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KURVS: the outer rotation curve shapes and dark matter fractions of z ∼ 1.5 star-forming galaxies

Puglisi, Annagrazia; Dudzevičiūtė, Ugnė; Swinbank, Mark; Gillman, Steven; Tiley, Alfred L; Bower, Richard G; Cirasuolo, Michele; Cortese, Luca; Glazebrook, Karl; Harrison, Chris; Ibar, Edo; Molina, Juan; Obreschkow, Danail; Oman, Kyle A; Schaller, Matthieu; Shankar, Francesco; Sharples, Ray M

KURVS: the outer rotation curve shapes and dark matter fractions of z ∼ 1.5 star-forming galaxies Thumbnail


Steven Gillman

Alfred L Tiley

Richard G Bower

Michele Cirasuolo

Luca Cortese

Karl Glazebrook

Chris Harrison

Edo Ibar

Juan Molina

Danail Obreschkow

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Dr Kyle Oman
Associate Professor - Royal Society Dorothy Hodgkin Fellow

Francesco Shankar


We present first results from the KMOS Ultra-deep Rotation Velocity Survey (KURVS), aimed at studying the outer rotation curves shape and dark matter content of 22 star-forming galaxies at z ∼1.5. These galaxies represent ’typical’ star-forming discs at z ∼1.5, being located within the star-forming main sequence and stellar mass-size relation with stellar masses 9.5 ≤ log(M★/M⊙) ≤ 11.5. We use the spatially resolved Hα emission to extract individual rotation curves out to 4 times the effective radius, on average, or ∼10-15 kpc. Most rotation curves are flat or rising between three and six disc scale radii. Only three objects with dispersion-dominated dynamics (vrot/σ0 ∼0.2) have declining outer rotation curves at more than 5σ significance. After accounting for seeing and pressure support, the nine rotation-dominated discs with vrot/σ0 ≥ 1.5 have average dark matter fractions of 50±20 per cent at the effective radius, similar to local discs. Together with previous observations of star-forming galaxies at cosmic noon, our measurements suggest a trend of declining dark matter fraction with increasing stellar mass and stellar mass surface density at the effective radius. Measurements of simulated EAGLE galaxies are in quantitative agreement with observations up to log(M★ Reff-2 /M⊙ kpc-2) ∼9.2, and overpredict the dark matter fraction of galaxies with higher mass surface densities by a factor of ∼3. We conclude that the dynamics of typical rotationally-supported discs at z ∼1.5 is dominated by dark matter from effective radius scales, in broad agreement with cosmological models. The tension with observations at high stellar mass surface density suggests that the prescriptions for baryonic processes occurring in the most massive galaxies (such as bulge growth and quenching) need to be reassessed.


Puglisi, A., Dudzevičiūtė, U., Swinbank, M., Gillman, S., Tiley, A. L., Bower, R. G., …Sharples, R. M. (2023). KURVS: the outer rotation curve shapes and dark matter fractions of z ∼ 1.5 star-forming galaxies. Monthly Notices of the Royal Astronomical Society, 524(2), 2814-2835.

Journal Article Type Article
Acceptance Date Jun 20, 2023
Online Publication Date Jul 8, 2023
Publication Date 2023-09
Deposit Date Oct 31, 2023
Publicly Available Date Oct 31, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 524
Issue 2
Pages 2814-2835
Keywords Space and Planetary Science; Astronomy and Astrophysics
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