A&A586,A122(2016) Astronomy DOI:10.1051/0004-6361/201527616 & (cid:13)c ESO2016 Astrophysics High angular resolution Sunyaev-Zel’dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis R.Adam1,2,B.Comis1,I.Bartalucci3,A.Adane4,P.Ade5,P.André3,M.Arnaud3,A.Beelen6,B.Belier7,A.Benoît8, A.Bideaud5,N.Billot9,O.Bourrion1,M.Calvo8,A.Catalano1,G.Coiffard4,A.D’Addabbo8,10,F.-X.Désert11, S.Doyle5,J.Goupy8,B.Hasnoun6,I.Hermelo9,C.Kramer9,G.Lagache12,S.Leclercq4,J.-F.Macías-Pérez1, J.Martino6,P.Mauskopf5,13,F.Mayet1,A.Monfardini8,F.Pajot6,E.Pascale5,L.Perotto1,E.Pointecouteau14,15, N.Ponthieu11,G.W.Pratt3,V.Revéret3,A.Ritacco1,L.Rodriguez3,G.Savini16,K.Schuster4,A.Sievers9, S.Triqueneaux8,C.Tucker5,andR.Zylka4 1 Laboratoire de Physique Subatomique et de Cosmologie, Université Grenoble-Alpes, CNRS/IN2P3, 53 rue des Martyrs, 38000Grenoble,France e-mail:[email protected] 2 LaboratoireLagrange,UniversitéCôted’Azur,ObservatoiredelaCôted’Azur,CNRS,Blvddel’Observatoire,CS34229, 06304NiceCedex4,France 3 LaboratoireAIM,CEA/IRFU,CNRS/INSU,UniversitéParisDiderot,CEA-Saclay,91191Gif-Sur-Yvette,France 4 InstitutdeRadioAstronomieMillimétrique(IRAM),38400Saint-Martind’HèresGrenoble,France 5 AstronomyInstrumentationGroup,UniversityofCardiff,CardiffCF103XQ,UK 6 Institutd’AstrophysiqueSpatiale(IAS),CNRSandUniversitéParisSud,91440Bures-sur-Yvettes,France 7 Institutd’ÉlectroniqueFondamentale(IEF),UniversitéParis-Sud,91400Orsay,France 8 InstitutNéel,CNRSandUniversitédeGrenoble,France 9 InstitutdeRadioAstronomieMillimétrique(IRAM),18012Granada,Spain 10 DipartimentodiFisica,SapienzaUniversitàdiRoma,PiazzaleAldoMoro5,00185Roma,Italy 11 InstitutdePlanétologieetd’AstrophysiquedeGrenoble(IPAG),CNRSandUniversitédeGrenoble,France 12 Aix-MarseilleUniversité,CNRS,LAM(Laboratoired’AstrophysiquedeMarseille)UMR7326,13388Marseille,France 13 SchoolofEarthandSpaceExplorationandDepartmentofPhysics,ArizonaStateUniversity,Tempe,AZ85287,USA 14 UniversitédeToulouse,UPS-OMP,InstitutdeRechercheenAstrophysiqueetPlanétologie(IRAP),31062Toulouse,France 15 CNRS,IRAP,9Av.colonelRoche,BP44346,31028ToulouseCedex4,France 16 UniversityCollegeLondon,DepartmentofPhysicsandAstronomy,GowerStreet,LondonWC1E6BT,UK Received22October2015/Accepted16December2015 ABSTRACT TheprototypeoftheNIKA2camera,NIKA,isadual-bandinstrumentoperatingattheIRAM30-mtelescope,whichcanobserve theskysimultaneouslyat150and260GHz.OneofthemaingoalsofNIKA(andNIKA2)istomeasurethepressuredistributionin galaxyclustersathighangularresolutionusingthethermalSunyaev-Zel’dovich(tSZ)effect.Suchobservationshavealreadyproved tobeanexcellentprobeofclusterpressuredistributionsevenatintermediateandhighredshifts.However,animportantfractionof clusters host sub-millimeter and/or radio point sources, which can significantly affect the reconstructed signal. Here we report on <20arcsecangularresolutionobservationsat150and260GHzoftheclusterMACSJ1423.8+2404,whichhostsbothradioandsub- millimeterpointsources.WeexaminethemorphologicaldistributionofthetSZsignalandcompareittootherdatasets.TheNIKA data are combined with Herschel satellite data to study the spectral energy distribution (SED) of the sub-millimeter point source contaminants.Wethenperformajointreconstructionoftheintraclustermedium(ICM)electronicpressureanddensitybycombining NIKA,Planck,XMM-Newton,andChandradata,focusingontheimpactoftheradioandsub-millimetersourcesonthereconstructed pressureprofile.Wefindthatlarge-scalepressuredistributionisunaffectedbythepointsourcesbecauseoftheresolvednatureof theNIKAobservations.Thereconstructedpressureintheinnerregionisslightlyhigherwhenthecontributionofpointsourcesare removed.Weshowthatitisnotpossibletosetstrongconstraintsonthecentralpressuredistributionwithoutaccuratelyremovingthese contaminants.ThecomparisonwithX-rayonlydatashowsgoodagreementforthepressure,temperature,andentropyprofiles,which allindicatethatMACSJ1423.8+2404isadynamicallyrelaxedcoolcoresystem.Thepresentobservationsillustratethepossibilityof measuringthesequantitieswitharelativelysmallintegrationtime,evenathighredshiftandwithoutX-rayspectroscopy.Thiswork ispartofapilotstudyaimingatoptimizingtSZobservationswiththefutureNIKA2camera. Keywords.techniques:highangularresolution–galaxies:clusters:individual:MACSJ1423.8+2404– galaxies:clusters:intraclustermedium 1. Introduction to both the matter content of the Universe and its dynamics because they form throughout its expansion history. Their for- Inthestandardscenarioofstructureformation,clustersofgalax- mation process is well understood and clusters have been used iesformthroughthehierarchicalmergingofsmallergroupsand to place constraints on cosmological parameters (e.g., Planck accretion of surrounding material. These clusters are sensitive Collaboration XXIX 2014). However, the complex baryonic ArticlepublishedbyEDPSciences A122,page1of16 A&A586,A122(2016) physics occurring during cluster formation, such as feedback observestheskyat150and260GHzwithanangularresolution from active galactic nuclei (AGN), or nonthermal processes of 18 and 12 arcsec full width at half maximum (FWHM), and occurring during mergers or in the presence of intracluster hasalreadybeenusedtoimagethetSZeffecttowardthegalaxy medium (ICM) turbulence or coherent motion, is still unclear clusters RXJ1347.5-1145 and CLJ1226.9+3332 (see Adam (seeforexampleBorgani&Kravtsov2011).Thisleadstoscat- et al. 2014, 2015). In the present paper we discuss observa- terandbiasesintheobservable–massscalingrelationsneededto tions of the intermediate redshift cluster MACSJ1423.8+2404 compare to theory, limiting the use of clusters as cosmological at z = 0.545, which contains both radio and sub-millimeter probes. galaxiesandwhichwehaveusedasatestcasetoinvestigatethe The thermal Sunyaev-Zel’dovich effect (tSZ; Sunyaev & impact of such contaminating objects on the reconstruction of Zel’dovich 1972, 1980) is produced by the inverse Compton thepressureofclustersobservedwithNIKA2. interaction of cosmic microwave background (CMB) photons with the energetic electrons in the ICM. This tSZ effect leads MACSJ1423.8+2404 is a massive cluster from the toaspectraldistortionoftheCMBobservableatmillimeterand MACS catalog (Massive Cluster Survey; Ebeling et al. 2001), sub-millimeter wavelengths that is directly proportional to the forwhichawealthofmultiwavelengthdatahavebeenobtained. line-of-sight integral of the electronic pressure distribution in Schmidt & Allen (2007), in a study of relaxed clusters with the ICM. The integrated tSZ flux is related to the overall ther- Chandra, reported a virial mass M = 4.52+0.79 × 1014 M , malenergyoftheclusterandisthereforeexpectedtoprovidea vir −0.64 (cid:12) indicatingthatitindeedisamassiveobject.Theclusterwasob- lowscattermassproxywithasmalldependenceonthedynam- served by the BIMA interferometer (LaRoque et al. 2003) and ical state of the cluster or the exact gas physics (e.g., da Silva by the Sunyaev-Zel’dovich Array (SZA), as part of a sample etal.2004;Motletal.2005;Nagai2006).Furthermore,resolved used to constrain the cluster pressure profile (Bonamente et al. tSZobservationsareverysensitivetotheoverpressurecausedby mergersandhaveprovedtobeveryefficientforprobingcluster 2012). The large-scale structure of MACSJ1423.8+2404 was investigated, using its red sequence galaxy density distribution astrophysics (see, for example, results by Pointecouteau et al. (Kartaltepe et al. 2008), showing a very relaxed morphology. 1999; Komatsu et al. 2001; Korngut et al. 2011; Adam et al. Guennou et al. (2014) studied the structure of the cluster using 2014,2015;Youngetal.2015;Mroczkowskietal.2015).This ChandraX-raydataaspartofthedarkenergyAmericanFrench is particularly true at high redshifts since, unlike other probes, the tSZ signal does not suffer from cosmological dimming and team survey. They observed a strong X-ray emission, slightly elongated, and only low significance substructures were found. is only limited by the sensitivity and angular resolution of the observations. Detailed reviews of the tSZ effect can be found Themorphologyoftheclusterwasalsostudiedfromadetailed gravitationallensing/opticalanalysisbyLimousinetal.(2010), in Birkinshaw (1999), Carlstrom et al. (2002), and Kitayama whonoticedthatMACSJ1423.8+2404isnearlyfullyvirialized, (2014). elongated,andshowsverylittlesubstructure(seealsothestrong During the past few years, tremendous achievements have lensing results by Zitrin et al. 2011, as part of a sample of 12 been made in the tSZ community with the production of MACS clusters). The temperature profile obtained by Morandi catalogues of more than 1000 objects by Planck (Planck etal.(2010)usingChandradatashowsatypicalcoolcoreform CollaborationXXIX2014),theAtacamaCosmologyTelescope withalowcentraltemperature(∼3keV)andapeakat∼7keVat (ACT; Hasselfield et al. 2013), and the South Pole Telescope about300kpcawayformthecenter.Thebrightestclustergalaxy (SPT; Reichardt et al. 2013; Bleem et al. 2015), at >1 arcmin (BCG) hosts a central AGN that is visible as a point source in angular resolution. X-ray observations have shown that, when radio observations (Condon et al. 1998; LaRoque et al. 2003; scaled to a characteristic radius, the cluster pressure profile Cobleetal.2007;Bonamenteetal.2012).ThisAGNisrespon- shows a low dispersion (Arnaud et al. 2010). This profile has sible for the presence of two cavities detected in the Chandra now been well measured at intermediate scales in the nearby X-ray image (Hlavacek-Larrondo et al. 2012). Another radio Universe with tSZ observations (Plagge et al. 2010; Planck source is located at about 1.5 arcmin southwest with respect to Collaboration V 2013c; Sayers et al. 2013a), but has not been the X-ray peak. Cluster members, foreground, and background deeplyexploredathighredshiftandintheclustercoresbecause (including lensed sources) sub-millimeter galaxies are detected ofthelackofhighangularresolutionobservations.Theinvesti- by Herschel, as observed during the Herschel Lensing Survey gationofthisprofileisnonethelessnecessarytomakebetteruse (HLS;Egamietal.2010;Rawleetal.2012). oftheavailabletSZclustersampleswhenrelatingthetSZsignal toclustermass. In the context of high angular resolution tSZ observations, This paper is organized as follows. The observations per- oneofthemainchallengestofaceistheremovalofthecontam- formed at the IRAM 30-m telescope are briefly presented in ination from point sources, as needed for example in the case Sect. 2. In Sect. 3, we discuss the processing of radio and sub- of Bolocam observations (Sayers et al. 2013b). Indeed, galaxy millimeterpointsourcesandtheirimpactontheradialtSZflux clusterscontaingalaxiesthatcanhostradiosourcesorasignifi- density profile. The data reduction of the XMM-Newton and cantamountofdust.Inaddition,clustersatintermediateredshift Chandra X-ray observations is presented in Sect. 4. We com- provideoptimallenses,whichcanmagnifysub-millimeterback- pare the NIKA observations to other multiwavelength datasets groundgalaxies(see,e.g.,Adametal.2015).Foregroundgalax- in Sect. 5. In Sect. 6, we reconstruct the radial pressure dis- iescanalsobelocatedinprojectionneartheclusterunderstudy. tribution of MACSJ1423.8+2404 and explore the impact of IntSZobservations,theseobjectsappearaspoint-likecontami- the presence of the point sources. The pressure profile is com- natingsources.TheNewIRAMKidsArray(NIKA)isthepro- bined with the electronic density of X-ray data to derive the totypeofNIKA2,thenextgenerationcontinuuminstrumentfor thermodynamic distribution of the ICM. Conclusions and per- the Institut de Radio Astronomie Millimétrique (IRAM) 30-m spectives for NIKA2 are provided in Sect. 7. Throughout this telescopenearGranada,Spain(seeMonfardinietal.2010,2011; paper we assume a flat ΛCDM cosmology, according to the Bourrion et al. 2011, 2012; Calvo et al. 2013; Catalano et al. latest Planck results (Planck Collaboration XIII 2015), with 2014,formoredetailsontheNIKAcamera).TheNIKAcamera H0 =67.8kms−1Mpc−1,ΩM =0.308,andΩΛ =0.692. A122,page2of16 R.Adametal.:ResolvedtSZobservationsofMACSJ1423.8+2404 2. ObservationsattheIRAM30-mtelescope to unity at scales that are smaller than the field of view. The withNIKA transferfunctionvanishessmoothlyatlargerangularscales(see Adametal.2015). 2.1. ThethermalSunyaev-Zel’dovicheffect The tSZ effect (Sunyaev & Zel’dovich 1972, 1980) results in a 2.3. RawNIKAobservations distortion of the CMB blackbody spectrum relative to the pri- maryCMBintensity,I ,(e.g.,Birkinshaw1999) The NIKA maps that we obtained are presented in Fig. 1. 0 The 150 GHz map reveals a negative decrement, as expected ∆ItSZ =y f(ν,T ). (1) from the tSZ effect at this frequency, with a maximum signif- I e icance of 4.5σ. The morphology of the signal has a ring-like 0 shape,asaconsequenceofthecontaminationbytheradiopoint The function f(ν,T ) gives the characteristic frequency depen- e source at the cluster center, which fills in the tSZ signal. The denceofthespectrum.Thesmalldependanceontheelectronic 260GHzmapdoesnotshowanysignificanttSZsignal.Atthis temperature,T ,arisesfromrelativisticcorrectionsforwhichwe e frequency, extrapolating from the 150 GHz map, we expect a usetheresultsofItohetal.(1998).TheComptonparameter,y, peak of ∼1 mJy/beam, which is below the level of the noise givestheamplitudeofthedistortionandisrelatedtotheline-of- standarddeviation.Weobservea3σpositivepeakaround(RA, sightintegraloftheelectronicpressure,P ,as e Dec)=(14:23:53,+24:03:45),whichcorrespondstoa2σpos- (cid:90) σ itive peak in the 150 GHz map owing to the presence of a y= T P dl. (2) m c2 e sub-millimeter source. Another peak is also seen around (RA, e Dec) = (+14:23:48, +24:04:15). The radio and sub-millimeter TheparameterσT istheThomsoncrosssection,me istheelec- pointsourcecontaminationisdiscussedindetailinSect.3. tron rest mass, and c the speed of light. The total integrated The significance of the NIKA maps was calculated using tSZ flux, Ytot, is then given by the aperture photometry per- MonteCarlorealizations.First,anoisemapwasobtainedfrom formedontheComptonparametermap. the half difference of two equivalent subsets. After having nor- In the NIKA bands, the tSZ signal is expected to be faint malized the noise map by the integration time per pixel, the (y∼10−4fortypicalmassiveclusters)anddiffuse.Itisnegative noise spectral distribution was computed with the POKER soft- at150GHzandpositiveat260GHz. ware (Ponthieu et al. 2011), which properly accounts for in- complete sky coverage due to the scanning around the cluster. The noise power spectrum was modeled as a function of angu- 2.2. Observingconditions,scanningstrategy,calibration, anddatareduction lar scale k, as P (k) = A +A (k )(cid:16)k(cid:17)β. The parameter noise white cor 0 k0 MACSJ1423.8+2404wasobservedduringthefirstNIKAopen Awhite representstheintrinsicdetectornoiseand Acor andβgive theamplitudeandtheslopeoftheresidualdetector-detectorat- pool in February 2014. We collected 1.47 h of on-target data. mosphericcorrelationsinthemap.Thismodelwasusedtogen- The atmospheric conditions were stable and the mean opacity erateMonte-Carlonoisemaprealizations,n,accountingforthe wasmeasuredtobe0.14and0.15,atthesourcelocation,at150 i integrationtimeperpixel.Thenoiserealizationsweresmoothed and260GHz,respectively,asdetailedinCatalanoetal.(2014). bythesame10arcsecGaussianfilterusedtodisplaythecluster, Themeanelevationofthesourcewas30.8deg. and the standard deviation across the Monte-Carlo realizations The scanning strategy adopted was the same as that used for CLJ1226.9+3332, detailed in Adam et al. (2015). Briefly, allowedustocomputetherootmeansquaremapand,therefore, the signal-to-noise contours shown in Fig. 1. The noise stan- eachscanconsisted19subscansof6arcminlengthseparatedby dard deviation on the flux of point sources at the center of the 10 arcsec steps made alternately at constant azimuth and con- mapis0.8and2.9mJyat150and260GHz,accountingforre- stantelevation(relativetothemapcenter).Thepointingcenter waschosentobeat(RA,Dec2000)=(14:23:47.8,+24:04:40.0) duction filtering effects. The mean noise standard deviation of the displayed maps within a radius of 60 arcsec, after apply- basedontheArchiveofChandraClusterEntropyProfileTables ing the Gaussian smoothing, is 0.39 and 1.3 mJy/beam at 150 catalog(ACCEPT;Cavagnoloetal.2009). and260GHz,respectively.Thefullnoisecovariancematrixwas The detailed calibration procedure can be found in Adam also computed as the mean of the noise covariance over all the et al. (2015) and we only summarize the main results here. realizations,C = 1 (cid:80)NMCnnT,anditisusedintheanalysisas Uranuswasusedastheprimarycalibrator.TheGaussianbeam NMC i=1 i i FWHM was measured to be 18.2 and 12.0 arcsec at 150 and describedinSect.6. 260 GHz, respectively. The nearby quasar 1354+195 was used to correct the pointing, for which the error is estimated to be 2.4. Astrophysicalcontaminants less than 3 arcsec. The overall calibration uncertainty was es- timated to be 7% at 150 GHz and 12% at 260 GHz. The Inadditiontotheinstrumentnoiseandatmosphericnoiseresid- NIKAbandpasseswereusedtoconvertthefluxsurfacebright- uals, diffuse astrophysical emission may give rise to an extra ness to Compton parameter. We obtained −10.9 ± 0.8 and sourceofnoisethatcannotbereducedbyincreasingtheobserv- 3.5 ± 0.5 Jy/beam per unit of Compton parameter at 150 and ingtime.Inthefollowing,weconsiderthecontaminationfrom 260 GHz, respectively. The effective number of detectors was CMB and cosmic infrared background (CIB) anisotropies, and 117 at 150 GHz and 136 at 260 GHz, corresponding to an in- Galacticemissions(dust,synchrotron,andfree-free). stantaneousfieldofviewof1.9and1.8arcmin,respectively. The Galactic latitude of MACSJ1423.8+2404 is high The removal of the atmospheric and electronic correlated (68.99◦), implying low contamination of the cluster field by noise,consistingofthesubtractionofthecorrelatedsignalinthe Galacticemissions(PlanckCollaborationetal.2015b).Toesti- timelinesacrossthedetectorarrays,wasperformedasinAdam matethiscontamination,weusetheHEALPixsoftware(Górski et al. (2015). The resulting signal filtering was estimated using etal.2005)toextract60arcmin×60arcminpatches,centered simulations. The observed transfer function was flat and close on the cluster coordinates, of the nine Planck channel maps A122,page3of16 A&A586,A122(2016) Fig.1.NIKAmapsat150GHz(left)and260GHz(right)inunitsofsurfacebrightness.Thesignificanceisgivenbytheblackcontoursstarting at±2σwith1σspacing.Themapsaresmoothedwithanextra10arcsecGaussianfilterfordisplaypurposesandtheeffectivebeamFWHMis representedasawhitecircleinthebottomleftcornerofeachpanel.ThewhitecrossesindicatetheX-raycenter. at 30, 44, 70, 100, 143, 217, 353, 547, and 857 GHz (Planck about 5 with respect to the clustering component. Taking the Collaborationetal.2015a),towhichwesubtracttheCMBmap NIKA transfer function and beams into account, we obtain a (Planck Collaboration et al. 2015c). We find that CMB emis- standarddeviationofthefluctuationsof0.13and0.38mJy/beam sion dominates over the low frequency Galactic components, at 150 and 260 GHz in the NIKA bands. This extra source of i.e.,synchrotronandfree-free,atallfrequencies.TheCMBalso noise is therefore subdominant with respect to the instrument dominatesoverthethermaldustemission,athigherfrequencies, noise and atmospheric noise residual at both frequencies, con- up to 353 GHz, where the amplitude of the fluctuations of the tributingtoabout1%ofthenoisewhensummedquadratically; twoaresimilar.Intheconsideredfield,theCMBthereforedom- wedonotaccountforthecontributionofthisextranoisesource inatesoverthediffuseGalacticemissionsintheNIKAbandsat inthepresentpaper. the Planck angular resolution. This is be even more true at the smaller scales probed by NIKA as Galactic diffuse emissions havepowerspectrathatarestronglydecreasingwiththespatial scale(powerlawwithanindexofabout−2.5). 3. Radioandsub-millimeterpointsources To estimate the level of contamination arising from 3.1. Radiopointsources CMB fluctuations, we use the CAMB software (Lewis et al. 2000) to compute the CMB power spectrum with the lat- Very Large Array (VLA) data at 4.8 GHz were used estPlanckcosmologicalparameters(PlanckCollaborationXIII by LaRoque et al. (2003) to detect radio sources toward 2015) as input. The spectrum is computed up to multipole MACSJ1423.8+2404. Two sources were detected within the (cid:96) = 44000 (corresponding to the NIKA angular resolution) NIKA field and we used the coordinates obtained by LaRoque and serves to generate CMB realization via the POKER soft- et al. (2003) as a reference (see Sect. 5 and Fig. 4). The first ware (Ponthieu et al. 2011). The simulated CMB maps are source, hereafter RS1, is located within the central BCG, near produced on a 5 arcmin × 5 arcmin field and are convolved theX-raycenter.Thesecond,hereafterRS2,islocatedatabout with the NIKA transfer function including the beam smooth- 1.5arcmintowardthesouthwest.ThefluxofRS1wasmeasured ing.WefindthattheCMBfluctuationsareabout15×10−3 and at various radio wavelengths between 1.4 GHz and 30 GHz, 7×10−3mJy/beam,whichisnegligiblewithrespecttotheinstru- while the flux of RS2 was only measured at 1.4 and 4.8 GHz. mentnoiseandatmosphericnoiseresidualat150and260GHz, WelistinTable1thefluxesmeasuredforbothsourcesandthe respectively.Therefore,weneglecttheCMBfluctuationsandall correspondingreferences. theGalacticdiffuseemissionthatarethemselvesfainterthanthe To estimate the expected flux of each source in the CMBfluctuations. NIKA bands, we modeled their spectral energy distribution sourFciensalalyc,cowuentiensgtimfoartethteheclcuosntetrriibnugtioonf dfruosmty esxtatrr-afgoarlmacintigc (SED)byFν = F1GHz(cid:16)1GνHz(cid:17)αradio.ThefluxesreportedinTable1 galaxies (CIB clustered anisotropies) and the shot noise from wereusedtofittheamplitudeoftheSED,F ,anditsslope, 1GHz both dusty star-forming galaxies and radio sources. The clus- α . The best-fit parameters are reported in Table 2 for both radio tering from radio sources is negligible (Hall et al. 2010). The sources. We then simulated mock SEDs by sampling the pa- clusteringtermiscomputedusingtheCIBpowerspectrummea- rameters within their error bars and accounting for the covari- suredat143and217GHzbyPlanckCollaborationXXX(2014), ancebetweenthem.EachmockSEDwasthenintegratedwithin modeled by a 1-halo and a 2-halo term, and extrapolated to the NIKA bandpasses to predict the expected flux at 150 and theNIKAfrequencies.Theshotnoise,arisingfromunresolved 260GHz.Thehistogramofalltherealizationswasfittedwitha sourcesbelow theNIKAdetection threshold,iscomputed with Gaussianfunctiontogivetheexpectedfluxesanduncertainties, themodelfromBétherminetal.(2012)inthecaseofdustystar- whicharelistedforbothsourcesandbothNIKAfrequenciesin forming galaxies and Tucci et al. (2011) for radio sources. At Table 2. The values of the spectral index α we obtain are radio the considered scales, the shot noise dominates by a factor of typicalforradiosources(seeforexampleWitzeletal.1979). A122,page4of16 R.Adametal.:ResolvedtSZobservationsofMACSJ1423.8+2404 Table1. Locationandfluxoftheradiosourcesobservedinthe4×4arcmin2fieldaroundMACSJ1423.8+2404. Source Identifier Position 1.4GHz 4.8GHz 28.5GHz 30GHz [mJy] [mJy] [mJy] [mJy] RS1 NVSSJ142347+240439 14:23:47.78+24:04:42.8a 8.0±1.1b 4.40±0.03a 1.49±0.12c 2.0±0.2d RS2 NVSSJ142345+240340 14:23:45.07+24:03:42.7a 7.2±0.5b 2.72±0.03a – – References.(a)VLA;LaRoqueetal.(2003).bNVSS;Condonetal.(1998).(c)OVRO/BIMA;Cobleetal.(2007).dSZA;Bonamenteetal.(2012). Table 2. Best-fit parameters and extrapolation of the fluxes in the NIKA bands of the radio sources in the 4 × 4 arcmin2 field around MACSJ1423.8+2404. Source RAoffset Decoffset(arcsec) F α 150GHz 260GHz 1GHz radio [arcsec] [arcsec] [mJy] [mJy] [mJy] RS1 0.3 2.6 10.39±0.30 −0.548±0.001 0.68±0.08 0.54±0.07 RS2 41.0 −57.3 9.39±0.69 −0.790±0.003 0.18±0.04 0.13±0.03 Notes.Thedegeneracybetweentheslopeα andtheamplitudeF hasbeenaccountedfortoextrapolatethefluxintheNIKAbands.See radio 1GHz textfordetails. 3.2. Sub-millimeterpointsources The positions and fluxes for all the sources are listed in Table3. WemakeuseoftheHerschelSpectralandPhotometricImaging Receiver(SPIRE;Griffinetal.2010)andPhotoconductorArray Similarly, the fluxes of the sub-millimeter sources in the NIKAfieldwereobtainedbyfittingtheamplitudeofaGaussian Camera and Spectrometer (PACS; Poglitsch et al. 2010) data model, using the NIKA FWHM at the source positions ex- obtained during the Herschel Lensing Survey (HLS, Egami etal.2010;Rawleetal.2012)1 toidentifysub-millimeterpoint pected from Herschel data. These were then corrected for the filtering induced by the data reduction (∼15 percent for point sources and compute their expected spectral energy distribu- sources). Uncertainties were obtained from the standard de- tion(SED)asseenbyNIKA,asdescribedbelow.TheHerschel viation of the amplitudes recovered using Gaussian fits per- data complement those from NIKA, both in terms of wave- formed on the Monte-Carlo noise map realizations. The fluxes length500,350,250,160,and100µm,andangularresolution, FWHM =35.2,23.9,17.6,9.9,6.1arcsec,respectively. obtained and their uncertainties are summarized together with the Herschel data in columns of Table 3. By stacking the flux The PACS maps were produced using the maximum like- of all the sources, assuming that they are independent, we ob- lihood map maker MADmap (Cantalupo et al. 2010), pro- tainedanaveragefluxof1.96±0.82mJyat260GHz(1.15mm) vided as a PACS Photometer Level 2.5 Product. We used and 0.46±,0.25 mJy at 150 GHz (2.05 mm), corresponding the Herschel Source List Product, generated with the soft- to a mean detection of 2.4 and 1.9σ, respectively. If we ex- ware SUSSEXtractor (Savage & Oliver 2007), which con- clude the two sources directly detected at the map level, the tains the location and flux of the sources found around MACSJ1424.8+2404.Thesourcesareextractedindependently detection reduces to 1.59 ± 0.89 mJy at 260 GHz (1.8σ) and 0.45 ± 0.25mJy(1.8σ)at150GHz. for each frequency band, with a signal-to-noise threshold of 5. The 250 µm channel is the most complete with 15 sources de- Only SMG02 and SMG06 are directly detected in the tectedinthe4×4arcmin2 aroundthecluster,andweusedthis NIKA maps. To better constrain the fluxes in the NIKA bands, 250µmchannelasabaselinetodefinethesourcepositionsand we modeled the SED with a modified blackbody spectrum, labels. The corresponding sources in the other channels were F = A (cid:16)ν(cid:17)βdust B (T ),whereA isanormalization,ν aref- matched to the 250 µm ones on the basis of their positions. ν 0 ν0 ν dust 0 0 erencefrequency,β thedustspectralindex,andT thedust Two sources peaking at high frequency were not present in the dust dust temperature. We noticed a flux excess at 100 µm for most of 250 µm catalog and we relied on the 100 µm channel for their thesourceswithrespecttothebest-fitSEDderivedfromallthe properties.ByusingalltheHerschelfrequencybands,wethere- other channels, which we attribute to the modified blackbody fore found a total of 17 sub-millimeter sources, two of which spectrum being too simplistic a description of the data at high correspond to the excesses seen in the NIKA 260 GHz map. frequency.Wethereforeexcludedthisfrequencyforconstraining Becauseoftherelativelylowresolutionat500and350µm,afew theSEDinthefollowing.Sinceweaimtosubtractthesourcesat sourcesareconfusedwiththeirneighborsand,ingeneral,notall 150GHz,wealsoexcludedtheNIKAmeasurementatthisfre- thesourcesareidentifiableinallthefrequencybandsinthecat- quencyandonlycheckedthatpredictedandmeasuredfluxesare alog. To obtain the fluxes of all sources in all bands, we fit the consistent. For the SMG02 and SMG05 sources, the 150 GHz amplitudeofaGaussianfunctiontoeachmapwiththeposition datawerenotextractedbecauseofstrongcontaminationbythe fixed at the source reference location and the FWHM fixed to localtSZsignal.Atlargerradii,thefaint,slowlyvaryingtSZsig- thatoftherespectiveHerschelchannels.Alocalbackgroundwas nalisaccountedforbecausewealsofitforalocalbackground. also fit. In order to account for the confusion in the flux uncer- The tSZ impact on the fluxes of the other sources is therefore tainties,wefitthesameGaussianfunctionatrandompositions, neglected and a bias is only expected in the case of significant where the noise is homogeneous, and use the dispersion as the tSZsignalatscalescomparabletothebeam. uncertainty. We checked that the sources present in the catalog WeperformedaMarkovchainMonteCarlo(MCMC)anal- have compatible fluxes with respect to those we recovered. ysis to fit simultaneously for β and T . This approach dust dust 1 Obs-IDs1342188159,1342188215and1342188216. allows us to sample the corresponding parameter space and A122,page5of16 A&A586,A122(2016) Table3.Positionsandfluxesofthe17sub-millimetersourcesidentifiedinthe4×4arcmin2 fieldaroundMACSJ1423.8+2404,measuredby fittingGaussianmodelstothemapsateachwavelengthasdescribedinSect.3.2. Source 250µmsourceposition 100µm 160µm 250µm 350µm 500µm 1.15mm 2.05mm [mJy] [mJy] [mJy] [mJy] [mJy] [mJy] [mJy] SMG01 14:23:52.31+24:05:04.9 20.8±1.1 35.1±3.2 52.3±7.7 30.4±8.1 11.6±7.4 0.6±3.2 1.4±0.9 SMG02 14:23:48.16+24:04:20.0 12.4±1.4 21.0±3.1 35.8±9.8 24.1±7.4 16.3±7.2 4.8±2.9 ∗∗ SMG03 14:23:53.50+24:06:05.1 10.7±1.2 17.0±2.9 34.7±11.3 23.7±7.9 8.2±7.1 3.4±3.8 0.5±1.1 SMG04 14:23:42.42+24:04:38.8 11.5±1.4 17.7±3.0 29.1±10.8 21.3±8.0 4.4±7.5 2.6±3.2 0.4±0.9 SMG05 14:23:47.58+24:04:48.7 6.1±1.3 9.4±2.8 25.6±8.4 18.3±7.6 14.3±7.5 3.1±2.9 ∗∗ SMG06 14:23:53.32+24:03:48.5 2.9±1.4 8.5±3.1 20.6±9.6 14.9±8.0 1.8±7.7 8.2±3.4 1.0±0.9 SMG07 14:23:45.04+24:05:48.9 3.4±1.3 10.2±3.0 20.1±9.2 14.0±8.0 7.3±8.0 1.3±3.4 1.0±0.9 SMG08 14:23:49.16+24:02:46.1 −1.0±1.5 5.4±3.2 19.9±8.8 24.0±7.8 11.2±7.8 3.5±3.8 0.9±1.0 SMG09 14:23:43.27+24:02:50.2 2.4±1.3 5.8±3.3 12.6±8.6 13.8±7.7 19.4±7.8 2.5±4.1 −0.1±1.1 SMG10 14:23:44.55+24:03:18.4 −1.5±1.2 4.4±3.3 11.1±8.2 19.0±7.7 19.7±7.8 4.3±3.4 −0.2±0.9 SMG11 14:23:54.14+24:05:32.2 7.3±1.3 11.6±2.9 11.0±9.1 3.5±7.5 5.9±7.8 −1.6±3.7 0.3±1.0 SMG12 14:23:43.41+24:03:50.6 5.4±1.3 9.1±3.2 7.3±10.0 −1.9±7.6 −6.9±7.4 2.3±3.4 0.4±0.9 SMG13 14:23:50.13+24:06:17.4 11.7±1.3 8.9±3.1 6.4±7.5 −2.4±8.0 −10.5±7.7 −4.2±3.7 0.9±1.0 SMG14 14:23:47.36+24:05:49.6 3.9±1.3 5.5±2.9 7.9±8.6 10.9±7.8 4.7±7.4 0.3±3.2 −0.2±0.9 SMG15 14:23:40.95+24:05:08.7 2.4±1.3 3.1±3.3 6.6±9.1 6.8±8.2 8.2±7.4 −1.2±3.5 0.0±0.9 SMG16∗ 14:23:53.69+24:04:12.6 6.2±1.4 7.3±3.4 18.0±10.5 −4.0±7.7 −3.5±7.5 3.4±3.3 0.6±0.9 SMG17∗ 14:23:51.72+24:05:48.8 4.7±1.3 4.3±3.4 −14.6±9.7 −6.2±7.7 −7.4±7.4 −2.2±3.4 −0.1±0.9 Notes.ThefinaltwocolumnscorrespondtotheNIKAbands.(∗)Sourcesforwhichthepositionisestimatedbasedonthe100µmPACSchannel. (∗∗)FluxeswhicharenotavailableduetothetSZcontamination. Table4. OffsetwithrespecttotheX-raycenter,andfluxextrapolatedtotheNIKAchannelsforthe17sub-millimetersourcesidentifiedinthe 4×4arcmin2fieldaroundMACSJ1423.8+2404,obtainedfromtheSEDmodeldescribedinSect.3.2. Source RAoffset Decoffset 1.15mm/260GHz 2.05mm/150GHz [arcsec] [arcsec] [mJy] [mJy] SMG01 −61.8 24.9 1.52±0.64 0.30±0.19 SMG02 −5.0 −20.0 2.39±1.10 0.62±0.42 SMG03 −78.1 85.1 1.51±0.79 0.35±0.26 SMG04 73.7 −1.2 1.05±0.67 0.25±0.21 SMG05 3.0 8.7 2.01±0.97 0.50±0.34 SMG06 −75.5 −51.5 1.13±1.12 0.31±0.39 SMG07 37.8 68.9 0.60±0.57 0.15±0.17 SMG08 −18.6 −113.9 2.53±1.17 0.60±0.40 SMG09 62.1 −109.8 2.15±1.51 0.55±0.47 SMG10 44.5 −81.6 3.79±1.56 0.97±0.55 SMG11 −86.8 52.2 0.09±0.12 0.02±0.03 SMG12 60.1 −49.4 0.05±0.07 0.01±0.02 SMG13 −31.9 97.4 0.05±0.06 0.01±0.01 SMG14 6.1 69.6 0.14±0.23 0.03±0.06 SMG15 93.8 28.7 0.13±0.28 0.03±0.07 SMG16∗ −80.6 −27.4 0.08±0.11 0.02±0.03 SMG17∗ −53.6 68.8 0.03±0.04 0.01±0.01 Notes. Despite the large uncertainties, these values allow to us estimate the impact of the contaminating sources on the reconstructed cluster properties.(∗)Sourcesforwhichthepositionisestimatedbasedonthe100µmPACSchannel. to automatically marginalize over A , which is highly degen- EachofthemodelSEDspectrawasintegratedwithintheNIKA 0 erate with the two other parameters. The Metropolis-Hasting bandpasses with the distribution of fluxes giving the expected algorithmwasusedtosampletheparameterspace.Eachmodel valueanduncertainty.TheresultsaresummarizedinTable4.A tested against the data was defined by a value of β and T similarfittingprocedurewasdevelopedbySayersetal.(2013c) dust dust and the normalization was linearly fit to the data. For NIKA, with SPIRE data to remove a contaminating signal from unre- colorcorrectionsareexpectedtobenegligiblewithrespecttothe solved sources in Bolocam data. Our analysis also includes the calibrationandstatisticaluncertainties(∼1−2%).Inthecaseof PACS 160 µm and NIKA 260 GHz photometric values, which Herschel,weapplythecolorcorrectionsgiveninPoglitschetal. allows us to release the constraint on the slope parameter β in (2010) for PACS and those available in the online documenta- contrasttothebaselinevalueof1.7usedbySayersetal.(2013c). tion for SPIRE2. These coefficients were interpolated for each modelwiththevaluesofβ andT ,andprovideasmallcor- 3.3. Surfacebrightnessprofile dust dust rectiontotheHerschelfluxes(∼5−10%).Wefinallyobtaineda Figure 2 shows the flux density profiles at 150 and 260 GHz, setofmodelsdistributedwithrespecttotheposteriorlikelihood. whichisobtainedbyaveragingthesignalfromtheNIKAmaps 2 http://herschel.esac.esa.int/Docs/SPIRE/html/spire_ in Fig. 1 in radial bins around the X-ray center. Uncertainties om.html#x1-830005.2.6 were computed using the noise realizations described in A122,page6of16 R.Adametal.:ResolvedtSZobservationsofMACSJ1423.8+2404 Fig.2.Profilesat150GHz(left)and260GHz(right),inunitsofsurfacebrightness,oftherawmap(blackdots)andthecontributionexpected fromradioandsub-millimeterpointsources(greensolidline).Thegreendashedenvelopegivesthe68%confidenceintervalonthepointsource profile. Sect.2.3.Thefluxdensityprofilewascomputedforeachnoise surfacebrightnessisexpressedas realizationandthestandarddeviationofalltherealizationsper (cid:90) radial bin provided the associated error bars. This allows us to 1 S = n2Λ(T ,Z)dl, (3) accountforpixel–pixelnoisecorrelation.Wealsocomputedthe X 4π(1+z)4 e e profileexpectedfromthepointsourcesforeachNIKAbandby simulatingthecorrespondingmapsusingthepointsourcefluxes where Λ(T ,Z) is the cooling function, which depends on the e andpositionsgiveninTables2and4.Theprofilewasthencal- temperature and the ICM metallicity Z, and is roughly pro- culated as for the NIKA maps and the error given by the dis- portional to T1/2. While X-ray imaging is mainly sensitive to persionofMonteCarlorealizationsofthepointsourcemapsby e the electronic density, the gas temperature can be estimated randomlyvaryingtheirfluxeswithintheGaussianerrors. fromX-rayspectroscopy.SeeforexampleBöhringer&Werner The 150 GHz profile decreases smoothly toward the center (2010)forareview. asaresultofthetSZsignal,exceptintheinner15arcsec,where itrises.Thisisconsistentwiththepositivesignalexpectedfrom the presence of radio and sub-millimeter emission from point- 4.1. Datapreparation like sources in the cluster core. Outside the core, the cluster is MACSJ1423.8+2404 was observed by the Chandra Advanced detected,attheprofilelevel,upto60arcsecradius. CCD Imaging Spectrometer (ACIS) for 115ks (obs-ID 4195) The sub-millimeter sources shown in Fig. 4 are located in and by the XMM-Newton European Photon Imaging Camera two distinct regions. Two of them are within 30 arcsec from (EPIC)for109ksintotal(obs-IDs720700301and720700401). theX-raypeak,whereweexpectthetSZcontributiontobethe XMM-Newton datasets were processed by applying the latest strongest,whiletheothersareconcentratedinaringof70arcsec calibration files via the Science Analysis System (SAS) ver- inner radius and 130 arcsec outer radius. No source is seen sion 14.0.0 and the calibration files available in May 2015. around 50 arcsec from the cluster center. This source distribu- Chandra datasets were processed with the Chandra Interactive tionisreproduced,despitethelargeuncertaintiesinthe260GHz AnalysisofObservation(CIAO)softwaresuiteversion4.7and profile.Thereisanexcessnearthecenter,whichweattributeto calibration database version 4.6.5. We applied the very faint thesumoftSZandsub-millimetersources(oneofwhichisde- mode3filteringtotheChandradatasetstoreducecontamination tected with NIKA at the map level). A dip can be seen around fromthestationaryfluxofhighenergeticparticles.Werejected 1arcmin,andanotherexcessisseenaround100arcsecfromthe  eventsforwhichthekeyword is>4(forMOS1,2)and center, both due to the distribution of Herschel point sources. >13(forPN)forXMM-Newton. Overall, the NIKA 260 GHz profile is consistent with that ex- TheChandraandXMM-Newtondatasetswereanalyzedus- pectedfromtheobservedpointsourcedistribution.Adeficitof ing the same technique, so unless otherwise stated, the proce- sub-millimetersurfacebrightnesswasalsoobservedtowardfour dures described in the following were applied to both datasets. galaxyclustersbyZemcovetal.(2013)aftertheremovalofthe Toremovesolarsoftprotonflarecontamination,wefollowedthe detected sources. This phenomenon is due to the gravitational procedures described in Pratt et al. (2007) and in the Chandra lensingofthecosmicinfraredbackgroundemissioninducedby 4 for the XMM-Newton and Chandra datasets, re- theclusters,andmightcontributetothedistributionweobserve spectively,rejectingtimeintervalswherethecountrateexceeded towardMACSJ1423.8+2404. 3σwithrespecttothemeanvalue.Wefoundnoflarecontamina- tionintheChandradataset,thus,thefull115ksobservationwas used;fortheXMM-Newtondataset,theusefulexposuretimewas 4. XMM-Newton andChandra X-raydatareduction 3 http://cxc.cfa.harvard.edu/cal/Acis/Cal_prods/ X-ray observations of galaxy clusters are sensitive to both the vfbkgrnd/ electronic density and the temperature of the ICM. The X-ray 4 http://cxc.harvard.edu/contrib/maxim/acisbg/COOKBOOK A122,page7of16 A&A586,A122(2016) Fig.3.MultiwavelengthdatasetofMACSJ1423.8+2404.Theoriginofthedataisgivenontopofeachmap.Themapshavebeensmoothedand theirrangeadaptedforvisualizationpurposes.ThedisplayedPACSandSPIREmapshavebeenreprojectedtomatchtheNIKAmapgrids.The 10arcsecradiuscirclesshowthepointsourcelocationsinblack/whiteforsub-millimetersources(Table3)andmagentaforradiosources(Table1). 122ksforMOS1+MOS2and41ksforPN.Weranawaveletde- datasets from period D for Chandra, since the observation was tectionalgorithmwithathresholdof5σonexposurecorrected performedin2003.Wecomputedtheweightsfortheinstrumen- imagesinthe[0.7−7] keVand[0.3−2] keVbandsChandraand talbackgrounddatasetsbyapplyingthesamepointsourcemask- XMM-Newton,respectively,toidentifypointsources.Theresult- ing andfiltering proceduresas for theobservation datasets. We ing source lists were merged, inspected by eye, and used as a thensubtractedfromthesurfacebrightnessandtemperaturepro- masktoremovepointsourcecontributionsfromtheanalysis. filestheinstrumentalbackgroundevaluatedusingthesedatasets. The residual background component is composed of ther- mal Galactic emission (Snowden et al. 1995) and the blending 4.2. Vignettingcorrection ofunresolveddistantpointsources,knownasthecosmicX-ray background(Giacconietal.2001).Wedeterminedaregionfree To correct for vignetting, we followed the procedure described from cluster emission and subtracted the residual mean back- inArnaudetal.(2001),computingaweightforeachphoton,de- groundcountrateforthesurfacebrightnessprofileanalysis.For finedastheratiooftheeffectiveareaattheaimpointtothatatthe the spectroscopic analysis, we extracted the spectrum from the photonposition.Usingthesequantities,wecanperformimaging source-free region and fitted it with a multicomponent model andspectroscopicanalysisasifthedetectorhadaflatresponse composed of two absorbed MEKAL thermal components and equaltothatattheaimpoint.Theweightswerecomputedusing anabsorbedpowerlaw(fordetailsonthemodelused,seePratt theevigweightroutineforXMM-Newton;weusedtheproce- etal.2009).Whenperformingfurtherspectroscopicanalysiswe dure described in Bartalucci et al. (in prep.) for Chandra. We addedthebackgroundmodelasafixedcomponentwithanam- alsocomputedtheeffectiveexposuretimeforeachphoton,pro- plitudescaledbytheratiooftheareaoftheregionofinterestto ducingexposuremapsthattakebadpixelsandcolumnsintoac- thatofthesource-freebackgroundarea.TheX-rayspectrawere count.Theresponsefilesforweightsandspectroscopicanalysis extracted and analyzed in the [0.3−10] keV and [0.7−10] keV werecomputedwiththeappropriatetoolsinCIAO(mkarfand bandsforXMM-NewtonandChandra,respectively. mkacisrmf)andSAS(arfgenandrmfgen). 5. Multiwavelengthcomparison 4.3. Backgroundsubtraction Figure 3 presents a multiwavelength overview of The X-ray background is due to diffuse sky emission and MACS J1423.8+2404, including the  survey (Faint an instrumental component caused by the interaction of high Images of the Radio Sky at Twenty-Centimeters; Becker et al. energetic particles with telescope instruments. To estimate 1995) observations at 1.4 GHz that provided the radio point the instrumental component, we used datasets tailored to source locations. The two radio sources discussed in Sect. 3.2 isolate this component, namely  and 4 for are clearly visible on the map. The complementarity of the XMM-Newton and Chandra, respectively. To match the ob- Herschel and NIKA instruments is clear; the NIKA bands servation, these datasets were skycasted and normalized in complement the Herschel spectral coverage at lower frequen- the [10−12], [12−14] keV and in the [9.5−10.6] keV band cies. In addition, the angular resolution of the NIKA bands is for MOS1,2-PN and ACIS, respectively. We used background comparable to that of SPIRE at 250 µm and PACS at 160 µm, A122,page8of16 R.Adametal.:ResolvedtSZobservationsofMACSJ1423.8+2404 6. Radialthermodynamicalreconstruction 30.0 The radial physical properties of the ICM were reconstructed 06:00.0 using two approaches. The first, detailed in Sect. 6.1, uses the X-ray data alone. The electronic density and gas temperature are directly measured and serve to reconstruct all the other 30.0 quantities.Thisapproachstronglydependsonthespectroscopic temperature reconstruction. The second approach, detailed in deg) 24:05:00.0 Sect. 6.2, consists of jointly fitting the tSZ data and the depro- 0 ( jectedelectronicdensityextractedfromtheX-raydata.Thepri- 0 0 Dec. J2 30.0 manadryasqusauncthititehsearmeetthheordefodreeptehnedpsroesnsluyrewaenadkleyleocntroXn-ircadyenspsietcy-, troscopythroughelectronicdensityreconstruction.Thecompar- 04:00.0 isonofthetwoapproachesisgiveninSect.6.3. 30.0 6.1. X-rayradialthermodynamicprofiles NIKA 150 GHz NIKA/Hershel SMG 03:00.0 Chandra photon counts NVSS radio sources We need to determine the temperature and electronic density Zitrin et al. mass model HST f814W profiles to compute the X-ray electronic pressure and entropy 56.0 54.0 52.0 14:23:50.0 48.0 46.0 44.0 42.0 40.0 profiles. The electronic density profiles was computed by ap- R.A. J2000 (hr) plying the regularized deconvolution and deprojection tech- Fig.4. Composite multiwavelength overview image of nique described in Croston et al. (2006). We extracted the sur- MACSJ1423.8+2404. Blue image: NIKA 150 GHz map show- face brightness profile from concentric annuli centered on the ingthetSZsignal.Redimage:Chandraphotoncounts(Obs-ID04195) X-ray peak, (RA, Dec) = (14:23:47.9, +24:04:42.3), in the tracing the electronic density. White contours: Surface mass distribu- [0.3−2.5] keV and [0.7−2.5] keV bands from the three com- tion model obtained by Zitrin et al. (2011, 2015) on a linear scale. bined EPIC and ACIS cameras, respectively. After background Yellow circles: (Sub-)millimeter sources candidate locations obtained usingtheNIKA260GHzmap(solidline)andidentifiedusingHerschel subtraction,theprofileswererebinnedviaalogarithmicbinning (dashed-line).Cyancircle:Locationoftheradiopointsourcespresent factor of 1.05 to have a 3σ significance for each bin, and were inthefieldasobtainedfromVLA(LaRoqueetal.2003).Greenimage: point spread function (PSF) deconvolved using the analytical HubbleSpaceTelescopeimageusingtheF814Wfilterobtainedbythe modelofGhizzardi(2001)forXMM-Newton.ForChandra,we CLASH program (Postman et al. 2012) showing the location of the assumed that the PSF is negligible with respect to the width of galaxies. thebins. The deconvolved, deprojected surface brightness profiles wereconvertedtodensityusingaconversionfactordetermined from the projected temperature profile. This temperature pro- filewasdeterminedbyextractingspectrafromconcentricannuli allowingustobreaktheconfusioninthelowfrequencySPIRE centeredontheX-raypeak,andthewidthofeachannuluswas bands in the crowded cluster environment for sources that defined to have a signal-to-noise ratio of 30 after background are directly detected by NIKA. The Hubble Space Telescope subtraction. We measured the temperature in each bin by fit- (HST) data from the Cluster Lensing And Supernova survey ting the spectrum with an absorbed MEKAL model, where the with Hubble program (CLASH; Postman et al. 2012) show absorption was fixed to NH = 2.2×1020cm−3 (Kalberla et al. the galaxy distribution. The (smoothed) Chandra X-ray image 2005), the redshift to z = 0.545, adding the scaled sky back- tracesthegaselectronicdensityandisusedfurtherinSect.6. ground component discussed above. We fit with the paramet- ricmodeldescribedinVikhlininetal.(2006)tointerpolatethe Figure 4 shows a composite multiwavelength image of the temperatureprofileforeachsurfacebrightnessbin.Theemissiv- cluster. The figure includes the NIKA 150 GHz tSZ map, ityterm,ΛterminEq.(3),dependsweaklyontemperature,so the Chandra X-ray photon counts, the NIKA and Herschel thatthechangeweobtainonthedensityprofileusingChandra sub-millimeter galaxy locations, the NVSS radio source lo- temperature profile instead of XMM is less than 1% over the cations, and the HST image from CLASH. We also provide, entire radial range. The differences in temperature reconstruc- for visual comparison, the surface mass distribution model of tion between Chandra and XMM-Newton (e.g., Schellenberger MACSJ1423.8+2404 produced by Zitrin et al. (2011, 2015) et al. 2015) thus do not affect the electronic density. To depro- withtheCLASHdata.Theimageprovidesadetailedpictureof jectthetemperatureprofile,wemeasuredthespectroscopic-like theclustercomplementingthediscussionofSect.1.TheNIKA temperature(Mazzottaetal.2004)usingtheweightingscheme 150 GHz tSZ signal surrounds the cluster core. The hole seen implementedinVikhlinin(2006),wheretheobservedtempera- in the tSZ signal is coincident with the BCG and results from tureprofileismodeledastheweightedsumofconcentricplasma cancelingthetSZbytheradioandsub-millimetersignal,asdis- shellseachatadifferenttemperature.Asforthedensityprofiles, cussedinSect.3.TheX-raymorphologyisverypeakedandthe wetakethePSFeffectsforXMM-Newtonintoaccount. maximumoftheemissioncoincideswiththeBCG.Theelliptic- Finally, M , the cluster mass enclosed within R 5, was ityofthespatialmassdistributionisveryclearfromthestrong 500 500 calculated by iteration about the M −Y relation of Arnaud lensing map, and is also visible in the X-ray map but less sig- 500 X etal.(2010). nificant.TheellipticityisnotvisibleinthetSZmapbecauseof the limited signal-to-noise and the point source contamination. Thegalaxydistributiondoesnotshowanyparticulargroupthat 5 R istheradiuswithinwhichthemeanclusterdensityisequalto 500 wouldbethesignofamergingevent. 500timesthecriticaldensityoftheUniverseatthecluster’sredshift. A122,page9of16 A&A586,A122(2016) 6.2. ModelingoftheICMandjointtSZ/X-rayfittingprocedure procedure also marginalizes over nuisance parameters such as thezeroleveloftheNIKAmap,thecalibrationuncertainty,and To fit the tSZ and electronic density jointly, we modeled the the central point source flux and position when included in the ICM using the approach described in detail in Adam et al. fit.FulldetailscanbefoundinAdametal.(2015). (2015).AsseeninSect.5andasemphasizedbyMorandietal. Theconstraintsobtainedonthepressureandelectronicden- (2010),MACSJ1423.8+2404iselliptical.Nevertheless,weas- sityprofilesarealmostindependent.However,eachmodelcom- sumesphericalsymmetrybecausethisworkdoesnotfocusonits paredtothedataincludesrelativisticcorrectionscomputedusing geometry,butontheimpactofthepresenceofpointsourceson theradialtemperatureprofile,givenbytheratiooftheelectronic the pressure profile reconstruction. Moreover, the significance pressure and density profiles, for each radial shell of the ICM. oftheNIKA150GHztSZmapisnotsufficienttoconstrainany Thisessentiallyaffectstheconstraintonthepressureprofilebut asymmetry. theeffectisverysmallcomparedtotheuncertainties.Therefore, Theradialdistributionoftheclusterelectronicpressurewas the constraint on the electronic density profile is driven by the modeledbyagNFWprofile(Nagaietal.2007),describedby X-ray data and that on the pressure is largely driven by the P tSZ data. The Planck constraint on the overall tSZ flux is rel- Pe(r)= (cid:18) (cid:19)c(cid:18) 0(cid:18) (cid:19)a(cid:19)b−c· (4) atively weak because of the location of the cluster on the sky r 1+ r a andthenoiseinhomogeneity.However,Planck providesanup- rp rp perlimitthatallowstheMCMCproceduretoavoidmodelsthat divergeatlargescales,whereNIKAisnotsensitive.Planckand Theparameter P isanormalizationconstant;r isacharacter- 0 p NIKAarethereforehighlycomplementarytoconstrainthepres- isticradius;anda,b,andcsettheslopesatintermediate,large, sureprofilefromsmalltolargescales. and small radii, respectively. This model was chosen to allow thedescriptionoftheprofileatallscales.Theelectronicdensity was modeled by a Simplified Vikhlinin Model (Vikhlinin et al. 6.3. Results 2006), MACSJ1423.8+2404 is known to be a typical cool core (e.g., ne(r)=ne01+(cid:32)rrc(cid:33)2−3β/2(cid:34)1+(cid:32)rrs(cid:33)γ(cid:35)−(cid:15)/2γ· (5) Mf(aou,obnra,dnc)dfoir=etsua(lc1.h.220c21l2u03s),t,e5sr.os49wb0ye5,Au0sr.en7da7u3thd6e)e.ptrTeahsl.seu(r2Xe0-1pra0roy)fiaplsehopataobrnaamseceloitunenres:t provided by XMM-Newton is larger than that of Chandra, al- Theparametern isthecentraldensity,r isthecoreradius,and e0 c lowingustoprobetheclusterICMuptolargerradii.Wethere- βisrelatedtotheslopeoftheprofile.Thesecondtermallowsa foreusedtheXMM-Newtonresultsasareferenceandwecross- steepening of the profile at large scales. The parameter (cid:15) gives checkedourresultswiththeChandradata. thechangeintheslope,r theradiusatwhichthetransitionoc- s curs, and γ the width of the transition. In the following, we set γ = 3 since this value provides a good fit to all clusters con- 6.3.1. Impactofthepointsourcesatmillimeterwavelengths sidered in the analysis of Vikhlinin et al. (2006). All the other The impact of the point source contamination on the recon- parametersarevariedwhenfittedtothedata. structedpressureprofilewastestedbyconsideringthreedifferent With the pressure and the density in hand, we compute the temperatureprofileassumingtheidealgaslaw,k T (r) = Pe(r), cases: B e ne(r) andtheentropyprofileasK(r)= Pe(r) .Thetotalmass,assum- 1. The presence of point sources was ignored and we fit the ing hydrostatic equilibrium, enclonsee(rd)5/w3 ithin r is then given by parameters P0 and rp, keeping the slope parameters fixed to their baseline values. This case is referred to as model 1 (M1). M (r)=− r2 dPe(r), (6) 2. The point sources were subtracted assuming the fluxes of HSE µ m n (r)G dr Table 4 and we repeated the fit of model M1. This case is gas p e referredtoasmodel2(M2). wherempistheprotonmass,GisNewton’sconstant,andµgas = 3. Thepointsourcesweresubtractedassumingthefluxesgiven 0.61themeanmolecularweightofthegas. inTable4,butpossibleresidualsofthecentralsourceswere The parameter space was sampled using the MCMC ap- also fitted. In this case, we also released the constraints on proachdetailedinAdametal.(2015),jointlyfittingthe150GHz theinnerandouterslopeparameters,candb,whicharealso NIKAtSZmapandtheelectronicdensityprofilecomputedfrom fitted.Theintermediateslopeparameterawasheldfixedbe- the X-ray data. We added an additional constraint on the to- causeitisstronglydegeneratewiththecharacteristicradius tal tSZ flux of the cluster with the Planck Compton parame- r andtheouterslopeb.Thiscaseisreferredtoasmodel3 p ter map (Planck Collaboration XXII 2015e). The tSZ models (M3). were convolved with the effective transfer function of the ob- servations, including the beam smoothing and the large-scale ComparisonoftheoutputpressureprofilefrommodelsM1and filtering cutoff due to the removal of the atmospheric noise. M2(seeFig.5)allowsadirectestimationoftheimpactofpoint MACSJ1423.8+2404 is not present in the Planck catalogue of sources. The use of model M3 was motivated by the large un- tSZ sources (Planck Collaboration XXVII 2016), but we ob- certainties on the point source fluxes as shown in Table 4. As tained an upper limit on its flux by integrating the Compton discussed in Sect. 3.3 and shown in Fig. 2, the sources that are parameter map (Planck Collaboration XXII 2015e) using aper- intheouterregionoftheclusterdonotcontributesignificantly ture photometry. The error on the flux was computed by per- to the radial flux density. However, this is not the case for the forming the same measurement randomly around the cluster, centralsources,inparticular,forRS1andSMG05.Weexpecta where the noise is homogeneous. The flux was measured to be significantcorrelationbetweenthefluxofthesesourcesandthe YPlanck = (0.40±0.66)×10−3 arcmin2. The MCMC sampling pressure profile parameters related to the cluster core, such as tot A122,page10of16