2025A&A...693A.252H -
Astronomy and Astrophysics, volume 693A252 (2025/1-1)
The Lyman alpha reference sample XV. Relating ionised gas kinematics with Lyman-α observables.
HERENZ E.C., SCHAIBLE A., LAURSEN P., RUNNHOLM A., MELINDER J., LE RESTE A., HAYES M.J., OSTLIN G., CANNON J., MICHEVA G., ROTH M. and SAHA K.
Abstract (from CDS):
Gas kinematics affect the radiative transfer and escape of hydrogen Lyman-α (Lyα) emission from galaxies. We investigate this interplay empirically by relating the ionised gas kinematics of 42 galaxies in the extended Lyα Reference Sample (eLARS) with their Lyα escape fractions, $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ , Lyα equivalent widths, EWLyα, and Lyα luminosities, LLyα. To this aim we use PMAS integral-field spectroscopic observations of the Balmer-α line. Our sample contains 18 rotating discs, 13 perturbed rotators, and 13 galaxies with more complex kinematics. The distributions of $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ , EWLyα, and LLyα do not differ significantly between these kinematical classes, but the largest Lyα observables are found amongst the kinematically complex systems. We find no trends between either $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ or EWLyα and kinematic or photometric inclinations. We calculate shearing velocities, vshear, and intrinsic velocity dispersions, $ \sigma_0^\mathrm{obs} $ (empirically corrected for beam-smearing effects), as global kinematical measures for each galaxy. The sample is characterised by highly turbulent motions (30 km s–1 ≲ σ0obs ≲ 80 km s–1) and more than half of the sources show dispersion-dominated kinematics. We uncover clear trends between Lyα observables and global kinematical statistics: EWLyα and LLyα correlate with $ \sigma_0^\mathrm{obs} $ , while $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ anti-correlates with vshear and vshear/σ0obs. Moreover, we find, that galaxies with EWLyα ≥ 20 Å are characterised by higher σ0 and lower vshear/σ0obs than galaxies below this threshold. We discuss the statistical importance of vshear, $ \sigma_0^\mathrm{obs} $ , and vshear/σ0obs for regulating the Lyα observables in comparison to other galaxy parameters. It emerges that $ \sigma_0^\mathrm{obs} $ is the dominating parameter for regulating EWLyα and that is as important as nebular extinction, gas covering fraction, and ionising photon production efficiency in regulating $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ . A simple scenario where the starburst age is simultaneously regulating turbulence, EWLyα, and fescesc is not supported by our observations. However, we show that the small-scale distribution of dust appears to be influenced by turbulence in some galaxies. In support of our observational result, we discuss how turbulence is theoretically expected to play a significant role in modulating $ {f^\mathrm{Ly\alpha}_\mathrm{esc}} $ .
Abstract Copyright:
© The Authors 2025
Journal keyword(s):
radiative transfer - galaxies: ISM - galaxies: kinematics and dynamics - galaxies: starburst
VizieR on-line data:
<Available at CDS (J/A+A/693/A252): cubes.dat cubes/* vfitmaps.dat vfit_fits/*>
Simbad objects:
43
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