Journal Article

Radial flows and angular momentum conservation in Galactic chemical evolution

Thomas Bilitewski and Ralph Schönrich

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 3, pages 2266-2282
Published in print November 2012 | ISSN: 0035-8711
Published online November 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21827.x
Radial flows and angular momentum conservation in Galactic chemical evolution

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We study the effects of radial flows on Galactic chemical evolution. A simple analytic scheme is developed prescribing the coupling of infall from the intergalactic medium and radial flows within the disc based on angular momentum conservation. We show that model parameters are tightly constrained by the observed [Fe/H]-abundance gradient in the Galactic disc. By this comparison the average rotational velocity of the onfalling material can be constrained to 0.7 ≤ v/Vc ≤ 0.75, or respectively ∼160 km s−1 when assuming a constant disc circular velocity of Vc = 220 km s−1. We test the robustness of this value against the influence of other processes. For a very simple model of inside-out formation this value changes only by Δv/Vc ∼ 0.1, i.e. ∼20 km s−1, and significantly less on more realistic scenarios, showing that inside-out formation does not alone explain the abundance gradient. Effects of other uncertain parameters, e.g. star formation history and star formation efficiency, have very small impact.

Other drivers of inflow beyond our explicit modelling are assessed by adding a fixed inflow across the whole disc. The churning amplitude only mildly affects the results mostly by slightly flattening the metallicity gradient in the inner disc. A new process causing radial gas flows due to the ejection of material by stars moving on non-circular orbits is studied and seems to contribute negligibly to the total flows.

We further show that gaseous outer discs cannot be the main source feeding the persistent star formation in the inner regions by a direct inflow.

Keywords: Galaxy: abundances; Galaxy: evolution; intergalactic medium; galaxies: ISM; galaxies: kinematics and dynamics

Journal Article.  12911 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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