Science at Q band SZ/CMB models: Q-band science Mark Birkinshaw University of Bristol

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


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


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


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.


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


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


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)


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).


Science at Q band

Scaling relation: flux density/X-ray kT

consistent with expected 3/2 scaling relation


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.


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.


Science at Q band

SZ effect confusion on CMB

Figure from Molnar & Birkinshaw 2000

thermal SZ

kinematic SZ

RS effect


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.


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.


Science at Q band

Simple observations: interferometers

SZA (2008)


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.


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


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


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


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


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


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.


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/


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


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


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


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.


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


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


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


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


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


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


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


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.


Science at Q band

Detailed structures

J0717.5+3745

z = 0.548

Clearly disturbed, shock-like substructure, filament

What will SZ image look like?


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.)


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)


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


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.


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


Science at Q band

Requirements on observations


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


Science at Q band

Requirements on observations


Cluster formation 0.02 Absolute calibration

Transverse velocity

0.01 Confusion; polarization calibration


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)


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


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


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?

Documents

Science at Q band SZ/CMB models: Q-band science Mark Birkinshaw University of Bristol