clusters of galaxies cosmology - lund observatory · galaxies. there is a “clusters” working...

CLUSTERS of GALAXIES &

COSMOLOGY

Cathy Horellou, Onsala Space Observatory, Chalmers University of Technology, Sweden

Introduction

– Clusters as cosmological tools

– Probes, processes,

& the importance of systematics

Sunyaev-Zelʼdovich observations

Radio synchrotron from clusters (LOFAR...)

XXL: The Ultimate XMM Extragalactic Survey

My own interests

Tuesday, February 5, 2013

Vikhlinin et al. 2009 Tuesday, February 5, 2013

Credit: The Virgo consortium, 1996

Observations of clusters make it possible to– measure the growth of structure in the expanding Universe– constrain the cosmological parameters

Ex: The observation of 1 single massive cluster at z = 0.8 (MS1054-0321) made it possible to exclude Ωm > 1 (Jetlema et al. 2001)

Ωm = 1

Numerical simulations of structure formation (dark matter only)

170 Mpc

200 Mpc

Ωm = 0.3ΩΛ = 0.7


Figure: Horellou & Berge 2005, MNRAS

Cluster number countsin different dark energy models

w = p/ρ : equation-of-state parameter of dark energyw = – 1 (ΛCDM)w = – 0.8w = – 0.6

A constant limiting mass was assumed.

To relate observations to models, it is importantto know the selection function of the survey,

and the Mass-Observable relation


• Velocity dispersion of cluster galaxies + virial theorem

• Hot gas in equilibrium with the gravitational

• Gravitational lensing (strong + weak lensing)

⇒ Total mass: a few times 1013 to 1015 Msun

• Scaling relations M - Observable

85%

10%5%

GalaxiesHot gasDark matter

kBTe !

!

GMmp

2Re!

"

! 7

!

M

3 " 1014M!

" !

Re!

1Mpc

""1

keV

1

Cluster masses


Mass

LX

TX

YSZ

N200

σV

Lensing mass

Optical/NIR

X-ray

mm-radio

Scaling relations: Mass – Observable


Constrain cosmologically-relevant quantities & the cosmological model with clusters:

- Clusters are natural TELESCOPES (Gravitational lenses to probe the high-z Universe)

- Number counts n(M,z)+ 2-point correlation function ξ(M,z) ➜ CosmoParams, neutrino mass,

non-Gaussianity, ...

- Baryon mass fraction in virialized clusters (Allen et al. 2011) ➜ CosmoParams...

- SZ: – Thermal SZ + X-rays of virialized clusters: DA(z) ➜ H0 – Kinetic SZ: Peculiar velocities ➜ CosmoParams... – TCMB(z ≠ 0). ➜ Standard law TCMB = T0(1+z), or more exotic model?

- Dark matter:

– Merging clusters ➜ Constraints on the properties of DM (self-interaction cross-section)– DM annihilation ➜ secondary electrons ➜ SZ signature

➜ gamma rays- Cosmic magnetic fields (LOFAR/SKA) via observations of polarized emission and of

Faraday Rotation Measures (∝∫ neB// dl) of background sources (tomography)Tuesday, February 5, 2013

B

Relat. e-

Th. e-

p

Radio synchrotron

X-ray (Bremsstrahlung)

γCMB

γCMB

γCMB

Th. e-SZ

(Inverse Compton scattering)

γCMB

γCMB

γCMB

π0

γ+γ Gamma rays

Dark matter

Thermal e- (keV), suprathermal e- (>10 keV), relativistic e- (power-law, MeV-GeV)

BRadio Faraday rotation

(∝∫ neB// dl)

Relat. e-γCMB

X/Gamma(Inv. Compton)

Th. e-

π0


THE SUNYAEV-ZELʼDOVICH EFFECT &

SZE OBSERVATIONS of CLUSTERS

Picture: Sheldonʼs and Lennartʼs white board in the TV series The Big Bang Theory

x = hν/kT

The Compton parameter y

y ∝∫ neTe dl ∝∫ Pe dl

y is dimensionless

We measure Y = ∫ y dΩin units of solid angle (sr, arcmin2)

Y is tightly related to the Mass!

The Kompaneets equationChange in the photon occupation number ∆n


Zelʼdovich & Sunyaev 1969; Reviews by Birkinshaw 1999; Carstrom et al. 2002

APEX

-SZ

LABO

CA

The SZ effect: Inverse Compton scattering of CMB


1. Thermal SZ effect

Decrement in the radio/mm, increment in the submm

ΔTSZ,th/TCMB(ν) ∝∫clusterneTedl = gas pressure

2. Kinetic SZ effect: ~10 times weaker

ΔTSZ,kin/TCMB(ν) ∝-vpec/c

Depends on the mass of the intracluster gas.

Current observations are sensitive to clusters with masses M > a few 1014 Msun.

Important: independent of redshift!

3. Relativistic SZ effect(High Te, high frequencies)

Characteristic distortions of the CMB spectrum:

APEX

-SZ

LABO

CA


Planck observation of Abell 2319 at z = 0.056 (DL = 236 Mpc)Image Credit: ESA / HFI & LFI Consortia

2 degrees

The Planck Early Science SZ catalog: 189 clusters (incl. 20 new)(the Planck Collaboration 2011, A&A)

Angular resolution: 24ʼ to 5ʼ


Reichardt et al. 2013

South Pole TelescopeAngular resolution 1ʼ

150 + 95 GHz

Planck: Beam dilution

ROSAT: Cosmological dimming

224 cluster candidatesin 720 deg2 (out of 2500 deg2),

158 confirmed in opt/NIR.Median z = 0.55

Mlim = 5 1014/h Msun at z > 0.6


APEX-SZPI: Adrian Lee

• Mapping the SZ decrement at 2 mm (150 GHz)

• Angular resolution of 1ʼ; FOV = 24ʼ

• Observations between 2005 and 2010

• 48 clusters + 2 deep fields.

Dec 2009Tuesday, February 5, 2013

Example of APEX-SZ 150 GHz maps (Schwan et al. 2012, The ESO Messenger)


The Bullet Cluster at z = 0.3

Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.

Hot gas (X-ray)

Dark matter (lensing)

Galaxies


The Bullet Cluster as a gravitational lens (Johansson, Horellou et al. 2010, A&A)

• 17 submm galaxies (APEX-LABOCA 870 micron map)

• The brightest one is a z = 2.8 galaxy located near a caustic line and magnified ~ 100 times

Red:Total mass distribution (Weak lensing from Clowe et al.)Red: X-ray (XMM)


The Bullet Cluster at z = 0.3

Star: Bright submm galaxy (50 mJy at 870 micron, Johansson et al. 2010) at z=2.8 near a critical line of the Bullet Cluster and magnified 100 times; its flux at 2 mm is negligible compared to the SZ

SZ decrement (APEX-SZ, 2mm): Halverson et al. 2009

SZ increment (LABOCA, 870 micron): Horellou et al., in prep

Contours: X-rayColors: SZ, resolution 27”

Substructure in the SZ, offset from the X-ray

Contours + Colors: SZ, resolution 1.4ʼ


The SZE spectrum

Abell 2163 at z = 0.3, Nord et al. 2009

Fixing temperature gives constraint on peculiar velocity-central Compton

parameter

vpec,los = –140 ± 460 km s−1,


Abell 2163 at z = 0.3, Nord et al. 2009

De-projected density & temperature

Joint X-ray/SZ analysis:

SZ: ∫losneTe dl

X-ray: ∫losne2

Lambda(Te) dl

Assuming spherical symmetry, one can use the Abel transformation

ne

Te


De-projected density & temperatureProfile of the enclosed gas mass and the total mass

(assuming hydrostatic equilibrium)

Abell 2204, a relaxed cluster at z = 0.15, Basu et al. 2010

ne

Te

Mgas (<R)

Mtot (<R)

fgas (<R)


APEX-SZ scaling relations Bender et al., in prep

The integrated Compton parameter YSZ is a good proxy of the clusterʼs total mass (e.g. Motl et al. 2006, Arnaud et al. 2010)

Y500


Lensing follow-up of the 15 clusters of our sample for which no weak lensing data exist

Ongoing PhD work of Matthias Klein, BonnBVR observations with the wide field imager (WFI) on the ESO/

MPG 2.2 m telescope in La Silla, FOV = 33ʼx34ʼ

Photo: www.eso.org

M200 = 11.4 (+2.5 -2.2) x 1014 Msol R200 = 1.96 +/- 0.13 Mpc

RXC 0532

S/N map of the reconstructed projected mass and shear profile


http://www.eso.org

http://www.eso.org

RADIO SYNCHROTRON OBSERVATIONS of CLUSTERS, LOFAR

The Onsala LOFAR stationCredit: Onsala Space Observatory/Leif Helldner


Figure: Radio halo of the Bullet Cluster (grey)+ X-ray surface brightness contours (Liang et al. 2000) after subtraction of the radio point sources

• Synchrotron emission on Mpc scale• Low surface brightness:

~3 mJy/arcmin2 at 1.4 GHz• Steep spectrum (α < –1, Sν ~να)⇒ brighter at lower frequencies

• Unpolarized

Detected in ~30% of X-ray clusters (Ferretti et al. 2012)

Origin of the relativistic electrons?

Accelerated in turbulence generated in mergers (e.g. Brunetti 2001)?

Giant radio halos in (some) galaxy clusters


Feretti et al. 2012Tuesday, February 5, 2013

2 Mpc long radio relic in the z= 0.19 Sausage Cluster

(van Weeren et al. 2010, Science)


The radio–X-ray correlation

Figure: Brown et al. 2011, ApJRed points: Detection of radio signal at 843 MHz by stacking ~100 clusters

Bi-modality

ON!

OFF!?


The radio–X-ray correlation

Figure: Brown et al. 2011, ApJRed points: Detection of radio signal at 843 MHz by stacking ~100 clusters

Bi-modality

ON!

OFF!

What about lower X-ray luminosity clusters/groups? ➜ XXL

?

?


61-67 MHz LOFAR map

Field around Abell 2256: resolution 80”

Inset: resolution 22”x26”

van Weeren et al. 2012 A&A

First LOFAR results: Abell 2256 at 8 - 67 MHz.


z=0.0594


LOFAR expectations for radio halosSo far: only about 50 radio halos are detected (VLA, GMRT).

The LOFAR all-sky survey at 120 MHz is expected to detect about 350 giant radio halos at z < 0.6 (Cassano et al. 2010 A&A).

Relation to mergers?

Population of CR electrons

Magnetic field via Rotation Measure Synthesis of polarized background/cluster galaxies.

There is a “Clusters” working group in the “Surveys” Key Science Project (KSP) (PIs Brueggen & Brunetti)

“Magnetism” KSP: Plan to search for polarization from galaxies (isolated/in groups and clusters, star-forming, AGN) and from the cosmic web of filaments.


die Kunst !

Über!

in der Wissenschaft!" Kandinsky!

PI: Marguerite Pierre (Saclay, France)Consortium of ~100 researchers!

The largest XMM project ever

2 x 25 deg2

Equatorial field CFHT-LS, RA = 2h23, DEC=-5dSouthern field BCS, RA=23h30, DEC=-55d

10 ksec per pointing

Extension of the XMM-LSS (Pacaud et al.ʼ06; 5.5 deg2; Chiappetti et al.ʼ12, 11.1 deg2),

C1 clusters: 5-6 /deg2

C2 clusters (50% complete): 12/deg2

XXL is expected to detect ~50 clusters at z > 1and more than 500 clusters in total,

+ 10 000 AGN.

Constrain the evolution of equation-of-state parameter w(z) of dark energy.


XXL equatorial field:extension of XMM-LSS field

Blue: existing dataRed: new observationsYellow: observations from other programsBlack rectangle: VIPERS spectroscopy


XXL Southern field:extension of XMM-BCS field

Blue, cyan, magenta: existing dataRed: new observationsYellow: observations from other programsBlack: Optical spectroscopy

Δα = Δδ= 20ʼ (Δα = Δδ = 23’ in the initial central survey)


From Pierre et al. 2011, MNRAS

Cosmological predictions for the XXL surveyw(z) = w0 + wa z/(1+z)

w(a) = w1 + w2 a, where a= 1/(1+z)


Frequency Telescope Area Resolution Largest angular scale

Detection limit (5σ) Reference

1.4 GHz VLA (NVSS) All sky δ > –40o 45” 15ʼ 2.5 mJy/bCondon et al.

1998

1.4 GHz VLA (FIRST) All sky δ > –40o 5” 2ʼ 0.15 mJy/b Becker et al.

610 MHz GMRT 12.7 deg2 6.5” 6.9ʼ 1.5 mJy/b Tasse et al. 2007

325 MHz VLA 15.3 deg2 6.7” 4 mJy/b Tasse et al. 2006

240 MHz GMRT 18 deg2 14.7” 11.5ʼ 12.5 mJy/b Tasse et al. 2007

74 MHz VLA 132 deg2 30” 20ʼ 160 mJy/bCohen et al.

2003 Tasse et al. 2006Tasse et al 2006

Existing radio observations of the XXL equatorial field


Radio observations of XXL

Main goals: Evolution of AGN and cluster-scale radio emission

Equatorial field (at DEC = –5 deg)

* Observed with LOFAR in January (PI Ph. Best)

* GMRT 610 MHz proposal accepted (PI S. Raychaudhury)5” resolution. Point-like sources versus extended emission?

* Jansky VLA (PI V. Smolcic)

Test data 3 GHz, 2 deg2

Future: Map the whole equatorial field at 2-4 GHz, 2” resolution.

Southern field:

* ATCA (PI V. Smolcic)Pilot proposal accepted (5.5 deg2). 2.1 GHz (BW 2 GHz), 15-20 μJy/beam rms


mm observations of XXL

Main goal: Sunyaev-Zeldovich observations of clustersEquatorial field

* Covered by ACT* Plans to start a systematic SZ follow-up of the most massive/distant clusters* CARMA observations of a few high-z clusters PIs: Adam Mantz, Tom Plagge (Chicago)

* APEX-SZ 2 mm observations of 0.75 deg2 of XMM-LSS, centered on XMM LSS-006, M500 = 1.9 1014 h-1 Msun

Second cluster detected10 μK rms in the central 0.25 deg2

PI: Florian Pacaud (Bonn)

Southern field* Covered by SPT

Figure: APEX-SZ map of XMM-LSS

~50ʼTuesday, February 5, 2013

Conclusion– Clusters are at the crossroad of astrophysics & cosmology:

they are complex individuals and the sites of interesting physical processes;

yet they are rather simple and share common fundamental properties

– To use clusters in cosmology it is essential to understand their astrophysics

– Fortunately, there are/will be new instruments able to measure the tiny signals from clusters, from gamma-rays to radio

– This is a unique time in history...

– ...but with great power comes great responsability (to figure it all out!)


clusters of galaxies cosmology - lund observatory · galaxies. there is a “clusters” working...

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