Evidence for Relativistic Disk Reflection in the Seyfert 1h Galaxy/ULIRG IRAS 05189-2524 Observed by NuSTAR and XMM-Newton

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by  Yanjun Xu

Draftversion February2,2017
PreprinttypesetusingLATEXstyleemulateapjv.5/2/11
EVIDENCE FOR RELATIVISTIC DISK REFLECTION IN THE SEYFERT 1H GALAXY/ULIRG
IRAS05189–2524OBSERVED BY NUSTAR AND XMM-NEWTON
Yanjun Xu1, Mislav Balokovic´1, Dominic J. Walton1,2,3, Fiona A. Harrison1, Javier A. Garc´ıa1,4,5,8, Michael J.
Koss6,7,9
Draft versionFebruary 2, 2017
ABSTRACT
7
1 We present a spectral analysis of the NuSTAR and XMM-Newton observations of the Seyfert 1h
0 galaxy/ULIRGIRAS05189–2524takenin2013. We findevidenceforrelativisticdiskreflectioninthe
2 broadbandX-rayspectrum: a highly asymmetric broadFe Kα emissionline extending downto 3keV
and a Compton scattering component above 10keV. Physical modeling with a self-consistent disk
n
reflectionmodelsuggeststhe accretiondisk is viewedatanintermediate anglewitha super-solariron
a
abundance, and a mild constraint can be put on the high-energy cutoff of the power-law continuum.
J
We test the disk reflection modeling under different absorption scenarios. A rapid black hole (BH)
1
spinisfavored,howeverwecannotplaceamodel-independenttightconstraintonthevalue. Thehigh
3
reflection fraction (R ≃ 2.0–3.2) suggests the coronal illuminating source is compact and close to
ref
the BH (lying within 8.7 R above the central BH), where light-bending effects are important.
] g
E Subject headings: accretion, accretion disks − black hole physics − galaxies: active − galaxies: indi-
H vidual (IRAS05189–2524)− galaxies: Seyfert − X-rays: galaxies
.
h
p 1. INTRODUCTION AGNs(e.g.Tanakaetal.1995;Nandraetal.2007;Risal-
-
iti et al. 2013; Walton et al. 2013); these are mostly
o The hard X-ray continuum emission of active galactic
r nuclei (AGNs) is believed to be produced in the corona Seyfert1–1.5 galaxies with only a few absorbed Seyfert
t 2 galaxies showing such features: e.g., IRAS 18325–
s via thermal Comptonization of ultraviolet (UV) radia-
a tion from the accretion disk (e.g., Haardt & Maraschi 5926 (Iwasawa et al. 1996), IRAS 00521–7054 (Tan et
[ al. 2012). XMM-Newton and Suzaku observations of
1993). This continuum emission is subsequently repro-
1 cessed by dense material either from the accretion disk IRAS00521–7054 revealed a possibly strong and broad
Fe Kα line favoring a high BH spin, however the broad
v ordistantstructuressuchasthedustytorusorthebroad
line could also be artificially produced by a combina-
3 line region(BLR), producing the characteristicreflected
tion of partial covering absorbers (Tan et al. 2012; Ricci
7 X-ray spectrum (e.g., George & Fabian 1991). Fluores-
et al. 2014). With high-quality broadband X-ray data
0 cent spectral lines, line edges and a Compton hump are
and multi-epoch observations, BH spins have been ro-
0 typicalfeaturesofthereflectedX-rayspectrum. FeKαis
bustly constrained in some nearby obscured Seyferts
0 the most prominent spectral line in the X-ray band due
. to its high cosmic abundance and fluorescent yield. The (e.g., Seyfert 1.9 galaxy NGC 1365, Risaliti et al. 2013;
2 Waltonetal.2014),butthemeasurementisstilldifficult
lineemissionfromthe innermostregionsoftheaccretion
0
for these obscured objects.
7 disk is relativisticallybroadenedby the combinedeffects
IRAS05189–2524 is an ultraluminous infrared galaxy
1 of Doppler shifts and gravitational redshift (Fabian et
: al. 1989; Laor 1991), which skew the line profile into an (ULIRG) with log(LIR/L⊙) = 12.16 (U et al. 2012)
v and hosts a Compton-thin AGN at redshift z = 0.0426.
extendedredwing. Assumingthe accretiondiskextends
i While originally classified as Seyfert 2 (Veilleux et
X down to the innermost stable orbit (ISCO), which is de-
al. 1995), broad polarized Balmer lines were detected
termined by the spin of the black hole (BH), a relativis-
r (Young et al. 1996) and near-infrared spectroscopy re-
a tically broadenedFe Kα line couldbe usedas aprobe of
vealed broad Paschen lines (Veilleux et al. 1999b; Sev-
the BH spin.
ergnini et al. 2001), indicating the existence of a hid-
So far, broad Fe Kα lines have been detected in many
den BLR. Therefore, it has been more accurately classi-
fied as a hidden broad line Seyfert 1 galaxy (Seyfert 1h
1Cahill Center for Astronomy and Astrophysics, California galaxy/S1h)(V´eron-Cetty& V´eron2006),whichdefines
Institute ofTechnology, Pasadena, CA91125, USA
2Jet Propulsion Laboratory, California Institute of Technol- the kind of Seyfert 2s having the spectra ofSeyfert 1s in
ogy,Pasadena, CA91109, USA the polarized light.
3InstituteofAstronomy,UniversityofCambridge,Madingley In the X-ray band, IRAS05189–2524 is one of the
Road,CambridgeCB30HA,UK
most luminous ULIRGs in the sky, which are typically
4Harvard-Smithsonian Center for Astrophysics, 60 Garden
St.,Cambridge,MA02138USA mergersystemsundergoingrapidstar-formingactivities.
5Remeis Observatory & ECAP, Universit¨at Erlangen- IRAS05189–2524is likelya late stagemergeroftwospi-
Nu¨rnberg,Sternwartstr.7,96049Bamberg,Germany ral galaxies (Sanders et al. 1988). Its X-ray emission is
6Institute for Astronomy, Department of Physics, ETH
dominatedbythe centralAGNratherthanstarburstac-
Zurich,Wolfgang-Pauli-Strasse27,CH-8093Zurich,Switzerland
7Institute for Astronomy, University of Hawaii, 2680 Wood- tivities (Veilleux et al. 1999b). Iron emission has been
lawnDrive,Honolulu,HI96822, USA detected in IRAS05189–2524 from previous X-ray ob-
8AlexandervonHumboldtFellow. servations by Beppo-SAX (Severgnini et al. 2001) and
9SNSFAmbizioneFellow.
2 Xu et al.
Suzaku (Teng et al. 2009), but the general line profile
wasnotresolved. Thesourcewentthroughamajorspec- TABLE 1
XSPECModels
tralchangeduringthe2006Suzakuobservationwhenthe
2–10 keV flux dropped by a factor of ∼30, which could
Model XSPECComponents Spectral Range
be explained by an increase in the absorption column
density or the change of the intrinsic AGN luminosity 1 zpcfabs*powerlaw +mekal 0.3–30keV
(Tengetal.2009). Atagalacticscale,high-velocityout- 2 zpcfabs*(pexrav +zgauss)+mekal 0.3–30keV
flows of ionized (Westmoquette et al. 2012; Bellocchi et 3a zpcfabs*relxilllp 2–30keV
al. 2013), neutral (Rupke et al. 2005; Teng et al. 2013; 3b (partcov*tbnew feo)*relxilllp 2–30keV
Rupke & Veilleux 2015) and molecular (Veilleux et al. 4a zpcfabs*XSTAR*relxilllp 2–30keV
2013) gas have been observed. 4b (partcov*tbnew feo)*XSTAR*relxilllp 2–30keV
Outflows have been recognized as a signature of AGN
feedback, which is believed to play an important role in NuSTARdatashowminorcountratevariability(∼20%)
the co-evolution of AGNs and their host galaxies. Evi- andnoobviouschangeinspectralshapebetweenthetwo
dence for multi-phase outflowing gas has been observed epochs. Therefore, we combined the three NuSTAR ob-
in AGNs on a wide rage of spatial scales from that of servations using the ADDSPEC script in HEASoft v6.19
the central accretion disk to large-scale molecular out- to maximize the signal-to-noise ratio (S/N) of the spec-
flows. If outflows at different scales are all AGN-driven, tra. We binned the data taking into account the back-
linking them could help unveil the expansion mecha- ground level to provide a nearly constant S/N over the
nism of the wind, such studies have been conducted on NuSTAR bandpass, with a minimum S/N of 3, and me-
ULIRGs IRAS11119+3257 (Tombesi et al. 2015) and dianS/Ns of5.5and5.3for the twofocalplane modules
Mrk231(Feruglioetal.2015). IntheX-rayband,thereis (FPMA and FPMB).
growingevidenceforultra-fastoutflows(UFOs)withthe
typical velocities of ∼0.1–0.2c, detected by fitting blue- 2.2. XMM-Newton
shiftedFe K-shell absorption lines between 7 and 10keV
The XMM-Newton observation was reduced with the
(e.g., Pounds et al. 2003;Tombesi et al. 2010;Pounds &
XMM-Newton Science Analysis System v14.0.0 follow-
King 2013). In the case of PDS 456, a P-Cygni-like pro-
ing standard procedures. The raw event files were fil-
file was observed, demonstrating a powerful wide angle
teredusingEPCHAINandEMCHAINtoproducecleaned
outflow (Nardini et al. 2015).
event lists for each of the EPIC-pn (Stru¨der et al. 2001)
In this paper, we report evidence for relativistic disk
and EPIC-MOS (Turner et al. 2001) detectors, respec-
reflection in IRAS05189–2524 based on analysis of the
tively. ScienceproductswerethenproducedusingXMM-
broadband X-ray spectrum from NuSTAR and XMM-
SELECT, considering only single and double events for
Newton. In Section 2, we describe the observations and
EPIC-pn,andsingletoquadrupleeventsforEPIC-MOS.
the data reduction. Section 3 provides the details of our
We extracted the source from a circular region of radius
spectralfitting. We presenta discussionofthe results in
40′′, while background was estimated from a large re-
Section 4 and summarize our results in Section 5.
gion of blank sky on the same detector as IRAS05189–
2. DATAREDUCTION 2524. Instrumental response files were generated with
RMFGEN and ARFGEN for eachdetector. The goodex-
IRAS05189–2524was observed with NuSTAR (Harri-
posure is ∼31ks for EPIC-pn and ∼36ks for each of the
son et al. 2013) and XMM-Newton (Jansen et al. 2001)
two EPIC-MOS detectors. After performing the reduc-
in 2013 as a part of the NuSTAR ULIRG survey (Teng
tionseparatelyforMOS1andMOS2,wecombinedthese
et al. 2015) and the NuSTAR survey of Swift/BAT
data into a single spectrum using ADDASCASPEC. The
AGN (Balokovi´c et al., in prep.). NuSTAR observed
MOS and PN spectra were grouped to have 25 counts
the source at two epochs: on 2013 February 20 (OBSID
per bin.
60002027002) and on 2013 October 2 (consecutive OB-
SIDs 60002027004and 60002027005)with the exposures 3. SPECTRALANALYSIS
of 23.1ks, 25.4ks and 8.3ks, respectively. The XMM-
Newton observation (OBSID 0722610101) with an ex- We model the time-averaged NuSTAR and XMM-
posure time of 37.8ks was coordinated with the second NewtonspectrajointlyinXSPECv12.9.0(Arnaud1996)
NuSTAR observation. The dataset was previously anal- using the χ2 statistics. All uncertainties of the spec-
ysed in the NuSTAR ULIRG survey (Teng et al. 2015), tralparametersarereportedatthe90%confidencelevel.
with the focus on uncovering the obscuration levels and Cross-normalizationconstants are allowed to vary freely
intrinsic luminosities of several nearby ULIRGs. We re- for NuSTAR FPMB and XMM-Newton MOS and PN,
ducedthe data followingthe data processingdescription and assumed to be unity for FPMA. The values are
in Teng et al. (2015). within ∼10% of unity, as expected from Madsen et al.
(2015). For all the spectral fitting, we take into account
2.1. NuSTAR the Galacticabsorptionby modifying the spectrumwith
The NuSTAR data were processed using v.1.6.0 a TBabs absorption model (Wilms et al. 2000). The
of the NuSTARDAS pipeline with NuSTAR CALDB Galactic column density is set to NH,gal = 1.66×1020
v20160731. Foreachobservation,thesourcespectrawere cm−2 (Kalberla et al. 2005).
extractedat the position ofIRAS05189–2524within the WebeginourspectralanalysisofthebroadbandX-ray
radius of 60′′. Corresponding background spectra were spectrumconsideringthebandfrom0.3keVto30keV,as
extracted from source-free areas on the same chip using itbecomesbackground-dominatedabove30keV.Wefirst
polygonalregions. AsdiscussedinTengetal.(2015),the fit the spectrum with a power-law model subject to one
IRAS05189–2524 3
(a) TABLE 2
SpectralFitting of IRAS05189–2524: Part I
-1V) Component Parameter Model1 Model2
e 1x10-3
-1s k zpcfabs NH (×1022 cm−2) 8.82+−00..2276 8.30±0.21
-2m fabs(%) 98.89+−00..0089 99⋆
c
ns power-law Γ 2.29±0.04 ···
o
hot mekal kT(keV) 0.092+−00..001005 0.087+−00..000069
P
2V ( 1x10-4 pexrav Γ ··· 2.47±0.04
ke Rref ··· 1.48+−00..5434
zgauss LineE(keV) ··· 6.40⋆
2.0 σ (keV) ··· 0.71+−00..1131
(b) model 1
1.6 χ2/d.o.f 1425.8/1049 1194.8/1047
o
Rati 1.2 truNmotfero.m—NuMSoTdAeRl1aannddXmMoMde-lN2ewfittotnhe.0P.a3r–a3m0keteeVrsbwroitahdb⋆aanrdesfipxeecd-
values.
0.8
2.0 disk reflection (Figure 1, panel b): a broad iron line
(c) model 2 peaking around 6.7keV in the source rest-frame with a
1.6 skewed shape extending down to ∼3keV and residuals
o
Rati 1.2 athbeorveea1r0ekpeoVssifbrloemabtshoerpCtoiomnpfteoanturreeflseocftbiolune.-sInhifatdeddiFtieonK,

lines in both the NuSTAR and the XMM-Newton spec-
0.8
tra, with the most evident absorption troughs lying in
1 10 the vicinity of the FeK-edge around 7.3keV (Figure 2).
Energy (keV)
3.1. Phenomenological Reflection Model
Fig.1.— (a) XMM-Newton PN (green), MOS (blue), NuS-
TARFPMA(red)andFPMB(black)spectraofIRAS05189–2524, We then test fitting the reflection features with a phe-
withthebest-fitphenomenologicalreflectionmodel(model2). (b) nomenologicalmodelbyaddinganeutralreflectioncom-
Data/model ratio after fitting an absorbed power-law plus a soft
mekalcomponenttothe0.3–30keVspectrum(model1). (c)Resid- ponent pexrav (Magdziarz & Zdziarski 1995) and one
uals of the phenomenal reflection model (model 2). The data are Gaussian emission line with variable width using the
rebinnedfordisplayclarity. model zgauss(model 2, see table 1). We freeze the cen-
troid of the Gaussian emission line at 6.4keV, the disk
2.5 inclinationangle at the default value (cosi = 0.45), the
iron abundance at solar and include no high-energy cut-
2.0
off (foldE = 0), as this simple model is not sensitive to
Ratio 1.5 t∆hχes2e/∆padr.aom.fe=ter−s.23T1h/e−fit2.isAimbprrooavdedGcaounsssiidaenralbinlye wwiitthh
1.0 linewidthσ =0.71+−00..1131keVandequivalentwidth(EW)
≃0.60keVisrequiredtoprovideadecentfitforthe iron
0.5 line emission feature in the spectrum. However, a clear
5 10 5 10 excess still remains in the residuals between 3 and 6keV
Energy (keV) Energy (keV) as would be expected from the red wing of a relativis-
Fig.2.— Possible absorption features between 7keV and 8keV tically broadened iron line (Figure 1, panel c). Model
markedbyarrowsintheresidualplots ofthe absorbedpower-law 2 also gives a very steep power-law of Γ = 2.47±0.04.
model (model 1). Left panel: XMM-Newton PN spectrum; right
panel: NuSTAR FPMBspectrum. We do not attempt to interpret the intrinsic continuum
steepnessatthispoint,asthisisonlyaphenomenological
partialcoveringneutralabsorbermodeledwithzpcfabs, model.
plusamekallineemissionmodelwithitselementalabun- We note that for both the simple absorbed power-
dancesfixedatsolarvalues(model1,XSPECmodelsare law and the phenomenological reflection model, at least
listedinTable1). Themekalcomponentisusedtomodel two extra emission features are present in the residuals
the thermal plasma contribution from the host galaxy. around0.9 and 1.9keV. The 0.9keV excess might be as-
We find the best fit (reduced chi-square χ2/d.o.f. = sociatedwithOLyαorFe–Lshellemissions,andthefea-
1425.8/1049) with a photon index Γ = 2.29±0.04 and ture around 1.9keV could be caused by ionized Si emis-
a mekal temperature kT = 0.092+0.010keV. The cover- sionlines. Theexcessescannotbeadequatelyfittedwith
−0.005
ingfractionoftheneutralabsorberiswellconstrainedas simple Gaussian emission line models, as they could be
98.89%,thereforecontributionfromthescatteredpower- a complicated combination of ionized absorption, over-
lawcomponentisnegligibleabove∼2keV.Forsimplicity, abundant metal lines and X-ray contribution from the
we fix the value at 99% from here on. high mass X-ray binary population in the star-forming
The data/model ratio plot shows strong signatures of regions. X-ray point-source emission correlates with
4 Xu et al.
galaxy star forming rate (SFR) in star-forming galaxies
(Lehmeretal.2010). AtanSFRof∼80M⊙ yr−1(West- -1V) (a)
e
moquette et al.2012),the 2–10keVluminosity from the k
binary population is estimated to be 1.4×1041ergss−1, -2-1m s 1x10-3
about 1% of the total luminosity, which is enough to c
dominate the soft emission of IRAS05189–2524. There- ns
o
fore, the soft part of the spectrum likely helps little to ot
h
P
constrain the X-ray continuum from the AGN. In order 2V (
to avoid the possible situation where the soft emission e
k 1x10-4
from the host galaxy is driving our modeling of the disk
2.0
reflection features, we ignore the data below 2 keV from (b) model 3a
here on. o 1.5
ati
R
1.0
3.2. Self-consistent Disk Reflection Models
0.5
In Teng et al. (2015), the authors attempted to ex- 2.0
(c) model 3b
plain the reflection features observed in IRAS05189–
o 1.5
2524 by neutral reflection from the torus, which is com- ati
R
monlythecaseforCompton-thickAGNs. However,they 1.0
foundneithertheMYTorus(Murphy&Yaqoob2009)nor
0.5
BNTorus model (Brightman & Nandra 2011) could pro- 2.0
(d) model 4a
vide an adequate fit for the broadband spectrum, which
ruledoutthe possibility ofdistantreflection. Inorderto atio 1.5
explore the relativistic reflection hypothesis, we replace R 1.0
the pexrav and zgauss components in the phenomeno-
0.5
logical model with the self-consistent relativistic reflec-
2.0
tion model relxill (Dauser et al. 2014; Garc´ıa et al. (e) model 4b
2014) (model 3a, see Table 1). We use relxilllp in atio 1.5
the relxill model family, instead of using an empiri- R
1.0
calemissivitylaw,theemissivityiscalculateddirectlyin
thelamppostgeometry(Dauseretal.2013). Relxilllp 0.5
3 5 10 30
calculatesaself-consistentreflectionfraction. Thiscould
Energy (keV)
help us constrain the BH spin by shrinking the parame-
ter space, as results with unphysicalsolutions of low BH Fig.3.—(a)XMM-NewtonandNuSTARspectraofIRAS05189–
2524 with the relativistic disk reflection model 4b. (b)–(e)
spins with high reflection fractions can be ruled out by
Data/model ratio plots after fitting for the disk reflection com-
the assumption of a lamp-post geometry (for discussion, ponent under four different absorption scenarios: (b) one neutral
see Dauser et al. 2014). In order to measure the BH absorberwithasolarironabundance;(c)oneneutralabsorberwith
spin, we assume the inner disk radius extends down to a variable iron abundance; (b) one neutral absorber with a solar
iron abundance + one ionized absorber; (c) one neutral absorber
the ISCO.We fix the outerradiusatthe defaultvalueof
withavariableironabundance +one ionizedabsorber. Thedata
400Rg (Rg ≡ GM/c2 is the gravitational radius) as the arerebinnedfordisplayclarity. SeeTable1forthelistofXSPEC
model is not sensitive to this parameter, and the cutoff models.
energy is allowed to vary in the fitting.
ionization parameter10 log ξ= 3.02± 0.02 erg cm s−1
Therelxilllpmodelyieldsagoodfittothe2–30keV
spectrum with χ2/d.o.f.= 862.0/859 and no obvious ex- for the accretion disk. We note that the iron abundance
A is unusually high with best-fit value hitting the up-
cess in the residuals (Figure 3, panel b). The intrinsic Fe
per bound of the model of 10. But if we fix the iron
X-raycontinuumissteep,withthepower-lawphotonin-
dexΓ=2.04+0.02. Itis inthe upperrangeofthephoton abundance at solar in the relxilllp model, the fitting
−0.03 degrades considerably (∆χ2 ∼130)with a visible excess
indexdistributionobservedinlocalSeyfertgalaxies(e.g.
in the Fe K band.
Nandra & Pounds 1996; Winter et al. 2009; Rivers et
A super-solar metal abundance is not uncommon
al.2013),butlessextremethanthepreviouslypublished
among ULIRGs (e.g., Rupke et al. 2008). In the case of
values for IRAS05189–2524: e.g, Γ = 2.68−+00..3103 (Teng IRAS05189–2524,basedonthediagnosticsof[NII]/Hα,
et al. 2009), Γ = 2.51 ± 0.02 (Teng et al. 2015). Al- [SII]/Hα and[O I]/Hα line ratios,anuncommonly high
beit lacking high quality data above 30keV, the model metallicity (>4Z⊙)11 is estimated for the outer galactic
is able to put a modest constraint on the high-energy disk, or else some peculiar ionization effects are needed
cutoff Ecut = 55+−170keV, as discussed in Garc´ıa et al. toexplainthelineratiomeasurements(Westmoquetteet
(2015a),suchsensitivity could come partly from the low al.2012). Ifthemetallicityisindeedhighonthegalactic
energy part of the reflection spectrum (< 3keV). The scale in IRAS05189–2524, it is more physically consis-
location of the primary radiation source is found to be tent to use neutral absorption models with super-solar
close to the disk h=2.39+0.80R , with a rapid BH spin
(dimensionless spin param−e0.t3e2r ag= 0.96+0.02), and the 10 Theionizationparameterξ=4πFx/n,whereFx istheioniz-
−0.03 ingfluxandnisthegasdensity.
self-consistent reflection fraction derived by the model 11 Only an upper limit was put on the metallicity because the
is high (Rref = 3.24). The best-fit results also find an lineratioswereoutsidetherangepredictedbythephotoionization,
intermediate inclination of θ = 42± 2 degrees and an shockorAGNmodelsusedinthepaper.
IRAS05189–2524 5
TABLE 3
SpectralFitting of IRAS05189–2524: PartII Self-consistentDisk Reflection Models
Component Parameter Model3a Model3b Model4a Model4b
zpcfabs NH (×1022 cm−2) 7.17+−00..1176 4.20+−00..2217 7.15+−00..6523 4.33+−00..9383
fabs(%) 99⋆ 99⋆ 99⋆ 99⋆
AFe ··· 5.5+−21..51 ··· 5.0+−u0.7
xstar NH (×1022 cm−2) ··· ··· 0.27+−00..3277 1.44+−11..5464
logξ (ergcms−1) ··· ··· 3.20+−10..2668 3.17+−00..2389
Vout (c) ··· ··· 0.13+−00..0026 0.12+−00..0021
AFe ··· ··· 10.0+−u3.3 5.0+−u0.7
relxilllp h(GM/c2) 2.39+−00..8302 4.70+−41..0949 3.00+−10..4887 4.08+−21..1660
a(cJ/GM2) 0.96+−00..0023 0.96+−u0.94 0.96+−u0.07 0.98+−u0.61
θ (◦) 42±2 44+−25 41+−52 51+−45
Γ 2.04+−00..0023 1.79+−00..1174 2.00+−00..1179 1.74+−00..1187
logξ (ergcms−1) 3.02±0.02 3.12+−00..2121 3.06±0.07 3.23+−00..1148
AFe 10.0+−u1.3 5.5+−21..51 10.0+−u3.3 5.0+−u0.7
Ecut (keV) 55+−170 34+−2110 59+−12141 33+−2110
χ2/d.o.f 862.0/859 860.6/859 854.8/856 854.7/856
Note. — Model 3–4 fit the broadband spectrum with the part below 2.0keV ignored. Parameterswith ⋆ are fixed values. Iron abundances
(AFe)arelinkedduringthespectralfitting. Valueswithuncertaintymarkedwith+udenote90%confidencelimitsinexcessoftheupperboundof
themodel.
abundances in our spectral fitting, as neutral absorbers outflows in the host galaxy (e.g., Westmoquette et al.
normally reside far from the central BH. 2012; Bellocchi et al. 2013; Rupke & Veilleux 2015), we
In an attempt to further constrain the iron abun- addanionizedabsorptioncomponenttoaccountfor any
dance, we tie the iron abundances of the neutral ab- outflowing ionized absorbers. We modify the spectrum
sorber and the disk reflection component by replacing withanionizedabsorptiontablemodelcalculatedbythe
the zpcfabs model with an improved model for neutral XSTAR code (Kallman & Bautista 2001)and tie its iron
absorption tbnew feo12 convolved with the partial cov- abundance with that of the relxilllpcomponent. It is
ering model partcov (model 3b, see Table 1). Both aphysicallyreasonablerequirement,sinceifthewindhas
Fe and O abundances are variable parameters in the extreme velocity, it most likely arises from the accretion
tbnew feo model. We freeze the O abundance at so- disk, thus the same chemical abundances would natu-
lar, since it would not have a significant influence on rally be expected. We first assume the partial covering
our spectral fitting above 2keV. As a result, the model neutral absorber has a solar iron abundance (model 4a,
finds a best-fit iron abundance A = 5.5+2.5, which is see Table 1). The fitting results reveal an ionized ab-
Fe −1.1
consistent with the measurement from Westmoquette et sorber with a velocity v = 0.13+0.02c in the source
out −0.06
al. 2012. This model provides a slightly better fit for rest-frame, which is well above the typical outflowing
the data (χ2/d.o.f.= 860.6/859), with a higher coronal velocities of warm absorbers, about the common value
height h = 4.70+4.04, a less steep power-law continuum found for UFOs (e.g., Tombesi et al. 2010). With an
−1.99
(Γ = 1.79+0.17) and a cutoff at 34+21keV, even lower ionization parameter log ξ = 3.06 ± 0.07 erg cm s−1,
than in th−e0.p14revious model. As a−1r0esult, the reflec- the absorption should be dominated by Fe XXV. How-
tion fraction is reduced to R = 1.99. We note here ever the detection of a high-velocity ionized outflow is
ref
the cutoff energy is uncommonly low for an AGN, even not significant, as it only brings marginal improvement
compared with the lowest NuSTAR measurements (e.g., to the fitting ∆χ2/∆d.o.f = −7.2/−3 and the differ-
Ursini et al. 2015; Tortosa et al. 2016). This model gen- encenotvisuallyevidentinthe ratioplot. Otherbest-fit
erally has more uncertainty in the parameters,most no- parameters are consistent with model 3a (without the
tably,placesnoconstraintontheBHspin. Althoughthe ionized absorber). A rapidly spinning BH with a>0.89
metallicitiesinthe wholegalaxyshouldbe related,there is required to provide an adequate fit for the data.
is no solid justification to assume the metallicities are Wethenreintroducetheneutralabsorptionmodelwith
the same in the BH vicinity and in the outer disk of the a variable iron abundance (model 4b, see Table 1), and
galaxy. However,we believe itis a reasonablesimplifica- force the iron abundances of the disk reflection, the out-
tion giventhe data quality, untying the ironabundances flowing wind and the neutral absorber to be the same.
brings no obvious improvement to the fitting. The model brings no further improvement for the fit-
Given the possible ionized absorption features in the ting. But again, it reduces the iron abundance AFe to
Fe K band and motivated by the presence of large-scale ∼5, and since the iron abundance and the column den-
sityinthe XSTARmodelaredegenerateparameters,the
12http://pulsar.sternwarte.uni-erlangen.de/wilms/research/tbabs/ column density of the ionized outflow is estimated to be
6 Xu et al.
20
2.0 (a) absorption-dominated: single-absorber model
model 3a: zpcfabs*relxilllp
model 3b: (partcov*tbnew_feo)*relxilllp o 1.5
model 4a: zpcfabs*xstar*relxilllp Rati
15 model 4b: (partcov*tbnew_feo)*xstar*relxilllp 1.0
0.5
2.0 (b) absorption-dominated: dual-absorber model
χ2 10
∆ o 1.5
ati
R
1.0
0.5
5
3 5 10 30
Energy (keV)
Fig.5.— Data/model ratio plots of the absorption-dominated
models: (a) one neutral partial covering absorber with the cover-
0 ing fraction fixed at 99% and a variable iron abundance; (b) two
0.0 0.2 0.4 0.6 0.8 1.0 partialcoveringabsorbersoffreecoveringfractionsandlinkediron
Spin a abundances. Thedataarerebinnedfordisplayclarity.
Fig. 4.— ∆χ2 as a function of BH spin for the relativistic disk constrained. The primary effect of the iron abundance
reflectionmodelingunder fourdifferentabsorptionscenarios. The parameter is to change the relative strength of the iron
dashed line marks the 90% confidence limit. Model 3a and 4a line and the Compton hump. Because of the low net
favor a high BH spin of a & 0.9. The constraint weakens consid- number counts at the high energy end of the NuSTAR
erablywhenweconsideravariableironabundancefortheneutral
spectra,the shapeoftheComptonhumpisnotwellcon-
absorberinmodel3band4b.
strained, which could make it difficult to obtain a tight
higher. Best-fit parameters of the disk reflection agree
constraintoftheironabundance. We notethatasimilar
well with those given by model 3b, except for a slightly
over-abundance in iron has been reported in a number
higher inclination of θ = 51+−45 degrees. Only a low BH of AGNs (e.g., Risaliti et al. 2009; Patrick et al. 2011)
spincanbe ruledoutatthe 90%confidence levelby this and stellar-mass BHs (e.g., Garc´ıa et al. 2015b), with
model. the examples of well-known narrow-line Seyfert 1 galax-
ies (NLSy1s) 1H0707–495 (Dauser et al. 2012; Kara et
4. DISCUSSION al. 2015) and IRAS13224–3809 (Fabian et al. 2013). In
We test four models under different absorption sce- the case of IRAS05189–2524, the galaxy is undergoing
narios to physically fit for the disk reflection features in intense star formation, so it is expected to be iron en-
IRAS05189–2524, which provide good and comparable riched. Since super-solar metallicities were indicated via
fitsto the2–30keVbroadbandspectrum(fordetails,see spatially resolved optical spectroscopy in the outer disk
Table 3 and Figure 3). With the covering fraction of andthenuclearregionofthegalaxy(Westmoquetteetal.
the neutral absorber fixed at 99%, there is also no large 2012), it is physically reasonable for the iron abundance
discrepancyinthe continuumbelow 2keV.Basedonthe to be high in the accretion disk.
limitedS/Nofthespectrum,wecannotdistinguishwhich
model better describes the data. A super-solar neutral 4.2. Absorption-dominated Models
absorber is a reasonable requirement by the metallicity
Absorptionfrommateriallying relativelydistant from
measurement of the galaxy from the literature, and it
the BH has frequently been proposed as an alternative
reduces the disk iron abundance to a less extreme value.
interpretation of relativistic disk reflection (e.g., Miller
However, detailed modeling of the intrinsic absorption
etal.2008,2009). Toinvestigatewhethertheexcessesin
causes apparent difficulty in disentangling the parame- theFeKbandandabove10keVobservedinIRAS05189–
ter degeneracies. Adding an ionized absorber modeled
2524 can be fully accounted by absorption-dominated
by XSTARhelps to accountfor the possible features of a
models(withoutthereflectioncomponent),wetestmod-
high-velocityoutflowintheFeKband,butisnotstatisti-
eling the 2–30keV spectrum with single and dual par-
callystronglyrequired. Forthreeoutofthefourmodels,
tial covering neutral absorption models with variable
we canrule out aslow orretrogradeBHspinatthe 90% iron abundances. For the single-absorber model13, we
confidence level. In model 3a and 4a, a rapidly spinning fix the covering faction at 99% to avoid large devia-
BH is favored (for the spin constraints, see Figure 4).
tion from the data below 2keV, the same way as in
In addition, we consider the possible contribution from all the previous modeling. With ∆χ2 = 215.6 com-
distant reflection produced in the torus or BLR, but in- pared to model 3b, this scenario can be easily ruled
cluding an extra xillver component does not improve out. The dual-absorber model14 with an iron abun-
the fitting. dance A = 2.2+0.2 provides a better fit for the data,
Fe −0.4
which requires one full covering absorber with the col-
4.1. Super-solar Iron Abundance umn density N = 6.01+0.14 ×1022 cm−2 and an-
H,abs1 −0.93
In our spectral analysis of IRAS05189–2524, all ac-
ceptablefits requireasuper-solarironabundanceforthe 13 (partcov*tbnew feo)*powerlaw
disk reflection component, but the value is not very well 14 (partcov*tbnew feo)*(partcov*tbnew feo)*powerlaw
IRAS05189–2524 7
other of the coverage fraction f = 64 ± 5% with XMM-Newton data taken in 2013. With the broadband
abs2
N = 1.92+0.58 × 1023 cm−2. However, it is still X-ray spectrum, an alternative dual partial covering ab-
H,abs2 −0.18
statistically worse than the reflection-dominated model sorber explanation can be ruled out. Physically model-
with ∆χ2 = 75.6. The model leaves a broad excess in ing with the self-consistent relativistic reflection model
the Fe K band andalso fails to produce the shape of the relxilllpfinds that the reflection is likely to be gener-
Compton hump above 10keV (see Figure 4, panel b), atedfromthe inner rangeof a rapidly spinning BH. The
resembling the case in NGC 1365 (Risaliti et al. 2013) . high reflection fraction measured (Rref ≃ 2.0–3.2) indi-
cates the reflection area is close to the BH, where rela-
tivisticlightbendingeffectsboostthereflectionsignature
4.3. Eddington Ratio and Outflow (Miniutti & Fabian 2004),suggestingthe coronalillumi-
nating source is compact. However, due to the complex
The time-averaged 2–30keV X-ray flux observed by
NuSTAR is 7.1×10−12 ergscm−2 s−1, correspondingto effects from neutral and ionized absorption and the lim-
an intrinsic luminosity of 3.0×1043 ergs s−1 during the ited S/N data, parameter degeneracies preclude putting
a tight, model-independent estimation on the BH spin.
2013 observation. Using the central velocity dispersions
As a merger system, IRAS05189–2524 is an interest-
measured from the Ca II Triplet line widths (Rothberg
ingtargetforthe spinmeasurement,asBHspins arebe-
et al. 2013) and the M -σ relation (Tremaine et al.
BH lieved to encode information about the galaxy evolution
2002), the BH mass of IRAS05189–2524is estimated to
be MBH = 4.2× 108 M⊙. We note the BH mass de- hpirsotpooryse(dBaesrtain&imVoploornttaenrti2tr0a0n8s)i,tiaonndpUhLasIeRiGnsthhaevheiebreaern-
rived from the Ca II Triplet here is more than ten times
chical evolution model of galaxies (Hopkins et al. 2006;
larger than the value measured from CO band heads in
Sanders et al. 1988). Simulations predict it is uncom-
the near infrared (Dasyra et al. 2006). As discussed in
monfor mergersto yieldlargespins, unless alignmentof
Dasyra et al. (2006), CO band heads are often repre-
the spins of the merging BHs with the orbital angular
sentative of young stellar populations, which could lead
momentum is very efficient (Berti & Volonteri 2008).
to systematically lower BH masses for ULIRGs. Com-
With Fe K band absorption features marginally ev-
bined with the bolometric luminosity inferred from the
ident in the residuals, the detection of a high-velocity
infrared(Tengetal.2015),IRAS05189–2524ismeasured
ionizedwindis notstatisticallysignificant. Also,wefind
to be accreting at an Eddington rate λ = L /L
Edd bol Edd theironabundanceoftheneuralabsorberisstronglyde-
of 0.12. Based on the correlation between the photon
generated with the BH spin. Future observations with
indexes and the Eddington ratios of AGNs (Shemmer et
higher S/N data could help disentangle the reflection
al.2008;Brightmanetal.2013,2016),aphotonindexof
Γ ∼ 2.0 would be expected. The photon index obtained component from the underlying continuum and the var-
ious absorption effects. Assuming the source remains at
by our disk reflection modeling with a low cutoff energy
is Γ ≃ 1.7−2.0, which is consistent with the expected the flux level observed in 2013, if the ionized absorption
indeed exists in IRAS05189–2524, simulations indicate
value given the scatter of the relation.
the XSTAR component would be significantly required
In our spectral modeling, we did not detect significant bydatasetswithmorethan∼2timesofexposure,leading
disk winds. Fitting the possible absorption features in
to a > 3σ detection of the ionized absorption features.
the spectrumwith a simple Gaussianabsorptionline us-
With longer observations (500 ks NuSTAR and 300 ks
ingthegabsmodelwouldreachsimilarχ2asthephysical
XSTARgrid,withthebest-fitlinecentroidat∼7.33keV. XthMeMBH-Nsepwintotnoewxiptohsinur∼es3)0,%itowfouunldcebretapinotsysibulnedteoroabllttahine
Although the effect of this ionized absorber on the con-
different absorption scenarios we have discussed above.
tinuum is subtle, we include it in the spectral fitting, as
even mild absorption lying around the Fe K-edge could
influence the BH spin measurement, which is sensitive We thank the anonymous referee for helpful com-
to the profile of the broad iron line. The power of an ments that improved the paper. M.B. acknowledges
outflow scales with the amount of matter being ejected support from NASA Headquarters under the NASA
(King & Pounds 2015). With the rather small column Earth and Space Science Fellowship Program, grant
density measured for the ionized absorption compared NNX14AQ07H. This work was supported under NASA
with that of massive disk winds found in other AGNs Contract No. NNG08FD60C, and made use of data ob-
(e.g., IRAS11119+3257,Tombesiet al.2015),evenifan tained with NuSTAR, a project led by Caltech, funded
UFO indeed exist in IRAS05189–2524 at the epoch of by NASA and managed by NASA/JPL and has utilized
the observation, it is probably not energetic enough to the NUSTARDAS software package, jointly developed
to have a large impact on its galactic environment. by the ASDC (Italy) and Caltech (USA). We thank the
NuSTAROperations,SoftwareandCalibrationteamsfor
supportwiththeexecutionandanalysisoftheseobserva-
5. SUMMARYANDCONCLUSION tions. This research has also made use of data obtained
We detect disk reflection features of a broad iron line withXMM-Newton,anESAsciencemissionwithinstru-
and a Compton reflection hump in IRAS05189–2524, a mentsandcontributionsdirectlyfundedbyESAMember
Seyfert 1h galaxy and ULIRG, from the NuSTAR and States.
REFERENCES
Arnaud,K.A.1996,AstronomicalDataAnalysisSoftwareand Bellocchi,E.,Arribas,S.,Colina,L.,&Miralles-Caballero,D.
Systems V,101,17 2013,A&A,557,A59
Berti,E.,&Volonteri,M.2008,ApJ,684,822-828
8 Xu et al.
Brightman,M.,Masini,A.,Ballantyne,D.R.,etal.2016,ApJ, Parker,M.L.,Wilkins,D.R.,Fabian,A.C.,etal.2014,
826,93 MNRAS,443,1723
Brightman,M.,&Nandra,K.2011, MNRAS,413,1206 Patrick,A.R.,Reeves,J.N.,Lobban,A.P.,Porquet,D.,&
Brightman,M.,Silverman,J.D.,Mainieri,V.,etal.2013, Markowitz,A.G.2011,MNRAS,416,2725
MNRAS,433,2485 Pounds,K.A.,King,A.R.,Page,K.L.,&O’Brien,P.T.2003,
Dasyra,K.M.,Tacconi,L.J.,Davies,R.I.,etal.2006,ApJ,651, MNRAS,346,1025
835 Pounds,K.A.,&King,A.R.2013, MNRAS,433,1369
Dauser,T.,Garc´ıa,J.,Parker,M.L.,Fabian,A.C.,&Wilms,J. Ricci,C.,Tazaki,F.,Ueda,Y.,etal.2014,ApJ,795,147
2014, MNRAS,444,L100 Risaliti,G.,Harrison,F.A.,Madsen,K.K.,etal.2013,Nature,
Dauser,T.,Garcia,J.,Wilms,J.,etal.2013,MNRAS,430,1694 494,449
Dauser,T.,Svoboda, J.,Schartel, N.,etal.2012,MNRAS,422, Risaliti,G.,Miniutti,G.,Elvis,M.,etal.2009,ApJ,696,160
1914 Rivers,E.,Markowitz,A.,&Rothschild,R.2013, ApJ,772,114
Dewangan,G.C.,Griffiths,R.E.,&Schurch,N.J.2003, ApJ, Rothberg,B.,Fischer,J.,Rodrigues,M.,&Sanders,D.B.2013,
592,52 ApJ,767,72
Fabian,A.C.,Kara,E.,Walton, D.J.,etal.2013,MNRAS,429, Rupke,D.S.N.,&Veilleux,S.2015, ApJ,801,126
2917 Rupke,D.S.N.,Veilleux,S.,&Baker,A.J.2008,ApJ,674,
Fabian,A.C.,Rees,M.J.,Stella,L.,&White,N.E.1989, 172-193
MNRAS,238,729 Rupke,D.S.,Veilleux,S.,&Sanders,D.B.2005,ApJ,632,751
Feruglio,C.,Fiore,F.,Carniani,S.,etal.2015, A&A,583,A99 Sanders,D.B.,Soifer,B.T.,Elias,J.H.,etal.1988,ApJ,325,74
Garc´ıa,J.,Dauser,T.,Lohfink, A.,etal.2014, ApJ,782,76 Severgnini,P.,Risaliti,G.,Marconi,A.,Maiolino,R.,&Salvati,
Garc´ıa,J.A.,Dauser,T.,Steiner,J.F.,etal.2015,ApJ,808,L37 M.2001,A&A,368,44
Garc´ıa,J.A.,Steiner,J.F.,McClintock,J.E.,etal.2015,ApJ, Shemmer,O.,Brandt,W.N.,Netzer, H.,Maiolino,R.,&Kaspi,
813,84 S.2008, ApJ,682,81-93
George,I.M.,&Fabian,A.C.1991, MNRAS,249,352 Stru¨der,L.,Briel,U.,Dennerl,K.,etal.2001,A&A,365,L18
Guainazzi,M.,Bianchi,S.,Matt,G.,etal.2010, MNRAS,406, Tan,Y.,Wang,J.X.,Shu,X.W.,&Zhou,Y.2012,ApJ,747,
2013 L11
Haardt,F.,&Maraschi,L.1993,ApJ,413,507 Tanaka,Y.,Nandra,K.,Fabian,A.C.,etal.1995,Nature,375,
Harrison,F.A.,Craig,W.W.,Christensen,F.E.,etal.2013, 659
ApJ,770,103 Teng,S.H.,Rigby,J.R.,Stern,D.,etal.2015,ApJ,814,56
Hopkins,P.F.,Hernquist,L.,Cox,T.J.,etal.2006,ApJS,163,1 Teng,S.H.,Veilleux,S.,Anabuki,N.,etal.2009, ApJ,691,261
Jansen,F.,Lumb,D.,Altieri,B.,etal.2001,A&A,365,L1 Teng,S.H.,Veilleux,S.,&Baker,A.J.2013,ApJ,765,95
Kallman,T.,&Bautista,M.2001,ApJS,133,221 Tombesi,F.,Cappi,M.,Reeves,J.N.,etal.2010,A&A,521,A57
Kara,E.,Fabian,A.C.,Lohfink,A.M.,etal.2015,MNRAS, Tombesi,F.,Mel´endez,M.,Veilleux,S.,etal.2015,Nature,519,
449,234 436
Iwasawa,K.,Fabian,A.C.,Mushotzky, R.F.,etal.1996, Tortosa,A.,Marinucci,A.,Matt,G.,etal.2016,
MNRAS,279,837 arXiv:1612.05871
Kalberla,P.M.W.,Burton,W.B.,Hartmann,D.,etal.2005, Tremaine,S.,Gebhardt,K.,Bender,R.,etal.2002,ApJ,574,740
A&A,440,775 Turner,M.J.L.,Abbey, A.,Arnaud,M.,etal.2001,A&A,365,
King,A.,&Pounds,K.2015,ARA&A,53,115 L27
Laor,A.1991,ApJ,376,90 U,V.,Sanders,D.B.,Mazzarella,J.M.,etal.2012,ApJS,203,9
Lehmer,B.D.,Alexander,D.M.,Bauer,F.E.,etal.2010,ApJ, Ursini,F.,Boissay,R.,Petrucci,P.-O.,etal.2015,A&A,577,A38
724,559 Veilleux,S.,Kim,D.-C.,Sanders,D.B.,Mazzarella,J.M.,&
Madsen,K.K.,Harrison,F.A.,Markwardt,C.B.,etal.2015, Soifer,B.T.1995,ApJS,98,171
ApJS,220,8 Veilleux,S.,Kim,D.-C.,&Sanders,D.B.1999a,ApJ,522,113
Magdziarz,P.,&Zdziarski,A.A.1995,MNRAS,273,837 Veilleux,S.,Mel´endez,M.,Sturm,E.,etal.2013,ApJ,776,27
Markoff,S.,Nowak,M.A.,&Wilms,J.2005, ApJ,635,1203 Veilleux,S.,Sanders,D.B.,&Kim,D.-C.1999b,ApJ,522,139
Matt,G.,Perola,G.C.,Piro,L.,&Stella,L.1992,A&A,257,63 V´eron-Cetty,M.-P.,&V´eron,P.2006,A&A,455,773
Miller,L.,Turner,T.J.,&Reeves,J.N.2008,A&A,483,437 Walton,D.J.,Nardini,E.,Fabian,A.C.,Gallo,L.C.,&Reis,
Miller,L.,Turner,T.J.,&Reeves,J.N.2009,MNRAS,399,L69 R.C.2013, MNRAS,428,2901
Miniutti,G.,&Fabian,A.C.2004,MNRAS,349,1435 Walton,D.J.,Risaliti,G.,Harrison,F.A.,etal.2014, ApJ,788,
Miniutti,G.,Ponti,G.,Dadina,M.,Cappi,M.,&Malaguti,G. 76
2007, MNRAS,375,227 Westmoquette, M.S.,Clements,D.L.,Bendo,G.J.,&Khan,
Murphy,K.D.,&Yaqoob,T.2009,MNRAS,397,1549 S.A.2012, MNRAS,424,416
Nandra,K.,O’Neill,P.M.,George,I.M.,&Reeves,J.N.2007, Wilms,J.,Allen,A.,&McCray,R.2000,ApJ,542,914
MNRAS,382,194 Winter,L.M.,Mushotzky, R.F.,Reynolds,C.S.,&Tueller,J.
Nandra,K.,&Pounds,K.A.1994,MNRAS,268,405 2009,ApJ,680,1322
Nardini,E.,Reeves,J.N.,Gofford,J.,etal.2015, Science,347, Young,S.,Hough,J.H.,Efstathiou,A.,etal.1996, MNRAS,
860 281,1206