedχ2 = 582/398.Thiscanbephe- centcomparedto40percent),showingthatthespectralcurvature
ν
nomenologically modelled by an additional Gaussian line, again ismore evident in these data. We use these two different models
with intrinsic width tied between the two datasets. This gives an (hereaftertermedGauandPcfxi,respectively)toassesstherobust-
acceptable fit,withχ2 = 441.3/393, for averybroad line, with ness of the change in the narrow absorption features to different
anintrinsicwidthof1.1±0.2keV.Thelineenergyisconsistent continuumplacement. Notethepartialcoveringmodel isinsensi-
betweenthetwodatasetsat∼ 4.4keVbutitsequivalentwidthis tive to the turbulence assumed, as its effect from 2–10keV is to
muchlargerintheXMM-NewtondatathanintheSuzakudata,at reproducethecontinuumcurvatureinthespectrum, frombound–
∼800eVcomparedto∼290eV(seeTable1),showingthatthere freeabsorptionsuchastheironK-shelledge.
is more curvature in the XMM-Newton data. Since it is also the Fig3showstheχ2residualstothepower-law,GauandPcfxi
XMM-Newton data which show the line absorption feature, it is models, respectively. The absorption line is still present in the
possiblethat thiscurvature isassociatedwiththeabsorber, rather XMM-Newtondata,evenagainstthePcfximodelwhichcontains
thanwithabroad,redshiftedironlinefromreflectionfromthevery the iron K-shell edge and its associated absorption line structure
innermost(i.e.<10Rg)accretiondisc. (Figure 13, Kallman et al. 2004). We fit an additional inverted
Wephenomenologicallymodelthisbypartialcoveringofthe Gaussianoffixedwidth(σ = 0.1keV)totheXMM-Newtondata
sourcebypartiallyionisedmaterial(e.g.Milleretal.,2007;Turner andfindthatthefitissignificantlyimproved,toχ2 = 418.7/391
ν
etal.,2007),usingagridofXSTAR(v2.1l)photoionisationmodels and417.6/391 for theGauandPcfxicontinuum models, respec-
baseduponthepubliclyavailabletabulated’grid25’.Thisusesthe tively.Thelineenergyandequivalent widthinbothis∼ 7.6keV
Fe K treatment of Kallman et al. (2004), a turbulent velocity of (7.05±0.05keVobserved)and110+−4450eV,respectively.Weallow
σ =200kms−1andsolarabundances(Grevesse&Sauval1998), alinewiththesameenergyandwidthintheSuzakudata,andfind
whiletheilluminatingcontinuumfrom1–1000RydbergshasΓ = a90%confidenceupperlimittoitsequivalentwidthof<25eV.
2.2 rather than Γ = 2, and spans a wider (but coarser) range of
column (0.05 to 500×1022 cm−2, 10 points) and logξ (-3 to 6,
12points).Thispartiallyionisedabsorptionisappliedtoafraction
5 THEORIGINOFTHEIRONKSHELLABSORPTION
f of the assumed continuum, whilethe remaining (1−f) isnot
affectedbythismaterial.1 Thustheabsorptionlineissignificantlyweakerinthe2005Suzaku
WefixtheredshiftofthepartialcoverertothatoftheAGN, data,sotheabsorption haschanged onatimescaleof < 4years.
andtietheionisationparameterofthismaterial(butnotitscover- Eitherthecolumnhasphysicallymoved,oritsionisationstatehas
ingfraction)betweenthetwodatasets.Thismodelgivesanequally changed (or both). The former puts alimit on the sizescale of 4
good fit as the broad Gaussian model, with χ2 = 439/393 for lightyears,unfeasiblysmallforanydiffuseGalactichaloorinter-
logξ ∼ 1.2. The column of the ionised material is consistent galacticemission(whichshouldbeonkpcscales),whilethelatter
between the two datasets at ∼ 2 × 1023 cm−2, but the cover- sets a limit on the density through the recombination timescale,
τ = 1/(α (T)n ),whereα istherecombinationrate,whichis
r r e r
dependentonthetemperature,T.ForaWHIMorigin,theabsorp-
1 ThismodelispubliclyavailableasanadditionalmodelforXSPECfrom tionlinemustbeassociatedwithFeXXVIinorderthatitsenergy
http://heasarc.gsfc.nasa.gov/docs/xanadu/xspec/newmodels.html matchesthatobserved. Suchmaterialshouldalsobecollisionally
4 J. Reeves et al.
Model Γa Norm×10−3a lineE(keV)b σ(keV)b EW(eV)b lineE(keV)c σ(keV)c EW(eV)c χ2
ν
NHcm−2 logξ CovFrac
po 1.77±0.03 0.88
1.76±0.03 0.99 744/403
Gau 1.93±0.05 0.96 6.63±0.09 0.24±0.04 250+−8700 4.36+−00..2239 1.07+−00..2240 810+−211800
1.87±0.04 1.07 6.52+0.04 270±50 4.39+0.38 290±100 441.4/393
−0.05 −0.48
Pcfxi 2.50+0.16 4.07 6.55+0.09 0.20±0.04 235±50 20+8 2.18+0.29 0.78+0.08
−0.17 −0.07 −4 −1.20 −0.08
2.10+−00..1120 2.00 6.53+−00..0052 210±45 16+−162 0.42+−00..0192 439.6/393
Table1.Fitparametersanduncertainties (∆χ2 = 2.7)fortheXMM-Newton2001andSuzaku2005spectrafromPG1211+143forthemodelsshownin
Fig3.aContinuumphotonindexandnormalisation(unitsphotonscm−2s−1keV−1at1keV).bEnergy(keV),intrinsicwidthσ(keV)andequivalentwidth
(eV)oftheironline,quotedinthequasarrestframe.cEnergy(keV),intrinsicwidthσ(keV)andequivalentwidth(eV)ofthebroadredshiftedGaussian(Gau
model),orforthepartialcovering(Pcfxi)model,columndensityNH(units×1022cm−2),ionisationparameterξ(unitsergcms−1)andcoveringfraction.
trinsicwidthof thelineof σ < 0.2 keV. Thisgivesacolumn of
8±3×1022cm−2,withanionisationparameteroflogξ=2.8+0.2
−0.3
atanobservedredshiftofz =−0.07±0.01i.e.implyinganAGN
outflowvelocityof∼ 0.15c. Whilethederivedcolumnisdepen-
dentontheturbulentvelocity,thecurveofgrowthisinthelinear
regimehere,soincreasingtheturbulentvelocitydoesnotincrease
theequivalentwidthoftheline,leadingtoarobustlowerlimitof
NH >5×1022cm−2.
Thelowerlimitonthedensity,combinedwiththecolumnden-
sity,cangiveanupperlimitonthesizescale∆Roftheabsorber
asN =n∆R.AhugecolumnofN ≥ 1025 cm−2 isrequired
H H
inorder toproduce aniron absorption linewithequivalent width
of 100 eV if the gas velocity is simply set by its temperature of
107.5 K(Kotanietal.2000;2006)asexpectedfromanylocalhot
gas.Suchalargecolumnisinconsistentwiththespectrum,asthis
produces a strong dip at 8–10 keV (rest frame) due to the FeK-
shelledgestructure(Kallmanetal2004), whichisnotpresent in
thedata.IndeedfromthelackofanironKedgeinPG1211+143,
thissetsanupperlimittothecolumnof<1024cm−2andrequires
that there must be substantial turbulent velocity (> 1000kms−1
derived from the curve of growth) in excess of the thermal mo-
tionstomodelthelineEW.ThisitselfisinconsistentwithaWHIM
origin. With this, the upper limit on the absorber size scale is
∆R < N /n = 1024/4×103 < 2.5×1020 cm. This is un-
H
feasiblylow tobe associated witheven thesmallest local diffuse
hotgas,thekpcscaleGalactichalo.
Another constraint on the properties of the material comes
from theemission measure EM = n2V where V = 4πR2∆R
Figure3.∆χ2residualsagainstapowerlaw(top),ironemissionlineand is the volume, assuming that the gas is distributed evenly in a
broadredshiftedGaussian(middle)andironemissionlineandpartialcov- spherical shell at distance R. The total bremsstrahlung luminos-
ering by partially ionised material (bottom) for the XMM-Newton 2001 ityisLbrems ∼ 2×10−27T1/2EM,sothesurfacebrightnessin
(red) and Suzaku 2005 (black) data, respectively. The absorption feature solidangledΩisL /(4πR2)(dΩ/4π).Forasolidangleof1
brems
at∼ 7keVintheXMM-Newtondataissignificantlystrongerthaninthe arcmin2 = 10−7 srthisgives∼ 1.3×10−35T1/2nN > 10−5
H
Suzakudatairrespectiveofthephenomenologicalcontinuummodel. ergss−1cm−2arcmin−2,i.e.brighterthantheCrabineverysquare
arcmin in X-rays. Indeed the observed upper limit to the diffuse
skysurfacebrightnessinthe3/4keVbandis∼ 2×10−4 counts
ionised, and requires temperatures > 107.5 K in order to be the s−1arcmin−2(Bregman&Lloyd–Davies2007),correspondingto
dominantion.Thisgivesarecombinationrateofα ∼2.5×10−12 afluxof<2×10−15ergss−1cm−2arcmin−2,10ordersofmag-
r
cm3 s−1 (e.g. Arnaud & Rothenflug 1985), so for this to be less nitudebelowthepredictedvalue.
than 4 years requires densities > 4×103 cm−3, which is 6 or- Thusthevariabilityandcolumnappeartoruleoutanysortof
dersof magnitude above thetypical density evenfor alocal halo non-AGNoriginfortheabsorbingmaterial.Thebestfitidentifica-
component(e.g.Bregman&Lloyd–Davies2007). tionbyPP06ofthehighlyionisedabsorptionasbeingdominated
WemodeltheFeKabsorptionlineusingtheWARMABSXS- byHe–like Fealsorulesout alocal origin asthelineisthen not
TARphoto-ionisationcodeincorporatedintoXSPEC,adoptingso- closetotherestwavelengthofthetransition,showing ablueshift
lar abundances. Weassume aturbulent velocityof 5000 kms−1, withrespecttothelocalframeof−0.07.ThisisbecausetheMg,
below theupper limitof < 8000 kms−1 setby theobserved in- SiandSK-shellabsorptionseenintheXMM-NewtonCCDspec-
IronK-shellabsorptionisnot fromtheWHIM 5
showironKabsorptionfeaturesclearlyshowarangeof(intrinsic
andobserved) velocities,removingtheapparenttrendfortheline
105 PDS 456 energy to appear at the rest energy for these transitions. Thus it
isclear that thismaterial isamildly relativisticoutflow from the
s)−1 PG 1211 AGN.Itshighvelocitymeansthatitskineticenergycanbecom-
m parable to the bolometric radiated luminosity of the AGN (King
k
y ( &Pounds 2003; Pounds etal 2003; Pounds&Reeves2007), yet
ocit itshighionisationmeansthatitiseffectivelyinvisibleinallother
Vel 104 wavebands. While such a major component of AGN energetics
ow could go unnoticed in individual objects, there is increasing ev-
utfl idence that strong AGN feedback controls galaxy formation and
O
evolution.Mildlyrelativisticwindsprovidemoreefficientheating
than the jet due to their impact on a larger area, so these highly
0 ioniseddiscwindsmaybethekeytounderstandingthegrowthof
0
0 structureintheUniverse.
11000 104 105
Recession Velocity (km s−1)
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McKernanB.,YaqoobT.,ReynoldsC.S.,2007,MNRAS,379,1359
at7.7keV(Markowitzetal.2006;Braitoetal.2007)inconsistent
McKernanB.,YaqoobT.,ReynoldsC.S.,2005,MNRAS,361,1337
withtherestenergyofanyFeKαtransitionline.Afurtherexam- McKernanB.,YaqoobT.,ReynoldsC.S.,2004,ApJ,617,232
pleisfromthenew2007SuzakudatafromPDS456(Reevesetal. MillerL.,TurnerT.J.,ReevesJ.N.,GeorgeI.M.,KraemerS.B.,WingertB.,
2007, in prep), which shows iron K absorption lines observed at 2007,A&A,463,131
7.6and8.2keV,inconsistentwithlocalabsorptionfromironKα. MiniuttiG.,PontiG.,DadinaM.,CappiM.,MalagutiG.,2007,MNRAS,
Indeed the iron K absorption features seen in high redshift BAL 375,227
QSO’sarelikewiseveryfarfromtheironKαrestenergiesforlo- Mitsuda,K.,etal.,2007,PASJ,59,1
PoundsK.A.,ReevesJ.N.,2007,MNRAS,374,823
calmaterial(Chartasetal2002,2003).
PoundsK.A.,PageK.L.,2006,MNRAS,372,1275
Pounds K.A., Reeves J.N., King A.R., Page K.L., O’Brien P.T., Turner
M.J.L.,2003,MNRAS,345,705
6 CONCLUSIONS PoundsK.A.,King,A.R.,PageK.L.,O’BrienP.T.,2003b,MNRAS,346,
1025
We show that the observed variability in the absorption line in
Pounds K.A., Reeves J.N., King A.R., Page K.L., O’Brien P.T., Turner
PG1211+143 between theXMM-Newton andSuzakudatataken
M.J.L.,2003b,MNRAS,345,705
4 years apart conclusively rules out a diffuse gas origin such as ProgaD.,KallmanT.R.,2004,ApJ,616,688
thelocalGalactichaloorWHIM.Thegasmustbeassociatedwith ReevesJ.N.,etal.,2007,PASJ,59,301
the AGN, as is further evidenced by its large column density in ReevesJ.N.,O’BrienP.T.,WardM.J.,2003,ApJ,593,L65
theXMM-Newton2001datawhichisfartoohighforlocalorin- RisalitiG.,BianchiS.,MattG.,BaldiA.,ElvisM.,FabbianoG.,ZezasA.,
tergalactic gas. The conclusive identification with the AGN, and 2005,ApJ,630,L129
theimplausibilityofanyalternativelinetransitionotherthaniron TurnerT.J.,MillerL.,ReevesJ.N.,KraemerS.B.,2007,A&A,475,121
Kαmeansthatthelargeoutflowvelocityof∼0.1cisinescapable. YoungA.J.,LeeJ.C.,FabianA.C.,ReynoldsC.S.,GibsonR.R.,Canizares
C.R.,2005,ApJ,631,733
Suchmaterialispredictedfromthewindswhichareproducedfrom
luminousaccretiondiscsinAGN(Proga&Kallman2004).
Thecoincidenceoftheoutflowvelocitywiththesourcered-
shift in these data is not significant. Other powerful AGN which