XMM-Newton unveils the complex iron K alpha region of Mrk 279

0.33 MB·

by  E. Costantini

Astronomy&Astrophysicsmanuscriptno.12555 (cid:13)c ESO2010
January15,2010
α
XMM-Newton unveils the complex iron K region of Mrk 279
E.Costantini1,J.S.Kaastra1,2,K.Korista3,J.Ebrero1,N.Arav4,G.Kriss5,andK.C.Steenbrugge6
1 SRONNationalInstituteforSpaceResearch,Sorbonnelaan2,3584CAUtrecht,TheNetherlands
2 AstronomicalInstitute,UtrechtUniversity,POBox80000,3508TAUtrecht,TheNetherlands
3 DepartmentofPhysics,WesternMichiganUniversity,Kalamazoo,MI49008,USA
4 DepartmentofPhysics,VirginiaTech,Blacksburg,VA24061,USA
5 SpaceTelescopeScienceInstitute,3700SanMartinDrive,Baltimore,MD21218,USA
6 UniversityofOxford,StJohn’sCollegeResearchCentre,Oxford,OX13JP,UK
0
Received/Accepted
1
0
ABSTRACT
2

n Wepresenttheresultsofa∼160ks-longXMM-NewtonobservationoftheSeyfert1galaxyMrk279.Thespectrumshowsevidence
a of both broad and narrow emission features. The FeKα line may be equally well explained by a single broad Gaussian (FWHM
J ∼10000kms−1)orbytwocomponents:anunresolvedcoreplusaverybroadprofile(FWHM∼14000kms−1).Forthefirsttime

5 we quantified, via the “locally optimally emitting cloud” model, the contribution of the broad line region (BLR) to the absolute
1 luminosityofthebroadcomponentoftheFeKαat6.4keV.WefindthatthecontributionoftheBLRisonly∼3%.Inthetwo-line
componentscenario,wealsoevaluatedthecontributionofthehighlyionizedgascomponent,whichproducestheFeXXVIlineinthe

] ironKregion.ThiscontributiontothenarrowcoreoftheFeKαlineismarginal<0.1%.Mostoftheluminosityoftheunresolved,
O componentofFeKαmaycomefromtheobscuringtorus,whilethevery-broadassociatedcomponentmaycomefromtheaccretion
C disk.However,modelsofreflectionbycoldgasaredifficulttotestbecauseofthelimitedenergyband.TheFeXXVIlineat6.9keVis
. consistenttobeproducedinahighcolumndensity(NH ∼1023cm−2),extremelyionized(logξ ∼5.5−7)gas.Thisgasmaybea
h highlyionizedouterlayerofthetorus.
p
Keywords.Galaxies:individual:Mrk279–Galaxies:Seyfert–quasars:absorptionlines–quasars:emissionlines–X-rays:galaxies
-
o
r
t
s 1. Introduction nent,probablyoriginatingfarfromtheblackhole,hasbeendis-
a
entangledfromtheFeKαline(Yaqoob&Padmanabhan2004;
[ The X-ray spectrum of active galactic nuclei (AGN) bears the
Jime´nez-Bailo´netal.2005).Thiscomponentispredictedinthe
1 signature of different environments in the vicinity of the su- unification model (Antonucci&Miller 1985) as produced in a
v permassive black hole. In particular, the emission features de- high-column density, cold region, about 1pc away from the
2 tected in an X-ray spectrum are believed to arise in different
blackhole(e.g.Krolik&Kallman1987;Kroliketal.1994)and
1 environments, with dramatically distinct physical characteris-
thenscatteredintoourlineofsight(e.g.Ghisellinietal.1994).
7 tics of temperature and density. Narrow emission line profiles
An unresolved FeKα line and the associated reflection seems
2 (especially from C, N, O He-like and H-like ions), not sig-
indeed to be ubiquitous in bright type 1 objects (Nandraetal.
1. nificantly variable on a short time-scale, may form in the far 2007).
0 narrow-lineregion(e.g.Poundsetal.2004).Thebroadsymmet-
AstheFWHM ofthenarrowcoreiscompatiblewiththewidth
0 riclineprofiles,themoreandmoreoftendetectedinAGNspec-
of the UV/optical broad lines (Yaqoob&Padmanabhan 2004),
1 tra (Kaastraetal. 2002; Ogleetal. 2004; Steenbruggeetal.
acontributiontothebroadcomponentfromtheBLRisinprin-
: 2005; Costantinietal. 2007, hereinafterC07),are consistentto
v ciplepossible.However,consideringindividualsources,noev-
i be produced, at least in one case, within the broad line re- ident correlation between the FWHM of neither the hydrogen
X gion (C07), which is ≈ 5.6L142/2 light days away from the Hα or Hβ, supposed to be entirely formed in the BLR, has
r central black hole (L is the luminosity of CIV in units of been found (Sulenticetal. 1998; Nandra 2006). These results
a
1042ergs−1, Peterson1993). Emissionfromtheaccretiondisk, are based on optical and X-ray data not simultaneously col-
located in the proximity of the black hole, has been exten- lected.In NGC7213,usingsimultaneousobservations,the Hα
sively studied via the iron Kα line at 6.4keV. For this line, andtheresolvedironlinesharedthesamevalueoftheFWHM
relativistic effects result in a skewed and asymmetric line pro- (Bianchietal.2008).
file (e.g. Tanakaetal. 1995; Youngetal. 2005; Wilmsetal.
2001). Recently, relativistic profiles have been reported also Mrk 279 is a bright Seyfert 1 galaxy (F ∼ 2.55 ×
for otherlines, in particularOVIII (Branduardi-Raymontetal. 10−11ergcm−2s−1, this study), extensively studied in X-rays
2001; Kaastraetal. 2002; Ogleetal. 2004; Steenbruggeetal. (C07andreferencestherein).C07,usingChandra-LETGSdata
2009). However,a contributionto the line emission from other ofthissource,forthefirsttimequantifiedthecontributionofthe
AGN regions (NLR, BLR and molecular torus) add up to BLR tothe softX-rayspectrum.Indeed,thanksto thesimulta-
these relativistic profiles. A narrow and not variable compo- neous observation of the broad lines in the UV band by HST-
STIS and FUSE (Gabeletal. 2005) the ionization structure of
Sendoffprintrequeststo:E.Costantini theBLRhasbeendeterminedusingthe“locallyoptimallyemit-
Correspondenceto:[email protected] ting clouds” model (LOC, Baldwinetal. 1995). This allowed
2 E.Costantinietal.:XMM-NewtonobservationofMrk279
to infer the X-ray broadlines luminosities, thatwere then con- Table1.XMM-Newtonobservationlog.
trastedwiththeLETGSdata.C07foundthatthebroadlinesob-
servedinthesoftX-rayspectrum(wheretheOVIItripletwasthe Orbit Exp Expnet date Epic-PNrate
mostprominentone)wereconsistenttobeentirelyformedinthe (ks) (ks) dd-mm-yy c/s(0.3–10keV)
BLR.TheaveragepeakofproductionoftheX-raylinesispos- 1087 59.3 27.4 15−11−05 25.7
sibly∼10timescloserinwithrespecttotheUVlines,implying 1088 59.7 32.0 17−11−05 21.6
a largerKeplerianwidth forthe X-raylines.Unfortunately,the 1089 38.0 15.5 19−11−05 23.5
limitedLETGSenergybandpreventedC07tostudytheironKα
Note: The orbit number, the nominal exposure, the net exposure, the
region.HerewepresentadetailedstudyoftheX-rayspectrum
dateandthe2–10keVEpic-PNbackground-subtracted countratesare
ofMrk 279asobservedbyXMM-Newton,focusingmainlyon
listed.
theemissioncomponentsandthe6.4–7keVregion.
The paperis organizedas follows.Sect. 2 is devotedto the
spectral analysis of the data. In Sect. 3 we modelthe emission
spectrumevaluating,foreachcomponent,thecontributiontothe
FeKα line. In Sect. 4 we discuss our results and in Sect. 5 we
presenttheconclusions.Thecosmologicalparametersusedare:
H0=70 kms−1Mpc−1, Ωm=0.3, and ΩΛ=0.7. The abundances
weresettosolarfollowingAnders&Grevesse(1989)prescrip-
tions. The redshiftis 0.0305(Scottetal. 2004). The quoteder-
rors are 68% confidence errors (∆χ2 = 1), unless otherwise
stated.
2. Thedataanalysis
The observation of Mrk 279 was spread over 3 orbits on
November 15–19 2005. In Table 1 we report the observation
log. The data were processed with the standard SAS pipeline
(SAS 7.0)and filtered for any backgroundflares. The Epic-PN
exposuretimeinsmall-windowmodereducedtheexposuretime
fromtheoriginal160ksto110ks.Afterthebackgroundfiltering Fig.1. Epic-PN light curves in the 0.3–2 and 2–10keV band.
weobtainedanetexposuretimeof∼75ks.Thelightcurveofthe Themaximalvariationisabout36%.
threetimeintervalsisdisplayedinFig.1inthesoft(0.3–2keV)
andhard(2–10keV)band.Themaximalvariationisabout36%
inbothenergybands.Toincreasethestatistics,wecombinedthe χ2 is again unacceptable(χ2/ν ∼ 6). The residuals show that
Epic-PNdataafterverifyingthatthephysicalparametersofthe a broad band component is still missing. We then substituted
modeling were the same for the three separate data sets. Epic- the simple powerlaw model with a broken power law, obtain-
MOS1camerawassetintimingmode.Duetostillexistingen- inganacceptabledescriptionofthecontinuum.Thereducedχ2,
ergy gain uncertainties in this mode, we did not analyze these considering only the best-fit continuum, without narrow emis-
data further. Epic-MOS2 were collected in imaging mode that sion/absorptionfeatures,isχ2/ν ∼ 2.5.Theparametersofthis
resultedinabout61ksofnetobservation,afterfilteringoutshort phenomenologicalinterpretationof the continuum are listed in
highbackgroundepisodes.ForbothEpic-PNandMOS2weim- Table 2 and the fit shown in Fig. 2. The parametersin Table 2
posedat least 20 countsper channelto allow the use of the χ2 andreducedχ2refertothetotalbestfit,includingemissionand
minimization. absorptionfeatures,asdescribedbelow(Sect.2.2,2.3).
TheRGStotalusefulexposuretimeisabout110ks.EachRGS For comparison,we analyzedalso MOS2 data, with the caveat
datasethasbeenrebinnedbyafactor5whichresultedinabin that deviation from the Epic-PN best fit may occur, especially
size of ∼0.07A˚ and signal-to-noise ratio of 10 for each set of atthelow(E<0.5keV)andhighenergy(E>8keV)endsofthe
data that were simultaneously fitted. The spectral analysis was band,andattheinstrumentalgoldedgearound2keV2.Thefinal
carriedoutusingthefittingpackageSPEX1(ver2.0). MOS2best-fitparametersareshowninTable2.Theparameters
Inthefollowingwedescribefirsttheunderlyingcontinuum, agree well with the Epic-PN fit, albeit with some differences,
then the emission line spectrum and finally the absorption whichweascribetothecrosscalibrationmismatchbetweenthe
featureswhichfurrowthespectrum. MOSandPNcameras.
2.2. Theemissionlinespectrum
2.1. Thecontinuum
We see evidence of a range of broad and narrow emission
ThecontinuumhasbeenfirstdeterminedusingEpic-PN.Asin- lines both in the RGS and in the Epic spectra. Here we re-
gle powerlaw fit, modified by Galactic absorption is unaccept- fer as narrow lines the ones which are unresolved by Epic-
able(χ2/ν >34,whereν isthenumberofdegreesoffreedom). PN (i.e. FWHM<7000kms−1), but may be resolved by RGS.
Thisfitproducessystematicresidualsbothatsoftandhardener- Then the broad lines (FWHM>7000kms−1) are instead re-
gies,inadditiontonarrowfeaturesbothinabsorptionandemis- solved also by Epic. Finally, the very broad lines are the ones
sion. We then addeda blackbodycomponent,modifiedbyco- withFWHM∼14000kms−1.Theonlyexampleofthelatterin
herentComptonscattering(Kaastra&Barr1989).Thereduced
2 Several examples are provided at
1 http://www.sron.nl/divisions/hea/spex/version2.0/release/ http://xmm2.esac.esa.int/cgi-bin/ept/preview.pl
E.Costantinietal.:XMM-NewtonobservationofMrk279 3
Fig.2.BestfitfortheEpic-PNdata.Themodelincludesamod- Fig.3. RGSspectrumintheOVIIregionintermsofratiofroma
ifiedblackbody(dottedline),abrokenpowerlaw(dashedline), continuumfit.Fordisplaypurpose,onlytherebinneddatafrom
bothabsorbedbyionizedgas,abroadFeKα(seeSect.2.2)line orbit1087and1088are shown. The measurementsreportedin
andtwonarrowlinesat6.9and7.05keV(dash-dottedlines). thepaperarebasedonthefullRGSexposure.Thelabelsindicate
someofthemainfeaturesofthewarmabsorber.
Table2.Best-fitcontinuumparametersforaphenomenological
model.
frame)andabroademissionfeature,consistentwithablendof
PN MOS2
FeXXVI and FeKβ at 6.90 ± 0.06keV and 7.05 ± 0.05keV
Tmbb keV 0.16±0.02 0.12±0.02 respectively (Fig. 4, upper panel). Because the MOS2 spec-
ΓΓ12 21..0785±±00..0011 21..0832±±00..0023 tral analysis deliver a slightly different powerlaw slope at en-
E0 keV 2.31±0.04 2.0±0.1 ergies > 2keV (Table. 2), and the data are affected by lower
χ2/ν 281/234 262/208 statistics, we restrict the iron line analysis to the Epic-PN data
only. At first we modeled the FeKα line with a single unre-
Note:Epic-PNandMOS2fittedseparately.Thereducedχ2 referhere solved Gaussian. Although the general fit improves (χ2/ν =
tothefinalbestfit. 371/243 ∼ 1.5) This model does not provide a good fit for
the line, as evident in Fig. 4 (lower panel). Next, we consid-
eredthelineascomposedofanunresolvedGaussianandavery
the present data is the broad, possibly relativistically smeared, broadcomponent,leadingtoasignificantimprovementofthefit
componentoftheironlineat6.4keV. (∆χ2/∆ν = 32/3,Table 4). The verybroad componenthas a
InourpreviousstudybroademissionfromablendoftheOVII FWHM of 0.29±0.04keV, correspondingto ∼14000kms−1.
tripletlineswasverysignificantlydetected(at∼ 6σ,C07).We We tested thisverybroadcomponentofthe FeKα line against
thereforelookedforsuchevidenceinthepresentRGSdata.We arelativisticallysmearedprofile(Laor 1991).Withthismodel,
fix the wavelength of the line centroid (λ=21.9A˚) to the val- the line should be viewed at an angle of ∼ 15◦, with a radial
ues found in C07. We also fix the FWHM of the broad fea- emissivity law r−q, with q ∼ 1.5 (Fig. 5, Table 4). These pa-
ture, which could notbe resolved in the individualOVII lines, rameters mimic a regular, almost symmetric, line profile (e.g.
tothepreviouslymeasuredvalue:1.4A˚,correspondingtoabout Reynolds&Nowak2003).Thestatisticalimprovementwithre-
19000kms−1fortheblend.Wefindthattheintrinsiclinelumi- specttoasimplevery-broadGaussianis:∆χ2/∆ν ∼ 5/1,cor-
nositydecreasedwithrespecttothe2003observationgoingfrom respondingto∼2.2σ.FortheFeKαfeature,weconsideredalso
50±8 to 13±7 in units of 1040ergs−1. The same line lumi- asingleGaussianwiththewidthfreetovary(Table3).Theline
nosityismeasuredalsousingthethreeRGSdatasetsseparately. centroidis 6.41±0.08 in the rest frameof the source,and the
The inclusion of the line improvesthe fit by ∆χ2/∆ν ∼ 6/1, intrinsicluminosityis61±6×1040ergs−1.Thelineisresolved
correspondingtoonly2.4σsignificance.Thebroadlineisalsoa byEpic-PN,withaFWHMof0.21±0.03keV(corresponding
necessaryemissioncomponenttocorrectlyfitsomeunderlying to ∼ 10000±1000kms−1). The statistical improvementwith
absorptionfeatures(e.g.OV, OVI and OVII), importantin the respecttoasingleunresolvedlineis∆χ2/∆ν =37/1.
globalfittingoftheionizedabsorberparameters(Fig.3).Thein- The inclusion of other two narrow lines, at the energy of the
clusionofthislow-ionizationabsorberaloneimprovesthefitof FeXXVI andtheFeKβ furtherimprovesthefitby∆χ2/∆ν =
theRGSspectrumby∆χ2/∆ν ∼58/3. 31/2.Forconsistency,wetestedtheLaormodel,withthesame
IntheRGSbandwedetectthenarrowOVIIforbiddenlinewitha line parameters, to the FeKβ, fixing the line ratio to 0.135
flux(9±6×10−15ergcm−2s−1),consistentwiththeChandra (Yaqoobetal. 2007; Palmerietal. 2003). As expected the flux
measurement(C07). The line is marginally detected (Table 3), ofabroadFeKβ linehasanegligibleeffectonthefit,therefore
probablybecauseofaneighboringbadpixel.Forotherrelevant weignorethisadditionalcomponentinsubsequentfits.Thisneg-
narrowlines, suchas OVIII Lyα, NeIX andNeX, we onlyob- ligiblecontributionofabroadprofileoftheFeKβalsostrength-
tainupperlimitsontheluminosity(Table3). ens our assumption that the bump seen in the 6.9–7.05 region
Both the PN and MOS2 spectra show a complexstructurebe- isablendoftwonarrowlines(FeXXVI andFeKβ)ratherthan
tween6.4and7keV:aprominentFeKαlineat∼6.4keV(rest- a broad FeKβ line arising from the accretion disk. This fit is
4 E.Costantinietal.:XMM-NewtonobservationofMrk279
Table 3. list of line luminosities as measured by Epic-PN
(inst.1)andRGS(inst.2).
ion Rest Lum F-test inst.
obs
wavelength
(A˚) (1040ergs−1) %
narrowlines
FeKβ 1.75 6.6±2.8 89.0 1
FeXXVILyα 1.77 10.0±2.7 99.98 1
FeXXVf. 1.85 <4.7 ... 1
FeKα1 1.93 12.0±7.0 >99.99 1
NeX 12.14 <1.2 ... 2
NeIXf. 13.69 <1.25 ... 2
OVIIILyα 18.97 <1.0 ... 2
OVIIf. 22.10 3.1±2.0 89.0 2
NVIILyα 24.78 <3.1 ... 2
NVIf. 29.53 <1.18 ... 2
broadlines
OVIItriplet2 21.9 13±7 95.0 2
Fig.4.Upperpanel:residuals,intermsofσtothecontinuumin FeKα3 1.93±0.03 61±6 >99.99 1
theironlineregionasobservedbyEpic-PN.Threefeaturesare
evident: a prominentFeKα line and weaker lines identified as Notes:Welisttheion,therest-framewavelength,theintrinsicluminos-
FeXXVI andFeKβ.Lowerpanel:residuals,intermsofσ after ityandtheirsignificance,fornarrowandbroadlines.
theinclusionofa narrowline at6.4keV. TheEpic-PNdataare 1Onlynarrow,unresolvedcomponentinatwo-linesmodel.
identifiedbysimplecrosses,andtheMOS2databydiamonds. 2BlendoftheOVIItripletlines.
3SingleGaussianwithfreeline-widthmodel.
Table4. ParametersfortheverybroadcomponentoftheFeKα
lineinatwo-componentsmodel.
Gauss1 Laor2
E keV 6.41±0.01 6.47±0.03
FWHM eV 0.29±0.04 ...
Lum 1041ergs−1 4.64±0.16 5.0±0.7
q ... 1.5±0.5
i deg ... 15±7
χ2/ν 339/240 334/239
Notes: Third column: one Gaussian with free width. Fourth column:
Profileincludingrelativisticeffects.Thereducedχ2 referstoaninter-
mediatefit(seeSect.2.2)
1 Welisttheenergyofthecentroid,theluminosityofthelineandthe
FWHM.
2Welisttheenergyofthecentroid,theluminosityoftheline,theemis-
Fig.5.Spectrumandbestfitintheironlineregionasobserved
sivitylaw,qandtheinclinationangle,i.
byEpic-PN.Thesolidlinesdisplaythebroadandnarrowcom-
ponents added to fit the emission features: a prominent FeKα
lineandweakerlinesidentifiedasFeXXVIandFeKβ. withNH ∼3.6×1019cm−2andtemperatureT ∼7.2eV(C07,
Williamsetal. 2006). Further, we detect other two, photoion-
ized,gascomponentsintrinsictothesource.Wereporttheaver-
showninFig.5. agephysicalparametersofthewarmabsorbersasmeasuredby
Thereducedχ2 ofafitwithallemissionlinesincluded,butno
absorption, is 308/238. With this final component(see below),
the χ2/ν = 281/234 ∼ 1.2. The lines’ parameters and their Table5. Bestfitparametersfortheabsorbedspectrumasmea-
significancearelistedinTable3.Inallthelinesfitting,wealso suredbyRGSandEpic-PN.
letthenormalizationfreeto varytowardsnegativevalues.This
allowedustouse the F-testasan indicationofthe significance comp. Param. RGS PN
ofthelines(Protassovetal.2002). 1 NH 0.7±0.2 1.5±0.5
logξ 0.8±0.3 1.1±0.3
vout −300±150 –300fix.
2.3. Theunderlyingabsorption 2 NH 3±1 4±1
logξ 2.6±0.1 1.8±0.1
Mrk 279 shows a complex absorption spectrum (C07), whose vout −400±150 –400fix.
characteristicsarebeststudiedusingRGS.InanalogywithC07,
wemodeledtheabsorptionwithtwoGalacticcomponents,that Note:Foreachcomponentwelistthecolumndensities(NH)inunitsof
is a neutral gas (NH = 1.64 × 1020, Elvisetal. 1989) and a 1020cm−2,ionizationparameter(logξ)andoutflowvelocities(vout,in
ionized gas, highlighted by the OVII absorption line at 21.6A˚, kms−1).
E.Costantinietal.:XMM-NewtonobservationofMrk279 5
However,theionizingcontinuum,andasaconsequencethe
lineluminosities,mayhavechanged.InFig.6theSEDusedfor
thepresentobservation(2005)isdisplayed(solidline).Theop-
ticalpointsaremeasuredbyOMusingtheU(344nm),UVW1
(291nm), UVM2 (231nm) and UVW2 (212nm) filters. The
unabsorbed X-ray continuum is evaluated using the Epic-PN
data.Forenergieshigherthan10keV,thepowerlawcontinuum
was extended and artificially cut off at ∼150keV. On the very
lowenergyendoftheSED(farinfraredtoradioband),theshape
was takenfroma standardAGN SED template used in Cloudy
(Ferland 2004). We used Cloudy (version 07.02.02) to obtain
a line luminositygrid overa large range of r and n values. As
inC07,r rangedbetween1014.7−18cm.Thevalueofnranged
between 108−12.5cm−3. For both parameters the spacing of
the valueswas 0.125inlog. Forcomparison,we show also the
SED used for the 2003 observation. The overall optical flux is
higherforthepresentdata,whiletheX-raycontinuumremained
almostunchangedinfluxandsoftX-rayspectrum.
Fig.6.TheSEDofMrk279in2005measuredbyXMM-Newton
(solid line). The optical data are measured by OM, while the
InordertoinfertheBLRcontributiontotheFeKαline,we
broadbandX-raycontinuumismeasuredbyEpic-PN.Thedot-
havetorelyontheOVII tripletintheX-rayband,whoselumi-
tedlineshowstheSEDofthe2003dataforcomparison(C07).
nositycouldbetotallyaccountedforbytheLOCmodel(C07).
Therefore we assume that all the emission from the broad line
of the OVII triplet comes from the BLR. The OVII line lumi-
RGS and the Epic-PN in Table 5. The absorbersare character- nosity (LOVII = 13± 7 × 1040ergcm−2s−1) from the RGS
ized by a low NH. Thereforeabsorptionlines, well detected in data can be explained by the LOC model using the new 2005
the high-resolutionspectrum(Fig. 3), rather thanedges(which SED,withthevaluesofγ andC setbythepreviousanalysis,
V
are in this case shallow features in the Epic spectrum), are the withintheerrors.Giventheseconstraints,theresultingvaluefor
signature of the absorbers. The inclusion of a lower ionization γ =1.17±0.03,whichisheretheonlyfreeparameter,isfound
gasalonealreadyimprovestheEpic-PNfitby∆χ2/∆ν =17/2. tobeconsistentwithpreviousresults.Oncethisconstraintisset,
The inclusion of a two-component gas, with column densities we can predictalso the contributionof the FeKα and otherX-
andionizationparametersfreetovaryleadstoanimprovement raylines.
of the fit of ∆χ2/∆ν = 27/4, bringing the reduced χ2/ν to In Sect. 2.2 we have provided two statistically acceptable de-
∼ 1.20. A detailed analysis of the complex absorption and a scriptions of the FeKα line: a narrow+very-broadcomponent
comparison with previous results will be presented in a forth- modelandasingle,resolved,Gaussian.Onlyforthelattercase
comingpaper(Ebreroetal.,inprep.). the FWHM is similar to the one directly measured from the
UVdata(FWHM =8500–9500kms−1,Gabeletal. 2005).In
UV
Fig.7weshowtheBLRlineluminositiespredictedbytheLOC
3. ModelingoftheFeKα line region model in the X-ray band. Along with the OVII observed lu-
minosity we also plot the observed value for the FeKα line in
Inthissectionweevaluatethecontributionofdifferentregionin the case of a single Gaussian model (Table 3). The predicted
theproximityoftheAGNtothespectrumabove6keV. OVII/FeKα luminosity ratio is about 6.3 within the narrow
1.14-1.20 range for γ. Therefore, the BLR contribution to the
3.1. TheLOCmodelforthebroademissionlines FeKαlineisthenLBLR(FeKα)=2±1×1040ergs−1,about30
times smaller than the broadFeKα componentmeasuredfrom
HereweinvestigateapossiblephysicallinkbetweentheFeKα thedata.Forcomparisonwealsomadeapredictionontheiron
line and the optical BLR. In order to quantitatively evaluate line flux based on the 2003 SED and the BLR parameters de-
the contributionof the BLR to any X-ray broadlines, we used rivedinC07.InthatcasetheFeKαluminosityofironfromthe
the “locally optimally emitting clouds” model (Baldwinetal. BLRis10±5×1040ergs−1.
1995). This model considers the observed line luminosity as
a sum of lines emitted at different density n and distances r,
3.2. Variability ofthecontinuumandironlinecomplex
weightedbyapowerlawdistributionfornandr:n−β andr−γ
respectively (see e.g. C07, Koristaetal. 1997, for details). For Lines emitted at a few gravitational radii from the black hole
thepresentobservationwecanbenefitfromtheresultsobtained may show significant short term variability. We examined the
inC07:theyevaluatedthe“structure”oftheBLR(i.e.thedistri- FeKαline parametersin the threetime segmentsof ourobser-
butionofrandthecoveringfactor)fitting11UVlinesobserved vationusingasimpleGaussianmodel.Wefindthattheflux,the
byHST-STISandFUSEsimultaneouslytotheChandra-LETGS FWHM,centroidenergyandtheunderlyingpowerlawslopeare
data.Theyfoundaslopeforr,γ = −1.02±0.14andacover- nearly the same in response to the central-source variation. In
ing factor C = 34 ± 26%, keeping the slope for n fixed to ordertofurthertestavariabilityoftheFeKαfluxweanalyzed
V
–1(Korista&Goad 2000).ThegeneralstructureoftheBLRis bothanarchivalXMM-Newton-pndatasetwith anetexposure
notexpectedtohavechangedsignificantlyin the2.5yearsthat time of ∼26ks, collected in May 2002 and Chandra HETGS
have elapsed since the Chandra observation. Thereforewe ap- data, collected about 10 days later in May 2002 (Scottetal.
ply those value also to the present spectral energy distribution 2004; Yaqoob&Padmanabhan 2004). In Table 6 we show the
(SED). comparisonofthelineparametersofallobservationssince2002,
6 E.Costantinietal.:XMM-NewtonobservationofMrk279
Fig.7.Thesolidthickline showsthe predictedBLRlinelumi- Fig.8. Emission line contribution to the high ionization lines
nositiesintheX-raybandinunitsof1040ergs−1usingtheLOC (FeXXVI, FeXXV, NeX, OVIII). Triangles:data. Lightshaded
model,usingasconstraintsC =34±26%andtheobservedlu- line:rangeofmodelsviabletofitthedata.
V
minosityofthebroadOVIIline.Thevalueofγisconsistentwith
whatpreviouslyfoundforMrk279.Theasterisksarethevalue
oftheobservedbroadlineluminositiesbyXMM(Table3).The
dashed line shows the LOC modeling based on the 2003 SED
andobservedOVIIlineluminosity.Thefilledtriangleshowsthe
OVIIbroadlineluminosityobservedbyChandra.
Table6. ParametersoftheFeKαatdifferentepochs.
year E L FWHM
(keV) (1040ergs−1) (keV)
2002a 6.43±0.03 46±11 0.26±0.12
2002b 6.42±0.04 41±15 <0.20
2005obs1 6.42±0.01 56±8 0.19±0.05
2005obs2 6.40±0.02 53±8 0.17±0.05
2005obs3 6.42±0.03 86±17 0.3±0.1
Note:Welisttheenergy,intrinsicluminosityandFWHMforasingle-
Fig.9.Parameterspaceofparametersviabletoproducetheob-
line fit to the FeKα profile for the spectra obtained in 2005 in three
servedhigh-ionizationemissionspectrum.Upperpanel:Logof
separateorbitsandforobservationscollectedin2002byXMM-Newton
(2002a)andChandra-HETGS(2002b). the ionizationparameteras a functionof the logof thecolumn
density. Lower panel: Covering factor of the FeXXVI line as a
functionofthelogofthecolumndensity.
3.3. TheFeXXVI lineat6.9keV
forasingle-linemodel.
Priorto1994,Mrk279showedasignificant2–10keVfluxvari- TherearenodetectablechangesintheFeXXVIlineina3-years
ation,rangingfrom1−5×10−11ergcm−2s−1 (Weaveretal. timescale.Theabsenceofanyofthelines(orablendoflines)
2001).The2002Chandra-HETGSobservation,revealedavery of the FeXXV triplet is also peculiar (Table 4, Fig. 5). In or-
low-flux state of the source (∼ 1.2 × 10−11ergcm−2s−1, dertounderstandthepropertiesofthegasemittingFeXXVI,we
Scottetal. 2004), a factor of two lower than what measured created a grid of column density, logNH= 22.0–24.5, and ion-
by XMM-Newton, shortly before. In the last XMM-Newton ization parameter, logξ=3–7, using Cloudy. For lower-column-
observation the source shows a 2–10keV flux of ∼ 2.5 × density,lower-ionizationparametergas, the predictedemission
10−11ergcm−2s−1.Weseethat,despitethechangeinthecon- linewouldbetooweak,orabsent.Foraneasyscalingofthelu-
tinuum flux (a factor two), the FeKα line parameters did not minosity,weinitiallyconsideredthecoveringfactor(C )equal
V
dramaticallychangeinthreeyearstime,withintheerrors. to unity.This is the fractionof lightthat is occultedby the ab-
In the Chandra data the decline of the HETGS effective area sorber3.Acoveringfactorofoneisofcourseunrealistic,because
andthe low signal-to-noiseratiohamperedthe detectionof the inthiscaseabsorptionlinesofthesameionsshouldbeobserved.
FeXXVI andFe Kβ lines.On the contrary,inthe 2002XMM- ThereforeC mustbelessthanone.We also simplisticallyas-
V
Newton spectrum, bothlines, althoughblended,are detectedat
about95and90%confidencelevelforFeXXVIandFeKβ,re- 3 This is different from the global covering factor, the fraction of
spectively.Thelineluminositiesarethesameweobtainin2005, emission intercepted by the absorber averaged over all lines of sight,
withintheerrors. whichishasbeenestimatedtobeabout0.5(e.g.Crenshawetal.2003).
E.Costantinietal.:XMM-NewtonobservationofMrk279 7
sumethatasinglegascomponentisresponsibleforallFeXXVI Table7. Alternativefitofthecontinuum,includingreflection.
emission.Therefore,wetookthemeasuredintrinsicluminosity
ofFeXXVI asthereferencelinetoestimatethecoveringfactor. Tmbb keV 0.21±0.3
Weonlyhaveupperlimitsonotherhighlyionizedlines(namely Γ 2.5±0.1
NVII,OVIII,NeXandFeXXV,Table4),thereforeaformalχ2 blurred
fitcannotbeperformed.However,thoselimitscontaininforma- normpow 1051phs−1keV−1 4.1±0.3
tionthatcanbe usedto constrainttheparameters.In Fig.8 the Γ 1.73±0.08
set of parameters which are consistent with the measurements α >1.7
i deg <30
aredisplayed.
s 0.8±0.3
In Fig. 9, we show the parameter space of the possible solu-
unblurred
tions.Weseethattheionizationparametersufficienttoproduce normpow 1051phs−1keV−1 8.0±2.5
FeXXVI, but not FeXXV has to be larger that ∼5.3. The ion- Γ 1.73±0.08
izationparameterlinearlycorrelateswiththecolumndensity,as i deg 60fixed
forthehighestvaluesoflogξtheemissionlinesarevisibleonly s 1.1+1.3
−0.2
if there issufficientemittingmaterial.For the same reason,for χ2/ν 322/230
thesamecolumndensity,logξandC correlatelinearly.Onthe
V
otherhand,thecoveringfactoranti-correlateswithNH (Fig.9). Note:Themodelincludesablackbody,apowerlaw,blurredreflection
Indeed, for a high column density less material on the line of fromtheaccretiondiskandreflectionfromunblurredcoldanddistant
sightisneededtoproducetheobservedemission. material.Thevalueofχ2 referstofullmodeling,includingabsorption
red
(Sect.2.3)andemissionlines(Sect.2.2).
4. Discussion
The two reflection component cannot fit simultaneously the
4.1. Acomplexcontinuum
broad band continuum, as the soft energy portion of the spec-
The continuumspectrum of Mrk 279needs at least three com- trumissignificantlyunderestimated.Toreachanacceptablefit,
ponenttobecorrectlyinterpreted:amodifiedblackbodyanda this region has to be modeled again by a modified black body
broken powerlaw (Table 2). In principle, reflection from both andasinglepowerlaw(Table7).Residualsmainlyatthecross-
the accretion disk and from distant matter should be present ing points of the continuum components determine the value
(Nandraetal. 2007; Krolik&Kriss 1995; Mattetal. 1991; of the reduced χ2 (Table 7). Therefore a broad band modeling
George&Fabian 1991). The only difference would be that if only in terms of reflection is not straightforward. In addition,
arisingfromtheaccretiondisk,thereflectionandtheassociated hardX-rayscoverageisnotavailableandthisfitisbasedonthe
iron line should be modified by relativistic effects. The harder 0.3–10keVcontinuumshapeandanironlinewithtwoblended
tailwithΓ∼1.75andthedoublecomponentoftheironlinepro- components.Thislimitedknowledgeonthebroadbandbehavior
file(Sect.2.2)maybereminiscentofareflectionemissioncom- makesthefitparametersveryuncertain.
ponent. We therefore tested this scenario, in comparison with
ourphenomenologicalmodelforthecontinuum,includingboth
4.2. ThecontributionoftheBLRtotheFeKαline
types of reflection in the model (model REFL in SPEX). This
model simultaneously considers the Compton reflected contin-
We have quantitatively evaluated the BLR contribution to the
uum(Magdziarz&Zdziarski1995)andthefluorescentemission
emissionoftheprominentFeKαlineat6.4keV.Thehighlyion-
from FeKα (Zycki&Czerny 1994; Zyckietal. 1999) from a izedspecieofFeXXVIhasanegligibleroleintheBLR,therefore
Schwarzschildblackhole.Generalrelativityeffectsandconvo-
theemissionweseeatthoseenergiesintheX-rayspectrummust
lution with an accretion disk effectscan be easily switched off
comefromsomeotherlocation(Sect.4.4).Webasedthisanaly-
in this model. Free parameters are the normalizationof the re-
sisonpreviousresultsfortheBLRstructureandonthepresent
flectedpowerlaw anditsspectralindexΓ, thereflectionscale4 detection of the OVII broad line in the RGS spectrum. From
s,theemissivityscaleα(Zyckietal.1999),theinclinationangle the extensive experience of broad lines studies in optical spec-
iofthediskoftheironlineemission.Intheunblurredreflection, tra of AGN, it is known that measurements of broad and shal-
wefixedtheinclinationangleto60◦,basedontheaveragefound
lowemissionfeaturescanbeaffectedbylargeuncertaintiesand
foralargesampleofSeyferts(Nandraetal.2007).
should be cautiously treated. The limitation is due for instance
We findthatthe energyrangeE > 3keV canbe wellfittedby to the signal-to-noise ratio of the continuum level. Resolution,
acombinationofareflectorwithrelativisticpropertiesandbya
effectiveareaandcalibrationoftheinstrumentarealsorelevant
distantreflector. The formeraccountsfor the broadcomponent
effects.However,known,possiblynotcompletelycalibrated,in-
oftheFeKαline,whilethelattermodelsthenarrowcomponent strumentalnarrowfeatures(23.05,23.35A˚,deVriesetal.2003)
of the line (Table 7) in a similar way as obtained in the two-
fall at the border of the OVII emission region. Observation-
componentfit(Fig.5).
specificbadpixels(flaggedasbadchannelsinthespectrum)are
The basic parameters of the disk (e.g. the inclination angle,
automaticallytakenintoaccountwhencomputingtheinstrument
Table7)areinagreementwithwhatwasfoundfromtheFeKα response, but they may certainly cause additional uncertainty
linefitusingtheLaor (1991)model.Wenotehoweverthathere whenfittingnarrowfeatures.TheOVIIbroadlineis1.4A˚ wide
acomparisonisnotstraightforwardasinZycki&Czerny(1994)
and the determination of its flux is not significantly influenced
adisklinefromaSchwarzschild(ratherthanKerr)blackholeis
by bad pixels. Considering also the very significant, indepen-
included.
dent,detectionintheChandra-LETGSdata,wetreatthisfeature
4 The parameter s is a scaling factor for the reflected luminosity: asanintrinsically-low-fluxOVIIline.Thelinefluxmeasuredin
Ltot = Lpow +sLrefl.Foranisotropicsourceabovethedisks = 1, 2005isindeedweakerthanin2003(Sect.2.2),eventhoughthe
correspondingtoanequalcontributionfromdirectandreflectedspec- SEDof2005showsanincreasedavailabilityofopticalandUV
trum. photons(Fig.6).Suchabehaviorofthelineintensityishowever
8 E.Costantinietal.:XMM-NewtonobservationofMrk279
notunexpected,asthesinglelineluminositiesarealsosensitive (e.g. Sulenticetal. 1998; Nandra 2006). In at least one case,
tothelongtermfluxhistoryandtheshapeoftheSEDbothinthe (the LINER galaxy NGC 7213, Bianchietal. 2008) a simulta-
UVandX-rayband(atleastoftheprevioustwomonths,given neousoptical–X-rayobservationrevealedthesamewidthforthe
thetypicalsize ofthe BLR).TheX-raycontinuumofMrk279 Hα and FeKα lines, suggesting a common origin in the BLR.
has beenobservedto changein a monthtime-scale (Sect. 3.2), Howeverthe UV andX-raylinesmightcomein regionscloser
howevertheinformationonthelightcurveofMrk279issparse, totheblackholewithrespecttothelowerionizationlinesinthe
asthemostrecentobservationpriortotheXMM-Newtonpoint- optical,implyingalargerFWHM.MoreoverNGC7213canbe
inghasbeendonein2003(C07).Thereforeareconstructionof consideredanoutsiderobject,ashasbeenproventototallylack
the SED priorto the presentXMM-Newtonobservationcannot the reflection component (Bianchietal. 2003). Therefore a di-
beperformed.Inthisstudywefindthatonlyasmallfractionof rectcomparisonwithclassicalSeyfert1galaxies(asisMrk279)
thebroadFeKαlinecanbeproducedintheBLR.FromtheLOC maynotbepossible.
modelingwe find that the FeKα line luminosity,coming from
theBLR,shouldbeaboutsixtimessmallerthantheOVIItriplet.
ThistranslatesinacontributiontotheFeKαlinewhichisabout 4.3. TheoriginoftheFeKαline
30 times smaller than that observed, implying a 3% contribu-
Anyvariabilityoftheironlinewouldeasilysuggestaclosein-
tion. However, the elemental abundance close to a black hole,
teraction between the central source and the region producing
especiallyofiron,mightbedifferentfromSolar.Abundancesup
theironline,e.g.theaccretiondisk.Thelinedoesnotneedtobe
to 7 times Solar have been suggested (e.g. Fabianetal. 2002).
relativisticallysmeared,asalsoGaussian-shapedlinesmayarise
The same BLR model, but with the Fe abundance enhanced
fromtheaccretiondisk(Yaqoobetal.2003).UsingASCAdata
by a factor seven only reduces the OVII/FeKα luminosity ra-
Weaveretal. (2001)foundvariabilityinthelinecentroidatthe
tiotoabout4.5.However,suchanoverabundanceimpliesmuch
1.6σlevel(90%confidence).Thevariabilitywasobservedona
strongerX-rayironlinesfromtheL–Mshells,whicharenotob-
timescaleofabout20ksfollowinga2–10keVcentral-fluxvari-
served.IfweartificiallyconsidertheluminosityoftheFeKαas
ation of ∼15%. The average EW and FWHM as measured by
entirelyproducedin the BLR, we shouldobservean OVII line
withaluminosityaslargeas3×1042ergs−1,whichisclearly ASCAwerehoweverconsistentwiththepresentXMM-Newton
data.Overatimescaleofatleast3years,theFeKαlineare,in
inconsistent with both the present and archival measurements
firstapproximation,stableinluminosity,widthandcentroiden-
(C07). Moreover the NeIX and OVIII broad lines (with pre-
dictedluminosityofabout60×1040ergs−1)wouldbeclearly ergywithintheerrors(Table6).Towhichextentthelineisstable
isdifficulttoassess,assomemeasurementsareaffectedbylarge
visibleinthespectrum,againsttheobservationalevidence.The
uncertainties.Formally,thelinecouldhavechangedofasmuch
same discrepancyapplies if we consider the very broad profile
as a factor of two or more in luminosity. In a scenario where
of the FeKα line as arising from the BLR (Sect. 2.2). In that
a dominantcomponentof the line doesnotrespondto the cen-
case,theBLRcontributionwouldbe23timessmallerthanob-
tral source variation, an origin of the iron line in the accretion
served.Theunresolvedcomponentofthe FeKα wouldinstead
disk can be justified by light-bending (e.g. Fabian&Vaughan
beabout6timessmaller.Ifthiswerethecase,thecontribution
2003;Galloetal.2007).Inthatcasetheapparentfluxisallowed
oftheBLRtotheFeKαlinewouldnotbenegligible(∼ 16%).
tochangeevenofa largefactor(upto four)while theline-flux
However,theFWHMofthecoreoftheFeKαline,asmeasured
byChandra-HETGSis4200+3350kms−1(Nandra2006),which change is marginal (Miniuttietal. 2003). A number of factors
−2950 mayinfluencetheironlinebehavior.Thelimitedknowledgeof
is inconsistent with the FWHM of the UV lines (Gabeletal.
the exact nature of the emission components (both FeKα line
2005).Moreover,BLRlinearesubjectedtosignificantvariabil-
andcontinuum)inthissourcedoesnotallowustomakepredic-
ity both in the UV (e.g., Goad&Koratkar1998) and in the X-
tions on the variation of the line in response to the continuum
rays(Steenbruggeetal.2009,andpresentwork),whilewecould
changesoneithershortorlongtimescales.
notdetectanysignificantchangeintheironlineflux,measured
A symmetric line profile, possibly constant over a long time
inafewoccasionsbydifferentinstruments(Sect.3.2).Thisalso
scale, may also suggest a relatively unperturbed environment,
supportstheideathattheBLRcontributionshouldbeminimal.
likeforexamplethemoleculartorus,∼1pcawayfromthecen-
AnimportantnoteisthattheBLRparametersofMrk279were
tral source. In the framework of the unification model (e.g.
determinedfirstusingUVdataonly(seeC07andSect.3.1)and
Antonucci 1993), the iron line is a natural consequence of the
then applied to the X-ray data. With this approach, any X-ray
obscuringtorus.Intype1objects,theexpectedequivalentwidth
lineonlyprovidesusefulupperlimits,withintherangeimposed
would be of the order of 100eV. However geometrical effects
alreadybytheC value,onthenormalizationoftheLOCmodel
V would easily reduce it of a factor of two (Nandraetal. 2007;
(Fig.7).Therefore,inprinciple,givenaBLRmodelandanSED,
Krolik&Kallman1987).InthecaseofMrk279,theEWofthe
thecontributionoftheBLRtotheFeKαlinecanbecalculated
narrowironlineis70±15eV,inagreementwiththetheoretical
withoutthesupportofotherX-raylines.Asatest,wealsopre-
prediction. The presence of FeKβ, insures that the ionization
dicted the iron line luminosity considering the SED and BLR
parametersderivedforthe2003dataset.Inthatcase,reminding stateofironislessthanFeXVII (Yaqoobetal.2007).Afurther
constraintontheionizationstateofironwouldbebasedonthe
thatwedonothaveanysimultaneousmeasurementoftheFeKα
line in 2003, the contribution of the BLR to the line would be FeKα/FeKβ branching ratio, which rangesfrom 0.12 for FeI
roughly17%. upto0.17forFeIX(Palmerietal.2003).Unfortunately,consid-
eringtheassociatederrorsontheobservedlinefluxes,we only
Here for the first time we have tested the connection be-
obtainalowerlimitof0.1tothatratio.
tween the optical BLR and the FeKα line, using the intrinsic
luminosity of the lines (rather than the FWHM) and relying
on a possible physical model for the BLR (The LOC model, 4.4. ThenatureoftheFeXXVIline
Baldwinetal. 1995). The idea of a non-relation between the
BLRandtheFeKαlinehasbeenalreadytestedcomparingthe He-like,sometimesassociatedwithH-like,ironlineshavebeen
width of the optical broad lines with the width of FeKα line detectedinanumberofAGNspectra.Theselinescanbeassoci-
E.Costantinietal.:XMM-NewtonobservationofMrk279 9
atedtohighcolumndensity,photoionizedgas(Longinottietal. The very broad componentof the FeKα line may be modeled
2007;Bianchietal.2005,andreferencestherein).Thespectrum by a line arising from an accretion disk, associated with
ofMrk279doesexhibitanarrowemissionlineat∼6.9keV,con- relativistically smeared reflection. However, a formal fit using
sistent with emission from FeXXVI, but interestingly FeXXV broad-band reflection models is affected by large uncertainties
is not detected, showing the presence of extremely highly ion- and degeneracy of the parameters, as we cannot access the
ized gas. Interpreting this emission as a product of photoion- region above 10keV and we only have to rely on the FeKα
ization,wefindthatahighcolumn-density(NH ∼ 1023cm−2) profile,whichisinturnformedbytwoline-components.
with a very-highionization parameter(logξ ∼ 6) is necessary.
A rangeof NH andlogξ andcoveringfactorsis allowed to ex- We also detected emission from FeXXVI, but not from
plain the FeXXVI emission and at the same time be consistent FeXXV. This implies an extremely highly ionized medium.
withthemeasuredupperlimitsontheotherhighionizationlines: Usingtheavailableconstraintsonotherhighlyionizedions(e.g.
FeXXV, NeX andOVIII (see Sect. 3.3and Fig. 9). Thecover- NeX, OVIII and NVII) we could limit the column density of
ing factor is on average 0.65. As we do not see any associated such gas 1022 < NH < 5 ×1023cm−2 with an increasingly
absorption, this gas must be out of our line of sight. The EW higher ionization parameter 5.3 < logξ < 7. The covering
of the FeXXVI line (12±5eV) is consistent with an origin in factor of the gas is 0.65 on average. Such a gas is predicted
photoionizedcircumnucleargasatthedistanceoftheobscuring by the AGN unification model, and it could be associated
torus(Bianchi&Matt2002).Thetorusitselfwouldproducethe with a highly ionized outer layer of the obscuring torus (e.g.
bulkoftheneutral-weaklyionizedironemission,whileahighly Krolik&Kallman1987).
ionizedouterlayerofphotoionizedgaswouldberesponsiblefor
H-likeandHe-likeiron.Inourcasethegasissoionizedtosup-
pressevenFeXXV. Acknowledgements. The Space Research Organization of the Netherlands is
Another possibility is that the FeXXVI line is formed in a hot supported financially by NWO, the Netherlands Organization for Scientific
galactic wind, driven by starburst activity (Chevalier&Clegg Research.
1985).However,averyhot(logE∼9–10keV)plasmawouldbe
neededtoproducetheobservedFeXXVIlineluminosityviacol-
lisionalionization.Suchhightemperatureshavebeenproposed References
for exampleforthe diffuseemission of the Galactic ridge (e.g.
Anders,E.,&Grevesse,N.1989,Geochim.Cosmochim.Acta,53,197
Tanaka 2002). However,this interpretationis problematic with
Antonucci,R.R.J.,&Miller,J.S.1985,ApJ,297,621
respecttotheconfinementoftheplasmawithinthehostgalaxy, Antonucci,R.1993,ARA&A,31,473
thesourceofsuchheat(e.g.Masaietal.2002)andthecontam- Baldwin,J.,Ferland,G.,Korista,K.,&Verner,D.1995,ApJ,455,L119
inationbypoint-like,hardsourcesinthediffuseemissionspec- Bianchi,S.,&Matt,G.2002,A&A,387,76
Bianchi,S.,Matt,G.,Balestra,I.,&Perola,G.C.2003,A&A,407,L21
trum(e.g.inNGC253,Stricklandetal. 2002).Anotherwayto
Bianchi,S.,Matt,G.,Nicastro,F.,Porquet,D.,&Dubau,J.2005,MNRAS,357,
modelthehighionizationspectrumintermsofagalacticwind, 599
is to invokequasi-thermalacceleration of electronswhich then Bianchi, S., La Franca, F., Matt, G., Guainazzi, M., Jimenez Bailo´n, E.,
wouldproduceX-rayswiththermalphotons.Ironlineswouldbe Longinotti,A.L.,Nicastro,F.,&Pentericci,L.2008,MNRAS,389,L52
Branduardi-Raymont,G.,Sako,M.,Kahn,S.M.,etal.,2001,A&A365,L140
producedbyrecombinationofbackgroundironionsrecapturing
Chevalier,R.A.,&Clegg,A.W.1985,Nature,317,44
electrons, as proposed by Masaietal. (2002) for the Galactic
Costantini,E.,etal.2007,A&A,461,121(C07)
ridgeemission. Crenshaw,D.M.,Kraemer,S.B.,&George,I.M.2003,ARA&A,41,117
deVries,C.P.,denHerder,J.W.,Kaastra,J.S.,Paerels,F.B.,denBoggende,
A.J.,&Rasmussen,A.P.2003,A&A,404,959
5. Conclusions Elvis,M.,Wilkes,B.J.,&Lockman,F.J.1989,AJ,97,777
Fabian, A. C., Ballantyne, D. R., Merloni, A., Vaughan, S., Iwasawa, K., &
We have performed a detailed modeling of the spectrum of Boller,T.2002,MNRAS,331,L35
Mrk 279, observed for ∼ 160ks by XMM-Newton. Thanks to Fabian,A.C.,&Vaughan,S.2003,MNRAS,340,L28
Ferland,G.J.2004,AmericanAstronomicalSocietyMeetingAbstracts,205,
thebroadbandcoveragewehadtheopportunitytostudyinde-
Gallo, L. C., Brandt, W. N., Costantini, E., Fabian, A. C., Iwasawa, K., &
tailboththe low-energyemissionlines(observedbyRGS)and
Papadakis,I.E.2007,MNRAS,377,391
theironKcomplexataround6.4keV(observedbyEpic). Gabel,J.R.,etal.2005,ApJ,623,85
We have extended the “locally optimally emitting cloud” George,I.M.,&Fabian,A.C.1991,MNRAS,249,352
model,which hasbeenconceivedto modelthe UV broadlines Ghisellini,G.,Haardt,F.,&Matt,G.1994,MNRAS,267,743
Goad,M.,&Koratkar,A.1998,ApJ,495,718
coming from the BLR (Baldwinetal. 1995), first to the soft
Jime´nez-Bailo´n, E., Piconcelli, E., Guainazzi, M., Schartel, N., Rodr´ıguez-
X-ray band (C07) and, in the present paper, to the FeKα line. Pascual,P.M.,&Santos-Lleo´,M.2005,A&A,435,449
TheBLRcaneasilyaccountfortheOVIIbroademission(C07), Kaastra,J.S.,&Barr,P.1989,A&A,226,59
while it contributes marginally to the luminosity of the broad Kaastra, J. S., Steenbrugge, K. C., Raassen, A. J. J., van der Meer, R. L. J.,
Brinkman,A.C.,Liedahl,D.A.,Behar,E.,&deRosa,A.2002,A&A,386,
iron line at 6.4keV (about 3%, this work). This is the first
427
attempt to evaluate the BLR contribution to the luminosity of
Kaastra,J.S.,etal.2004,A&A,428,57
theironlineusingaglobalmodeling(ratherthanrelyingonthe Korista,K.,Baldwin,J.,Ferland,G.,&Verner,D.1997,ApJS,108,401
lineFWHMonly).Furtherinvestigationonhighqualitydataof Korista,K.T.,&Goad,M.R.2000,ApJ,536,284
similarsourcesareofcoursenecessarytotesttherobustnessof Krolik,J.H.,&Kallman,T.R.1987,ApJ,320,L5
Krolik,J.H.,Madau,P.,&Zycki,P.T.1994,ApJ,420,L57
ourresults.
Krolik,J.H.,&Kriss,G.A.1995,ApJ,447,512
Laor,A.,1991,ApJ376,90
The bulk of the FeKα narrow emission line shows no Longinotti, A. L., Bianchi, S., Santos-Lleo, M., Rodr´ıguez-Pascual, P.,
remarkablevariability,influxandshapeoveratleastthreeyears Guainazzi,M.,Cardaci,M.,&Pollock,A.M.T.2007,A&A,470,73
Masai,K.,Dogiel,V.A.,Inoue,H.,Scho¨nfelder,V.,&Strong,A.W.2002,ApJ,
(Sect. 3.2) and it may be produced by reflection from distant
581,1071
andcoldmatter.TheEWoftheline(∼70eV)isalsoconsistent
Magdziarz,P.,&Zdziarski,A.A.1995,MNRAS,273,837
withthispicture. Matt,G.,Perola,G.C.,&Piro,L.1991,A&A,247,25
10 E.Costantinietal.:XMM-NewtonobservationofMrk279
Miniutti,G.,Fabian,A.C.,Goyder,R.,&Lasenby,A.N.2003,MNRAS,344,
L22
Nandra,K.2006,MNRAS,368,L62
Nandra,K.,O’Neill,P.M.,George,I.M.,&Reeves,J.N.2007,MNRAS,382,
194
Ogle,P.M.,Mason,K.O.,Page,M.J.,Salvi,N.J.,Cordova,F.A.,McHardy,
I.M.,&Priedhorsky,W.C.2004,ApJ,606,151
Palmeri,P.,Mendoza,C.,Kallman,T.R.,Bautista,M.A.,&Mele´ndez,M.2003,
A&A,410,359
Peterson,B.M.1993,PASP,105,247
Pounds,K.A.,Reeves,J.N.,King,A.R.,&Page,K.L.2004,MNRAS,350,10
Protassov,R.,vanDyk,D.A.,Connors,A.,Kashyap,V.L.,&Siemiginowska,
A.2002,ApJ,571,545
Reynolds,C.S.,&Nowak,M.A.2003,Phys.Rep.,377,389
Scott,J.E.,etal.2004,ApJS,152,1
Steenbrugge,K.C.,etal.2005,A&A,434,569
Steenbrugge,K.C.,Fenovcˇ´ık,M.,Kaastra,J.S.,Costantini,E.,&Verbunt,F.
2009,A&A,496,107
Strickland,D.K.,Heckman,T.M.,Weaver,K.A.,Hoopes,C.G.,&Dahlem,
M.2002,ApJ,568,689
Sulentic, J. W., Marziani, P., Zwitter, T., Calvani, M., & Dultzin-Hacyan, D.
1998,ApJ,501,54
Tanaka,Y.,etal.1995,Nature,375,659
Tanaka,Y.2002,A&A,382,1052
Weaver,K.A.,Gelbord,J.,&Yaqoob,T.2001,ApJ,550,261
Williams,R.J.,Mathur,S.,&Nicastro,F.2006,ApJ,645,179
Wilms,J.,Reynolds,C.S.,Begelman,M.C.,Reeves,J.,Molendi,S.,Staubert,
R.,&Kendziorra,E.2001,MNRAS,328,L27
Yaqoob,T.,&Padmanabhan,U.2004,ApJ,604,63
Yaqoob,T.,George,I.M.,Kallman,T.R.,Padmanabhan,U.,Weaver,K.A.,&
Turner,T.J.2003,ApJ,596,85
Yaqoob,T.,etal.2007,PASJ,59,283
Young, A. J., Lee, J. C., Fabian, A. C., Reynolds, C. S., Gibson, R. R., &
Canizares,C.R.2005,ApJ,631,733
Zycki,P.T.,Done,C.,&Smith,D.A.1999,MNRAS,305,231
Zycki,P.T.,&Czerny,B.1994,MNRAS,266,653