Skip to main content

Dark matter versus modified gravity



The scenario consistent with a wealth of observations for the missing mass problem is that of weakly interacting dark matter particles. However, arguments or proposals for a Newtonian or relativistic modified gravity scenario continue to be made.


A distinguishing characteristic between the two scenarios is that dark matter particles can produce a gravitational effect, in principle, without the need of baryons while this is not the case for the modified gravity scenario where such an effect must be correlated with the amount of baryonic matter.

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster MACSJ0717.5+3745, one of the most massive galaxy clusters known and also the largest known gravitational lens. Credit: NASA, ESA and the HST Frontier Fields team (STScI)
In a recent paper (Lin & Ishak 2016) the authors consider ultra-faint dwarf (UFD) galaxies as a promising arena to test the two scenarios based on the above assertion. They compare the correlation of the luminosity with the velocity dispersion between samples of UFD and non-UFD galaxies, finding a trend of loss of correlation for the UFD galaxies.

For example, they find for 28 non-UFD galaxies a strong correlation coefficient of -0.688 which drops to -0.077 for the 23 UFD galaxies. Incoming and future data will determine whether the observed stochasticity for UFD galaxies is physical or due to systematics in the data.

Such a loss of correlation (if it is to persist) is possible and consistent with the dark matter scenario for UFD galaxies but would constitute a new challenge for the modified gravity scenario.

  • Lin & Ishak 2016 (preprint) - Ultra faint dwarf galaxies: an arena for testing dark matter versus modified gravity (arXiv)
Etichette:

Comments

Post a Comment

Popular posts from this blog

CONSTRAINTS ON THE LOCATION OF A POSSIBLE 9TH PLANET

Image: The six most distant known objects in the solar system with orbits exclusively beyond Neptune (magenta) all mysteriously line up in a single direction. Such an orbital alignment can only be maintained by some outside force, Batygin and Brown say. Their paper argues that a planet with 10 times the mass of the earth in a distant eccentric orbit anti-aligned with the other six objects (orange) is required to maintain this configuration. Credit: Caltech The astronomers have noticed some of the dwarf planets and other small, icy objects tend to follow orbits that cluster together. To explain the unusual distribution of these Kuiper Belt objects, several authors have advocated the existence of a superEarth planet in the outer solar system ( planet Nine or planet X ).
1 comment
Read more

ORBITAL PERIODS OF THE PLANETS

For orbital period generally we refer to the sidereal period, that is the temporal cycle that it takes an object to make a full orbit, relative to the stars. This is the orbital period in an inertial (non-rotating) frame of reference (365,25 days for the earth).
Post a Comment
Read more

Importance of Supernovae in the Enrichment of Planetary Systems

Figure: Called the Veil Nebula, the debris is one of the best-known supernova remnants, deriving its name from its delicate, draped filamentary structures. This view is a mosaic of six Hubble pictures of a small area roughly two light-years across, covering only a tiny fraction of the nebula’s vast structure. Credit: NASA/ESA/Hubble Heritage Team The presence and abundance of short lived radioisotopes in chondritic meteorites implies that the Sun formed in the vicinity of one or more massive stars that exploded as supernovae (SNe).
Post a Comment
Read more