NASA | MSFC | SAO | Chandra X-ray Observatory | 2019 Jun 03
dark matter packed into its core than expected after being isolated for billions of years, as reported in our press release. The image on the right shows the galaxy called Markarian 1216 (abbreviated as Mrk 1216) in visible light from NASA's Hubble Space Telescope over the same field of view.
Mrk 1216 belongs to a family of elliptically shaped galaxies that are more densely packed with stars in their centers than most other galaxies. Astronomers think they have descended from red, compact galaxies called "red nuggets" that formed about a billion years after the Big Bang, but then stalled in their growth about 10 billion years ago.
If this evolution is correct, then the dark matter in Mrk 1216 and its galactic cousins should also be tightly packed. To test this idea for the first time, a pair of astronomers studied the X-ray brightness and temperature of hot gas at different distances from Mrk 1216's center, so they could "weigh" how much dark matter exists in the middle of the galaxy. The brighter colors at the center of the Chandra image represent the increased density of hot gas in the galaxy's core.
According to the new study, a halo, or fuzzy sphere, of dark matter formed around the stars in the center of Mrk 1216 about 3 or 4 billion years after the Big Bang. The formation of such a red nugget was typical for a wide range of elliptical galaxies seen today. However, unlike Mrk 1216, most giant elliptical galaxies continued to gradually grow in size when smaller galaxies merged with them over cosmic time. ...
The Extremely High Dark Matter Halo Concentration of the Relic
Compact Elliptical Galaxy Mrk 1216 ~ David A. Buote, Aaron J. Barth
- Astrophysical Journal 877(1):91 (2019 Jun 01) DOI: 10.3847/1538-4357/ab1008
- arXiv.org > astro-ph > arXiv:1902.02938 > 08 Feb 2019 (v1), 15 Mar 2019 (v3)