Galaxies, with billions of stars revolving around a supermassive black hole, are accompanied by a large spherical halo of gas that surrounds it. This halo reaches much farther than the main population of stars, as if it were a galactic atmosphere. In it reside diffuse hot gas, dark matter and some stars.
Now the Hubble Space Telescope has studied the Andromeda halo, the closest galaxy to the Milky Way stretching more than 1 million light-years from the galaxy, which itself is 220,000 light-years across. The study, which has been published in The Astrophysical Journal, highlights that the halo is a very complex structure due to the internal processes of the galaxy.
“The outer layer is softer and warmer. This difference is a likely result of the impact of supernova activity on the disk of the galaxy that more directly affects the inner halo,” explains Nicolas Lehner of the University of Notre Dame.
These incredible observations were made possible by the AMIGA (Andromeda Ionized Gas Absorption Map) Project, which observed 46 quasars in the line of sight of where the halo was expected to be. The quasars were used as “backlights” to illuminate the diffuse halo so that it could be studied by the Hubble telescope.
“Understanding the huge gas halos that surround galaxies is immensely important,” explained co-researcher Samantha Berek of Yale University. “This reservoir of gas contains fuel for future star formation within the galaxy, as well as outputs from events such as supernovae. It is full of clues about the past and future evolution of the galaxy, and we can finally study it in great detail in our closest galactic neighbor . “
Referencia: Project AMIGA: The Circumgalactic Medium of Andromeda. Nicolas Lehner, Samantha C. Berek, J. Christopher Howk, Bart P. Wakker, Jason Tumlinson, Edward B. Jenkins, J. Xavier Prochaska, Ramona Augustin, Suoqing Ji, Claude-André Faucher-Giguère Published 2020 August 27 • © 2020. The American Astronomical Society.
