Post on 01-Apr-2015
Science at Q band
SZ/CMB models:Q-band science
Mark Birkinshaw
University of Bristol
15 September 2009 Mark Birkinshaw, U. Bristol 2
Science at Q band
1. Simple observables: shape
SZ effects – from inverse-Compton scattering by hot electrons on cold CMB photons.
Thermal SZ effect – los amplitude Comptonization parameter, ye, the dimensionless electron temperature weighted by the scattering optical depth
15 September 2009 Mark Birkinshaw, U. Bristol 3
Science at Q band
Simple observables: shape
2
3
2
1
2
2
0 1)(
cee yy
For a simple isothermal model
• typical central value ye0 10-4
• SZ effect has angular size about 3 × X-ray angular size for ~ 0.7 (typical for rich clusters)
• at z = 0.2, θc~ 1 arcmin for rich cluster
15 September 2009 Mark Birkinshaw, U. Bristol 4
Science at Q band
Simple observables: spectrum
• spectrum related to gradient of CMB spectrum
• zero near CMB peak (about 220 GHz)
• flux density effect small at long λ
Q
15 September 2009 Mark Birkinshaw, U. Bristol 5
Science at Q band
Simple observables: spectrum
If the cluster is moving, then in the cluster frame the CMB is anisotropic. Scattering isotropizes it by an amount evz, giving kinematic SZE.
Angular shape same as thermal SZ effect, if cluster is isothermal.
Spectrum differs from thermal SZ effect, but same shape as the spectrum of primordial CMB fluctuations, so velocity information is obtained contaminated by the (lensed) primordial CMB.
15 September 2009 Mark Birkinshaw, U. Bristol 6
Science at Q band
Simple observables: kinematic SZE
• spectrum related to gradient of CMB spectrum
• no zero• small compared to
thermal effect at low frequency
• flux density effect small at long λ
• confused by primordial structure
Q
15 September 2009 Mark Birkinshaw, U. Bristol 7
Science at Q band
2. Simple observations
Simplest: single-dish radiometers/radiometer arrays.
Secondary focus:• single on-axis feed• symmetrical dual feeds• array of feeds (large focal plane)
• e.g., OCRA series
Prime focus:• single on-axis feed• symmetrical dual feeds
15 September 2009 Mark Birkinshaw, U. Bristol 8
Science at Q band
Lancaster et al. (2009; in preparation)• 34 highest LX clusters from ROSAT BCS
(Ebeling et al. 1998) at z > 0.2• ‘fair’ sample with few biases• Complete subset of 18 with Chandra data• Study scaling relations: decode surveys• Statistically useful cluster parameters• OCRA-p on Toruń 32-m (OCRA-F now,
OCRA-C possible)• noise ~ 0.4 mJy [less than 1 hour/cluster]
Sample studies (X-ray/optical selection)
15 September 2009 Mark Birkinshaw, U. Bristol 9
Science at Q band
Source contamination
SZ effects evident in most clusters before source correction – compare cluster and trail statistics.
Uncorrected: lose 20% of clusters.Corrected (GBT): lose 10% of clusters (lose 5% of trails).
15 September 2009 Mark Birkinshaw, U. Bristol 10
Science at Q band
Scaling relation: flux density/X-ray kT
consistent with expected 3/2 scaling relation
15 September 2009 Mark Birkinshaw, U. Bristol 11
Science at Q band
Next step: blind survey
Potential field: XMM-LSS. Survey blind in SZ, provides parallel X-ray, lensing, IR data.
Too far south for Toruń: accessible to AMiBA.
15 September 2009 Mark Birkinshaw, U. Bristol 12
Science at Q band
AMiBA-13
Partially-completed AMiBA-13 interferometer on Mauna Loa (baselines to 6.5 m).
Larger antennas than in first AMiBA season.
90 GHz: would need a larger system at 30 GHz.
15 September 2009 Mark Birkinshaw, U. Bristol 13
Science at Q band
SZ effect confusion on CMB
Figure from Molnar & Birkinshaw 2000
thermal SZ
kinematic SZ
RS effect
15 September 2009 Mark Birkinshaw, U. Bristol 14
Science at Q band
Sensitivity of radiometer
Single-dish and interferometers need to use switching strategies or extra filtering. Beam-switching + position-switching, or scanning for single dishes. Multi-field differencing or fringe rate filtering for interferometers.
2sys
A
TNT
(N > 1), but TA doesn’t reduce with time as -1/2 after some time: unsteady gain and Tsys etc.
15 September 2009 Mark Birkinshaw, U. Bristol 15
Science at Q band
Simple observations: z dependence
Angular size and separation of beams leads to redshift dependent efficiency
Shape of curve shows redshift of maximum signal, long plateau.
Similar for all types of observation.
15 September 2009 Mark Birkinshaw, U. Bristol 16
Science at Q band
Simple observations: interferometers
SZA (2008)
15 September 2009 Mark Birkinshaw, U. Bristol 17
Science at Q band
Simple observations: interferometer sensitivity
Sensitivity of interferometer
synth
source
corr
sys
N
TT
Ncorr = number of antenna-antenna correlations used in making synthesized beam (solid angle synth). source = solid angle of source. Built-in rejection of many systematic errors.
15 September 2009 Mark Birkinshaw, U. Bristol 18
Science at Q band
Simple observations: angular dynamic range
• restricted angular dynamic range set by baseline and antenna size
• good rejection of confusing radio sources (use long baselines)
• even tightly packed arrays trade sensitivity for resolution Abell 665 model, VLA observation
available baselines
15 September 2009 Mark Birkinshaw, U. Bristol 19
Science at Q band
Simple observations: interferometer maps
• restricted angular dynamic range
• high signal/noise (long integration possible)
• clusters easily detectable to z 1
• better for structure studies?
Carlstrom et al. 1999
15 September 2009 Mark Birkinshaw, U. Bristol 20
Science at Q band
3. Simple science results
• Integrated SZ effects– total thermal energy content– total hot electron content
• SZ structures– not as sensitive as X-ray data– need for gas temperature
• Mass structures and relationship to lensing
• Radial peculiar velocity via kinematic effect
15 September 2009 Mark Birkinshaw, U. Bristol 21
Science at Q band
Simple science results: integrated SZE
Total SZ flux density
thermaleeRJ UdzTndS Thermal energy content immediately measured in redshift-independent wayVirial theorem: SZ flux density should be good measure of gravitational potential energy
15 September 2009 Mark Birkinshaw, U. Bristol 22
Science at Q band
Simple science results: integrated SZE
Total SZ flux density
eeeeRJ TNdzTndS With X-ray temperature, SZ flux density measures electron count, Ne (hence baryon count) and total gas mass
Combine with X-ray derived mass to get fb
15 September 2009 Mark Birkinshaw, U. Bristol 23
Science at Q band
Some rough Q-band numbers
These total flux densities are integrated out to the virial radius: most observations cannot go out that far.Note that the total flux densities are highly distance dependent – the detectable signals in a single beam (radiometer/interferometer) are less so because of the z-dependence of the efficiency.
15 September 2009 Mark Birkinshaw, U. Bristol 24
Science at Q band
Simple science results: SZE and lensing
Weak lensing measures ellipticity field e, and so
)(),(1 2
crit θθθθ ii ed
Surface mass density as a function of position can be combined with SZ effect map to give a map of fb SRJ/
15 September 2009 Mark Birkinshaw, U. Bristol 25
Science at Q band
Simple science results: total, gas masses
Inside 250 kpc:
XMM +SZ
Mtot = (2.0 0.1)1014 M
Lensing
Mtot = (2.7 0.9)1014 M
XMM+SZ
Mgas = (2.6 0.2) 1013 M
CL 0016+16 with XMMWorrall & Birkinshaw 2003
15 September 2009 Mark Birkinshaw, U. Bristol 26
Science at Q band
z=0.68z=0.68z=0.58
z=0.73
z=0.14
z=0.14
z=0.29
z=0.25
z=0.25
Noise dominated region
××
4.5
4.25
pixel data from simulations
clusters identified in simulations
Lensing and the thermal SZ effect
15 September 2009 Mark Birkinshaw, U. Bristol 27
Science at Q band
Simple science results: vz
• Kinematic effect separable from thermal SZE by different spectrum
• Confusion with primary CMB fluctuations limits vz accuracy (typically to 150 km s-1)
• Velocity substructure in atmospheres will reduce accuracy further
• Statistical measure of velocity distribution of clusters as a function of redshift in samples
15 September 2009 Mark Birkinshaw, U. Bristol 28
Science at Q band
3. Simple science results: vz
Need• good SZ spectrum• X-ray temperature
Confused by CMB structure
Sample vz2
Errors 1000 km s so far
A 2163; figure from LaRoque et al. 2002.
15 September 2009 Mark Birkinshaw, U. Bristol 29
Science at Q band
3. Simple science results: cosmology
• Cosmological parameters– cluster-based Hubble diagram– cluster counts as function of redshift
• Cluster evolution physics– evolution of cluster atmospheres via cluster counts – evolution of radial velocity distribution– evolution of baryon fraction
• Microwave background temperature elsewhere in Universe
15 September 2009 Mark Birkinshaw, U. Bristol 30
Science at Q band
3. Simple science results: cluster distances
X-ray surface brightness
SZE intensity change
Eliminate unknown ne to get cluster size L, and hence distance or H0
LTn eeX2/12
LTnI ee
2/320
2/312
eXL
eX
TIH
TIL
15 September 2009 Mark Birkinshaw, U. Bristol 31
Science at Q band
Simple science results: cluster distances
CL 0016+16
DA = 1.36 0.15 Gpc
H0 = 68 8 18 km s-1 Mpc-1
Worrall & Birkinshaw 2003
15 September 2009 Mark Birkinshaw, U. Bristol 32
Science at Q band
Simple science results: cluster Hubble diagram
• poor leverage for other parameters
• need many clusters at z > 0.5
• need reduced random errors
• ad hoc sample • systematic errors
Carlstrom, Holder & Reese 2002
15 September 2009 Mark Birkinshaw, U. Bristol 33
Science at Q band
Simple science results: SZE surveys
• SZ-selected samples– almost mass limited and orientation independent
• Large area surveys– 1-D interferometer surveys slow, 2-D arrays better– radiometer arrays fast, but radio source issues– bolometer arrays fast, good for multi-band work
• Survey in regions of existing X-ray/optical surveys– Expect SZ to be better than X-ray at high z
15 September 2009 Mark Birkinshaw, U. Bristol 34
Science at Q band
Simple science results: fB
SRJ Ne Te
Total SZ flux total electron count total baryon content.Compare with total mass (from X-ray or gravitational lensing) baryon mass fraction
Figure from Carlstrom et al. 1999.
b/m
15 September 2009 Mark Birkinshaw, U. Bristol 35
Science at Q band
4. More complicated observables• Detailed structures
– Gross mass model– Clumping– Shocks and cluster substructures
• Detailed spectra– Temperature-dependent/other deviations from
Kompaneets spectrum– CMB temperature
• Polarization– Multiple scatterings– Velocity term
15 September 2009 Mark Birkinshaw, U. Bristol 36
Science at Q band
Detailed structures
Clumping induced by galaxy motions, minor mergers, etc. affects the SZE/X-ray relationship
More extreme structures caused by major mergers, associated with shocks, cold fronts
Further SZE (density/temperature-dominated) structures associated with radio sources (local heating), cooling flows, large-scale gas motions (kinematic effect).
SZ effects are more relatively sensitive to outer parts of clusters than X-ray surface brightness.
15 September 2009 Mark Birkinshaw, U. Bristol 37
Science at Q band
Detailed structures
J0717.5+3745
z = 0.548
Clearly disturbed, shock-like substructure, filament
What will SZ image look like?
15 September 2009 Mark Birkinshaw, U. Bristol 38
Science at Q band
Detailed structures
Bullet cluster, Laboca (extensively filtered).High-frequency structure affected by bright point sourceMany other point sources; SZ effect also detected – easier in Q band, probably.
(Lopez-Cruz et al.)
15 September 2009 Mark Birkinshaw, U. Bristol 39
Science at Q band
Detailed spectra
• Ratio of SZ effects at two different frequencies is a function of CMB temperature (with slight dependence on Te and cluster velocity)
• So can use SZ effect spectrum to measure CMB temperature at distant locations and over range of redshifts
• Test TCMB (1 + z)
Battistelli et al. (2002)
15 September 2009 Mark Birkinshaw, U. Bristol 40
Science at Q band
• for low-Te gas effect is independent of Te
• Te > 5 keV, spectrum is noticeable function of Te
• non-thermal effect (high energies) gives distortion
• multiple scatterings give another distortion
• hard to measure
5 keV15 keV
Detailed spectra
15 September 2009 Mark Birkinshaw, U. Bristol 41
Science at Q band
Polarization
Polarization signals are O(z) or O(e) smaller than the total intensity signals: this makes them extremely hard to measure.
Interferometers help by rejecting much of the resolved signal, since some of the polarization signal has smaller angular size than I.
Still need excellent common-mode rejection to remove systematic errors in polarization.
15 September 2009 Mark Birkinshaw, U. Bristol 42
Science at Q band
5. Requirements on observations
Use Size (mK) Critical issues
Energetics 0.50 Absolute calibration
Baryon count 0.50 Absolute calibration; isothermal/spherical cluster; gross model
Gas structure 0.50 Beamshape; confusion
Mass distribution 0.50 Absolute calibration; isothermal/spherical cluster
Hubble diagram 0.50 Absolute calibration; gross model; clumping; axial ratio selection bias
15 September 2009 Mark Birkinshaw, U. Bristol 43
Science at Q band
Requirements on observations
Use Size (mK) Critical issues
Blind surveys 0.10 Gross model; confusion
Baryon fraction evolution
0.10 Absolute calibration; isothermal/spherical cluster; gross model
CMB temperature
0.10 Absolute calibration; substructure
Radial velocity 0.05 Absolute calibration; gross model; bandpass calibration; velocity substructure
15 September 2009 Mark Birkinshaw, U. Bristol 44
Science at Q band
Requirements on observations
Use Size (mK) Critical issues
Cluster formation 0.02 Absolute calibration
Transverse velocity
0.01 Confusion; polarization calibration
15 September 2009 Mark Birkinshaw, U. Bristol 45
Science at Q band
6. Status of SZ effects
• Hundreds of cluster detections– many high significance (> 10) detections– multi-telescope confirmations– poor interferometer maps, structures usually from
X-rays
• Spectral measurements still rudimentary – no kinematic effect detections
• Preliminary blind and semi-blind surveys– a few detections (not at Q band, yet)
15 September 2009 Mark Birkinshaw, U. Bristol 46
Science at Q band
Status at the time of early ALMA• 10 × more cluster detections
– Planck catalogue, low-z not yet available– high-resolution surveys (AMiBA-13, SZA, SPT, APEX-SZ,
etc.; Q-band selected fraction?)• About 100 images with > 100 resolution elements
– mostly interferometric, tailored arrays, 10 arcsec FWHM– some bolometric maps, 15 arcsec FWHM– angular dynamic range, structure indications poor
• A few integrated spectral measurements – Still confusion limited– Still problems with absolute calibration
15 September 2009 Mark Birkinshaw, U. Bristol 47
Science at Q band
ALMA possibilities
• Q band good for SZ studies– ALMA: 1 μJy in 10 arcsec FWHM over 145 arcsec
primary beam in 12 hours: cluster substructure mapping with main array (loses largest scales)
– quality of mosaics?– 7-m antennas in compact configuration more
effective on angular scales of most interest • Blind surveys using ALMA band-1 not likely – wrong
angular scales (OCRA-F/AMiBA/APEX-SZ/…)• Fortunately, Chandra and XMM-Newton still working
15 September 2009 Mark Birkinshaw, U. Bristol 48
Science at Q band
Possible SZ unique studies• Hot outflows around ionizing objects at recombination
(or later) may show kinematic with little thermal SZ.• SZ spectral inversion into electron distribution
function – 100-400 GHz range critical. • Information on developing cluster velocity field.• Non-thermal SZ effect in large radio sources to test
equipartition (c.f., X-ray inverse-Compton studies). Leverage on relativistic electron populations?