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Abell 68

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Abell 68 BCG (short for Abell 68 Brightest Cluster Galaxy), also known as PGC 1360619, is a massive 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 and has a redshift of 0.24, meaning it is located 3.6 billion light-years from Earth.[1]

Characteristics

Abell 68 BCG has a light profile described by a de Vaucouleurs surface brightness law, μ(r) ə r1/4, over a large range in its radius[2] and fitted to the inner regions.[3] 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.[4] 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.[5] On top of that, the galaxy is known to have a near-infrared luminosity range of LX > 5 × 1044 erg s-1.[6]

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.[7] Presumably, Abell 68 BCG was formed from galaxy mergers involving smaller spiral or elliptical galaxies.[8] 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.[9][10]

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.[11] The star formation rate in Abell 68 BCG is estimated to be SFR = 1-150 M ⊙ yr-1,[12] 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.[11]

Gravitational lens in Abell 68 BCG

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.[13] 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.[14] The object 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]

Abell 68

The galaxy cluster where Abell 68 BCG is residing is found to have temperatures between 1-10 keV and luminosity range of 6 × 1042 to 11 × 1044 erg s-1.[15] It is dynamically relaxed[16] but shows disturbed structures indicating the cluster is merging.[17] 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.[18][19] 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.[20]

Moreover, Abell 68 is found to be an active accreting cluster with a clustercentric radius of rsp/r200,m = 1.291 ± 0.062 presenting a splashback feature[21] 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.[22]

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.[23]

Like Abell 68 BCG, the cluster also acts as a gravitational lens. Through researchers present Spitzer and IRAC surveys of H-faint (H 160 ≳ 26.4, < 5σ) sources in 101 lensing cluster fields, they were able to several galaxies found massive (median M star = 1010.3±0.3 M ⊙), dust-obscured (A V = 2.6 ± 0.3) and lying at redshifts of z = 3.9 ± 0.4.[24]

References

  1. ^ "Your NED Search Results". ned.ipac.caltech.edu. Retrieved 2024-06-18.
  2. ^ de Vaucouleurs, Gerard (1948-01-01). "Recherches sur les Nebuleuses Extragalactiques". Annales d'Astrophysique. 11: 247. ISSN 0365-0499.
  3. ^ Kormendy, John; Djorgovski, S. (1989-01-01). "Surface photometry and the structure of elliptical galaxies". Annual Review of Astronomy and Astrophysics. 27: 235–277. doi:10.1146/annurev.aa.27.090189.001315. ISSN 0066-4146.
  4. ^ Hogan, M. T.; Edge, A. C.; Hlavacek-Larrondo, J.; Grainge, K. J. B.; Hamer, S. L.; Mahony, E. K.; Russell, H. R.; Fabian, A. C.; McNamara, B. R.; Wilman, R. J. (2015-10-01). "A comprehensive study of the radio properties of brightest cluster galaxies". Monthly Notices of the Royal Astronomical Society. 453: 1201–1222. doi:10.1093/mnras/stv1517. ISSN 0035-8711.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  5. ^ Lin, Yen-Ting; Huang, Hung-Jin; Chen, Yen-Chi (2018-05-01). "An Analysis Framework for Understanding the Origin of Nuclear Activity in Low-power Radio Galaxies". The Astronomical Journal. 155: 188. doi:10.3847/1538-3881/aab5b4. ISSN 0004-6256.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  6. ^ Stott, J. P.; Edge, A. C.; Smith, G. P.; Swinbank, A. M.; Ebeling, H. (2008-03-01). "Near-infrared evolution of brightest cluster galaxies in the most X-ray luminous clusters since z = 1". Monthly Notices of the Royal Astronomical Society. 384: 1502–1510. doi:10.1111/j.1365-2966.2007.12807.x. ISSN 0035-8711.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  7. ^ Sohn, Jubee; Geller, Margaret J.; Diaferio, Antonaldo; Rines, Kenneth J. (2020-03-01). "Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters". The Astrophysical Journal. 891: 129. doi:10.3847/1538-4357/ab6e6a. ISSN 0004-637X.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  8. ^ Toomre, Alar (1977-01-01). Mergers and Some Consequences.
  9. ^ Hernquist, Lars (1993-06-01). "Structure of Merger Remnants. II. Progenitors with Rotating Bulges". The Astrophysical Journal. 409: 548. doi:10.1086/172686. ISSN 0004-637X.
  10. ^ Hernquist, Lars (1992-12-01). "Structure of Merger Remnants. I. Bulgeless Progenitors". The Astrophysical Journal. 400: 460. doi:10.1086/172009. ISSN 0004-637X.
  11. ^ a b Hoffer, Aaron S.; Donahue, Megan; Hicks, Amalia; Barthelemy, R. S. (2012-03-01). "Infrared and Ultraviolet Star Formation in Brightest Cluster Galaxies in the ACCEPT Sample". The Astrophysical Journal Supplement Series. 199: 23. doi:10.1088/0067-0049/199/1/23. ISSN 0067-0049.
  12. ^ Rawle, T. D.; Edge, A. C.; Egami, E.; Rex, M.; Smith, G. P.; Altieri, B.; Fiedler, A.; Haines, C. P.; Pereira, M. J.; Pérez-González, P. G.; Portouw, J.; Valtchanov, I.; Walth, G.; van der Werf, P. P.; Zemcov, M. (2012-03-01). "The Relation between Cool Cluster Cores and Herschel-detected Star Formation in Brightest Cluster Galaxies". The Astrophysical Journal. 747: 29. doi:10.1088/0004-637X/747/1/29. ISSN 0004-637X.
  13. ^ a b Smith, Graham P.; Smail, Ian; Kneib, J. -P.; Davis, C. J.; Takamiya, M.; Ebeling, H.; Czoske, O. (2002-06-01). "A Hubble Space Telescope lensing survey of X-ray luminous galaxy clusters - III. A multiply imaged extremely red galaxy at z=1.6". Monthly Notices of the Royal Astronomical Society. 333: L16–L20. doi:10.1046/j.1365-8711.2002.05501.x. ISSN 0035-8711.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  14. ^ "Gravitational Lens Creates Cartoon of Space Invader - NASA Science". science.nasa.gov. Retrieved 2024-06-18.
  15. ^ 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.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  16. ^ 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)
  17. ^ 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.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  18. ^ 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.
  19. ^ information@eso.org. "Annotated Hubble image of Abell 68". www.spacetelescope.org. Retrieved 2024-06-18.
  20. ^ 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.
  21. ^ 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)
  22. ^ Zhu, Zhenghao; Xu, Haiguang; Hu, Dan; Shan, Chenxi; Zhu, Yongkai; Fan, Shida; Zhao, Yuanyuan; Gu, Liyi; Wu, Xiang-Ping (2021-02-01). "A Study of Gas Entropy Profiles of 47 Galaxy Clusters and Groups out to the Virial Radius". The Astrophysical Journal. 908: 17. doi:10.3847/1538-4357/abd327. ISSN 0004-637X.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  23. ^ Hashimoto, Yasuhiro; Böhringer, Hans; Umetsu, Keiichi (2022-04-01). "Dwarf galaxy luminosity functions and cluster environments". Monthly Notices of the Royal Astronomical Society. 511: 2796–2813. doi:10.1093/mnras/stac209. ISSN 0035-8711.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  24. ^ Sun, Fengwu; Egami, Eiichi; Pérez-González, Pablo G.; Smail, Ian; Caputi, Karina I.; Bauer, Franz E.; Rawle, Timothy D.; Fujimoto, Seiji; Kohno, Kotaro; Dudzevičiūtė, Ugnė; Atek, Hakim; Bianconi, Matteo; Chapman, Scott C.; Combes, Francoise; Jauzac, Mathilde (2021-12-01). "Extensive Lensing Survey of Optical and Near-infrared Dark Objects (El Sonido): HST H-faint Galaxies behind 101 Lensing Clusters". The Astrophysical Journal. 922: 114. doi:10.3847/1538-4357/ac2578. ISSN 0004-637X.{{cite journal}}: CS1 maint: unflagged free DOI (link)
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