multiwavelength observations of clusters of galaxies · multiwavelength observations of clusters of...
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![Page 1: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/1.jpg)
Multiwavelength Observations of Clusters ofGalaxies
Andisheh Mahdavi
Department of Physics and AstronomySan Francisco State University
September 2, 2008
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Outline
1 IntroductionWhat good are clusters of galaxies?Physics with clusters of galaxies
2 Understanding Relaxed ClustersMass Measurement Techniques at Many WavelengthsCCCP SurveyJoint Analysis of Cluster ObservationsEvidence for Non-hydrostatic Gas
3 Dark Matter and Violent MergersThe Bullet and MACS ClustersAbell 520Chain of slingshots or something more exotic?
![Page 3: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/3.jpg)
Introduction
Outline
1 IntroductionWhat good are clusters of galaxies?Physics with clusters of galaxies
2 Understanding Relaxed ClustersMass Measurement Techniques at Many WavelengthsCCCP SurveyJoint Analysis of Cluster ObservationsEvidence for Non-hydrostatic Gas
3 Dark Matter and Violent MergersThe Bullet and MACS ClustersAbell 520Chain of slingshots or something more exotic?
![Page 4: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/4.jpg)
Introduction What good are clusters of galaxies?
Evolution of Structure in the UniverseCurrent structure formation picture
We live in an accelerating universe (Ωm ∼ 14 , ΩΛ ∼ 3
4 )Early on, this universe was hot, dense, and nearly (but notperfectly) uniformAfter matter decoupled from radiation, small density perturbationsgrew nonlinearlySmaller objects formed first, and then grew hierarchically intolarger and larger structuresClusters of galaxies, the most massive collapsed structures, tellus about the composition and fate of matter in the universe
![Page 5: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/5.jpg)
Introduction What good are clusters of galaxies?
Evolution of Structure in the UniverseCurrent structure formation picture
We live in an accelerating universe (Ωm ∼ 14 , ΩΛ ∼ 3
4 )Early on, this universe was hot, dense, and nearly (but notperfectly) uniformAfter matter decoupled from radiation, small density perturbationsgrew nonlinearlySmaller objects formed first, and then grew hierarchically intolarger and larger structuresClusters of galaxies, the most massive collapsed structures, tellus about the composition and fate of matter in the universe
![Page 6: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/6.jpg)
Introduction What good are clusters of galaxies?
Evolution of Structure in the UniverseCurrent structure formation picture
We live in an accelerating universe (Ωm ∼ 14 , ΩΛ ∼ 3
4 )Early on, this universe was hot, dense, and nearly (but notperfectly) uniformAfter matter decoupled from radiation, small density perturbationsgrew nonlinearlySmaller objects formed first, and then grew hierarchically intolarger and larger structuresClusters of galaxies, the most massive collapsed structures, tellus about the composition and fate of matter in the universe
![Page 7: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/7.jpg)
Introduction What good are clusters of galaxies?
Evolution of Structure in the UniverseCurrent structure formation picture
We live in an accelerating universe (Ωm ∼ 14 , ΩΛ ∼ 3
4 )Early on, this universe was hot, dense, and nearly (but notperfectly) uniformAfter matter decoupled from radiation, small density perturbationsgrew nonlinearlySmaller objects formed first, and then grew hierarchically intolarger and larger structuresClusters of galaxies, the most massive collapsed structures, tellus about the composition and fate of matter in the universe
![Page 8: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/8.jpg)
Introduction What good are clusters of galaxies?
Evolution of Structure in the UniverseCurrent structure formation picture
We live in an accelerating universe (Ωm ∼ 14 , ΩΛ ∼ 3
4 )Early on, this universe was hot, dense, and nearly (but notperfectly) uniformAfter matter decoupled from radiation, small density perturbationsgrew nonlinearlySmaller objects formed first, and then grew hierarchically intolarger and larger structuresClusters of galaxies, the most massive collapsed structures, tellus about the composition and fate of matter in the universe
![Page 9: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/9.jpg)
Introduction What good are clusters of galaxies?
Collapse of a rich cluster of galaxiesStarting 200 million years after the big bang
Courtesy Volker Springel, MPA Garching
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Introduction What good are clusters of galaxies?
Composition a Typical Clusters of Galaxies at z ≈ 0
Mass budget of a typical rich cluster:5% stars
Typically in galaxies with older (red) stellar populationsStar-forming (blue) galaxies on the outskirtsOccasionally, gas cools enough to form stars at the core
15% plasmaLargely thermal electron populationBremsstrahlung at 1-10 keVNonthermal contributions: turbulence, shocks, cosmic rays
80% dark matterFavored candidate: SUSY relic or axion (CDM)Neutrinos (HDM), substellar bodies (MACHOS) disfavoredVery resistant to alternative theories of gravity
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Introduction What good are clusters of galaxies?
Composition a Typical Clusters of Galaxies at z ≈ 0
Mass budget of a typical rich cluster:5% stars
Typically in galaxies with older (red) stellar populationsStar-forming (blue) galaxies on the outskirtsOccasionally, gas cools enough to form stars at the core
15% plasmaLargely thermal electron populationBremsstrahlung at 1-10 keVNonthermal contributions: turbulence, shocks, cosmic rays
80% dark matterFavored candidate: SUSY relic or axion (CDM)Neutrinos (HDM), substellar bodies (MACHOS) disfavoredVery resistant to alternative theories of gravity
![Page 12: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/12.jpg)
Introduction What good are clusters of galaxies?
Composition a Typical Clusters of Galaxies at z ≈ 0
Mass budget of a typical rich cluster:5% stars
Typically in galaxies with older (red) stellar populationsStar-forming (blue) galaxies on the outskirtsOccasionally, gas cools enough to form stars at the core
15% plasmaLargely thermal electron populationBremsstrahlung at 1-10 keVNonthermal contributions: turbulence, shocks, cosmic rays
80% dark matterFavored candidate: SUSY relic or axion (CDM)Neutrinos (HDM), substellar bodies (MACHOS) disfavoredVery resistant to alternative theories of gravity
![Page 13: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/13.jpg)
Introduction What good are clusters of galaxies?
The Physics of Clusters of GalaxiesClusters lie at the intersection of several unsolved problems in astrophysics
Through clusters we can address vital questions:
Fundamental cosmological parametersThe nature of dark matterThe physics of cooling and heating in astrophysical plasmas
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Introduction Physics with clusters of galaxies
Cosmology with Clusters of GalaxiesAllen et al. 2007
Ωm = 1,ΩΛ = 0 Ωm = 0.25,ΩΛ = 0.75
0 0.5 1
0.05
0.1
0.15
0.2
f gas (r
2500
) h 50
1.5
z0 0.5 1
00.
050.
10.
15
f gas (r
2500
) h 70
1.5
z
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Introduction Physics with clusters of galaxies
Cosmology with Clusters of GalaxiesAllen et al. 2007
Ωm
w0
0 0.1 0.2 0.3 0.4 0.5 0.6−2.5
−2
−1.5
−1
−0.5
0
CMB
SNIa
Cluster fgas
Ωm
w0,w
et0.1 0.2 0.3 0.4 0.5
−3
−2.5
−2
−1.5
−1
−0.5
0
0.5
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Introduction Physics with clusters of galaxies
Canonical Cold Dark MatterNavarro et al. 1997, Ghigna et al. 2001, and others
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Introduction Physics with clusters of galaxies
Canonical Cold Dark MatterHigher resolution: Navarro et al. 2004, Merritt et al. 2005
ρdm ∝ r−n(r200 + cr)n−3
n is the “slope”c is the concentrationn ≈ 1 − 1.5 dependingon size of structureFlat cores (n = 0) donot occur in CDM
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Introduction Physics with clusters of galaxies
Mass-concentration relationFrom gravitational lensing; Mandelbaum, Seljak, & Hirata 2008
M-c relation ispotentially powerfulcosmologicaldiscriminantHowever, precision inc is currently thelimiting factor forcosmological tests
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Introduction Physics with clusters of galaxies
Cooling and Heating of the Intracluster PlasmaPerseus cluster, Fabian et al. 2005
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Introduction Physics with clusters of galaxies
Cooling and Heating of the Intracluster PlasmaSimulating feedback from active galactic nuclei
Courtesy Markus Brueggen, Jacobs University Bremen
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Introduction Physics with clusters of galaxies
Disturbances due to shocks and cold frontsDisruptions of the intracluster medium by the hierarchical structure formation process
Courtesy Daisuke Nagai
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Introduction Physics with clusters of galaxies
Physics with clusters of galaxies
With clusters we can get at dark matter and dark energy.To do this, we need to understand the evolution of galaxies andthe intracluster plasma along the way
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Understanding Relaxed Clusters
Outline
1 IntroductionWhat good are clusters of galaxies?Physics with clusters of galaxies
2 Understanding Relaxed ClustersMass Measurement Techniques at Many WavelengthsCCCP SurveyJoint Analysis of Cluster ObservationsEvidence for Non-hydrostatic Gas
3 Dark Matter and Violent MergersThe Bullet and MACS ClustersAbell 520Chain of slingshots or something more exotic?
![Page 24: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/24.jpg)
Understanding Relaxed Clusters Mass Measurement
HydrodynamicsX-ray observations
X-ray spectra→ X-ray temperatures
1ρg
ddr
(ρgkTµmp
)= −
G(Md + Mg + Ms)r2 .
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Understanding Relaxed Clusters Mass Measurement
Weak gravitational lensingOptical observations
Shear profile:
〈gT〉(R) =κ(< R)− κ(R)
1− κ(R)
κ(R) =Σ(R)Σcrit
From Wittman et al. (2000)
Kaiser, Squires, & Broadhurst (KSB) shear measurement technique
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Understanding Relaxed Clusters Mass Measurement
Sunyaev-Zel’dovich EffectRadio observations
Courtesy WMAP Science Team
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Understanding Relaxed Clusters Mass Measurement
Sunyaev-Zel’dovich EffectRadio observations
Courtesy L. Van Speybroeck / U. Chicago
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Understanding Relaxed Clusters Mass Measurement
Radio: Sunyaev-Zel’dovich Effect
∆T/TCMB ≈ 2y
y =∫
PσT
mec2 dl
=∫σT
ρg
∫GMρg
mec2r2 dl
From Birkinshaw (1998)
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Understanding Relaxed Clusters CCCP Survey
Canadian Cluster Comparison ProjectMahdavi, Hoekstra, Babul; (UVic); Henry (IfA); Sievers (CITA)
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Understanding Relaxed Clusters CCCP Survey
Canadian Cluster Comparison ProjectDetailed study of ≈ 30 massive clusters (kT > 5 keV)
Data sources:X-rays: archival and proprietary Chandra and XMM-Newton dataOptical: CFHT/Gemini/HST for weak lensing and spectroscopyRadio: Cosmic Background Imager
Project goals:
Relaxed systems: Dark matter profiles from simultaneous modelingof all data at all wavelengthsMerging systems: Maps of X-ray / Lensing offsets, comparison withour own N-body “collider”Study nonthermal contributors to plasma equation of state
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Understanding Relaxed Clusters CCCP Survey
Canadian Cluster Comparison ProjectDetailed study of ≈ 30 massive clusters (kT > 5 keV)
Data sources:X-rays: archival and proprietary Chandra and XMM-Newton dataOptical: CFHT/Gemini/HST for weak lensing and spectroscopyRadio: Cosmic Background Imager
Project goals:
Relaxed systems: Dark matter profiles from simultaneous modelingof all data at all wavelengthsMerging systems: Maps of X-ray / Lensing offsets, comparison withour own N-body “collider”Study nonthermal contributors to plasma equation of state
![Page 32: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/32.jpg)
Understanding Relaxed Clusters JACO
Joint Analysis of Cluster ObservationsMahdavi et al. 2007a
1 New physical insightsCombining X-ray, lensing, and SZ data breaks degeneracies in thestructural parameter of the gravitational potentialStudy the covariance of all astrophysical parameters (gasmetallicty, dark matter slope, mass-to-light ratio . . . )
2 Designed to deal with real data
First time real X-ray, lensing, and SZ data are jointly fitModels are projected and convolved with instrumental response
3 Modular, state-of-the-art codebase
Easily handle new astrophysics (e.g. turbulence, cooling/heating)Includes new distributed minimization algorithms (Hrothgar)Can run on (for large data sets, requires) Beowulf clusters
![Page 33: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/33.jpg)
Understanding Relaxed Clusters JACO
Joint Analysis of Cluster ObservationsMahdavi et al. 2007a
1 New physical insightsCombining X-ray, lensing, and SZ data breaks degeneracies in thestructural parameter of the gravitational potentialStudy the covariance of all astrophysical parameters (gasmetallicty, dark matter slope, mass-to-light ratio . . . )
2 Designed to deal with real data
First time real X-ray, lensing, and SZ data are jointly fitModels are projected and convolved with instrumental response
3 Modular, state-of-the-art codebase
Easily handle new astrophysics (e.g. turbulence, cooling/heating)Includes new distributed minimization algorithms (Hrothgar)Can run on (for large data sets, requires) Beowulf clusters
![Page 34: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/34.jpg)
Understanding Relaxed Clusters JACO
Joint Analysis of Cluster ObservationsMahdavi et al. 2007a
1 New physical insightsCombining X-ray, lensing, and SZ data breaks degeneracies in thestructural parameter of the gravitational potentialStudy the covariance of all astrophysical parameters (gasmetallicty, dark matter slope, mass-to-light ratio . . . )
2 Designed to deal with real data
First time real X-ray, lensing, and SZ data are jointly fitModels are projected and convolved with instrumental response
3 Modular, state-of-the-art codebase
Easily handle new astrophysics (e.g. turbulence, cooling/heating)Includes new distributed minimization algorithms (Hrothgar)Can run on (for large data sets, requires) Beowulf clusters
![Page 35: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/35.jpg)
Understanding Relaxed Clusters JACO
Application to the Abell 478 Cluster of Galaxies3% of Abell 478 X-ray data is shown
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Understanding Relaxed Clusters JACO
Fit results: SZ and lensing data
→ The same physical model fits the lensing, X-ray, and SZ dataself-consistently.
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Understanding Relaxed Clusters JACO
Covariance of all cluster observables
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Understanding Relaxed Clusters JACO
Covariance of dark matter parameters
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Understanding Relaxed Clusters JACO
Covariance of dark matter parametersUsing only SZ and Weak lensing, gas mass fixed at X-ray value
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Understanding Relaxed Clusters JACO
Conditions for correctness of joint analysis
Error in dark matter concentration can be halved via joint analysisRelevant for high redshift survey: SZ + WL only require the X-raysurface brightnessBut there are caveats...Reliance on hydrostatic analysisTheory says gas should be nonhydrostaticBut are there “more hydrostatic” regions within a cluster?
Interior disturbed by cooling gasExterior incompletely thermalized due to bulk motions
![Page 41: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/41.jpg)
Understanding Relaxed Clusters JACO
Conditions for correctness of joint analysis
Error in dark matter concentration can be halved via joint analysisRelevant for high redshift survey: SZ + WL only require the X-raysurface brightnessBut there are caveats...Reliance on hydrostatic analysisTheory says gas should be nonhydrostaticBut are there “more hydrostatic” regions within a cluster?
Interior disturbed by cooling gasExterior incompletely thermalized due to bulk motions
![Page 42: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/42.jpg)
Understanding Relaxed Clusters JACO
Conditions for correctness of joint analysis
Error in dark matter concentration can be halved via joint analysisRelevant for high redshift survey: SZ + WL only require the X-raysurface brightnessBut there are caveats...Reliance on hydrostatic analysisTheory says gas should be nonhydrostaticBut are there “more hydrostatic” regions within a cluster?
Interior disturbed by cooling gasExterior incompletely thermalized due to bulk motions
![Page 43: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/43.jpg)
Understanding Relaxed Clusters JACO
Conditions for correctness of joint analysis
Error in dark matter concentration can be halved via joint analysisRelevant for high redshift survey: SZ + WL only require the X-raysurface brightnessBut there are caveats...Reliance on hydrostatic analysisTheory says gas should be nonhydrostaticBut are there “more hydrostatic” regions within a cluster?
Interior disturbed by cooling gasExterior incompletely thermalized due to bulk motions
![Page 44: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/44.jpg)
Understanding Relaxed Clusters JACO
Conditions for correctness of joint analysis
Error in dark matter concentration can be halved via joint analysisRelevant for high redshift survey: SZ + WL only require the X-raysurface brightnessBut there are caveats...Reliance on hydrostatic analysisTheory says gas should be nonhydrostaticBut are there “more hydrostatic” regions within a cluster?
Interior disturbed by cooling gasExterior incompletely thermalized due to bulk motions
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Understanding Relaxed Clusters Evidence for Non-hydrostatic Gas
Evidence for Non-hydrostatic GasA dramatic first result for the JACO+CCCP survey
Comparison of Weak Lensing and X-ray derived masses
M(r∆) = 4π∆r3∆ρc/3
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Understanding Relaxed Clusters Evidence for Non-hydrostatic Gas
Evidence for Non-hydrostatic GasProperly taking data covariance into account
1.03± 0.07 (r2500) and 0.78± 0.09 (r500) are correlatedData used for M2500 goes into M500 as well.
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Understanding Relaxed Clusters Evidence for Non-hydrostatic Gas
Comparison with N-body workX-ray and “true” masses agree at r2500, disagree at r500
Consistent with recent N-body simulations involving bulk motions:
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Dark Matter and Violent Mergers
Outline
1 IntroductionWhat good are clusters of galaxies?Physics with clusters of galaxies
2 Understanding Relaxed ClustersMass Measurement Techniques at Many WavelengthsCCCP SurveyJoint Analysis of Cluster ObservationsEvidence for Non-hydrostatic Gas
3 Dark Matter and Violent MergersThe Bullet and MACS ClustersAbell 520Chain of slingshots or something more exotic?
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Dark Matter and Violent Mergers The Bullet and MACS Clusters
The Bullet ClusterClowe et al. 2006
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Dark Matter and Violent Mergers The Bullet and MACS Clusters
The MACS Extreme MergerBradac et al. 2008
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Dark Matter and Violent Mergers The Bullet and MACS Clusters
Simulation of bullet cluster collision
Courtesy KIPAC/John Wise
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Dark Matter and Violent Mergers Abell 520
Abell 520, CFHT optical image
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Dark Matter and Violent Mergers Abell 520
Abell 520, red light (likely members)
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Dark Matter and Violent Mergers Abell 520
Abell 520, Chandra X-ray emission
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Dark Matter and Violent Mergers Abell 520
Abell 520, Weak gravitational lensing signal
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Dark Matter and Violent Mergers Abell 520
Abell 520 multiwavelength imageMahdavi et al. 2007b
Mtot/LB
1: 234± 622: 85± 253: 721± 1794: 135± 255: 57± 49
Mgas/Mtot1: < 0.052: < 0.123: < 0.174: < 0.075: < 1
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Dark Matter and Violent Mergers Abell 520
Abell 520 Dark CoreHow confident are we in the result?
Chance superpositions and other trivial explanations ruled out:Redshift measurements for the X-ray gas as well as thegalaxies—all coincideLensing signal as a function of magnitude rules out a backgroundcluster (light or dark) beyond z = 0.7
Any normal cluster within z = 0.7 would have been detectedspectroscopicallyNot an overlap of two NFW or isothermal halos (too much mass)Dark matter-only “bridges” of this mass and size do not occur inCDM merger simulations
Bottom line: we are confident in the result at the stated level of 3σ(statistical+systematic) excess M/L
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Dark Matter and Violent Mergers Abell 520
Abell 520 Dark CoreHow confident are we in the result?
Chance superpositions and other trivial explanations ruled out:Redshift measurements for the X-ray gas as well as thegalaxies—all coincideLensing signal as a function of magnitude rules out a backgroundcluster (light or dark) beyond z = 0.7
Any normal cluster within z = 0.7 would have been detectedspectroscopicallyNot an overlap of two NFW or isothermal halos (too much mass)Dark matter-only “bridges” of this mass and size do not occur inCDM merger simulations
Bottom line: we are confident in the result at the stated level of 3σ(statistical+systematic) excess M/L
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Dark Matter and Violent Mergers Abell 520
Abell 520 Dark CoreHow confident are we in the result?
Chance superpositions and other trivial explanations ruled out:Redshift measurements for the X-ray gas as well as thegalaxies—all coincideLensing signal as a function of magnitude rules out a backgroundcluster (light or dark) beyond z = 0.7
Any normal cluster within z = 0.7 would have been detectedspectroscopicallyNot an overlap of two NFW or isothermal halos (too much mass)Dark matter-only “bridges” of this mass and size do not occur inCDM merger simulations
Bottom line: we are confident in the result at the stated level of 3σ(statistical+systematic) excess M/L
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Dark Matter and Violent Mergers Abell 520
Abell 520 Dark CoreHow confident are we in the result?
Chance superpositions and other trivial explanations ruled out:Redshift measurements for the X-ray gas as well as thegalaxies—all coincideLensing signal as a function of magnitude rules out a backgroundcluster (light or dark) beyond z = 0.7
Any normal cluster within z = 0.7 would have been detectedspectroscopicallyNot an overlap of two NFW or isothermal halos (too much mass)Dark matter-only “bridges” of this mass and size do not occur inCDM merger simulations
Bottom line: we are confident in the result at the stated level of 3σ(statistical+systematic) excess M/L
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Dark Matter and Violent Mergers Abell 520
Abell 520 Dark CoreHow confident are we in the result?
Chance superpositions and other trivial explanations ruled out:Redshift measurements for the X-ray gas as well as thegalaxies—all coincideLensing signal as a function of magnitude rules out a backgroundcluster (light or dark) beyond z = 0.7
Any normal cluster within z = 0.7 would have been detectedspectroscopicallyNot an overlap of two NFW or isothermal halos (too much mass)Dark matter-only “bridges” of this mass and size do not occur inCDM merger simulations
Bottom line: we are confident in the result at the stated level of 3σ(statistical+systematic) excess M/L
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Dark Matter and Violent Mergers Abell 520
Abell 520, Weak gravitational lensing signal
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Dark Matter and Violent Mergers Abell 520
Abell 520 multiwavelength imageMahdavi et al. 2007b
Mtot/LB
1: 234± 622: 85± 253: 721± 1794: 135± 255: 57± 49
Mgas/Mtot1: < 0.052: < 0.123: < 0.174: < 0.075: < 1
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Dark Matter and Violent Mergers Abell 520
Abell 520 and the Bullet ClusterThey differ in the relative offset of dark matter and galaxies
In Bullet cluster, mass is where the galaxies are, and vice versa.In Abell 520, the core has mass and X-ray but almost no galaxies,Peak 5 has galaxies, but little mass (baryon fraction ∼ 1).
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDid the dark matter and galaxies separate during the merger? If so, how?
Peak is 5σ detection; excess M/L is 3σ. Followup:18 orbits HST time—just completed!500ks of Chandra data—in handKeck DEIMOS spectroscopy—in hand
If the result is confirmed, two unpalatable choices:Galaxies separated from DM via complex slingshotsDark matter self-interaction partly responsible
Implied cross section is 4± 1 cm2/gStill much smaller than coulomb interaction cross-section,≈ 1200 cm2/g for 1000 km/s gas collision
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDid the dark matter and galaxies separate during the merger? If so, how?
Peak is 5σ detection; excess M/L is 3σ. Followup:18 orbits HST time—just completed!500ks of Chandra data—in handKeck DEIMOS spectroscopy—in hand
If the result is confirmed, two unpalatable choices:Galaxies separated from DM via complex slingshotsDark matter self-interaction partly responsible
Implied cross section is 4± 1 cm2/gStill much smaller than coulomb interaction cross-section,≈ 1200 cm2/g for 1000 km/s gas collision
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDid the dark matter and galaxies separate during the merger? If so, how?
Peak is 5σ detection; excess M/L is 3σ. Followup:18 orbits HST time—just completed!500ks of Chandra data—in handKeck DEIMOS spectroscopy—in hand
If the result is confirmed, two unpalatable choices:Galaxies separated from DM via complex slingshotsDark matter self-interaction partly responsible
Implied cross section is 4± 1 cm2/gStill much smaller than coulomb interaction cross-section,≈ 1200 cm2/g for 1000 km/s gas collision
![Page 68: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/68.jpg)
Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleChain of slingshots works with the small halo galaxies, not the largest ones
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
0 5 10 15 20log mχ [GeV]
-30
-25
-20
-15
-10
-35
-40
-45
log
σ χN [
cm2
]
Underground Detectors
Cosmic Rays
MW redone
MW Disk Disru
ption
XQC
IMP 7/8 IMAX
SKYLAB
RRS
COUPP 2007 result
Impliedσdm/mχ ≈4 cm2/g
≈ 7 × 10−24
cm2/GeV
Much largerthan limits ondark matter-nucleon crosssections
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
Fine-tuning required:Need to make self-interaction cross section orders of magnitudelarger than nucleon cross sectionSome simple models exist (e.g. Faraggi & Pospelov 2001)
Astrophysical constraints on self-interaction:For ρ ∝ r−n, CDM predicts n ≈ 1, SIDM n ≈ 0Observers disagree on the value of nMeasurement of n is a key goal of JACO
Other key problems can be worked out:Do n = 0 halos undergo core-collapse? (Kochanek & White 2000)Does the same σdm describe dwarf galaxies and clusters?
May require velocity-dependent cross-section (Davé et al. 2001)
SIDM may be an unlikely possibility, but is interesting and notconclusively ruled out by either data or theory
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
Fine-tuning required:Need to make self-interaction cross section orders of magnitudelarger than nucleon cross sectionSome simple models exist (e.g. Faraggi & Pospelov 2001)
Astrophysical constraints on self-interaction:For ρ ∝ r−n, CDM predicts n ≈ 1, SIDM n ≈ 0Observers disagree on the value of nMeasurement of n is a key goal of JACO
Other key problems can be worked out:Do n = 0 halos undergo core-collapse? (Kochanek & White 2000)Does the same σdm describe dwarf galaxies and clusters?
May require velocity-dependent cross-section (Davé et al. 2001)
SIDM may be an unlikely possibility, but is interesting and notconclusively ruled out by either data or theory
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Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
Fine-tuning required:Need to make self-interaction cross section orders of magnitudelarger than nucleon cross sectionSome simple models exist (e.g. Faraggi & Pospelov 2001)
Astrophysical constraints on self-interaction:For ρ ∝ r−n, CDM predicts n ≈ 1, SIDM n ≈ 0Observers disagree on the value of nMeasurement of n is a key goal of JACO
Other key problems can be worked out:Do n = 0 halos undergo core-collapse? (Kochanek & White 2000)Does the same σdm describe dwarf galaxies and clusters?
May require velocity-dependent cross-section (Davé et al. 2001)
SIDM may be an unlikely possibility, but is interesting and notconclusively ruled out by either data or theory
![Page 73: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/73.jpg)
Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
Fine-tuning required:Need to make self-interaction cross section orders of magnitudelarger than nucleon cross sectionSome simple models exist (e.g. Faraggi & Pospelov 2001)
Astrophysical constraints on self-interaction:For ρ ∝ r−n, CDM predicts n ≈ 1, SIDM n ≈ 0Observers disagree on the value of nMeasurement of n is a key goal of JACO
Other key problems can be worked out:Do n = 0 halos undergo core-collapse? (Kochanek & White 2000)Does the same σdm describe dwarf galaxies and clusters?
May require velocity-dependent cross-section (Davé et al. 2001)
SIDM may be an unlikely possibility, but is interesting and notconclusively ruled out by either data or theory
![Page 74: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/74.jpg)
Dark Matter and Violent Mergers Chain of slingshots or something more exotic?
The Abell 520 PuzzleDark matter self-interaction: how plausible is it?
Fine-tuning required:Need to make self-interaction cross section orders of magnitudelarger than nucleon cross sectionSome simple models exist (e.g. Faraggi & Pospelov 2001)
Astrophysical constraints on self-interaction:For ρ ∝ r−n, CDM predicts n ≈ 1, SIDM n ≈ 0Observers disagree on the value of nMeasurement of n is a key goal of JACO
Other key problems can be worked out:Do n = 0 halos undergo core-collapse? (Kochanek & White 2000)Does the same σdm describe dwarf galaxies and clusters?
May require velocity-dependent cross-section (Davé et al. 2001)
SIDM may be an unlikely possibility, but is interesting and notconclusively ruled out by either data or theory
![Page 75: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/75.jpg)
Summary
Summary
Clusters of galaxies offer exciting limits on dark matter and darkenergy propertiesWe will need to learn a lot of baryon physics along the wayThe JACO, CCCP, and LoCuSS projects will offer new constraintson vital astrophysical questions through
Joint analysis of lensing, SZ, X-ray, and dynamical dataMass models of relaxed clustersStudies of violent mergers such as Abell 520
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Summary
Upcoming workWhere are we headed?
Next few years: better dark matter constraintsDetailed modeling and simulations of Abell 520Final constraints from CCCP sample (30 clusters)Expansion to larger samples (e.g. LoCUSS, 100 clusters)Inclusion of dynamics, triaxiality, nonthermal effects, and stronglensing into JACO codebase
Next decade: era of precision cluster physicsPAN-STARRS, Large Synoptic Survey Telescope, SNAP: 105
clusters of galaxiesSPT, ACT surveys coordinated with weak lensing and X-raycampaignsInternational X-ray Observatory (IXO): advanced probes ofturbulence, cosmic ray heating, bulk motions, and othernonthermal effects
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Summary
Upcoming workWhere are we headed?
Next few years: better dark matter constraintsDetailed modeling and simulations of Abell 520Final constraints from CCCP sample (30 clusters)Expansion to larger samples (e.g. LoCUSS, 100 clusters)Inclusion of dynamics, triaxiality, nonthermal effects, and stronglensing into JACO codebase
Next decade: era of precision cluster physicsPAN-STARRS, Large Synoptic Survey Telescope, SNAP: 105
clusters of galaxiesSPT, ACT surveys coordinated with weak lensing and X-raycampaignsInternational X-ray Observatory (IXO): advanced probes ofturbulence, cosmic ray heating, bulk motions, and othernonthermal effects
![Page 78: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/78.jpg)
Summary
Upcoming workWhere are we headed?
Next few years: better dark matter constraintsDetailed modeling and simulations of Abell 520Final constraints from CCCP sample (30 clusters)Expansion to larger samples (e.g. LoCUSS, 100 clusters)Inclusion of dynamics, triaxiality, nonthermal effects, and stronglensing into JACO codebase
Next decade: era of precision cluster physicsPAN-STARRS, Large Synoptic Survey Telescope, SNAP: 105
clusters of galaxiesSPT, ACT surveys coordinated with weak lensing and X-raycampaignsInternational X-ray Observatory (IXO): advanced probes ofturbulence, cosmic ray heating, bulk motions, and othernonthermal effects
![Page 79: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/79.jpg)
Summary
Upcoming workWhere are we headed?
Next few years: better dark matter constraintsDetailed modeling and simulations of Abell 520Final constraints from CCCP sample (30 clusters)Expansion to larger samples (e.g. LoCUSS, 100 clusters)Inclusion of dynamics, triaxiality, nonthermal effects, and stronglensing into JACO codebase
Next decade: era of precision cluster physicsPAN-STARRS, Large Synoptic Survey Telescope, SNAP: 105
clusters of galaxiesSPT, ACT surveys coordinated with weak lensing and X-raycampaignsInternational X-ray Observatory (IXO): advanced probes ofturbulence, cosmic ray heating, bulk motions, and othernonthermal effects
![Page 80: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/80.jpg)
Summary
Upcoming workWhere are we headed?
Next few years: better dark matter constraintsDetailed modeling and simulations of Abell 520Final constraints from CCCP sample (30 clusters)Expansion to larger samples (e.g. LoCUSS, 100 clusters)Inclusion of dynamics, triaxiality, nonthermal effects, and stronglensing into JACO codebase
Next decade: era of precision cluster physicsPAN-STARRS, Large Synoptic Survey Telescope, SNAP: 105
clusters of galaxiesSPT, ACT surveys coordinated with weak lensing and X-raycampaignsInternational X-ray Observatory (IXO): advanced probes ofturbulence, cosmic ray heating, bulk motions, and othernonthermal effects
![Page 81: Multiwavelength Observations of Clusters of Galaxies · Multiwavelength Observations of Clusters of Galaxies Andisheh Mahdavi Department of Physics and Astronomy San Francisco State](https://reader036.vdocuments.us/reader036/viewer/2022062506/5f06643d7e708231d417c334/html5/thumbnails/81.jpg)
Summary
Abell 520, Weak gravitational lensing signal
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Summary
Abell 520, Weak gravitational lensing signalIndependent analysis of the data by Milkeraitis and van Waerbeke