It's an astronomical peculiarity that in some ways we know more about other galaxies than we do about our own. Scientists have examined the energy coming from the center of thousands of other spiral galaxies in visible light. But for our own Milky Way, that knowledge is blocked by thick clouds of gas and dust.
A team of researchers examined decades of data from the Wisconsin H-Alpha Mapper telescope (WHAM) for clues about the Milky Way's energy. Their results are in a paper titled "Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas."
[...] There's an enormous amount of hydrogen near the center of the Milky Way. That hydrogen is ionized by the energy from the galactic center. As an ionized gas, it's had its electrons stripped away. The WHAM telescope is designed to see the ionized hydrogen, which appears red when viewed with the 'scope.
It's not just that the hydrogen is ionized. After a gas is ionized, the ions usually recombine to neutrality in a short period of time. The fact that all of this hydrogen is continually ionized by a source of energy is the link between the WHAM data and the energy at the center of the Milky Way. Astronomers have thought that the source of energy for this ionization is star formation, but that's not conclusive.
WHAM is tailor-made to study ionized gas. The Milky Way contains a thick layer of it, called the Warm Ionized Medium (WIM), which is a distinct and major component of the galactic interstellar medium. The WIM is WHAM's primary target.
[...] "Close to the nucleus of the Milky Way," Krishnarao explained, "gas is ionized by newly forming stars, but as you move further away from the center, things get more extreme, and the gas becomes similar to a class of galaxies called LINERs, or low ionization (nuclear) emission regions."
LINERs are galactic cores identified by their spectral line emissions, which show the presence of weakly ionized or neutral atoms like O, O+, N+, and S+. About one-third of nearby galaxies are LINERs. They're more radiative than galaxies whose only source of energy is star formation, but less radiative than galaxies that have an actively-feeding supermassive black hole.
Now that we know that our very own Milky Way galaxy is a LINER, it means astronomers can now study a LINER up close and personal.
Journal Reference:
D. Krishnarao, R. A. Benjamin, L. M. Haffner. Discovery of diffuse optical emission lines from the inner Galaxy: Evidence for LI(N)ER-like gas [open], Science Advances (DOI: 10.1126/sciadv.aay9711)
(Score: 2) by Kitsune008 on Tuesday July 07 2020, @07:16PM
For sanity's sake! Call Acronym Policy Enforcement on these offenders ASAP!