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The shapes of the rotation curves of star-forming galaxies over the last ≈10 Gyr

Lookup NU author(s): Dr Christopher HarrisonORCiD



This is the final published version of an article that has been published in its final definitive form by Oxford University Press, 2019.

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© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.We analyse maps of the spatially resolved nebular emission of ≈1500 star-forming galaxies at z ≈ 0.6-2.2 from deep K-band Multi-Object Spectrograph and MUSE observations to measure the average shape of their rotation curves. We use these to test claims for declining rotation curves at large radii in galaxies at z ≈ 1-2 that have been interpreted as evidence for an absence of dark matter. We show that the shape of the average rotation curves, and the extent to which they decline beyond their peak velocities, depends upon the normalization prescription used to construct the average curve. Normalizing in size by the galaxy stellar disc-scale length after accounting for seeing effects (Rd′), we construct stacked position-velocity diagrams that trace the average galaxy rotation curve out to 6Rd′ (≈13 kpc, on average). Combining these curves with average H i rotation curves for local systems, we investigate how the shapes of galaxy rotation curves evolve over ≈10 Gyr. The average rotation curve for galaxies binned in stellar mass, stellar surface mass density and/or redshift is approximately flat, or continues to rise, out to at least 6Rd′. We find a trend between the outer slopes of galaxies' rotation curves and their stellar mass surface densities, with the higher surface density systems exhibiting flatter rotation curves. Drawing comparisons with hydrodynamical simulations, we show that the average shapes of the rotation curves for our sample of massive, star-forming galaxies at z ≈ 0-2.2 are consistent with those expected from lambda cold dark matter theory and imply dark matter fractions within 6Rd of at least ≈60 per cent.

Publication metadata

Author(s): Tiley AL, Swinbank AM, Harrison CM, Smail I, Turner OJ, Schaller M, Stott JP, Sobral D, Theuns T, Sharples RM, Gillman S, Bower RG, Bunker AJ, Best P, Richard J, Bacon R, Bureau M, Cirasuolo M, Magdis G

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2019

Volume: 485

Issue: 1

Pages: 834-860

Print publication date: 01/05/2019

Online publication date: 13/02/2019

Acceptance date: 05/02/2019

Date deposited: 04/02/2020

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press


DOI: 10.1093/mnras/stz428


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