By University of St. Andrews
May 24, 2022
The brand-new research study recommends that the blue ellipse for a really low disposition might really be proper– hence conserving the MOND theory– if the galaxy is fundamentally somewhat non-circular. General Relativity requires dark matter to hold galaxies together, while MOND does not require dark matter.
Due to the fact that dark matter has actually never ever been identified in spite of years of very delicate searches, numerous theories have actually been put forward to additionally explain what holds galaxies together. The brand-new research study explored this important issue using detailed MOND simulations of a disc galaxy similar to AGC 114905 made at the University of Bonn by Srikanth Nagesh and prompted by Pavel Kroupa, Professor at the University of Bonn and Charles University in Prague. A comparable process causes the spiral arms in disc galaxies, functions which are so common that these are often called spiral galaxies.
Radio image of the neutral hydrogen gas in the galaxy AGC 114905. The new study recommends that the blue ellipse for an extremely low disposition could really be right– therefore saving the MOND theory– if the galaxy is fundamentally rather non-circular. The authors reveal that this is possible using a devoted MOND simulation.
A global group of astronomers, led by a physicist at the University of St Andrews, has revived an alternative gravity theory.
Headed by Dr. Indranil Banik of the School of Physics and Astronomy at the University of St Andrews, the research revealed a high predicted rotation speed of gas in a dwarf galaxy constant with the formerly unmasked theory known as Milgromian Dynamics (MOND).
An earlier study of the rotation speed of gas in the dwarf galaxy AGC 114905 (Mancera Pina et al, 2022) discovered that the gas turned extremely slowly and for that reason claimed the MOND theory was dead.
Such theories are necessary in comprehending our universe since, according to recognized physics, galaxies turn so quickly they ought to fly apart. MOND is a controversial option to General Relativity, the prevailing Einstein-inspired understanding of the phenomenon of gravity. General Relativity requires dark matter to hold galaxies together, while MOND does not require dark matter.
Because dark matter has never ever been found regardless of decades of extremely sensitive searches, numerous theories have been put forward to alternatively discuss what holds galaxies together. Debate raves over which theory is. The extremely low rotation speed reported in the Mancera Pina et al research study is inconsistent with forecasts in a universe governed by General Relativity with large amounts of dark matter.
Dr. Baniks group argues that the high forecasted rotation speed in the MOND gravity theory is consistent with observations if the disposition of the galaxy is overestimated.
The rotation of stars and gas in distant galaxies can not be measured straight. If the galaxy is seen nearly face-on, then it would primarily rotate within the aircraft of the sky.
The brand-new research study explored this crucial concern utilizing comprehensive MOND simulations of a disc galaxy similar to AGC 114905 made at the University of Bonn by Srikanth Nagesh and initiated by Pavel Kroupa, Professor at the University of Bonn and Charles University in Prague. When viewed face-on, the simulations reveal that it can appear rather elliptical even. Since stars and gas in the galaxy have gravity and can pull themselves into a rather non-circular shape, this is. A similar process causes the spiral arms in disc galaxies, features which are so common that these are often called spiral nebula.
As an outcome, the galaxy might be a lot closer to face-on than the observers thought. This might suggest the galaxy is turning much faster than reported, removing the stress with MOND.
Dr. Banik, lead author on the brand-new research study, said: “Our simulations show that the disposition of AGC 114905 might be significantly less than reported, which would indicate the galaxy is really turning much faster than individuals think, in line with MOND expectations.”.
Dr. Hongsheng Zhao, of the School of Physics and Astronomy at the University of St Andrews, said: “The extremely low reported rotation speed of this galaxy is inconsistent with both MOND and the standard approach with dark matter. Just MOND is able to get around this obvious contradiction.”.
The brand-new study also argues that a comparable fake inclination impact is not likely to occur in the standard dark matter technique because the galaxy is dominated by the smooth dark matter halo. The stars and gas contribute little to the gravity, so the disc is not self-gravitating.
This means it is likely to look extremely circular if seen face-on, as validated by simulations performed by another group (Sellwood & & Sanders, 2022). As an outcome, the observed ellipticity needs to be because of a substantial disposition between the disc and sky planes. The rotation speed would then be extremely small, implying that the galaxy has very little dark matter. It is not possible in this structure that an isolated dwarf galaxy would have such a percentage of dark matter offered just how much mass it has in stars and gas.
Pavel Kroupa, Professor at the University of Bonn and Charles University in Prague, stated of the more comprehensive context of these results: “While MOND works well in the tests performed so far, the standard approach causes really extreme issues on all scales ranging from dwarf galaxies like AGC 114905 all the way up to cosmological scales, as found by many independent groups.”.
Reference: “Overestimated inclinations of Milgromian disc galaxies: the case of the ultradiffuse galaxy AGC 114905” by Indranil Banik, Srikanth T Nagesh, Hosein Haghi, Pavel Kroupa and Hongsheng Zhao, 19 April 2022, Monthly Notices of the Royal Astronomical Society.DOI: 10.1093/ mnras/stac1073.