XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster ClJ120958.9+495352 (z=0.902)
Sophia Thölken, Tim Schrabback, Thomas H. Reiprich, Lorenzo Lovisari, Steven W. Allen, Henk Hoekstra, Douglas Applegate, Axel Buddendiek, Amalia Hicks
AAstronomy & Astrophysics manuscript no. submit c (cid:13)
ESO 2017November 27, 2017
XMM-Newton X-ray and HST weak gravitational lensing study ofthe extremely X-ray luminous galaxy cluster Cl J z = . ) Sophia Th¨olken , Tim Schrabback , Thomas H. Reiprich , Lorenzo Lovisari , Steven W. Allen , , , Henk Hoekstra ,Douglas Applegate , Axel Buddendiek , and Amalia Hicks Argelander-Institut f¨ur Astronomie, Universit¨at Bonn, Auf dem H¨ugel 71, 53121 Bonn, Germanye-mail: [email protected] Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085, USA Department of Physics, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085, USA SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, the Netherlands Kavli Institute for Cosmological Physics, University of Chicago, 5640 S Ellis Ave, Chicago, IL 60637 Cadmus, Energy Services Division, 16 N. Carroll Street, Suite 900, Madison, WI 53703Received date / Accepted date
ABSTRACT
Context.
Observations of relaxed, massive and distant clusters can provide important tests of standard cosmological models, forexample by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to beinvestigated. X-ray analyses provide one of the best opportunities to access this information and to determine important propertiessuch as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analysesare complementary independent probes that are essential in order to test whether X-ray masses could be biased.
Aims.
We study the very luminous, high redshift ( z = . J + Methods.
We perform a spectral analysis using an XMM-Newton observation of 15 ks cleaned exposure time. As the treatment ofthe background is crucial, we use two di ff erent approaches to account for the background emission to verify our results. We accountfor point spread function e ff ects and deproject our results to estimate the gas mass fraction of the cluster. We measure weak lensinggalaxy shapes from mosaic HST imaging and select background galaxies photometrically in combination with imaging data from theWilliam Herschel Telescope. Results.
The X-ray luminosity of Cl J + . − . L X = (13 . + . − . ) × erg / s and thus it is one of the most X-ray luminous clusters known at similarly high redshift. We find clear indicationsfor the presence of a cool core from the temperature profile and the central cooling time, which is very rare at such high redshifts.Based on the weak lensing analysis, we estimate a cluster mass of M / M (cid:12) = . + . − . (stat . ) ± . . ) and a gas mass fraction of f gas , = . + . − . in good agreement with previous findings for high redshift and local clusters. Key words. galaxies: clusters: general - galaxies: clusters: individual: Cl J +
1. Introduction
In the paradigm of hierarchical structure formation very massiveand distant clusters should be extremely rare. These clusters pro-vide the opportunity for many interesting astrophysical and cos-mological studies. The gas mass fraction ( f gas ) of dynamicallyrelaxed clusters is an important probe of cosmological models(Allen et al. 2008, Mantz et al. 2014) as the matter content ofthese objects should approximately match the matter content ofthe universe (e.g., White et al. 1993, Allen et al. 2011, and refer-ences therein). In particular high-redshift clusters are of interestwhere the leverage on the cosmology is largest.The cooling time for these clusters is very short and thepresence of a cool core is believed to be strongly related tothe dynamical status of the cluster (e.g., Hudson et al. 2010). McDonald et al. (2017) studied the evolution of the ICM andcool core clusters over the past 10 Gyr. Their results imply thatfrom redshift z = z = . J + J + a r X i v : . [ a s t r o - ph . C O ] N ov . Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . ter cores such as MACS J z >
1, Cl J + z = . z = . J + < . z = .
87 with L X = (2 . ± . × h − erg / s (Menanteau et al. 2012) whichis one of the most massive and luminous clusters found so far.For cosmological tests, the total cluster mass is an impor-tant quantity for which weak gravitational lensing provides anindependent probe in addition to the X-ray hydrostatic mass.The gravitational potential imprints coherent distortions onto theobserved shapes of background galaxies (e.g., Bartelmann &Schneider 2001; Schneider 2006). Measurements of these weaklensing distortions directly constrain the projected mass distri-butions and cluster masses (Hoekstra et al. 2013). These mea-surements are sensitive to the total matter distribution, includingboth dark matter and baryons. Especially at high redshifts, theHubble Space Telescope (HST) is an essential tool for the anal-ysis of such objects as ground-based telescopes are not able toresolve the shapes of the very distant background galaxies.Recently, Buddendiek et al. (2015) performed a combinedsearch of distant massive clusters using ROSAT All Sky Surveyand Sloan Digital Sky Survey (SDSS) data covering an area of10,000 deg . They found 83 high-grade candidates for X-ray lu-minous clusters between 0 . < z < WilliamHerschel Telescope (WHT) or Large Binocular Telescope (LBT)imaging to confirm the candidates. One of the clusters they foundis special in many respects: Cl J + Fig. 1.
Combined, cleaned, exposure corrected, and smoothedMOS image of Cl J + J + z ∼ .
9. It is thus a valuable candidatefor a distant cooling-core cluster and provides a great opportu-nity to study one of these rare systems in detail.In this work we perform a spectroscopic XMM-Newton andHST weak lensing study of this extraordinary object found byBuddendiek et al. (2015). We investigate the temperature profilewith respect to the presence of a cool core and determine thecooling time within <
100 kpc. In Sec. 2 we describe the prop-erties of Cl J + Λ CDM cosmologywith H =
70 km / s / Mpc, Ω m = . Ω Λ = .
7. All uncer-tainties are given at the 68% confidence level and overdensitiesrefer to the critical density. All magnitudes are in the AB system.
2. Observations and data analysis Cl J + L obs , . − . = . ± . × erg / s (Buddendiek et al. 2015). They measure thespectroscopic redshift to be z = .
902 and their SZ data yields amass of M = (5 . ± . × h − M (cid:12) .We analyze XMM-Newton observations of the cluster with ∼
15 ks cleaned exposure time (XMM-Newton observation IDs0722530101 and 0722530201, PI of the joint XMM-Newtonand HST program: T. Schrabback). The observations were per-formed in October and November 2013 (see Tab. 1) and wereexecuted over the course of two revolutions, which we analyzesimultaneously.Following the standard data reduction procedure using SASversion 14.0.0, we use the ODF data and apply cifbuild to catchup with the latest calibration and odfingest to update the ODFsummary file with the necessary instrumental housekeeping in-formation. Then we proceed by applying emchain and epchain (for MOS and PN detector, respectively) to create calibratedevent files.On these calibrated files we apply the following filters forthe event pattern of the triggered CCD pixels (the numberingis based to the ASCA GRADE selection) and the quality flagof the pixels: PATTERN ≤
12 for the MOS detectors, for PNPATTERN =
0; FLAG = . −
10 keV. The observationin the second revolution shows strong flaring for a large fractionof the exposure time. We apply a 3 σ clipping to all the lightcurves to filter the flared time intervals and inspected the lightcurves afterwards which then show no further hint of flaring. see heasarc.gsfc.nasa.gov/docs/xmm/abc/
2. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . Table 1.
Details of the XMM-Newton observation ofCl J + Rev. date R.A. Dec. Cleanedexp. time Filter2545 Oct. 2013 182.512 49.926 9.6 ks thick2546 Nov. 2013 182.510 49.924 5.1 ks thick
This removes approximately half of the exposure time for thesecond observation (revolution 2546).To detect point sources in the field of view (FOV), we createimages from the event files for all detectors in five energy bandsbetween 0 . −
12 keV. These images are provided in the task edetect chain . An X-ray image of the cluster is shown in Fig. 1. We se-lect three annular regions around the center and choose theregion sizes such that we can achieve a S / Bkg ratio (i.e.,counts source / counts bk g ) of ∼ (cid:48) − . (cid:48) , . (cid:48) − . (cid:48) , and 0 . (cid:48) − . (cid:48)
3. We fit the spectra of allannuli and for all detectors and the two observations simultane-ously using the Cash-Statistic (cstat option) in XSPEC. For thecluster emission we use an absorbed APEC model with a col-umn density from Willingale et al. (2013), which also includesmolecular hydrogen and the solar metal abundance table fromAsplund et al. (2009). We assume the same abundance in allannuli and thus link the corresponding model parameters. TheXMM-Newton point spread function (PSF) is ∼ (cid:48)(cid:48) HEW. Wecorrect for the e ff ect of photon mixing between di ff erent annulidue of the PSF as described in Sec. 2.1.5.From our HST data (Sec. 3.1) we estimate R = . (cid:48) ff erentbackground components are described in Sec. 2.1.3 and 2.1.4and we follow two approaches for the treatment of the back-ground:1. Background modeling
One approach is to model all thedi ff erent background components individually in the fittingprocedure. These components are described in the follow-ing sections. We determine models for the quiescent parti-cle background and the X-ray background and use them inthe fitting of the cluster emission. We additionally introducea power-law model to account for the residual soft protonemission, which is left over emission after the flare filtering.The index is linked for the two MOS detectors while the nor-malizations for each detector are independent. We use an en-ergy range between 0 . −
10 keV. The results of this approachcan be found in Sec. 3.2.2.
Background subtraction
The cluster has a small extent onthe sky, thus we do not expect significant cluster emissionbeyond R = . (cid:48) estimated from our HST data. For thisreason we are able to subtract the full background from thespectra. To do so, we extract background spectra in an annu-lus between 3 (cid:48) − (cid:48) . This region lies completely on the MOSCCD1 chips which is important because the particle back-ground shows strong variations between the di ff erent chips.Also for PN this region is close enough to the source extrac-tion region to properly model the Ni and Cu lines. As for the first method, the energy range is 0 . −
10 keV and the resultsof this procedure are described in Sec. 3.2.
The quiescent particle background (QPB) is caused by highlyenergetic particles interacting with the detector and the sur-rounding material. It is composed of a continuum emission andfluorescent lines from various elements contained in the assem-bly of the satellite. XMM-Newton is equipped with a filter wheelsystem which can be used to measure the level of the QPB. Whenthe filter is closed, only the high energy particles can penetratethe filter and a spectrum of the QPB can be obtained. We usemerged event files of the filter-wheel-closed observations whichare close to the time of the observation (revolution 2514 − − (cid:48) − (cid:48) (the source region,which lies completely on CCD1 for the MOS destectors) andfrom 7 (cid:48) − (cid:48) (the region where we determine the X-ray back-ground, see Sec. 2.1.4) – for all detectors independently. For theQPB, diagonal responses are used in the fit and no ancillary re-sponse file (ARF) is applied as these particles do not su ff er frominstrumental e ff ects such as vignetting. The spectra with the bestfit models are shown in Fig. 2. When fitting the cluster emission,the QPB normalizations of the power-law components and theGaussian lines are allowed to vary separately by ±
20 %, due topossible spatial and temporal variations of the QPB.
The X-ray background (XRBG) emission is caused by di ff erentsources: 1.) a local component and solar wind charge exchange,2.) a component from the Milky Way halo plasma, and 3.) thesuperposition of the X-ray emission from distant AGNs causinga di ff use background (CXB). To model these background com-ponents we extract a spectrum in a region 7 (cid:48) − (cid:48) , where no clus-ter emission is expected. Additionally, ROSAT All-Sky-Survey − − − − − − no r m a li z ed c oun t s s − k e V − − ( da t a − m ode l ) / e rr o r Energy (keV)
Fig. 2.
Spectra and best fit models of the QPB obtained fromthe filter-wheel-closed observations and extracted on the centralchip in the region 0 (cid:48) − (cid:48) for MOS1 (black), MOS2 (red) and PN(green) and normalized to the extraction area.
3. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . − − − − − no r m a li z ed c oun t s s − k e V − − ( da t a − m ode l ) / e rr o r Energy (keV)
Fig. 3.
Spectra and best fit models for the XRBG + QPB forMOS1 (black), MOS2 (red), and PN (green) in the region 7 (cid:48) − (cid:48) . The di ff erent components of the XRBG are shown as dotted,dash-dotted and dashed lines for the local, halo and CXB com-ponent, respectively. The power law component for the residualsoft proton emission is shown as short-dashed line. For the spec-tra and models of the QPB see Fig. 2.data are used to support the estimation of the background pa-rameters at energies between 0 . − . (cid:48) − (cid:48) with two floating multiplicative con-stants ( ± ff erentcomponents are shown in Fig. 3 for the o ff -axis region between7 (cid:48) and 12 (cid:48) . The extent of the cluster on the sky is small; therefore, we haveto choose annular region sizes which su ff er from the PSF size ofXMM-Newton. This causes “mixing” of photons, i.e., photonsoriginating from a certain region on the sky are detected in an-other region on the detector. This has an impact on the spectraand influences the measurements, especially the determinationof the temperature profile. To avoid this we introduce a PSF cor-rection. The XMM-Newton task arfgen allows us to calculatecross-region ARFs. Via these cross-region ARFs the e ff ectivearea for the emission coming from one particular region, but de-tected in another, is estimated. These ARFs can then be used inthe fitting process to account for the PSF e ff ects. Therefore, weintroduced additional absorbed APEC models for each combi-nation of photon mixing (e.g., photons from region 1 on the sky obtained with the HEASARC X-ray background tool heasarc.gsfc.nasa.gov/cgi-bin/Tools/xraybg/xraybg.pl but detected in region 2 on the detector, etc.). These models usethe cross-region ARFs and the model parameters are linked tothe parameters of the annulus the emission truly originates from,as described in the corresponding SAS-thread . We neglect thePSF e ff ects for the emission coming from the outermost annulusto the two inner annuli as the e ff ective area for this mixing isclose to zero. Here we perform a weak gravitational lensing analy-sis based on new Hubble Space Telescope observationsof Cl J + + HST program (HST program ID 13493). Weak lensingmeasurements require accurate measurements of the shapes ofbackground galaxies well behind the cluster. Given the high red-shift of Cl J + z (cid:38) .
4. As most of them are unresolvedin ground-based seeing-limited data, HST observations are keyfor this study. Specifically, we analyze observations obtainedwith the
Advanced Camera for Surveys (ACS) in the F606W fil-ter in a 2 × ∼ . (cid:48) × . (cid:48) ∼ . × . ), with integration times of 1.9 ks per pointing,each split into four exposures.The data reduction and analysis is conducted with the samepipeline that was used for the weak lensing analysis of high-redshift galaxy clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey (Bleem et al. 2015) presented in Schrabbacket al. (2016, hereafter S16). Therefore, we only summarize themain analysis steps here and refer the reader to S16 for furtherdetails.For the ACS data reduction we employ basic calibrationsfrom CALACS , the correction for charge-transfer ine ffi ciencyfrom Massey et al. (2014), MultiDrizzle (Koekemoer et al.2003) for the cosmic ray removal and stacking, and scriptsfor the image registration and improvement of masks fromSchrabback et al. (2010). We detect objects using
SourceExtractor (Bertin & Arnouts 1996) and measure shapes us-ing the KSB + formalism (Kaiser et al. 1995; Luppino & Kaiser1997; Hoekstra et al. 1998) as implemented by Erben et al.(2001) with adaptions for HST measurements described inSchrabback et al. (2007, 2010). In particular, we apply a modelfor the temporally and spatially varying HST PSF constructedfrom a principal component analysis of ACS stellar field ob-servations. In order to estimate cluster masses from weak lens-ing, accurate knowledge of the source redshift distribution is re-quired. Here we follow the approach from S16, who first ap-ply a color selection to remove cluster galaxies from the sourcesample, and then estimate the redshift distribution based onCANDELS photometric redshift catalogs (Skelton et al. 2014),to which they apply consistent selection criteria, as used in thecluster fields, and statistical corrections for photometric redshiftoutliers.For the color selection we make use of additional i -band observations of Cl J + + × . (cid:48)(cid:48)
27 and an 18 (cid:48) × (cid:48) field of view. We reduce these data us-ing theli (Erben et al. 2005; Schirmer 2013), co-adding ex- cosmos.esa.int/web/xmm-newton/sas-thread-esasspec
4. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . posures of a total integration time of 13 . σ limit of i WHT , lim (cid:39) . (cid:48)(cid:48) , withan image quality of 2 r f = . (cid:48)(cid:48)
2, where r f corresponds to theFLUX RADIUS parameter from Source Extractor . We useSDSS (SDSS Collaboration et al. 2016) for the photometric cal-ibration and convolve the ACS F606W imaging to the ground-based resolution to measure V , con − i WHT colors. For galaxiesat the cluster redshift the 4000Å / Balmer break is located withinthis filter pair. Therefore, by selecting very blue galaxies in thiscolor, we can cleanly remove the cluster galaxies, while se-lecting the majority of the z (cid:38) . V , con − i WHT < .
16 ( V , con − i WHT < − .
04) for galax-ies with magnitudes 24 < V < . . < V <
26) mea-sured in 0 . (cid:48)(cid:48) V − I < . V − I < . J + V , auto < . Source Extractor automagnitude, which results in a final galaxy number density of9.6 / arcmin , while the shape catalog extends to V , auto (cid:39) . ff ective mean geometric lensing e ffi ciencyof (cid:104) β (cid:105) = . ± . . ) ± . . ) based on theCANDELS analysis (see S16 for details).
3. Results
In Fig. 4 we show contours of the weak lensing mass recon-struction of Cl J + / WFC F606W imaging and WFC3 / IR imaging ob-tained in F105W (1.2 ks) and F140W (0.8 ks). The reconstruc-tion employs a Wiener filter (McInnes et al. 2009; Simon et al.2009), as further detailed in S16. Divided by the r.m.s. imageof the reconstructions of 500 noise fields, the contours indicatethe signal-to-noise ratio of the weak lensing mass reconstruc-tion, starting at 2 σ in steps of 0 . σ . The reconstruction peaksat R . A . = δ =+ (cid:48)(cid:48) in each direction (estimated by bootstrapping thesource catalog), which makes it consistent with the locations ofthe X-ray peak and the BCG at the 1 σ level.Fig. 5 displays the measured tangential reduced shearprofile of Cl J + < V , aper < ≤ r ≤ . M / M (cid:12) = . + . − . (stat . ) ± . . ) and M / M (cid:12) = . + . − . (stat . ) ± . . ).Here we have corrected for a small expected bias of − − M ( M ) caused by the simplistic mass model,as estimated by S16 and further detailed in Applegate et al. (inprep.) using the analysis of simulated cluster weak lensingdata. Di ff ering from S16 we assume negligible miscenteringfor the bias correction, justified by the regular morphology ofthe cluster and precise estimate of the X-ray cluster center.The quoted statistical uncertainty includes shape noise, uncor-related large-scale structure projections, and line-of-sight vari-ations in the source redshift distribution, while the systematicerror estimate takes shear calibration, redshift errors, and massmodeling uncertainties into account (see S16 for details). Herewe have doubled the systematic mass modeling uncertaintiesused in S16 as we include somewhat smaller scales in thefit . When restricting the radial range in the fit to the moreconservative range 500 kpc ≤ r ≤ . M / M (cid:12) = . + . − . (stat . ) ± . . ) and M / M (cid:12) = . + . − . (stat . ) ± . . ) with smaller expectedand corrected biases of 3% (5%) for M ( M ) and smallersystematic uncertainties, but increased statistical errors.For the comparison to the X-ray measurements we ad-ditionally require weak lensing mass estimates for an over-density ∆ = , the weak lensing mass constraints corre-spond to M / M (cid:12) = . + . − . (stat . ) ± . . ) when in-cluding measurements from scales 300 kpc ≤ r ≤ . M / M (cid:12) = . + . − . (stat . ) ± . . ) when restricting theanalysis to scales 500 kpc ≤ r ≤ . ≤ r ≤ . ff erent concentrations. Based on simulations, Du ff y et al.(2008) find that the scatter around the median concentrationis approximately lognormal with σ (log c ) = .
11 for re-laxed clusters. Approximately matching the expected 1 σ lim-its, fixed concentrations c = . c = .
0) change the bestfit mass constraints for M , M , M by + , + , − − , − , + c = . In the analysis of simulated data we find that the mass biases in-crease by factors of ∼ . − . >
500 kpc from S16 to >
300 kpc as employed here. FollowingS16, we estimate the residual uncertainty of the bias correction as a rel-ative factor of the bias value. Accordingly, the uncertainty increases byapproximately a factor of two. This is necessary given that the analysis from S16 as a function oflog ∆ provides bias estimates for ∆ =
200 and ∆ =
500 only, as masses M are not available for the simulations used to derive the bias values.We do propagate the statistical uncertainty of this extrapolation, but notethat it is negligible compared to the statistical uncertainty of the massconstraints for Cl J + J + z = . h m s s m s s s RA (J2000) +49 ◦ ′ ′′ ′′ ′ ′′ ′′ ′ ′′ D e c ( J2000 ) Fig. 4.
HST 2 . (cid:48) × . (cid:48) J + / WFC F606W (blue)and WFC3 / IR F105W (green), and F140W (red) imaging. Thewhite contours indicate the signal-to-noise ratio of the weaklensing mass reconstruction, starting at 2 σ in steps of 0 . σ , withthe cross marking the peak position, which is consistent withthe X-ray peak (red square) and BCG position (magenta star)within the uncertainty of 23 (cid:48)(cid:48) in each direction.certainties of the study presented here. It should be noted thatthis analysis assumes spherical cluster models, which can leadto extra scatter due to triaxiality when comparing to X-ray re-sults.In Fig. 4, the signal-to-noise ratio contours of the massreconstruction appear to be slightly elliptical, extending to-wards the south-southwest, which is tentatively in agreementwith the location of some apparent early-type cluster galaxies.To investigate whether this elliptical shape is actually signif-icant, we estimate the shape of the mass peak using SourceExtractor both for the actual mass reconstruction and thereconstructions originating from the bootstrap-resampled cat-alogs. Using the
Source Extractor estimates of the semi-major and semi-minor axes a and b , as well as the position an-gle φ measured towards the north from west, we compute com-plex ellipticities e = e + i e = | e | e φ with | e | = ( a − b ) / ( a + b ),as employed in weak lensing notation (e.g., Bartelmann &Schneider 2001). Using the dispersion of the estimates fromthe boostrapped samples as errors, our resulting estimate e = ( − . ± . + i ( − . ± .
16) is consistent with a roundmass distribution ( e = The global properties for both methods of the treatment of thebackground are summarized in Tab. 2. The overall propertiesagree well between the two methods.The rest-frame luminosity of the cluster in the0 . − . L X = (13 . + . − . ) × erg / s and L X = (13 . + . − . ) × erg / s, for background-modeling andbackground-subtraction method, respectively, estimated fromthe spectral fit. It is thus comparable to the most X-ray luminous Fig. 5.
Tangential reduced shear profile (black solid circles)of Cl J + < V , aper <
26, as done in S16. The curve shows the cor-responding best fitting NFW model prediction constrained byfitting the data within the range 300 kpc ≤ r ≤ . dr = − .
05 Mpc for clarity.
Table 2.
Global cluster properties between 0 (cid:48) < R < . (cid:48) background-modeling background-subtraction T [keV] 9 . + . − . . + . − . Z [ Z (cid:12) ] 0 . + . − . . + . − . norm . + . − . . + . − . norm = − π [ D A (1 + z )] (cid:82) n e n H d V cm − with D A being the angular diameter dis-tance to the source. MACS clusters, but at even higher redshift. These values arealso in very good agreement with the findings by Buddendieket al. (2015) after applying a K-correction.
We compare the results for the two approaches of the back-ground treatment for temperature and density profile. Fig. 6shows the temperature profile of Cl J + J +
6. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . R (arcmin) k T ( ke V ) R (kpc)
Fig. 6.
Deprojected and PSF-corrected temperature profileof Cl J + Table 3.
Fit results for the three radial bins for both methodsof background treatment. The abundance is linked between allannuli. (cid:48) − . (cid:48) . (cid:48) − . (cid:48) . (cid:48) − . (cid:48) T [keV] 7 . + . − . . + . − . . + . − . Z [ Z (cid:12) ] 0 . + . − . norm . + . − . . + . − . . + . − . background-subtraction T [keV] 7 . + . − . . + . − . . + . − . Z [ Z (cid:12) ] 0 . + . − . norm . + . − . . + . − . . + . − . norm = − π [ D A (1 + z )] (cid:82) n e n H d V cm − with D A being the angular diameter dis-tance to the source. applied, the cool core remains and the uncertainty of the secondtemperature decreases by a factor of ∼ ∼ N i = − π D (1 + z ) (cid:90) V i n e ( R ) n H ( R ) d V , (1)where i corresponds to the i th annulus from the center and D A is the angular diameter distance to the source. The volume alongthe line of sight V i is the corresponding cylindrical cut througha sphere with inner and outer radii of the i th annulus. We adopt n e = . n H . Due to the small extent of the cluster, there is onlylimited radial resolution. Therefore, we perform a simple depro-jection method following Ettori et al. (2002). R (arcmin) ) - ( c m e n -3 -2 R (kpc)
Fig. 7.
Deprojected and PSF-corrected electron density profile ofCl J + EI i ) and temperature ( T i ) in ring i aregiven by EI i = N (cid:88) j = i n e n H V i , j (2) T i = (cid:80) Nj = i (cid:15) j V i , j T j (cid:80) Nj = i (cid:15) j V i , j , (3)with V i , j being the volume of the cylindrical cut correspondingto ring i through spherical shell j , n e and n H the electron andproton density, and (cid:15) the emissivity. By subtracting the contri-bution of the overlying shells in each annulus, we determine thedeprojected electron density profiles for both background treat-ment methods shown in Fig. 7. As for the temperature, the twodensity profiles agree very well showing that our backgroundtreatment works well in both cases.As an additional test for the background-subtraction methodwe choose an even larger inner radius of the background region(4 (cid:48) − (cid:48) ) and repeat the analysis. We find only marginal di ff er-ences and thus conclude that no significant cluster emission ispresent in the background-region.As can be seen in Fig. 1, we detect a point source close tothe center of the cluster. To investigate the impact of the pointsource, we increase the exclusion radius around this source by50% and repeat the fit. Due to the lowered statistics, the uncer-tainties clearly increase but we find no significant impact com-pared to the nominal values. From the gas mass profile and the total mass M tot ( < R ) inside agiven radius R , the gas mass fraction can be obtained: f gas ( < R ) = M gas ( < R ) M tot ( < R ) . (4)We note that, given the limited XMM-Newton spatial res-olution, a very robust determination of the total mass from the
7. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . hydrostatic equation is di ffi cult as this would require high spa-tial resolution measurements of the density and temperature pro-file. Therefore, we use the total mass based on our weak lensingHST estimates and the corresponding R (see Sec. 3.1). As across-check, we also determine the gas-mass fraction using the L X − M relation obtained by Hoekstra (2007) for the totalmass.The HST results yield M / M (cid:12) = . + . − . (stat . ) ± . . ). For the estimation of f gas , we include an addi-tional 30% triaxiality / projection uncertainty and a 10% uncer-tainty from the mass-concentration relation on M . From10000 Monte Carlo (MC) realizations of M , we estimate R = . (cid:48) + . − . and for each realization the gas masswithin the corresponding R , assuming a constant density ineach shell. This yields M gas , = (1 . + . − . ) × M (cid:12) and M gas , = (1 . + . − . ) × M (cid:12) for the background-subtractionand background-modeling method, respectively, which are invery good agreement. Combining these results, we estimate f gas , = . + . − . for both methods. We note that through thisprocedure the given uncertainties on M , M gas , , and R are, on the one hand, correlated and, on the other hand, the as-sumption of constant density in each shell is only a rough ap-proximation, which is why the uncertainty on f gas , is lowerthan naively expected. A more general estimate is obtained byusing a beta-model for the density profile and following the sameprocedure as described above. We fix the core radius to a typicalvalue of R c = . × R and assume a slope of β = / R is estimated from our HST results. This yields f gas = . + . − . for both background methods. Yet another ap-proach is to estimate f gas and its uncertainties at a fixed radius(i.e., assuming that the true R is known), in which case theuncertainties on M and M gas are uncorrelated and directlypropagate onto f gas , which then yields f gas = . + . − . . Here, wetake the result using the beta-model as default.Hoekstra (2007) estimated the L X − M relation for agalaxy cluster sample of 20 X-ray luminous objects at interme-diate redshifts up to z ∼ .
6. They find a slope consistent withthe one from Pratt et al. (2009), which is also used in the red-shift evolution study of Reichert et al. (2011) and also consistentwith the (inverted) slope of Maughan (2007) who assumed self-similar evolution. Using the relation from Hoekstra (2007) andassuming 30% intrinsic scatter, we find M = (1 . + . − . ) × M (cid:12) for the background-subtraction method and M = (1 . + . − . ) × M (cid:12) for the background-modeling method and(using the corresponding R ) M gas , = (1 . + . − . ) × M (cid:12) and M gas , = (1 . + . − . ) × M (cid:12) , respectively. This yields f gas , = . ± .
02 for both background methods, and is invery good agreement with our previous findings using the weaklensing mass.
To estimate the cooling time, we further reduced the size of thecentral region to 0 . (cid:48) ∼
100 kpc and performedthe same PSF correction and deprojection method as describedabove. The cooling time is given by (Hudson et al. 2010) t cool = n e + n i ) k B T n e n H Λ ( T , Z ) , (5)where n i is the ion density and Λ ( T , Z ) the cooling func-tion. Within 100 kpc we find n e = (2 . + . − . ) × − cm − and T = . + . − . keV. This yields a short cooling time forCl J + t cool = . ± . t cool = . ± . . R with Chandra. According to their findings,Cl J + J +
4. Discussion and conclusions
Our results show that Cl J + z ∼ .
9. Compared to the total mass es-timate from Buddendiek et al. (2015) of M = (5 . ± . × h − M (cid:12) , we find a slightly lower value from our weak lens-ing analysis of M / M (cid:12) = . + . − . (stat . ) ± . . ), whichis, however, compatible within the uncertainties.As discussed in, e.g., Sanderson et al. (2009) and Semleret al. (2012) there is a tight correlation between the dynami-cal state of the cluster and the presence and strength of a coolcore. We find strong indications for the presence of a cool core,and the two di ff erent approaches for the background handlingyield similar results which gives us confidence in our treatmentof the background. The temperature profile shows a clear droptowards the center and the cooling time within 100 kpc is shortwith t cool = . ± . t cool = . ± . ff set between the BCG and the X-ray emission peak (see, e.g.,Rossetti et al. 2016, Mahdavi et al. 2013, Hudson et al. 2010).Rossetti et al. (2016) define a relaxed cluster by an o ff set smallerthan 0 . R . For Cl J + ff set is about 2 (cid:48)(cid:48) ( ∼
15 kpc) corresponding to 0 . R (using the BCG positiongiven in Buddendiek et al. 2015, see also Fig. 4), which is an-other indication for the relaxed nature of the system. Our HSTweak lensing study also shows that the mass reconstruction peakis compatible with the BCG position and the X-ray peak within1 σ . As investigated in Sec. 3.1, the apparent elliptical shape ofthe lensing mass reconstruction is not significant. Hence, the re-sults are consistent with a round mass distribution.In a bottom-up scenario for structure formation, massivecool core systems should be extremely rare at high redshifts.Their gas mass fractions should not depend on the cosmolog-ical model. However, the apparent evolution varies for di ff er-ent assumed cosmologies. Previous measurements from Allenet al. (2008) and Mantz et al. (2014) show that their data are ingood agreement with the standard cosmological model, showinga flat behavior of f gas with redshift. However, these data onlycontain a few objects at very high redshifts. Therefore, clusterslike Cl J + f gas , = . + . − . , whichis consistent with the result from Allen et al. (2008) for their fullcluster sample and also consistent with the assumed Λ CDM cos-mology ( Ω m = . h = . L X − M scaling relation for the total mass and testedthe assumption of constant density in each shell, to verify this re-sult and find very good agreement. Mantz et al. (2014) measuredthe gas mass fraction in an annulus from 0 . R < R < . R
8. Th¨olken et al.: XMM-Newton X-ray and HST weak gravitational lensing study of Cl J + z = . excluding the core of the clusters to minimize gas depletion un-certainties and intrinsic scatter in the inner part. They find typical f gas values between 0 . − .
12 and are thus consistent with ourfindings and Allen et al. (2008).Reichert et al. (2011) studied the evolution of cluster scal-ing relations up to redshift 1 .
5. They use the relations from Prattet al. (2009) for the local clusters and obtain a bias-correctedevolution factor. Testing this L X − T scaling relation with our es-timated global gas temperature yields a luminosity that is about40% smaller than our measured value. This result is, at least par-tially, expected due to the presence of a cool core. However, theuncertainties solely due to the uncertainties of the slope and nor-malization of the scaling relation (assuming they are uncorre-lated) are already large ( (cid:38) J + . Acknowledgements.
This work is based on joint observations made with theNASA / ESA
Hubble Space Telescope , using imaging data from program 13493(PI: Schrabback) and XMM-Newton data (IDs 0722530101 and 0722530201),as well as WHT data (ID W14AN004, PI: Hoekstra). ST and TS acknowl-edge support from the German Federal Ministry of Economics and Technology(BMWi) provided through DLR under projects 50 OR 1210, 50 OR 1308, 50OR 1407, and 50 OR 1610. ST and THR acknowledge support by the GermanResearch Association (DFG) through grant RE 1462 / References
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