The KMOS Deep Survey (KDS) – I. Dynamical measurements of typical star-forming galaxies at z ≃ 3.5

We present dynamical measurements from the KMOS (K-band Multi-Object Spectrograph) Deep Survey (KDS), which is comprised of 77 typical star-forming galaxies at z z ≃ 3.5 in the mass range 9.0 1), with the sample average VC/σint value much smaller than at lower redshift. After carefully selecting comparable star-forming samples at multiple epochs, we find that the rotation-dominated fraction evolves with redshift with a z−0.2 dependence. The rotation-dominated KDS galaxies show no clear offset from the local rotation velocity-stellar mass (i.e. VC − M⋆) relation, although a smaller fraction of the galaxies are on the relation due to the increase in the dispersion-dominated fraction. These observations are consistent with a simple equilibrium model picture, in which random motions are boosted in high-redshift galaxies by a combination of the increasing gas fractions, accretion efficiency, specific star-formation rate and stellar feedback and which may provide significant pressure support against gravity on the galactic disk scale

Extended Hα over compact far-infrared continuum in dusty submillimeter galaxies

By using data from the Atacama Large Millimeter/submillimeter Array and near-infrared (NIR) integral field spectrographs, including both Spectrograph for INtegral Field Observations in the Near Infrared and K-band Multi Object Spectrograph on the Very Large Telescope, we investigate the two-dimensional distributions of Hα and rest-frame far-infrared (FIR) continuum in six submillimeter galaxies (SMGs) at z ∼ 2. At a similar spatial resolution (∼0.″5 FWHM; ∼4.5 kpc at z = 2), we find that the half-light radius of Hα is significantly larger than that of the FIR continuum in half of the sample, and on average Hα is a median factor of 2.0 ± 0.4 larger. Having explored various ways to correct for the attenuation, we find that the attenuation-corrected Hα-based star-formation rates (SFRs) are systematically lower than the infrared (IR)-based SFRs by at least a median factor of 3 ± 1, which cannot be explained by the difference in half-light radius alone. In addition, we find that in 40% of cases the total V-band attenuation (AV) derived from energy balance modeling of the full ultraviolet (UV)-to-FIR spectral energy distributions (SEDs) is significantly higher than what is derived from SED modeling using only the UV-to-NIR part of the SEDs, and the discrepancy appears to increase with increasing total infrared luminosity. Finally, in considering all of our findings along with the studies in the literature, we postulate that the dust distributions in SMGs, and possibly also in less IR luminous z ∼ 2 massive star-forming galaxies, can be decomposed into the following three main components: the diffuse dust heated by older stellar populations, the more obscured and extended young star-forming H II regions, and the heavily obscured central regions that have a low filling factor but dominate the infrared luminosity in which the majority of attenuation cannot be probed via UV-to-NIR emissions

Effect of salt on the compression of polyelectrolyte brushes in a theta solvent

Classical strong-stretching theory (SST) predicts that, as opposing polyelectrolyte brushes are compressed together in a salt-free theta solvent, they contract so as to maintain a finite polymer-free gap, which offers a potential explanation for the ultra-low frictional forces observed in experiments even with the application of large normal forces. However, the SST ignores chain fluctuations, which would tend to close the gap resulting in physical contact and in turn significant friction. In a preceding study, we examined the effect of fluctuations using self-consistent field theory (SCFT) and illustrated that high normal forces can still be applied before the gap is destroyed. We now look at the effect of adding salt. It is found to reduce the long-range interaction between the brushes but has little effect on the short-range part, provided the concentration does not enter the salted-brush regime. Consequently, the maximum normal force between two planar brushes at the point of contact is remarkably unaffected by salt. For the crossed-cylinder geometry commonly used in experiments, however, there is a gradual reduction because in this case the long-range part of the interaction contributes to the maximum normal force