More from Chris Lintott:<\/strong><\/em><\/p>\n Look at these systems with X-ray eyes \u2013 or, as Harvard\u2019s Nazma Islam and colleagues do, rummage through the archives of the XMM-Newton space telescope \u2013 and they look different, with dramatic jets and hot gas swirling around the brightly glowing black holes<\/a> at their centres.<\/p>\n The team has assembled an atlas of such observations (there is a long-standing astronomical tradition of using \u2018atlas\u2019 to mean not a book of maps, but a collection of images).<\/p>\n The galaxies included have already featured in a similar collection of observations with NASA\u2019s Chandra X-ray Observatory, but XMM is a larger telescope, operating at slightly shorter wavelengths, and Chandra has a smaller field of view than its European counterpart.<\/p>\n While the Chandra observations told astronomers a lot about what was happening to the galaxy itself, a broader perspective is needed to understand how the systems interact with their surroundings.<\/p>\n As hot gas expelled from galaxies can alter the environment of neighbouring galaxies, or even affect them directly, this is important.<\/p>\n Take NGC 1550, for example. The Chandra image shows a nice, smooth halo of hot gas throughout most of the galaxy, but XMM confirms the presence of a bar-like feature at the galaxy\u2019s nucleus, aligned roughly east to west.<\/p>\n From observations of the galaxy\u2019s spectrum, we can tell this east to west feature is formed of cooler gas, and it seems to line up with jets that others have seen in radio observation.<\/p>\n The jets come from activity associated with the galaxy\u2019s central supermassive black hole, and they appear to have captured cooler gas associated with stars in the inner regions of the system, carrying it out into the galaxy.<\/p>\n The other galaxy considered in detail, NGC 4636, shows what can happen when these processes happen on a large scale.<\/p>\n Here, gas is being expelled from the galaxy altogether, shocking material in the intergalactic medium and heating it up so it glows brightly in the XMM image.<\/p>\n The observations also reveal the metallicity of the gas \u2013 the proportion of elements heavier than hydrogen and helium, which, as they are produced by previous generation of stars, provide a guide to how processed by star formation the gas has been.<\/p>\n Each of the other 36 galaxies will have their own stories to tell.<\/p>\n This kind of work in the archives, which reflects a huge amount of effort to reprocess and display archived data in a uniform and useful fashion, doesn\u2019t always get enough attention.<\/p>\n But catalogues like these are the raw materials for future science \u2013 and it\u2019s also sometimes just fun to look at pictures of galaxies, especially when you pick the right wavelength.<\/p>\n![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/08\/Virgo-cluster-7ac757c.jpeg?quality=90&resize=620%2C478"\" "\\"\"A\\"")
<\/div>![\""X-ray\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/08\/NGC-1550-892f7b5.jpg?quality=90&resize=620%2C309"\" "\\"\"NGC\\"")
<\/div>![\""A\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/08\/0144_xray-374747f-e1629886519229.jpg?quality=90&resize=620%2C483"\" "\\"\"Chandra\\"")
<\/div>![\""X-ray\"](\""https:\/\/images.immediate.co.uk\/production\/volatile\/sites\/25\/2021\/08\/ngc-4636-6a5c517.jpg?quality=90&resize=620%2C309"\" "\\"\"NGC\\"")
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