The inaugural issue of Nature Astronomy features the work of F. Andrade-Santos
The most recent work of Felipe Andrade-Santos, X2002, features in the very first issue of Nature Astronomy, which was also selected to be on the cover.
"The case for electron re-acceleration at galaxy cluster shocks" is the title of the most recent work of Reinout van Weeren, Felipe Andrade-Santos, and collaborators, and has just been published on the first issue of Nature Astronomy. "Astronomers have discovered a cosmic one-two punch unlike any ever seen before. Two of the most powerful phenomena in the Universe, a supermassive black hole, and the collision of giant galaxy clusters, have combined to create a stupendous cosmic particle accelerator." wrote Chandra X-ray Observatory, NASA's flagship mission for X-ray astronomy, in its press release "Astronomers Discover Powerful Cosmic Double Whammy”.
In this article, Reinout, Felipe, and collaborators have found the most compelling evidence for electron re-acceleration at clusters shocks to date. “Clusters of galaxies are the largest structures in the universe. The components of their visible matter are galaxies and a very hot and dilute gas. Clusters are formed via accretion of matter and mergers with other structures, such as galaxy groups and clusters. When clusters collide, shock waves are generated in their dilute and hot gas, travelling through the clusters for hundreds of millions of years. At the location of these shocks, astronomers have observed bright radio emission in many clusters, which we call radio relics. The question that remained open for several years was the origin of these very energetic electrons that could emit in the radio band. Two competing theories were largely invoked to explain it. The first would require that electrons from this hot and dilute plasma would accelerate from keV energies to GeV when compressed by the shock wave. The calculations, however, wouldn’t match the observed strength of cluster shocks. The second theory would suggest that pre-accelerated, relativistic electrons already existed in the regions where we observed these bright radio emissions, so the cluster shock would need to increase the energy of these electrons by just a factor of few, so they could emit in radio.”, said Felipe.
In the work published in Nature Astronomy, Reinout, Felipe, and their collaborators analyzed radio, X-ray, and optical data from the merging galaxy cluster Abell 3411-3412. That allowed them to find the best evidence for electron re-acceleration at clusters shocks to date. “For the first time we observed a clear connection between a radio relic and a radio galaxy, clearly indicating that the electrons at the relic region originated from a supermassive black hole residing in the nucleus of this galaxy. They were first accelerated by the supermassive black hole, and then re-accelerated by the cluster shock.”, added Felipe.
"It's almost like launching a rocket into low-Earth orbit and then getting shot out of the Solar System by a second rocket blast," said Felipe. "These particles are among the most energetic particles observed in the Universe, thanks to the double injection of energy."
Felipe Andrade-Santos is a post-doctoral research fellow at the Harvard-Smithsonian Center for Astrophysics (CfA). He first went to the CfA in 2005, as part of his “Stage Scientifique” from École Polytechnique.