Black hole phoenix cluster
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Black Hole Feedback and Cooling Flows in the Phoenix Cluster
The Phoenix cluster is a unique galaxy cluster known for its extremely strong cooling flow and unusually high star formation rates in its central galaxy. This makes it an important system for studying the interplay between black hole activity, cooling gas, and star formation.
Cooling Flow Problem and Black Hole Regulation
In many galaxy clusters, the hot gas in the center should cool rapidly, but observations show much less star formation than expected. This is called the "cooling flow problem." In the Phoenix cluster, new observations using the James Webb Space Telescope have mapped gas at intermediate temperatures and found evidence for a recent, rapid cooling episode. This episode led to a short-lived spike in the cooling rate, estimated at 5,000–23,000 solar masses per year. The data show that black hole feedback not only regulates but can also promote cooling in the cluster core, highlighting the complex role of the central black hole in controlling the cooling and heating of the gas .
AGN Feedback, Radio Bubbles, and Mini-Halo
The central black hole in the Phoenix cluster is very active, producing both intense radiation and powerful radio jets. These jets inflate large bubbles in the hot gas, which are visible in radio observations. The bubbles interact with the surrounding gas, lifting cold molecular filaments and possibly triggering the formation of new cold gas through thermal instabilities. This process helps explain how feedback from the black hole can both heat the gas and stimulate the production of cold gas needed for further feedback and star formation .
Radio observations have also revealed a mini-halo in the Phoenix cluster, likely formed by turbulence from sloshing motions in the cluster core, possibly due to a recent merger. The feedback from the black hole appears less efficient at reheating the gas in this massive cluster, which may be due to the black hole being underweight for the cluster's size or due to variability in the black hole's activity over time .
Black Hole Mass and Feedback Cycles
The central black hole in the Phoenix cluster is a candidate for being one of the most massive known, possibly reaching up to 100 billion solar masses. Such a massive black hole could have a significant impact on the structure of the central galaxy and the regulation of cooling flows. However, in very massive clusters like Phoenix, the black hole may not be able to provide enough feedback to fully stop the cooling, leading to the observed high star formation rates .
Simulations suggest that the Phoenix cluster is currently at the end of a cooling phase, where a new outburst from the black hole has started but has not yet stopped the cooling. This phase of high cooling and star formation is expected to last for about 100 million years, after which feedback from the black hole may again suppress cooling and star formation .
Conclusion
The Phoenix cluster provides a rare view of a galaxy cluster where the balance between cooling and heating by the central black hole is temporarily tipped in favor of rapid cooling and star formation. Observations show that black hole feedback is a complex process that can both suppress and promote cooling, depending on the timing and strength of outbursts. The Phoenix cluster's massive black hole, strong cooling flow, and active feedback make it a key system for understanding how black holes regulate the growth and evolution of galaxies in the most massive clusters 12345.
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