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ID: 742674.0, MPI für Astronomie / Publikationen_mpia
Galactic disc profiles and a universal angular momentum distribution from statistical physics
Authors:
Date of Publication (YYYY-MM-DD):2017
Title of Journal:Monthly Notices of the Royal Astronomical Society
Volume:467
Start Page:5022
End Page:5032
Audience:Not Specified
Abstract / Description:We show that the stellar surface brightness profiles in disc galaxies - observed to be approximately exponential - can be explained if radial migration efficiently scrambles the individual stars' angular momenta while conserving the circularity of the orbits and the total mass and angular momentum. In this case, the disc's distribution of specific angular momenta j should be near a maximum entropy state and therefore approximately exponential, dN ∝ \exp (-j/< j\rangle ) dj. This distribution translates to a surface density profile that is generally not an exponential function of radius: Σ (R) ∝ \exp [-R/R_e({R})]/ (R R_e({R}))(1+d{ log v_c (R)}/ d{ log R}), for a rotation curve v(R) and R_e({R})≡ < j\rangle /v_c (R). We show that such a profile matches the observed surface brightness profiles of disc-dominated galaxies just as well as the empirical exponential profile. Disc galaxies that exhibit population gradients cannot have fully reached a maximum-entropy state but appear to be close enough that their surface brightness profiles are well fit by this idealized model.
Free Keywords:methods: analytical; galaxies: kinematics and dynamics; galaxies: spiral; galaxies: structure
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI fÃ¼r Astronomie
Identifiers:ISSN:0035-8711