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{{Infobox galaxy cluster|image=Hubble image of Abell 68 (8557242488).jpg|name=Abell 68|caption=Captured by the [[Hubble Space Telescope]] in 2012}}
{{Infobox galaxy cluster|image=Hubble image of Abell 68 (8557242488).jpg|name=Abell 68|caption=The galaxy cluster, Abell 68 captured by the [[Hubble Space Telescope]] in 2012|constellation=[[Pisces (constellation)|Pisces]]|ra=00h 37m 05.300s|brightest_member=Abell 68 BCG (PGC 1360619)|epoch=[[J2000.0]]|dec=+09d 09m 11.00s|distance=3.668 [[light years|Gly]] (1124.6 [[Megaparsecs|Mpc]])|redshift=0.254600|names=NSCS J003706+090916, ZwCl 0034.4+0851, PSZ2 G116.95-53.55|luminosity=Between 6 × 1042 and 11 × 1044 [[erg]] s<sup>-1|richness=1|bmtype=Type I}}


'''Abell 68''' is massive and rich [[galaxy cluster]] located in the constellation of [[Pisces (constellation)|Pisces]] with a projected [[Comoving and proper distances|co-moving distance]] of approximately 1124.6 [[Parsec|Mpc]] or 3.668 billion light-years away from [[Earth]]. The cluster is especially notable for its [[Gravitational lens|gravitational lensing]]<ref>{{Cite journal |last=Yuan |first=T. -T. |last2=Kewley |first2=L. J. |last3=Richard |first3=J. |date=2013-01-01 |title=The Metallicity Evolution of Star-forming Galaxies from Redshift 0 to 3: Combining Magnitude-limited Survey with Gravitational Lensing |url=https://ui.adsabs.harvard.edu/abs/2013ApJ...763....9Y |journal=The Astrophysical Journal |volume=763 |pages=9 |doi=10.1088/0004-637X/763/1/9 |issn=0004-637X}}</ref> and was first discovered by [[George O. Abell]] in 1958.<ref name=":0">{{Cite journal |last=Abell |first=George O. |date=1958-05-01 |title=The Distribution of Rich Clusters of Galaxies. |url=https://ui.adsabs.harvard.edu/abs/1958ApJS....3..211A |journal=The Astrophysical Journal Supplement Series |volume=3 |pages=211 |doi=10.1086/190036 |issn=0067-0049}}</ref>
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'''Abell 68 BCG''' (short for '''Abell 68 Brightest Cluster Galaxy'''), also known as '''PGC 1360619''', is a massive [[Type-cD galaxy|type-cD]] [[elliptical galaxy]] residing as the [[brightest cluster galaxy]] (BCG) of the Abell 68 [[galaxy cluster]]. The galaxy is located in the constellation of [[Pisces (constellation)|Pisces]] and has a [[redshift]] of 0.24, meaning it is located 3.6 billion [[Light-year|light-years]] from Earth.<ref>{{Cite web |title=Your NED Search Results |url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=2107909&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1 |access-date=2024-06-18 |website=ned.ipac.caltech.edu}}</ref>

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== History ==
Abell 68 is one of the original 2,712 [[Galaxy groups and clusters|galaxy clusters]] to be compiled inside the [[Abell catalogue|Abell Catalogue]] by George O. Abell who used the data that is retrieved from the [[National Geographic Society – Palomar Observatory Sky Survey|National Geographic Society - Palomar Observatory Sky Survey]].<ref name=":0" />


== Characteristics ==
== Characteristics ==
Abell 68 BCG has a light profile described by a de Vaucouleurs [[surface brightness]] law, μ(''r'') ə ''r''<sup>1/4</sup>, over a large range in its [[radius]]<ref>{{Cite journal |last=de Vaucouleurs |first=Gerard |date=1948-01-01 |title=Recherches sur les Nebuleuses Extragalactiques |url=https://ui.adsabs.harvard.edu/abs/1948AnAp...11..247D |journal=Annales d'Astrophysique |volume=11 |pages=247 |issn=0365-0499}}</ref> and fitted to the inner regions.<ref>{{Cite journal |last=Kormendy |first=John |last2=Djorgovski |first2=S. |date=1989-01-01 |title=Surface photometry and the structure of elliptical galaxies. |url=https://ui.adsabs.harvard.edu/abs/1989ARA&A..27..235K |journal=Annual Review of Astronomy and Astrophysics |volume=27 |pages=235–277 |doi=10.1146/annurev.aa.27.090189.001315 |issn=0066-4146}}</ref> It is classified as an [[emission line]] galaxy containing a powerful [[Astronomical radio source|radio source]] and a strong core component correlating with its [O III] 5007 Å [[Line-emission spectrum|line emission]] according to [[Multi-frequency signaling|multifrequency]] radio [[Observation|observations]] detected through data from [[Australia Telescope Compact Array]], Jansky [[Very Large Array]] and [[Very Long Baseline Array]] telescopes.<ref>{{Cite journal |last=Hogan |first=M. T. |last2=Edge |first2=A. C. |last3=Hlavacek-Larrondo |first3=J. |last4=Grainge |first4=K. J. B. |last5=Hamer |first5=S. L. |last6=Mahony |first6=E. K. |last7=Russell |first7=H. R. |last8=Fabian |first8=A. C. |last9=McNamara |first9=B. R. |last10=Wilman |first10=R. J. |date=2015-10-01 |title=A comprehensive study of the radio properties of brightest cluster galaxies |url=https://ui.adsabs.harvard.edu/abs/2015MNRAS.453.1201H |journal=Monthly Notices of the Royal Astronomical Society |volume=453 |pages=1201–1222 |doi=10.1093/mnras/stv1517 |issn=0035-8711}}</ref> Moreover, Abell 68 BCG is also a low-excitation [[radio galaxy]] with a 1.4 [[Hertz|GHz]] luminosity between 2 × 10<sup>23</sup> and 3 × 10<sup>25</sup> W Hz<sup>-1</sup> caused by [[Accretion (astrophysics)|accretion]] of cooling gas from the hot [[atmosphere]] that triggers its [[active galactic nucleus]] (AGN) as the BCG resides in massive [[dark matter halo]].<ref>{{Cite journal |last=Lin |first=Yen-Ting |last2=Huang |first2=Hung-Jin |last3=Chen |first3=Yen-Chi |date=2018-05-01 |title=An Analysis Framework for Understanding the Origin of Nuclear Activity in Low-power Radio Galaxies |url=https://ui.adsabs.harvard.edu/abs/2018AJ....155..188L |journal=The Astronomical Journal |volume=155 |pages=188 |doi=10.3847/1538-3881/aab5b4 |issn=0004-6256}}</ref> On top of that, the galaxy is known to have a [[Infrared|near-infrared]] luminosity range of LX > 5 × 1044 [[erg]] s<sup>-1</sup>.<ref>{{Cite journal |last=Stott |first=J. P. |last2=Edge |first2=A. C. |last3=Smith |first3=G. P. |last4=Swinbank |first4=A. M. |last5=Ebeling |first5=H. |date=2008-03-01 |title=Near-infrared evolution of brightest cluster galaxies in the most X-ray luminous clusters since z = 1 |url=https://ui.adsabs.harvard.edu/abs/2008MNRAS.384.1502S |journal=Monthly Notices of the Royal Astronomical Society |volume=384 |pages=1502–1510 |doi=10.1111/j.1365-2966.2007.12807.x |issn=0035-8711}}</ref>
Abell 68 has a [[temperature]] between 1-10 keV and luminosity range of 6 × 10<sup>42</sup> to 11 × 10<sup>44</sup> erg s<sup>-1</sup>.<ref>{{Cite journal |last=Molham |first=Mona |last2=Clerc |first2=Nicolas |last3=Takey |first3=Ali |last4=Sadibekova |first4=Tatyana |last5=Morcos |first5=A. B. |last6=Yousef |first6=Shahinaz |last7=Hayman |first7=Z. M. |last8=Lieu |first8=Maggie |last9=Raychaudhury |first9=Somak |last10=Gaynullina |first10=Evelina R. |date=2020-05-01 |title=X-ray properties of the X-CLASS-redMaPPer galaxy cluster sample: the luminosity-temperature relation |url=https://ui.adsabs.harvard.edu/abs/2020MNRAS.494..161M |journal=Monthly Notices of the Royal Astronomical Society |volume=494 |pages=161–177 |doi=10.1093/mnras/staa677 |issn=0035-8711}}</ref> It is dynamically relaxed<ref>{{Cite journal |last=Casas |first=Madeline C. |last2=Putnam |first2=Ky |last3=Mantz |first3=Adam B. |last4=Allen |first4=Steven W. |last5=Somboonpanyakul |first5=Taweewat |date=2024-05-01 |title=Optical Photometric Indicators of Galaxy Cluster Relaxation |url=https://ui.adsabs.harvard.edu/abs/2024ApJ...967...14C |journal=The Astrophysical Journal |volume=967 |pages=14 |doi=10.3847/1538-4357/ad41de |issn=0004-637X}}</ref> but shows disturbed structures indicating the cluster is merging.<ref>{{Cite journal |last=Yuan |first=Z. S. |last2=Han |first2=J. L. |last3=Wen |first3=Z. L. |date=2022-06-01 |title=Dynamical state of galaxy clusters evaluated from X-ray images |url=https://ui.adsabs.harvard.edu/abs/2022MNRAS.513.3013Y |journal=Monthly Notices of the Royal Astronomical Society |volume=513 |pages=3013–3021 |doi=10.1093/mnras/stac1037 |issn=0035-8711}}</ref> The galaxy cluster is also massive with an [[estimation]] mass of M<sub>500</sub> ≳ 2 × 10<sup>14</sup> M⊙. Several galaxies of the cluster are known to infall into the cluster as they pass through the dense [[intergalactic gas]] with [[ram pressure]] taking place to strip the gas.<ref>{{Cite journal |last=Koulouridis |first=E. |last2=Gkini |first2=A. |last3=Drigga |first3=E. |date=2024-04-01 |title=AGNs in massive galaxy clusters: Role of galaxy merging, infalling groups, cluster mass, and dynamical state |url=https://ui.adsabs.harvard.edu/abs/2024A&A...684A.111K |journal=Astronomy and Astrophysics |volume=684 |pages=A111 |doi=10.1051/0004-6361/202348212 |issn=0004-6361}}</ref><ref>{{Cite web |last=information@eso.org |title=Annotated Hubble image of Abell 68 |url=https://www.spacetelescope.org/images/heic1304b/ |access-date=2024-06-18 |website=www.spacetelescope.org |language=en}}</ref> As the process continues, these galaxies classified as [[Jellyfish galaxy|jellyfish galaxies]], suffer the rapid quenching of star formation as the AGN of the BCG is activated.<ref>{{Cite journal |last=Maier |first=C. |last2=Haines |first2=C. P. |last3=Ziegler |first3=B. L. |date=2022-02-01 |title=Star-formation quenching of cluster galaxies as traced by metallicity and presence of active galactic nuclei, and galactic conformity |url=https://ui.adsabs.harvard.edu/abs/2022A&A...658A.190M |journal=Astronomy and Astrophysics |volume=658 |pages=A190 |doi=10.1051/0004-6361/202141498 |issn=0004-6361}}</ref>


The galaxy is known to have a quiescent appearance with a large [[velocity dispersion]] of σ > 160 km s<sup>-1</sup> and much steeper through researchers constructing a velocity dispersion function of D<sub>n</sub>4000 > 1.5 and within R<sub>200</sub>.<ref>{{Cite journal |last=Sohn |first=Jubee |last2=Geller |first2=Margaret J. |last3=Diaferio |first3=Antonaldo |last4=Rines |first4=Kenneth J. |date=2020-03-01 |title=Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters |url=https://ui.adsabs.harvard.edu/abs/2020ApJ...891..129S |journal=The Astrophysical Journal |volume=891 |pages=129 |doi=10.3847/1538-4357/ab6e6a |issn=0004-637X}}</ref> Presumably, Abell 68 BCG was formed from [[Galaxy merger|galaxy mergers]] involving smaller spiral or elliptical galaxies.<ref>{{Cite book |last=Toomre |first=Alar |url=https://ui.adsabs.harvard.edu/abs/1977egsp.conf..401T |title=Mergers and Some Consequences |date=1977-01-01}}</ref> As they collided, this creates [[dynamical friction]] that is combined with mutual [[Tidal force|tidal forces]]. The [[kinetic energy]] is then redistributed into [[Random energy model|random energy]], allowing these galaxies to merge together into a single amorphous, triaxial system resembling an elliptical galaxy like Abell 68 BCG.<ref>{{Cite journal |last=Hernquist |first=Lars |date=1993-06-01 |title=Structure of Merger Remnants. II. Progenitors with Rotating Bulges |url=https://ui.adsabs.harvard.edu/abs/1993ApJ...409..548H |journal=The Astrophysical Journal |volume=409 |pages=548 |doi=10.1086/172686 |issn=0004-637X}}</ref><ref>{{Cite journal |last=Hernquist |first=Lars |date=1992-12-01 |title=Structure of Merger Remnants. I. Bulgeless Progenitors |url=https://ui.adsabs.harvard.edu/abs/1992ApJ...400..460H |journal=The Astrophysical Journal |volume=400 |pages=460 |doi=10.1086/172009 |issn=0004-637X}}</ref>
Abell 68 is also an active accreting cluster with a clustercentric radius of r<sub>sp</sub>/r<sub>200,m</sub> = 1.291 ± 0.062 presenting a splashback feature<ref>{{Cite journal |last=Bianconi |first=Matteo |last2=Buscicchio |first2=Riccardo |last3=Smith |first3=Graham P. |last4=McGee |first4=Sean L. |last5=Haines |first5=Chris P. |last6=Finoguenov |first6=Alexis |last7=Babul |first7=Arif |date=2021-04-01 |title=LoCuSS: The Splashback Radius of Massive Galaxy Clusters and Its Dependence on Cluster Merger History |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...911..136B |journal=The Astrophysical Journal |volume=911 |pages=136 |doi=10.3847/1538-4357/abebd7 |issn=0004-637X}}</ref> with its gas entropy showing the total feedback energy per [[particle]] decreasing from ∼10 [[Electronvolt|keV]] at the center to about zero at ∼0.35r<sub>200</sub> implying the [[Limit inferior and limit superior|upper limit]] of the feedback efficiency of ∼0.02 for the [[supermassive black hole]] hosted in the center of the cluster's BCG.<ref>{{Cite journal |last=Zhu |first=Zhenghao |last2=Xu |first2=Haiguang |last3=Hu |first3=Dan |last4=Shan |first4=Chenxi |last5=Zhu |first5=Yongkai |last6=Fan |first6=Shida |last7=Zhao |first7=Yuanyuan |last8=Gu |first8=Liyi |last9=Wu |first9=Xiang-Ping |date=2021-02-01 |title=A Study of Gas Entropy Profiles of 47 Galaxy Clusters and Groups out to the Virial Radius |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...908...17Z |journal=The Astrophysical Journal |volume=908 |pages=17 |doi=10.3847/1538-4357/abd327 |issn=0004-637X}}</ref>


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According to researchers, Abell 68 contain several [[Dwarf galaxy|dwarf galaxies]] as cluster members. Through investigating their [[Luminous efficiency function|luminosity function]] of (M<sub>i</sub> < -15), they found these galaxies located at faint end of the cluster shows a flat [[slope]] (α ~ -1.2 to -1.4) but show steeper slope profiles at larger cluster-centric distance.<ref>{{Cite journal |last=Hashimoto |first=Yasuhiro |last2=Böhringer |first2=Hans |last3=Umetsu |first3=Keiichi |date=2022-04-01 |title=Dwarf galaxy luminosity functions and cluster environments |url=https://ui.adsabs.harvard.edu/abs/2022MNRAS.511.2796H |journal=Monthly Notices of the Royal Astronomical Society |volume=511 |pages=2796–2813 |doi=10.1093/mnras/stac209 |issn=0035-8711}}</ref>
Abell 68 BCG is also a [[starburst galaxy]]. According to observations from [[GALEX|Galaxy Evolution Explorer]] (GALEX), [[Spitzer Space Telescope]], and [[2MASS|Two Micron All Sky Survey]] (2MASS), the galaxy exhibits recent signs of [[star formation]] in the form of [[ultraviolet]] (38%) and [[Infrared|mid-infrared]] emission (43%) from 8 to 160 μm, despite its current old [[stellar population]].<ref name=":0">{{Cite journal |last=Hoffer |first=Aaron S. |last2=Donahue |first2=Megan |last3=Hicks |first3=Amalia |last4=Barthelemy |first4=R. S. |date=2012-03-01 |title=Infrared and Ultraviolet Star Formation in Brightest Cluster Galaxies in the ACCEPT Sample |url=https://ui.adsabs.harvard.edu/abs/2012ApJS..199...23H |journal=The Astrophysical Journal Supplement Series |volume=199 |pages=23 |doi=10.1088/0067-0049/199/1/23 |issn=0067-0049}}</ref> The star formation rate in Abell 68 BCG is estimated to be SFR = 1-150 M ⊙ yr<sup>-1</sup>,<ref>{{Cite journal |last=Rawle |first=T. D. |last2=Edge |first2=A. C. |last3=Egami |first3=E. |last4=Rex |first4=M. |last5=Smith |first5=G. P. |last6=Altieri |first6=B. |last7=Fiedler |first7=A. |last8=Haines |first8=C. P. |last9=Pereira |first9=M. J. |last10=Pérez-González |first10=P. G. |last11=Portouw |first11=J. |last12=Valtchanov |first12=I. |last13=Walth |first13=G. |last14=van der Werf |first14=P. P. |last15=Zemcov |first15=M. |date=2012-03-01 |title=The Relation between Cool Cluster Cores and Herschel-detected Star Formation in Brightest Cluster Galaxies |url=https://ui.adsabs.harvard.edu/abs/2012ApJ...747...29R |journal=The Astrophysical Journal |volume=747 |pages=29 |doi=10.1088/0004-637X/747/1/29 |issn=0004-637X}}</ref> suggesting the galaxy was enabled by presence of high-density, [[X-ray]]-emitting [[Interstellar medium|interstellar gas]] originating from the core of the cluster, providing necessary [[pressure]] and fuel to trigger more [[Star|stars]].<ref name=":0" />


== Gravitational lens in Abell 68 BCG ==
== Gravitational lensed galaxies ==
[[File:Gravitational Lens Creates Cartoon of Space Invader.jpg|thumb|Gravitational lensing has caused the background to be split and stretched, hence giving this appearance.]]
Abell 68 BCG is known to act as a [[gravitational lens]]. According to [[Hubble Space Telescope]], it was able to image an extremely red object, located at redshift z = 1.6 called EROJ003707.<ref name=":1">{{Cite journal |last=Smith |first=Graham P. |last2=Smail |first2=Ian |last3=Kneib |first3=J. -P. |last4=Davis |first4=C. J. |last5=Takamiya |first5=M. |last6=Ebeling |first6=H. |last7=Czoske |first7=O. |date=2002-06-01 |title=A Hubble Space Telescope lensing survey of X-ray luminous galaxy clusters - III. A multiply imaged extremely red galaxy at z=1.6 |url=https://ui.adsabs.harvard.edu/abs/2002MNRAS.333L..16S |journal=Monthly Notices of the Royal Astronomical Society |volume=333 |pages=L16–L20 |doi=10.1046/j.1365-8711.2002.05501.x |issn=0035-8711}}</ref> The light from the gravitational lens is found to distort the object into a shape of a cartoon [[alien]] from [[Space Invaders]], a cult 1970s [[video game]].<ref>{{Cite web |title=Gravitational Lens Creates Cartoon of Space Invader - NASA Science |url=https://science.nasa.gov/missions/hubble/gravitational-lens-creates-cartoon-of-space-invader/ |access-date=2024-06-18 |website=science.nasa.gov |language=en-US}}</ref> The object is revealed to be an L* early-type [[Disc galaxy|disk galaxy]] with its properties being shared by ~10 [[Percentage|percent]] of galaxies with (R-K)>=5.3 and K<=21. Looking at its evolution, researchers theorized; if the [[gas]] continues to cool inside the galaxy in the manner predicted via hierarchical [[Galaxy formation and evolution|galaxy formation]] models then EROJ003707 could evolve into a very luminous [[spiral galaxy]] in the present.<ref name=":1" />
Abell 68 presents a strong [[gravitational lens]] which it was able to detect far objects.<ref>{{Cite web |last=information@eso.org |title=Hubble image of Abell 68 |url=https://www.spacetelescope.org/images/heic1304a/ |access-date=2024-06-18 |website=www.spacetelescope.org |language=en}}</ref> According to [[Hubble Space Telescope]], it was able to image an extremely red object or a background [[galaxy]], located at redshift z = 1.6 called EROJ003707.<ref name=":12">{{Cite journal |last=Smith |first=Graham P. |last2=Smail |first2=Ian |last3=Kneib |first3=J. -P. |last4=Davis |first4=C. J. |last5=Takamiya |first5=M. |last6=Ebeling |first6=H. |last7=Czoske |first7=O. |date=2002-06-01 |title=A Hubble Space Telescope lensing survey of X-ray luminous galaxy clusters - III. A multiply imaged extremely red galaxy at z=1.6 |url=https://ui.adsabs.harvard.edu/abs/2002MNRAS.333L..16S |journal=Monthly Notices of the Royal Astronomical Society |volume=333 |pages=L16–L20 |doi=10.1046/j.1365-8711.2002.05501.x |issn=0035-8711}}</ref> The galaxy is found to be distorted by the lens, giving it shape of a cartoon [[alien]] from [[Space Invaders]], which is a cult 1970s [[video game]].<ref>{{Cite web |title=Gravitational Lens Creates Cartoon of Space Invader - NASA Science |url=https://science.nasa.gov/missions/hubble/gravitational-lens-creates-cartoon-of-space-invader/ |access-date=2024-06-18 |website=science.nasa.gov |language=en-US}}</ref> Furthermore the galaxy lens, is revealed to be an L* early-type [[Disc galaxy|disk galaxy]] with its properties being shared by ~10 [[Percentage|percent]] of galaxies with (R-K)>=5.3 and K<=21. Looking at its evolution, researchers theorized; if the [[gas]] continues to cool inside the galaxy in the manner predicted via hierarchical [[Galaxy formation and evolution|galaxy formation]] models then EROJ003707 could evolve into a very luminous [[spiral galaxy]] in the present.<ref name=":12" />


Researchers who presented [[Spitzer Space Telescope|Spitzer]] and [[Infrared Array Camera|IRAC]] surveys of H-faint (H 160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields, were able to detect several more distant [[Galaxy|galaxies]]. These are found massive with median M <sub>star</sub> = 10<sup>10.3±0.3</sup> M ⊙, have a [[star formation]] rate of = 100<sup>+60</sup><sub>-40</sub> M ⊙ yr-1 and being dust-obscured (A <sub>V</sub> = 2.6 ± 0.3) galaxies that located at various redshifts of z = 3.9 ± 0.4. According to them these are H-faint galaxies make up 16<sup>+13</sup><sub>-7</sub>% of the galaxies in the [[Stellar mass|stellar-mass]] range of 10<sup>10</sup> - 10<sup>11.2</sup> M ⊙ at z = 3 ~ 5, which contributes to 8<sup>+8</sup><sub>-4</sub>% of the cosmic star formation rate [[density]] in the epoch indicating the early phase of massive [[Galaxy formation and evolution|galaxy formation]].<ref>{{Cite journal |last=Sun |first=Fengwu |last2=Egami |first2=Eiichi |last3=Pérez-González |first3=Pablo G. |last4=Smail |first4=Ian |last5=Caputi |first5=Karina I. |last6=Bauer |first6=Franz E. |last7=Rawle |first7=Timothy D. |last8=Fujimoto |first8=Seiji |last9=Kohno |first9=Kotaro |last10=Dudzevičiūtė |first10=Ugnė |last11=Atek |first11=Hakim |last12=Bianconi |first12=Matteo |last13=Chapman |first13=Scott C. |last14=Combes |first14=Francoise |last15=Jauzac |first15=Mathilde |date=2021-12-01 |title=Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...922..114S |journal=The Astrophysical Journal |volume=922 |pages=114 |doi=10.3847/1538-4357/ac2578 |issn=0004-637X}}</ref>
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== Abell 68 ==
The galaxy cluster where Abell 68 BCG is residing is found to have [[Temperature|temperatures]] between 1-10 keV and luminosity range of 6 × 10<sup>42</sup> to 11 × 10<sup>44</sup> erg s<sup>-1</sup>.<ref>{{Cite journal |last=Molham |first=Mona |last2=Clerc |first2=Nicolas |last3=Takey |first3=Ali |last4=Sadibekova |first4=Tatyana |last5=Morcos |first5=A. B. |last6=Yousef |first6=Shahinaz |last7=Hayman |first7=Z. M. |last8=Lieu |first8=Maggie |last9=Raychaudhury |first9=Somak |last10=Gaynullina |first10=Evelina R. |date=2020-05-01 |title=X-ray properties of the X-CLASS-redMaPPer galaxy cluster sample: the luminosity-temperature relation |url=https://ui.adsabs.harvard.edu/abs/2020MNRAS.494..161M |journal=Monthly Notices of the Royal Astronomical Society |volume=494 |pages=161–177 |doi=10.1093/mnras/staa677 |issn=0035-8711}}</ref> It is dynamically relaxed<ref>{{Cite journal |last=Casas |first=Madeline C. |last2=Putnam |first2=Ky |last3=Mantz |first3=Adam B. |last4=Allen |first4=Steven W. |last5=Somboonpanyakul |first5=Taweewat |date=2024-05-01 |title=Optical Photometric Indicators of Galaxy Cluster Relaxation |url=https://ui.adsabs.harvard.edu/abs/2024ApJ...967...14C |journal=The Astrophysical Journal |volume=967 |pages=14 |doi=10.3847/1538-4357/ad41de |issn=0004-637X}}</ref> but shows disturbed structures indicating the cluster is merging.<ref>{{Cite journal |last=Yuan |first=Z. S. |last2=Han |first2=J. L. |last3=Wen |first3=Z. L. |date=2022-06-01 |title=Dynamical state of galaxy clusters evaluated from X-ray images |url=https://ui.adsabs.harvard.edu/abs/2022MNRAS.513.3013Y |journal=Monthly Notices of the Royal Astronomical Society |volume=513 |pages=3013–3021 |doi=10.1093/mnras/stac1037 |issn=0035-8711}}</ref> The galaxy cluster is also massive with an [[estimation]] mass of M<sub>500</sub> ≳ 2 × 10<sup>14</sup> M⊙. Several galaxies of the cluster are known to infall into the cluster as they pass through the dense [[intergalactic gas]] with [[ram pressure]] taking place to strip the gas.<ref>{{Cite journal |last=Koulouridis |first=E. |last2=Gkini |first2=A. |last3=Drigga |first3=E. |date=2024-04-01 |title=AGNs in massive galaxy clusters: Role of galaxy merging, infalling groups, cluster mass, and dynamical state |url=https://ui.adsabs.harvard.edu/abs/2024A&A...684A.111K |journal=Astronomy and Astrophysics |volume=684 |pages=A111 |doi=10.1051/0004-6361/202348212 |issn=0004-6361}}</ref><ref>{{Cite web |last=information@eso.org |title=Annotated Hubble image of Abell 68 |url=https://www.spacetelescope.org/images/heic1304b/ |access-date=2024-06-18 |website=www.spacetelescope.org |language=en}}</ref> As the process continues, these galaxies classified as [[Jellyfish galaxy|jellyfish galaxies]], suffer the rapid quenching of star formation as the AGN of the BCG is activated.<ref>{{Cite journal |last=Maier |first=C. |last2=Haines |first2=C. P. |last3=Ziegler |first3=B. L. |date=2022-02-01 |title=Star-formation quenching of cluster galaxies as traced by metallicity and presence of active galactic nuclei, and galactic conformity |url=https://ui.adsabs.harvard.edu/abs/2022A&A...658A.190M |journal=Astronomy and Astrophysics |volume=658 |pages=A190 |doi=10.1051/0004-6361/202141498 |issn=0004-6361}}</ref>


== Abell 68 BCG ==
Moreover, Abell 68 is found to be an active accreting cluster with a clustercentric radius of r<sub>sp</sub>/r<sub>200,m</sub> = 1.291 ± 0.062 presenting a splashback feature<ref>{{Cite journal |last=Bianconi |first=Matteo |last2=Buscicchio |first2=Riccardo |last3=Smith |first3=Graham P. |last4=McGee |first4=Sean L. |last5=Haines |first5=Chris P. |last6=Finoguenov |first6=Alexis |last7=Babul |first7=Arif |date=2021-04-01 |title=LoCuSS: The Splashback Radius of Massive Galaxy Clusters and Its Dependence on Cluster Merger History |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...911..136B |journal=The Astrophysical Journal |volume=911 |pages=136 |doi=10.3847/1538-4357/abebd7 |issn=0004-637X}}</ref> with its gas entropy showing the total feedback energy per [[particle]] decreasing from ∼10 [[Electronvolt|keV]] at the center to about zero at ∼0.35r<sub>200</sub> implying the [[Limit inferior and limit superior|upper limit]] of the feedback efficiency of ∼0.02 for the [[supermassive black hole]] hosted in the center of the cluster's BCG.<ref>{{Cite journal |last=Zhu |first=Zhenghao |last2=Xu |first2=Haiguang |last3=Hu |first3=Dan |last4=Shan |first4=Chenxi |last5=Zhu |first5=Yongkai |last6=Fan |first6=Shida |last7=Zhao |first7=Yuanyuan |last8=Gu |first8=Liyi |last9=Wu |first9=Xiang-Ping |date=2021-02-01 |title=A Study of Gas Entropy Profiles of 47 Galaxy Clusters and Groups out to the Virial Radius |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...908...17Z |journal=The Astrophysical Journal |volume=908 |pages=17 |doi=10.3847/1538-4357/abd327 |issn=0004-637X}}</ref>
{{Infobox galaxy|name=Abell 68 Brightest Cluster Galaxy|constellation name=[[Pisces (constellation)|Pisces]]|epoch=[[J2000.0]]|ra=00h 37m 06.86s|dec=+09d 09m 23.6s|z=0.249403|h_radial_v=74,769 [[kilometer per second|km/s]]|dist_ly=3.651 [[light year|Gly]] (1119.4 [[Megaparsec|Mpc]])|group_cluster=Abell 68|appmag_v=0.257|appmag_b=0.340|sbrightness=26.5|type=[[Brightest Cluster Galaxy|BrCLG]]|names=[[2MASX]] J00370686+0909236, [[Principal Galaxies Catalogue|PGC]] 1360619, [[Sloan Digital Sky Survey|SDSS]] J003706.84+090924.1, WISEA J003706.85+090924.0}}
⚫
The [[brightest cluster galaxy]] of Abell 68 or '''Abell 68 BCG''' (short for '''Abell 68 Brightest Cluster Galaxy'''), also known as '''PGC 1360619''', is a massive [[Type-cD galaxy|type-cD]] [[elliptical galaxy]] residing as dominant member of the cluster. It is located in the constellation of [[Pisces (constellation)|Pisces]] and has a [[redshift]] of 0.24.<ref>{{Cite web |title=Your NED Search Results |url=https://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Obj_id&objid=2107909&objname=1&img_stamp=YES&hconst=73.0&omegam=0.27&omegav=0.73&corr_z=1 |access-date=2024-06-18 |website=ned.ipac.caltech.edu}}</ref>


The galaxy has a light profile described by a de Vaucouleurs [[surface brightness]] law, μ(''r'') ə ''r''<sup>1/4</sup>, over a large range in its [[radius]]<ref>{{Cite journal |last=de Vaucouleurs |first=Gerard |date=1948-01-01 |title=Recherches sur les Nebuleuses Extragalactiques |url=https://ui.adsabs.harvard.edu/abs/1948AnAp...11..247D |journal=Annales d'Astrophysique |volume=11 |pages=247 |issn=0365-0499}}</ref> and fitted to the inner regions.<ref>{{Cite journal |last=Kormendy |first=John |last2=Djorgovski |first2=S. |date=1989-01-01 |title=Surface photometry and the structure of elliptical galaxies. |url=https://ui.adsabs.harvard.edu/abs/1989ARA&A..27..235K |journal=Annual Review of Astronomy and Astrophysics |volume=27 |pages=235–277 |doi=10.1146/annurev.aa.27.090189.001315 |issn=0066-4146}}</ref> It is classified as an [[emission line]] galaxy containing a powerful [[Astronomical radio source|radio source]] and a strong core component correlating with its [O III] 5007 Å [[Line-emission spectrum|line emission]] according to [[Multi-frequency signaling|multifrequency]] radio [[Observation|observations]] detected through data from [[Australia Telescope Compact Array]], Jansky [[Very Large Array]] and [[Very Long Baseline Array]] telescopes.<ref>{{Cite journal |last=Hogan |first=M. T. |last2=Edge |first2=A. C. |last3=Hlavacek-Larrondo |first3=J. |last4=Grainge |first4=K. J. B. |last5=Hamer |first5=S. L. |last6=Mahony |first6=E. K. |last7=Russell |first7=H. R. |last8=Fabian |first8=A. C. |last9=McNamara |first9=B. R. |last10=Wilman |first10=R. J. |date=2015-10-01 |title=A comprehensive study of the radio properties of brightest cluster galaxies |url=https://ui.adsabs.harvard.edu/abs/2015MNRAS.453.1201H |journal=Monthly Notices of the Royal Astronomical Society |volume=453 |pages=1201–1222 |doi=10.1093/mnras/stv1517 |issn=0035-8711}}</ref> Moreover, Abell 68 BCG is also a low-excitation [[radio galaxy]] with a 1.4 [[Hertz|GHz]] luminosity between 2 × 10<sup>23</sup> and 3 × 10<sup>25</sup> W Hz<sup>-1</sup> caused by [[Accretion (astrophysics)|accretion]] of cooling gas from the hot [[atmosphere]] that triggers its [[active galactic nucleus]] (AGN) as the BCG resides in massive [[dark matter halo]].<ref>{{Cite journal |last=Lin |first=Yen-Ting |last2=Huang |first2=Hung-Jin |last3=Chen |first3=Yen-Chi |date=2018-05-01 |title=An Analysis Framework for Understanding the Origin of Nuclear Activity in Low-power Radio Galaxies |url=https://ui.adsabs.harvard.edu/abs/2018AJ....155..188L |journal=The Astronomical Journal |volume=155 |pages=188 |doi=10.3847/1538-3881/aab5b4 |issn=0004-6256}}</ref> On top of that, the galaxy is known to have a [[Infrared|near-infrared]] luminosity range of LX > 5 × 1044 [[erg]] s<sup>-1</sup>.<ref>{{Cite journal |last=Stott |first=J. P. |last2=Edge |first2=A. C. |last3=Smith |first3=G. P. |last4=Swinbank |first4=A. M. |last5=Ebeling |first5=H. |date=2008-03-01 |title=Near-infrared evolution of brightest cluster galaxies in the most X-ray luminous clusters since z = 1 |url=https://ui.adsabs.harvard.edu/abs/2008MNRAS.384.1502S |journal=Monthly Notices of the Royal Astronomical Society |volume=384 |pages=1502–1510 |doi=10.1111/j.1365-2966.2007.12807.x |issn=0035-8711}}</ref>
⚫
According to researchers, Abell 68 contain several [[Dwarf galaxy|dwarf galaxies]] as cluster members. Through investigating their [[Luminous efficiency function|luminosity function]] of (M<sub>i</sub> < -15), they found these galaxies located at faint end of the cluster shows a flat [[slope]] (α ~ -1.2 to -1.4) but show steeper slope profiles at larger cluster-centric distance.<ref>{{Cite journal |last=Hashimoto |first=Yasuhiro |last2=Böhringer |first2=Hans |last3=Umetsu |first3=Keiichi |date=2022-04-01 |title=Dwarf galaxy luminosity functions and cluster environments |url=https://ui.adsabs.harvard.edu/abs/2022MNRAS.511.2796H |journal=Monthly Notices of the Royal Astronomical Society |volume=511 |pages=2796–2813 |doi=10.1093/mnras/stac209 |issn=0035-8711}}</ref>

The galaxy is known to have a quiescent appearance with a large [[velocity dispersion]] of σ > 160 km s<sup>-1</sup> and much steeper through researchers constructing a velocity dispersion function of D<sub>n</sub>4000 > 1.5 and within R<sub>200</sub>.<ref>{{Cite journal |last=Sohn |first=Jubee |last2=Geller |first2=Margaret J. |last3=Diaferio |first3=Antonaldo |last4=Rines |first4=Kenneth J. |date=2020-03-01 |title=Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters |url=https://ui.adsabs.harvard.edu/abs/2020ApJ...891..129S |journal=The Astrophysical Journal |volume=891 |pages=129 |doi=10.3847/1538-4357/ab6e6a |issn=0004-637X}}</ref> Presumably, Abell 68 BCG was formed from [[Galaxy merger|galaxy mergers]] involving smaller spiral or elliptical galaxies.<ref>{{Cite book |last=Toomre |first=Alar |url=https://ui.adsabs.harvard.edu/abs/1977egsp.conf..401T |title=Mergers and Some Consequences |date=1977-01-01}}</ref> As they collided, this creates [[dynamical friction]] that is combined with mutual [[Tidal force|tidal forces]]. The [[kinetic energy]] is then redistributed into [[Random energy model|random energy]], allowing these galaxies to merge together into a single amorphous, triaxial system resembling an elliptical galaxy like Abell 68 BCG.<ref>{{Cite journal |last=Hernquist |first=Lars |date=1993-06-01 |title=Structure of Merger Remnants. II. Progenitors with Rotating Bulges |url=https://ui.adsabs.harvard.edu/abs/1993ApJ...409..548H |journal=The Astrophysical Journal |volume=409 |pages=548 |doi=10.1086/172686 |issn=0004-637X}}</ref><ref>{{Cite journal |last=Hernquist |first=Lars |date=1992-12-01 |title=Structure of Merger Remnants. I. Bulgeless Progenitors |url=https://ui.adsabs.harvard.edu/abs/1992ApJ...400..460H |journal=The Astrophysical Journal |volume=400 |pages=460 |doi=10.1086/172009 |issn=0004-637X}}</ref>


Like Abell 68 BCG, the cluster also acts as a gravitational lens. Through researchers present Spitzer and [[Infrared Array Camera|IRAC]] surveys of H-faint (H 160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields, they were able to several [[Galaxy|galaxies]] found massive (median M star = 10<sup>10.3±0.3</sup> M ⊙), dust-obscured (A <sub>V</sub> = 2.6 ± 0.3) and lying at redshifts of z = 3.9 ± 0.4.<ref>{{Cite journal |last=Sun |first=Fengwu |last2=Egami |first2=Eiichi |last3=Pérez-González |first3=Pablo G. |last4=Smail |first4=Ian |last5=Caputi |first5=Karina I. |last6=Bauer |first6=Franz E. |last7=Rawle |first7=Timothy D. |last8=Fujimoto |first8=Seiji |last9=Kohno |first9=Kotaro |last10=Dudzevičiūtė |first10=Ugnė |last11=Atek |first11=Hakim |last12=Bianconi |first12=Matteo |last13=Chapman |first13=Scott C. |last14=Combes |first14=Francoise |last15=Jauzac |first15=Mathilde |date=2021-12-01 |title=Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters |url=https://ui.adsabs.harvard.edu/abs/2021ApJ...922..114S |journal=The Astrophysical Journal |volume=922 |pages=114 |doi=10.3847/1538-4357/ac2578 |issn=0004-637X}}</ref>
Abell 68 BCG is also a [[starburst galaxy]]. According to observations from [[GALEX|Galaxy Evolution Explorer]] (GALEX), [[Spitzer Space Telescope]], and [[2MASS|Two Micron All Sky Survey]] (2MASS), the galaxy exhibits recent signs of [[star formation]] in the form of [[ultraviolet]] (38%) and [[Infrared|mid-infrared]] emission (43%) from 8 to 160 μm, despite its current old [[stellar population]].<ref name=":02">{{Cite journal |last=Hoffer |first=Aaron S. |last2=Donahue |first2=Megan |last3=Hicks |first3=Amalia |last4=Barthelemy |first4=R. S. |date=2012-03-01 |title=Infrared and Ultraviolet Star Formation in Brightest Cluster Galaxies in the ACCEPT Sample |url=https://ui.adsabs.harvard.edu/abs/2012ApJS..199...23H |journal=The Astrophysical Journal Supplement Series |volume=199 |pages=23 |doi=10.1088/0067-0049/199/1/23 |issn=0067-0049}}</ref> The star formation rate in Abell 68 BCG is estimated to be SFR = 1-150 M ⊙ yr<sup>-1</sup>,<ref>{{Cite journal |last=Rawle |first=T. D. |last2=Edge |first2=A. C. |last3=Egami |first3=E. |last4=Rex |first4=M. |last5=Smith |first5=G. P. |last6=Altieri |first6=B. |last7=Fiedler |first7=A. |last8=Haines |first8=C. P. |last9=Pereira |first9=M. J. |last10=Pérez-González |first10=P. G. |last11=Portouw |first11=J. |last12=Valtchanov |first12=I. |last13=Walth |first13=G. |last14=van der Werf |first14=P. P. |last15=Zemcov |first15=M. |date=2012-03-01 |title=The Relation between Cool Cluster Cores and Herschel-detected Star Formation in Brightest Cluster Galaxies |url=https://ui.adsabs.harvard.edu/abs/2012ApJ...747...29R |journal=The Astrophysical Journal |volume=747 |pages=29 |doi=10.1088/0004-637X/747/1/29 |issn=0004-637X}}</ref> suggesting the galaxy was enabled by presence of high-density, [[X-ray]]-emitting [[Interstellar medium|interstellar gas]] originating from the core of the cluster, providing necessary [[pressure]] and fuel to trigger more [[Star|stars]].<ref name=":02" />


== References ==
== References ==
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[[Category:Gravitational lensing]]
[[Category:Gravitational lensing]]
[[Category:Pisces (constellation)]]
[[Category:Pisces (constellation)]]
[[Category:Abell objects]]
[[Category:Galaxy clusters]]
[[Category:Abell richness class 1]]

Revision as of 11:28, 18 June 2024

Abell 68
The galaxy cluster, Abell 68 captured by the Hubble Space Telescope in 2012
Observation data (Epoch J2000.0)
Constellation(s)Pisces
Right ascension00h 37m 05.300s
Declination+09d 09m 11.00s
Brightest memberAbell 68 BCG (PGC 1360619)
Richness class1
Bautz–Morgan classificationType I
Redshift0.254600
Distance3.668 Gly (1124.6 Mpc)
X-ray luminosityBetween 6 × 1042 and 11 × 1044 erg s-1
Other designations
NSCS J003706+090916, ZwCl 0034.4+0851, PSZ2 G116.95-53.55
See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters

Abell 68 is massive and rich galaxy cluster located in the constellation of Pisces with a projected co-moving distance of approximately 1124.6 Mpc or 3.668 billion light-years away from Earth. The cluster is especially notable for its gravitational lensing[1] and was first discovered by George O. Abell in 1958.[2]

History

Abell 68 is one of the original 2,712 galaxy clusters to be compiled inside the Abell Catalogue by George O. Abell who used the data that is retrieved from the National Geographic Society - Palomar Observatory Sky Survey.[2]

Characteristics

Abell 68 has a temperature between 1-10 keV and luminosity range of 6 × 1042 to 11 × 1044 erg s-1.[3] It is dynamically relaxed[4] but shows disturbed structures indicating the cluster is merging.[5] The galaxy cluster is also massive with an estimation mass of M500 ≳ 2 × 1014 M⊙. Several galaxies of the cluster are known to infall into the cluster as they pass through the dense intergalactic gas with ram pressure taking place to strip the gas.[6][7] As the process continues, these galaxies classified as jellyfish galaxies, suffer the rapid quenching of star formation as the AGN of the BCG is activated.[8]

Abell 68 is also an active accreting cluster with a clustercentric radius of rsp/r200,m = 1.291 ± 0.062 presenting a splashback feature[9] with its gas entropy showing the total feedback energy per particle decreasing from ∼10 keV at the center to about zero at ∼0.35r200 implying the upper limit of the feedback efficiency of ∼0.02 for the supermassive black hole hosted in the center of the cluster's BCG.[10]

According to researchers, Abell 68 contain several dwarf galaxies as cluster members. Through investigating their luminosity function of (Mi < -15), they found these galaxies located at faint end of the cluster shows a flat slope (α ~ -1.2 to -1.4) but show steeper slope profiles at larger cluster-centric distance.[11]

Gravitational lensed galaxies

Gravitational lensing has caused the background to be split and stretched, hence giving this appearance.

Abell 68 presents a strong gravitational lens which it was able to detect far objects.[12] According to Hubble Space Telescope, it was able to image an extremely red object or a background galaxy, located at redshift z = 1.6 called EROJ003707.[13] The galaxy is found to be distorted by the lens, giving it shape of a cartoon alien from Space Invaders, which is a cult 1970s video game.[14] Furthermore the galaxy lens, is revealed to be an L* early-type disk galaxy with its properties being shared by ~10 percent of galaxies with (R-K)>=5.3 and K<=21. Looking at its evolution, researchers theorized; if the gas continues to cool inside the galaxy in the manner predicted via hierarchical galaxy formation models then EROJ003707 could evolve into a very luminous spiral galaxy in the present.[13]

Researchers who presented Spitzer and IRAC surveys of H-faint (H 160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields, were able to detect several more distant galaxies. These are found massive with median M star = 1010.3±0.3 M ⊙, have a star formation rate of = 100+60-40 M ⊙ yr-1 and being dust-obscured (A V = 2.6 ± 0.3) galaxies that located at various redshifts of z = 3.9 ± 0.4. According to them these are H-faint galaxies make up 16+13-7% of the galaxies in the stellar-mass range of 1010 - 1011.2 M ⊙ at z = 3 ~ 5, which contributes to 8+8-4% of the cosmic star formation rate density in the epoch indicating the early phase of massive galaxy formation.[15]

Abell 68 BCG

Abell 68 Brightest Cluster Galaxy
Observation data (J2000.0 epoch)
ConstellationPisces
Right ascension00h 37m 06.86s
Declination+09d 09m 23.6s
Redshift0.249403
Heliocentric radial velocity74,769 km/s
Distance3.651 Gly (1119.4 Mpc)
Group or clusterAbell 68
Apparent magnitude (V)0.257
Apparent magnitude (B)0.340
Surface brightness26.5
Characteristics
TypeBrCLG
Other designations
2MASX J00370686+0909236, PGC 1360619, SDSS J003706.84+090924.1, WISEA J003706.85+090924.0

The brightest cluster galaxy of Abell 68 or Abell 68 BCG (short for Abell 68 Brightest Cluster Galaxy), also known as PGC 1360619, is a massive type-cD elliptical galaxy residing as dominant member of the cluster. It is located in the constellation of Pisces and has a redshift of 0.24.[16]

The galaxy has a light profile described by a de Vaucouleurs surface brightness law, μ(r) ə r1/4, over a large range in its radius[17] and fitted to the inner regions.[18] It is classified as an emission line galaxy containing a powerful radio source and a strong core component correlating with its [O III] 5007 Å line emission according to multifrequency radio observations detected through data from Australia Telescope Compact Array, Jansky Very Large Array and Very Long Baseline Array telescopes.[19] Moreover, Abell 68 BCG is also a low-excitation radio galaxy with a 1.4 GHz luminosity between 2 × 1023 and 3 × 1025 W Hz-1 caused by accretion of cooling gas from the hot atmosphere that triggers its active galactic nucleus (AGN) as the BCG resides in massive dark matter halo.[20] On top of that, the galaxy is known to have a near-infrared luminosity range of LX > 5 × 1044 erg s-1.[21]

The galaxy is known to have a quiescent appearance with a large velocity dispersion of σ > 160 km s-1 and much steeper through researchers constructing a velocity dispersion function of Dn4000 > 1.5 and within R200.[22] Presumably, Abell 68 BCG was formed from galaxy mergers involving smaller spiral or elliptical galaxies.[23] As they collided, this creates dynamical friction that is combined with mutual tidal forces. The kinetic energy is then redistributed into random energy, allowing these galaxies to merge together into a single amorphous, triaxial system resembling an elliptical galaxy like Abell 68 BCG.[24][25]

Abell 68 BCG is also a starburst galaxy. According to observations from Galaxy Evolution Explorer (GALEX), Spitzer Space Telescope, and Two Micron All Sky Survey (2MASS), the galaxy exhibits recent signs of star formation in the form of ultraviolet (38%) and mid-infrared emission (43%) from 8 to 160 μm, despite its current old stellar population.[26] The star formation rate in Abell 68 BCG is estimated to be SFR = 1-150 M ⊙ yr-1,[27] suggesting the galaxy was enabled by presence of high-density, X-ray-emitting interstellar gas originating from the core of the cluster, providing necessary pressure and fuel to trigger more stars.[26]

References

  1. ^ Yuan, T. -T.; Kewley, L. J.; Richard, J. (2013-01-01). "The Metallicity Evolution of Star-forming Galaxies from Redshift 0 to 3: Combining Magnitude-limited Survey with Gravitational Lensing". The Astrophysical Journal. 763: 9. doi:10.1088/0004-637X/763/1/9. ISSN 0004-637X.
  2. ^ a b Abell, George O. (1958-05-01). "The Distribution of Rich Clusters of Galaxies". The Astrophysical Journal Supplement Series. 3: 211. doi:10.1086/190036. ISSN 0067-0049.
  3. ^ Molham, Mona; Clerc, Nicolas; Takey, Ali; Sadibekova, Tatyana; Morcos, A. B.; Yousef, Shahinaz; Hayman, Z. M.; Lieu, Maggie; Raychaudhury, Somak; Gaynullina, Evelina R. (2020-05-01). "X-ray properties of the X-CLASS-redMaPPer galaxy cluster sample: the luminosity-temperature relation". Monthly Notices of the Royal Astronomical Society. 494: 161–177. doi:10.1093/mnras/staa677. ISSN 0035-8711.
  4. ^ Casas, Madeline C.; Putnam, Ky; Mantz, Adam B.; Allen, Steven W.; Somboonpanyakul, Taweewat (2024-05-01). "Optical Photometric Indicators of Galaxy Cluster Relaxation". The Astrophysical Journal. 967: 14. doi:10.3847/1538-4357/ad41de. ISSN 0004-637X.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  5. ^ Yuan, Z. S.; Han, J. L.; Wen, Z. L. (2022-06-01). "Dynamical state of galaxy clusters evaluated from X-ray images". Monthly Notices of the Royal Astronomical Society. 513: 3013–3021. doi:10.1093/mnras/stac1037. ISSN 0035-8711.
  6. ^ Koulouridis, E.; Gkini, A.; Drigga, E. (2024-04-01). "AGNs in massive galaxy clusters: Role of galaxy merging, infalling groups, cluster mass, and dynamical state". Astronomy and Astrophysics. 684: A111. doi:10.1051/0004-6361/202348212. ISSN 0004-6361.
  7. ^ information@eso.org. "Annotated Hubble image of Abell 68". www.spacetelescope.org. Retrieved 2024-06-18.
  8. ^ Maier, C.; Haines, C. P.; Ziegler, B. L. (2022-02-01). "Star-formation quenching of cluster galaxies as traced by metallicity and presence of active galactic nuclei, and galactic conformity". Astronomy and Astrophysics. 658: A190. doi:10.1051/0004-6361/202141498. ISSN 0004-6361.
  9. ^ Bianconi, Matteo; Buscicchio, Riccardo; Smith, Graham P.; McGee, Sean L.; Haines, Chris P.; Finoguenov, Alexis; Babul, Arif (2021-04-01). "LoCuSS: The Splashback Radius of Massive Galaxy Clusters and Its Dependence on Cluster Merger History". The Astrophysical Journal. 911: 136. doi:10.3847/1538-4357/abebd7. ISSN 0004-637X.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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