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Recent observations have shown that the intrinsic ionised gas velocity dispersion of star-forming galaxies increases with increasing redshift. A number of physical origins have been proposed, such as mergers, higher gas fractions, disk instabilities, and feedback processes, all of which are intricately related to the effective star-formation rates of galaxies. If disruptive processes play a role, it could mean that gas dynamics at high redshift are partly non-gravitational. The dynamics of stars provide the most accurate dynamical masses, but because of signal-to-noise limitations, ionised gas emission lines, such as Halpha, are the principal tracer of gravitational potential at high redshift. The VLT/VIMOS LEGA-C survey combines for the first time the statistics of >3000 K-band selected galaxies at 0.6 < z < 1.0 with ultra-deep 20-hour long integration times on an 8 meter class telescope, allowing both detailed stellar and gas dynamical measurements. I will show for the first time that in the more massive galaxies, the intrinsic gas velocity dispersion is not uniform as usually assumed, but higher in their central regions. I will cross-check high redshift dynamical masses based on both stellar and ionised gas dynamics and discuss the results in light of future observations with upcoming facilities, which will probe the distant universe mainly through emission lines. |
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