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Durham University

Department of Physics

Staff profile

Publication details for Prof David Alexander

Swinbank, M., Harrison, C., Trayford, J., Schaller, M., Smail, I., Schaye, J., Theuns, T., Smit, R., Alexander, D., Bacon, R., Bower, R., Contini, T., Crain, R., de Breuck, C., Decarli, R., Epinat, B., Fumagalli, M., Furlong, M., Galametz, A., Johnson, H.L., Lagos, C., Richard, J., Vernet, J., Sharples, R., Sobral, D. & Stott, J.P. (2017). Angular momentum evolution of galaxies over the past 10 Gyr: a MUSE and KMOS dynamical survey of 400 star-forming galaxies from z = 0.3 to 1.7. Monthly Notices of the Royal Astronomical Society 467(3): 3140-3159.

Author(s) from Durham


We present a MUSE and KMOS dynamical study 405 star-forming galaxies at redshift
z = 0.28–1.65 (median redshift z¯= 0.84). Our sample is representative of the star-forming
“main-sequence”, with star-formation rates of SFR = 0.1–30M⊙ yr−1
and stellar masses
M⋆ = 108–1011 M⊙. For 49 ± 4% of our sample, the dynamics suggest rotational support,
24 ± 3% are unresolved systems and 5 ± 2% appear to be early-stage major mergers with
components on 8–30 kpc scales. The remaining 22 ± 5% appear to be dynamically complex,
irregular (or face-on systems). For galaxies whose dynamics suggest rotational support,
we derive inclination corrected rotational velocities and show these systems lie on a
similar scaling between stellar mass and specific angular momentum as local spirals with
j⋆ = J /M⋆ ∝ M
⋆ but with a redshift evolution that scales as j⋆ ∝ M
⋆ (1 + z)
. We also
identify a correlation between specific angular momentum and disk stability such that galaxies
with the highest specific angular momentum (log(j⋆ / M2/3
⋆ ) > 2.5) are the most stable, with
Toomre Q = 1.10 ± 0.18, compared to Q = 0.53± 0.22 for galaxies with log(j⋆ / M2/3
⋆ ) < 2.5.
At a fixed mass, the HST morphologies of galaxies with the highest specific angular momentum
resemble spiral galaxies, whilst those with low specific angular momentum are morphologically
complex and dominated by several bright star-forming regions. This suggests that
angular momentum plays a major role in defining the stability of gas disks: at z ∼ 1, massive
galaxies that have disks with low specific angular momentum, are globally unstable, clumpy
and turbulent systems. In contrast, galaxies with high specific angular have evolved in to stable
disks with spiral structure where star formation is a local (rather than global) process.