Anatomy of the AGN in NGC 5548: II. The Spatial, Temporal and Physical Nature of the Outflow ...

40 Pages·2014·2.48 MB·English

Astronomy&Astrophysicsmanuscriptno.NGC5548UV (cid:13)c ESO2014
November11,2014
Anatomy of the AGN in NGC 5548: II. The Spatial, Temporal
and Physical Nature of the Outflow from HST/COS Observations
N.Arav1,C.Chamberlain1,G.A.Kriss2,3,J.S.Kaastra4,5,M.Cappi6,M.Mehdipour4,7,P.-O.Petrucci8,9,K.C.
Steenbrugge10,11,E.Behar12,S.Bianchi13,R.Boissay14,G.Branduardi-Raymont7,E.Costantini4,J.C.Ely2,J.Ebrero4,
L.diGesu4,F.A.Harrison15,S.Kaspi12,J.Malzac16,17,B.DeMarco18,G.Matt13,K.P.Nandra18,S.Paltani14,
B.M.Peterson19,20,C.Pinto21,G.Ponti18,F.PozoNun˜ez22,A.DeRosa23,H.Seta24,F.Ursini8,9,C.P.deVries4,
D.J.Walton15,andM.Whewell7
4
1 1 DepartmentofPhysics,VirginiaTech,Blacksburg,VA24061,USA.
0 2 SpaceTelescopeScienceInstitute,3700SanMartinDrive,Baltimore,MD21218,USA.
2 3 DepartmentofPhysicsandAstronomy,TheJohnsHopkinsUniversity,Baltimore,MD21218,USA.
4 SRONNetherlandsInstituteforSpaceResearch,Sorbonnelaan2,3584CAUtrecht,theNetherlands.
v
5 LeidenObservatory,LeidenUniversity,PostOfficeBox9513,2300RALeiden,Netherlands.
o
6 INAF-IASFBologna,ViaGobetti101,I-40129Bologna,Italy.
N
7 MullardSpaceScienceLaboratory,UniversityCollegeLondon,HolmburySt.Mary,Dorking,Surrey,RH56NT,UK.
8 Univ.GrenobleAlpes,IPAG,F-38000Grenoble,France.
8
9 CNRS,IPAG,F-38000Grenoble,France.

10 InstitutodeAstronom´ıa,UniversidadCato´licadelNorte,AvenidaAngamos0610,Casilla1280,Antofagasta,Chile.
]
A 11 DepartmentofPhysics,UniversityofOxford,KebleRoad,Oxford,OX13RH,UK.
12 DepartmentofPhysics,Technion-IsraelInstituteofTechnology,32000Haifa,Israel.
G
13 DipartimentodiMatematicaeFisica,Universita`degliStudiRomaTre,viadellaVascaNavale84,00146Roma,Italy.
. 14 DepartmentofAstronomy,UniversityofGeneva,16Ch.d’Ecogia,1290Versoix,Switzerland.
h
15 CahillCenterforAstronomyandAstrophysics,CaliforniaInstituteofTechnology,Pasadena,CA91125,USA.
p
16 Universite´deToulouse,UPS-OMP,IRAP,Toulouse,France.
-
o 17 CNRS,IRAP,9Av.colonelRoche,BP44346,31028ToulouseCedex4,France.
r 18 Max-Planck-Institutfu¨rextraterrestrischePhysik,Giessenbachstrasse,D-85748Garching,Germany.
t 19 DepartmentofAstronomy,TheOhioStateUniversity,140W18thAvenue,Columbus,OH43210,USA.
s
a 20 CenterforCosmology &AstroParticlePhysics,TheOhioStateUniversity,191WestWoodruff Avenue, Columbus,OH43210,
[ USA.
21 InstituteofAstronomy,UniversityofCambridge,MadingleyRd,Cambridge,CB30HA,UK.
1 22 AstronomischesInstitut,Ruhr-Universita¨tBochum,Universita¨tsstraße150,44801,Bochum,Germany.
v 23 INAF/IAPS-ViaFossodelCavaliere100,I-00133Roma,Italy.
7 24 ResearchCenterforMeasurementinAdvancedScience,FacultyofScience,RikkyoUniversity3-34-1Nishi-Ikebukuro,Toshima-
5 ku,Tokyo,Japan.
1
2 November11,2014
.
1
ABSTRACT
1
4
Context.AGNoutflowsarethoughttoinfluencetheevolutionoftheirhostgalaxiesandsupermassiveblackholes.Ourdeepmul-
1
tiwavelengthcampaignonNGC5548revealedanunusuallystrongX-rayobscuration. Theresultingdramaticdecreaseinincident
:
v ionizingfluxontheoutflow,allowedustoconstructacomprehensivephysical,spatialandtemporalpictureforthelong-studiedAGN
i windinthisobject.
X
Aims.Todeterminethedistanceoftheoutflowingcomponentsfromthecentralsource;theirtotalcolumndensityandthemechanism
r responsiblefortheobservedabsorptiontroughvariability.
a Methods.WestudytheUVspectraacquiredduringthecampaignaswellasfromfourpreviousepochs,wheretheoutflowsarede-
tectedasblue-shiftedabsorptiontroughsinthespectraoftheobject.Ourprincipalanalysistoolsareioniccolumndensityextraction
techniques,photoinizationmodelsbasedonthecodeCLOUDY,andcollisionalexcitationsimulations.
Results.Asimplemodelbasedonafixedtotalcolumn-densityabsorber,reactingtochangesinionizingillumination,matchesthe
verydifferentionizationstatesseeninfivespectroscopicepochsspanning16years.Themainoutflowcomponentissituatedat3.5±1
pcfromthecentralsource.Threeothercomponentsaresituatedbetween5-70pcandtwoarefurtherthan100pc.Thewealthofob-
servationalconstraintsandthedisparaterelationshipoftheobservedX-rayandUVfluxbetweendifferentepochsmakeourphysical
modelaleadingcontenderforinterpretingtroughvariabilitydataofquasaroutflows.
Conclusions.Thiscampaign,incombinationwithpriordata,yieldsthefirstsimplemodelthatcanexplainthephysicalcharacteristics
andthesubstantialvariabilityobservedinanAGNoutflow.
Keywords.galaxies:Seyfert–galaxies:active–X-rays:galaxies
1
1. Introduction HST observationsofNGC5548thatare alsoused inthisanal-
ysis. The five observationsfrom the summer of 2013 were op-
AGN outflows are detected as blueshifted absorption troughs,
timally weighted to produce an average spectrum that we use
with respect to the object systemic redshift. Such outflows
for our analysis. Kaastraetal. (2014) describe the data reduc-
in powerful quasars can expel sufficient gas from their host
tionprocessfromthecalibrationofthedatatotheproductionof
galaxies to halt star formation, limit their growth and lead to
thisaveragespectrum.
the co-evolution of the size of the host and the mass of its
The2013averageHST/COSspectrumwithallidentifiedab-
central super massive black holes (e.g., Ostrikeretal. 2010;
sorptionfeaturesisshowninFigureA1.AsdescribedinKaastra
Hopkins&Elvis2010;Soker&Meiron2011;Ciottietal.2010;
etal.(2014),wemodeledtheemissionfromNGC5548usinga
Faucher-Gigue`reetal. 2012; Borguetetal. 2013; Aravetal.
reddenedpowerlaw(withextinctionfixedatE(B−V) = 0.02,
2013). Therefore, deciphering the properties of AGN outflows
Schlegeletal. 1998), weak Feii emission longward of 1550 Å
iscrucialfortestingtheirroleingalaxyevolution.
intherestframe,broadandnarrowemissionlinesmodeledwith
Nearby bright AGN are excellent laboratories for study-
severalGaussiancomponents,blue-shiftedbroadabsorptionon
ing these outflows as they yield: a) high-resolution UV data,
all permitted transitions in NGC 5548, and a Galactic damped
which allow us to study the outflow kinematics and can yield
Lyα absorption line. Using this emission model, we normal-
diagnostics for their distance from the central source; and b)
ized the average spectrum to facilitate our analysis of the nar-
high quality X-ray spectra that give the physical conditions
rowintrinsicabsorptionlinesinNGC5548.Figure1showsnor-
for the bulk of the outflowingmaterial (e.g., Steenbruggeetal.
malized spectra for absorption lines produced by Siiii λ1206,
2005;Gabeletal.2005;Aravetal.2007;Costantinietal.2007;
Siiv λλ1394,1403, Civ λλ1548,1550, Nv λλ1238,1242, and
Kaastraetal.2012).Thus,suchobservationsareavitalstepping
Ly α as a functionof rest-framevelocity relative to a systemic
stone for quantifying outflows from the luminous (but distant)
redshift of z = 0.017175 (deVaucouleursetal. 1991) via the
quasars,forwhichhighqualityX-raydataarenotavailable.
NASA/IPACExtragalacticDatabase(NED).
Forthesereasons,weembarkedonadeepmultiwavelength
AsshowninTableA.1,high-resolutionUVspectraofNGC
campaign on the prototypical AGN outflow seen in the inten-
5548usingHSTcoveranadditionalfourepochsstretchingback
sively studied Seyfert 1 galaxy NGC 5548. For the past 16
to 1998. We use the calibrated data sets for each of these ob-
years, this outflow has shown 6 kinematic components in the
servations as obtained from the Mikulski Archive for Space
UV band (labeled in descending order of velocity, following
Telescopes (MAST) at the Space Telescope Science Institute
Crenshawetal.2003),andtheirassociatedX-raywarmabsorber
(STScI). We compare the strengths of the narrow UV absorp-
(WA). Our 2013 campaign revealed a new X-ray obscurer ac-
tiontroughsforeachoftheseepochswithournewdatasetfrom
companied by broad UV absorption (analyzed in Kaastraetal.
2013inFigs.A2andA3.
2014).Theappearanceoftheobscurerallowsustoderiveacom-
prehensive physical picture of the long-term observed outflow,
whichwereporthere.
3. Physicalandtemporalcharacteristicsof
The plan of the paper is as follows: In § 2 we describe the
Component1
observationsanddatareduction;in§ 3weanalyzethekeycom-
ponentof the outflow;in § 4 we discuss the remaining5 com- The key for building a coherent picture of the long-seen out-
ponents;in § 5 we connectthe results of the UV analysis with flow is component 1: the strongest and highest velocity out-
thoseoftheX-raywarmabsorberofthesameoutflow;andin§6 flow component(centeredat−1160km s−1). Dueto the strong
wecompareourresultswithpreviousstudies,discusstheimpli- suppressionof incidentionizing flux by the obscurer,the 2013
cation of our results to the variability of AGN outflow troughs HST/COS data of component 1 show a wealth of absorption
in general, and elaborate on the connection between the X-ray troughsfromionsneverbeforeobservedintheNGC5548out-
obscurer and the persisting outflow; In § 7 we summarize our flow. These data allow us to decipher the physical characteris-
results. ticsofthiscomponent.In§3.1weusethecolumndensitymea-
surementsofPv,Piii,Feiii,andSiiiasinputinphotoionization
models,andderivethetotalhydrogencolumndensityforcom-
2. ObservationsandDataReduction ponent1oflog(N ) = 21.5+0.4 cm−2,andanionizationparam-
H −0.2
Our 2013 multiwavelength campaign on NGC 5548 included eteroflog(UH) = −1.5+−00..42.In§3.2weusethecolumndensity
coordinated observations using XMM-Newton, HST, Swift, measurements of Ciii* and Siiii* to infer the electron number
INTEGRAL, and NuSTAR. Kaastraetal. (2014) describe the densitylog(ne)=4.8±0.1cm−3,whichcombinedwiththevalue
overall structure of the campaign. A full log of all the obser- oftheincidentUH yieldsadistanceR=3.5±1parsecbetween
vations is given by Mehdipouretal (2014). Here we present a component1andthecentralsource.In§3.3weconstructasim-
moredetailedanalysisoftheUVobservationsweobtainedusing plemodelbasedonafixedtotalcolumn-densityabsorber,react-
theCosmicOriginsSpectrograph(COS)(Greenetal.2012)on- ing to changes in ionizing illumination, that matches the very
boardHST.We obtainedfiveCOSobservationssimultaneously differentionizationstatesseeninfiveHSThigh-resolutionspec-
with five of the XMM-Newton observationsbetween 2013-06- troscopicepochsspanning16years.
22 and 2013-08-01. Each two-orbit observation used gratings
G130MandG160Matmultiplecentralwavelengthsettingsand
3.1.TotalColumnDensity(N )andIonizationParameter
H
multiplefocal-planepositions(FP-POS)tocoverthewavelength
(U )
H
rangefrom1132Åto1801Åataresolvingpowerof∼15,000.
TableA.1liststheobservationdatesoftheindividualvisits,the In the Appendix we describe the methods we use to derive
exposuretimes, andthecontinuumfluxmeasuredat1350Å in the ionic column densities (Nion) from the outflow absorption
therestframe,aswellascorrespondinginformationforarchival troughs. Table 2 gives the Nion measurements for all observed
troughsofall6outflowcomponentsinthe5HSTepochs(span-
Sendoffprintrequeststo:[email protected] ning 16 years) of high-resolution UV spectroscopy. The upper
N.Aravetal.:NGC5548
Fig.2.TheadoptedNGC5548SEDs.InblackweshowtheSED
for NGC 5548 in 2002 at an unobscured X-ray flux (hereafter
“highSED,”fromSteenbruggeetal.2005).Inblueweshowthe
SED appropriateto the 2013epoch,whereforthesame fluxat
1000 Å, the new X-ray obscurer reduced the ionizing flux by
a factor of 17 between 1 Ry and 1 keV (obscured SED). The
ionization potentials for destruction of some of the prominent
observedspeciesareshownbytheverticallines.
the “obscured”SED in Figure 2, and furtherjustify its specific
shape in § 3.3 For abundances, we use pure proto-Solar abun-
dancesgivenbyLoddersetal.(2009).
WiththechoiceofSEDandchemicalabundances,twomain
Fig.1.Intrinsicabsorptionfeaturesinthe2013COSspectrumof
parametersgovernthephotoionizationstructureoftheabsorber:
NGC5548.Normalizedrelativefluxesareplottedasafunction
the total hydrogencolumn density (N ) and the ionization pa-
ofvelocityrelativetothesystemicredshiftofz=0.017175,top H
to bottom: Siiii λ1206, Siiv λλ1394,1403,Civ λλ1548,1550, rameter
Nv λλ1238,1242,andLy α, as a functionofrest-frameveloc- Q
U ≡ H (1)
ity.Forthedoubletsthe redandbluecomponentsareshownin H 4πR2n c
redandblue,respectively.Dottedverticallinesindicatetheve- H
locitiesoftheabsorptioncomponentsnumberedasinCrenshaw where QH is the rate of hydrogen-ionizingphotons emitted by
etal.(2003). the object, c is the speed of light, R is the distance from the
centralsourcetotheabsorberandn isthetotalhydrogennum-
H
berdensity.Wemodelthephotoionizationstructureandpredict
the resulting ionic column densities by self-consistently solv-
andlowerlimitswerederivedusingtheApparentOpticalDepth ing the ionization and thermal balance equations with version
(AOD)method.Allthereportedmeasurementsweredoneusing 13.01 of the spectral synthesis code Cloudy, last described in
thePartialCovering(PC)method.WeusedthePower-Law(PL) Ferlandetal.(2013).Weassumeaplane-parallelgeometryfora
methodonlyontheCiii*inordertoquantifythesystematicer- gasofconstantn .
rorduetodifferentmeasuringmethods(see§3.2andFig.4). TofindthepaHirof(U ,N )thatbestpredictsthesetofob-
H H
TheNionwemeasurearearesultoftheionizationstructureof served column densities, we vary UH and NH in 0.1 dex steps
theoutflowingmaterial,andcanbecomparedtophotoionization to generate a grid of models (followingthe same approachde-
models to determine the physicalcharacteristics of the absorb- scribedinBorguetetal.2012b)andperformaminimizationof
ing gas. As boundary conditions for the photoionization mod- thefunction
els, we need to specify the choice of incident Spectral Energy
Distribution(SED),andthechemicalabundancesoftheoutflow- χ2 = log(Ni,mod)−log(Ni,obs) 2 (2)
inggas. log(N )−log N ±σ !
Wemakethesimple(andprobablyover-restrictive)assump- Xi i,obs i,obs i
(cid:0) (cid:1)
tion that the shape of the SED emitted from the accretion disk where,forioni, N andN aretheobservedandmodeled
i,obs i,mod
did not change over the 16 years of high-resolution UV spec- columndensities,respectively,andσ istheerrorintheobserved
i
troscopy.Specifically,we assume that the emittedSED hasthe columndensity.Themeasurementerrorsarenotsymmetric.We
sameshapeithadwhenweobtainedsimultaneousX-ray/UVob- use the positive error (+σ) when log(N ) > log(N ) and
i i,mod i,obs
servationsin2002(the “high”SED in Figure2, determinedby thenegativeerror(−σ)whenlog(N )<log(N ).
i i,mod i,obs
Steenbruggeetal. 2005). In 2013 the obscurer absorbed much Theionizationsolutionforcomponent1atthe2013epochis
ofthesoftionizingphotonfluxfromthisSEDbeforeitreached showninfigure3.WeonlyshowconstraintsfromN measure-
ion
component 1. We model the incident SED on component 1 as ments,andnotethatallthelowerlimitsreportedinTable2are
3
N.Aravetal.:NGC5548
FeIII
22
N ) H PV
g (
o
L
PIII
21
SiII
-2 -1 0
Log (U )
H
Fig.3.A photoionizationphaseplotshowingtheionizationso-
lution for component1 epoch2013.We use the obscuredSED
andassumedproto-solarmetalicity(Loddersetal. 2009).Solid
linesandassociatedcoloredbandsrepresentthelocusofU ,N
H H
models, which predict the measured N , and their 1σ uncer-
ion
tainties.Theblackdotisthebestsolutionandissurroundedby
a1σ χ2contour.
satisfiedbythissolution.Wefindlog(N ) = 21.5+0.4cm−2,and
H −0.2
anionizationparameteroflog(U )=−1.5+0.4,wheretheerrors
H −0.2
arestronglycorrelatedasillustratedbythe1σχ2contour.
3.2.NumberDensityandDistance
As shown in Figure 4, we detect absorption troughs from the
Ciii* 1175 Å multiplet, arising from the metastable 3P levels
j
ofthe2s2pterm.AsdetailedinGabeletal.(2005),theexcited
Ciii* 1175Å multipletcomprisessix linesarisingfromthreeJ
levels. The J=0 and J=2 levels have significantly lower radia-
tivetransitionprobabilitiestothegroundstatethantheJ=1level
and are thus populated at much lower densities than the latter.
In particular, figure 5 in Borguetetal. (2012a) shows that the
relative populations of the three levels are a sensitive probe to
a wide range of n while being insensitive to temperature.The
e
twohigh-S/NtroughsfromtheJ=2levelallowustoaccurately
accountforthemildsaturationinthesetroughsandthereforeto
derivereliableN forbothlevels.Fromthesemeasurementswe
ion
inferlog(n ) = 4.8±0.1cm−3 (see Fig.4).We alsodetecttwo
e
shallow troughs from the same metastable level of Siiii* (see
panelbofFig.4),whichweusetomeasureanindependentand
consistent value for ne (see panel c of Fig. 4). The collisional Fig.4. a)AbsorptionspectrumfortheCiii* 1175Å multiplet.
excitationsimulationsshowninFigure4cwereperformedusing
The 2013 COS spectrum shows clear and relatively unblended
version7.1.3ofCHIANTI(Dereetal.1997;Landietal.2013),
individualtroughsfromtheJ=2andJ=0levels,butnocontribu-
withatemperatureof10,000K(similartothepredictedtemper-
tionfromtheJ=1levelthatispopulatedathigherdensities(see
atureofourCLOUDYmodelforcomponent1duringthe2013
panelc).b)AbsorptionspectrumfortheSiiii*1298Åmultiplet
epoch).
(similar in level structure to the Ciii* 1175 Å multiplet). The
In addition to the Ciii* and Siiii* troughs, the 2013 COS
2013COS spectrum shows shallow but highlysignificant indi-
spectraofcomponent1showseveraladditionaltroughsfromex-
vidualtroughsfromtheJ=2andJ=0levels,butagainnocontri-
citedstates:Cii*, Siii*,Piii*, Siii* andFeiii* (aswellastheir
bution from the J=1 level that is populated at higher densities.
associatedresonancetransitions).Carefulmeasurementofthose
c) Ciii* andSiiii* levelpopulationratios, theoryandmeasure-
troughsshowthatinthesecases,thededucedn isalowerlimit
e ments.ThecomputedpopulationsfortheJ=2/J=0andJ=1/J=0
thatislargerthanthecriticaldensityoftheinvolvedexcitedand
areplottedasafunctionofelectronnumberdensityforbothions
zero energy levels. In all cases the critical densities are below
(seetextforelaboration).Thecrossesshowthemeasuredratios
fortheJ=2/J=0ratioofbothions.FromtheCiii*ratiosweinfer
4 log(ne) = 4.8±0.1cm−3,wheretheerrorincludesbothstatisti-
calandsystematiceffects.Thisvalueisfullyconsistentwiththe
oneinferredfromtheSiiii*ratio,whereinthecaseofSiiii*the
statisticalerrorislargersincethetroughsaremuchshallower.
N.Aravetal.:NGC5548
log(n ) = 4.8 cm−3, thus they are consistent with the n mea- ualintensityofthecomponent1Civtroughcannotbeattributed
e e
surementwederivefromtheCiii*andSiiii*troughs. to new materialappearingdue to transverse motionat this dis-
As can be seen from the definition of the ionization pa- tance.Wenotethat25%motionacrosstheprojectedsizeofthe
rameter U (Equation 1), knowledge of the hydrogen number Civ BLR is a highly conservative limit for two reasons: 1) at
H
density n for a given U and N allows us to derive the dis- certainvelocitiestherearechangesof50%intheresidualinten-
tance R. OHur photoionizaHtionmodHels show that for component sityinthecomponent1Civtroughbetweenthe2011and2013
1,log(U )=−1.5andsincen ≃1.2n (asisthecaseforhighly epochs;andintheelapsing2years,transversemotionwillonly
ionizedpHlasma),n =5.3×10e4cm−3.HTodeterminetheQ that cover3%oftheprojectedsizeoftheCivBLR;2)materialthat
H H
affectscomponent1, wefirstcalculatethe bolometricluminos- movesawayfromthecentralsourceundertheinfluenceofradial
ity using the average flux at 1350Å for visits 1-5 in 2013, the forces should conserve its angular momentum. Therefore, if it
redshift of the object and the obscured SED (see Fig. 2). We movedtodistancesthataremuchlargercomparedwithitsinitial
find Lbol = 2.6 × 1044 erg s−1 and from it, QH = 6.9 × 1052 distance,itsv⊥ ≪ vkep atitscurrentdistance.Weconcludethat
s−1.Therefore,equation(1)yieldsR = 3.5+1.0pc,wheretheer- evenunderfavorableconditions,thetransversemotionmodelof
rorisdeterminedfrompropagatingtheerro−rs1.2ofthecontributing gas into or out of the line of sight cannotexplain the observed
quantities. behaviorofcomponent1overthe5observedepochs.
Assuming the canonical 50% global covering factor for Can changes of the ionizing flux experienced by the out-
Seyfertoutflows(Crenshawetal.1999),andusingequation(1) flowinggasexplaintheobservedtroughchanges?Weconstruct
in Aravetal. (2013) we find thatthe massflux associated with suchamodelunderthesimplestandrestrictiveassumptionthat
the UV manifestation of component 1 is 1.0+−20..05 solar masses the NH ofcomponent1 didnotchangeoverthe 16yearsspan-
per year, and that the kinetic luminosity is 4+8 × 1041 erg s−1. ningthe5highresolutionUVspectralepochs.Furthermore,for
WenotethatmostoftheNH inthevariousou−tfl2owcomponents log(ne)=4.8(cm−3),theabsorbershouldreacttochangesinin-
isassociatedwiththehigherionizationX-rayphaseofthe out- cidentionizingfluxontime-scalesof 5days(seeeq.3here,and
flow.Therefore,wedeferafulldiscussionofthetotalmassflux discussioninAravetal. 2012).Therefore,forcomponent1 we
andkineticluminosityoftheoutflowtoafuturepaperthatwill usetherestrictiveassumptionofasimplephotoionizationequi-
presentacombinedanalysisoftheUVandX-raydatasets. librium,determinedbythefluxlevelofthespecificobservation.
In 1998 the AGN was in a high flux level of F=6 (mea-
sured at 1350 Å rest-frame and given in units of 10−14
3.3.ModelingtheTemporalBehavioroftheOutflow
ergs s−1 cm−2 Å−1). At that epoch the absorber only showed
The absorption troughs of component1 change drastically be- a Lyα trough necessitating log(UH) ∼> 0.1 (otherwise a Nv
tweenthe fiveHST high-resolutionspectroscopicepochsspan- troughwouldbedetected,seeFig.5).In2002theAGNwasina
ning 16 years (see figures A2 and A3). After finding the lo- mediumfluxlevelwithF=2,atwhichtimetheabsorbershowed
cation and physical characteristics of component 1 using the Civ andNv troughsin additionto Lyα. In 2004the AGN was
2013 data, the next step is to derive a self-consistent temporal atahistoricallylowfluxofF=0.25.InthatepochaSiiiitrough
picture for this component. There are two general models that appearedinadditiontotheCiv,NvandLyαtroughs;however,
explain trough variability in AGN outflows (e.g., Barlowetal. aCiitroughdidnotappear.ThecombinationoftheSiiiiandCii
1992;Gabeletal.2003;Capellupoetal.2012;Aravetal.2012; constraints necessitates −1.3 < log(UH) < −1.15 (see Fig. 5).
FilizAketal. 2013, and references therein). One model at- The change in log(UH) required by the photoionization mod-
tributesthetroughvariabilitytochangesoftheionizingfluxex- elsagreesremarkablywellwiththechangeinfluxbetweenthe
periencedbytheoutflowinggas.Initssimplestform,thismodel 1998and2004epochsaslog(F2004/F1998) =−1.4.Thus,acon-
assumesthatthetotalNH alongthelineofsightdoesnotchange stant NH absorberyieldsanexcellentfitforthe absorptionfea-
as a function of time. A second model invokes material mov- tures from two epochs with the same spectral energy distribu-
ingacrossthelineofsight,whichingeneralcauseschangesof tion(highSEDinFigureFig.5),butwithverydifferentUH val-
N along the line of sight as a function of time to explain the ues.Comparisonofseveralkeytroughsbetweenthe5epochsis
H
observedtroughchanges. showninFigs.A2andA3.The1350Åfluxmeasurements,plus
In the case of component 1, we have enough constraints observation details are given in Table A.1 and the derived col-
to exclude the model of material moving across our line of umndensitiesforalltheoutflowfeaturesaregiveninTableA.2.
sight.The outflowis situatedat3.5 pcfromthe centralsource, In 2013 the AGN flux was F=3. With this flux level and
which combined with the estimated mass of the black hole in assuming the same SED, the U value should have been 50%
H
NGC5548(4×107 solarmasses;Pancoastetal.2013),yieldsa higher than in 2002, and we would expect to see only Civ,
Keplerianspeedof1.9×107 cms−1 atthatdistance.Ascanbe NvandLyαtroughs.Insteadwe alsodetectSiiii, Cii, Siii and
seen from figure A1, 2/3 of the emission at the wavelength of Alii. Therefore, the incident SED for component 1 must have
component1 arises fromthe Civ BroadEmission Line (BEL). changed,andindeedthe2013softX-rayfluxis25timeslower
Therefore,thetransversemotionmodelcruciallydependsonthe comparedtothatofthe2002epoch(seeFig.1inKaastraetal.
ability of gas clouds to cross most of the projected size of the 2014).Thisdropiscausedbythenewlyobservedobscurerclose
BroadLineRegion(BLR)inthetimespanningtheobservations totheAGN,whichdoesnotfullycoverthesource(Kaastraetal.
epochs. Reverberation studies (Koristaetal. 1995) give the di- 2014).WefoundagoodmatchtotheUVabsorptionandsoftX-
ameteroftheCivBLRas15lightdaysor3.9×1016cm,which rayfluxwithanSEDthatissimilartothatofthehighfluxone
for v⊥ = 1.9×107 cm s−1, yieldsa crossing time of 2.0×109 longwardof1Ry,butabruptlydropsto6%ofthatfluxbetween
seconds,or65years. 1Ryand1keV(seeFig.2).Thispictureisconsistentwiththe
Thus, in the 16 years between our epochs, material that transmitted flux resulting from the low-ionization, partial cov-
movesattheKeplerianvelocity,3.5pcawayfromtheNGC5548 eringmodeloftheobscurerderivedinKaastraetal.(2014).To
black hole, will cross only about 25% of the projected size of complete the UV picture for component1, in 2011NGC 5548
the Civ BLR. Therefore, the much larger change in the resid- showed F=6, equal to that of the 1998 epoch. However, Civ
5
N.Aravetal.:NGC5548
notbetweenthe2013/7/24and2013/8/1ones,whenwe dosee
changes in component 1. Using the formalism given in § 4 of
Aravetal. (2012), we can deduce the n of these components
e
fromtheobservedtime lags.Supposean absorberin photoion-
izationequilibriumexperiencesasuddenchangeintheincident
22
ionizing flux such that I(t > 0) = (1 + f)I(t = 0), where
) NH −1≤ f ≤∞.Thenthetimiescaleforchangeintiheionicfraction
( g isgivenby:
o 2004 2002 1998
L
2013 2011 n α −1
t∗ = −fαn i+1 − i−1 , (3)
" i e n α !#
21 CII 2004 SiIII 2004 SiIII 2011 CIV 2002 NV 1998 HI 1998 owsefhpaearrgeaitvαeeienipseotlchehmesreseinhctooiwmnibinoigninatirztoiaoutnigohrnactsehtaaognfegieoisn.aFinradonmtdhenthi7eisd4at0hyesdsafreyapscattrihaoatn-t
ingepochswithnochange,wecandeduce3.5 < log(n ) < 4.5
-2 -1 0 e
Log (U ) (cm−3)forbothcomponents,otherwisetheirtroughswouldnot
H
react to changes in incident ionizing flux in the observed way,
Fig.5.A photoionizationphaseplotshowingtheionizationso-
despitethelargechangesinincidentionizingfluxoverthatpe-
lutionsforcomponent1forall5epochs.The2013epochsolu-
riod.AssumingasimilarU tothatofcomponent1(seediscus-
H
tionisidenticaltotheoneshowninFig.3.Forthe1998,2002,
sionbelow),thisn rangeyieldsdistancesof5<R<15parsec.
e
and 2004 epochs we used the high SED (see Fig. 2) with the Similarly,component6showsCivandNvtroughsin2011but
same abundances, and their ionization solutions are shown in
not in 2002. This nine years timescale yields R < 100 parsec.
bluecrosses.DashedlinesrepresentN lower-limitthatallow
ion Component2andcomponent4donotshowchangesintheUV
thephase-spaceabovetheline,whilethedottedlinesareupper-
absorptionbetweenanyoftheepochs.Therefore,wecanderive
limits that allow the phase-spacebelow the line (onlythe most
alowerlimitfortheirdistanceofR>130parsec.
restrictive constraints are shown). N is fixed for all epochsat
H ConstrainingN andU :Itisnotfeasibletoputphysically
H H
the value determined from the 2013 solution. For 1998, 2002
interestingconstraintsoncomponents2,4and6.First,theyonly
and2004thedifferenceinUH valuesisdeterminedbytheratio showtroughsfromCiv,Nv,andLyα,which(basedonouranal-
of fluxesat 1350Åand the actual value is anchoredby the ob- ysisofcomponent1)areprobablyhighlysaturated.Second,the
servedNionconstraints.Asexplainedin§3.3,theUH positionof ionizationtime-scalesofcomponents2and4arelargerthan16
the2011epochislesstightlyconstrained.Thesolutionforeach years.Therefore,evenifaU canbededucedfromthemeasure-
H
epochsatisfiesalltheNionconstraintsforthatepoch. ments,itwillonlybearepresentativeaveragevalueforaperiod
oftimelargerthan16years.
Figure 6 shows the N –U phase plot for component 3
H H
based on the N reported in Table A.2 (the Lyα and Civ
and Nv are clearly seen in the 2011 epoch but not any of the N lowerlimitsioanretriviallysatisfiedbythelowerlimitshown
ion
other ionic species seen in 2013. To explain this situation we for the Nv N ). The phase plot constraints given by the N
ion ion
assume that the obscurer was present at the 2011 epoch, but it measurementsare mostly parallel to each other. Therefore,the
onlyblockedsomewherebetween50–90%oftheemittedioniz- N –U constraints are rather loose, allowing a narrow strip
H H
ingradiationbetween1Ryand1keV.Thepossiblepresenceof from log(N ) = 19.6 and log(U ) = −2, to log(N ) = 21.5
H H H
a weaker X-rayobscureris also suggestedbybroadabsorption and log(U ) = −1.1. If we take the most probable value of
H
onthebluewingoftheCIVemissionlinein2011thatisweaker log(U ) = −1.3, the distance estimate for component 3 will
H
thanthatseenin2013. dropby30%comparedwiththeestimateof5 < R < 15parsec,
Tosummarize,asimplemodelbasedonafixedtotalcolumn- whichusedthelog(U )=−1.5ofcomponent1.Forcomponent
H
density absorber, reacting to changes in ionizing illumination, 5, the situation is rather similar, as the detected Siiii and Siiv
matches the very different phenomenology seen in all high- allowanarrowstripfromlog(N ) = 19.2andlog(U ) = −1.8,
H H
resolutionUVspectraofcomponent1spanning16years.Figure to log(N ) = 20.7andlog(U ) = −1.2,while the lowestχ2 is
H H
7givesaschematicillustrationofthetemporalmodel. achievedatlog(N )=20.7andlog(U )=−1.3.
H H
4. Components2-6 5. ComparisonwiththeWarmAbsorberAnalysis
Whatarethedistancesandphysicalconditions(N andU )for Howdothephysicalcharacteristicsinferredfromtheoutflows’
H H
the other 5 outflow components(2-6)? As we show below, we UV diagnostics compare to the properties of the X-ray mani-
can derive distances (or interesting limits of) for all these UV festation of the outflow known as the Warm Absorber? Since
components and some loose constraints on the N and U of the soft X-ray flux in our 2013 data is very low due to the ap-
H H
components3and5.Figure7givesthevelocitiesanddistances pearanceoftheobscurer,wecannotcharacterizetheWAthatis
ofall6components,aswellasaschematicillustrationfortheir connectedwiththe6UVoutflowcomponentsatthatepoch.Our
temporalbehavior. main inferences about the WA are from the 2002 epoch when
Constraining the Distances: components2-6 do notshow weobtainedsimultaneousX-rayandUVspectraoftheoutflow
absorptionfromexcitedlevels(Exceptforcomponent3,whose (when no obscurer was present) that gave a much higher soft
Cii/Cii*troughsonlyyieldalowerlimitforn .).However,com- X-rayflux (comparedwith the 2013observations)and allowed
e
ponents 3 and 5 show clear variations in their Siiii and Siiv a detail modeling of the WA in that epoch (Steenbruggeetal.
troughs between our 2013/6/22and 2013/8/1observations, but 2005; Kaastraetal. 2014). Due to the inherent complications
6
N.Aravetal.:NGC5548
Table1.ComparisonbetweentheUVandWAcomponents
22
Component Velocitya log(N ) log(U )
H H
(kms−1) (cm−2) (2002)
UV1b -1160 21.5+0.4 −0.4+0.4
+ SiIV UV2 -720 —−0.2 —−0.2
) NH 21 UV3 -640 19.6−21.5 (−0.9)−0.0
( g SiIII UV4 -475 — —
o UV5 -300 19.2−20.7 (−0.7)−(−0.1)
L
UV6 -40 — —
WAAc −588±34 20.30±0.12 −0.82±0.08
CII WAB −547±31 20.85±0.06 −0.09±0.05
20 WAC −1148±20 21.18±0.08 0.55±0.03
NV WAD −255±25 21.03±0.07 0.76±0.03
WAE −792±25 21.45±0.12 1.34±0.08
WAF −1221±25 21.76±0.13 1.53±0.05
avelocitycentroidofthecomponent
-2 -1 0
Log (U ) bUVcomponents1-6arearrangedbydecreasingabsolutevelocity.
H
cParametersforWarmAbsorbercomponentsA-FarefromTableS2
Fig.6. A photoionization phase plot showing the ionization ofKaastraetal.(2014).Theyarearrangedbyincreasingionization
solution for component 3 epoch 2013. As for component 1, parameter.
we use the obscured SED and assumed proto-solar metalicity
(Loddersetal. 2009). Solid lines and associated colored bands
represent the locus of UH,NH models, which predict the mea- theWAareatlowenoughionizationstatestogiverisetotheUV
sured Nion, and their 1σ uncertainties, while the dashed line is observedmaterial.
thelowerlimitontheNvcolumndensitythatpermitsthephase-
3. Assuming constant N for the UV componentsand com-
spaceaboveit.Thebluecrossisthebestχ2 solutionandissur- H
ponentsAandBoftheWA.
roundedbya1σ χ2bluecontour.
Our temporalmodel for component1 has a constant N value
H
inalltheobservedepochs,including2002.Themodelalsopre-
dicts the U of the 2002 epoch (see Fig. 5). We can therefore
H
compare the predictions of this model to the results of the re-
analysisofthe2002WA(Kaastraetal.2014),providedthatthe
of comparinganalyses on differentspectral regions(X-rayand N forcomponentsAandBoftheWAalsodidnotchangeover
H
UV) separated by 11 years(2002and 2013),of a clearly time- the 11 years between the epochs. We note that since UV com-
dependent phenomenon, we defer a full comparison to a later ponent1 is the closest to the central source, the assumption of
paper (Ebrero et al 2015). Here we outline some of the main constant N for the other UV components, over this 11 years
H
points in such a comparison, based on the analysis presented time period, is reasonable (see discussion in § 3.3). Therefore,
here and the published analysis of the WA (Steenbruggeetal. we use the same ionization assumptionsfor UV components3
2005; Kaastraetal. 2014) and discuss some of the similarities and5asforcomponent1.Thatis,their N isfixedtothe2013
H
andchallengesofsuchacombinedanalysis. valueandtheirlog(U ) = log(U ) +1.1,whicharethe
H 2002 H 2013
1.KinematicSimilarity.Thereiskinematiccorrespondence valueswe list in Table 1. We do nothave empiricalconstraints
betweentheUVabsorptiontroughsincomponents1–5andthe onthedistancesofWAcomponentsA-Ffromthecentralsource.
sixionizationcomponents(A–F)oftheX-rayWA(Kaastraetal. 4.ComparingUVcomponents1and3tocomponentsAand
2014, see Table 1 here). X-ray components F and C span the BoftheWA.
width of UV component 1. X-ray component E matches UV Using proto-Solar abundances (Loddersetal. 2009), our 2002
component2. The lowest ionization X-ray components, A and model prediction for UV component1 has log(N ) = 21.5+0.4
H −0.2
B comprise the full width of the blended UV troughs of com- cm−2, and an ionization parameter of log(U ) = −0.4+0.4 (see
H −0.2
ponents 3 and 4 . Finally, X-ray component D kinematically § 3.1 and Fig. 5). This model gives a good match for the UV
matchesUVcomponent5.However,asweshowinpoint2be- dataofthatepoch(2002)anditslog(U )isinbetweenthoseof
H
low, this kinematic matching is physically problematic as the WAcomponentsA[log(U ) = −0.8]andB[log(U ) = −0.1].
H H
ionizationparametersofWAcomponentsC,D,EandFaretoo However, there are two inconsistencies between the models.
hightoproduceobservedtroughsfromCivandNvthatareob- First,componentsAandBhaveatotallog(N )=20.95±0.1or
H
servedinalltheUVcomponents. about2σdisagreementwiththatofUVcomponent1.Thisdis-
2.Comparingsimilarionizationphases. crepancyis mainlydueto the limit onthe Ovii Nion thatarises
WenotethattheX-rayanalysisoftheWAintheChandra2002 from the bound-free edge of this ion in the X-ray data. In the
observations uses a different ionization parameter (ξ) than the WAmodel,about95%oftheOviiNion arisesfromcomponents
U we use here; where ξ ≡ L/(n r2) (erg cm) with n being A andB. Second,the reportedvelocitycentroidsfor WA com-
thHehydrogennumberdensity,LtheHionizingluminositybHetween ponents A and B (−588± 34 km s−1 and −547± 31 km s−1,
13.6eVand13.6keVandrthedistancefromthecentralsource. respectively)arein disagreementwith the velocitycentroidsof
ForthehighSED,log(U ) = log(ξ)+1.6.InTable1, we give UVcomponent1(−1160kms−1)andits300kms−1width.
H
thelog(U )fortheWAcomponents.FromtheWAanalysisand UVcomponent3hasavelocitycentroidat–640kms−1and
H
figure5here,wededucethat90%oftheWAmaterial(compo- awidthof∼200kms−1,andthereforeisabettervelocitymatch
nentsC,D,EandFinTableS2ofKaastraetal.2014)isintoo with WA components A and B. The large uncertainties in the
high an ionization stage to produce measurable lines from the inferredN andU forUVcomponent3(seeFig.6andTable
H H
UVobservedions(e.g.,Civ,Nv).OnlycomponentAandBof 1), make these values consistent with the N and U deduced
H H
7
N.Aravetal.:NGC5548
for WA components A and B. However, the uncertainties also 6. Discussion
allow UV component 3 to have a negligible N compared to
H
WAcomponentsAandB. 6.1.ComparisonWithPreviousWork
We notethatwiththecurrentanalyses,thebettertheagree- Howdotheseresultscomparewiththepreviousextensivework
mentbetweenUVcomponent3andWA componentsA andB, ontheenduringoutflowinNGC5548?Forthefirsttimeasim-
theworseisthedisagreementbetweenUVcomponent1andWA ple model of a constant NH absorber yields a physical picture
componentsAandB.ThisisbecauseUVcomponent1already thatisconsistentwiththesubstantialtroughvariationseeninall
predictshighervaluesofN andOviiN thanaremeasuredin epochsofhighresolutionUVspectralobservations.Thetrough
H ion
WA components A and B, and the kinematics of the deduced changesareexplainedsolely bytheobserveddifferencesinthe
Ovii N disagree considerably. In points 5 and 6 below we incidentionizingflux.Inaddition,wedeterminerobustdistances
ion
identifytwopossiblewaystoalleviateandeveneliminatethese for(orlimitson)all6kinematiccomponents.Ourresultsdiffer
apparentdiscrepancies. considerablyfromthosepreviouslyfoundforthisoutflow(e.g.,
Crenshawetal. 2009). This is due to the powerful diagnostics
5. Existence of considerable Ovii N at the velocity of
ion that were revealedduring the 2013 campaign,recognizingthat
UV component 1. The 2002 X-ray spectra presented by
manyoftheobservedtroughsarehighlysaturated(e.g.,theex-
Steenbruggeetal. (2005) consist of two different data sets that istence of similar depth Civ and Pv troughs in component 1;
wereacquiredinthesameweek:170ksobservationstakenwith
seediscussioninBorguetetal.2012a)andthefactthatthepre-
the High EnergyTransmissionGratingSpectrometer(HETGS) vious work did not account for the emergence of Siiii troughs
and 340 ks observations with the Low Energy Transmission
associatedwithcomponents1and3inthe2004data.
Grating Spectrometer (LETGS). Figure 2 in Steenbruggeetal.
(2005)showssomeofthelowionizationWAtroughsinvelocity
presentation,wherethedottedlinesshowthepositionoftheUV 6.2.ImplicationsforBALVariabilityStudies
components (with somewhat different velocity values than we
use here due to the use of a slightly differentsystemic redshift Our multiwavelength campaign has significant consequences
fortheobject).TheLETGSdataoftheOviiandOvtroughsare for studies of absorption trough variability in quasar outflows,
consistentwithonemainkinematiccomponentmatchingtheve- and in particular for the intensive studies of trough variabil-
locityofUVcomponent3.However,themorenoisybuthigher ityinBroadAbsorptionLine(BAL)quasars(e.g.,Barlowetal.
resolutionHETGS data for the same transitions, show two sub 1992;Capellupoetal.2012;FilizAketal.2013,andreferences
troughsone correspondingto UV component1 and one to UV therein).As discussed in § 3.3, the two main proposedmecha-
component3.Therefore,itispossiblethatmuchoftheOviiN nisms for trough variability are (1) reaction to changes in ion-
ion
isassociatedwithUVcomponent1. izing flux of a constant absorber (which is the model we suc-
cessfullyusetoexplaintheNGC5548outflowtroughchanges);
6. Abundances considerations: As mentioned in § 3, for the and(2)absorbermotionacrossthelineofsight(e.g.,Gabeletal.
UVanalysis,weusepureproto-Solarabundances(Loddersetal. 2003),whichaswedemonstrated,cannotexplainthevariability
2009), which well-matchthe measured Nion from the UV data. oftheNGC5548outflow(see§3.3).
But these models produce considerably more Ovii N in the
ion In some BAL cases the rest-frame UV flux around 1350
2002epoch,thanthemeasuredOvii N inthewarmabsorber
ion Å does not change appreciably between the studied epochs
data. However, the N (and therefore also the Ovii N ) of
H ion whilesignificanttroughvariabilityisobserved.Thisbehavioris
UV component1 is critically dependenton the assumed phos-
takenasanargumentagainstmechanism(1)(e.g.,Barlowetal.
phorus abundance. Ionization models with all elements having
1992; FilizAketal. 2013) as the ionizing flux (below 912Å)
proto-Solar abundances except phosphorus, for which we as-
is assumed to correlate with the longer wavelength UV flux.
sume twice proto-Solar abundance, preserve the fit to the UV
However,oursimultaneousUV/X-rayobservationsshowaclear
data(at1/3the N value)andatthesametimematchtheOvii
H casewheretheionizingphotonfluxdropsbyafactorof25be-
N measured in the X-ray warm absorber at the 2002 epoch.
ion tween the 2002 and 2013 epochs, while the 1350 Å UV flux
Larger over-abundances of phosphorus further reduce the N
valueandthereforethepredictedOviiN forthe2002epoch.H actuallyincreasesby50%.
ion
ThespectroscopicdatasetofNGC5548giveshighS/Nand
But are such assumed abundances physically reasonable? high-resolutionspectraofmanyUVabsorptiontroughs,andsi-
AGN outflows are known to have abundances higher by fac- multaneously yields the crucial soft X-ray flux that is respon-
tors of two (Aravetal. 2007) and even ten (Gabeletal. 2006) sible for the ionization of the outflow. Such data can constrain
comparedwiththeproto-Solarvalues.Inparticular,phosphorus troughvariabilitymodelsfarbetterthanthestandardvariability
abundance in AGN outflows, relative to other metals, can be a datasetswhereoneortworest-frameUVBALareobservedat
factorofseveralhigherthaninproto-Solarabundances(see§4.1 two (andlessfrequentlyinmore)epochs(e.g.,Capellupoetal.
in Aravetal. 2001). Furthermore, the theoretical expectations 2012;FilizAketal.2013).
forthevalueofchemicalabundancesinanAGNenvironmentas
a function of metalicity are highly varied. The leading models
can differ about relative abundances values by factors of three 6.3.ImplicationsfortheX-rayObscurer
ormore(e.g.,comparingthevaluesofHamann&Ferland1993;
What do our results about the enduring outflow tell us about
Balleroetal.2008).
theX-rayobscurerandthebroadUVabsorptiondiscoveredby
WeconcludethatifroughlyhalfoftheobservedOviiN is Kaastraetal.(2014)?ThederivedtransmissionfortheX-rayob-
ion
associatedwithUVcomponent1(asdiscussedinpoint5),and scurerisconsistentwiththeSEDrequiredforthe2013spectrum,
iftherelativeabundanceofphosphorustooxygenistwicesolar thus showing that the obscurer is closer to the super massive
or larger,than the N , U and velocity distribution of the WA blackholesthan3.5pc.,andthatitsshadowinfluencesthecon-
H H
andUVoutflowinggascanbeconsistent. ditionsinthemoredistantnarrowUVabsorbers.
8
N.Aravetal.:NGC5548
Fig.7.Anillustrationofthephysical,spatialandtemporalconditionsoftheoutflowsseeninNGC5548.Alongthetimeaxiswe
show the behavior of the emission source at the 5 UV epochs and give its UV flux values (measured at 1350 Å rest-frame and
giveninunitsof10−14 ergss−1 cm−2 Å−1).Theobscurerissituatedatroughly0.01pcfromtheemissionsourceandisonlyseen
in2011and2013(itismuchstrongerin2013).Outflowcomponent1showsthemostdramaticchangesinitsabsorptiontroughs.
Differentobservedionicspeciesarerepresentedascoloredzoneswithintheabsorbers.Thetroughchangesarefullyexplainedby
ourphysicalmodelshowninFigure5.Usingcomponent1Ciii*troughs,whichareonlyseeninthe2013epoch,wedetermineits
numberdensity(seeFigure4)tobelog(n ) = 4.8±0.1cm−3,andthereforeitsdistance,R=3.5parsec.Thedistancesfortheother
e
componentsare discussed in § 4. Dimmer clouds represent epochs where components2-6 did not show new absorption species
comparedwiththe2002epoch.
7. Summary of log(N ) = 21.5+0.4 cm−2, an ionization parameter of
H −0.2
log(U ) = −1.5+0.4, and an electron number density of
In 2013 we executed the most comprehensive multiwave- H −0.2
log(n ) = 4.8±0.1cm−3.Thiscomponentprobablycarries
length spectroscopic campaign on any AGN to date, directed e
thelargestN associatedwiththeUVoutflow.See§3.1and
at NGC 5548. This paper presents the analysis’ results from H
ourHST/COSdataofthe oftenobservedUVoutflow,whichis §3.2forelaboration.
2. For component 1 a simple model based on a fixed total
detectedin 6 distinctkinematiccomponents.Ourcampaignre-
column-densityabsorber,reactingtochangesinionizingil-
vealedanunusuallystrongX-rayobscuration.Theresultingdra-
lumination,matchestheverydifferentionizationstatesseen
maticdecreaseinincidentionizingfluxontheoutflowallowed
atfivespectroscopicepochsspanning16years.See§3.3for
us to construct a comprehensivephysical, spatial and temporal
elaboration.
pictureforthewell-studiedAGNwindinthisobject.Ourmain
3. Thewealthofobservationalconstraintsmakesourchanges-
findingsarelistedbelow(seeFig.7foragraphicillustrationof
of-ionization model a leading contender for interpreting
ourresults).
troughvariabilitydataofquasaroutflows,inparticularBroad
AbsorptionLine(BAL)variability.See§6.2forelaboration.
1. Ourbestconstraintsareobtainedforcomponent1(thehigh-
est velocity component): It is situated at 3.5±1 pc from 4. Components3and5aresituatedbetween5-15pcfromthe
centralsource,component6iscloserthan100pcandcom-
the central source, has a total hydrogen column density
9
N.Aravetal.:NGC5548
ponents2and4arefurtheroutthan130pc.See§4forelab- deVaucouleurs,G.,deVaucouleurs, A.,Corwin,Jr.,H.G.,etal.1991,Third
oration. ReferenceCatalogueofBrightGalaxies.VolumeI:Explanationsandrefer-
5. A detailed comparison of the physical characteristics in- ences.VolumeII:Dataforgalaxiesbetween0hand12h.VolumeIII:Datafor
galaxiesbetween12hand24h.
ferred from the outflows’ UV diagnosticswith those of the
Dere,K.P.,Landi,E.,Mason,H.E.,MonsignoriFossi,B.C.,&Young,P.R.
X-ray Warm Absorber is deferred to a future paper. Here 1997,A&AS,125,149
we outline some of the main points in such a comparison, Edmonds,D.,Borguet,B.,Arav,N.,etal.2011,ApJ,739,7
anddiscusssomeofthesimilaritiesandchallengesofsucha Faucher-Gigue`re,C.-A.,Quataert,E.,&Murray,N.2012,MNRAS,420,1347
combinedanalysis.See§5forelaboration. Ferland, G.J.,Porter, R. L.,van Hoof, P.A.M., et al. 2013, Rev. Mexicana
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Acknowledgements. This work was supported by NASA through grants for Gabel,J.R.,Arav,N.,&Kim,T.2006,ApJ,646,742
HSTprogramnumber13184fromtheSpaceTelescopeScienceInstitute,which Gabel,J.R.,Crenshaw,D.M.,Kraemer,S.B.,etal.2003,ApJ,583,178
is operated by the Association of Universities for Research in Astronomy, Gabel,J.R.,Kraemer,S.B.,Crenshaw,D.M.,etal.2005,ApJ,631,741
Incorporated, under NASA contract NAS5-26555. SRON is supported finan- Green,J.C.,Froning,C.S.,Osterman,S.,etal.2012,ApJ,744,60
ciallybyNWO,theNetherlandsOrganizationforScientificResearch.M.M.ac- Hamann,F.,Barlow,T.A.,Junkkarinen,V.,&Burbidge,E.M.1997,ApJ,478,
knowledgesthesupportofaStudentshipEnhancementProgrammeawardedby 80
theUKScience&TechnologyFacilitiesCouncil(STFC).P.-O.P.andF.U.thanks Hamann,F.&Ferland,G.1993,ApJ,418,11
financial supportfromtheCNESandfromtheCNRS/PICS.F.U.acknowledg Hopkins,P.F.&Elvis,M.2010,MNRAS,401,7
PhDfundingfromtheVINCIprogramoftheFrench-ItalianUniversity.K.C.S. Kaastra,J.S.,Detmers,R.G.,Mehdipour,M.,etal.2012,A&A,539,A117
wantstoacknowledge financial supportfromtheFondoFortalecimiento dela Kaastraetal.,J.S.2014,Science
ProductividadCientficaVRIDT2013.E.B.issupportedbygrantsfromIsrael’s Korista,K.T.,Alloin,D.,Barr,P.,etal.1995,ApJS,97,285
MoST, ISF (1163/10), and I-CORE program (1937/12). J.M. acknowledges Landi,E.,Young,P.R.,Dere,K.P.,DelZanna,G.,&Mason,H.E.2013,ApJ,
fundingfromCNRS/PNHEandCNRS/PICSinFrance.G.M.andF.U.acknowl- 763,86
edge financial support from the Italian Space Agency under grant ASI/INAF Lodders,K.,Palme,H.,&Gail,H.-P.2009,in”Landolt-Bo¨rnstein -GroupVI
I/037/12/0-011/13. B.M.P. acknowledges support from the US NSF through AstronomyandAstrophysicsNumericalDataandFunctionalRelationships
grant AST-1008882. M.C, S.B, G.Mand A. D. R., acknowledge INAF/PICS inScienceandTechnologyVolume,ed.J.E.Tru¨mper,44
support.G.P.acknowledgessupportviaanEUMarieCurieIntra-Europeanfel- Mehdipouretal,M.2014
lowshipundercontractno.FP-PEOPLE-2012-IEF-331095.M.W.acknowledges Ostriker,J.P.,Choi,E.,Ciotti,L.,Novak,G.S.,&Proga,D.2010,ApJ,722,
the support of aPhD studentship awarded bythe UK Science & Technology 642
FacilitiesCouncil(STFC). Pancoast,A.,Brewer,B.J.,Treu,T.,etal.2013,ArXive-prints
The data used in this research are stored in the public archives of the Schlegel,D.J.,Finkbeiner,D.P.,&Davis,M.1998,ApJ,500,525
satellites thatareinvolved. WethanktheInternational SpaceScience Institute Soker,N.&Meiron,Y.2011,MNRAS,411,1803
(ISSI)inBern forsupport. This workisbasedonobservations obtained with Steenbrugge,K.C.,Kaastra,J.S.,Crenshaw,D.M.,etal.2005,A&A,434,569
XMM-Newton,anESAsciencemissionwithinstrumentsandcontributionsdi-
rectly funded byESAMember States andthe USA (NASA).It is alsobased
on observations with INTEGRAL, an ESA project with instrument and sci-
ence data center funded by ESA member states (especially the PI countries:
Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic, and
Poland and with the participation of Russia and the USA. This work made
useofdatasuppliedbytheUKSwiftScienceDataCentreattheUniversityif
Leicester.ThisresearchmadeuseoftheChandraTransmissionGratingCatalog
andarchive(http://tgcat.mit.edu).Thisresearchhasmadeuseofdataobtained
withtheNuSTARmission,aprojectledbytheCaliforniaInstituteofTechnology
(Caltech), managed by the Jet Propulsion Laboratory (JPL) and funded by
NASA,andhasutilizedtheNuSTARDataAnalysisSoftware(NUSTARDAS)
jointly developed bytheASIScience DataCenter (ASDC,Italy)andCaltech
(USA).Figure7wascreatedbyAnnFeildfromSTScI.
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