scholarly journals Extreme Dark Matter Dominated Dwarfs

2004 ◽  
Vol 220 ◽  
pp. 359-364
Author(s):  
Mark I. Wilkinson ◽  
Jan T. Kleyna ◽  
N. Wyn Evans ◽  
Gerard F. Gilmore
Keyword(s):  
Dark Matter ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Dwarf Spheroidal Galaxies ◽  
Sharp Fall ◽  
Outer Limit ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Central Regions ◽  
Ursa Minor

The results of a large radial velocity survey of the Draco and Ursa Minor dwarf spheroidal galaxies are presented. the velocity dispersion profiles of both objects are very similar: initially the dispersion increases with radius, while at radii approaching the outer limit of the stellar distribution we observe a sharp fall-off. We present the results of mass modeling based on these new data – the mass to light ratios are found to be about 400M⊙/L⊙. Evidence is also presented that the dark matter in the central regions of UMi has a core-like distribution. Finally, we demonstrate that the inner regions of UMi have not been affected by tides and discuss the implications of our data for MOdified Newtonian Dynamics (MOND).

scholarly journals The Search for Dark Matter in Draco and Ursa Minor: A Three Year Progress Report

1987 ◽  
Vol 117 ◽  
pp. 153-160 ◽  
Author(s):  
M. Aaronson ◽  
E. Olszewski
Keyword(s):  
Dark Matter ◽  
Velocity Dispersion ◽  
Progress Report ◽  
Radial Velocities ◽  
Circumstantial Evidence ◽  
Dwarf Spheroidal Galaxies ◽  
Ursa Minor ◽  
Stellar Velocity ◽  
Atmospheric Motions ◽  
Matter Component

We report the cumulative results of an on-going effort to measure the stellar velocity dispersion in two nearby dwarf spheroidal galaxies. Radial velocities having an accuracy ≲ 2 km s−1 have now been secured for ten stars in Ursa Minor and eleven stars in Draco (including 16 K giants and 5 C types). Most objects have been observed at two or more epochs. Stars having non-variable velocities yield in both dwarfs a large (∼ 10 km s−1) dispersion. These results cannot be explained by atmospheric motions, and circumstantial evidence suggests that the effects of undetected binaries are also not likely to be important. Instead, it seems that both spheroidals contain a substantial dark matter component, which therefore must be “cold” in form.

scholarly journals Evidence for Light-weight Local Group Dwarf Spheroidal Galaxies

2004 ◽  
Vol 220 ◽  
pp. 365-366
Author(s):  
J. R. Kuhn ◽  
D. Kocevski
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Local Group ◽  
Light Weight ◽  
Natural Explanation ◽  
Dwarf Spheroidal Galaxies ◽  
Ursa Minor ◽  
Matter Component ◽  
Morphological State ◽  
Spheroidal Galaxies

A simple and natural explanation for the dynamics and morphology of the Local Group Dwarf Spheroidal galaxies, Draco (Dra) and Ursa Minor (UMi), is that they are weakly unbound stellar systems with no significant dark matter component. A gentle, but persistent, Milky Way (MW) tide has left them in their current kinematic and morphological state (the “parametric tidal excitation”). A new test of a dark matter dominated dS potential follows from a careful observation of the “clumpiness” of the dS stellar surface density.

scholarly journals Too big to fail in light of Gaia

2019 ◽  
Vol 490 (1) ◽  
pp. 231-242 ◽  
Author(s):  
Manoj Kaplinghat ◽  
Mauro Valli ◽  
Hai-Bo Yu
Keyword(s):  
Dark Matter ◽  
Milky Way ◽  
Large Scatter ◽  
Too Big To Fail ◽  
Dwarf Spheroidal Galaxies ◽  
Ursa Minor ◽  
Spheroidal Galaxies

ABSTRACT We point out an anticorrelation between the central dark matter (DM) densities of the bright Milky Way dwarf spheroidal galaxies (dSphs) and their orbital pericenter distances inferred from Gaia data. The dSphs that have not come close to the Milky Way centre (like Fornax, Carina and Sextans) are less dense in DM than those that have come closer (like Draco and Ursa Minor). The same anticorrelation cannot be inferred for the ultrafaint dSphs due to large scatter, while a trend that dSphs with more extended stellar distributions tend to have lower DM densities emerges with ultrafaints. We discuss how these inferences constrain proposed solutions to the Milky Way’s too-big-to-fail problem and provide new clues to decipher the nature of DM.

scholarly journals Necessity of Dark Matter in Modified Newtonian Dynamics within Galactic Scales

2008 ◽  
Vol 100 (3) ◽  
Author(s):  
Ignacio Ferreras ◽  
Mairi Sakellariadou ◽  
Muhammad Furqaan Yusaf
Keyword(s):  
Dark Matter ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics

scholarly journals Alternatives to Dark Matter (?)

2004 ◽  
Vol 220 ◽  
pp. 17-26 ◽  
Author(s):  
Anthony Aguirre
Keyword(s):  
General Relativity ◽  
Dark Matter ◽  
General Idea ◽  
Galactic Dynamics ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Visible Matter

It has long been known that Newtonian dynamics applied to the visible matter in galaxies and clusters does not correctly describe the dynamics of those systems. While this is generally taken as evidence for dark matter it is in principle possible that instead Newtonian dynamics (and with it General Relativity) breaks down in these systems. Indeed there have been a number of proposals as to how standard gravitational dynamics might be modified so as to correctly explain galactic dynamics without dark matter. I will review this general idea (but focus on “MOdified Newtonian Dynamics”, or “MOND”), and discuss a number of ways alternatives to dark matter can be tested and, in many cases, ruled out.

scholarly journals The Modified Newtonian Dynamics as an Alternative to Hidden Matter

1987 ◽  
Vol 117 ◽  
pp. 319-333
Author(s):  
Mordehai Milgrom ◽  
Jacob Bekenstein
Keyword(s):  
Dark Matter ◽  
Main Body ◽  
Modified Newtonian Dynamics ◽  
Newtonian Dynamics ◽  
Nonrelativistic Theory ◽  
The Masses ◽  
Modified Dynamics

The mass discrepancy, which has led to the notion of dark matter may, in fact, be due to a breakdown of the Newtonian laws which are used to determine the masses of galactic systems. We describe a nonrelativistic theory which departs from Newton's in the limit of small accelerations. When one uses the modified dynamics to deduce gravitational masses, the need to invoke large quantities of dark matter disappears. We outline the theory and give criteria for deciding which systems are expected to exhibit marked departures from Newtonian behaviour. The main body of the talk is a succinct description of the major predictions of the theory regarding dynamics within galaxies.

Sign in / Sign up

Export Citation Format

Share Document