Free Astronomy Magazine March-April 2019

35 MARCH-APRIL 2019 SPACE CHRONICLES Hubble Frontier Fields project, housed in the Mikulski Archive for Space Telescopes (MAST). The MHD is a measure of how far two subsets are from each other. The smaller the value of MHD, the more similar the two point sets are. This analysis showed that the intracluster light distribution seen in the Hubble Frontier Fields images matched the mass distribution of the six galaxy clusters better than did X-ray emis- spiring,” Trujillo said. “Still, I did not expect the results to be so precise. The implications for future space- based research are very exciting.” The astronomers used the Modified Hausdorff Distance (MHD), a metric used in shape matching, to measure the similarities between the con- tours of the intracluster light and the contours of the different mass maps of the clusters, which are pro- vided as part of the data from the sion, as derived from archived ob- servations from Chandra X-ray Ob- servatory’s Advanced CCD Imaging Spectrometer (ACIS). Beyond this initial study, Montes and Trujillo see multiple opportuni- ties to expand their research. To start, they would like to increase the radius of observation in the original six clus- ters, to see if the de- gree of tracing accu- racy holds up. Another important test of their method will be obser- vation and analysis of additional galaxy clus- ters by more research teams, to add to the data set and confirm their findings. The astronomers also look forward to the ap- plication of the same techniques with future powerful space-based telescopes like the James Webb Space Telescope and WFIRST, which will have even more sensitive instru- ments for resolving faint intracluster light in the distant universe. Trujillo would like to test scaling down the method from massive galaxy clusters to sin- gle galaxies. “It would be fantastic to do this at galactic scales, for example exploring the stellar halos. In prin- ciple, the same idea should work; the stars that surround the galaxy as a result of the merging activity should also be following the grav- itational potential of the galaxy, il- luminating the location and dis- tribution of dark matter.” T wo massive galaxy clusters — Abell S1063 (left) and MACS J0416.1-2403 (right) — display a soft blue haze, called intracluster light, embedded among innumerable galaxies. The intra- cluster light is produced by orphan stars that no longer belong to any single galaxy, having been thrown loose during a violent galaxy interaction, and now drift freely throughout the cluster of galaxies. [NASA, ESA, and M. Montes (University of New South Wales)] !