Exploratory Study of the X-Ray Properties of Quasars With Intrinsic Narrow Absorption Lines

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by  Toru Misawa

ACCEPTEDFORPUBLICATIONINTHEASTROPHYSICALJOURNAL
PreprinttypesetusingLATEXstyleemulateapjv.10/09/06
EXPLORATORYSTUDYOFTHEX-RAYPROPERTIESOFQUASARSWITHINTRINSICNARROWABSORPTION
LINES
TORUMISAWA,MICHAELERACLEOUS1,GEORGECHARTAS,ANDJANEC.CHARLTON
DepartmentofAstronomyandAstrophysics,PennsylvaniaStateUniversity,525DaveyLab,UniversityPark,PA16802
AcceptedforpublicationintheAstrophysicalJournal
ABSTRACT
WehaveusedarchivalChandraandXMM-NewtonobservationsofquasarshostingintrinsicnarrowUVab-
sorptionlines(intrinsicNALs)tocarryoutanexploratorysurveyoftheirX-rayproperties.Oursampleconsists
8
ofthreeintrinsic-NALquasarsandone“mini-BAL”quasar,plusfourquasarswithoutintrinsicabsorptionlines
0
for comparison. These were drawn in a systematic manner from an optical/UV-selectedsample. The X-ray
0
propertiesofintrinsic-NALquasarsareindistinguishablefromthoseof“normal”quasars. Wedonotfindany
2
excessabsorptioninquasarswithintrinsicNALs,withupperlimitsofNH∼<afew×1022 cm−2. Wecompare
n theX-rayandUVpropertiesofoursamplequasarsbyplottingtheequivalentwidthandblueshiftvelocityof
a theintrinsicNALsandtheX-rayspectralindexagainstthe“optical-to-X-ray”slope,a . WhenBALquasars
J ox
andotherAGNswithintrinsicNALsareincluded,theplotssuggestthatintrinsic-NALquasarsformanexten-
0
sion ofthe BAL sequencesandtend to bridgethe gapbetweenBAL and“normal”quasars. Observationsof
1
largersamplesof intrinsic-NALquasarsare neededto verifythese conclusions. We also test two competing

scenariosforthelocationoftheNALgasinanaccretion-diskwind. Ourresultsstronglysupportalocationof
]
h theNALgasathighlatitudesabovethedisk,closertothediskaxisthanthedenseBALwind.Wedetectexcess
p X-rayabsorptiononlyinQ0014+8118,whichdoesnothostintrinsicNALs.Theabsorbingmediumverylikely
- correspondstoaninterveningsystematz=1.1,whichalsoproducesstrongabsorptionlinesintherest-frame
o
UVspectrumofthisquasar.IntheappendixwediscusstheconnectionbetweenUVandX-rayattenuationand
tr itseffectona ox.
s
Subjectheadings:galaxies:active–galaxies:nuclei–X-rays:galaxies–quasars:absorptionlines
a
[

1 1. INTRODUCTION AGNs(e.g.,Shields1977;Chiang&Murray1996;Murray&
v Chiang1997). Moreover,theoutflowsmaybeimportantfor
The intrinsic absorption lines found in the rest-frame UV
2 cosmology since they deliver energy and momentum to the
spectra of quasars and active galactic nuclei (AGNs) are
9 interstellarandintergalacticmedia(hereafter,ISMandIGM,
classified based on their line widths into broad absorption
6
1 lines (BALs; FWHM> 2000 km s−1, found in ∼ 10% respectively)andcanaffectgalaxyevolution(e.g.,Granatoet
al. 2004; Scannapieco & Oh 2004; Springel, Di Matteo &
. of all quasars), narrow absorption lines (NALs; FWHM<
1 500kms−1,foundin∼50%ofquasarsatz∼2–4;thesecan Hernquist2005;Chartasetal. 2007a).
0 Most of our knowledge about intrinsic absorbers is de-
beclearlyseparatedfrominterveninglinesviahigh-resolution
8 rived from optical/UV observations. A combination of ob-
spectroscopy),andmini-BALs(intermediateFWHMbetween
0 servational results and models suggest that intrinsic absorp-
BALs and NALs). They are typically blueshifted relative
v: to the quasar and are thought to trace outflows from the tion lines of different widths represent either different lines
i quasar central engine. These outflows could be hydromag- ofsightthroughtheoutflowingwindtothequasarcontinuum
X
source(Gangulyetal. 2001;Elvis2000),ordifferentstages
netic accretion-disk winds (e.g., Blandford & Payne 1982;
r intheevolutionoftheabsorbinggasparcels(e.g.,Hamann&
Emmering, Blandford & Shlosman 1992; Ko¨nigl & Kartje
a
Sabra2004;Misawaetal. 2005).
1994; Everett 2005), or accretion-disk winds driven by ra-
X-ray observations of BAL quasars have revealed large
diationpressure(e.g.,Murrayetal. 1995;Arav,Li,&Begel-
columns of nearly-neutral absorbing gas (∼ 1023−24 cm−2;
man1994,Proga,Stone,&Kallman2000).Alternativelythey
see, for example, Green & Mathur 1996; Gallagher et al.
couldbeoutflowsdrivenbythermalpressureandlaunchedei-
2002a). However,little is knownaboutthe X-ray properties
therfromtheaccretiondiskitself(e.g.,Begelman,McKee,&
ofquasarswithintrinsic NALsandmini-BALs. X-rayspec-
Shields 1983) or from the obscuring torus invoked by AGN
troscopy of the last two types of quasars can be extremely
unificationschemesanddrivenbythermalpressure(e.g.,Bal-
usefulinmanyrespects:
sara & Krolik 1993; Krolik & Kriss 1995, 2001; Chelouche
& Netzer 2005). However, thermalaccretiondisk winds are
• Ingeneralterms,wecancomparetheX-rayproperties
toohotto produceabsorptionlinesinthe UV, whilethermal
of quasars that host intrinsic NALs with those that do
windsfromtheobscuringtorusaretooslowtoaccountforthe
not. Thiscomparisonallowsustoassesswhetherthere
observevelocitiesofNALsandBALs. Accretiondiskwinds,
is a significant difference between the central engines
whatevertheirorigin,areanintegralpartoftheaccretionflow,
of the two types of object. If no difference is found,
and may be the source of the broad emission lines that are
andsinceintrinsicNALsareubiquitousinquasarspec-
characteristic of the optical and UV spectra of quasars and
tra(seeMisawaetal2007bandreferencestherein),we
will be led to a picture where intrinsic NALs, hence
Electronicaddress:misawa,mce,chartas,[email protected]
1CenterforGravitationalWavePhysics,ThePennsylvaniaStateUniver- outflows,areauniversalpropertyofquasars.
sity,UniversityPark,PA16802
• X-ray spectra can probe highly-ionizedmedia thatare
2 Misawaetal.
not directly probed by optical/UV absorption lines. 2. SAMPLESELECTION
Moreover,theycanyieldmoredirectmeasurementsof
Our sample was drawn from a survey for intrinsic NALs
thetotalhydrogencolumndensityofabsorbersinarel-
in the Keckhigh-resolutionspectra of 37quasarsatz=2–4
ativelylow-ionizationstate(thiscannotbeeasilydone
(Misawaetal. 2007b).Thesequasarswereoriginallyselected
throughUVabsorptionlines,unlesstheionizationstate
and observed in order to study intergalactic deuterium lines
ofthe gasisverywellconstrained). Thus, wecanuse
(e.g.,O’Mearaetal. 2001,andreferencestherein),therefore,
the X-ray spectra to investigate whether any hot gas
they make up a largely unbiased sample with respect to in-
(which may represent the bulk of the mass) co-exists
trinsicNALs. TheintrinsicNALswereseparatedfromNALs
(mixedorlayered)withtheUVabsorbers.
arising in cosmologically intervening objects based on their
partialcoveragesignature(e.g.,Hamannetal. 1997b;Barlow
• ThecolumndensitiesdeterminedfromtheX-rayspec-
& Sargent 1997; Ganguly et al. 1999, 2003; Misawa et al.
tra constitute a directtest of scenariosforthe location
2003, 2005). In summary, the partial coverage test exploits
oftheNALgasinthelargeroutflow.Inparticular,Elvis
thefactthattheratioofopticaldepthsintheindividuallines
(2000)suggeststhattheNALgasislocatedatverylow
of UV resonance doublets is prescribed by atomic physics.
latitudesabovetheaccretiondisk, implyingverylarge
Departures from the expected ratio in well-resolved, unsat-
column densities (comparable to those found in BAL
urated doublets is interpreted as the result of dilution of the
quasars, i.e., >1022 cm−2). On the other hand, Gan-
∼ line troughsby continuum photonsthat do not pass through
guly et al. (2001)place the NAL gasat high latitudes
the absorber (e.g., Hamann et al. 1997b; Barlow & Sargent
above the accretion disk, implicitly suggesting lower
1997;Gangulyetal.1999),i.e.,theabsorberisverycompact,
columndensities.
thus intrinsic to the quasars (most cosmologically interven-
ingstructuresareconsiderablymoreextendedthanthequasar
• Several examples of intrinsic NALs at high ejection
continuum source). In the case of the prominent UV reso-
velocities (∼0.2c) are now known (see Misawa et al.
nancedoublets(CIV,SiIV,andNV),theratioofopticaldepths
2007bandreferencestherein). Itisextremelyinterest-
betweendoubletmembersis2:1,whichallowsustocompute
ing,therefore,tosearchquasarswithintrinsicNALsfor
analytically the fraction of the continuum photons that pass
high-velocityX-rayabsorptionlines(see,forexample,
throughthe absorber(the coveragefraction). In practicethe
Chartasetal. 2002,2003).Suchobservationscanyield
coveragefractioniscomputedbothbyapplyingtheaboveal-
resultsrelevanttocosmologysincetheycanleadtoes-
gorithmtoeverypixelofthelineprofileandbydecomposing
timatesofthemassoutflowrateandthekineticpower
the profile into kinematic components(representedby Voigt
oftheoutflow(see,forexample,Chartasetal. 2007b). functionswhose FWHM turn out to be of order 10 km s−1)
andapplyingtheabovealgorithmtoeachcomponent.Ifboth
With the above considerations in mind, we have used
methods consistently reveal partial coverage in parts of the
archival Chandra and XMM-Newton data to carry out an
lineprofile,thelineisidentifiedasintrinsic. Wefindthatthe
exploratory survey of the X-ray properties of a small, but
profilesoftheCIVabsorptionlinesoftenhavemultiplekine-
carefully-selected sample of quasars at z ≈ 2.5–3.8. This matic components, not sharing the same coverage fraction.
sampleconsistsofthreequasarshostingintrinsicNALs, one
FurtherdetailsofthemethodologycanbefoundinMisawaet
quasarhostingamini-BAL(HS1603+3820),andfourquasars
al(2007b),andthereferencescitedtherein.
withoutintrinsicabsorptionlinesforcomparison(thesewere
The above search yielded intrinsic CIV NALs in 32% of
selectedinasystematicway,asdescribedinthenextsection).
the quasarsandintrinsic CIV, SiIV, or NV NALs in 50%of
WecomparethepropertiesoftheUVNALs(e.g.,equivalent
thequasars. Tothissampleweaddedonemorequasarhost-
width, outflow velocity) with the parameters describing the
ing a CIV mini-BAL showing the signature partial coverage
X-rayspectrum(e.g.,photonindex,intrinsiccolumndensity,
as well as variability, HS1603+3820 (Misawa et al. 2007a,
andoptical-to-X-rayslope,a ).Thus,weplaceNALquasars
ox and references therein). After searching the Chandra and
in the context of BAL quasars (see Gallagher et al. 2002b;
XMM-Newton archives we found that 11 quasars from the
Brandt,Laor,&Wills2000)andinvestigatewhetheralltypes
abovesurveyhadbeenobservedand8oftheobservedquasars
ofobjectsfollowthesametrendsintheirproperties. Wealso
hadarchivalX-rayspectrawithenoughcountstoyieldinter-
use the column densities determined from the X-ray spectra
esting spectral constraints (the 3 objects that were excluded
to carry out one of the tests outlined, above, namely, we at-
fromourfinalsampleare: Q0241−0146,Q0636+6801,and
tempttodistinguishbetweenthetwodifferentsuggestionsfor
Q1055+4611).The8quasarsmakingupthefinalsampleare
thelocationoftheNALgasinthelargeroutflow.
listedinTable1,whichalsosummarizestheirbasicproperties
In §2, we describe howthe sample was selected and sum- andthepropertiesoftheirintrinsicNALs. Ofthese,threeob-
marizethepropertiesoftheconstituentquasars.In§3and§4, jectshaveintrinsicNALs,onehasamini-BAL,andfourhave
wepresenttheanalysisofthedata(observations,datascreen-
nointrinsicabsorptionlines. Thuswehaveasmall, butwell
ing, and model fits to the X-ray spectra). We compare the
defined sample of NAL quasars and a matching comparison
rest-frameUVandX-raypropertiesin§5. In§6wesumma- sampleofquasarswithoutintrinsicNALs. Allofthequasars
rize our findings, discuss our results, and consider prospects
with intrinsic NALs and 2/4 quasars without intrinsic NALs
for future work. We adopt a cosmologicalmodel with H =
0 areradioquiet.TheChandraandXMM-NewtonX-rayspectra
75 km s−1 Mpc−1, W m=0.3, and W L = 0.7. Throughoutthis of6ofthesequasarswereanalyzedandtheresultspublished
paperwegiveerrorbarscorrespondingtothe90%confidence
(see references in §4.2). Nevertheless, we have re-analyzed
level,unlessnotedotherwise.Asignificantpartofourdiscus-
the data for the entire sample for the sake of uniformity of
sion makes use of the optical-to-X-ray slope of the spectral
analysisandinordertomakeacarefulassessmentofabsorp-
energydistribution,a ,whichisaffectedbyextinction.Thus
ox tion intrinsic to the quasar central engines. To this end we
weexaminetheeffectsofextinctionona indetailintheap-
ox havetestedavarietyofspectralmodels,aswedetailin§4.1.
pendix.
ExploratoryStudyofIntrinsic-NALQuasars 3
TABLE1
SAMPLEQUASARS
QuasarProperties IntrinsicCIVNALProperties
Radio DLb NHGal f2500A◦ c u shiftd RestEW Cfe
Quasar z Loud?a (Gpc) (1020cm−2) (mJy) (kms−1) (A˚)
(1) (2) (3) (4) (5) (6) (7) (8) (9)
Q0014+8118 3.387 L 27.4 14 0.70 ... ... ...
Q0130−4021 3.030 Q 24.0 1.9 0.21 −65,181 0.53 (0.19±0.03),(0.83+0.10),(0.83+0.16),1
−0.09 −0.15
−37,035 0.69f 1,1,1,(0.67±0.03),(0.6±0.1),(0.27±0.03),1
Q1107+4847 3.000 Q 23.7 1.3 0.30 −21,388 0.20 1,(0.70+0.17),1
−0.15
Q1208+1011 3.803 Q 31.5 1.7 0.04 ... ... ...
Q1422+2309 3.611 L 29.6 2.7 0.05 ... ... ...
Q1442+2931 2.670 Q 20.6 1.7 0.47 ... ... ...
HS1603+3820g 2.542 Q 19.4 1.3 0.77 −32,657 0.33 1,1,1,(0.70+0.24),1,(0.87±0.02),1
−0.16
−9,000 2.53–5.07g 0.24–0.45(±0.02)g
+800 0.74 (0.30+0.14),1,(0.23±0.05),1,1
−0.09
Q1700+6416 2.722 Q 21.1 2.7 0.53 −24,195 0.58h 1.00
−23,641 ...h 1.00
−765 0.14 (0.49±0.06),1
aIndicateswhetherthequasarisradio-loud(L)orradio-quiet(Q);fromMisawaetal. (2007b).b Theluminositydistance,computedbasedonthecosmologicalparameters
givenattheendof§1ofthetext.cFluxdensityperunitfrequencyat2500A˚ inthequasarrestframe,derivedfromtheV-orR-bandflux(assumingfn (cid:181) n −0.44;seeMisawa
etal. 2007b)andcorrectedforGalacticextinctionbutnotintrinsicextinction.d VelocityoffsetofaNALrelativetotheredshiftofthequasar. Anegativevaluedenotesa
blueshift.eCoveragefractionsforthekinematic(Voigt)componentsusedtodecomposethelineprofile. EachcomponenthasaFWHMoforder10kms−1(fromMisawaet
al.2007a,b;see§2ofthetext).ThesevalueseffectiverepresentthevariationofCf acrosstheCIVlineprofile.fTheredmemberofthisdoubletisblendedwithanotherline,
buttheequivalentwidthcanbeevaluated.gThisquasarhostsaCIVmini-BALatablueshiftedvelocityof−9,000kms−1.Therest-frameequivalentwidthofthismini-BAL
variessignificantlyovershorttimescales(seeMisawaetal.2007a).ThuswelistarangeofCfvaluestoindicateitstemporalvariability(theerrorbarsarecomparableoverall
epochs,hencewegiveonlyarepresentativevaluehere).hTheselinesarelockedtoeachotherandassuchtheyarejudgedtobeintrinsic. Thecoveragefractionisunityand
onlythetotalequivalentwidthcanbeevaluated.
InTable1wegivethequasarname,redshift,Galacticcol- bothinstrumentsandsomeobjectswereobservedmorethan
umndensity(NGal),andfluxdensityat2500A˚ inthequasar oncewiththesameinstrument,yieldingatotalof6Chandra
H
rest frame, after correcting for absorption in the ISM of the and6XMM-Newtondatasets. InTable2wegivealogofthe
Milky Way, but without any correction for intrinsic absorp- observations, including the observatory and instrument, the
tion.WealsoincludethepropertiesofintrinsicNALs,namely observationidentificationnumber,andthedate.
the offset velocity relative to the quasar redshift2, the rest- Weretrievedthedatafromtherespectivedataarchivesand
frame equivalent width of the intrinsic CIV NALs, and the reducedtheminastandardanduniformmannerusingup-to-
coveragefractionoftheabsorber. Thecoveragefractionwas date calibration data3. The Chandra data were reduced us-
determinedasdescribedinthefirstparagraphofthissection. ing the CIAO 3.3 software package, provided by the Chan-
InTable1welistthecoveragefractionsoftheVoigtcompo- draX-rayCenter(CXC)andfollowingtheCXCthreads. We
nents used to decompose each CIV line profile. These val- screenedthedataaccordingtostatus,photoneventgrade,as-
ueseffectivelyrepresentthevariationofthecoveragefraction pect solution, and background level. We also removed the
acrosstheCIVprofilesinbinsofwidthoforder10kms−1and ±0.′′25randomizationappliedto thephotonpositionsbythe
providethebasisfortheclassificationoftheNALsasintrinsic CXC in order to improve the spatial resolution. The XMM-
(thecoveragefractionissignificantlylowerthanunityinlarge Newton data were reduced with the SAS 6.5 software pack-
portionsofthelineprofile,especiallyclosetothelinecenter). ageprovidedbytheXMM-NewtonScienceOperationCenter
TheclassificationoftheseNALsasintrinsicisalsocorrobo- (SOC). We screened the pn and MOS data to retain events
ratedbysimilarpartialcoverageinformationonotherlinesin withvaluesofthePATTERNkeywordintherange0–4and0–
thesamesystem,suchasNV.InthecaseofQ1700+6416,the 12, respectively. To avoid intervals of high background we
higher-velocityabsorptionsystem listed inTable 1 isjudged excludeddatatakenwhenthe full-fieldcountratesexceeded
tobeintrinsicbasedonthefactthatitislinelocked. 20s−1 inthepnandand4s−1 intheMOS.
We extracted spectra of the target quasars after subtract-
ing the local background. In Table 2, we list the exposure
3. X-RAYOBSERVATIONSANDDATASCREENING
times and number of the counts in the spectra of individual
The8quasarsinoursamplewereobservedwiththeChan- instruments. With the exception of the Chandra spectra of
dra Advanced CCD Imaging Spectrometer (ACIS; Garmire Q1422+2309(taken at three different epochs) there was no
etal. 2003)and/orwith the XMM-NewtonEuropeanPhoton evidenceofpileupinthedata.Oursampleincludestwograv-
ImagingCamera(EPIC)pnandMOSdetectors(Stru¨deretal. itationally lensed quasars, Q1208+1011 and Q1422+2309,
2001;Turneretal. 2001). Someobjectswereobservedwith whichrequiredspecialtreatment. Wegivethedetailsofhow
2Absorption-linesystemsclosetothesystemicredshiftofthequasarare 3 Updates on the calibration of Chandra and XMM-
regardedas“associated”withthequasar,justonthebasisoftheirproximity Newton are available on the WWW sites of the CXC
invelocityspace. However,differentauthorsadoptadifferentvelocitylimit (http://asc.harvard.edu/ciao/releasenotes/history.html)
fortheirdefinitionofassociatedsystems. Themostcommonconventionis and XMM-Newton SOC (http://xmm.vilspa.esa.es/external/
|u shift|≤5,000kms−1 (e.g.,Foltzetal1986), whileBrandtetal. (2000) xmm sw cal/calib/rel notes/index.shtml)
adopt|u shift|≤12,000kms−1.
4 Misawaetal.
TABLE2
OBSERVATIONLOG
Exp.
Quasar Observatory Instr. Obs.ID Date (ks) Counts
(1) (2) (3) (4) (5) (6) (7)
Q0014+8118 XMM-Newton pn 0112620201 2001Aug23 14.3 13348
MOS1 16.9 4866
MOS2 16.9 4827
Q0130-4021 XMM-Newton pn 0112630201 2001Jun04 23.0 1842
MOS1 25.2 499
MOS2 25.3 491
Q1107+4847 XMM-Newton pn 0104861001 2002Jun01 28.1 813
MOS1 32.2 213
MOS2 32.3 253
Q1208+1011 Chandra ACIS-S 3570 2003Mar02 9.97 175
Q1422+2309 Chandra ACIS-S 367 2000Jun01 28.4 426
Chandra ACIS-S 1631 2001May21 10.7 244
XMM-Newton pn 0143652301 2003Feb04 ...a ...a
MOS1 4.89 191
MOS2 4.89 198
Chandra ACIS-S 4939 2004Dec01 47.7 762
Q1442+2931 XMM-Newton pn 0103060201 2002Aug01 21.3 2607
MOS1 24.8 768
MOS2 24.8 753
HS1603+3820 Chandra ACIS-S 4026 2002Nov29 8.30 137
Q1700+6416 Chandra ACIS-S 547 2000Oct31 49.5 325
XMM-Newton pn 0107860301 2002May31 14.1 1060
MOS1 18.3 281
MOS2 18.4 299
aThepnimageofQ1422+2309fellonachipgap,thereforewewerenotabletousethosedata.
we treated these two objects in §4.2, below. The luminosi- the source. The free parameters of this model are the
ties we report for these two quasars have been scaled down photonindex,G ,andthenormalization(i.e.,thephoton
accordingtothemagnificationfactorsreportedin§4.2. fluxperunitenergyat1keV).
4. MODELFITSTOTHEOBSERVEDSPECTRAAND
RESULTS 2. [wabs*zwabs(zpow)] Simple power-law continuum
(attheredshiftofthesource)withintrinsicabsorption.
4.1. SuiteofModelsandFitResults
Thismodelhasanadditionalfreeparametercompared
We fitted a variety of models to the observed X-ray spec- tothepreviousmodel,thecolumndensityoftheintrin-
trausingtheXSPEC12.3.0softwarepackage(Arnaud1996). sic absorber, N . Simple models of this type can un-
H
Allenergychannelsbelow0.4keVwereignored. Thespec- derestimate the column density of the absorber, if the
tra were binnedto havea minimumof 10 countsper bin (in absorberisionizedorifitcoversthesourceonlypartly.
most cases the minimum number of counts per bin was re- Therefore, we also test the more complex absorption
quiredtobehigher;see§4.2forspecificdetails). Inthecase modelslistedbelow.
ofXMM-Newtondata,weperformedjointfitstotheMOSand
pnspectra.
3. [wabs(zpow)+const*wabs*zwabs(zpow)] Power-
We used the suite of models, described below, to fit the
law continuum (at the redshift of the source) with
spectraandselectedthemodelthatgavethebestfit. Itisim-
partialcoverageintrinsicabsorption. Inthismodel,the
portantto findthe mostappropriatemodelsfor the observed
absorberis assumed to coverthe projected area of the
spectrasothatwecandeterminetheintrinsiccolumndensity
X-ray source only partially. The free parameters are
reliably,sincethisisacrucialquantityinoursubsequentdis-
thoseofthepreviousmodelplusthecoveragefraction
cussion. AbsorptionintheISMoftheMilkyWayisincluded
(thefractionofphotonsthatpassthroughtheabsorber).
in all models, using the Galactic column densities from the
HEASARC nH tool4 (NGal, listed in Table 1) and the photo-
H
electricabsorptioncross-sectionsofMorrison&McCammon 4. [wabs*absori(zpow)] Power-law continuum (at the
(1983).Thesecolumndensitieswereheldfixedduringthefit- redshiftofthesource)withionizedintrinsicabsorption
tingprocess. Wherevernecessary,we adopteda Solar abun- (following Done et al. 1992; see also Zdziarski et al.
dance pattern for heavy elements from Anders & Grevesse 1995). The free parametersare the normalizationand
(1989). photonindexofthepower-lawcontinuum,andthecol-
The models we used are outlined below (along with their umn density and ionizationparameter of the absorber,
XSPEC model syntax; Galactic absorption is denoted by x 5. Thetemperatureoftheabsorberwasheldfixedat
wabs). 30,000 K, while the iron abundance was held fixed at
theSolarvalue.
1. [wabs(zpow)] Simple power-law continuum (at the
redshift of the source) without intrinsic absorption at 5 x ≡L/nr2,whereListheluminosityofthesourcebetween5eVand
300keV,risitsdistancefromtheabsorber, andnisthehydrogennumber
4http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/w3nh/w3nh.pl densityoftheabsorber
ExploratoryStudyofIntrinsic-NALQuasars 5
TABLE3
PARAMETERSOFBEST-FITMODELS
Model1: Model2:
SimplePowerLaw PowerLaw&IntrinsicAbsorption ComplexModels
NH NH F-Testd F-Testd
Quasara G cn2/n b G (1022cm−2) cn2/n b Modelc G (1022cm−2) cn2/n b PF(1) PF(2)
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Q0014+8118 1.43±0.02 1.181/383 1.48±0.02 1.1±0.3 1.104/380 3 1.49+0.03 1.3+4.9 1.108/381 2×10−6 0.92
−0.02 −0.2
4 1.48±0.03 1.5+3.4 1.103/379 1×10−6 0.27
−0.6
Q0130−4021 2.01±0.07 1.033/56 1.98+0.13 <0.26 1.066/55 5 2.6+0.5 ... 0.866/55 0.0011 ...e
−0.06 −0.6
Q1107+4847 1.9±0.1 1.315/44 2.0+0.3 <1.6 1.321/43 6 3.3±0.4 <1.7 1.157/42 0.026 0.011
−0.2
Q1208+1011 2.2±0.3 1.106/12 2.0+0.8 <3.3 1.299/11 ... ... ... ...... ...
−0.2
Q1422+2309 1.55+0.15 0.543/13 1.5+0.3 <2.2 0.594/12 ... ... ... ... ... ...
−0.14 −0.2
1.7+0.3 1.175/11 1.5+0.7 <4.3 1.475/10 ... ... ... ... ... ...
−0.2 −0.2
1.4±0.2 0.838/45 1.5+0.4 <4.5 0.852/44 ... ... ... ... ... ...
−0.3
1.6±0.1 1.272/11 1.6+0.3 <2.7 1.430/10 ... ... ... ... ... ...
−0.2
Q1442+2931 1.87±0.05 0.738/67 1.87+0.10 <0.36 0.750/66 ... ... ... ... ... ...
−0.06
HS1603+3820 1.9±0.3 0.891/9 2.00+1.4 <8.4 0.972/8 ... ... ... ... ... ...
−0.5
Q1700+6416 2.2±0.2 1.297/12 2.3+0.5 <5.3 1.407/11 ... ... ... ... ... ...
−0.3
2.1±0.2 0.951/87 2.0+0.3 <0.55 0.967/86 ... ... ... ... ... ...
v −0.2
aQuasarnamesandobservationsareinthesameorderasinTable2.bReducedc 2andnumberofdegreesoffreedom.cModelsaredescribedindetailin§4ofthetext.dF-testprobabilitythatmore
complexmodelsprovideabetterfitthanmodels1and2,respectively.eModels2and5havethesamenumberoffreeparameters,thustheF-testdoesnotgiveameaningfulresult.Forreference,
wenotethatthevaluesofc 2formodels2and5yieldchanceprobabilitiesof0.66and0.25,respectively.
5. [wabs(pexrav)]Power-lawcontinuum(withanexpo-
nential cutoff at 100 keV) “reflected” from a nearly- TABLE4
neutral slab (with solar abundances; see George & BEST-FITPARAMETERSOFMODEL4(IONIZED
ABSORBER)a
Fabian1991;Magdziarz&Zdziarski1995).
6. [wabs*zwabs(pexrav)] Power-law continuum “re- NH
flected” from a nearly-neutral slab with intrinsic ab- Quasar G (1022cm−2) cn2/n b
(1) (2) (3) (4)
sorptionincluded.
Q0014+8118 1.48±0.03 1.5+3.4 1.103/379
−0.6
In addition to the above models we also experimented with
addingaGaussianFeKa linetothesimplepowerlawmodel Q0130−4021 2.00−+00..0185 <7.4 1.000/58
as wellwith brokenpower-lawmodelswith and withoutab- Q1107+4847 2.1+0.3 <7.8 1.202/46
−0.2
sorption.
Q1442+2931 1.87+0.12 <9.9 0.716/69
We find that the simplest models from the above list pro- −0.06
vide an adequate fit to most of the spectra, in part because Q1700+6416 2.0+0.4 <13 0.938/89
−0.2
of the modest signal-to-noise ratio (S/N) of the spectra. In
Figure1,weshowthespectrawiththebest-fittingpowerlaw aThismodelwasfittedonlytotheXMM-Newtonspectrabecause
modelwithintrinsicabsorption(model2)superposed. Inthe thesehappentobetheoneswiththelargestnumberofcountsfor
samefigure,wealsoshowtheconfidencecontoursintheG – eachobject. The quasar Q1422+2309 is anexception; it is so
faintthatitsXMM-Newtonspectradidnotwarrantafitwiththis
NH plane for the same model. In Table 3 we list the best- model.bReducedc 2andnumberofdegreesoffreedom.
fittingvaluesofthephotonindexformodel1(simplepower
law) as well as the photon index and intrinsic column den-
sityformodel2(simplepowerlawwithintrinsicabsorption). In 9 out of 12 spectra the simple power law without in-
In cases where a complex model provides a better fit to the trinsic absorption(model1) providesthe best fit. In another
spectrumthanthesimple,unabsorbedpowerlaw,wealsolist two spectra (Q0130−4021and Q1107+4847),the improve-
thebest-fittingparametersofthecomplexmodel. InTable4 ment in the goodness of the fit resulting from a more com-
we list the values (or limits) of the column density obtained plexmodelisonlymarginal(seeTable3andthediscussionin
from the ionized absorber model (model 4). In this table, §4.2,below). TheremainingobjectisQ0014+8118,theonly
we only includethose objectswhose spectra (typically from casewherewe areableto detectsignificantintrinsicabsorp-
XMM-Newton) included more than 1000 counts and yielded tionwithacolumnof≈1×1022cm−2. Thisquasarhappens
“interesting”results. tobethebrightestquasarinoursamplebyfar,withmorethan
6 Misawaetal.
2.2
Q0130−4021
v)−1 XMM−Newton/EPIC
ke
Rate (s −1 0.01 2.1
nt
Cou 10−3 GN H= < 1 .09.826· 1022 cm−2 G 2+
2
Q0130−4021
sual/ 0 1.9 XMM−Newton/EPIC
Resid −2 GN H= < 1 .09.826· 1022 cm−2
0.5 1 2 5 1.80 0.1 0.2 0.3 0.4 0.5
Energy (keV)
N (1022 cm−2)
H
Q1107+4847
v)−1 0.01 XMM−Newton/EPIC 2.4
ke
Rate (s −1 10−3 2.2
unt 10−4
o
C N = 0.47· 1022 cm−2 G 2 +
G H= 2.02
10−25 Q1107+4847
sResidual/ −101 1.8 XMGN MH= = −2 N.00.e24w7t·o1n0/E22P cImC−2
−2
0.5 1 2 5 10 1.60 0.5 1 1.5 2 2.5
Energy (keV) N (1022 cm−2)
H
5
3.
Q1208+1011
v)−1 0.01 Chandra/ACIS−S
ke
Rate (s −1 5×10−3 3
nt 2×10−3
u
Co 10−3 GN H= < 2 .30.429· 1022 cm−2 G 2.5
1 Q1208+1011
sdual/ 0 2+ Chandra/ACIS−S
Resi −1 NG H= < 2 .30.429· 1022 cm−2
0.5 1 2 1.50 2 4 6
Energy (keV)
N (1022 cm−2)
H
FIG. 1.—LeftColumn: Observed-framespectrawiththebest-fittingversionofmodel2(simplepowerlawwithintrinsicabsorption)superposed. Themodel
parametersaresummarizedinTable3.RightColumn:The68,90,and99%confidencecontoursintheG –NHplaneformodel2.The90%upperlimitstoNHare
summarizedinTable3(inthecaseofQ0014+8118weareabletodetermineanintrinsiccolumndensitywhichisnotconsistentwithzero.
ExploratoryStudyofIntrinsic-NALQuasars 7
0.01
Q1422+2309 (1)
kev)−1 5×10−3 Chandra/ACIS−S 2
Rate (s −1 2×10−3
nt
u
Co 10−3 GN H= < 1 .25.224· 1022 cm−2 G 1.5+
5×10−4
1 Q1208+2309 (1)
sResidual/ −00..550 CGN hH=a < n1 d.25r.22a4/A· C10IS22− cSm−2
−1
0.5 1 2 5 10 1 2 3 4
Energy (keV) N (1022 cm−2)
H
0.02 Q1422+2309 (2) 2.5
v)−1 Chandra/ACIS−S
ke 0.01
Rate (s −1 5×10−3 2
nt
u
o 2×10−3
C N < 4.31· 1022 cm−2 G
G H= 1.52
10−3
2 1.5+ Q1422+2309 (2)
sResidual/ 01 CNG hH=a < n1 d.45r.23a1/A· C10IS22− cSm−2
1 2 10 2 4 6 8
Energy (keV) N (1022 cm−2)
H
Q1422+2309 (3)
kev)−1 0.01 XMM−Newton/EPIC 2
Rate (s −1 10−3
nt
u
o
C 10−4 GN H= = 1 .04.864· 1022 cm−2 G 1.5 +
2 Q1422+2309 (3)
sual/ 1 XMM−Newton/EPIC
Resid −10 NG H= = 1 .04.864· 1022 cm−2
0.5 1 2 5 10 10 2 4 6 8
Energy (keV) N (1022 cm−2)
H
0.01 Q1422+2309 (4)
Rate (s kev)−1−1 5×10−3 Chandra/ACIS−S 2
nt 2×10−3
u
o
C 10−3 GN H= < 1 .25.868· 1022 cm−2 G 1.5+
2
Q1422+2309 (4)
sual/ 1 Chandra/ACIS−S
Resid −10 GN H= < 1 .25.868· 1022 cm−2
1 2 1
0 2 4
Energy (keV)
N (1022 cm−2)
H
Fig.1.—Continued
8 Misawaetal.
0.1 2.1
Q1442+2931
v)−1 XMM−Newton/EPIC
ke
Rate (s −1 0.01 2
nt
u
Co 10−3 NG H= < 1 .08.736· 1022 cm−2 G 1.9+
2
Q1442+2931
sResidual/ −101 1.8 XMGN MH= < −1 N.08.e73w6t·o1n0/E22P cImC−2
−2
0.5 1 2 5 10
0 0.2 0.4 0.6
Energy (keV)
N (1022 cm−2)
H
0.01 HS1603+3820
v)−1 Chandra/ACIS−S 4
ke
Rate (s −1 5×10−3
nt 2×10−3 3
u
o
C N = 0.75· 1022 cm−2 G
10−3 G H= 2.00
1 2 + HS1603+3820
sResidual/ −10 CGN hH=a = n2 d.00r.07a5/A· C10IS22− cSm−2
1
1 2 0 5 10 15
Energy (keV) N (1022 cm−2)
H
5×10−3 3.5
Q1700+6416 (1)
v)−1 Chandra/ACIS−S
ke 2×10−3
Rate (s −1 10−3 3
nt 5×10−4
u
Co 2×10−4 GN H= = 2 .02.758· 1022 cm−2 G 2.5 +
1 Q1700+6416 (1)
sual/ 0 2 Chandra/ACIS−S
Resid −1 GN H= < 2 .02.758· 1022 cm−2
−2
5
1 2 5 1.0 2 4 6 8 10
Energy (keV)
N (1022 cm−2)
H
Q1700+6416 (2)
v)−1 XMM−Newton/EPIC
Rate (s ke−1 0.01 22.4
nt 10−3 2.
u
o
C NG H= < 2 .00.055· 1022 cm−2 G 2+
10−4
2 Q1700+6416 (2)
sResidual/ −20 1.8 XMGN MH= < −2 N.00.e05w5t·o1n0/E22P cImC−2
0.5 1 2 5 10 1.60 0.5 1
Energy (keV)
N (1022 cm−2)
H
Fig.1.—Continued
ExploratoryStudyofIntrinsic-NALQuasars 9
13,000 counts in its XMM-Newton pn spectrum; we discuss
thiscasefurtherin§4.2and§6.3.Thebest-fittingvaluesofthe TABLE5
photonindexareintherange1.5–2.3,whicharewellwithin FLUXDENSITIES,INTEGRATEDFLUXES,ANDa oxOFSAMPLEQUASARS
the range of photon indices found in radio-quiet quasars at
z=2–3(Vignalietal. 2001). F(2–10keV)a L(2–10keV)b f2keVc
Thus, our primary observational result consists of the up- Quasar (ergs−1cm−2) (ergs−1) (nJy) a oxd D a oxe
(1) (2) (3) (4) (5) (6)
per limits on (and one measurement of) the column density
of a nearly-neutral absorber in the rest frame of the quasar. Q0014+8118 3.6×10−12 1.5×1047 126 −1.44 0.42
These were determined in a uniform and systematic fashion Q0130−4021 8.3×10−14 5.8×1045 11.3 −1.63 0.14
Q1107+4847 3.2×10−14 2.0×1045 3.65 −1.88 −0.09
usingtheabsorbedpower-lawmodel(model2)andarelisted
Q1208+1011 3.2×10−14f 1.7×1045 2.36 −1.61 0.11
in column 5 of Table 3. The limits correspond to the 90% Q1422+2309 7.1×10−14g 1.1×1045 0.93 −1.81 ...
confidence intervals shown in the contour plots of Figure 1 9.4×10−14g 1.7×1045 1.61 −1.72 ...
andareoforder1022cm−2. Theuseofmorecomplexmodels 8.7×10−13f 2.4×1045 1.86 −1.69 ...
didnotresultinmorerestrictivelimits(mostlikelybecauseof 8.3×10−14g 1.4×1045 1.29 −1.75 −0.03
thelargernumberoffreeparametersinthese models). Thus Q1442+2931 1.6×10−13 7.0×1045 16.5 −1.70 0.10
thelimitsin column5ofTable3 alsoincorporatethe uncer- HS1603+3820 5.8×10−14 2.3×1045 6.1 −1.96 −0.15
Q1700+6416 2.5×10−14 1.7×1045 5.06 −1.92 ...
taintyresultingfromtheuseofmorecomplexmodelsforthe
8.6×10−14 4.8×1045 12.5 −1.77 −0.04
continuum. We notethatthese limitsareconsiderablylower
than the intrinsic columndensities detectedin BAL quasars, aThe2–10keVfluxintheobservedframe,correctedforabsorptionintheISMoftheMilky
NH =1023−24 cm−2 (e.g., Gallagher et al. 2006, and refer- Way(andforintrinsicabsorptioninthecaseofQ0014+8118).b Therest-frame2–10keV
ences therein). In the case of an ionized absorber, the data luminosity,correctedforabsorptionandscaleddowntoaccountforthelensingmagnifica-
allow for higher column densities. The corresponding lim- tioninthecaseofthetwolensedquasars,Q1208+1011andQ1422+2309.cTherest-frame
fluxdensityperunitfrequencyatanenergyof2keV(correctedforMilkyWayabsorption
itswerederivedinthesamefashionasforthenearly-neutral butnotintrinsicabsorption;see§5). Theuncertaintiesare ∼<10%.d Theoptical-to-X-ray
absorberand they turn outto be approximatelyone orderof spectralindexcomputedfromequation(2)withoutcorrectionsforintrinsicabsorption. The
magnitudehigherthanthaninthecaseoftheneutralabsorber. uncertaintiesarediscussedin§5ofthetext.eThedifferencebetweentheobservedvalueof
Theyarelistedincolumn3ofTable4. a oxandthevalueexpectedbasedontheUVluminosityofthequasar(seedetailsin§5ofthe
Wealsosearchedforabsorptionlinesinthevicinityofthe otebxste).rvFaotiroqnuwasiathrstwheithhimghuelstitpSle/NX.-fraTyootablseorbvsaetrivoends,flwuexoonflyalrlelpeonrstetdheimvaalgueesocfoDmaboinxefdo,rnthoet
Fe Ka transition by adding an unresolved (s =0.01 keV) correctedformagnification(seenotesin§4.2).gObservedfluxofimageConly,notcorrected
Gaussian line with negative normalization to the power-law formagnification(seenotesin§4.2).
continuum. Thiswasmotivatedbythe detectionof suchab-
sorption lines in high-redshiftquasars by severalauthors, as )
1
–
we discuss further in §6.4. Our search yielded interesting s
2
limitsonlyinthecase ofQ0014+8118,whichhasbyfarthe –
m
highest-S/N spectra of all the quasarsin our sample. These s c – 1
limits are shown graphically in Figure 2 where we plot the n
o
normalizationoftheGaussiancomponent(i.e.,theintegralof ot 68%
h
theGaussian)asafunctionofrest-frameenergyinthespec- 5 p – 2
trum. Given the redshift of this quasars and its continuum –0 90%
1
photonindex,wecanrelatetheabsolutevalueofthenormal- n ( 3
iwzaidtitohn,Worfestth,eanGaalyutsisciaalnlylianse, K, to the rest-frame equivalent alizatio – 99%
Wrest =26 (cid:18)4×10−5Kcm−2s−1(cid:19) (cid:18)6.E4rkesetV(cid:19)1.48 eV, (1) e Norm – 4
n
where E is the rest-frame energy of the absorption line. Li 6 6.5 7 7.5 8 8.5
rest
Thus,accordingtoFigure2,atarest-frameenergyof6.7keV Rest-Frame Line Energy (keV)
the 99% upper limit to the absolute value of the equivalent
width is 28 eV, while at a rest-frame energy of 7.4 keV this FIG.2.—Limits(at68%,90%,and99%confidence)onthenormalization
of an unresolved Fe Ha absorption line in the spectrum of Q0014+8118.
limitis13eV.
Theprofile of the line is assumedto be Gaussian and it is superposed on
thepower-lawcontinuum.Thelinenormalizationcanbetranslatedtoarest-
4.2. NotesonIndividualQuasars frameequivalentwidthusingequation(1).
Q0014+8118.— Page et al. (2004) presented the XMM-
Newtonspectrumofthisquasarintheiranalysisofthe tially covered, neutral absorber models, and the ion-
X-ray Baldwin effect. We reduced the same XMM- ized absorber model (models 2, 3, and 4) yield a sig-
Newtondatatakenon2001August23for14.3ks(pn) nificantly better fit than the simple power-law model
and16.9ks(MOS)(Obs-ID:0112620201,PI:Turner). (model 1), as shown by the F-test (see chance prob-
Thespectrumwasbinnedwithaminimumof50counts abilities in Table 3). The ionized absorber model of
per bin. The rest-frame 2–10 keV luminosity that we Done et al. (1992), as implemented in XSPEC, is not
obtain is in good agreement with that of Page et al. self-consistent, therefore its results must be regarded
(2004);theydonotreportanyoftheparametersofthe with caution. In particular, the temperature and ion-
best-fitting model. This is the only object in which ization parameter are treated as independent parame-
we detect an intrinsic absorber unambiguously, with tersinsteadofbeingcalculatedself-consistentlyfroma
a column of ≈ 1×1022 cm−2. The fully and par- fullphotoionizationmodel. Therefore,we verifiedthe
10 Misawaetal.
results using a rigorous photoionization model, com- asmodel1(simplepower-lawmodel)andmodel2(ab-
putedbythecodeXSTAR6 (Kallmanetal. 2004). The sorberpower-law).
latter model yielded a column density for the ionized
absorberofNH=(2.5±2.0)×1022cm−2 andanion- Q1208+1011.— Thisgravitationallylensedquasarwasorig-
ization parameter of logx XSTAR =1.7±0.7 (where x inallyfoundbyHazard,McMahon,& Sargent(1986).
is in units of erg cm s−1). In comparison, the fit with Itcomprisestwosplitimagesseparatedby0.′′47witha
model 4 (absori)yields N =(1.5+3.4)×1022cm−2 brightness ratio of about 4, based on the observations
H −0.6
and an ionization parameter of logx <2.2, cor- with ground-based telescopes (Magain et al. 1992)
absori
responding to logx <1.97, consistent with the andtheHubbleSpaceTelescope(HST)(Bahcalletal.
XSTAR 1992b). Giallongo et al. (1999) derived a total mag-
XSTARresults.
nificationfactorof m =22,whichwaslaterrevisedto
t
Models2,3,and4,aswellastheXSTAR-basedmodel, m =3.1 by Barvainis & Ivison (2002). We extracted
t
appeartoprovideequallygoodfitstothespectrum,in- thespectrumofthisquasarbysummingthecountsfrom
dicating that excess absorption is present in the spec- allimagesandthenscaleddowntheluminosityaccord-
trum of Q0014+8118but the properties of the ioniza- ingtothelattermagnificationfactorlistedabove.
tionstateandcoveragefractionoftheabsorberarenot
Dai et al. (2004) analyzed the Chandra data of this
wellconstrained.Thus,weadoptmodel2asthework-
quasar and fitted the spectrum with a power law and
ing model for this object in the discussion below be-
a Gaussian emission line without intrinsic absorption.
causeitisthesimplestone. However,wereturntothis
Theyfoundabest-fittingphotonindexofG =2.3±0.2
casein§5and§6todiscusstheimplicationsofthemea-
andderivedvalueofa =−1.62. Werepeatedthere-
suredcolumndensityandtoconstrainthelocationand ox
duction of the same Chandra data (Obs-ID: 3570 PI:
properties of the absorber with the help of additional
Garmire). The spectrum was binned with a minimum
evidence.
of 10 countsper bin. The spectralparametersthat we
derive are consistent to those obtained by Dai et al.
Q0130-4021.— Pageetal. (2003)searchedforAGNsinthe
(2004).
XMM-Newton field of this quasar, and detected 9 ob-
jects including Q0130−4021 itself. We reduced the
same XMM-Newton data taken on 2001 June 04 for Q1422+2309.— This is a gravitationally-lensed,radio-loud
23.0ks(pn)and25.2ks(MOS)(Obs-ID:0112630201, quasar,consistingof4images.Kormann,Schneider,&
PI:Turner).ThepnandMOSspectrawerebinnedwith Bartelmann (1994) explored lensing models based on
a minimum of 50 and 30 counts per bin, respectively. ellipticalmassdistributionandderivedatotalmagnifi-
Model5(powerlawplusComptonreflection)provides cation factor of m t =15.38. Three Chandra (Obs-ID:
amarginallybetterfitthanmodel1(simplepower-law 367, 1631, and 4939 PI: Garmire) and XMM-Newton
model) to the XMM-Newton spectrum of this object, observations(Obs-ID:0143652301PI:Georgantopou-
P (1)=0.0011 (see Table 3). However, the fit with los)werecarriedoutoveraspanoffouryears. Among
F
model5 appearsto be as goodas the fit with model2 thefourlensedimagesresolvedbyChandra,thebright-
(absorberpower-law). esttwoimagesareprobablyaffectedbypileupatleast
in their central few pixels (Grant et al. 2004). Since
Q1107+4847.— XMM-Newtonobservedthistargettwiceon thefaintestimageisnotbrightenoughtobedetectedin
2002 April 25 and June 1. The analysis of the sec- the Chandra data, we extracted a spectrum only from
onddatasetwaspresentedbyBrocksoppetal. (2004). imageC, the thirdbrightestimage. Themagnification
They fitted the spectra with a power law model with factorforthisparticularimage, accordingtoKormann
photonindexofG =1.96andobtainedanupperlimiton etal. is m C =3.43, thuswe scaled downthe luminos-
the intrinsicabsorptionofN <1.5×1022 cm−2 with ity accordingly. The spectra from the three Chandra
H
99%confidence.WeexaminedbothXMM-Newtondata observations were binned with a minimum of 25, 15,
sets(Obs-ID:0059750401and0104861001,PI:Mann and 50countsperbin, respectively. Inour analysisof
and Mason), butreducedonlythe secondonebecause theXMM-Newtonobservation,we usedonlytheMOS
the first observationwasperformedduringa periodof databecauseinthepntheimagefellonachipgap.We
high background (background-to-signalratio is >20). summedallthecountsfromtheMOSimagessincethe
ThepnandMOSspectrawerebinnedwithaminimum four lensed images were not resolved. We binned the
of 50 and 15 counts per bin, respectively. The results extracted spectrum with a minimum of 10 counts per
ofourfitsareconsistentwiththeresultsofBrocksopp bin and we scaled down the luminosity by a factor of
et al. (2004). Model 6 (power law plus Compton re- m tot =15.38.
flection and intrinsic absorption) provides an equally
good fit to the XMM-Newton spectrum of this object Q1442+2931.— AnanalysisoftheXMM-Newtonspectrum
of this quasar was presentedby Ferrero& Brinkmann
6http://heasarc.gsfc.nasa.gov/docs/software/xstar/xstar.html (2003). They fitted with a power-law and obtained a
7 Theionization parameters intheXSTARandabsori models arede- photon index of 1.87. They found no evidence of an
fined in a slightly different way. The former involves the continuum lu- Fe Ha line. We re-analyzed the same XMM-Newton
minosity from 1 Ry to 1000 Ry, while the latter involves the continuum
luminosity from 5 eV to 300 keV. They can be related if one assumes a data (Obs-ID: 0103060201, PI: Aschenbach). The
specific shape for the spectral energy distribution. Here we make the as- spectrawerebinnedwith aminimumof50countsper
sumption that the spectral energy distribution is that of Mathews & Fer- bin. Our derived values of the photon index and of
land(1987)butwechangetheX-rayphotonindexto1.49sothatitagrees a are consistentwith thoseof Ferrero& Brinkmann
withwhatwemeasureforQ0014+8118. Underthisassumptionwefindthat ox
logxabsori−logxXSTAR=0.262. (2003).