Angular momentum evolution of galaxies in EAGLE

Abstract

We use the EAGLE cosmological hydrodynamic simulation suite to study the specific angular momentum of galaxies, $j$, with the aims of (i) investigating the physical causes behind the wide range of $j$ at fixed mass and (ii) examining whether simple, theoretical models can explain the seemingly complex and non-linear nature of the evolution of $j$. We find that $j$ of the stars, $j_{\mathrm{stars}}$, and baryons, $j_{\mathrm{bar}}$, are strongly correlated with stellar and baryon mass, respectively, with the scatter being highly correlated with morphological proxies such as gas fraction, stellar concentration, (u-r) intrinsic colour, stellar age and the ratio of circular velocity to velocity dispersion. We compare with available observations at $z=0$ and find excellent agreement. We find that $j_{\mathrm{bar}}$ follows the theoretical expectation of an isothermal collapsing halo under conservation of specific angular momentum to within $\approx 50$%, while the subsample of rotation-supported galaxies are equally well described by a simple model in which the disk angular momentum is just enough to maintain marginally stable disks. We extracted evolutionary tracks of the stellar spin parameter of EAGLE galaxies and found that the fate of their $j_{\mathrm{stars}}$ at $z=0$ depends sensitively on their star formation and merger histories. From these tracks, we identified two distinct physical channels behind low $j_{\mathrm{stars}}$ galaxies at $z=0$: (i) galaxy mergers, and (ii) early star formation quenching. The latter can produce galaxies with low $j_{\mathrm{stars}}$ and early-type morphologies even in the absence of mergers.

22 pages (16 without appendices). Accepted for publication in MNRAS. The only difference with previous version is a shorter abstract (to comply with the 250 words limit in MNRAS)

References in corpus (13)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• The EAGLE simulations of galaxy formation: calibration of subgrid physics and model variations
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• Properties of galaxies reproduced by a hydrodynamic simulation
• The SAURON project -- IX. A kinematic classification for early-type galaxies
• A primer on hierarchical galaxy formation: the semi-analytical approach
• The SAMI Galaxy Survey: instrument specification and target selection
• Four phases of angular-momentum buildup in high-z galaxies: from cosmic-web streams through an extended ring to disc and bulge
• Galactic Angular Momentum in the Illustris Simulation: Feedback and the Hubble Sequence
• The SAMI Galaxy Survey: the link between angular momentum and optical morphology
• Two Conditions for Galaxy Quenching: Compact Centres and Massive Haloes
• Building disc structure and galaxy properties through angular momentum: The DARK SAGE semi-analytic model
• How to get cool in the heat: comparing analytic models of hot, cold, and cooling gas in haloes and galaxies with EAGLE

Cited by in corpus (5)

• The role of mergers and halo spin in shaping galaxy morphology
• The KMOS Redshift One Spectroscopic Survey (KROSS): rotational velocities and angular momentum of z~0.9 galaxies
• How to get cool in the heat: comparing analytic models of hot, cold, and cooling gas in haloes and galaxies with EAGLE
• Galactic angular momentum in cosmological zoom-in simulations. I. Disk and bulge components and the galaxy--halo connection
• The HIX galaxy survey I: Study of the most gas rich galaxies from HIPASS