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Angular momentum evolution of galaxies in EAGLE | | Claudia del P. Lagos
; Tom Theuns
; Adam R.H. Stevens
; Luca Cortese
; Nelson D. Padilla
; Timothy A. Davis
; Sergio Contreras
; Darren Croton
; | | Date: |
6 Sep 2016 | | Abstract: | We use EAGLE to study the specific angular momentum of galaxies, j, at z<3.
Our aims are (i) to investigate the physical causes behind the wide range of j
in galaxies at fixed mass at z=0 and (ii) examine whether simple, theoretical
models can explain the seemingly complex and non-linear nature of the evolution
of j in EAGLE. We find that j of the stars, jstars, and baryons, jbar, are
strongly correlated with stellar and baryon mass, respectively, and that the
dispersion of the relation is highly correlated with gas fraction, stellar
concentration, (u-r) colour, stellar age and the ratio of circular velocity to
velocity dispersion. We compare with available observations at z=0 and find
excellent agreement. Our findings suggest that in the case of all baryons and
stars, j follows the theoretical expectation of an isothermal collapsing halo
under conservation of j to within 50%. In rotation-supported galaxies, the
strong dependence of jstars and jbar on the neutral gas fraction is well
described by a model in which the disk angular momentum is just enough to
maintain marginally stable disks. We also identify average tracks for the
evolution of the spin parameter of the stars, lstars =j/M^2/3, (with j measured
within a half-stellar mass radius), depending on whether most of the stars
formed before or after turnaround (z~1.2 for our galaxies). In the absence of
mergers, galaxies older than 9Gyr (i.e. most stars formed before turnaround)
show little evolution in their lstars, while younger ones show a constant
lstars at z>1.2, and then increase as lstars~a. Galaxy mergers reduce lstars by
a factor of 2-3. These tracks are driven by both the evolution of the total
jstars but also its radial distribution. Regardless of the aperture used to
measure j, two distinct channels leading to low jstars in galaxies at z=0 are
identified: (i) galaxy mergers, and (ii) early formation of most of the stars. | | Source: | arXiv, 1609.1739 | | Services: | Forum | Review | PDF | Favorites | |
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