HE 0141-3932: a bright QSO with an unusual emission line spectrum and associated absorption

0.77 MB·English

by  D. Reimers

Astronomy&Astrophysicsmanuscriptno.lev February2,2008
(DOI:willbeinsertedbyhandlater)
HE 0141–3932: a bright QSO with an unusual emission line
⋆
spectrum and associated absorption
1 1 1 2 2 3
D.Reimers ,E.Janknecht ,C.Fechner ,I.I.Agafonova ,S.A.Levshakov ,andS.Lopez
1 HamburgerSternwarte,Universita¨tHamburg,Gojenbergsweg112,D-21029Hamburg,Germany
5 2 DepartmentofTheoreticalAstrophysics,IoffePhysico-TechnicalInstitute,194021St.Petersburg,Russia
0
3 DepartamentodeAstronomia,UniversidaddeChile,Casilla36-D,Santiago,Chile
0
2
receiveddate;accepteddate
n
a
J Abstract.HE0141–3932(zem=1.80)isabrightblueradio-quitequasarwithanunusuallyweakLyαemissionline.Large
redshiftdifferences(∆z =0.05)areobservedbetweenhighionizationandlowionizationemissionlines.Absorptionsystems
8
2 identifiedatzabs=1.78,1.71,and1.68showmildoversolarmetallicities(Z ≈1−2Z⊙)andcanbeattributedtotheassociated
gascloudsejectedfromthecircumnuclearregion.Thejointanalysisoftheemissionandabsorptionlinesleadstotheconclusion

1 thatthisquasarisseenalmostpole-on.ItsapparentluminositymaybeDopplerboostedby∼10times.Theabsorbinggasshows
v ahighabundanceofFe,MgandAl ([Fe,Mg,Al/C]≃ 0.15±0.10)alongwithunderabundanceofN ([N/C]≤ −0.5).This
9 abundance patternisatvariancewithcurrentchemicalevolutionmodelsofQSOspredicting[N/C] > 0and[Fe/C]< 0at
∼
2 Z ∼Z⊙.
6
1 Keywords.Cosmology:observations–Line:formation–Line:profiles–Galaxies:abundances–Quasars:absorptionlines
0
–Quasars:individual:HE0141–3932
5
0
/
h 1. Introduction 3932isaradio-quietquasar,i.e.notablazar.Afewotherblue
p
radio-quietquasarsareknownwithapparentlymissingorweak
- In the course of a high-resolution study of the Lyα forest at
o Lyα emission but clearly present metal lines: PG 1407+265
r intermediate redshifts (1.5 ≤ z ≤ 2) in bright quasars from [z = 0.94, McDowell et al. (1995)], Tol 1037–2703 [z =
t em em
s theHamburg/ESOSurveywiththeUV-visualechellespectro- 2.20, Srianand & Petitjean, (2001)], PHL 1811 [z = 0.192,
a graph(UVES)attheVLT,thediscoveryspectrumoftheQSO em
Leighly, Halpern, & Jenkins (2004)], and several cases from
:
v HE 0141–3932(z ≃1.8,B = 16.2,Wisotzkietal.2000)at-
SDSS(Fanetal.1999,2003).Thenatureoftheirpeculiaremis-
i tractedourattentionbytwofacts:itappearedtohavenooronly
X sionlinespectraisnotclear.
veryweakLyαemissionalongwithclearlyrecognizableMgII,
r
a and it showed several absorption line systems at zabsranging In particular, Leighly et al. (2004) suggest a high accre-
from1.78to1.68withverycomplexandstrongmetalprofiles tion rate which powers the UV emission from an optically
whichallowustosuggestthatthesesystemsmayoriginatein thick accretiondisk, while suppressingthe formationof a hot
theejectedgas. corona. However, recent radio observations of PG 1407+265
SincetheidentificationspectrumofHE0141–3932wasof on the milliarcsecond scale revealed a relativistic jet of mod-
only moderate quality, we took furtherlow-resolution spectra erate powerbeamed toward us (Blundell, Beasley & Bicknell
with EFOSC 2 with the ESO 3.6 m telescope to improve the 2003).Thismeansthatthequasarisseenalmostpole-onandits
redshiftmeasurementandwefoundathirdpeculiarity,namely emissionlinespectrummaybedilutedbycontinuumradiation
largeredshiftdifferences(∆z ∼0.05)betweenhighionization bothfromthejetandtheaccretiondisk.
andlowionizationemissionlines.
EmissionlinespectrasimilartothatofHE0141–3932are Inthepresentpaperweanalyzeboththeemissionandab-
observedinsome highredshiftBL Lacertae(BL Lac)objects sorption line spectra of HE 0141–3932. We expect that this
(Urry&Padovani1995,hereafterUP95).However,HE0141– jointconsiderationmayshedsomelightontheunusualproper-
tiesofthisquasar.
Sendoffprintrequeststo:S.A.Levshakov,
The paper is organized as follows: observations are de-
[email protected]
⋆ BasedonobservationsobtainedattheVLTKueyentelescopeand scribed in Sect. 2, the emission lines are studied in Sect. 3,
3.6mESOtelescope,Chile,theESOprogramsNo.67.A-0280(A)and theanalysisofthezabs≈zemabsorbersisgiveninSect.4,the
72.D-0174A,respectively. resultsarediscussedandsummarizedinSect.5.
2 D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption
Fig.1.EFOSC2spectraofHE0141–3932.Thespectralresolutionsareindicatedinthepanels.Allidentifiedemissionfeatures
arelabeled.TheparametersoftheprominentemissionlinesarelistedinTable2
2. Observations 3. Theemissionline spectrum
HE 0141–3932wasobservedwith theUVESat the8 m ESO The combinationof EFOSC 2 spectra with roughly flux cali-
VLTonParanalover7nightsinJuly/August2001.Elevenin- bratedUVESspectraallowsustoestimateredshiftsandequiv-
dividualexposureswithintegrationtimesof60minweremade alentwidthsofallemissionlinesbetweenLyαandMgIIλ2800
usingthedichroicmodeinstandardsettings(Table1).Witha A˚. Equivalent widths (EW) and redshifts were measured by
slitwidthof1′′,aresolutionof41000(7.3kms−1)intheblue fitting Gaussian profiles to the data. Table 2 presents the re-
and38000(7.9kms−1)intheredisachieved. sults. The Lyα EW is relatively uncertain since in the cali-
The data reduction was performed at the Quality Control bratedUVESdatathe continuumis difficultto determineand
Group in Garching using the UVES pipeline Data Reduction thebluewingofthelineisincomplete(seeFig.1and2).
Software (Ballester et al. 2000), the vacuum-barycentric cor- Theidentificationoftheemissionlineat∼3400A˚ isam-
rectedspectrawereco-added.Theresultingsignal-to-noisera- biguous:itcouldbeeitherLyαatz =1.80orNVatz =1.75
tio,S/N,istypically75. orblendofbothlines.Therearetwoargumentsinfavorofthe
Since both the Lyα and the MgII emission line ranges NVidentification:ithasawidthcomparabletoCIVanditsred-
are covered only by UVES spectra, we performed an ab- shift–ifidentifiedasNV–isequaltothatoftheCIV,whilein
solute flux calibration using an appropriate master response QSOs with significant redshift differences between high ion-
curve and the respective airmasses during the observa- ization lines (CIV) and low ionization lines (MgII, Hα), the
tions. The procedure is described on the ESO web page Lyαlinetypicallyisfoundattheredshiftofthehighionization
www.eso.org/observing/dfo/quality/UVES/qc/response.html. BLRemissionlines(Gaskell,1982;Espeyetal.,1989).Onthe
FurtherspectraweretakenwithEFOSC2attheESO3.6m otherhand,theemissionlineat3400A˚ isquitestrongforNV,
telescopeonOctober2,2003,toimproveourknowledgeabout althoughtherearequasarsknownwithNV strengthcompara-
the redshifts of the emission lines. Details are given in Table bletothatofCIV(Halletal.2004;Baldwinetal.2003b).Even
1.Wavelengthandfluxcalibrationwasperformedaccordingto ifthislinewouldbeentirelyduetoemissionofneutralhydro-
standardprocedures.TheresultingspectraareshowninFig.1. gen,wecanconcludethatLyαinHE0141–3932isunusually
Noticethatduetotherapidlydecreasingsensitivitybelow3500 weak.
A˚, the EFOSC 2 spectra only partially cover the wavelength The second anomaly of this quasar is the large velocity
rangeexpectedfortheLyαemissionline. difference between low ionization lines (MgII, CIII], AlIII
D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption 3
Table1.LogofspectroscopicobservationsofHE0141–3932
Instrument λλ Exposure Date Resolution
(A˚) time(h) (kms−1)
UVES 3053–3872 7 7.3
4700–5800 7 July+ 7.3
5800–6800 7 August 7.8
UVES 3761–4982 4 2001 7.3
6650–8550 4 7.8
8600–10400 4 7.8
EFOSC2 3270–5240 0.25 Oct.2 420 (6A˚)
3380–7520 0.25 2003 700 (13A˚)
etc.) and high ionization lines (CIV, SiIV) of roughly 5000
kms−1;itisamongthemostextremecaseslikePG1407+265
(McDowelletal.1995,∆vMgII−CIV ≃ 5000kms−1)andQ
1309–056(Espeyetal.1989,∆vMgII−CIV ≃4000kms−1).
InFig.2wedisplaytheemissionlineprofilesonavelocity
scale relative to z = 1.80. The redshift of the low ionization
linesofz = 1.80appearstoberoughlythesystemicredshift,
since the UVES spectrum shows that the Lyα forest starts at
z =1.8086.
While the velocityshift in the emission lines is extremely
large,howunusualaretheemissionlineintensities?Thiscan
bebestseenbyacomparisonwiththehistogramofequivalent
widths of the LBQS-quasars, a well selected sample of QSO
givenbyFrancis(1993).TheLyα,CIV,CIII]andMgIIequiv-
alent widths are among the bottom 2%, 1%, 13% and 1.5%,
respectively, of the Francis (1993) distribution. At the same
time,theAlIII1856/64andFeIII2075linesappearunusually
strong. In order to investigate the physical properties of gas
which could producesuch an unusualemission line spectrum
wecomparedtheobservedequivalentwidthsofHE0141–3932
withthecompilationofquasarBLRrest-wavelengthemission
lineequivalentwidthsgivenasfunctionsofcolumndensity,in-
cidentionizingspectrum,andmetalabundanceoftheemitting
gas clouds (Korista et al. 1997). While Lyα, MgII and CIII]
haveroughlythesamevelocity(redshift)andcouldoriginatein
thesamevolume,wewereunabletofindaparametercombina-
tionwhichmettheconstraintsonLyαandMgIIlinestrengths
simultaneously–thetheoreticalLyαisalwaysmuchtoostrong
Fig.2. Emission lines of HE 0141–3932(spectra fromUVES
foraparametercombinationthatmatchestheMgIIequivalent andEFOSC 2).v = 0 kms−1 correspondsto z = 1.80.For
width.TheCIV/LyαEW ratiocanbemetassuminghighgas orientation,atv =0kms−1 andv =−5000kms−1 dashed
densities[logn(H)≥12],butthediscrepantredshiftsexclude
linesareplotted
formationinthesamelocation.AmeanBLRparametersetap-
pearstobeunabletoreproducethemeasuredEWsofemission
linesinHE0141–3932.
TheMCIisbasedontheassumptionthatalllinesobserved
intheabsorptionsystemareformedinacontinuousabsorbing
4. Theabsorptionsystems gasslabofthicknessL wherethegasdensity,n (x), andve-
H
locity,v(x),fluctuatefrompointtopointgivingrisetocomplex
4.1. Calculationprocedure
profiles(herexisthespacecoordinatealongthelineofsight).
In orderto estimate the physicalparametersof the absorption We also assume that within the absorber the metal abun-
systems we used the Monte Carlo Inversion (MCI) method. dances are constant, the gas is optically thin for the ionizing
Detailed description of the MCI is given in Levshakov et al. UVradiation,andthegasisinthermalandionizationequilib-
(2000,2002,2003a).Hereweoutlinebrieflyitsbasicsneeded rium. The intensity and the spectral shape of the background
tounderstandtheresultspresented. ionizingradiationaretreatedasexternalparameters.
4 D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption
Table2.Estimatedequivalentwidths,redshifsandrelativevelocitiesforemissionlinesofHE0141–3932
Ion Instrument EWrest,A˚ zobs v,kms−1 Comment
HI1215 UVES 16±7 1.80+−00..0012 0+−12017400 asymmetric
and/orNV1239 1.75±0.01 −5350±1070
SiIV1398+OIV]1402 EFOSC2 11±1 1.76±0.01 −4280±1070 —
CIV1549 EFOSC2 14±1 1.75±0.01 −5350±1070 asymmetric
AlIII1858+ EFOSC2 13±1 1.79±0.01 −1070±1070 —
CIII]1909+SiIII]1892 1.79±0.01 −1070±1070 blend,fractionsofcomponentsunknown
FeIII2075 EFOSC2 5±1 1.80±0.01 0±1070 —
MgII2800 UVES 16±1 1.795±0.005 −535±535 blendedwithFeIIemission
Zerovelocitycorrespondstoz =1.80.Onlystatisticalerrorsareindicated.
The radial velocity v(x) and gas density n (x) are con- (Fig. 3) separatedby 2000 km/sfromthe centralsource.The
H
sidered as two continuousrandom functionswhich are repre- bluewingofLyαispartiallyblendedbytheadjacenthydrogen
sentedbytheirsampledvaluesatequallyspacedintervals∆x. line[N(HI)∼1014cm−2]fromaninterveningabsorber(only
The computational procedure is based on adaptive simulated a weak CIV doubletis detected in this system). CIII λ977 is
annealing. The fractional ionizations of different elements at beyond the wavelength coverage and SiIII λ1206 is blended,
each space coordinate x, Υ [U(x)], are computed with the probablywithLyαabsorptionfromthez =1.7606.
ion abs
photoionizationcodeCLOUDY(Ferland1997).
We started the analysis assuming standard ionizing back-
The following physical parameters are directly estimated groundssuchasapowerlawf ∝ν−α(withdifferentindexes
ν
bytheMCIprocedure:themeanionizationparameterU ,the
0 α = 1.0−1.8),themeanintergalacticspectrum(atz = 1.8)
total hydrogen column density N , the line-of-sight velocity
H of Haardt & Madau (1996), and the AGN-type spectrum of
dispersion,σ ,anddensitydispersion,σ ,ofthebulkmaterial
v y Mathews&Ferland(1987,hereafterMF).
[y ≡ n (x)/n ], and the chemicalabundancesZ of all ele-
H 0 a
mentsinvolvedin the analysis. With these parameterswe can Noneofthesespectrawasconsistentwiththeobservedin-
furthercalculatethecolumndensitiesfordifferentspeciesN , tensitiesoftheCII, CIV,SiII andSiIV lines:alltrialsunder-
a
andthemeankinetictemperatureT . produced CII/CIV and overproduced SiII/SiIV, but the MF
kin
spectrum provided the lowest χ2. All spectra gave the mean
In general, the uncertainties on the fitting parameters U ,
0 ionizationparameterintherangeof−2.75< logU < −2.5.
N , σ , σ , and Z are about 15%–20% (for data with S/N ∼ 0 ∼
H v y a
Inspiteofthesaturation,theneutralhydrogencolumndensity
> 30)andtheerrorsoftheestimatedcolumndensitiesareless
∼
can be estimated with a sufficiently high accuracy (∼ 20%)
than10%.However,inindividualabsorptionsystemstheaccu-
sincethevelocitydispersionofgasisdeterminedbynumerous
racyoftherecoveredvaluescanbelowerfordifferentreasons
metal lines detected in this system (the procedure to restore
likepartialblendingofthelineprofiles,saturation,orabsence
partly blended profiles is described in Sect. 3 in Levshakov
oflinesofsubsequentionictransitions.
et al. 2003a). All runs with differentmodel spectra showed a
The MCI can be supplemented with an additional proce-
rather high metallicity – slighty above solar value, and an al-
dure aimed at restoring the shape of the backgroundionizing
mostsolarratioofSi/C.
spectrum. A formal description of this procedure is given in
the Appendix.Its accuracydependssignificantlyon the num- Taking into account this preliminary information we can
ber of unsaturated lines of the subsequentionic transitions of assume that the UV spectrum to be found should maximize
different elements (e.g. SiII/SiIII/SiIV, CII/CIII/CIV) avail- the product of ratios CII/CIV and SiIV/SiII in the range of
ablefortheanalysis.Theabsorberatz =1.7817(described U ∼ 0.002−0.003forsolarmetalcontentandsolarelement
abs 0
below)revealsenoughsuchlinesandweusethemtoestimate abundances. The spectral shape of the MF spectrum can be
thespectralshapeofthebackgroundUVradiationintherange takenasafirstapproximation(formoredetailsseeAppendix).
E >1Ryd.
Applying the adjustment procedure as described in
All calculations are carried out with the laboratory wave-
Appendix, we estimated a new shape of the ionizing spec-
lengths and oscillator strengths taken from Morton (2003).
trum which ensured a self-consistent description of all lines
SolarphotosphericabundanceforcarbonistakenfromAllende
observedinthez =1.7817system.Thisspectrumisshown
abs
Prieto et al. (2002), for silicon, nitrogen and iron – from
inFig.4bythedashedline,whereastheinitialMFspectrumis
Holweger(2001).
thesolidline.AsseeninFig.4,therestoredspectrumissofter
in the range 2 Ryd < E < 6.5 Ryd but much harder above
4.2. Absorptionsystem atzabs=1.7817 6.5Ryd.ItshowsabreakattheHeIIionizationedgewiththe
amplitudeJ (A)/J (B)≃3correspondingtotheopticaldepth
ν ν
Manyunsaturatedlinesofdifferentionictransitionsalongwith τc(HeII)≃1.Physicalparametersestimatedwiththismodified
asinglesaturatedhydrogenlineLyαaredetectedinthissystem ionizingbackgroundarelistedinTable3,Col.2,andthecorre-
D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption 5
Fig.3. Hydrogenandmetalabsorptionlinesassociatedwiththez =1.7817systemtowardHE0141–3932(normalizedinten-
abs
sities areshownbydotswith1 σ errorbars).Thezeroradialvelocityis fixedatz = 1.7817.Smoothcurvesare thesynthetic
spectraconvolvedwiththecorrespondingpoint-spreadspectrographfunctionandcomputedwiththephysicalparameterslistedin
Table3,Col.2.Boldhorizontallinesmarkpixelsincludedintheoptimizationprocedure.Thesyntheticprofilesofunmarkedab-
sorptionfeatureswerecalculatedinasecondroundusingthevelocityv(x)andgasdensityn (x)distributionsalreadyobtained
H
intheoptimizationprocedure.
spondingsyntheticprofilesareplottedinFig.3bythesmooth The subsystem B has an unsaturated hydrogen line and
curves. henceallowsustoestimatethehydrogencolumndensitywitha
sufficientlyhighaccuracy.The physicalparameterscomputed
with the UV background deduced for the z = 1.7817 sys-
abs
4.3. Absorptionsystem atzabs=1.7103 temaregiveninTable3,Col.4.Theobtainedextremelyhigh
metallicity–almost9Z⊙ –isstriking.SincesiliconlinesSiIII
Thisabsorptionsystemspansthevelocityrangeof500kms−1 λ1206 and SiIV λ1393,1402 are very weak and the element
andislocatedinvelocityspaceatadistanceof9600kms−1 ratios ([Si/C], [N/C]) notknown a priori,the mean ionization
from the QSO. It reveals many lines of differentionic transi- parameterU ≃ 0.04 representsa lower limit consistentwith
0
tions (Fig. 5). The structure of the Lyα, CIV, SiIV and NV theobservedintensitiesoftheCIVlinesandtheabsenceofthe
profilesindicatesthatthesystemmaybedividedintotwosub- CII λ1334 absorption. Formally this subsystem could be fit-
systems: one at –200 km s−1 < v < 180 km s−1 (A) and
anotherat180kms−1 <v <320kms−1 (B).
6 D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption
km s−1< v < −100 km s−1. A single available hydrogen
line does not allow us to conclude whether the blue wing is
blendedorthereisindeedagradientofmetalcontent.Thefor-
mer possibility looks more probablesince there is a non-zero
flux in the Lyα profile at –110 km s−1< v < –90 km s−1
with the mean intensity 0.018±0.005 (marked by the arrow
inFig.5).Theconstantmetallicitythroughoutthissub-system
seemstobeappropriatesinceverysteepbluewingsofseveral
ions (SiIII, SiIV,CIV) do not indicate a progressive dilution.
Thus,thecalculationswerecarriedoutwiththeassumptionof
constantmetallicity.Theneutralhydrogencolumndensityand
theshapeofthebluewingofthesyntheticLyαshowninFig.5
were calculated with the velocityand density fields estimated
fromtheobservedmetallineprofiles(fordetailssee Sect.4.3
in Levshakovetal. 2003a).The obtainedphysicalparameters
aregiveninTable3,Col.3.Wealsotriedotherionizingback-
grounds(differentpowerlawsandtheMFspectrum),butnone
of them was consistent with the observed relative intensities
Fig.4. Spectral shape of a typical AGN ionizing continuum withintheCII/CIVandSiII/SiIII/SiIVprofiles.
from Mathews & Ferland (1987)shown by the solid line and
its modification (dashed line) estimated for the z = 1.7817
abs
system.ThespectraarenormalizedsothatJ (hν =1Ryd)=
ν
Inspiteofalluncertaintiesintrinsictothissubsystemsev-
1.Factorsf aredefinedintheAppendix
i
eralparametersweresteadlyreproducedinallruns.Theseare
(1)slightlyundersolarnitrogenabundance,[N/C]=−0.1±0.1,
(2)significantlylowerratiosofSi/CandAl/Cascomparedto
tedwithanyhigherionizationparameterproducingevenhigher
their solar values,[Si/C] = −0.3±0.1, [Al/C] = −0.3±0.1,
metallicityandhigher[Si/C]and[C/N]ratios.
and (3)extremelyhighoverabundanceof iron[Fe/H] > 1.5.
To confirm the high metallicity in this subsystem we re- ∼
The extremely high overabundance of iron as well as under-
peated calculations assuming other ionizing backgrounds –
abundancesof silicon and aluminium may be caused by non-
power laws with α ranging between 1.0 and 1.8 and the MF
equilibriumionization.Whenanabsorbinggascomestoequi-
spectrum. These trials also delivered metallicity of about 10
libriumthroughcoolingandrecombiningitsionizationparam-
solar.
etercanbeoverstatedduetodifferentcoolingandrecombina-
In principle,such highmetalenrichmentofthecircumnu-
tiontimesoftheobservedionsstemmingfromdensityfluctu-
cleargasispredictedinsomemodelsofchemicalevolutionof
ations(so-called ”hotphotoionization”).A higherdensity gas
QSO/host galaxies (Hamann & Ferland 1999, hereafter HM).
hasshortercoolingandrecombinationtimesandhencecomes
However,anotherexplanationofourresultsisthattheabsorb-
fastertoequilibrium.Thus,thesub-systemAmaybedescribed
inggasisnotinequilibriumwiththeionizingbackground,e.g.,
as consisting of dense gas clumps that are already close to
isstillcoolingandrecombining.Inthiscasehighmetallicities
equilibrium (seen in low ionization absorptions) and ambient
canbecausedbya longerrecombinationtimeof hydrogenas
rarefied gas still far from equilibrium (responsible for most
comparedtoCIVandNV(e.g.,Osterbrock1989).Theioniza-
of CIV and NV absorptions). The equilibrium ionization pa-
tionparameterU and,hence,thetotalhydrogencolumndensity
rametershouldbelower,probablyrangingbetween0.001and
N ∝ 1/Υ (U) is determinedby the observedline intensi-
H HI 0.003.WiththisU ,onlyamildoverabundanceofiron,[Fe/Si]
ties ofdifferentions.Since hydrogenisionizedhigherthan it 0
∼0.2−0.3,wouldbeenoughtodescribetheobservedintensity
would be in the ionization equilibrium with the same param-
oftheFeIIlines.
eterU, thetotalhydrogenbecomesunderestimatedleadingto
anartificiallyhighmetallicity.Wemayexpectthattheadjacent
subsystemA(centeredatv =0kms−1)wouldhelptoclarify
thephysicalconditionsinthezabs=1.7103absorber. Thus, we estimate a metallicity of >∼ 9Z⊙ in the higher
ThesubsystemAshowscomplexprofilesoflowionization ionized subsystem B and ∼ 2Z⊙ in the lower ionized sub-
lines CII, MgII, SiII, and FeII along with AlIII, SiIII, SiIV, systemA(bothmetallicitiesarereferredtosiliconlines).This
NVandsaturatedCIV(seeFig.5).Thecomputationshadbeen strong metallicity difference is another argument in favor of
carriedoutwiththeionizingbackgroundfromthezabs=1.7817 non-equilibrium ionization in sub-system B. It probably has
system.Thepresenceofthesubsequentionictransitionsguar- lowergasdensitythaninAwhichleadstolongercoolingand
anteestheaccuracyofthemeanionizationparameterof∼10% recombinationtimes.Wesuggestthatsometimeagothewhole
(foragivenionizingbackground). absorbingcomplex(A+B)waseitherexposedtoamuchmore
Theassumptionofconstantmetallicityinsidetheabsorber intenseradiationorshock-heateduptothetemperatureswhen
turned out to be inconsistent with the observed blue wing of collisional ionization becomes significant (Klein et al. 1994,
Lyαandtheabsenceofanymetalabsorptionintherange−200 2003;Levshakovetal.,2004).
D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption 7
Fig.5. Same as Fig. 1 but for the z = 1.7103system. The zero radialvelocity is fixed at z = 1.71027.The corresponding
abs
physicalparametersarelistedinTable3,Cols.3,4.ThearrowintheLyαpanelindicatespixelswithnon-zerointensities
4.4. Absorptionsystem atzabs=1.6838 metallicityinsidetheabsorber.Theionizationparametergiven
inTable3forthesubsystemAisdeterminedfromtheobserved
This system separated by ∼ 12450 km s−1 from the QSO intensityofCIVandthenoiselevelattheexpectedpositionof
shows a partially saturated Lyα and many metal lines with theCIIλ1334lineandshouldbeconsideredasalowerlimit.
complex profiles (Fig. 6). SiII λ1260,1193,1190 and NV
λ1242areblendedwithLyαforestabsorptions,andatthepo-
Thealmostsolarratioof[Si/C]=0.06±0.1andastrongun-
sitionofSiIIλ1526aclearcontinuumwindowisseen.
derabundanceofnitrogen[N/C]<−0.5obtainedforbothsub-
The apparent structure of the Lyα profile suggests that systemsindicatethatphotoionizationisprobablyclosetoequi-
this system can be divided into two subsystems: one at – librium.However,slightlyhighermetallicityinthesub-system
250 km s−1< v < –180 km s−1 (A) and another at –180 Aandtheremainingflux0.04±0.01attheshallowbottomof
km s−1< v < 150 km s−1 (B) which were analyzed sep- Lyα may indicate that hydrogenhas not yet reached its equi-
arately. Calculations were carried out using both the ioniz- libriumwiththeionizingbackground(seesub-systemBinthe
ing spectrum restored for the z = 1.7817 system and sev- foregoingsection). Althoughthe absolute valuesof the abun-
abs
eral power law spectra. Physical parameterslisted in Table 3, dancesareuncertain(theydependontheassumedbackground
Cols.5,6correspondtothez =1.7817background.Thered andthemeanionizationparameter),thesolartooversolarcar-
abs
wingofthesyntheticprofileofLyαinthesubsystemBiscal- boncontent,theratio[Si/C]≃ 0andasignificantunderabun-
culated simultaneously with metal lines assuming a constant danceofnitrogenareconstantlyreproducedinalltrials.
8 D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption
Fig.6. Same as Fig. 1 but for the z = 1.6838system. The zero radialvelocity is fixed at z = 1.68377.The corresponding
abs
physicalparametersarelistedinTable3,Cols.5,6
4.5. Absorptionsystems atzabs= 1.7365and The distance between the absorbing cloud and the light
1.4978 source can be estimated from the photoionization model and
thecolumndensityratiosofCII∗/CIIorSiII∗/SiII.Foranion
OthersystemswithunusuallystrongandcomplexCIVprofiles intheinterstellar(intergalactic)medium,theratioofexcitedto
areidentifiedinthespectrumofHE0141–3932.Unfortunately, ground-statepopulationis equal to the ratio of the collisional
they cannot be analyzed by the MCI because their hydrogen excitationrateQ1→2 tothespontaneoustransitionprobability
linesareunavailable,andwedescribethemonlyqualitatively. A2→1 (Bahcall&Wolf1968):
Thesystem atz = 1.7365(separatedby7000kms−1from
abs
the QSO) shows also a clear NV doublet (Lyα profile is n2 = Q1→2 . (1)
blended). The apparent ratio CIV/NV is very much like that n1 A2→1
inthesub-systemAatzabs=1.6838andthezabs=1.7365sys- ThecorrespondingatomicdataforCII∗ andSiII∗ arethefol-
tzeambs=pro1b.4a9b7ly8h(∆asvsi=mil3a0r 0p0h0yskicmalsp−a1ra)meextheirbsi.tsThaestsryosntgemanadt lloiswioinnsg:wAit2h→e1le=ctr2o.n2s91at×T10−=6s1−014,Ktheqeexcit≃atio1n×ra1t0e−b7yccmol3-
kin 1→2
complex SiIV absorption and a weak NV doublet as well as s−1forCII∗,andA2→1 =2.17×10−4s−1,q1e→2 ≃2×10−7
CIIλ1334(Lαisoutofrange),andinthesefeaturesresembles cm3 s−1 for SiII∗ (Silva & Viegas 2002). Since collisions
thesub-systemBatz =1.6838.
abs with other particles have much lower excitation rates, we put
Q1→2 =q1e→2ne.
4.6. Thedistance from the lightsource WedonotdetectSiII∗ orCII∗ linesintheassociatedsys-
tems,thereforeclear‘continuumwindows’attheexpectedpo-
The oversolar metallicity obtained in the absorbers described sitionsofCII∗λ1335.7andSiII∗λ1264.7 wereusedtosetup-
aboveplacetheminaclassofassociatedsystems.Furthermore, perlimitsonthecolumndensitiesofCII∗ andSiII∗ (Table3).
theirextremelylargeradialvelocitiesimplythattheyoriginate Forthe3σupperlimitsonN(SiII∗)andN(CII∗),eq.(1)pro-
ingasejectedfromthecircumnuclearregionoftheQSO/host vides n < 3 cm−3in the z = 1.78, and 1.71 (A) systems,
e abs
galaxy.Thisisalsosupportedbytherelativelystrongemission and n < 15 cm−3in the z = 1.68 (B) system. Since the
e abs
flux in FeII and FeIII lines and at the same time by the FeII degreeofionizationin thesesystemsis high(nH+/nH ≫ 1),
absorptionsin the associated systems. Note that FeII lines in theupperlimitsonthetotalgasdensitynH arethe same,i.e.,
absorberswithN(HI) <∼1016cm−2areextremelyrare;prob- nH < 3cm−3andnH < 15cm−3,respectively(thecontribu-
ablythisisthefirstsuchdetection. tionoftheionizedheliumisignoredsinceithasasmalleffect).
D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption 9
Table 3. Physical parameters of the z = 1.7817, 1.7103 and 1.6838 metal absorbers toward HE 0141–3932 (z = 1.80)
abs em
derivedbytheMCIprocedure(limitsaregivenatthe1σlevel)
z =1.7817 z =1.7103 z =1.6838
abs abs abs
Parameter subsystemA subsystemB subsystemA subsystemB
(1)f (2) (3)d (4)d (5) (6)
U0 3.1E–3a 9.0E–3 3.8E–2 >∼2.8E–2 1.3E–2a
NH,cm−2 4.2E17a 5.7E18 8.6E17 >∼3.2E17 2.5E18
σv,kms−1 20.8a 55.0 21.0 19.2 59.0a
σy 0.63a 0.77 0.62 0.36 0.52a
ZC 3.4E–4a 1.1E–3 2.1E–3 <∼5.2E–4 2.9E–4a
ZN <1.2E–4 3.1E–4 3.2E–4 <∼5.0E–5 2.8E–5b
ZMg 7.0E–5b 1.4E–4 ... ... ...
Z 7.0E–6b 6.2E–6 ... ... ...
Al
ZSi 4.3E–5a 7.4E–5 3.0E–4 <∼8.5E–5 4.8E–5a
ZFe 6.0E–5b ∼8.0E–4 ... ... ...
[ZC] 0.14±0.08 0.65 0.94 <∼0.33 0.08±0.10
[ZN] <0.15 0.56 0.58 <∼ −0.3 −0.48±0.15
[ZMg] 0.30±0.10 0.6 ... ... ...
[Z ] 0.30±0.10 0.3 ... ... ...
Al
[ZSi] 0.09±0.08 0.33 0.94 <∼0.4 0.14±0.10
[ZFe] 0.30±0.15 ∼1.5 ... ... ...
N(HI),cm−2 (2.6±0.5)E15 1.0E16e (2.6±0.5)E14 (1.1±0.2)E14 2.5E15e
N(CII),cm−2 (1.64±0.08)E13 (1.5±0.2)E14 <∼1.0E12 <∼1.6E11 (7.3±1.5)E12
N(CII∗),cm−2 <5.0E11 <4.3E12 ... ... <1.5E12
N(MgII),cm−2 (1.20±0.20)E11 (5.3±1.5)E12 ... ... ...
N(SiII),cm−2 (2.8±0.3)E12 (1.2±0.1)E13 ... ... ...
N(SiII∗),cm−2 <1.3E11 <2.0E11 ... ... ...
N(FeII),cm−2 (1.4±0.4)E11 (5.5±2.0)E11 ... ... ...
N(AlIII),cm−2 (3.6±1.0)E11 (1.4±0.3)E12 ... ... ...
N(SiIII),cm−2 7.5E12c (5.5±0.6)E13 (2.3±1.2)E11 <∼8.5E10 (7.9±0.8)E12
N(CIV),cm−2 (2.2±0.2)E13 (1.7±0.2)E15 (3.4±0.3)E14 (3.4±0.2)E13 (2.3±0.1)E14
N(SiIV),cm−2 (4.5±0.4)E12 (7.7±0.8)E13 (1.6±0.5)E12 <3.0E11 (1.2±0.1)E13
N(NV),cm−2 <1.4E12 (1.8±0.2)E14 (7.7±0.8)E13 (4.5±0.5)E12 (1.3±0.1)E13
hTi,K 0.8E4 1.2E4 1.3E4 1.8E4 1.6E4
a,bUncertainties:a∼15−20%,andb∼30%.
cThevalueofN(SiIII)iscalculatedonbaseofotherlines.
dPhysicalparameters(U0,NH,σv,σyandmetallicities)areonlyillustrativesinceestimatedforthe
photoionizationequilibriumwhereastheabsorptionsystemisinnon-equilibrium.
eEstimatedundertheassumptionofconstantmetallicityinsidetheabsorber.
fZX =NX/NH;[ZX]=log(NX/NH)−log(NX/NH)⊙.
To estimate the distance, the QSO continuum luminosity ergs−1 Hz−1 whichshowsthatbothvaluesare in reasonable
atthe LymanlimitL mustbe known.Absolutespectropho- agreement.In the followingwe use the second one since it is
νc
tometryisnotavailableforHE0141–3932.Thereforeweesti- basedontheobservationaldata.
matedtheintrinsicluminosityL from(i)thecomparisonof Given the upper limits on n , the distance from the QSO
νc H
theQSOBmagnitude(assumingtheQSOspectralenergydis- to the absorbing cloud can be calculated from the estimated
tributionisaMF-type,i.e.,α = 0.5intherange912A˚< λ < ionizationparameterU whichisdefinedas
1600 A˚) with the specific flux of a star having m = 0.0
outside the Earth’s atmosphere (4.4 × 10−20 erg sB−1 cm−2 U = Q(H0) = nph , (2)
Hz−1) and from (ii) the empirical formula given by Tytler 4πr2cnH nH
[1987, Eq.(17)]which is obtained from a fit to (fν,mv) data where
onover60QSOswithawiderangeofredshifts.Theobserved
∞ L
B magnitude of 16.09 (corrected for extinction) translates to Q(H0)= ν dν (3)
thefluxfν(4400A˚)=1.6×10−26ergs−1 cm−2Hz−1 which Zνc hν
in turn leads to the apparentluminosity near the Lyman limit is the number of hydrogen ionizing photons emitted per unit
Lνc ∼ 8 × 1031 erg s−1 Hz−1 (H0 = 71 km s−1 Mpc−1, time by the central source, c is the speed of light, νc is the
Ωm = 0.3,andΩΛ = 0.7areusedtocalculatetheluminosity frequency of the Lyman continuum edge, and nph the corre-
distanceof13Gpc).ThesecondmethodgivesLνc ∼5×1031 spondingdensityofionizingphotons.
10 D.Reimersetal.:HE0141–3932:abrightQSOwithanunusualemissionlinespectrumandassociatedabsorption
With the estimated Lyman continuum luminosity L ∼ lessthan7×1031ergs−1Hz−1.Thisimplieseitheranunusu-
νc
5×1031ergs−1Hz−1, onefindsQ(H0)∼7.5×1057photons allyflatradiationcontinuum(typicallyforQSOsisL ∝ν−0.5
ν
s−1, assuming L = L (ν/ν )−α, and α = 1 in the range at ν < 1013 Hz and∝ ν−1.5 above),orthatthe apparentop-
ν νc c
ν > ν .Asubstitutionofthenumericalvaluesin(2)provides ticalluminosityisDoppler-boosteddueto the relativisticmo-
c
r >100kpc,r >280kpc,andr >450kpc. tion of the light source. Another argument in favor of boost-
1.68 1.71 1.78
ingcomesfromthemetallicityestimations.HE0141–3932isa
brightsource.ItissupposedthattheQSOluminosityisdeter-
5. Discussionandconclusions
mined by the accretion rate which requiresa large amountof
Thecharacteristicsofboththebroademissionlinesandasso- circumnucleargas.This,inturn,supposesa largemassofthe
ciatedabsorptionsofHE0141–3932canbebestexplainedby contributingstellarpopulationand,hence,ahighmetalenrich-
thealmostpole-onviewofthisquasar.Theweaknessofemis- mentofthe accretinggas.For reference,allQSOs with lumi-
sion lines is then due to dilution by direct radiation from the nositiesabove5×1031ergs−1Hz−1inthesampleofDietrich
accretiondisk,whereasthevelocityshiftsoftheassociatedsys- etal.(2003)havemetallicitiesZ > 3Z⊙ withthemeanvalue
temsandtheirdistancesfromthelightsourcecanbecausedby of 4-5Z⊙. The metallicity of 4-5Z⊙ has been also measured
the entrainment into the large-scale outflowing jet. However, intheassociatedsystemofaverybrightQSOHE0515–4414
powerfuljetspropagatingtodistancesof∼0.5Mpcimplythe (Levshakov et al. 2003b). Gas in HE 0141–3932 has metal-
existence of significant radio radiation, but HE 0141–3932is licity Z ≈ 1−2Z⊙, which supposes a relatively low stellar
a radio-quiet QSO. An upper limit to its radio flux of 1 mJy populationinvolvedintheenrichment,lowaccretionrateand,
translates into the intrinsic radio luminosity L < 7 × 1031 hence,lowluminosity.Boostingcanbecausedbyarelativistic
ν
ergs−1 Hz−1. Thisis a radio powerofa typicalFR I source. jetseenatasmallviewingangle.Takingintoaccountthemea-
Jets in the FR I-type structures are known to be subsonic or suredequivalentwidthsoftheemissionlines,wemayassume
slightlyoversonicwithvelocities1000–10000kms−1,heav- thattheluminosityisamplifiedby∼10times,i.e.theintrinsic
ier than and isobaric with the external medium (e.g., Hughes luminosity of HE 0141–3932mightbe only L ∼ 5×1030
νc
1991).Thesecharacteristicsareinlinewiththesuggestionthat ergs−1 Hz−1.
theobservedabsorptionsoriginateintheentrainedclouds.Itis Anotherissueofinterestistherelativeabundancesobtained
alsoknownthatFRIjetsdonotshowanextendedradioemis- for the absorbinggas. The analyzedabsorptionsystems show
sion.Thismeansthatradioobservationsofsuchjets,especially high iron content, [Fe/C] = 0.15±0.1, [Fe/Mg] = 0.0±0.1
whentheyareseenatasmallangletothelineofsight,needa (z = 1.78),butatthe same time nitrogenis stronglyunder-
abs
high spatial resolution and high sensitivity. Nevertheless, the abundant,[N/C] < −0.5(z =1.68).Althoughthesevalues
∼ abs
calculated distances of several hundreds of kiloparsecs seem were estimated in different absorption systems they are rep-
tobe4-5timeoverestimatedsincethetypicaljetlengthofthe resentative for the bulk of circumnuclear gas for the follow-
FRIobjectisbelow100kpc.Wecannotexplainthesourceof ing reason. The mass of the stellar populationinvolvedin the
thisdiscrepancy.Itshouldbenoted,however,thatdistancesof enrichment of a quasar’s circumnuclear region is > 104M⊙
hundredsofkiloparsecsfortheassociatedsystemsarenotex- (Baldwin et al. 2003a) and hence large metallicity gradients
ceptional[see,e.g.,Morrisetal. (1986);Tripp,Lu,& Savage andsharpdiscontinuitiesduetoenrichmentbyonlyafewstars
(1996);D’Odoricoetal.(2004)]. are unlikely. In the Hamann & Ferland (1993, 1999) models
The second fact that is hard to explain is the large veloc- of QSO chemical evolution, solar metallicity is reached after
ity excess between low- and high-ionization emission lines. > 0.2Gyrandischaracterizedbyarelativeoverabundanceof
∼
According to a model of the quasar atmosphere (e.g., Elvis nitrogen,[N/C] > 0, and an underabundanceof iron, [Fe/C]
∼
2004), low-ionization emission lines (Hα, OI, FeII, MgII, <0.Duetothedelayof1GyrinFeenrichmentexpectedfrom
CIII])comefromtheouterregionoftheaccretiondiskwhich the longerevolutionof SNe Ia which are the main sourcesof
iswellshieldedfromthecentralsourceradiationandoptically iron, the emission line ratios FeII/CIV and FeII/MgII were
thick for Lyα. Lyα and high-ionization emission lines (CIV, proposed as a clock to constrain the QSO ages. However, in
SiIV,NV)areformedinacoolphaseofthewindarisingfrom thesemodels,largevaluesof[Fe/C]and[Fe/Mg]arealwaysas-
the inner parts of the accretion disk. The emission at 3400 A˚ sociatedwithaconsiderableoverabundanceofnitrogen,[N/C]
observed in HE 0141–3932 cannot be interpreted unambigu- > 0.3. We do not observe such behavior in our systems and,
ously,butifitis(evenpartially)duetoLyαatz = 1.80,then hence,cannotconfirmthis‘ironclock’.Thisisinlinewiththe
itsredshiftandstrengthisinconsistentwiththisscenariosince resultofMatteucci&Recchi(2001),whoshowedthatthetime
CIV and SiIV are seen at z = 1.75. The same situation (i.e., scaleforenrichmentbySNeIaisnotuniquebutastrongfunc-
z >z )isobservedinPG1407+265.Apparently,acom- tion of the adopted stellar lifetimes, initial mass function and
Lyα CIV
plex geometrical model of the broad emission line region is starformationrateandcanvarybymorethananorderofmag-
necessarytoexplaintheobservations. nitude.
As already mentioned, the relativistic jet beamed toward
Acknowledgements. TheworkofS.A.L.andI.I.A.issupportedbythe
us was discovered in the bright (B = 15.7) and radio-quiet
RFBR grant No. 03-02-17522 and by the RLSS grant 1115.2003.2.
PG 1407+265 (Blundell et al. 2003). There are indications
C.F. is supported by the Verbundforschung of the BMBF/DLR
that HE 0141–3932may also have a similar small-scale rela- grant No. 50 OR 9911 1. S.L. acknowledges support from the
tivistic jet. The Lyman limit luminosity of HE 0141–3932 is Chilean CentrodeAstrof´ısicaFONDAP No. 15010003, and from
Lνc = 5×1031ergs−1 Hz−1,whereasitsradioluminosityis FONDECYTgrantNo1030491.