ANGULAR MOMENTUM-MASS RELATION FOR DARK MATTER HALOS

• Published in: The Astrophysical journal Vol. 809; no. 1; pp. 1 - 15
• Main Authors: Liao, Shihong, Cheng, Dalong, Chu, M.-C., Tang, Jiayu
• Format: Journal Article
• Language: English
• Published: The American Astronomical Society 10.08.2015
• Subjects: Angular momentum; Astronomical models; Cosmology; cosmology: theory; Dark matter; Dynamical systems; Evolution; galaxies: evolution; galaxies: halos; Halos; Merging; methods: numerical
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/809/1/64

ABSTRACT We study the empirical relation between an astronomical object's angular momentum J and mass M, J = βM , the J-M relation, using N-body simulations. In particular, we investigate the time evolution of the J-M relation to study how the initial power spectrum and cosmological model affect this relation and to test two popular models of its origin-mechanical equilibrium and tidal torque theory (TTT). We find that in the ΛCDM model, starts with a value of ∼1.5 at high redshift z, increases monotonically, and finally reaches 5/3 near z = 0, whereas β evolves linearly with time in the beginning, reaches a maximum and decreases, and, finally, stabilizes. A three-regime scheme is proposed to understand this newly observed picture. We show that the TTT accounts for this time-evolution behavior in the linear regime, whereas = 5/3 comes from the virial equilibrium of halos. The J-M relation in the linear regime contains the information of the power spectrum and cosmological model. The J-M relations for halos in different environments and with different merging histories are also investigated to study the effects of a halo's nonlinear evolution. An updated and more complete understanding of the J-M relation is thus obtained.