Precision Observations of Galaxy Clusters
through Broadband Spectroscopyof the Sunyaev-Zeldovich EffectLuca Lamagna (on behalf of P. de Bernardis)
Physics Department
Sapienza-University of Rome

Tsukuba Global Science Week
Session 8-8, Sep 26, 2017

Outline• Cluster science and SZ effect– Advantage of multi-frequency observations– Spectrometry of the SZE• Olimpo DFTS

– Instrument rationale– Subsystems review– Projected performance• Final Remarks

What are galaxy clusters?
«Galaxy clusters are significant concentrations of galaxies.»

Basically true, but…

What are galaxy clusters?
«Galaxy clusters are significant concentrations of galaxies.»

Basically true, but…fairly naive.

What truly are galaxy clusters?
•••«Galaxy Clusters are the cosmic structures on the high-mass tail of the halo
mass function»
Large structures (few Mpc) with a fair representation of the cosmic mass
budget:– ∼ 2% mass in galaxies (tens to thousands depending on richness)– ∼ 13% in the hot (107÷108K), ionized intra-cluster plasma(i.e. baryon assembly into galaxies is quite inefficient)– ∼ 85% dark matter (historical argument by F. Zwicky)
Typical masses in excess of 1014 M☉
Routine observations of clusters today are performed in a variety of spectral
windows:––––––

Optical, IR (σv , Ngal)
Optical (lensing mass)
X-rays (LX,TX)
Mm/submm (Compton Y)
Radio (halos, relics…)…

Clusters:
the crossroad of astrophysics and cosmology?
••
•
•
•
•
•

Measuring distances using clusters as standard rulers
Growth of cosmic structure from cluster number counts
Calibration of the SZ flux vs total mass scaling relation
Using the gas mass fraction in clusters to measure the cosmic baryon
density
Measuring the large-scale velocity fields in the universe from kinematic SZ
EffectConstraints from power spectrum
Constraints on Tcmb(z)Problem: at the MPc scales, structure assembly and evolution cannot be
predicted from pure gravity+cosmology alone.
Q: Given this complication, can we still predict some general properties whichbind the cluster population to the underlying cosmology?
A: Yes, if we understand the (baryon) physics in galaxy clusters.

Baryons in galaxy clusters• Assembly into galaxies is inefficient• Majority of baryonic mass in clusters is hot gas (ICM)– Temperature T ∼ 108 K (∼ 10 keV) (heated by gravitational potential)– Electron number density ne ~ 10-3 cm-3
– Mainly H, He, but with heavy elements (O, Fe, ..)– Mainly emits X-rays (but also radio and gamma rays), first observed byUhuru back in the ‘70s
– LX ∼ 1045 erg/s, most luminous extended X-ray sources in Universe– Causes the Sunyaev-Zel’dovich effect (SZE) by inverse Compton
scattering the background CMB photons

Clusters at CMB frequencies:
the Sunyaev-Zel’dovich EffectInverse Compton Scattering of CMB
photons off the hot ICM electrons results ina net energy injection into the CMBphotons.

Photons are shifted to higher frequencies,
providing a unique spectral signature of theCMB distorsion at microwaves.

«Holes in the microwave sky» at radio
frequencies, hot spots above ~217 GHz.

Redshift independent, first order in plasma
density w.r.t. X-ray brightness: excellent
tool to detect (and even discover) clusters
at high z.

Effect proportionalpressure of the ICM.

totheintegrated

32k 3TCMB x 4 e x
ΔI =σ T ∫ n e dl[θf1 (x ) − β + R (x, θ, β )]22 2xh ce −1( x
f1 (x ) = x coth  − 42)x = hν/kTCMB

θ = kTe /mc 2
β = Vpec /cSunyaev & Zel’dovich, Comm. Astr. Sp. Phys 4, 173 (1972)

Reviews by:
Rephaeli, ARA&A 33, 541 (1995)
Birkinshaw, Phys. Rep. 310,97 (1999)
Carlstrom et al., ARA&A 40, 643 (2002)

Clusters at CMB frequencies:
the Sunyaev-Zel’dovich EffectInverse Compton Scattering of CMB
photons off the hot ICM electrons results ina net energy injection into the CMB
photons.

Photons are shifted to higher frequencies,
providing a unique spectral signature of theCMB distorsion at microwaves.

«Holes in the microwave sky» at radio
frequencies, hot spots above ~217 GHz.

Redshift independent, first order in plasma
density w.r.t. X-ray brightness: excellent
tool to detect (and even discover) clusters
at high z.

Effect proportionalpressure of the ICM.

totheintegrated32k 3TCMB x 4 e x
ΔI =σ T ∫ n e dl[θf1 (x ) − β + R (x, θ, β )]22 2xh ce −1( xf1 (x ) = x coth  − 42)x = hν/kTCMB

θ = kTe /mc 2
β = Vpec /cSunyaev & Zel’dovich, Comm. Astr. Sp. Phys 4, 173 (1972)

Reviews by:
Rephaeli, ARA&A 33, 541 (1995)
Birkinshaw, Phys. Rep. 310,97 (1999)
Carlstrom et al., ARA&A 40, 643 (2002)

Clusters at CMB frequencies:
the Sunyaev-Zel’dovich EffectInverse Compton Scattering of CMB
photons off the hot ICM electrons results ina net energy injection into the CMB
photons.

Photons are shifted to higher frequencies,
providing a unique spectral signature of theCMB distorsion at microwaves.

«Holes in the microwave sky» at radio
frequencies, hot spots above ~217 GHz.

Redshift independent, first order in plasma
density w.r.t. X-ray brightness: excellent
tool to detect (and even discover) clusters
at high z.

Effect proportionalpressure of the ICM.

toThe spectral signature: Multifrequency view of Abell 2319 by Planck

theintegrated

Clusters at CMB frequencies:
the Sunyaev-Zel’dovich EffectInverse Compton Scattering of CMB
photons off the hot ICM electrons results ina net energy injection into the CMB
photons.

Photons are shifted to higher frequencies,
providing a unique spectral signature of theCMB distorsion at microwaves.

«Holes in the microwave sky» at radio
frequencies, hot spots above ~217 GHz.

Redshift independent, first order in plasma
density w.r.t. X-ray brightness: excellent
tool to detect (and even discover) clusters
at high z.

Effect proportionalpressure of the ICM.

totheThe redshift magic: OVRO/BIMA 30GHz maps with X-ray counterparts

integrated

Relativistic corrections• Relativistic effects in the high velocity tailof the electron energy distribution do havean impact over the final comptoonization
effect, up to 10-15% in moderately hot(kTe>8keV) clusters.
• The relativistically correct crossover
frequency is frequency dependent• Observational consequences in cluster
detection/selection and plasma
characterization: need to clean signals andmaps on a cluster-by-cluster basis, rather
than statistically.
• Significant in blind surveys of unknown
clusters.
• Measurements around the crossover andin the increment region are strongly
sensitive to gas temperatures, providing acompelling probe of the baryon thermalhistory.

Cluster studies today

Cluster scaling relations & the quest for the perfect mass proxy• How many clusters of mass M exist in a given
cosmology at redshift z?
• What is the probability that a cluster of mass
M at redshift z will have temperature Tx (orsome other observable)?

How many «inferred» masses?
Hydrostatic (X, SZ):

Dynamical (opt):

Lensing (opt):

Proxies: LX , TX , YX , YSZ , N200 , other?
Comparison of mass-proxies + hydro sims can help
identify which ones work best, but also provides
insights on the relevant cluster physics.

𝜎𝑇 𝜇𝑌𝑆,∆ =𝑚𝑒 𝑐 2 𝜇𝑒

∆𝐺𝐻0
4

2/3

5/3

𝐸 𝑧 2/3 𝑓𝑔𝑔𝑔,∆ 𝑀𝑡𝑡𝑡,∆Cosmology with cluster counts/masses

Different models/parametrizations for the Mass Function:(Press-Schechter, 1974)(Jenkins, 2001)

Ω𝑀 𝜌𝑐𝑐𝑐
𝑑𝑛𝑀=𝐴𝑑 𝑙𝑙𝜎 −1𝑀Where:𝜎2 ∝ �∞

0𝜎 −𝑎2+ 1 𝑒 −𝑐⁄𝜎𝑏𝑃 𝑘 𝑊 2 𝑘𝑘 𝑘 2 𝑑𝑑(Tinker, 2008)

Variance on mass scale M(constraints on σ8, Ωm, ΩΛ, w, …)

Cosmology with cluster counts/masses
Halo mass function +matter power spectrum(Cosmology)

Cluster counts(observations)Δ = 3200

Δ = 200

Halo mass function +matter power spectrum(Cosmology)

Volumeintegration(geometry)

Cluster counts(observations)Cluster studies in the 2010s

Blind SZ detections & hi res SZ mapping

ACT
Marriage et al., ApJ 737, 71 (2011)

Vanderlinde et al., ApJ 722, 1180 (2010)

SPTMustang

Korngut et al., ApJ 734,10 (2011)NIKAPlanck(since early paper no. VIII)The OLIMPO experiment• Long Duration Balloon
experiment for mm and submm astronomy• 2.6-m telescope withscanning capability bywobbling the primary mirror• Multifrequency arrays (4)with kinetic inductancedetectors
Two different observationalmodes in-flight:– photometry– spectrometry by DFTS
Main targets:
1. SZE on known clusters and blind survey
2. CMB power spectrum up to l=2000
3. FIRB

The OLIMPO experimentTeam @ Uni. Sapienza: S. Masi (PI), P. de Bernardis, M. De Petris, F. Piacentini, E. Battistelli,
L. Lamagna, A. Coppolecchia, G. D’alessandro, A. Paiella, F. Columbro
F. Nati*, A. Schillaci*, R. Gualtieri*• Long Duration Balloon
experiment for mm and submm astronomy• 2.6-m telescope withscanning capability by
wobbling the primary mirror• Multifrequency arrays (4)with kinetic inductancedetectors
Two different observationalmodes in-flight:– photometry– spectrometry by DFTS
Main targets:
1. SZE on known clusters and blind survey
2. CMB power spectrum up to l=2000
3. FIRBOLIMPO – spectral coverage

Cryostat& det. arrays

DFTS

telescope

OLIMPO – spectral coverage# detectors

19372354

Photon bckg over band(pW)

9191760

Photon noise overband*(10-18 Wrms /√Hz)

200

140

170

200

Cryostat& det. arrays

DFTS

telescope

OLIMPO – telescope and cold optics

Modified Offner 1:1 design (M. De Petris+)

OLIMPO – telescope and cold optics

Modified Offner 1:1 design (M. De Petris+)

OLIMPO – wet cryostat & fridge• Liquid N2 + He Vapor Cooled Shield@20K + LiquidHe@2K• Single stage He3 sorption fridge• Unmanned operation @ 300mK for 16days(suboptimal lab conditions) up to 45° tilt

Coppolecchia et al., in prep.

OLIMPO – KIDs

OLIMPO – KIDs

OLIMPO – KIDs

Paiella et al., in prep.

OLIMPO – readout

ROACH-2 boards (2x) featuring:- Virtex-6 SX475T FPGA
- PowerPC 440EPx stand-alone processor (control functions)MUSIC DAC/ADC Mezzanine
VALON 5007 Oscillator as LO and MUSIC clock
ADL5385/87 boards for quadrature mod/demod
Filters, Bias Tees, Attenuators
Cryogenic LNAs developed by ASU+Firmware provided by ASU+Python code for interfacing and acquisition management
Readout scheme/hardware derived from the BLAST-TNG readout –Gordon et al., J. Astr. Instr., Volume 5, Issue 4, id. 1641003 (2016)

OLIMPO – Differential FTS

Schillaci et al., Astronomy & Astrophysics, Volume 565, id.A125 (2014)

OLIMPO – Differential FTS

Schillaci et al., Astronomy & Astrophysics, Volume 565, id.A125 (2014)

OLIMPO – DFTS characterization
Resolution

D’alessandro et al., Applied Optics, vol. 54, issue 31, p. 9269, 2015

OLIMPO – DFTS characterization
Resolution

High freq efficiency and left/right FTS balance

D’alessandro et al., Applied Optics, vol. 54, issue 31, p. 9269, 2015

OLIMPO – DFTS characterization
Resolution

High freq efficiency and left/right FTS balanceCommon mode rejection and thermal/opticalimbalance

D’alessandro et al., Applied Optics, vol. 54, issue 31, p. 9269, 2015

OLIMPO – end-to-end performance
DFTS resolution can be adjusted with almost
no effort.
Noise/bin is proportional to the inverse of thespectral bin‐width.
In the case of OLIMPO, with telescope andspectrometer at 250K, photon noise fromoptics emission is important.
• 1.8 GHz res: About 110
independent spectral bins
• 6 GHz res: About 34 independent
spectral bins, within the same bands.
Observations from 10°to 60°elevation
40 targeted clusters S/N=10min=1h, max=5h
Single flight products:
34-frequency maps of selected sky regions (4sq. deg. tiles, 2’ FWHM res) on ~40 clusters
and ~40 blank‐sky regions.
Conversi et al., A&A 504 A7 (2010)
De Bernardis, LL, et al., A&A 538 A86 (2012)

OLIMPO – end-to-end performance
Simulations of OLIMPO observations in DFTS configuration show that the spectroscopicconfiguration has superior performance in converging to the correct estimate of thermal
optical depth and dust parameters, while the photometric configuration tends toconverge to biased estimates of the parameters.
In particular the separation of thermal SZ and foreground dust emission is effective andunbiased.

De Bernardis, LL et al., A&A 538 A86 2012

OLIMPO – flight

The former version of OLIMPO (featuringpast-gen TES detectors) was integrated inJuly 2014 for its first scientific flight fromSvalbard Islands (78°N)
After on-the-field testing of all thesubsystems (but NO launch due to adverseconditions), it has been funded for theupgrade to the KID configuration.
Launch was rescheduled to Summer 2018.

Concluding remarks• SZ spectroscopy is both reliable and versatile in precisionobservations of galaxy clusters.
• The technology is mature and compatible with current andnext-gen mm instrumentation.
• OLIMPO is not the only solution: the DFTS design has alreadybeen adapted and studied for both space and ground-based
platforms (different spectral coverage, different limiting
factors, but also different opportunities for making greatscience)• Ground-based operation from cold and dry sites, in particular,
could combine excellent spectral sensitivity with theadvantage of a large aperture telescope (Antarctica?).
Unfortunately, there are currently no plans to upgrade
existing facilities to perform spectroscopy.
• Many adaptations already studied (APEX, SAGACE,MILLIMETRON…)

ありがとうございました!