Probing the Outskirts of Strongly Merging Double Clusters

Transcription

1 Probing the Outskirts of Strongly Merging Double Clusters S. W. Randall - CfA E. Bulbul, R. Paterno-Mahler, C. Jones, W. Forman, E. Miller, S. Murray, C. Sarazin, E. Blanton

2 Probing the Outskirts of Strongly Merging Double Clusters S. W. Randall - CfA E. Bulbul, R. Paterno-Mahler, C. Jones, W. Forman, E. Miller, S. Murray, C. Sarazin, E. Blanton

3 Probing the Outskirts of Strongly Merging Double Clusters S. W. Randall - CfA E. Bulbul, R. Paterno-Mahler, C. Jones, W. Forman, E. Miller, S. Murray, C. Sarazin, E. Blanton

4 Probing the Outskirts of Strongly Merging Double Clusters S. W. Randall - CfA E. Bulbul, R. Paterno-Mahler, C. Jones, W. Forman, E. Miller, S. Murray, C. Sarazin, E. Blanton

5 NO SYSTEMATIC UNCERTAINTIES!!!

6 Cluster Outskirts and Suzaku Suzaku has allowed for systematic studies of the ICM in clusters out to their virial radii: PKS0745 (George+09); A2204 (Reiprich+09); A1795 (Bautz+09); A1413 (Hoshin+10); A1689 (Kawaharada+10); A2142 (Akamatsu+11); Virgo (Urban+11); Perseus (Simionescu+11,Urban+14); RXJ1159 (Humphrey+12,Su+15); Hydra A (Sato+12); A2029 (Walker+12); ESO (Su+13); Centaurus (Walker+13);... Two general methods: most-to-all of azimuth at R 200 with smaller FOV, or arms out to R 200 for larger FOV

7 Perseus Urban+14

8 Entropy Profiles Entropy profile predicted by purely gravitational simulations of heirarchical structure formation (Voit+05; Pratt+10): K(R)/K 500 = 1.47(R/R 500 ) 1.1 Generally, entropy is found to lie above the self-similar prediction within 0.5 R 200 and above at R 200

9 Walker+13 (Black line from XMM REXCESS sample of Pratt+10)

10 Entropy Flattening Various explanations have been proposed: Gas clumping (Simionescu+11) Weakening accretion shocks (Lapi+10; Cavaliere+11) e-i non-equilibrium (Hoshino+10; Akamatsu+11) Non-thermal pressure support (Lau+09) Can construct self-similar temperature and density profiles from self-similar entropy and universal pressure profiles (Arnaud+10; Walker+13)

11 Walker+13 kt follows SS, drops outside R 200, n H above SS near R 200 (entropy drop due to kt in 2/13 clusters in Walker+13) Supports gas clumping, where kt of cool gas clumps is higher due to ramp pressure stripping support Clumping also expected from simulations (Roncarelli+06, Nagai+11)

12 Urban+14 find that SS deviations in Perseus depend on azimuth Find less deviation along cluster minor access. Clumps destroyed in more dynamically active regions? Urban+14 Strongly merging clusters are a good place to look for correlations with large scale structure, since we know where the filaments should be

13 Einstein Double Clusters Forman+81 March 15-20, 2015, Snowbird, Utah SnowCluster - The Physics of Galaxy Clusters S. W. Randall

14 A115 1 Mpc

15 Einstein Double Clusters Advantages: Bright enough and separated enough to be detected with Einstein Close enough to be covered in a few pointings 3+ collinear subclusters strongly suggest LSS filament Relatively cool (3-6 kev), need fewer counts to measure temperature Only a few cool, low mass clusters explored to their virial radii Goals: Compare on- and off-filament ICM properties Differences in entropy flattening/gas clumping signatures Look for accretion shocks Look for cool filament (WHIM-ish) emission Strategy: Chandra in between subclusters, Suzaku out to R 200

16 Einstein Double Clusters z Chandra XMM Suzaku A98 A1750 A115 A3395/A Non-PI data

17 Abell 115 A115 1 Mpc

18 Abell 115 Radio lobes point in direction if subcluster motion Can be explained by gas circulation patterns (Forman+15) Simulations suggest v flow km/s v circ km/s, with large projection uncertainties (Heinz+03) kt map reveals hot, presumably shock-heated region between subclusters

19 Abell 3395/3391 A3391 A3395/A3391 A Mpc

20 Abell 3395/3391 Galaxy Redshift Distribution ASCA GIS IMAGE Tittley & Henriksen 01 Detect filamentary gas between subclusters with ROSAT and ASCA Conclude that it is a filament tilted close to the line of sight, with a radial to tangential ratio of 6 < l rad /l tan < 18

21 Abell 3395/3391 Clusters and bridge detected by Planck (PC15, see also Sunday s talk by Marcias-Perez)

22 A3395/A3391 (Chandra) PRELIMINARY! Diffuse gas detected across filament, such detections are rare (e.g., A222/ A223 Werner+08) Galaxy group located where the virial radii of A3395 and A3391 overlap 1 Mpc Randall+15, in prep.

23 A3395/A3391 A3395/A3391 (Chandra) (Chandra) PRELIMINARY! No systematic uncertainty (increases error bars by 5-10% in faintest regions) 1 Mpc 1 Mpc Diffuse gas temperature measured across filament Coolest region contains galaxy group

24 A3395/A3391 (Chandra) PRELIMINARY! Subcluster Properties A3395E: kt = 5.1+/-0.3 kev; Ab = 0.44+/-0.15 A3395W: kt = 5.3+/-0.3 kev; Ab = 0.24+/-0.14 A3391: kt = 6.0+/-0.25 kev; Ab = 0.33+/-0.10 Global Filament Properties (includes group) kt = 2.9+/-0.5 kev Ab = 0.2 +/-0.14 Assuming cylindrical geometry for filament: n e = / cm -3 (l rad /1.2 Mpc) -0.5 M gas = 2.3 +/ M sun (l rad /1.2 Mpc) Mpc For 6 < l rad /l tan < 18: 3.7e-5 < n e < 6.4e-5 cm e12 < M gas < 1.0e13 M sun

25 Abell 98 A98 1 Mpc

26 A98N Abell 98 Results published in Paterno- Mahler+14 Faint bridge between A98N/A98S, consistent with overlapping atmospheres, although errors are large A98S N/S elongation of A98N and N/S asymmetry of A98S suggest interaction Double core in A98S, ongoing late stage merger A98SS 0.5 Mpc Dynamical analysis indicates bound ingoing orbit for A98N/A98S (A98SS is unbound)

27 Abell 98 Temperature map shows arc of hot gas south of A98N, coincident with a surface brightness enhancement in the residual image, which is potentially a shock Detailed spectral fits support hotter gas in this region (kev): kt S1 = ; kt S2 = kt N1 = ; kt N2 = Dynamical analysis, possible shock, and X-ray morphology are all consistent with an early stage merger between A98N/A98S Deeper observations are required to confirm shock (first unambiguous shock in such an early stage merging system) and determine nature of the bridge emission (cooler filament gas, or hotter cluster gas)

28 Abell 1750 A Mpc

29 Abell 1750 XMM observations analyzed in Belsole+04, Chandra (and numerical simulations) in Molnar+13 Both studies conclude that A1750N and A1750C are in an early premerger state, and are just beginning to interact Belsole+04 find evidence for a weak shock edge 450 kpc SE of A1750C, unrelated to early stage merger with A1750N Both studies find evidence of a temperature increase between A1750N and A1750C, possibly due to a shock

30 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) 1 Mpc

31 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) 1 Mpc

32 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) 7 6 A1750N A1750C A1750S Temperatures (kev) Mpc Distance (arcmin)

33 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) 1 Mpc

34 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) Flux (counts cm -2 s -1 arcmin -2 ) e-05 North South East R 500 R Mpc 1e Radius (arcmin)

35 Abell 1750 A1750 PRELIMINARY! NO SYSTEMATIC UNCERTAINTIES (Bulbul+15, in prep.) Temperature measurements in faint regions complicated by filament, area lost to point sources, and background systematics 1 Mpc

36 Abell 1750 PRELIMINARY! Temperature (kev) South East R 500 R 200 Temperature drops sharply to the SE North Radius (arcmin)

37 Abell 1750 PRELIMINARY! Temperature drops sharply to the SE Reasons 5 to worry: Temperature (kev) Leccardi & Molendi07,08 argue fixing BG model will South East North 1 10 Radius (arcmin) R 500 R 200 bias kt low due to statistical fluctuations in the BG Uncertainties in GH (kt 0.2) and LHB (kt 0.1) Contamination from SE filament? Affected by SE merger reported by Belsole+04, perhaps a subgroup? Or heated core?

38 Abell 1750 PRELIMINARY! Entropy (kev cm 2 ) South-East North R 500 R 200 Self-Similar Radius (arcmin) North flatter than SS at small radii, consistent at large radii SE shows entropy flattening at large radii Consistent with more clumps in less dynamically active regions, as in Perseus? Flattening driven by low kt instead of high n e, only the case for 2/13 clusters in Walker+13 Beyond R 200 (maybe elliptical on large scales due to filament)? Effect of reported shock? Cooler system?

39 Summary Observations have shown flattening in entropy profiles around R 200 that appears to correlate with large scale structure Strongly merging binary+ clusters are good places to look for such dependencies, since the orientation of LSS filaments is implied Of our 4 early stage merger clusters, 3 (A115, A98, A1750) show evidence of merger shocks and 3 (A98, A3395/A3391,A1750) show faint bridges of emission between subclusters Emission is detected out to R 200 in A1750 with Suzaku, both on and off the putative filament Preliminary results suggest a flattening entropy profile perpendicular to the filament but not along it, consistent with more cool gas clumps in less dynamically active regions, as found in Perseus (but much more work is needed!)

40 Abell 1750 XMM observations analyzed in Belsole+04, Chandra (and numerical simulations) in Molnar+13 Both studies conclude that A1750N and A1750C are in an early premerger state, and are just beginning to interact Belsole+04 find evidence for a weak shock edge 450 kpc SE of A1750C Both studies find evidence of a temperature increase between A1750N and A1750C, possibly due to a shock Molnar+13