Astrophysics (Index)About

dark matter halo

(dark halo, halo)
(hypothetical dark matter throughout and surrounding a galaxy)

A dark matter halo is the dark matter portion of a galaxy which extends throughout the visible galaxy and further out, thus as a halo. Dark matter explains apparent additional gravity of a galaxy, galaxy cluster, or other large structures beyond that explained by the visible and inferred stars, interstellar media and other normal matter. The velocity distribution of orbiting stars depends upon the amount of gravity (and thus mass), and can be determined from Doppler shifts of the starlight, revealing the mass of the galaxy, including any not evident from the number and mass of its stars.

The typical inferred halo is spherical, densest in the center and about 5 times more massive than the visible portion of the galaxy. The halo of a substantial galaxy such as the Milky Way includes satellite galaxies and globular clusters, which are presumed to form around volumes of extra dark-matter density, termed subhalos (sub-halos). Lambda-CDM model predicts more subhalos than known evidence confirms, so any new evidence of additional subhalos (e.g., tidal effects on stellar streams) is of interest.

Dark matter halos are presumed to exist before the galaxies, i.e., galaxies form where the gravity of dark matter halos has gathered gas. The term minihalo refers to a small halo, and it is presumed that in the early universe, they were usual before gravity caused halos to combine into larger halos. Models of Population III star formation often take into account the possibility of such minihalos.


Dark matter halo can also refer to a region of dark matter throughout a galaxy cluster, presumably somewhat less dense than regions around the individual galaxies. The term cluster dark matter halo is sometimes used to distinguish this usage.


(physics,galaxies,gravity,dark matter)
Further reading:
https://en.wikipedia.org/wiki/Dark_matter_halo
https://astronomy.swin.edu.au/cosmos/D/dark+halo
https://web2.ph.utexas.edu/~coker2/index.files/darkmatter.html
https://chandra.as.utexas.edu/dm-halo-pic.html
https://ui.adsabs.harvard.edu/abs/2018ARA%26A..56..435W/abstract
https://ui.adsabs.harvard.edu/abs/2019A%26A...621A..56P/abstract

Referenced by pages:
brightest cluster galaxy (BCG)
cluster radius
conditional luminosity function (CLF)
conditional stellar mass function (CSMF)
core-cusp problem
dark galaxy
dark matter (DM)
dark matter detector
dark matter filament
dwarf galaxy problem
galactic disk
galactic halo
galaxy
galaxy formation
gravitational instability model
halo abundance matching (HAM)
halo mass function (HMF)
halo model
HI gas mass
LasDamas
MACHO
Navarro-Frenk-White profile (NFW profile)
POINT-AGAPE
Press-Schechter formalism
RHAPSODY
semi-analytic model (SAM)
Spitzer HETDEX Exploratory Large Area Survey (SHELA)
structure formation

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