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In the news this month: Chandra tells tails of extragalactic star formation

X-ray tails in Abell 3627
Two spectacular tails of X-ray emission have been found behind the galaxy known as ESO 130-001 in Abell 3627 CREDIT: X-ray: NASA/CXC/UVa/M. Sun, et al; H-alpha/Optical: SOAR (UVa/NOAO/UNC/CNPq-Brazil)/M.Sun et al.
Star formation is usually thought of as occurring mainly in the spiral arms of galaxies. In close encounters or collisions between galaxies, the orbits of these stars around the galactic disk can be disrupted, resulting in some stars being thrown out into intergalactic space. But new results from the Chandra X-ray Observatory suggest that, at least in some cases, stars can form outside the normal boundaries of galactic disks.

A team led by Ming Sun at the University of Virginia used the orbiting Chandra telescope to observe galaxies in a nearby rich cluster known as Abell 3627. What they found were several enormous tails of X-ray emission, trailing behind galaxies located in the cluster. Tails like these are made up of X-ray emitting gas which is stripped from a galaxy as it moves through the cluster. One of these galaxies, ESO 137-001, was already known to have one X-ray tail which extends approximately 260 thousand light years from the galaxy itself, but in these observations the team found a second tail apparently associated with the same galaxy. This new tail is of a similar length to the first, but is both fainter and narrower. Both the widths and temperatures of the tails remain surprisingly constant over their entire lengths, and these properties present challenges to current models and simulations of such systems. A similar tail of about half the length was also detected behind ESO 137-002, another similar galaxy in the same cluster.

Together with observations using telescopes operating in other parts of the electromagnetic spectrum, the research also shows the first unambiguous evidence of star formation in the material stripped from a galaxy. Rather than forming in the galactic disk as normal, these stars are forming in the gas stripped from the disk as the galaxy moves through the tenuous gas in the cluster.

X-ray tails are rare, and double-tails are extremely rare, so one question is, why should there be two bright X-ray tails visible in the same cluster? In their paper, published in the Astrophysical Journal, the researchers suggest that (aside from coincidence) the high ambient pressure in this particular cluster could play a role, making the X-ray tails denser and more luminous. If this is the case, the high pressure environment would also be helping the process of extra-galactic star formation.

Sun, M., Donahue, M., Roediger, E., Nulsen, P., Voit, G., Sarazin, C., Forman, W., & Jones, C. (2010). SPECTACULAR X-RAY TAILS, INTRACLUSTER STAR FORMATION, AND ULXs IN A3627 The Astrophysical Journal, 708 (2), 946-964 DOI: 10.1088/0004-637X/708/2/946

Posted by Megan on Tuesday 02nd Feb 2010 (04:18 UTC) | Add a comment | Permalink


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