quenching (astronomy)

In large surveys of the Universe, galaxies generally display a bi-modality, with distinct populations of blue, star-forming galaxies versus red, quenched ones.{{Cite journal |last1=Gabor |first1=J. M. |last2=Davé |first2=R. |last3=Finlator |first3=K. |last4=Oppenheimer |first4=B. D. |date=2010-09-11 |title=How is star formation quenched in massive galaxies? |journal=Monthly Notices of the Royal Astronomical Society |volume=407 |issue=2 |pages=749–771 |doi=10.1111/j.1365-2966.2010.16961.x |doi-access=free |arxiv=1001.1734 |bibcode=2010MNRAS.407..749G |issn=0035-8711}}{{Cite journal |last1=McGee |first1=Sean L. |last2=Balogh |first2=Michael L. |last3=Wilman |first3=David J. |last4=Bower |first4=Richard G. |last5=Mulchaey |first5=John S. |last6=Parker |first6=Laura C. |last7=Oemler |first7=Augustus |date=2011-05-11 |title=The Dawn of the Red: star formation histories of group galaxies over the past 5 billion years |journal=Monthly Notices of the Royal Astronomical Society |volume=413 |issue=2 |pages=996–1012 |doi=10.1111/j.1365-2966.2010.18189.x |doi-access=free |arxiv=1012.2388 |bibcode=2011MNRAS.413..996M |issn=0035-8711}} To quantify this bi-modality, astronomers use $\{sSFR\}$, the specific star formation rate of a galaxy, which can be defined simply as:

$sSFR\; =\; \{SFR\; \backslash over\; M\_*\}$

File:Optical Image of M87 Jet (2001-0134-more-2).tiff. Astrophysical jets are a type of active galactic nucleus (AGN) feedback that can heat up previously cold gas and prevent quenching.]]

The most prominent driver of quenching in a galaxy is feedback from its active galactic nucleus (AGN).{{Cite journal |last1=Terrazas |first1=Bryan A |last2=Bell |first2=Eric F |last3=Pillepich |first3=Annalisa |last4=Nelson |first4=Dylan |last5=Somerville |first5=Rachel S |last6=Genel |first6=Shy |last7=Weinberger |first7=Rainer |last8=Habouzit |first8=Mélanie |last9=Li |first9=Yuan |last10=Hernquist |first10=Lars |last11=Vogelsberger |first11=Mark |date=2020-04-01 |title=The relationship between black hole mass and galaxy properties: examining the black hole feedback model in IllustrisTNG |url=https://academic.oup.com/mnras/article/493/2/1888/5740724 |journal=Monthly Notices of the Royal Astronomical Society |volume=493 |issue=2 |pages=1888–1906 |doi=10.1093/mnras/staa374 |doi-access=free |issn=0035-8711|arxiv=1906.02747 }} When gas and dust spiral towards a supermassive black hole inside an AGN, this process can release a lot of energy and heat up the gas of the entire galaxy, which takes away the amount of cold gas that the galaxy needs for star formation.

In cosmological simulations such as Illustris, quenching can only happen in massive galaxies when there is some type of AGN-driven heating.{{Cite journal |last1=Piotrowska |first1=Joanna M |last2=Bluck |first2=Asa F L |last3=Maiolino |first3=Roberto |last4=Peng |first4=Yingjie |date=2022-05-01 |title=On the quenching of star formation in observed and simulated central galaxies: evidence for the role of integrated AGN feedback |url=https://academic.oup.com/mnras/article/512/1/1052/6482843 |journal=Monthly Notices of the Royal Astronomical Society |volume=512 |issue=1 |pages=1052–1090 |doi=10.1093/mnras/stab3673 |doi-access=free |issn=0035-8711|arxiv=2112.07672 }} There are at least two scenarios by which an AGN can heat up gas in a galaxy. In one scenario, a lot of gas accretes onto the AGN at once, which leads to violent feedback, including astrophysical jets, which can heat up entire galaxies at a rapid pace.{{Cite journal |last1=Maiolino |first1=R. |last2=Gallerani |first2=S. |last3=Neri |first3=R. |last4=Cicone |first4=C. |last5=Ferrara |first5=A. |last6=Genzel |first6=R. |last7=Lutz |first7=D. |last8=Sturm |first8=E. |last9=Tacconi |first9=L. J. |last10=Walter |first10=F. |last11=Feruglio |first11=C. |last12=Fiore |first12=F. |last13=Piconcelli |first13=E. |date=2012-09-01 |title=Evidence of strong quasar feedback in the early Universe |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=425 |issue=1 |pages=L66–L70 |doi=10.1111/j.1745-3933.2012.01303.x |doi-access=free |arxiv=1204.2904 |bibcode=2012MNRAS.425L..66M |issn=1745-3925}} This is known as the "quasar mode". In another scenario called the "preventative mode", the heating occurs in a slower, less violent way: the AGN provides energy that prevents cold gas from accreting in the interstellar medium, which over time will reduce star formation.{{Cite journal |last1=Brownson |first1=Simcha |last2=Bluck |first2=Asa F L |last3=Maiolino |first3=Roberto |last4=Jones |first4=Gareth C |date=2022-04-01 |title=What drives galaxy quenching? A deep connection between galaxy kinematics and quenching in the local Universe |url=https://academic.oup.com/mnras/article/511/2/1913/6524206 |journal=Monthly Notices of the Royal Astronomical Society |volume=511 |issue=2 |pages=1913–1941 |doi=10.1093/mnras/stab3749 |doi-access=free |issn=0035-8711|arxiv=2201.02484 }} Observations of the local Universe have shown that both pathways can lead to the heating of cold gas, and eventually quenching.{{Cite journal |last=Fabian |first=A. C. |date=2012-09-22 |title=Observational Evidence of Active Galactic Nuclei Feedback |url=https://www.annualreviews.org/content/journals/10.1146/annurev-astro-081811-125521 |journal=Annual Review of Astronomy and Astrophysics |language=en |volume=50 |issue= |pages=455–489 |doi=10.1146/annurev-astro-081811-125521 |arxiv=1204.4114 |bibcode=2012ARA&A..50..455F |issn=0066-4146}}

Another mechanism for quenching is shock heating, which begins when intergalactic gas falls into a galaxy's dark matter halo at a rate much faster than the local speed of sound.{{Cite journal |last1=Birnboim |first1=Yuval |last2=Dekel |first2=Avishai |date=2003 |title=Virial shocks in galactic haloes? |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=345 |issue=1 |pages=349–364 |doi=10.1046/j.1365-8711.2003.06955.x|doi-access=free |arxiv=astro-ph/0302161 |bibcode=2003MNRAS.345..349B }}{{Cite journal |last1=Dekel |first1=Avishai |last2=Birnboim |first2=Yuval |date=2006-05-01 |title=Galaxy bimodality due to cold flows and shock heating |journal=Monthly Notices of the Royal Astronomical Society |volume=368 |issue=1 |pages=2–20 |doi=10.1111/j.1365-2966.2006.10145.x |doi-access=free |arxiv=astro-ph/0412300 |bibcode=2006MNRAS.368....2D |issn=0035-8711}} This creates a shock that not only halts the in-falling material, but also generates a hot, virialized halo of gas which propagates towards the virial radius (the radius of the dark matter halo itself) and, in some cases, can extend even further than said radius. Under the effect of this hot medium, the cold gas in the galaxy can be heated up, thus preventing star formation.

File:Eridanus II color cutout hst 14224 03 acs wfc f814w f475w sci.jpg, a dwarf galaxy quenched solely by supernova feedback.|left]]

Shock heating is not possible across all ranges of galaxy halo mass, but is restricted to halos with masses above 10¹² solar masses.{{Cite journal |last1=Dekel |first1=Avishai |last2=Birnboim |first2=Yuval |date=2008-01-01 |title=Gravitational quenching in massive galaxies and clusters by clumpy accretion |journal=Monthly Notices of the Royal Astronomical Society |volume=383 |issue=1 |pages=119–138 |doi=10.1111/j.1365-2966.2007.12569.x |doi-access=free |arxiv=0707.1214 |bibcode=2008MNRAS.383..119D |issn=0035-8711}} This is because at lower masses, the gas pressure generated by the shock is curtailed by radiative cooling and cannot prevent the shock from gravitational collapse. Moreover, even in cases where the shock is supported and successfully generates a hot medium, there may still be gas filaments within the halo that are too cold and dense to be heated up. These filaments will provide critical gas supply to the post-shock galaxy, which is now dominated by the hot medium. In such scenarios, a full quenching of the galaxy will require supplementary factors, including AGN feedback.{{Cite journal |last1=Ocvirk |first1=P. |last2=Pichon |first2=C. |last3=Teyssier |first3=R. |date=2008 |title=Bimodal gas accretion in the Horizon-MareNostrum galaxy formation simulation |journal=Monthly Notices of the Royal Astronomical Society |volume=390 |issue=4 |page=1326 |language=en |doi=10.1111/j.1365-2966.2008.13763.x|doi-access=free |arxiv=0803.4506 |bibcode=2008MNRAS.390.1326O }}{{Cite journal |last1=Kereš |first1=Dušan |last2=Katz |first2=Neal |last3=Fardal |first3=Mark |last4=Davé |first4=Romeel |last5=Weinberg |first5=David H. |date=2009-05-01 |title=Galaxies in a simulated ΛCDM Universe - I. Cold mode and hot cores |journal=Monthly Notices of the Royal Astronomical Society |language=en |volume=395 |issue=1 |pages=160–179 |doi=10.1111/j.1365-2966.2009.14541.x|doi-access=free |arxiv=0809.1430 |bibcode=2009MNRAS.395..160K }}

There are additional processes within a galaxy that can contribute to its quenching in limited cases. One such process is supernovae, which can indeed heat up cold gas but is too distributed to singlehandedly quench galaxies inside massive dark matter halos.{{Cite journal |last1=Pontzen |first1=Andrew |last2=Tremmel |first2=Michael |last3=Roth |first3=Nina |last4=Peiris |first4=Hiranya V. |last5=Saintonge |first5=Amélie|author5-link=Amélie Saintonge |last6=Volonteri |first6=Marta |author6-link=Marta Volonteri|last7=Quinn |first7=Tom |last8=Governato |first8=Fabio |date=2017-02-11 |title=How to quench a galaxy |url=https://academic.oup.com/mnras/article/465/1/547/2617667 |journal=Monthly Notices of the Royal Astronomical Society |volume=465 |issue=1 |pages=547–558 |doi=10.1093/mnras/stw2627 |doi-access=free |issn=0035-8711|arxiv=1607.02507 }} However, in the case of ultra-faint dwarf galaxy Eridanus II, whose halo is only 10⁷ solar masses, supernova feedback alone has been shown to be capable of driving out star-forming gas, thereby quenching the system.{{Cite journal |last1=Gallart |first1=C. |last2=Monelli |first2=M. |last3=Ruiz-Lara |first3=T. |last4=Calamida |first4=A. |last5=Cassisi |first5=S. |last6=Cignoni |first6=M. |last7=Anderson |first7=J. |last8=Battaglia |first8=G. |last9=Bermejo-Climent |first9=J. R. |last10=Bernard |first10=E. J. |last11=Martínez-Vázquez |first11=C. E. |last12=Mayer |first12=L. |last13=Salvadori |first13=S. |last14=Monachesi |first14=A. |last15=Navarro |first15=J. F. |date=2021-03-01 |title=The Star Formation History of Eridanus II: On the Role of Supernova Feedback in the Quenching of Ultrafaint Dwarf Galaxies* |journal=The Astrophysical Journal |volume=909 |issue=2 |pages=192 |doi=10.3847/1538-4357/abddbe |doi-access=free |arxiv=2101.04464 |bibcode=2021ApJ...909..192G |issn=0004-637X}}

A merging event between two star-forming galaxies can create a quenched galaxy. In this scenario, the merger drastically alters the morphology of the galaxies, thus redistributing their material and causing a starburst. This starburst then quickly uses up the cold gas reservoir and leaves behind a single galaxy with reduced star formation rates. In addition, if the merging galaxies host an AGN, the starburst can also feed that AGN, which heats up any remaining cold gas and results in a completely quenched elliptical galaxy.{{Cite journal |last1=Springel |first1=Volker |last2=White |first2=Simon D. M. |last3=Jenkins |first3=Adrian |last4=Frenk |first4=Carlos S. |last5=Yoshida |first5=Naoki |last6=Gao |first6=Liang |last7=Navarro |first7=Julio |last8=Thacker |first8=Robert |last9=Croton |first9=Darren |last10=Helly |first10=John |last11=Peacock |first11=John A. |last12=Cole |first12=Shaun |last13=Thomas |first13=Peter |last14=Couchman |first14=Hugh |last15=Evrard |first15=August |date=2005 |title=Simulations of the formation, evolution and clustering of galaxies and quasars |url=https://www.nature.com/articles/nature03597 |journal=Nature |language=en |volume=435 |issue=7042 |pages=629–636 |doi=10.1038/nature03597 |pmid=15931216 |arxiv=astro-ph/0504097 |bibcode=2005Natur.435..629S |issn=0028-0836}}{{Cite journal |last1=Quai |first1=Salvatore |last2=Byrne-Mamahit |first2=Shoshannah |last3=Ellison |first3=Sara L |last4=Patton |first4=David R |last5=Hani |first5=Maan H |date=2023-02-21 |title=The interconnection between galaxy mergers, AGN activity, and rapid quenching of star formation in simulated post-merger galaxies |url=https://academic.oup.com/mnras/article/519/2/2119/6939847 |journal=Monthly Notices of the Royal Astronomical Society |volume=519 |issue=2 |pages=2119–2137 |doi=10.1093/mnras/stac3713 |doi-access=free |issn=0035-8711|arxiv=2212.10598 }}

File:NGC 4388 - HST - Potw1649a.tif, a spiral galaxy whose reduced star formation rate is due to ram pressure stripping as it passes through the Virgo Cluster.]]

In the case of low-mass dwarf galaxies, quenching is also caused by interactions that do not require galaxies merging as one. One such phenomenon is ram pressure stripping, which happens when a dwarf galaxy passes through the dense, hot medium in the center of a galaxy cluster. Acting as a fluid, this intracluster medium will exert a drag force surpassing the gravitational potential of the passing galaxy and remove its gas through elongated tails.{{Cite journal |last=Bekki |first=Kenji |date=2009-11-11 |title=Ram-pressure stripping of halo gas in disc galaxies: implications for galactic star formation in different environments |journal=Monthly Notices of the Royal Astronomical Society |volume=399 |issue=4 |pages=2221–2230 |doi=10.1111/j.1365-2966.2009.15431.x |doi-access=free |arxiv=0907.4409 |bibcode=2009MNRAS.399.2221B |issn=0035-8711}}{{Cite journal |last1=Roediger |first1=E. |last2=Brüggen |first2=M. |last3=Owers |first3=M. S. |last4=Ebeling |first4=H. |last5=Sun |first5=M. |date=2014-09-01 |title=Star formation in shocked cluster spirals and their tails |url=https://academic.oup.com/mnrasl/article/443/1/L114/1054937 |journal=Monthly Notices of the Royal Astronomical Society: Letters |volume=443 |issue=1 |pages=L114–L118 |doi=10.1093/mnrasl/slu087 |doi-access=free |issn=1745-3925|arxiv=1405.1033 }} Ram pressure stripping has been observed in clusters like Virgo. Cosmological simulations show that this procedure has a rapid timescale of 200 million years,{{Cite journal |last1=Mao |first1=Zhiying |last2=Kodama |first2=Tadayuki |last3=Pérez-Martínez |first3=Jose Manuel |last4=Suzuki |first4=Tomoko L. |last5=Yamamoto |first5=Naoaki |last6=Adachi |first6=Kouta |date=2022-10-01 |title=Revealing impacts of stellar mass and environment on galaxy quenching |url=https://www.aanda.org/articles/aa/full_html/2022/10/aa43733-22/aa43733-22.html |journal=Astronomy & Astrophysics |language=en |volume=666 |pages=A141 |doi=10.1051/0004-6361/202243733 |arxiv=2208.00722 |bibcode=2022A&A...666A.141M |issn=0004-6361}} and can take out all the gas in dwarf galaxies whose stellar mass is less than 10⁷ solar masses.{{Cite journal |last1=Simpson |first1=Christine M |last2=Grand |first2=Robert J J |last3=Gómez |first3=Facundo A |last4=Marinacci |first4=Federico |last5=Pakmor |first5=Rüdiger |last6=Springel |first6=Volker |last7=Campbell |first7=David J R |last8=Frenk |first8=Carlos S |date=2018-07-21 |title=Quenching and ram pressure stripping of simulated Milky Way satellite galaxies |url=https://academic.oup.com/mnras/article/478/1/548/4952015 |journal=Monthly Notices of the Royal Astronomical Society |volume=478 |issue=1 |pages=548–567 |doi=10.1093/mnras/sty774 |doi-access=free |issn=0035-8711|arxiv=1705.03018 }}

Another mechanism involves a cutoff of the gas supply that comes from the hot corona around a dwarf galaxy.{{Cite journal |last1=Kawata |first1=Daisuke |last2=Mulchaey |first2=John S. |date=2008-01-10 |title=Strangulation in Galaxy Groups |url=https://iopscience.iop.org/article/10.1086/526544 |journal=The Astrophysical Journal |language=en |volume=672 |issue=2 |pages=L103–L106 |doi=10.1086/526544 |arxiv=0707.3814 |bibcode=2008ApJ...672L.103K |issn=0004-637X}} In theory, the gas in this corona can cool off, fall into the galactic disk, and fuel star formation. However, as the galaxy passes through a dense environment, ram pressure can remove this hot gas from the galaxy at a slower pace than stripping.{{Cite journal |last1=Vijayaraghavan |first1=Rukmani |last2=Ricker |first2=Paul M. |date=2015-05-21 |title=Ram pressure stripping of hot coronal gas from group and cluster galaxies and the detectability of surviving X-ray coronae |url=https://academic.oup.com/mnras/article/449/3/2312/1133846 |journal=Monthly Notices of the Royal Astronomical Society |volume=449 |issue=3 |pages=2312–2335 |doi=10.1093/mnras/stv476 |doi-access=free |issn=0035-8711|arxiv=1503.01121 }} As a result, the gas supply will be cut off over a prolonged period of a few billion years. This phenomenon has multiple names in the literature, including slow quenching, starvation, and strangulation.{{Cite journal |last1=Bekki |first1=Kenji |last2=Couch |first2=Warrick J. |last3=Shioya |first3=Yasuhiro |date=October 2002 |title=Passive Spiral Formation from Halo Gas Starvation: Gradual Transformation into S0s |url=https://iopscience.iop.org/article/10.1086/342221 |journal=The Astrophysical Journal |language=en |volume=577 |issue=2 |pages=651–657 |doi=10.1086/342221 |arxiv=astro-ph/0206207 |bibcode=2002ApJ...577..651B |issn=0004-637X}}{{Cite journal |last1=Larson |first1=R. B. |last2=Tinsley |first2=B. M. |last3=Caldwell |first3=C. N. |date=1980 |title=The evolution of disk galaxies and the origin of S0 galaxies |url=http://adsabs.harvard.edu/doi/10.1086/157917 |journal=The Astrophysical Journal |language=en |volume=237 |pages=692 |doi=10.1086/157917 |bibcode=1980ApJ...237..692L |issn=0004-637X}}{{Cite journal |last1=Man |first1=Allison |last2=Belli |first2=Sirio |date=2018 |title=Star formation quenching in massive galaxies |url=https://www.nature.com/articles/s41550-018-0558-1 |journal=Nature Astronomy |language=en |volume=2 |issue=9 |pages=695–697 |doi=10.1038/s41550-018-0558-1 |arxiv=1809.00722 |bibcode=2018NatAs...2..695M |issn=2397-3366}}

Dwarf galaxies can also lose gas via harassment.{{Cite journal |last1=Moore |first1=Ben |last2=Katz |first2=Neal |last3=Lake |first3=George |last4=Dressler |first4=Alan |last5=Oemler |first5=Augustus |date=1996 |title=Galaxy harassment and the evolution of clusters of galaxies |url=https://www.nature.com/articles/379613a0 |journal=Nature |language=en |volume=379 |issue=6566 |pages=613–616 |doi=10.1038/379613a0 |arxiv=astro-ph/9510034 |bibcode=1996Natur.379..613M |issn=1476-4687}} This is when a galaxy falls into the center of a cluster and experiences frequent high-speed close encounters with the galaxies therein. Disturbed by these encounters, the in-falling galaxy can change shape and redistribute its material (much like the merger case), leading to a starburst that eventually drains it of its gas contents.{{Cite journal |last1=Boselli |first1=Alessandro |last2=Gavazzi |first2=Giuseppe |date=2006 |title=Environmental Effects on Late-Type Galaxies in Nearby Clusters |url=http://iopscience.iop.org/article/10.1086/500691 |journal=Publications of the Astronomical Society of the Pacific |language=en |volume=118 |issue=842 |pages=517–559 |doi=10.1086/500691 |arxiv=astro-ph/0601108 |bibcode=2006PASP..118..517B |issn=0004-6280}}

The application of words like stripping, starvation, strangulation, and harassment to galactic mechanisms has been criticized among astronomers for its unnecessary connotations of domestic and gender-based violence.{{Cite web |last=Madrid |first=Juan P. |title=The Language of Astronomy Is Needlessly Violent and Inaccurate |url=https://www.scientificamerican.com/article/the-language-of-astronomy-is-needlessly-violent-and-inaccurate/ |access-date=2025-05-13 |website=Scientific American |language=en}}{{Cite web |last1=June 21 |last2=Vallejo |first2=2018 {{!}} Jessie M. |last3=Comments |first3=Jorge G. F. Moreno Soto {{!}} |title=Intergalactic Pachamama: Kichwa Cosmology vs. Western Astrophysics |url=https://folklife.si.edu/magazine/intergalactic-pachamama-kichwa-cosmology-vs-western-astrophysics |access-date=2025-05-13 |website=Smithsonian Center for Folklife and Cultural Heritage |language=en-US}}{{Cite web |last1=Claremont |first1=Pomona College 333 N. College Way |last2=Ca 91711 |date=2022-02-14 |title=Pomona Professor Leads Research Into Galaxies Lacking Dark Matter {{!}} Pomona College in Claremont, California - Pomona College |url=https://www.pomona.edu/news/2022/02/14-pomona-professor-leads-research-galaxies-lacking-dark-matter |access-date=2025-05-13 |website=www.pomona.edu |language=en}} Additionally, terms like starvation and strangulation are seen as inaccurate, because the human processes that they originally describe often lead to death, while the dwarf galaxies that undergo these phenomena do not "die", but simply form stars at a more reduced rate.

Other than quenched or quiescent, a galaxy that has shut down its star formation can also be called passive or early-type. The latter description came from the Hubble tuning-fork diagram, where ellipticals and lenticulars, which are typically quenched, are placed on the left side, hence their classification as early (as opposed to late-type spiral galaxies, which are on the right side). There are misconceptions that Edwin Hubble arranged the diagram and named the galaxy types in such ways because he thought early-type ellipticals would evolve into late-type spirals;{{Cite web |date=2023-12-15 |title=Hubble Looks at a Late-type Galaxy - NASA Science |url=https://science.nasa.gov/missions/hubble/hubble-looks-at-a-late-type-galaxy/ |access-date=2025-05-12 |language=en-US}} however, he had warned in a paper from 1927 that the positioning on the diagram was not meant to show any evolution, and that “temporal connotations are made at one's peril.”{{Cite journal |last=Hubble |first=Edwin |date=1927 |title=The classification of spiral nebulae |url=https://adsabs.harvard.edu/full/1927Obs....50..276H |journal=The Observatory |volume=50 |pages=276–281 |bibcode=1927Obs....50..276H |via=SAO/NASA Astrophysics Data System (ADS)}}

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Category:Star formation

Category:Galaxies

Category:Supermassive black holes