@article{11572, abstract = {We present spectroscopic follow-up of candidate luminous Ly α emitters (LAEs) at z = 5.7–6.6 in the SA22 field with VLT/X-SHOOTER. We confirm two new luminous LAEs at z = 5.676 (SR6) and z = 6.532 (VR7), and also present HST follow-up of both sources. These sources have luminosities LLy α ≈ 3 × 1043 erg s−1, very high rest-frame equivalent widths of EW0 ≳ 200 Å and narrow Ly α lines (200–340 km s−1). VR7 is the most UV-luminous LAE at z > 6.5, with M1500 = −22.5, even brighter in the UV than CR7. Besides Ly α, we do not detect any other rest-frame UV lines in the spectra of SR6 and VR7, and argue that rest-frame UV lines are easier to observe in bright galaxies with low Ly α equivalent widths. We confirm that Ly α line widths increase with Ly α luminosity at z = 5.7, while there are indications that Ly α lines of faint LAEs become broader at z = 6.6, potentially due to reionization. We find a large spread of up to 3 dex in UV luminosity for >L⋆ LAEs, but find that the Ly α luminosity of the brightest LAEs is strongly related to UV luminosity at z = 6.6. Under basic assumptions, we find that several LAEs at z ≈ 6–7 have Ly α escape fractions ≳ 100  per cent, indicating bursty star formation histories, alternative Ly α production mechanisms, or dust attenuating Ly α emission differently than UV emission. Finally, we present a method to compute ξion, the production efficiency of ionizing photons, and find that LAEs at z ≈ 6–7 have high values of log10(ξion/Hz erg−1) ≈ 25.51 ± 0.09 that may alleviate the need for high Lyman-Continuum escape fractions required for reionization.}, author = {Matthee, Jorryt J and Sobral, David and Darvish, Behnam and Santos, Sérgio and Mobasher, Bahram and Paulino-Afonso, Ana and Röttgering, Huub and Alegre, Lara}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution – galaxies: high-redshift, dark ages, reionization, first stars, cosmology: observations}, number = {1}, pages = {772--787}, publisher = {Oxford University Press}, title = {{Spectroscopic properties of luminous Ly α emitters at z ≈ 6–7 and comparison to the Lyman-break population}}, doi = {10.1093/mnras/stx2061}, volume = {472}, year = {2017}, } @article{11573, abstract = {We present dynamical measurements from the KMOS (K-band multi-object spectrograph) Deep Survey (KDS), which comprises 77 typical star-forming galaxies at z ≃ 3.5 in the mass range 9.0 < log (M⋆/M⊙) < 10.5. These measurements constrain the internal dynamics, the intrinsic velocity dispersions (σint) and rotation velocities (VC) of galaxies in the high-redshift Universe. The mean velocity dispersion of the galaxies in our sample is σint=70.8+3.3−3.1kms−1⁠, revealing that the increasing average σint with increasing redshift, reported for z ≲ 2, continues out to z ≃ 3.5. Only 36 ± 8 per cent of our galaxies are rotation-dominated (VC/σint > 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 disc scale.}, author = {Turner, O. J. and Cirasuolo, M. and Harrison, C. M. and McLure, R. J. and Dunlop, J. S. and Swinbank, A. M. and Johnson, H. L. and Sobral, D. and Matthee, Jorryt J and Sharples, R. M.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: kinematics and dynamics}, number = {2}, pages = {1280--1320}, publisher = {Oxford University Press}, title = {{The KMOS Deep Survey (KDS) – I. Dynamical measurements of typical star-forming galaxies at z ≃ 3.5}}, doi = {10.1093/mnras/stx1366}, volume = {471}, year = {2017}, } @article{11574, abstract = {We present new results from the widest narrow-band survey search for Lyα emitters at z = 5.7, just after reionization. We survey a total of 7 deg2 spread over the COSMOS, UDS and SA22 fields. We find over 11 000 line emitters, out of which 514 are robust Lyα candidates at z = 5.7 within a volume of 6.3 × 106 Mpc3. Our Lyα emitters span a wide range in Lyα luminosities, from faint to bright (LLyα ∼ 1042.5–44 erg s−1) and rest-frame equivalent widths (EW0 ∼ 25–1000 Å) in a single, homogeneous data set. By combining all our fields, we find that the faint end slope of the z = 5.7 Lyα luminosity function is very steep, with α=−2.3+0.4−0.3⁠. We also present an updated z = 6.6 Lyα luminosity function, based on comparable volumes and obtained with the same methods, which we directly compare with that at z = 5.7. We find a significant decline of the number density of faint Lyα emitters from z = 5.7 to 6.6 (by 0.5 ± 0.1 dex), but no evolution at the bright end/no evolution in L*. Faint Lyα emitters at z = 6.6 show much more extended haloes than those at z = 5.7, suggesting that neutral Hydrogen plays an important role, increasing the scattering and leading to observations missing faint Lyα emission within the epoch of reionization. Altogether, our results suggest that we are observing patchy reionization which happens first around the brightest Lyα emitters, allowing the number densities of those sources to remain unaffected by the increase of neutral Hydrogen fraction from z ∼ 5 to 7.}, author = {Santos, Sérgio and Sobral, David and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: high-redshift, galaxies: luminosity function, mass function, cosmology: observations, dark ages, reionization, first stars}, number = {2}, pages = {1678--1691}, publisher = {Oxford University Press}, title = {{The Lyα luminosity function at z= 5.7–6.6 and the steep drop of the faint end: Implications for reionization}}, doi = {10.1093/mnras/stw2076}, volume = {463}, year = {2016}, } @article{11575, abstract = {We investigate correlations between different physical properties of star-forming galaxies in the ‘Evolution and Assembly of GaLaxies and their Environments’ (EAGLE) cosmological hydrodynamical simulation suite over the redshift range 0 ≤ z ≤ 4.5. A principal component analysis reveals that neutral gas fraction (fgas,neutral), stellar mass (Mstellar) and star formation rate (SFR) account for most of the variance seen in the population, with galaxies tracing a two-dimensional, nearly flat, surface in the three-dimensional space of fgas, neutral–Mstellar–SFR with little scatter. The location of this plane varies little with redshift, whereas galaxies themselves move along the plane as their fgas, neutral and SFR drop with redshift. The positions of galaxies along the plane are highly correlated with gas metallicity. The metallicity can therefore be robustly predicted from fgas, neutral, or from the Mstellar and SFR. We argue that the appearance of this ‘Fundamental Plane of star formation’ is a consequence of self-regulation, with the plane's curvature set by the dependence of the SFR on gas density and metallicity. We analyse a large compilation of observations spanning the redshift range 0 ≲ z ≲ 3, and find that such a plane is also present in the data. The properties of the observed Fundamental Plane of star formation are in good agreement with EAGLE's predictions.}, author = {Lagos, Claudia del P. and Theuns, Tom and Schaye, Joop and Furlong, Michelle and Bower, Richard G. and Schaller, Matthieu and Crain, Robert A. and Trayford, James W. and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics stars: formation, ISM: evolution, galaxies: evolution, galaxies: formation, galaxies: ISM}, number = {3}, pages = {2632--2650}, publisher = {Oxford University Press}, title = {{The Fundamental Plane of star formation in galaxies revealed by the EAGLE hydrodynamical simulations}}, doi = {10.1093/mnras/stw717}, volume = {459}, year = {2016}, } @article{11576, abstract = {We use new near-infrared spectroscopic observations to investigate the nature and evolution of the most luminous Hα emitters at z ∼ 0.8–2.23, which evolve strongly in number density over this period, and compare them to more typical Hα emitters. We study 59 luminous Hα emitters with LHα > L∗Hα⁠, roughly equally split per redshift slice at z ∼ 0.8, 1.47 and 2.23 from the HiZELS and CF-HiZELS surveys. We find that, overall, 30 ± 8 per cent are active galactic nuclei [AGNs; 80 ± 30 per cent of these AGNs are broad-line AGNs, BL-AGNs], and we find little to no evolution in the AGN fraction with redshift, within the errors. However, the AGN fraction increases strongly with Hα luminosity and correlates best with LHα/L∗Hα(z)⁠. While LHα ≤ L∗Hα(z) Hα emitters are largely dominated by star-forming galaxies (>80 per cent), the most luminous Hα emitters (⁠LHα>10L∗Hα(z)⁠) at any cosmic time are essentially all BL-AGN. Using our AGN-decontaminated sample of luminous star-forming galaxies, and integrating down to a fixed Hα luminosity, we find a factor of ∼1300 evolution in the star formation rate density from z = 0 to 2.23. This is much stronger than the evolution from typical Hα star-forming galaxies and in line with the evolution seen for constant luminosity cuts used to select ‘ultraluminous’ infrared galaxies and/or sub-millimetre galaxies. By taking into account the evolution in the typical Hα luminosity, we show that the most strongly star-forming Hα-selected galaxies at any epoch (⁠LHα>L∗Hα(z)⁠) contribute the same fractional amount of ≈15 per cent to the total star formation rate density, at least up to z = 2.23.}, author = {Sobral, David and Kohn, Saul A. and Best, Philip N. and Smail, Ian and Harrison, Chris M. and Stott, John and Calhau, João and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations}, number = {2}, pages = {1739--1752}, publisher = {Oxford University Press}, title = {{The most luminous H α emitters at z ∼ 0.8–2.23 from HiZELS: Evolution of AGN and star-forming galaxies}}, doi = {10.1093/mnras/stw022}, volume = {457}, year = {2016}, } @article{11578, abstract = {We present the first results from our CAlibrating LYMan α with Hα (CALYMHA) pilot survey at the Isaac Newton Telescope. We measure Lyα emission for 488 Hα selected galaxies at z = 2.23 from High-z Emission Line Survey in the COSMOS and UDS fields with a specially designed narrow-band filter (λc = 3918 Å, Δλ = 52 Å). We find 17 dual Hα-Lyα emitters [fLyα > 5 × 10−17 erg s−1 cm−2, of which five are X-ray active galactic nuclei (AGN)]. For star-forming galaxies, we find a range of Lyα escape fractions (fesc, measured with 3 arcsec apertures) from 2 to 30 per cent. These galaxies have masses from 3 × 108 M⊙ to 1011 M⊙ and dust attenuations E(B − V) = 0–0.5. Using stacking, we measure a median escape fraction of 1.6 ± 0.5 per cent (4.0 ± 1.0 per cent without correcting Hα for dust), but show that this depends on galaxy properties. The stacked fesc tends to decrease with increasing star formation rate and dust attenuation. However, at the highest masses and dust attenuations, we detect individual galaxies with fesc much higher than the typical values from stacking, indicating significant scatter in the values of fesc. Relations between fesc and UV slope are bimodal, with high fesc for either the bluest or reddest galaxies. We speculate that this bimodality and large scatter in the values of fesc is due to additional physical mechanisms such as outflows facilitating fesc for dusty/massive systems. Lyα is significantly more extended than Hα and the UV. fesc continues to increase up to at least 20 kpc (3σ, 40 kpc [2σ]) for typical star-forming galaxies and thus the aperture is the most important predictor of fesc.}, author = {Matthee, Jorryt J and Sobral, David and Oteo, Iván and Best, Philip and Smail, Ian and Röttgering, Huub and Paulino-Afonso, Ana}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, galaxies: ISM}, number = {1}, pages = {449--467}, publisher = {Oxford University Press}, title = {{The CALYMHA survey: Lyα escape fraction and its dependence on galaxy properties at z = 2.23}}, doi = {10.1093/mnras/stw322}, volume = {458}, year = {2016}, } @article{11519, abstract = {Faint Lyα emitters become increasingly rarer toward the reionization epoch (z ∼ 6–7). However, observations from a very large (∼5 deg2) Lyα narrow-band survey at z = 6.6 show that this is not the case for the most luminous emitters, capable of ionizing their own local bubbles. Here we present follow-up observations of the two most luminous Lyα candidates in the COSMOS field: “MASOSA” and “CR7.” We used X-SHOOTER, SINFONI, and FORS2 on the Very Large Telescope, and DEIMOS on Keck, to confirm both candidates beyond any doubt. We find redshifts of z = 6.541 and z = 6.604 for “MASOSA” and “CR7,” respectively. MASOSA has a strong detection in Lyα with a line width of 386 ± 30 km s−1 (FWHM) and with very high EW0 (>200 Å), but undetected in the continuum, implying very low stellar mass and a likely young, metal-poor stellar population. “CR7,” with an observed Lyα luminosity of 1043.92±0.05 erg s−1 is the most luminous Lyα emitter ever found at z > 6 and is spatially extended (∼16 kpc). “CR7” reveals a narrow Lyα line with 266 ± 15 km s−1 FWHM, being detected in the near-infrared (NIR) (rest-frame UV; β = −2.3 ± 0.1) and in IRAC/Spitzer. We detect a narrow He II 1640 Å emission line (6σ, FWHM = 130 ± 30 km s−1 ) in CR7 which can explain the clear excess seen in the J-band photometry (EW0 ∼ 80 Å). We find no other emission lines from the UV to the NIR in our X-SHOOTER spectra (He II/O III] 1663 Å > 3 and He II/C III] 1908 Å > 2.5). We conclude that CR7 is best explained by a combination of a PopIII-like population, which dominates the rest-frame UV and the nebular emission, and a more normal stellar population, which presumably dominates the mass. Hubble Space Telescope/WFC3 observations show that the light is indeed spatially separated between a very blue component, coincident with Lyα and He II emission, and two red components (∼5 kpc away), which dominate the mass. Our findings are consistent with theoretical predictions of a PopIII wave, with PopIII star formation migrating away from the original sites of star formation.}, author = {Sobral, David and Matthee, Jorryt J and Darvish, Behnam and Schaerer, Daniel and Mobasher, Bahram and Röttgering, Huub and Santos, Sérgio and Hemmati, Shoubaneh}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, dark ages, reionization, first stars – early universe – galaxies: evolution}, number = {2}, pages = {139}, publisher = {IOP Publishing}, title = {{Evidence for PopIII-like stellar populations in the most luminous Lyα emitters at the epoch of reionisation: Spectroscopic confirmation}}, doi = {10.1088/0004-637X/808/2/139}, volume = {808}, year = {2015}, } @article{11579, abstract = {CR7 is the brightest z = 6.6 Ly α emitter (LAE) known to date, and spectroscopic follow-up by Sobral et al. suggests that CR7 might host Population (Pop) III stars. We examine this interpretation using cosmological hydrodynamical simulations. Several simulated galaxies show the same ‘Pop III wave’ pattern observed in CR7. However, to reproduce the extreme CR7 Ly α/He II1640 line luminosities (⁠Lα/HeII⁠) a top-heavy initial mass function and a massive ( ≳ 107 M⊙) Pop III burst with age ≲ 2 Myr are required. Assuming that the observed properties of Ly α and He II emission are typical for Pop III, we predict that in the COSMOS/UDS/SA22 fields, 14 out of the 30 LAEs at z = 6.6 with Lα > 1043.3 erg s−1 should also host Pop III stars producing an observable LHeII≳1042.7ergs−1⁠. As an alternate explanation, we explore the possibility that CR7 is instead powered by accretion on to a direct collapse black hole. Our model predicts Lα, LHeII⁠, and X-ray luminosities that are in agreement with the observations. In any case, the observed properties of CR7 indicate that this galaxy is most likely powered by sources formed from pristine gas. We propose that further X-ray observations can distinguish between the two above scenarios.}, author = {Pallottini, A. and Ferrara, A. and Pacucci, F. and Gallerani, S. and Salvadori, S. and Schneider, R. and Schaerer, D. and Sobral, D. and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, black hole physics, stars: Population III, galaxies: high-redshift}, number = {3}, pages = {2465--2470}, publisher = {Oxford University Press}, title = {{The brightest Lyα emitter: Pop III or black hole?}}, doi = {10.1093/mnras/stv1795}, volume = {453}, year = {2015}, } @article{11580, abstract = {We present results from the largest contiguous narrow-band survey in the near-infrared. We have used the wide-field infrared camera/Canada–France–Hawaii Telescope and the lowOH2 filter (1.187 ± 0.005 μm) to survey ≈10 deg2 of contiguous extragalactic sky in the SA22 field. A total of ∼6000 candidate emission-line galaxies are found. We use deep ugrizJK data to obtain robust photometric redshifts. We combine our data with the High-redshift(Z) Emission Line Survey (HiZELS), explore spectroscopic surveys (VVDS, VIPERS) and obtain our own spectroscopic follow-up with KMOS, FMOS and MOSFIRE to derive large samples of high-redshift emission-line selected galaxies: 3471 Hα emitters at z = 0.8, 1343 [O III] + Hβ emitters at z = 1.4 and 572 [O II] emitters at z = 2.2. We probe comoving volumes of >106 Mpc3 and find significant overdensities, including an 8.5σ (spectroscopically confirmed) overdensity of Hα emitters at z = 0.81. We derive Hα, [O III] + Hβ and [O II] luminosity functions at z = 0.8, 1.4, 2.2, respectively, and present implications for future surveys such as Euclid. Our uniquely large volumes/areas allow us to subdivide the samples in thousands of randomized combinations of areas and provide a robust empirical measurement of sample/cosmic variance. We show that surveys for star-forming/emission-line galaxies at a depth similar to ours can only overcome cosmic-variance (errors <10 per cent) if they are based on volumes >5 × 105 Mpc3; errors on L* and ϕ* due to sample (cosmic) variance on surveys probing ∼104 and ∼105 Mpc3 are typically very high: ∼300 and ∼40–60 per cent, respectively.}, author = {Sobral, D. and Matthee, Jorryt J and Best, P. N. and Smail, I. and Khostovan, A. A. and Milvang-Jensen, B. and Kim, J.-W. and Stott, J. and Calhau, J. and Nayyeri, H. and Mobasher, B.}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: formation, galaxies: luminosity function, mass function, cosmology: observations, early Universe, large-scale structure of Universe}, number = {3}, pages = {2303--2323}, publisher = {Oxford University Press}, title = {{CF-HiZELS, an ∼10 deg2 emission-line survey with spectroscopic follow-up: Hα, [O III] + Hβ and [O II] luminosity functions at z = 0.8, 1.4 and 2.2 }}, doi = {10.1093/mnras/stv1076}, volume = {451}, year = {2015}, } @article{11582, abstract = {We have observed a sample of typical z ∼ 1 star-forming galaxies, selected from the HiZELS survey, with the new K-band Multi-Object Spectrograph (KMOS) near-infrared, multi-integral field unit instrument on the Very Large Telescope (VLT), in order to obtain their dynamics and metallicity gradients. The majority of our galaxies have a metallicity gradient consistent with being flat or negative (i.e. higher metallicity cores than outskirts). Intriguingly, we find a trend between metallicity gradient and specific star formation rate (sSFR), such that galaxies with a high sSFR tend to have relatively metal poor centres, a result which is strengthened when combined with data sets from the literature. This result appears to explain the discrepancies reported between different high-redshift studies and varying claims for evolution. From a galaxy evolution perspective, the trend we see would mean that a galaxy's sSFR is governed by the amount of metal-poor gas that can be funnelled into its core, triggered either by merging or through efficient accretion. In fact, merging may play a significant role as it is the starburst galaxies at all epochs, which have the more positive metallicity gradients. Our results may help to explain the origin of the fundamental metallicity relation, in which galaxies at a fixed mass are observed to have lower metallicities at higher star formation rates, especially if the metallicity is measured in an aperture encompassing only the central regions of the galaxy. Finally, we note that this study demonstrates the power of KMOS as an efficient instrument for large-scale resolved galaxy surveys.}, author = {Stott, John P. and Sobral, David and Swinbank, A. M. and Smail, Ian and Bower, Richard and Best, Philip N. and Sharples, Ray M. and Geach, James E. and Matthee, Jorryt J}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: abundances, galaxies: evolution, galaxies: kinematics and dynamics}, number = {3}, pages = {2695--2704}, publisher = {Oxford University Press}, title = {{A relationship between specific star formation rate and metallicity gradient within z ∼ 1 galaxies from KMOS-HiZELS}}, doi = {10.1093/mnras/stu1343}, volume = {443}, year = {2014}, } @article{11583, abstract = {Candidate galaxies at redshifts of z ∼ 10 are now being found in extremely deep surveys, probing very small areas. As a consequence, candidates are very faint, making spectroscopic confirmation practically impossible. In order to overcome such limitations, we have undertaken the CF-HiZELS survey, which is a large-area, medium-depth near-infrared narrow-band survey targeted at z = 8.8 Lyman α (Lyα) emitters (LAEs) and covering 10 deg2 in part of the SSA22 field with the Canada–France–Hawaii Telescope (CFHT). We surveyed a comoving volume of 4.7 × 106 Mpc3 to a Lyα luminosity limit of 6.3 × 1043舁erg舁s−1. We look for Lyα candidates by applying the following criteria: (i) clear emission-line source, (ii) no optical detections (ugriz from CFHTLS), (iii) no visible detection in the optical stack (ugriz > 27), (iv) visually checked reliable NBJ and J detections and (v) J − K ≤ 0. We compute photometric redshifts and remove a significant amount of dusty lower redshift line-emitters at z ∼ 1.4 or 2.2. A total of 13 Lyα candidates were found, of which two are marked as strong candidates, but the majority have very weak constraints on their spectral energy distributions. Using follow-up observations with SINFONI/VLT, we are able to exclude the most robust candidates as LAEs. We put a strong constraint on the Lyα luminosity function at z ∼ 9 and make realistic predictions for ongoing and future surveys. Our results show that surveys for the highest redshift LAEs are susceptible of multiple contaminations and that spectroscopic follow-up is absolutely necessary.}, author = {Matthee, Jorryt J and Sobral, David and Swinbank, A. M. and Smail, Ian and Best, P. N. and Kim, Jae-Woo and Franx, Marijn and Milvang-Jensen, Bo and Fynbo, Johan}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution, galaxies: high-redshift, cosmology: observations, dark ages, reionization, first stars}, number = {3}, pages = {2375--2387}, publisher = {Oxford University Press}, title = {{A 10 deg2 Lyman α survey at z=8.8 with spectroscopic follow-up: Strong constraints on the luminosity function and implications for other surveys}}, doi = {10.1093/mnras/stu392}, volume = {440}, year = {2014}, } @article{11520, abstract = {We present the spatially resolved Hα dynamics of 16 star-forming galaxies at z ∼ 0.81 using the new KMOS multi-object integral field spectrograph on the ESO Very Large Telescope. These galaxies, selected using 1.18 μm narrowband imaging from the 10 deg2 CFHT-HiZELS survey of the SA 22 hr field, are found in a ∼4 Mpc overdensity of Hα emitters and likely reside in a group/intermediate environment, but not a cluster. We confirm and identify a rich group of star-forming galaxies at z = 0.813 ± 0.003, with 13 galaxies within 1000 km s−1 of each other, and seven within a diameter of 3 Mpc. All of our galaxies are “typical” star-forming galaxies at their redshift, 0.8 ± 0.4 SFR$^*_{z = 0.8}$, spanning a range of specific star formation rates (sSFRs) of 0.2–1.1 Gyr−1 and have a median metallicity very close to solar of 12 + log(O/H) = 8.62 ± 0.06. We measure the spatially resolved Hα dynamics of the galaxies in our sample and show that 13 out of 16 galaxies can be described by rotating disks and use the data to derive inclination corrected rotation speeds of 50–275 km s−1. The fraction of disks within our sample is 75% ± 8%, consistent with previous results based on Hubble Space Telescope morphologies of Hα-selected galaxies at z ∼ 1 and confirming that disks dominate the SFR density at z ∼ 1. Our Hα galaxies are well fitted by the z ∼ 1–2 Tully–Fisher (TF) relation, confirming the evolution seen in the zero point. Apart from having, on average, higher stellar masses and lower sSFRs, our group galaxies at z = 0.81 present the same mass–metallicity and TF relation as z ∼ 1 field galaxies and are all disk galaxies.}, author = {Sobral, D. and Swinbank, A. M. and Stott, J. P. and Matthee, Jorryt J and Bower, R. G. and Smail, Ian and Best, P. and Geach, J. E. and Sharples, R. M.}, issn = {1538-4357}, journal = {The Astrophysical Journal}, keywords = {Space and Planetary Science, Astronomy and Astrophysics, galaxies: evolution – galaxies, high-redshift – galaxies, starburst}, number = {2}, publisher = {IOP Publishing}, title = {{The dynamics of z=0.8 H-alpha-selected star-forming galaxies from KMOS/CF-HiZELS}}, doi = {10.1088/0004-637x/779/2/139}, volume = {779}, year = {2013}, }