2017/03/31 by Daniel DeFelippis, Shy Genel, Greg L. Bryan +2 · 60 citations
Physics and Astronomy · #Accretion (finance) #Angular momentum #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Dark matter #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Halo #Specific relative angular momentum #Stars #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aa6dfc
published in The Astrophysical Journal 841(1), 16 (IOP Publishing) · Accepted to ApJ. 13 pages, 10 figures. Key figures are 1, 2, and 3
arxiv created 2017/04/18 · openalex publication_date 2017/05/18 · openalex created_date 2017/05/19 · arxiv updated 2017/05/24 · openalex updated_date 2026/08/06
Abstract Observed galactic disks have specific angular momenta similar to expectations for typical dark matter halos in ΛCDM. Cosmological hydrodynamical simulations have recently reproduced this similarity in large galaxy samples by including strong galactic winds, but the exact mechanism that achieves this is not yet clear. Here we present an analysis of key aspects contributing to this relation: angular momentum selection and evolution of Lagrangian mass elements as they accrete onto dark matter halos, condense into Milky-Way-scale galaxies, and join the z = 0 stellar phase. We contrast this evolution in the Illustris simulation with that in a simulation without galactic winds, where the z = 0 angular momentum is lower. We find that winds induce differences between these simulations in several ways: increasing angular momentum, preventing angular momentum loss, and causing z = 0 stars to sample the accretion-time angular momentum distribution of baryons in a biased way. In both simulations, gas loses on average between accreting onto halos and first accreting onto central galaxies. In Illustris, this is followed by gains in the “galactic wind fountain” and no further net evolution past the final accretion onto the galaxy. Without feedback, further losses of occur in the gas phase inside the galaxies. An additional difference arises from feedback preferentially selecting higher angular momentum gas at accretion by expelling gas that is poorly aligned. These and additional effects of similar magnitude are discussed, suggesting a complex origin of the similarity between the specific angular momenta of galactic disks and typical halos.