View source for Sunyaev–Zeldovich effect

{{Short description|Spectral distortion of cosmic microwave background in galaxy clusters}}
{{Use dmy dates|date=May 2021}}
{{cosmology}}
The '''Sunyaev–Zeldovich effect''' (named after [[Rashid Sunyaev]] and [[Yakov Zeldovich|Yakov B. Zeldovich]] and often abbreviated as the '''SZ effect''') is the [[Cosmic microwave background spectral distortions | spectral distortion]] of the [[cosmic microwave background]] (CMB) through [[Compton scattering#Inverse Compton scattering|inverse Compton scattering]] by high-energy [[electrons]] in galaxy clusters, in which the low-energy CMB [[photons]] receive an average energy boost during collision with the high-energy cluster electrons. Observed distortions of the [[cosmic microwave background]] spectrum are used to detect the disturbance of density in the universe. Using the Sunyaev–Zeldovich effect, dense [[Groups and clusters of galaxies|clusters of galaxies]] have been observed.

== Overview ==
The Sunyaev–Zeldovich effect was predicted by [[Rashid Sunyaev]] and [[Yakov Zeldovich]] to describe anisotropies in the CMB. The effect is caused by the CMB interacting with high energy electrons. These high energy electrons cause inverse Compton scattering of CMB photons which causes a distortion in the radiation spectrum of the CMB. The Sunyaev–Zeldovich effect is most apparent when observing galactic clusters. Analysis of CMB data at higher angular resolution (high [[Multipole|<math>\ell</math>-values]]) requires taking into account the Sunyaev–Zeldovich effect.

The Sunyaev–Zeldovich effect can be divided into different types:

* [[Thermal energy|Thermal]] effects, where the CMB photons interact with electrons that have high energies due to their temperature
* [[Kinematic]] effects, a second-order effect where the CMB photons interact with electrons that have high energies due to their bulk motion (also called the Ostriker–Vishniac effect, after [[Jeremiah P. Ostriker]] and [[Ethan Vishniac]].<ref>{{Cite journal|last1=Ostriker|first1=Jeremiah P.|last2=Vishniac|first2=Ethan T.|name-list-style=amp|date=1986|title=Generation of Microwave Background Fluctuations from Nonlinear Perturbations at the Era of Galaxy Formation|journal=Astrophysical Journal Letters|volume=306|page=L51|bibcode=1986ApJ...306L..51O|doi=10.1086/184704}}</ref>)
* [[Polarization (waves)|Polarization]]

The Sunyaev–Zeldovich effect is of major [[Astrophysics|astrophysical]] and [[Physical cosmology|cosmological]] interest. It can help determine the value of the [[Hubble's law|Hubble constant]], determine the location of new galaxy clusters, and in the study of cluster structure and mass. Since the Sunyaev–Zeldovich effect is a scattering effect, its magnitude is independent of redshift, which means that clusters at high redshift can be detected just as easily as those at low redshift.

== Thermal effects ==
The distortion of the CMB resulting from a large number of high energy electrons is known as the thermal Sunyaev–Zeldovich effect. The thermal Sunyaev–Zeldovich effect is most commonly studied in [[galaxy cluster]]s. By comparing the Sunyaev–Zeldovich effect and [[X-ray emission]] data, the thermal structure of the cluster can be studied, and if the temperature profile is known, Sunyaev–Zeldovich data can be used to determine the baryonic mass of the cluster along the line of sight.<ref name=":03">{{Cite journal|last=Birkinshaw|first=M|date=March 1999|title=The Sunyaev–Zel'dovich effect|url=https://linkinghub.elsevier.com/retrieve/pii/S0370157398000805|journal=Physics Reports|volume=310|issue=2–3|pages=97–195|doi=10.1016/S0370-1573(98)00080-5|arxiv=astro-ph/9808050|bibcode=1999PhR...310...97B|hdl=1983/5d24f14a-26e0-44d3-8496-5843b108fec5|s2cid=119330362}}</ref> Comparing Sunyaev–Zeldovich and X-ray data can also be used to determine the Hubble constant using the angular diameter distance of the cluster.<ref>{{Cite journal|last1=Birkinshaw|first1=M.|last2=Hughes|first2=J. P.|date=January 1994|title=A measurement of the Hubble constant from the X-ray properties and the Sunyaev-Zel'dovich effect of Abell 2218|journal=The Astrophysical Journal|language=en|volume=420|pages=33|doi=10.1086/173540|bibcode=1994ApJ...420...33B|issn=0004-637X|doi-access=free}}</ref> These thermal distortions can also be measured in [[supercluster]]s and in gases in the local group, although they are less significant and more difficult to detect. In superclusters, the effect is not strong (< 8 μK), but with precise enough equipment, measuring this distortion can give a glimpse into large-scale structure formation. Gases in the local group may also cause anisotropies in the CMB due to the thermal Sunyaev–Zeldovich effect which must be taken into account when measuring the CMB for certain angular scales.<ref name=":03" />

== Kinematic effects ==
The kinematic Sunyaev–Zeldovich effect is caused when a galaxy cluster is moving relative to the [[Hubble's law|Hubble flow]]. The kinematic Sunyaev–Zeldovich effect gives a method for calculating the peculiar velocity:
<math display="block">\Delta T_\text{kin} = - T_\text{CMB}\frac {V_p} {c} \tau</math>
where <math>V_p</math> is the peculiar velocity, and <math>\tau</math> is the optical depth.<ref>{{cite journal| last1=Tartari|first1=A.| last2=Boella|first2=G.|last3=Candotti|first3=M.|last4=Gervasi|first4=M.|last5=Natale|first5=V.| last6=Passerini|first6=A.| last7=Sironi|first7=G.|last8=Zannoni|first8=M.|date=2003-07-09|title=Sunyaev Zel'dovich effect studies with MASTER|journal=Memorie della Societa Astronomica Italiana Supplementi|volume=2|page=44|arxiv=astro-ph/0307166| bibcode=2003MSAIS...2...44T}}</ref> In order to use this equation, the thermal and kinematic effects need to be separated. The effect is relatively weak for most galaxy clusters. Using [[gravitational lens]]ing, the peculiar velocity can be used to determine other velocity components for a specific galaxy cluster.<ref name=":03" /> These kinematic effects can be used to determine the Hubble constant and the behavior of clusters.

== Research ==
Current research is focused on modelling how the effect is generated by the intracluster plasma in [[galaxy cluster]]s, and on using the effect to estimate the [[Hubble constant]] and to separate different components in the angular average statistics of fluctuations in the background. Hydrodynamic structure formation simulations are being studied to gain data on thermal and kinetic effects in the theory.<ref>{{Cite journal|last1=Cunnama D.|first1=Faltenbacher F.|last2=Passmoor S.|first2=Cress C.|last3=Cress|first3=C.|last4=Passmoor|first4=S.|date=2009|title=The velocity-shape alignment of clusters and the kinetic Sunyaev–Zeldovich effect|journal=MNRAS Letters|volume=397|issue=1|page=L41–L45|arxiv=0904.4765|bibcode=2009MNRAS.397L..41C|doi=10.1111/j.1745-3933.2009.00680.x|doi-access=free |s2cid=9809159}}</ref> Observations are difficult due to the small amplitude of the effect and to confusion with experimental error and other sources of CMB temperature fluctuations. To distinguish the SZ effect due to galaxy clusters from ordinary density perturbations, both the [[Electromagnetic spectrum|spectral]] dependence and the spatial dependence of fluctuations in the [[cosmic microwave background]] are used.

A factor which facilitates high redshift cluster detection is the [[Angular size redshift relation|angular scale versus redshift relation]]: it changes little between redshifts of 0.3 and 2, meaning that clusters between these redshifts have similar sizes on the sky. The use of surveys of clusters detected by their Sunyaev–Zeldovich effect for the determination of cosmological parameters has been demonstrated by Barbosa et al. (1996). This might help in understanding the dynamics of dark energy in surveys ([[South Pole Telescope]], [[Atacama Cosmology Telescope]], ''[[Planck (spacecraft)|Planck]]'').

== Observations ==
[[File:ALMA’s_Hole_in_the_Universe.jpg|alt=This picture taken by the Atacama Large Millimeter Array is known to be one of the most galaxy clusters, known as RX J1347-1145|thumb|First measurements of the thermal Sunyaev–Zeldovich effect from the [[Atacama Large Millimeter Array]] with one of the most massive galaxy clusters known, [[RX J1347.5−1145|RX J1347.5-1145]].<ref>{{cite web|title=ALMA's Hole in the Universe|url=https://www.eso.org/public/images/potw1708a/|access-date=20 February 2017|website=eso.org}}</ref>]]
In 1984, researchers from the [[Cavendish Astrophysics Group|Cambridge Radio Astronomy Group]] and the [[Owens Valley Radio Observatory]] first detected the Sunyaev–Zeldovich effect from [[Galaxy cluster|clusters of galaxies]].<ref>{{Cite journal|last1=Birkinshaw|first1=M.|last2=Gull|first2=S.F.|last3=Hardebeck|first3=H.|date=1984|title=The Sunyaev-Zeldovich effect towards three clusters of galaxies|url=https://www.nature.com/articles/309034a0|journal=Nature|volume=309|issue=5963|pages=34–35|bibcode=1984Natur.309...34B|doi=10.1038/309034a0|s2cid=4276748}}</ref> Ten years later, the [[Ryle Telescope]] was used to image a [[Galaxy cluster|cluster of galaxies]] in the Sunyaev–Zeldovich effect for the first time.<ref>{{cite arXiv|last=Saunders|first=Richard|date=1996-11-26|title=Sunyaev-Zel'dovich observations with the Ryle Telescope|eprint=astro-ph/9611213}}</ref>

In 1987 the [[Cosmic Background Explorer|Cosmic Background Explorer (COBE)]] satellite observed the CMB and gave more accurate data for anisotropies in the CMB, allowing for more accurate analysis of the Sunyaev–Zeldovich effect.<ref name=":03" />

Instruments built specifically to study the effect include the Sunyaev–Zeldovich camera on the [[Atacama Pathfinder Experiment]],<ref>{{Cite journal|last1=Schwan|first1=D.|last2=Ade|first2=P. a. R.|last3=Basu|first3=K.|last4=Bender|first4=A. N.|last5=Bertoldi|first5=F.|last6=Cho|first6=H.-M.|author6-link=Hsiao-Mei Cho|last7=Chon|first7=G.|last8=Clarke|first8=John|last9=Dobbs|first9=M.|last10=Ferrusca|first10=D.|last11=Güsten|first11=R.|date=2011-09-01|title=Invited Article: Millimeter-wave bolometer array receiver for the Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument|url=https://aip.scitation.org/doi/full/10.1063/1.3637460|journal=Review of Scientific Instruments|volume=82|issue=9|pages=091301|doi=10.1063/1.3637460|pmid=21974566|arxiv=1008.0342|bibcode=2011RScI...82i1301S|s2cid=33402455|issn=0034-6748}}</ref> and the [[Sunyaev–Zel'dovich Array|Sunyaev–Zeldovich Array]], which both saw first light in 2005. In 2012, the [[Atacama Cosmology Telescope]] (ACT) performed the first statistical detection of the kinematic SZ effect.<ref>{{Cite journal|last1=Hand|first1=Nick|last2=Addison|first2=Graeme E.|last3=Aubourg|first3=Eric|last4=Battaglia|first4=Nick|last5=Battistelli|first5=Elia S.|last6=Bizyaev|first6=Dmitry|last7=Bond|first7=J. Richard|last8=Brewington|first8=Howard|last9=Brinkmann|first9=Jon|last10=Brown|first10=Benjamin R.|last11=Das|first11=Sudeep|display-authors=29|date=2012|title=Detection of Galaxy Cluster Motions with the Kinematic Sunyaev–Zeldovich Effect|journal=Physical Review Letters|volume=109|issue=4|pages=041101|arxiv=1203.4219|bibcode=2012PhRvL.109d1101H|doi=10.1103/PhysRevLett.109.041101|pmid=23006072|first21=Matt|first12=Kyle S.|last13=Devlin|first13=Mark J.|first14=Joanna|last15=Dunner|first15=Rolando|first16=Daniel J.|first18=Megan B.|last17=Fowler|first17=Joseph W.|last18=Gralla|last19=Hajian|last16=Eisenstein|last20=Halpern|first20=Mark|last21=Hilton|last12=Dawson|first26=Kent D.|last22=Hincks|last27=Kosowsky|last24=Hughes|first23=Renée|first24=John P.|last25=Infante|first25=Leopoldo|last26=Irwin|last29=Malanushenko|first27=Arthur|first19=Amir|last28=Lin|first28=Yen-Ting|first22=Adam D.|first29=Elena|last30=Malanushenko|first30=Viktor|s2cid=11392448|last23=Hlozek|last14=Dunkley}}</ref> In 2012 the kinematic SZ effect was detected in an individual object for the first time in [[MACS J0717.5+3745]].<ref>{{Cite journal|last1=Mroczkowski|first1=Tony|last2=Dicker|first2=Simon|last3=Sayers|first3=Jack|last4=Reese|first4=Erik D.|last5=Mason|first5=Brian|last6=Czakon|first6=Nicole|last7=Romero|first7=Charles|last8=Young|first8=Alexander|last9=Devlin|first9=Mark|last10=Golwala|first10=Sunil|last11=Korngut|first11=Phillip|title=A Multi-Wavelength Study of the Sunyaev-Zel'dovich Effect in the Triple-Merger Cluster Macs J0717.5+3745 with Mustang and Bolocam|date=2012-12-10|url=https://iopscience.iop.org/article/10.1088/0004-637X/761/1/47|journal=The Astrophysical Journal|volume=761|issue=1|pages=47|doi=10.1088/0004-637X/761/1/47|arxiv=1205.0052|bibcode=2012ApJ...761...47M|s2cid=50951413|issn=0004-637X}}</ref>

As of 2015, the [[South Pole Telescope|South Pole Telescope (SPT)]] had used the Sunyaev–Zeldovich effect to discover 415 galaxy clusters.<ref>{{Cite journal|last1=Bleem|first1=L. E.|last2=Stalder|first2=B.|last3=de Haan|first3=T.|last4=Aird|first4=K. A.|last5=Allen|first5=S. W.|last6=Applegate|first6=D. E.|last7=Ashby|first7=M. L. N.|last8=Bautz|first8=M.|last9=Bayliss|first9=M.|last10=Benson|first10=B. A.|last11=Bocquet|first11=S.|title=Galaxy Clusters Discovered Via the Sunyaev-Zel'dovich Effect in the 2500-Square-Degree SPT-Sz Survey|date=2015-01-29|url=https://iopscience.iop.org/article/10.1088/0067-0049/216/2/27|journal=The Astrophysical Journal Supplement Series|language=en|volume=216|issue=2|pages=27|doi=10.1088/0067-0049/216/2/27|arxiv=1409.0850|bibcode=2015ApJS..216...27B|hdl=1721.1/96784|s2cid=6663564|issn=1538-4365}}</ref> The Sunyaev–Zeldovich effect has been and will continue to be an important tool in discovering hundreds of galaxy clusters.

Recent experiments such as the OLIMPO balloon-borne telescope try to collect data in specific frequency bands and specific regions of the sky in order to pinpoint the Sunyaev–Zeldovich effect and give a more accurate map of certain regions of the sky.<ref>{{Cite journal|date=2007-03-01|title=The OLIMPO experiment|url=https://www.sciencedirect.com/science/article/abs/pii/S1387647306003253|journal=New Astronomy Reviews|language=en|volume=51|issue=3–4|pages=385–389|doi=10.1016/j.newar.2006.11.066|issn=1387-6473|last1=Nati|first1=F.|last2=Ade|first2=P.|last3=Boscaleri|first3=A.|last4=Brienza|first4=D.|last5=Calvo|first5=M.|last6=Colafrancesco|first6=S.|last7=Conversi|first7=L.|last8=De Bernardis|first8=P.|last9=De Petris|first9=M.|last10=Delbart|first10=A.|last11=Hargrave|first11=P.|last12=Iacoangeli|first12=A.|last13=Juin|first13=J.B.|last14=Magneville|first14=C.|last15=Marini Bettolo|first15=C.|last16=Masi|first16=S.|last17=Mauskopf|first17=P.|last18=Melchiorri|first18=F.|last19=Nati|first19=L.|last20=Orlando|first20=A.|last21=Rephaeli|first21=Y.|last22=Romeo|first22=G.|last23=Pansart|first23=J.P.|last24=Peterzen|first24=S.|last25=Piacentini|first25=F.|last26=Pisano|first26=G.|last27=Polenta|first27=G.|last28=Salvaterra|first28=L.|last29=Savini|first29=G.|last30=Tucker|first30=C.|bibcode=2007NewAR..51..385N|display-authors=1}}</ref>

== See also ==

* [[Sachs–Wolfe effect]]
* [[Cosmic microwave background spectral distortions]]
* [[Kompaneyets equation]]

==References==
{{Reflist|colwidth=30em}}

==Further reading==
* {{cite journal | first = Y. | last = Rephaeli | bibcode = 1995ARA&A..33..541R | title = Comptonization of the Cosmic Microwave Background: The Sunyaev–Zeldovich Effect | journal=Annual Review of Astronomy and Astrophysics | volume = 33 | date= 1995 | issue = 1 | pages = 541–580 | doi = 10.1146/annurev.aa.33.090195.002545}}
*{{cite journal | author=Barbosa, D. |author2=Bartlett, J. G. | bibcode = 1996A&A...314...13B | title = The Sunyaev–Zel'dovich effect and the value of &Omega;<sub>0</sub> | journal=Astronomy and Astrophysics | volume = 314 | pages = 13–17| year= 1996 |arxiv = astro-ph/9511084 |last3=Blanchard  |first3=A.  |last4=Oukbir  |first4=J.  }}
* {{cite journal | author=Birkinshaw, M. |author2=Gull, S. F.  | bibcode = 1984Natur.309...34B | title = The Sunyaev–Zel'dovich effect towards three clusters of galaxies | journal=Nature | volume = 309 | issue = 5963 | pages = 34–35| date = 1984 | doi = 10.1038/309034a0|last3=Hardebeck  |first3=H.  |s2cid=4276748 }}
* {{cite journal | last = Birkinshaw | first = Mark | s2cid = 119330362 | url = http://nedwww.ipac.caltech.edu/level5/Birkinshaw/Birk_contents.html | title = The Sunyaev Zel'dovich Effect | year = 1999 | journal=Physics Reports | volume = 310 | issue = 2–3 | pages = 97–195 | doi = 10.1016/S0370-1573(98)00080-5|arxiv = astro-ph/9808050 |bibcode = 1999PhR...310...97B | hdl = 1983/5d24f14a-26e0-44d3-8496-5843b108fec5 }}
* {{cite journal | last = Cen | first = Renyue | author2 = Jeremiah P. Ostriker | s2cid = 1284598 | url = http://zeus.ncsa.uiuc.edu:8080/gc3/gc3013/mdm.html | title = A hydrodynamic approach to cosmology: the mixed dark matter cosmological scenario | journal = The Astrophysical Journal | volume = 431 | issue = 1994 | date = 1994 | pages = 451 | doi = 10.1086/174499 | bibcode = 1994ApJ...431..451C | arxiv = astro-ph/9404011 | citeseerx = 10.1.1.254.3635 | url-status = dead | archive-url = https://web.archive.org/web/20040222081854/http://zeus.ncsa.uiuc.edu:8080/gc3/gc3013/mdm.html | archive-date = 22 February 2004 }}
* {{cite journal | last = Hu | first = Jian |author2=Yu-Qing Lou  | s2cid = 10520376 | arxiv = astro-ph/0402669 | title = Magnetic Sunyaev–Zel'dovich effect in galaxy clusters | journal=Astrophysical Journal Letters|bibcode = 2004ApJ...606L...1H |doi = 10.1086/420896 | date = 2004 | volume = 606 | issue = 1 | pages = L1–L4 }}
* {{cite journal | last = Ma | first = Chung-Pei |author-link=Chung-Pei Ma|author2=J. N. Fry  | s2cid = 5655238 | title = Nonlinear Kinetic Sunyaev–Zel'dovich Effect | journal= Physical Review Letters| date = 27 May 2002 | arxiv = astro-ph/0106342 |bibcode = 2002PhRvL..88u1301M |doi = 10.1103/PhysRevLett.88.211301 | pmid = 12059470 | volume = 88 | issue = 21 | pages = 211301 | url = https://cds.cern.ch/record/505490 }}
* {{cite journal | first1 = A. D. | last1 = Myers | title = Evidence for an Extended SZ Effect in WMAP Data | journal=[[Monthly Notices of the Royal Astronomical Society]] | arxiv = astro-ph/0306180 |bibcode = 2004MNRAS.347L..67M |doi = 10.1111/j.1365-2966.2004.07449.x | date = 2004 | volume = 347 | issue = 4 | pages = L67–L72 | display-authors = 2 | last2 = Shanks | first2 = T. | last3 = Outram | first3 = P. J. | last4 = Frith | first4 = W. J. | last5 = Wolfendale | first5 = A. W. | doi-access = free | s2cid = 53119165 }}
* {{cite journal | last1 = Springel | first1 = Volker | first2 = Martin | last2 = White | first3 = Lars | last3 = Hernquist | s2cid = 6728519 | arxiv = astro-ph/0008133 | title = Hydrodynamic Simulations of the Sunyaev–Zel'dovich effect(s) | journal=The Astrophysical Journal|bibcode = 2001ApJ...549..681S |doi = 10.1086/319473 | date = 2001 | volume = 549 | issue = 2 | pages = 681–687 }}
* {{cite journal | last = Sunyaev | first = R. A. |author2=Ya. B. Zel'dovich | bibcode = 1970Ap&SS...7....3S | title = Small-Scale Fluctuations of Relic Radiation | journal=Astrophysics and Space Science | volume = 7 | issue = 1 | pages = 3–19 | date = 1970 | doi = 10.1007/BF00653471 | s2cid = 117050217 | url =  https://link.springer.com/article/10.1007/BF00653471 | url-access = subscription}}
* {{cite journal | last = Sunyaev | first = R. A. |author2=Ia. B. Zel'dovich | bibcode = 1980ARA&A..18..537S | title = Microwave background radiation as a probe of the contemporary structure and history of the universe | journal=Annual Review of Astronomy and Astrophysics | volume = 18 |date = 1980 | issue = 1 | pages = 537–560 | doi = 10.1146/annurev.aa.18.090180.002541}}
* {{cite journal | last1 = Diego | first1 = J. M. | first2 = E. | last2 = Martinez | first3 = J. L. | last3 = Sanz | first4 = N. | last4 = Benitez | first5 = J. | last5 = Silk | s2cid = 10486016 | arxiv =  astro-ph/0103512| title = The Sunyaev–Zel'dovich effect as a cosmological discriminator | journal=Monthly Notices of the Royal Astronomical Society| volume = 331 |date = 2002 | issue = 3 | pages = 556–568| doi = 10.1046/j.1365-8711.2002.05039.x| doi-access = free |bibcode = 2002MNRAS.331..556D }}
* Royal Astronomical Society, ''Corrupted echoes from the Big Bang?'' RAS Press Notice PN 04/01 <!--Was at : http://www.ras.org.uk/html/press/pn0401ras.html -->

== External links ==
* [http://www.innovations-report.com/html/reports/physics_astronomy/report-25349.html  Corrupted echoes from the Big Bang?] innovations-report.com.
* [http://xstructure.inr.ac.ru/x-bin/theme3.py?level=1&index1=10339 Sunyaev–Zel'dovich effect on arxiv.org]
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