Challenging the merger/ sloshing cold front paradigm : A2142 revisited by XMM

1. Challenging the merger/sloshingcold front paradigm:A2142 revisited by XMM Mariachiara Rossetti (Università degli Studi di Milano & IASF Milano) D. Eckert, S. De Grandi, S. Molendi, F. Gastaldello, S.Ghizzardi, E. Roediger, D. Farnsworth, S. Brown, L. Rudnick

2. A tale of twocoldfronts First cluster in which CF havebeendiscovered by Chandra (Markevitch et al. 2000): twosharpedges in the X-ray image, with a temperature jump Interpretedin the discoverypaperas the “remnantcores” of twomergingsubclusters • Butproblems with the galaxydistribution: • G2 isisolated with a large velocity in the l.o.s • G1 lagsbehind the gas Galaxy clusters as giant cosmic laboratories

3. A tale of twocoldfronts Resemblance of the X-ray image with the predictions of hydrodynamicalsimulations (Tittley & Henriksen2005, Ascasibar & Markevitch 2006) changed the interpretation to sloshing(Markevitch & Vikhlinin 2007, Owers et al 2009) Optical substructureanalysis by Owers et al 2011 suggeststwopossible candidate perturbers However: A2142 isnot a cool core cluster (K0=68 keV cm2) and morphologyiselliptical and elongated SE-NW direction Galaxy clusters as giant cosmic laboratories

4. A tale of twocoldfronts Remnantcores • Cometaryshape of the edges • Overallelongation in X-rays and in the optical in the SE-NW direction • Not a relaxed, cool core cluster • Problem with the opticaldistribution: where are the galaxiesassociated to the NW CF? Sloshing • Concentricedgesas in simulations • Optical subclusteridentifiedas candidate perturber, with orbitconsistent with the overallmorphology ✗Not a relaxed, cool core cluster, flatentropyprofile Whileusuallyshownastextbookexamples of coldfronts, A2142 challengesourcurrentinterpretation of the cold front feature. Weneed new observations! (Puzzlingobjects are interesting target) Galaxy clusters as giant cosmic laboratories

5. A2142 asseen by XMM-Newton Galaxy clusters as giant cosmic laboratories

6. A2142 asseen by ROSAT PSPC The SE featurewasnottotallyunexpected: wehadalreadynoticedit in ROSAT PSPC residualmaps and profiles (Eckert et al. in prep.) SE excessseenalso in Chandraresidualmaps (Owers et al 2011) Galaxy clusters as giant cosmic laboratories

7. A2142 asseen by ROSAT PSPC SE NW The discontinuityisseenalso in the SB profile in the SE. Fit with a brokenpower-law density model givesnIN/nOUT= 1.92±0.1, Rcut=986±10 kpc Galaxy clusters as giant cosmic laboratories

8. Nature of the SE discontinuity The temperature differenceisonlymarginallysignificant (1.8σ).Stillconsistent with the shock front? Using Rainkine-Hugoniotconditionwith ourmeasureddensityjump, we can predictkTOUT= 3.9 keV, rejectedat > 5 σ It’snot a shock! Itis a cold front Galaxy clusters as giant cosmic laboratories

9. Properties of the SE cold front No obvious dark matterhaloisassociated to the SE CF: no substructure in the galaxydistributionhere (Owers et al. 2011) or in the weaklensingmaps (Okabe & Umetsu 2008). Extreme slingshotphase? At 1 Mpc from the center, thisis the mostperipheralcold front unassociated to a galaxyconcentrationeverdetected in a galaxy cluster A SB discontinuityisdetected (with the quantitative criterion of Ghizzardi et al 2010) in narrowsectors for 70 degrees: the linear size of the front is1.2 Mpc. Itisevenharder to reconcilethis new featurewithinknowncold front scenarios. Galaxy clusters as giant cosmic laboratories

10. XMM-Newton residualmap Morphologicalsimilarity with predictionsfrom sloshingsimulationsbutat a muchlarger scale: “extreme” sloshingalong the line of sight? Roediger et al. 2010 Galaxy clusters as giant cosmic laboratories

11. Temperature and metal distribution Regions on the SB excess (bothat the center and to the SE) are COOLER with respect to regionsat the samedistance from the center Galaxy clusters as giant cosmic laboratories

12. Temperature and metal distribution Regions on the SB excess to the NW show the largest metal abundance in the cluster (Roediger et al. 2011, seealsoS.Ghizzardi’s talk) Regions on the SB excess to the SE do notfeature a significant metal abundanceexcess. Galaxy clusters as giant cosmic laboratories

13. A new giant radio halo The radio emission of A2142 (Giovannini & Feretti, 2000) hasbeen so far interpretedas a MINI RADIO HALO, due to its small size (500 kpc) Extended Mpc scale diffuse emissionfound with GBT @1.4 GHz (Farnsworth, Rudnick & Brown, in prep.) Galaxy clusters as giant cosmic laboratories

14. A tale of twothreecoldfronts Remnantcores • Cometaryshape of the edges • Overallelongation in X-rays and in the optical in the SE-NW direction • Not a relaxed, cool core cluster • Large scale thirdcoldfront at 1 Mpc from the center • Presence of a giant radio halo (associated to merger) • Problem with the opticaldistribution: where are the galaxiesassociated to the NW CF? • Where are the galaxiesassociated to the new feature? First examples of extremeslingshot? Sloshing • Concentricedgesas in simulations • Optical subclusteridentifiedas candidate perturber, with orbitconsistent with the overallmorphology • Residualmapsverysimilar to sloshingsimulationsseenalong the line of sight • Metal abundancemaps • Not a relaxed, cool core cluster, flatentropyprofile • Size of the thirdfeature and presence of a giant radio halo? First example of extremesloshing? Galaxy clusters as giant cosmic laboratories

15. A tale of two three cold fronts The puzzle isnotsolvedyet. But the new XMM-Newton observationhasalreadyprovided new pieces of information (thirdcold front, metal abundancemap), which are pointing to either new phenomenaeitherextremeversions of knownmechanisms. (Eckert et al. in prep, Rossetti et al. in prep., Farnsworth et al. in prep. ) • What do westillneed? • New observationsatdifferentwavelengths (radio, X-rays, optical) • New simulationfocusing on extremescenarios Galaxy clusters as giant cosmic laboratories