Abundance Constraints and Direct Redshift Measurement of the Diffuse X-ray Emission from a Distant Cluster of Galaxies

0.43 MB·English

by  Yasuhiro Hashimoto

Astronomy & Astrophysics manuscript no. ms February 2, 2008
(DOI: will be inserted by hand later)
Abundance Constraints and Direct Redshift Measurement of the
Diffuse X-ray Emission from a Distant Cluster of Galaxies
1 2 1 3 1
Yasuhiro Hashimoto Xavier Barcons Hans B¨ohringer Andrew C. Fabian Gu¨nther Hasinger Vincenzo
1 1
Mainieri and Hermann Brunner
4 1 Max-Planck-Institut fu¨r extraterrestrische Physik,Giessenbachstrasse D-85748 Garching, Germany
0 2 Institutode F´ısica deCantabraia (CSIC-UC),39005 Santander,Spain
0
3 Instituteof Astronomy,Madingley Road, Cambridge, CB3 0HA,UK
2

n
Received ; accepted
a
J
Abstract. WereportontheXMM-Newton(XMM)observationofRXJ1053.7+5735,oneofthemostdistantX-ray
5
selectedclustersofgalaxies,whichalsoshowsanunusualdouble-lobedX-raymorphology,indicativeofapossible
1
equal-mass cluster merger. The cluster was discovered during the ROSAT deep pointings in the direction of the

1 Lockman Hole. All XMM Lockman Hole observations (PV, AO-1 & AO-2 phases) with the European Photon
v ImagingCamera(EPIC)werecombinedfortheanalysis,totalingexposuretimes∼648ks,738ks,and758ksfor
7 pn, MOS1, and MOS2, respectively. With this ‘deep’ dataset, we could detect theFe K line and obtain a strong
9 constraint on cluster metallicity, which is difficult toachieve for clusters at z> 1. Thebest-fit abundanceis 0.46
2 +0.11 times the solar value. The Fe line emission also allows us to directly estimate the redshift of diffuse gas,
−0.07
1 with a value z = 1.14 +0.01. This is one of the first clusters whose X-ray redshift is directly measured prior to
−0.01
0
the secure knowledge of cluster redshift by optical/NIR spectroscopy. We could also estimate the X-ray redshift
4
separately for each ofthetwolobes in thedouble-lobedstructure,and theresult isconsistent with thetwo lobes
0
beingpartofoneclustersystematthesameredshift.Comparison withothermetallicity measurementsofnearby
/
h and distant clusters shows that there is little evolution in theICM metallicity from z ∼ 1 to thepresent.
p
- Key words.Galaxies: clusters: general – X-rays:galaxies – Galaxies: evolution
o
r
t
s
a 1. Introduction X-ray spectroscopic observations provide a powerful
:
v meanstoprobethemetalcontentofthediffusegasinclus-
i The heavy element abundances and their distribution in ters.Inthelate70’s,theironlineemissionwasdiscovered
X
theintraclustermedium(ICM)ofgalaxyclustersprovides intheX-rayspectraofgalaxyclusters(e.g.Serlemitsoset
r
a uswithimportantinformationontheevolutionoftheclus- al. 1977). It was later found that the ICM in z ∼ 0 clus-
tergalaxies,theclustersthemselves,andpossiblytheuni- tersofgalaxieshasbeenenrichedinirontoapproximately
verse as a whole. By tracing the evolution of the global 1/3 of the solar value (e.g. Edge & Stewart 1991). ASCA
metal content of the ICM, one can obtain useful informa- and BeppoSAX showed that the metallicity of the ICM
tion on the epoch where the last major star formation in stays constant at its local value Z = 0.3Z⊙ out to z ∼
clustergalaxiestookplaceandenrichedthediffusecluster 0.4 (e.g. Mushotzky & Loewenstein 1997;Allen & Fabian
gas.Ifclustersarefairsamplesofthe universe,then stud- 1998;DellaCecaetal2000;Matsumotoetal2000;Ettori,
ies of the evolution of the ICM metallicity also constrain Allen& Fabian2001).Theseobservationsclearlyindicate
the star formation history in the universe. Supernova ex- that a significant amount of the metals produced by su-
plosions, which are the main contributor to metal enrich- pernovae were injected by z ≥ 0.4.
ment, may also provide a significant source of heating for
the ICM. Therefore, a knowledge of the metal content of With Chandra and XMM-Newton (XMM) observa-
galaxy clusters allows one to estimate the total amount tions on distant clusters, the evolution of chemical abun-
ofenergysuppliedbysupernovaexplosions(e.g.Pipinoet dancesbeyondz=0.4canbeinvestigated,thusextending
al. 2002). thepreviousanalysisbasedonASCAandBeppoSAXdata
(e.g. Jones et al. 2003; Arnaud et al. 2002; Jeltema et al.
2001; Maughan et al. 2003; Worrall et al. 2003; Holden
Send offprint requests to: Y. Hashimoto, et al. 2002). Tozzi et al. (2003) analyzed mostly-Chandra
e-mail: [e-mail] data of 18 distant clusters with redshift 0.3 < z < 1.3.
2 Hashimoto et al.: Abundanceof z> 1.0 cluster
They report, using a combined spectral fit of cluster sub-
samples indifferentredshift bins,that the meanFe abun-
dance at z ∼ 0.8 is Z = 0.25+−00..0046Z⊙, consistent with the
local metallicity value. Unfortunately, for clusters at red-
shift z > 1, they could only provide weak constraints for
the metallicity (Z = 0.21+−00..1025Z⊙ )even after combining
four clusters.
The cluster RXJ1053.7+5735, which shows an un-
usual double-lobed X-ray morphology, was discovered
during our deep (1.31 Msec) ROSAT HRI pointings
(Hasinger et al. 1998a), in the direction of the “Lockman
Hole”, a line of sight with exceptionally low HI column
density.Theangularsizeofthesourceis1.7×0.7arcmin2
and two lobes are approximately 1 arcmin apart. The to-
talX-rayflux ofthe entire source inthe 0.5-2.0keVband
is 2 × 10−14 erg cm−2 s−1 (Hasinger et al. 1998b). Our Fig.1. The contours of XMM image of the cluster
subsequent deep optical/NIR imaging follow-ups (V < RXJ1053.7+5735overlaidon a CFHT I band image. The
26.5, R < 25, I < 25, K < 20.5) with LRIS and NIRC imagewascreatedbycombiningalleventsinthe0.2-8keV
on Keck, and the Calar Alto Omega Prime camera re- band from three (pn, MOS1, & MOS2)cameras.North is
vealed a bright 7 arcsecond-long arc with an integrated up and Eastis left. The image is 2.′3 × 1.′5 on a side. The
magnitudeofR=21.4aswellasanoverdensityofgalaxies raw data were smoothed with a Gaussian with σ = 7′′.
in both X-ray lobes (e.g. Thompson et al. 2001). Further Thelowestcontouris1.9countsarcsec−2 andthecontour
Keck LRIS/NIRSPEC spectroscopic observations on the interval is 0.2 counts arcsec−2.
bright arc and one of the brightest galaxies near the arc
showed that the former is a lensed galaxy at a redshift
19, 2000 (rev. 70, 71, 73, 74, and 81) for ∼ 170 ks (PV
z = 2.57 while the latter is at a redshift of z = 1.263
phase),theperiodOct.25-Nov.4,2001(rev.344,345,and
(Thompson et al. 2001).DeepVRIzJHKphotometrydata
349) for ∼ 199 ks (AO-1), and the period Oct. 15-Dec. 7,
producedconcordantphotometric redshifts for more than
2002 (rev. 522-528, and 544-548) for ∼ 920 ks (AO-2).
10 objects at redshift of z ∼ 1.1-1.3, confirming that at
Both EPIC cameras, pn and MOS, were operated in Full
leasttheeasternlobeisamassiveclusterathighredshift.
Frame mode and with the medium optical blocking fil-
The improbability of chance alignment and similarity of
ter for the bulk of time, except for the PV observation,
colors for the galaxies in the two X-ray lobes were con-
where the thin filter was used for pn, and thin and thick
sistent with the western lobe also being at z ∼ 1.1-1.3
filters were used for MOS. The light curves were visually
(Thompson et al. 2001).Meanwhile,theX-raydataofthe
inspected,andwediscardedthedatacorrespondingtothe
XMM observation(with a totaleffective exposure time ∼
high particle background (> 8 ct/s for the pn, and > 5.2
100 ks) performed during the PV phase for this cluster
ct/s for MOS1 and MOS2 inside the entire fov in the 0.5-
were analyzed (Hashimoto et al. 2002), yielding a best-
10keVband).Thedatawithpattern>4andpattern>12
fit temperature of 4.9 +1.5 keV, while the metallicity was
−0.9 werealsoexcludedforpnandMOS,respectively,retaining
poorly constrained with an upper limit on the iron abun-
onlysingleanddoubleeventsforpn,andsingletoquadru-
dance of 0.62Z⊙. pleeventsforMOS.Wefurtherremovedthoseeventswith
Here we reportona deep ∼ 1 Msec XMM observation
low spectra quality (i.e. FLAG >0). The remaining expo-
of the cluster RXJ1053.7+5735, based on the data ob-
suretimesafterthiscleaningisapproximately648ks,738
tained during the PV, AO-1, & AO-2 phases. The paper
ks and 758 ks for pn, MOS1, and MOS2, respectively.
is organized as follows. In Sec. 2, we briefly describe the
observationanddatareduction.InSec.3,wefirstpresent
3. RESULTS
spectroscopic analysis of the entire cluster, then of each
lobe. In Sec. 4, we present a discussion of the metallicity
3.1. Overall Cluster Analysis
evolution, as well as the comparison between the X-ray
redshift and optical/infrared redshifts. All uncertainties The spectra were extracted from an elliptical region cen-
quotedareatthe 68%confidence levelsforaoneinterest- tered at the cluster image with a semi-major/minor axis
ing parameterfit. Throughoutthe paper, we useHo = 65 1.′2 & 0.′6, respectively The backgrounds were estimated
km s−1 Mpc−1, Ωm=0.3, and ΩΛ=0.7 from a co-centric annulus region surrounding the cluster
with1.′3(inner)and2.′1(outer)radii,afterremovingpoint
sources.Weobtain4605and4305netsourcecounts(inthe
2. Observations and Data Reduction
0.2-10.0 keV band) for pn and MOS(1+2), respectively.
TheclusterRXJ1053.7+5735wasobservedasapartofthe To correct for vignetting effects, we used the SAS
XMM Lockman Hole observation with European Photon V5.4.1 task EVIGWEIGHT (Arnaud et al. 2002),so that
Imaging Camera (EPIC) during the period April 27-May we can use on-axis effective areas. This task computes a
Hashimoto et al.: Abundanceof z> 1.0 cluster 3
weight coefficient for each event, defined as the ratio of
theeffectiveareaatthephotonpositionandenergytothe
centraleffectiveareaatthatenergy,includingfiltertrans-
mission and quantum efficiency. Redistribution matrices
are generated by the SAS RMFGEN for each pointing,
filter, and detector, and then combined for joint analysis.
We regroupedallthe sourcespectrasothatnoenergybin
had fewer than 50 counts. We fitted the spectra with a
redshiftedMEKALmodel(e.g.Meweetal.1985;Kaastra
& Mewe 1993) using the XSPEC V11.0 (Arnaud 1996).
We fit pn and MOS data (MOS1 and MOS2 are merged)
jointly with common temperature, abundance, and red-
shift,while using separatenormalizationforeachdataset,
and fixing the column density of neutral hydrogen NH at
a value of 5.6 × 1019 cm−2 (Dickey & Lockman 1990).
Fig.3. Two-dimensionalχ2 contoursat68.3%,90%,and
99% confidence levels (∆χ2=2.30, 4.61 and 9.21) for the
temperature kT and the abundance Z/Z⊙ of the cluster
RXJ1053.7+5735. Both the temperature and the abun-
dance are obtained from the joint fit to the pn and MOS
data.
3.2. Substructure
As illustrated in Fig. 1, the cluster RXJ1053.7+5735
shows a clearly double-lobed structure, which extends
roughly in the east-west direction. Using a circular (ra-
dius=0.′47)extractionregioncenteredateachlobe,X-ray
characteristics are investigated for the substructure.
Fig.4showsX-rayspectraandresidualsfortheeastern
lobe (top panel)and for the westernlobe (bottom panel).
Fig. 5 shows two-dimensionalχ2 contours at 68.3%, 90%,
and 99% confidence levels (∆χ2=2.30, 4.61 and 9.21) for
Fig.2. Rebinned spectra, residuals, and best-fit models the eastern and western lobes of the cluster temperature
for cluster RXJ1053.7+5735 with MOS1+2 (lower spec- and redshift, obtained from the joint fit to the pn and
trum) , and pn (upper spectrum) cameras. The crosses MOS data. Our fitting for each lobe shows that kT is
are the observed spectra and the solid lines denote best- 3.4 +0.2 keV & 4.4 +0.3 keV, the redshift is 1.16 +0.02 &
−0.1 −0.3 −0.03
fit models. 1.14+0.02,andtheabundanceis0.41+0.18 &0.62+0.15 for
−0.01 −0.16 −0.14
easternandwesternlobe,respectively(Table1).Notethat
the redshifts of two lobes agree within a statistical limit,
In Fig. 2, the results of the best-fits are shown, while
consistent with the interpretation that two lobes are at
Fig. 3 shows the two-parameter χ2 contours for the clus-
close physical distance.
termetallicityandX-raytemperature.Thebest-fitvalues
based on a simultaneous fit are kT = 3.9 +0.2 keV, an
−0.2
abundance of 0.46 +0.11 times the solar value, and a red- Table 1. Comparison between the two lobes
−0.07
shift z = 1.14 +0.01. Using the best-fit model parameters, (pn+MOS1+MOS2)
−0.01
we derived an unabsorbed (0.2-10) keV flux of f0.2−10 =
2.8× 10−14 ergcm −2 s−1,correspondingto a luminosity Lobe kT Z/Z⊙ Redshift R.χ2(dof)
in the cluster rest frame of L0.2−10 = 2.4 × 1044 erg s−1 (keV) (z)
and a bolometric luminosity ofLbol = 2.8 × 1044 erg s−1. East 3.4+0.2 0.41+0.18 1.16+0.02 1.47(99)
−0.1 −0.16 −0.03
Note that the best-fit redshift is consistent with the red- West 4.4+0.3 0.62+0.15 1.14+0.02 1.00(119)
−0.3 −0.14 −0.01
shift range derived by the photometric redshift technique ALL 3.9+0.2 0.46+0.11 1.14+0.01 1.17(301)
−0.2 −0.07 −0.01
(Thompsonetal.2001),whileitissignificantlylowerthan
the NIR spectroscopic redshift (z=1.26) of one galaxy in
theeasternlobenearthegravitationalarc.Wewillfurther To investigate the indication of detailed temperature
comment about this point in §4. variations in the cluster, we created an X-ray ‘hardness
4 Hashimoto et al.: Abundanceof z> 1.0 cluster
WWEESSTT
EEAASSTT
Fig.5. Two-dimensionalχ2 contoursat68.3%,90%,and
99% confidence levels (∆χ2=2.30, 4.61 and 9.21) for the
temperature kT and the redshift of the eastern and west-
ern lobes of cluster RXJ1053.7+5735.
Fig.4. X-ray spectrum and residuals for the east lobe
(top panel), and for the west lobe (bottom panel).
ratio’ map, whose structure may be interpreted as tem-
perature variations.The X-ray hardness ratio map is cre-
Fig.6. The X-ray hardness ratio map where the hard
ated,first,bymaking hard(1-8keV)andsoft(0.2-1keV)
band image (1-8 keV) is divided by soft band image (0.2-
band images, then by dividing the hard band image by
1 keV). Both images are separately smoothed, before the
thesoftbandimage.Twoimagesareseparatelysmoothed
division,withaGaussianwithσ =7′′.Thefull-band(0.2-
before the division with a Gaussian with σ = 7′′. This
8 keV) contours are overlaid on the hardness ratio map.
map is shown in Fig. 6. The full-band (0.2-8 keV) con-
Illustratively, the ratio = 1.8 here roughly corresponds to
tours are overlaid on the hardness map. Inset shows the
kT ∼9-10keV,whilethevalue1.3correspondstokT ∼3-
hardnessratiomapoftheβmodel(β=0.67,rc=17′.′2)con-
4 keV.Insetshowsthe hardnessratiomapofthe β model
volvedwiththedetectorPSFatthepositionofthecluster
convolved with the detector point spread function (PSF)
(westlobe).Theinsetcoverstheregionoftheskyidentical
at the position of the cluster (westlobe), demonstrating
to the main figure of Fig. 6. The profile of each pointing
that the energy dependence of the detector PSF has neg-
and each detector in 0.2-1, 1-2, 2-5, and 5-8 keV bands
ligible effect on the cluster hardness ratio map.
are separately created by the SAS V.6.0 emldetect task
with a parameterextentmodel=beta. The hard band (1-8
kev)is splitintothree bandsandlatercombined,inorder 5 keV. Fig. 6 shows that the coldest part of the west-
to reflect the cluster X-ray flux in each band. The scale ern lobe may be slightly off-centered toward west, while
bar in the inset is shown as a reference for the image-size the temperature structures of the eastern lobe is aligned
(the color-scales are the same as the main figure). The withrespecttothefull-bandcontours.Theregionbetween
inset demonstrates that the energy dependence of the de- the two lobes seems to have similar temperature with the
tector PSF has negligible effect on the cluster hardness outer regionof each lobe, and seems hotter than the bulk
ratiomap,wherethe bulk ofthe clusteremissionis below of the cluster temperature, however, the influence from
Hashimoto et al.: Abundanceof z> 1.0 cluster 5
the cluster-cluster collision is unclear based on our data. hotcluster-intersectionregionmightbeinterpretedasone
We will further discuss about this point in §4. such‘coldfront’.Note,however,thatourabrupttempera-
tureboundarydoesnotseemtomatchexactlythedensest
part of the gas (as shown by the contours) and therefore
4. Discussion
this tentative interpretation has to be taken with some
4.1. Cluster Redshift caution.
Relatively high Fe abundance of RXJ1053.7+5735 is
The redshift of the cluster diffuse gas directly estimated
somewhatsurprising,particularlyconsideringits redshift.
by fitting the X-ray data is z = 1.14 +0.01. This value is
−0.01 However, it may be explained by the possible existence
withintheclusterredshift-rangeobtainedwiththephoto-
of ‘densed core’ (or ‘colling flow’) in the cluster, and its
metricredshifttechnique.However,itissignificantlylower
relationtotheFeabundance(e.g.Allen&Fabian1998;see
than a redshift (z=1.26), of one cD-like galaxy near the
alsoDeGrandi&Molendi2001).Thehardnessratiomap
eastern-lobe arc, obtained by near infrared spectroscopy.
of RXJ1053.7+5735 may indicate that the temperature
The infraredredshift is practicallydefined by one line de-
is cooler at the center of each lobe, which is consistent
tected at 1.485 µm, which Thompson et al. (2001) inter-
withthecoolingflowinterpretation.However,this‘densed
preted as Hα in light of its photometric redshift.
core’ feature has been considered to be associated with
If the redshift of this cD-like galaxy were at z = 1.14,
a relaxed dynamical state of clusters (e.g. McGlynn &
as indicated by the X-ray redshift, then this emission line
Fabian 1984; Edge, Stewart, & Fabian 1992). If the two
detected in the cD-like galaxy would not correspond to
lobes of RXJ1053.7+5735are indeed interacting, and are
anyprominentline.Moreover,no line is detected at1.404
in the process of nearly-equal-mass merger, it would be
µmwherepossibleHαlineshouldbelocated,ifthegalaxy
unlikelythatthisdynamicalstateexistsinsidethecluster,
isindeedatz=1.14.Therefore,itisunlikelythatredshift
and therefore unlikely to have the ‘densed core’ profile.
of this particular galaxy is at z=1.14.
Unfortunately, the spatial resolution of our data is not
The simplest explanation for this redshift discrepancy
sufficient enough to directly investigate the core profile of
is: the cD-like galaxy is in the background of the clus-
the cluster RXJ1053.7+5735, and therefore, the implied
ter, and therefore, not a member of the cluster (relative
dynamical state of the cluster remains unknown. Future
velocity ∼ 17,000kms−1). Even with the apparent prox-
X-rayobservationswithhighspatialresolution,aswellas
imity of the cD-like galaxy to the gravitational arc and
the optical/NIR spectroscopic observations of individual
to the center of the X-ray contour, this explanation is
clustermembers,areneededformoredefinitivestatement
indeed possible. In fact, there is another cD galaxy can-
about the dynamical state of the cluster.
didate equally close to the center of the X-ray contour.
We obtained DEIMOS/Keck spectroscopy of this galaxy
and our preliminary analysis shows that the redshift of 4.3. Abundance vs. Redshift
the galaxy is consistent with that of X-ray diffuse gas.
In Fig. 7, we compare our newly measured metallicity for
RX J1053.7+5735 with other high redshift clusters ob-
4.2. Dynamical State of the Cluster
served by XMM or Chandra from Tozzi et al. (2003). For
The fact that the X-ray morphology of RXJ1053.7+5735 comparison, the low redshift samples from Mushotzky &
isdouble-lobedsuggeststhatwemaybewitnessingapos- Loewenstein(1997),andIrwin&Bregman(2001)arealso
sibleequal-massmergereventatz>1.Wecouldestimate plotted. The black square denotes the new abundance for
the X-rayredshift separatelyfor eachlobe, andthe result RX J1053.7+5735. The eastern and western lobes of the
is consistent with the interpretation that two lobes are a cluster are also separately shown(labeled as “EastLobe”
part of one cluster system at the same redshift, although and “West Lobe”). The error bars on the abundance are
the dynamical state of the system cannot be definitively one dimensional 68% confidence range. Some 90% errors
known from the redshift-information alone. quoted in the literature are converted to 68% error by
As for the Tx distribution, as shown in Fig. 6, the multiplying by a factor 1/1.6.
inter-lobe regionseems hotter than the bulk of each lobe, Several studies report a hint of a weak dependence
however it is not clear from the figure that the temper- of global Fe abundance on the temperature in such a
ature in that region is actually enhanced, by the mech- way that lower temperature clusters tend to have larger
anism such as a shock induced by the cluster ‘collision’. Fe abundances than hot clusters (e.g. Yamashita 1992;
Relativelyabrupttemperature boundarybetweenthe low Fabian et al. 1994; Mushotzky & Loewenstein 1997;
temperature regionin the westernlobe andthe inter-lobe Matsumoto et al. 2000; Tozzi et al. 2003, see however
region may be similar with the ‘cold fronts’ observed in Fukazawa et al. 1998; Fukazawa et al. 2000). This de-
localclusters (e.g. Markevitchet al. 2000;Vikhlinin et al. pendence may be related to the correlation between the
2001). In these ‘cold fronts’, a sharp temperature gradi- core profile and Fe abundance, which indicates that more
ent forms when a cooler gas blob propagates in a hot- ‘densed core’ or ‘cooling flow’ clusters show the higher
ter ambient gas. The cold western lobe spot which shows Fe abundance (e.g. Allen & Fabian 1998). Regardless of
a steep temperature gradient relative to an intermediate the origin of this Fe dependence on the cluster tempera-
6 Hashimoto et al.: Abundanceof z> 1.0 cluster
1.0 1.0
0.8 0.8
ce 0.6 ce 0.6
n n
a a
d d
n n
u u
b 0.4 b 0.4
A A
0.2 0.2
0.0 0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2
z z
Fig.7. New XMM abundance and its 1σ error (68.3%) 1.0
for RXJ1053.7+5735 plotted with high redshift clusters
from Tozzi et al. (2003). For comparison,the low redshift
0.8
samplesfromMushotzky&Loewenstein(1997),andIrwin
& Bregman (2001) are also plotted.
ce 0.6
n
a
d
ture, Tozzi et al. (2003) subdivided their cluster sample n
u
accordingtothe temperature(the ‘hot’clustersubsample Ab 0.4
with kT > 5 keV and the ‘cold’ cluster subsample with
kT < 5 keV). They investigated the abundance vs. red-
0.2
shift relation separately for each subsample using a com-
bined fit across all of the subsample clusters in different
redshift bins, and reported that at least the high temper- 0.0
0.0 0.2 0.4 0.6 0.8 1.0 1.2
ature subsample reveals no sign of the evolution in their
z
average abundances up to z ∼ 1.2.
Fig.9. AbundancevsRedshiftfortwosubsetsofclusters
1.0
defined by X-ray temperature. Top panel: Clusters with
kT > 5 keV, Bottom panel: clusters with kT < 5 keV
0.8
ce 0.6
n Fig. 8 shows the abundance vs. temperature relation
a
d for the same sample as Fig. 7. The symbols are identi-
n
bu 0.4 cal with Fig. 7. The error bars on the temperature are
A
again68%confidencerange.TheclusterRXJ1053.7+5735
roughlyfollowsaweaktrendthatlowertemperatureclus-
0.2 ters tend to have larger iron abundances than hot clus-
ters. Fig. 9 shows the abundance vs. temperature rela-
0.0 tion for the ‘hotter’ clusters (kT > 5 keV: Fig. 9a), and
2 4 6 8 10 12 14 ‘cooler’ clusters (kT < 5 keV: Fig. 9b). Again, the black
kT(keV) squaredenotes the new abundance forRX J1053.7+5735,
witheasternandwesternlobesseparatelyshown.Forboth
subsamples,thereisnostatistically-significantredshiftde-
Fig.8. NewXMMabundanceandTxandtheir1σerrors pendence, while the mean abundance is somewhat higher
(68.3%) for RXJ1053.7+5735 plotted with high redshift forthecoolersubsample.Theresultisconsistentwithno-
clusters from Tozzi et al. (2003). The low redshift sam- evolution of the Fe abundance at z ∼ 1.2, supporting the
ples from Mushotzky & Loewenstein (1997), and Irwin & scenario that much of the enrichment and star formation
Bregman (2001) are also plotted. took place earlier.
Hashimoto et al.: Abundanceof z> 1.0 cluster 7
The cluster RX J1053.7+5735 is now one of the first ThompsonD.,PozzettiL.,HasingerG,etal.,2001,A&A377,
clusterswhoseX-rayredshiftisdirectlymeasuredpriorto 778
the secureknowledgeofthe clusterredshiftobtainedwith Tozzi P., Rosati P., Ettori S., et al. 2003, ApJ593, 705
optical/NIR spectroscopy. Deep pointings with the cur- VikhlininA.,MarkevitchM.,MurrayS.S.,2001, ApJ551,160
Worrall D.M., & Birkinshaw M., 2003, MNRAS340, 1261
rent X-ray satellites provide a powerful means to study
Yamashita K., 1992, in Frontiers of X-ray Astronomy, ed.
the high-redshiftclusters,enabling us to directly measure
Tanaka Y. & Koyama K. (Tokyo: Universal Academy
the redshifts, and to probe the metal contents, of the dif-
Press)
fuse gas in the clusters. The high-throughput X-ray spec-
troscopicmissioninthefuture,suchasCon-XandXEUS,
should make these studies almost a routine.
Acknowledgements. We thank Pat Henry for a careful read-
ing of the paper and useful comments. XB acknowledges par-
tial financial support by the Spanish Ministerio de Ciencia y
Tecnolog´ıa,underprojectAYA2000-1690.Weacknowledgeref-
eree’s comments which improved the manuscript.
References
Allen S.W., & Fabian A.C. 1998, MNRAS,297, L63
Arnaud K.A.,1996, In ASPConference Series, Vol101, 17
Arnaud M., Majerowicz S., Neumann D.M., et al. 2002, A&A
390, 27
DeGrandi S., & Molendi S. 2001, ApJ 551, 153
Della Ceca R., Scaramella R., Gioia I.M., Rosati P., Fiore F.,
& SquiresG. 2000 A&A 353, 498
Dickey J.M., & Lockman F.J. 1990 ARA&A28, 215
Edge A.C., & Stewart G.C. 1991, MNRAS,252, 428
EdgeA.C.,StewartG.C., &FabianA.C.,1992, MNRAS,255,
431
Ettori S., Allen S.W., & Fabian A.C., 2001, MNRAS 322, 187
Fabian A.C., Crawford C.S., Edge A.C., & Mushotzky R.F.,
1994, MNRAS,267, 779
FukazawaY.,Makishima K.,TamuraT,et al.1998 PASJ,50,
187
Fukazawa Y., Makishima K., Tamura T, et al. 2000 MNRAS,
313, 21
Hashimoto, Y., Hasinger G., Arnaud M., Rosati P., & Miyaji
T., 2002, A&A381, 841
HasingerG.,BurgR.,GiacconiR.,etal.,1998a,A&A329,482
Hasinger G., Giacconi R., Gunn J.E., et al., 1998b, A&A340,
L27
HoldenB.P., Stanford S.A.,SquiresG.K., etal. 2002, AJ124,
33
Irwin J.A., & Bregman J.N., 2001, ApJ546, 150
Jeltema T.E., Canizares C.R., Bautz M.W., Malm M.R.,
Donahue M., Garmire G.P. 2001, ApJ562, 124
Jones C., Maughan B.J., Ebeling H. et al. 2003,
astro-ph/0304264
Kaastra J.S., & Mewe R. 1993, A&AS,97, 443
Matsumoto,H.,Tsuru,T.,Fukazawa,Y.etal.2000,PASJ52,
153
Maughan B.J., Jones L.R., Ebeling H. et al. 2003, ApJ 587,
589
MeweR.,GronenschildE.H.B.M.,&vandenOordG.H.J1985,
A&AS,62, 197
Markevitch, M. et al. 2000, ApJ541, 542
McGlynn T.A., & Fabian A.C., 1984, MNRAS,208, 709
Mushotzky R., Loewenstein M., 1997, ApJ481, L63
PipinoA.,MatteucciF.,BorganiS.,etal., 2002,NewA7,227
Serlemitsos P.J, Smith B.W., Boldt E.A., Holt S.S., & Swank
J.H., 1977, ApJ211, L63