| Phoenix Cluster | |
|---|---|
_Chandra.jpg) The Phoenix Cluster, seen in this multi-wave length composite image of X-ray and visible light overlays. Note the two vast outer cavities, seen as large holes in the blue emission. Less pronounced inner cavities are to the top right and bottom left of the central galaxy, the brightest object in the image.[1] | |
| Observation data (EpochJ2000.0[2]) | |
| Constellation(s) | Phoenix |
| Right ascension | 23h 44m 40.9s[2] |
| Declination | −42° 41′ 54″[2] |
| Brightest member | Phoenix A (mag 18.2)[2][3] |
| Number of galaxies | 42 known[2] |
| Redshift | 0.597320±0.000150 (center)[4] |
| Distance | 2,640.6 ± 184.8megaparsecs (8.61 ± 0.60 billionlight-years) (present comoving) 1,796.38megaparsecs (5.86 billionlight-years) (light-travel)[3] |
| Binding mass | (1.26–2.5)×1015[4] M☉ |
| Other designations | |
| PhoenixCluster,SPT-CLJ2344-4243,SPT-CL J2344-4243[5] | |
ThePhoenix Cluster (SPT-CL J2344-4243) is a massive, Abell class type Igalaxy cluster located at its namesake, southernconstellation ofPhoenix. It was initially detected in 2010 during a 2,500 square degree survey of the southern sky using theSunyaev–Zeldovich effect by theSouth Pole Telescope collaboration.[5] It is one of the most massive galaxy clusters known, with the mass on the order of 2×1015M☉,[4] and is the most luminous X-ray cluster discovered, producing moreX-rays than any other known massive cluster.[4] It is located at a comoving distance of 8.61 billionlight-years (2.64gigaparsecs) from Earth. About 42 member galaxies were identified and currently listed in theSIMBAD Astronomical Database,[2] though the real number may be as high as 1,000 galaxies.[6]
The Phoenix Cluster was first reported in a paper by R. Williamson and colleagues during a survey by theSouth Pole Telescope inAntarctica,[5] being one of the 26 galaxy clusters identified by the survey. The detection has been conducted at frequencies between 95, 150, and 220 GHz, with 14 of the galaxy clusters detected have been previously identified, while 12 – including Phoenix Cluster, being new discoveries. The would-be named Phoenix Cluster (still identified by its numerical catalogue entry SPT-CL J2344–4243) has been remarked to be having "the largest X-ray luminosity of any cluster" described by the survey.[5] A bright, type-2 Seyfert galaxy has also been pronounced lying 19 arcseconds from the apparent center of the cluster that has been identified as2MASX J23444387-4243124,[5] which would later be named Phoenix A, the cluster's central galaxy.
Owing to its extreme properties, the Phoenix Cluster has been extensively studied and is considered one of the most important class of objects of its type. A multiwavelength observational study by M. McDonald and colleagues show that it has an extremely strongcooling flow rate (roughly 3,280M☉ per annum), described as a runaway cooling flow.[4] This measurement is one of the highest ever seen in the middle of a galaxy cluster. The very strong cooling flow, in contrast to other galaxy clusters, has been a suggested result of the feedback mechanism to prevent a runaway cooling flow which may not be established yet in the Phoenix Cluster;[4] the heating mechanism expected to be produced by the central black hole being inadequate to create a feedback (in contrast to thePerseus andVirgo clusters). This is further supported by the high starburst activity of the central galaxy Phoenix A, where stars are formed at 740M☉ per annum (compared to theMilky Way's 1M☉ per annum of star production); the central active galactic nucleus attested to not have been producing sufficient energy to ionize the galaxy's gas and prevent starburst activity.[7]
| Phoenix A | |
|---|---|
_from_DESI_Legacy_Imaging_Surveys%2c_Data_Release_9.png) Image of the central galaxy of the Phoenix cluster (Phoenix A) from DESI Legacy Imaging Surveys, Data Release 9. | |
| Observation data (J2000.0epoch) | |
| Right ascension | 23h 44m 43.89s[3] |
| Declination | −42° 43′ 12.4″[3] |
| Redshift | 0.597[3] |
| Heliocentric radial velocity | 179,072km/s |
| Apparent magnitude (V) | 18.80[3] |
| Characteristics | |
| Size | 110.48 kiloparsecs (360,300 light-years) (diameter;2MASS K-band total isophote)[3] |
| Other designations | |
| RBS 2043,2MASX J23444387-4243124, MRSS 292-067217, 2CXO J234443.9-424312,LEDA 3988894 | |
The central ellipticalcD galaxy of this cluster,Phoenix A (RBS 2043,2MASX J23444387-4243124), hosts anactive galactic nucleus that has been described as sharing both the properties of being aquasar and a type 2Seyfert galaxy, which is powered by a centralsupermassive black hole. The galaxy has an uncertain morphology. Based on the "total" aperture at the K-band, Phoenix A has anangular diameter of 16.20 arcseconds, corresponding to a largeisophotal diameter of 206.1kiloparsecs (672,200light-years), making it one of thelargest known galaxies discovered from Earth.[3]
Phoenix A also contains vast amounts of hot gas. More normal matter is present there than the total of all the other galaxies in the cluster. Data from observations indicate that hot gas is cooling in the central regions at a rate of3,820 M☉/yr, the highest ever recorded.[4]
It is also undergoing a massive starburst, the highest recorded in the middle of a galaxy cluster, although other galaxies at higher redshifts have a higher starburst rate(seeBaby Boom Galaxy).[8]
Observations by a variety of telescopes including theGALEX andHerschel space telescopes shows that it has been converting the material to stars at an exceptionally high rate of 740M☉ per year.[4] This is considerably higher than that ofNGC 1275 A, the central galaxy of thePerseus Cluster, where stars are formed at a rate around 20 times lower, or the one per year rate of star formation in theMilky Way.[9]
The central black hole of the Phoenix Cluster is the engine that drives both the Seyfert nucleus of Phoenix A, as well as the relativistic jets that produce the inner cavities in the cluster center. M. Brockamp and colleagues had used a modelling of the innermost stellar density of the central galaxy and theadiabatic process that fuels the growth of its central black hole to create a calorimetric tool to measure the black hole's mass.[10] The team deduced an energy conversion parameter and related it to the behavior of the hot intracluster gas, the AGN feedback parameter, and the dynamics and density profiles of the galaxy to create an evolutionary modelling of how the central black hole may have grown in the past.[10] In the case of Phoenix A, it has been shown to have far more extreme characteristics, with adiabatic models near the theoretical limitations.[10]
These models, as suggested by the paper, are indicative of a central black hole with estimated mass on the order of 100 billionM☉, possibly even exceeding this mass,[10] though the black hole's mass itself has not yet been measured through orbital mechanics. Such a high mass makes it potentially one of themost massive black holes known in theobservable universe. A black hole of this mass has:
Such a high mass may place it into a proposed category ofstupendously large black holes (SLABs), black holes that may have been seeded byprimordial black holes with masses that may reach 100 billion M☉ or more, larger than the upper maximum limit for at least luminous accretingblack holes hosted by disc galaxies of about 50 billion M☉[12]
In 2025, NASA’sJames Webb Space Telescope (JWST) revealed a key missing link in the Phoenix Cluster’s rapid star formation. Using mid-infrared spectroscopy, Webb detected an intermediate-temperature cooling gas (~540,000°F) that bridges the gap between the cluster’s hot gas (18 million°F) and cool gas (18,000°F) — a phenomenon unseen in other galaxy clusters.[13] This discovery confirms that the Phoenix Cluster sustains star formation despite its supermassive black hole, challenging previous models of how galaxy clusters regulate star birth.
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