Recent SZ observations and prospects for cluster surveys
Rüdiger Kneissl
UC Berkeley (Astronomy & Physics)
Distant cluster workshop, Schloss Ringberg, 27 October 2005
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• Examples of recent SZ cluster observations
– Baryon fraction and M-T relation from the VSA sample
– High sensitivity SZ observations (first AMI targets)
• Cluster searches
– Interferometer technique: AMI
– Multi-bolometer arrays: APEX-SZ
– Satellite by-product: Planck
• Outlook
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The VSA cluster sample: Coma, A1795, A399+A401, A478, A2142, A2244CONT: COMA C IPOL 33841.019 MHZ COMA-S test.ICL001.2PLot file version 1 created 28-MAY-2004 13:45:03
Cont peak flux = -2.4479E-01 JY/BEAM Levs = 3.021E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)13 02 01 00 12 59 58 57 56 55 54 53
29 00
28 30
00
27 30
CONT: A1795 IPOL 34096.665 MHZ A1795-6 T.08.ICL001.2PLot file version 3 created 20-MAY-2004 13:33:23
Cont peak flux = -2.0493E-01 JY/BEAM Levs = 3.500E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)13 51 50 49 48 47 46 45 44 43 42
27 30
00
26 30
00
CONT: A401 IPOL 33837.746 MHZ A401-6 T.075.ICL001.4PLot file version 3 created 20-MAY-2004 13:40:47
Cont peak flux = 1.5093E-01 JY/BEAM Levs = 4.000E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)03 00 02 59 58 57 56 55 54 53 52
14 00
13 30
00
12 30
A399
A401
CONT: A478 IPOL 32999.999 MHZ A478-4 T.16.ICL001.1PLot file version 3 created 20-MAY-2004 13:47:11
Cont peak flux = -1.3904E-01 JY/BEAM Levs = 3.200E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)04 15 14 13 12 11 10 09 08 07
11 00
10 30
00
09 30
CONT: A2142 IPOL 34068.122 MHZ A2142-7 T.1.ICL001.2PLot file version 4 created 20-MAY-2004 13:49:41
Cont peak flux = -1.7375E-01 JY/BEAM Levs = 3.800E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)16 01 00 15 59 58 57 56 55 54 53 52
28 00
27 30
00
26 30
CONT: A2244 IPOL 33834.418 MHZ A2244-5 T.19.ICL001.1PLot file version 4 created 20-MAY-2004 13:59:34
Cont peak flux = 6.6234E-02 JY/BEAM Levs = 2.600E-02 * (-10, -9, -8, -7, -6, -5, -4,-3, -2, -1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
DECLINATION (B1950)
RIGHT ASCENSION (B1950)17 06 04 02 00 16 58 56
35 00
34 30
00
33 30
Gas fraction measurement
Combined constraint:fg = 0.08
+0.06−0.04h
−1 (Lancaster et al.,astro-ph/0405582)
A mass - temperature relation
Agrees with X-ray determinations
Understanding LSZ - M relation, ie. M-T and fg, will be essential for the SZ surveys.
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Analysis
Cluster model: assume gas density King-profile with HSE giving total mass, eg. M200,
Mr =3βr3
r2c + r2
kT
µG
and gas mass Mg = 4πρg(0)r3c∫ r/rc0 (1 + x
2)−3β/2xdx, x = r/rc. Therefore
fg =Mg
Mrand also A = MrT
−3/2 =3βr3
r2c + r2
kT−1/2
µG
Radio sources: 41 radio source (400 > Sν > 20mJy; ∼ 3σ) simultaneously observedand subtracted from the data; preselecting all NVSS and GB6 sources with predictedfluxes > 50mJy within 2◦ radius and raster-scanning one square-degree with the Ryletelescope to S15GHz > 20mJy.
Bayesian Inference: P (Θ|data, H) = P (data|Θ, H)P (Θ|H)/P (data|H);characterisation of posterior PDF with Monte-Carlo approach; typically 10 Markovchains running in parallel using BAYESYS, evaluation in visibility (Fourier) space; weakpriors on rc, β, Mg, strong prior on Te.
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The Arcminute Micro-Kelvin Imager
10 3.7m (200 λ ∼ 3’) & 8 13m antennae, 12-18 GHz, Tsys = 25K
AMI Collaboration: R. Barker, P. Biddulph, D. Bly, R. Boysen, A. Brown, C. Clementson, M. Crofts, T.
Culverhouse, J. Czeres, R. Dace, R. D’Alessandro, P. Doherty, P. Duffett-Smith, K. Duggan, J. Ely, M.
Felvus, W. Flynn, J. Geisbuesch, K. Grainge, W. Grainger, D. Hammet, R. Hills, M. Hobson, C. Holler, R.
Jilley, M. Jones, T. Kaneko, R. Kneissl, K. Lancaster, A. Lasenby, P. Marshall, F. Newton, O. Norris, I.
Northrop, G. Pooley, V. Quy, R. Saunders, A. Scaife, J. Schofield, P. Scott, C. Shaw, A. Taylor, D.
Titterington, M. Velic, E. Waldram, S. West, B. Wood, G. Yassin, J. Zwart
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IF system: downconverters, amplifiers, filters, path compensator, gain control units for6–12 GHz.
Correlator:
• 16-lag analogue correlator → 8 complex frequency channels
• detect phase-switched power with Schottky diodes
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First AMI cluster detections - high sensitivity SZ observations
13.0 14.0 15.0 16.0 17.0 18.0Channel Centre Frequency (GHz)
2.0
3.0
4.0
5.0
6.0
Inte
grat
ed S
Z flu
x (−
mJy
)
Spectrum of SZ effect in A1914
A1914 (astro-ph/0509215; Accepted A773 (6h observation)for publication in MNRAS Letters)S = -8.6 mJy, noise = 0.2 mJy/beam
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Cluster survey in the presence of primordial CMB
Grayscale image: Virgo cluster positions with scaled β model clusters, plus CMBContour overlay: 6 months survey, 2 arcmin resolution. Sources subtracted!
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Sensitivity and CMB Confusion
Thermal flux sensitivity (6 × 8-hours; within a 21 arcmin aperture) of the compact array3.7-m and large array 13-m dishes compared to primordial CMB and 4 clusters withmasses of M = 2 / 5 ×1014M� and at redshifts z = 0.15/0.8.
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SZ selection function
Melin, Bartlett, Delabrouille2005, A&A 429, 417
Culverhouse(Moriond 2004)
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Cluster masses and redshifts
RK et al. 2001
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Imaging cluster substructureConstruction phase 3: Compactifying the Ryle telescope
current wideEast-Westalignment
Hydrosimulation:5× 1014 M� mergingcluster at z = 0.155.
morecompact
array withimproved
North-South
resolution
high declination (45 deg)
low declination (-5 deg)
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Pointed high redshift cluster observations
Cluster merger at redshift 1.5 of totalmass 2 × 1014 M� from a hydrody-namical simulation (G. Tormen); iny-units of 10−6.
Simulated 14 × 8−h observation withcompact array and Ryle mosaic; in µJybeam−1.
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The SZ receiver for the APEX telescopeMPIfR Bonn & UC Berkeley
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People:
Max Planck Institute for Radioastronomy:
K. Basu, F. Bertoldi (U Bonn), R. Güsten, E. Kreysa, K. Menten, D. Muders, P. Schilke
MPE: H. Böhringer
University of California, Berkeley
Physics Department: H.-M. Cho, N. W. Halverson (U Colorado), W. L. Holzapfel, R.Kneissl, T. M. Lanting, A. T. Lee, M. Lueker, J. Mehl, T. Plagge, P. L. Richards, D.Schwan, M. White
LBNL: M. Dobbs (U McGill), H. Spieler
• 12 m Atacama Pathfinder Experiment telescope, on-axis Cassegrain
• 0.75 m secondary, tertiary optics, 0.4 degree field-of-view
• Spiderweb Transition-Edge Sensor bolometer array with 330 elements
• SQUID readout, frequency multiplexing for SPT
• dry (τ = 0.061 at 225 GHz), high elevation (5000 m) site, 23◦S latitude
• observing frequencies (90) 150 (217) GHz
• 100-200 deg2, several months integration, 10 µK, 60” FWHM ( 150 GHz) resolution
Observing strategy
Optimise scanning speed, cross-linking, field size, geometry, etc.
Science goals / cluster yield with APEX-SZ
• Evolution of cluster mass function• Cluster correlation function• Evolution of gas fraction and M-T re-
lation• Dark matter density and distribution• Dark energy equation of state• Population of inverted spectrum radio
sources• High redshift star forming galaxies• Density-velocity field correlations• Lensing of the cosmic microwave
background
SZ / X-ray cluster selection
Planck all-sky CMB (and cluster) component separation(Stolyarov et al. 2002)
Input component maps Recovered power spectra
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Towards a complete and pure Planck cluster sample
Geisbüsch, RK, Hobson, 2005, MNRAS 360, 41
• Virgo HVLC catalogues (Sphere, Octants, ’Evrard mass function’)
• ΛCDM and τCDM cosmologies
• rescaling of cluster catalogue with σ8
• M − T relation with different normalisation (virial + ’X-ray’)
• analytic isothermal gas profile truncated at rv (90 % unresolved clusters)
• assume constant gas fraction fg
• assume NFW profile to rescale dark matter mass definitions
• fix total cluster flux, ’adjust’ central density and rc/rv
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Recovered cluster fluxes
ΛCDM: σ8 = 1 (virial) ΛCDM: σ8 = 0.7 (virial) ΛCDM: σ8 = 0.7 (xnorm)
Scatter, completeness and purity for a variety of cosmological SZ realisations.
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Mass function and completeness in redshift bins
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Outlook
• First generation (testing) SZ survey instruments (interferometers) beginning to takedata: SZA, AMI (known clusters until spring 2006, surveys from summer), limitedby radio source confusion until large telescopes, e.g. Ryle array, become available.
• Second generation (fast surveying), large bolometer arrays on single telescope,starting soon, e.g. APEX-SZ engineering run this year, full commissioning spring2006.
• High sensitivity SZ cluster data are very interesting to explore gas physics
• SZ will provide high-z clusters to study evolution and large samples to constraincosmology, hopefully with advantageous selection
• Multi-wavelength (optical,IR,X-ray,radio,sub-mm) (pre-)follow-up important
• Third generation (digesting) SZ instruments (high resolution imaging, SZspectroscopy)
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