Mass of galaxy lenses in modified gravity: Any need for dark mass?

Chiu, Mu Chen; Ko, C. M.; Tian, Yong; Zhao, Hongsheng

doi:10.1103/physrevd.83.063523

Cited by 23 publications

(19 citation statements)

References 47 publications

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“…While such a missing mass is indeed possible, and even corroborated by some dynamical studies [365] of galaxies residing inside clusters (i.e., the small-scale equivalent of the problem of MOND in clusters), for isolated systems with wellconstrained stellar mass-to-light ratio, the use of the simple µ-function (α = 1 in Eq. 46) has on the contrary been shown to yield perfectly acceptable fits [95] in accordance with the lensing fundamental plane [398].…”

Section: Strong Lensing By Galaxiesmentioning

confidence: 99%

Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions

Famaey

McGaugh

2012

Living Rev. Relativ.

887

1,303

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A wealth of astronomical data indicate the presence of mass discrepancies in the Universe. The motions observed in a variety of classes of extragalactic systems exceed what can be explained by the mass visible in stars and gas. Either (i) there is a vast amount of unseen mass in some novel form — dark matter — or (ii) the data indicate a breakdown of our understanding of dynamics on the relevant scales, or (iii) both. Here, we first review a few outstanding challenges for the dark matter interpretation of mass discrepancies in galaxies, purely based on observations and independently of any alternative theoretical framework. We then show that many of these puzzling observations are predicted by one single relation — Milgrom’s law — involving an acceleration constant a0 (or a characteristic surface density Σ† = a0/G) on the order of the square-root of the cosmological constant in natural units. This relation can at present most easily be interpreted as the effect of a single universal force law resulting from a modification of Newtonian dynamics (MOND) on galactic scales. We exhaustively review the current observational successes and problems of this alternative paradigm at all astrophysical scales, and summarize the various theoretical attempts (TeVeS, GEA, BIMOND, and others) made to effectively embed this modification of Newtonian dynamics within a relativistic theory of gravity.

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Section: Strong Lensing By Galaxiesmentioning

confidence: 99%

Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions

Famaey

McGaugh

2012

Living Rev. Relativ.

887

1,303

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“…1) in small galaxies and in the solar system [14]. Additionally, there will be only very mild (< 50%) variations of A 0 inside galaxies, as well as between galaxies, small variations which might be desirable to explain some anomalies in strong lensing galaxies [15][16][17][18][19]. In any case this scatter is acceptable as the MOND formula works for all galaxies as long as a 0 is within the range between 0.9 and 1.7 × 10 −10 m s −2 [13,20].…”

Section: A Realistic Effective Variation Of the Acceleration Scalementioning

confidence: 99%

Unifying all mass discrepancies with one effective gravity law?

Zhao

Famaey

2012

Phys. Rev. D

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A remarkably tight relation is observed between the Newtonian gravity sourced by the baryons and the actual gravity in galaxies of all sizes. This can be interpreted as the effect of a single effective force law depending on acceleration. This is however not the case in larger systems with much deeper potential wells, such as galaxy clusters. Here we explore the possibility of an effective force law reproducing mass discrepancies in all extragalactic systems when depending on both acceleration and the depth of the potential well. We exhibit, at least at a phenomenological level, one such possible construction in the classical gravitational potential theory. Interestingly, the framework, dubbed EMOND, is able to reproduce the observed mass discrepancies in both galaxies and galaxy clusters, and to produce multi-center systems with offsets between the peaks of gravity and the peaks of the baryonic distribution.PACS numbers: 98.10.+z, 98.62.Dm, 95.35.+d, 95.30.Sf

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“…Any theory of modified gravity necessarily needs to comprise the -empirically well established -MOND laws as well as non-dynamical signatures of gravity, notably (i) gravitational lensing and (ii) gravitational waves. Studies assuming TeVeS as the underlying theory of gravity find good agreement with observations of gravitational lensing [89,90,91]. An example for a theory naturally including gravitational waves is provided by massive gravity; as already pointed out by [76], in massive gravity the GR equations of gravitational waves are recovered in the limiting case of vanishing graviton mass.…”

Section: Discussionmentioning

confidence: 54%

The ‘Missing Mass Problem’ in Astronomy and the Need for a Modified Law of Gravity

Trippe

2014

Zeitschrift Für Naturforschung A

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Since the 1930s, astronomical observations have accumulated evidence that our understanding of the dynamics of galaxies and groups of galaxies is grossly incomplete: assuming the validity of Newton's law of gravity on astronomical scales, the observed mass (stored in stars and interstellar gas) of stellar systems can account only for roughly 10% of the dynamical (gravitating) mass required to explain the high velocities of stars in those systems. The standard approach to this "missing mass problem" has been the postulate of "dark matter", meaning an additional, electromagnetically dark, matter component that provides the missing mass. However, direct observational evidence for dark matter has not been found to date. More importantly, astronomical observations obtained during the last decade indicate that dark matter cannot explain the kinematics of galaxies. Multiple observations show that the discrepancy between observed and dynamical mass is a function of gravitational acceleration (or field strength) but not of other parameters (size, rotation speed, etc.) of a galaxy; the mass discrepancy appears below a characteristic and universal acceleration a M = (1.1 ± 0.1) × 10 −10 m s −2 ("Milgrom's constant"). Consequently, the idea of a modified law of gravity, specifically the ansatz of Modified Newtonian Dynamics (MOND), is becoming increasingly important in astrophysics. MOND has successfully predicted various important empirical relations of galaxy dynamics, including the famous Tully-Fisher and Faber-Jackson relations. MOND is found to be consistent with stellar dynamics from binary stars to clusters of galaxies, thus covering stellar systems spanning eight orders of magnitude in size and 14 orders of magnitude in mass. These developments have the potential to initiate a paradigm shift from dark matter to a modified law of gravity as the physical mechanism behind the missing mass problem.

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Mass of galaxy lenses in modified gravity: Any need for dark mass?

Cited by 23 publications

References 47 publications

Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions

Modified Newtonian Dynamics (MOND): Observational Phenomenology and Relativistic Extensions

Unifying all mass discrepancies with one effective gravity law?

The ‘Missing Mass Problem’ in Astronomy and the Need for a Modified Law of Gravity

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