University of California, Santa Barbara | 2019 Jun 18
Astronomers investigate invisible matter and the workings of the galactic ecosystem
Take a look at any galaxy in the universe through a telescope or in pictures captured by observatories and you might think you have a good idea of its shape.
Think again -- roughly half of a galaxy’s matter is invisible. But scientists have since discovered this missing mass in halos of cool gas surrounding galaxies. Understanding their dynamics, however, has remained an open question.
Now a team of astronomers led by UC Santa Barbara Professor Crystal Martin and graduate student Stephanie Ho has released a paper investigating how these halos interact with the rest of their galaxies. ...
“When you look at galaxies, you see light and that’s what grabs your attention, and you think that’s where the stuff is,” said Martin. “What’s interesting to me is that most of the normal material associated with a galaxy is not luminous at all.”
Astronomers can measure the total mass of a galaxy by looking at the galaxy’s movement and rotation. But this doesn’t separate normal from dark matter. Fortunately, scientists have good measurements of the ratio of these two on the cosmic scale. Around 84% of the universe’s mass is dark matter, and 16% is conventional matter -- made up of protons, electrons, neutrons, and their cousins. With this knowledge, researchers figured out that roughly half of galaxies’ normal matter was nowhere to be seen. ...
Cool Halo Gas Caught Spinning Like Galactic Disks
W.M. Keck Observatory | 2019 Jun 18
Kinematics of Circumgalactic Gas: Feeding Galaxies and Feedback ~ Crystal L. Martin et al
- Astrophysical Journal 878(2):84 (2019 Jun 20) DOI: 10.3847/1538-4357/ab18ac
- arXiv.org > astro-ph > arXiv:1901.09123 > 26 Jan 2019 (v1), 25 Apr 2019 (v3)