Does Dark Matter Exist, Or Is Gravity Wrong? The Answer Lies Billions Of Years In The Past (Synopsis) [Starts With A Bang]

“Dark matter or invisible element?
You decide.” -Toba Beta

The dark matter wars rage on and on, with both sides — those in favor of modifying gravity and those in favor of adding an additional mass component to the Universe — claiming victories for their own side and defeat for the other. But one piece of evidence, hitherto elusive, might finally hold the key to distinguishing one from the other: early, young, less-evolved galaxies. Billions of years ago, not as much dark matter had fallen into the inner portions of galaxies, meaning that the outer portions of rotating spirals should display less dark matter in the past than they do today.

Do smaller and/or younger galaxies obey a different gravitational or acceleration law than large, old ones? That would go a long way towards discerning between dark matter and modified gravity. Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona.

Instead of flat rotation curves, the galaxies in the distant Universe should exhibit falling rotation curves. In a series of new papers, a team was able to observe 101 distant galaxies at relatively high redshifts, and what they found presented compelling evidence for exactly this phenomenon. As always, more and better data is needed, as it’s only a three-sigma effect so far.

The dark matter models of today (top curves) fail to match the rotation curves, as (black curve) does the no dark matter model. However, models that allow dark matter to evolve with time, as expected, match up remarkably well. Image credit: P. Lang et al., arXiv:1703.05491, submitted to ApJ.

But as the first hint of this long-anticipated effect, it’s a compelling preview of what the telescopes of the 2020s will offer! Come get the scientific story today.

from ScienceBlogs http://ift.tt/2moODpx

“Dark matter or invisible element?
You decide.” -Toba Beta

The dark matter wars rage on and on, with both sides — those in favor of modifying gravity and those in favor of adding an additional mass component to the Universe — claiming victories for their own side and defeat for the other. But one piece of evidence, hitherto elusive, might finally hold the key to distinguishing one from the other: early, young, less-evolved galaxies. Billions of years ago, not as much dark matter had fallen into the inner portions of galaxies, meaning that the outer portions of rotating spirals should display less dark matter in the past than they do today.

Do smaller and/or younger galaxies obey a different gravitational or acceleration law than large, old ones? That would go a long way towards discerning between dark matter and modified gravity. Image credit: Adam Block/Mount Lemmon SkyCenter/University of Arizona.

Instead of flat rotation curves, the galaxies in the distant Universe should exhibit falling rotation curves. In a series of new papers, a team was able to observe 101 distant galaxies at relatively high redshifts, and what they found presented compelling evidence for exactly this phenomenon. As always, more and better data is needed, as it’s only a three-sigma effect so far.

The dark matter models of today (top curves) fail to match the rotation curves, as (black curve) does the no dark matter model. However, models that allow dark matter to evolve with time, as expected, match up remarkably well. Image credit: P. Lang et al., arXiv:1703.05491, submitted to ApJ.

But as the first hint of this long-anticipated effect, it’s a compelling preview of what the telescopes of the 2020s will offer! Come get the scientific story today.

from ScienceBlogs http://ift.tt/2moODpx