Presentation on theme: "Galaxies Cluster formation : Numerical Simulations and XMM Observations JL Sauvageot *, Elena Belsole *,R.Teyssier *, Herve Bourdin + Service d'Astrophysique."— Presentation transcript:
Galaxies Cluster formation : Numerical Simulations and XMM Observations JL Sauvageot *, Elena Belsole *,R.Teyssier *, Herve Bourdin + Service d'Astrophysique CEA-Saclay +NICE Observatory Palermo, 2003 I) Simulations of Merging Clusters of galaxies II) Convolution and Temperature map Reconstruction III) XMM Observations of A1750, A3921 and A2065 IV) Conclusion
Major mergers Quiet accretion Two paths for building clusters : Through nearly continuous groups infall m group << M Clus Or by Major Merger M Clus1 ~ M Clus2 From observations we learn that: Most clusters are accreting smaller clumps at present. 3 to15 % of clusters have undergoing a major merger in the last Gyr (at low redshift). Galaxies Clusters Formation Cavaliere et al.
I) Mergers in cosmological environment RAMSES : Teyssier, 2002, A&A,385,337 Particle-Mesh Method (N-Body, Dark Matter) Pieceweise Linear Method (Euler Equation, Gas) Adaptive Mesh Refinement Starting from Initials Density Fluctuations, you could not set where the cluster will form, what are the parameters of the collisions, what is the history of previous events... Simulation in 2 runs : -1- Box of universe of L box =400 h -1 Mpc Npart=128 3, CDM simulation => ~ 100 clusters -2- Zoom onto one Major Merging Event (re- play) Same Universe Box with more than 400 000 particles and mesh points within the selected cluster Virial radius. ==> realistic simulation of large scale potential & continuous infall AND high local resolution. The mesh spacing in the cluster core went down to 6 h -1 kpc, (corresponding to a formal resolution of 65536 3 ) Dark Matter Grid Spacing Temperature
II) Cosmological Simulation as seen through XMM-Newton From RAMSES Simul., we have r,T for each cell (+x,y,z position) Generation of photons list using Plasma code Database + Monte-Carlo Using XMM Calibration files to emulate the Instrument Then Comparison between observation and simulations. Cosmological Simulation are much more realistic but : One could not chose the Initial collision parameters. Much more complex initial state of the units due to their own history of merging. Density (or X-ray Low Energy ) Map : shows gas distribution with limited contrast (even in strong shock case, r/r 4) Temperature (or Hardness Ratio) Map : Higher Contrast in T, Lifetime up to 6 time longer. but less direct (and much more difficult to achieve). From X-rays Observations of Mergers we get :
II) Cluster merging in a realistic Cosmological environment. X rays(Low Energy) Temperature map AFTER XMM/EPIC and Tmap Algo. Temperature Map Computation for X-ray Cluster of Galaxies : H. Bourdin et al. A&A 2003 accepted Emissivity EM weighted Temp. BEFORE the instrument simulation. Compression Shock Z=0.13 Z=0.09 Z=0.
IIIa) A1750 XMM Observation kT map enhancement of T in the interaction region+ History effect Low Energy [0.3-0.6 keV] image Adaptatively Smoothed. 1.0 keV 6 keV z=0.086; 30 ksec GT; Bi-modal structure ; ~1 to 1 mass Collision; Projected Distance between units ~ 1Mpc ; V redshift ~1000 km/s (NB. Vignetting Effect) kT=2.84+/-0.12 keV kT=5.12+/-0.7 keV kT=3.87+/-0.1 keV An XMM-Newton Observation of the dynamically active binary cluster A1750 : E.Belsole et al. A&A,2003 submitted
A1750 is a real merger just at the beginning of the event: Detection of a hotter region in the interaction zone. BUTits 2 sub-units are already NOT relaxed (highly distorted contours+ very complex Temperature Structure) ==> A1750 is an observational evidence that Time Interval between collision is (at least sometime) shorter than relaxation time IIIa) A1750 Conclusions Comparing projected distance (1Mpc) and Numerical Simulations of major merger units at that distance ==> Real distance between units should be higher==>Strong Projection Effect Rosat PSPC Field
Main Component Spectrum 4.35+/-0.1 keV B1: Interaction zone Spectrum 5.6+/-0.3 keV IIIb) A3921 XMM Observation Z=0.094, 30 ksec GT Observation 3 cD galaxies Highly elongated X-ray structure Adaptatively smoothed Low Energy Image
IIIb) A3921 XMM Observation 3.00 6.00 All galaxies used to build the map are at z A3921 with m Gal <22. Galaxies are less collisional than Gas ==> They better follow the Dark Matter potential. Optical data from Nice Obs. Collaborators Temp. Map with adaptative bining Multiscale Temp. Map reconstruction Galaxies Density map.
IIIb) Idealized 3M/M Simulation of merger with a Large Impact Parameter b=5 r s L X contours onto Temperature map -0.5 0 1 Gyr Time Density contours onto Dark Matter map Galaxies Density Map M over 3M collision Ricker&Sarazin2001
A3921 is a complex case of merger: From X-rays : Hotter interaction region NOT orthogonal to the line linking the centers of the sub-units but nearly parallel to it. From Optical: Velocity information+ Galaxy Density Map do NOT support the pre-merger view. Proposed scenario: The small group has already pass through the main cluster with an impact parameter 0 IIIb) A3921 Preliminary Conclusions
IIIc) A2065: a Merger in the compact phase seen with XMM 30 ksec but Very High Level of Protons ==> very specific treatment ==> Model of the protons spectrum and spatial distribution. ==> Analysis limited by statistics and confidence but a Shock wave could have been detected on A2065 A2065 Low Energy EPIC Map kT map Simulation Hardness Ratio Map + Surviving Cooling flow... will be re-observed during AO3
IV)Conclusions Numerical Simulations seem to agree qualitatively with X-ray observations of early mergers, BUT detailed quantitative comparisons still need to be done. -A1750 seems to be an early merger bi-modal system. But its 2 sub-units are already not relaxed due to their own history. -A3921 is much more complex : it may be an off-axis 3/1 Mass late merger. (detailed optical vs X- ray comparison to be done) -A2065 really looks like a Compact Post Merger. Better quality data needed to confirm (XMM-AO3). To understand the X-rays mergers observations, we definitely need : Data in Visible and Numerical Simulations
The Observable : Image represent the emission weighted Temperature Contours are the X - ray Luminosity -0.5 0 1 2 3.5 Gyr B=0 B=2 r s B=5 r s Ia) Idealized Simulation (Ricker&Sarazin2001) Impact Parameter Time