Hitting the Bull's-eye: The Radial Profile of Accretion and Star Formation in the Milky Way

Abstract

Ongoing star formation in the Milky Way requires continuous gaseous fuel from accretion. Previous work has suggested that the accretion of dwarf galaxies could provide the needed gas for this process. In this work we investigate whether dwarf galaxy accretion is consistent with the radial profile of star formation observed in the Milky Way, which is strongly concentrated toward the center of the gaseous disk of the Galaxy. Using realistic parameters for the Galactic potential, gaseous halo, Galactic disk, velocities of dwarf galaxies, and effects of drag on stripped gas in the halo, we model the distribution of radii at which dwarf galaxies accrete onto the Galactic disk. We also model the radial distribution of the accretion of gas that cools directly out of the halo by examining the results of recent simulations. We show that dwarf galaxies cannot reproduce the concentration of accretion toward the center of the Galaxy required by star formation. We also show that clouds that cool directly from the halo can reproduce this central concentration, and conclude that this difference is largely due to the discrepancy in absolute specific angular momentum between the two mechanisms.

9 pages, 5 figures, accepted to the ApJ

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• The EAGLE simulations: atomic hydrogen associated with galaxies
• Can Gas prevent the Destruction of Thin Stellar Discs by Minor Mergers?
• Radial gas motions in The HI Nearby Galaxy Survey (THINGS)
• Estimating gas accretion in disc galaxies using the Kennicutt-Schmidt law
• An HI Survey of Six Local Group Analogs. II. HI properties of group galaxies
• The Metal-Enriched Outer Disk of NGC 2915
• Thermal instabilities in cooling galactic coronae: fuelling star formation in galactic discs
• Gas Accretion onto the Milky Way
• Extraplanar H II Regions in Spiral Galaxies. I. Low-Metallicity Gas Accreting through the Disk-Halo Interface of NGC 4013
• Extraplanar H II Regions in Spiral Galaxies. II. In Situ Star Formation in the Interstellar Thick Disk of NGC 4013
• Large-scale latitude distortions of the inner Milky Way Disk from the Herschel/Hi-GAL Survey
• Stellar Migration and Chemical Enrichment in the Milky Way Disc: A Hybrid Model
• The multi-zone chemical evolution of the Galactic bulge: predicting abundances for different radial zones
• Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk