Modified Newtonian dynamics and the Coma cluster

The, Lih Sin; White, Simon D. M.

doi:10.1086/114760

Cited by 40 publications

(18 citation statements)

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“…It has been known from the early 1990s that MOND, in its minimalist and purist form (which assumes, e.g., a universal value of a 0 ), does not completely remove the mass discrepancies in galaxy clusters (e.g., The & White 1988;Gerbal & al. 1992;Sanders 1994;Sanders 1999;Sanders 2003;Pointecouteau & Silk 2005;Takahashi & Chiba 2007;Angus, Famaey, & Buote 2008).…”

Section: Introductionmentioning

confidence: 99%

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

Milgrom

2015

Mon. Not. R. Astron. Soc.

104

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MOND reduces greatly the mass discrepancy in clusters of galaxies, but does leave a global discrepancy of about a factor of 2 (epitomized by the structure of the Bullet Cluster). It has been proposed, within the minimalist and purist MOND, that clusters harbor some indigenous, yet undetected, cluster baryonic (dark) matter (CBDM), whose total amount is comparable with that of the observed hot gas. Koda et al. have recently identified more than a thousand ultra-diffuse, galaxy-like objects (UDGs) in the Coma cluster. These, they argue, require, within Newtonian dynamics, that they are much more massive than their observed stellar component. Here, I propound that some of the CBDM is internal to UDGs, which endows them with robustness. The rest of the CBDM objects formed in now-disrupted kin of the UDGs, and is dispersed in the intracluster medium. The discovery of cluster UDGs is not in itself a resolution of the MOND cluster conundrum, but it lends greater plausibility to CBDM as its resolution. Alternatively, if the UDGs are only now falling into Coma, their large size and very low surface brightness could result from the inflation due to the MOND, variable externalfield effect (EFE). I also consider briefly solutions to the conundrum that invoke more elaborate extensions of purist MOND, e.g., that in clusters, the MOND constant takes up larger than canonical values of the MOND constant. Whatever solves the cluster conundrum within MOND might also naturally account for UDGs. Subject headings:

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Section: Introductionmentioning

confidence: 99%

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

Milgrom

2015

Mon. Not. R. Astron. Soc.

104

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“…MOND does not fully account for the mass discrepancies in galaxy cluster and rich galaxy groups that contain large quantities of x-ray emitting, hot gas. This was first pointed out in relation to the Coma cluster in The & White, 1988, and then shown to apply to other clusters and rich groups in several publications.…”

Section: Galaxy Clustersmentioning

confidence: 85%

MOND vs. dark matter in light of historical parallels

Milgrom

2020

Studies in History and Philosophy of Science Part B: Studies in

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MOND is a paradigm that contends to account for the mass discrepancies in the Universe without invoking 'dark' components, such as 'dark matter' and 'dark energy'. It does so by supplanting Newtonian dynamics and General Relativity, departing from them at very low accelerations. Having in mind readers who are historians and philosophers of science, as well as physicists and astronomers, I describe in this review the main aspects of MOND -its statement, its basic tenets, its main predictions, and the tests of these predictions -contrasting it with the dark-matter paradigm. I then discuss possible wider ramifications of MOND, for example the potential significance of the MOND constant, a0, with possible implications for the roots of MOND in cosmology. Along the way I point to parallels with several historical instances of nascent paradigms. In particular, with the emergence of the Copernican world picture, that of quantum physics, and that of relativity, as regards their initial advent, their development, their schematic structure, and their ramifications. For example, the interplay between theories and their corollary laws, and the centrality of a new constant with converging values as deduced from seemingly unrelated manifestations of these laws. I demonstrate how MOND has already unearthed a number of unsuspected laws of galactic dynamics (to which, indeed, a0 is central) predicting them a priori, and leading to their subsequent verification. I parallel the struggle of the new with the old paradigms, and the appearance of hybrid paradigms at such times of struggle. I also try to identify in the history of those established paradigms a stage that can be likened to that of MOND today.

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“…Studies based on gas dynamics and on lensing have helped determine the remaining discrepancy, e.g. by The and White (1988), Gerbal et al (1992), Sanders (1994Sanders ( ,1999Sanders ( ,2003, Aguirre et al (2001), Pointecouteau and Silk (2005), Angus et al (2007b), and by Takahashi and Chiba 2007. In the framework of MOND we have to attribute the remaining discrepancy to yet undetected matter. It is likely that this matter is baryonic in some form-and so I shall assume in this paper-although other possibilities have been raised, e.g., massive neutrinos (Sanders 2003(Sanders , 2007.…”

Section: Cluster Dark Matter In Light Of Mondmentioning

confidence: 99%

Marriage à-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle

Milgrom¹

2008

New Astronomy Reviews

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I start with a brief introduction to MOND phenomenology and its possible roots in cosmology-a notion that may turn out to be the most far reaching aspect of MOND. Next I discuss the implications of MOND for the dark matter (DM) doctrine: MOND's successes imply that baryons determine everything. For DM this would mean that the puny tail of leftover baryons in galaxies wags the hefty DM dog. This has to occur in many intricate ways, and despite the haphazard construction history of galaxies-a very tall order. I then concentrate on galaxy clusters in light of MOND, which still requires some yet undetected cluster dark matter, presumably in some baryonic form (CBDM). This CBDM might contribute to the heating of the x-ray emitting gas and thus alleviate the cooling-flow puzzle. MOND, qua theory of dynamics, does not directly enter the microphysics of the gas; however, it does force a new outlook on the role of DM in shaping the cluster gasdynamics: MOND tells us that the cluster DM is not cold dark matter, is not so abundant, and is not expected in galaxies; it is thus not subject to constraints on baryonic DM in galaxies. The mass in CBDM required in a whole cluster is, typically, similar to that in hot gas, but is rather more centrally concentrated, totally dominating the core. The CBDM contribution to the baryon budget in the universe is thus small. Its properties, deduced for isolated clusters, are consistent with the observations of the "bullet cluster". Its kinetic-energy reservoir is much larger than that of the hot gas in the core, and would suffice to keep the gas hot for many cooling times. Heating can be effected in various ways depending on the exact nature of the CBDM, from very massive black holes to cool, compact gas clouds.

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Modified Newtonian dynamics and the Coma cluster

Cited by 40 publications

References 0 publications

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

MOND vs. dark matter in light of historical parallels

Marriage à-la-MOND: Baryonic dark matter in galaxy clusters and the cooling flow puzzle

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