MPE: Distant Galaxies Are Dominated by Gas & Stars

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MPE: Distant Galaxies Are Dominated by Gas & Stars

Post by bystander » Fri Mar 17, 2017 3:53 pm

Distant Galaxies Are Dominated by Gas and Stars -- Where Is the Dark Matter?
Max Planck Institute for Extraterrestrial Physics | 2017 Mar 15
[img3="Observations of the six galaxies with KMOS and SINFONI. For each galaxy, the left column shows the distribution of the total surface brightness in the Hα line. The right column gives the velocity map. All galaxies show a clear rotation pattern, with blue areas moving towards the observer and red parts away from the observer. (Credit: MPE)"] ... 540642.jpg[/img3][hr][/hr]
New observations of rotating galaxies at the peak epoch of galaxy formation, 10 billion years ago, surprisingly show that these massive, star-forming galaxies are completely dominated by baryonic or “normal” mass with dark matter playing a much smaller role in comparable regions of their outer disks than in the local universe. The international group of researchers led by the Max Planck Institute for Extraterrestrial Physics mapped the rotation curves of six galaxies to distances of ~65,000 light years from their centres and found that their rotation velocities are not constant but drop with radius. These findings are supported by observations of more than 200 further galaxies, where different estimates of their dynamical state also indicate a high baryonic mass fraction. In addition, the analysis shows that these early galaxies had a much thicker disk with turbulent motion accounting for part of the dynamical support. These findings are published in a paper in the journal Nature as well as three accompanying papers in the Astrophysical Journal.

Over the past few decades, many different studies of galaxies in the local universe have shown the existence and importance of so-called “dark matter”. While normal, or “baryonic”, matter can be seen as brightly shining stars or luminous gas and dust, dark matter interacts with normal matter only through gravity. In particular it is responsible for flat rotation curves in spiral galaxies, i.e. rotation velocities that are constant or increasing with radius. ...

Dark Matter Less Influential in Galaxies in Early Universe
ESO Science Release | VLT | 2017 Mar 15

VLT observations of distant galaxies suggest they were dominated by normal matter

New observations indicate that massive, star-forming galaxies during the peak epoch of galaxy formation, 10 billion years ago, were dominated by baryonic or “normal” matter. This is in stark contrast to present-day galaxies, where the effects of mysterious dark matter seem to be much greater. This surprising result was obtained using ESO’s Very Large Telescope and suggests that dark matter was less influential in the early Universe than it is today. ...

Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago - R. Genzel et al Falling outer rotation curves of star-forming galaxies at 0.6 < z < 2.6
probed with KMOS3D and SINS/ZC-SINF
- P. Lang et al The evolution of the Tully-Fisher relation between z∼2.3 and z∼0.9 with KMOS3D - H. Übler et al KMOS3D: Dynamical constraints on the mass budget in early star-forming disks - S. Wuyts et al
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