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High-velocity outflows are ubiquitous in compact, massive (M$_* \sim$ 10$^{11}$ M$_{\odot}$), z $\sim$ 0.5 galaxies with extreme star formation surface densities ($\Sigma_{SFR} \sim$ 2000 M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$). We have previously detected and characterized these outflows using MgII absorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [OII] and MgII emission nebulae surrounding all of the 12 galaxies in this study. We find that [OII] is more effective than MgII in tracing low surface brightness, extended emission in these galaxies. The [OII] nebulae are spatially extended beyond the stars, with radial extent R$_{90}$ between 10 and 40 kpc. The nebulae exhibit non-gravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from -335 to -1920 km s$^{-1}$. The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last $<$ 3 Myr) exhibit the highest central velocity dispersions ($\sigma >$ 400 km s$^{-1}$), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the CGM and mix on timescales $>$ 50 Myr., Comment: Accepted for publication in The Astrophysical Journal

Many quiescent galaxies discovered in the early Universe by \textit{JWST} raise fundamental questions on when and how these galaxies became and stayed quenched. Making use of the latest version of the semi-analytic model GAEA that provides good agreement with the observed quenched fractions up to $z\sim 3$, we make predictions for the expected fractions of quiescent galaxies up to $z\sim 7$ and analyze the main quenching mechanism. We find that in a simulated box of $685~{\rm Mpc}$ on a side, the first quenched massive ($M_{\star} \sim 10^{11} {\rm M}_{\odot}$), Milky Way mass, and low mass ($M_{\star} \sim 10^{9.5} {\rm M}_{\odot}$ ) galaxies appear at $z\sim 4.5$, $z\sim 6.2$, and before $z = 7$. Most quenched galaxies identified at early redshifts remain quenched for more than 1 Gyr. Independently of galaxy stellar mass, the dominant quenching mechanism at high redshift is accretion disk feedback (quasar winds) from a central massive black hole, which is triggered by mergers in massive and MW-mass galaxies, and by disk instabilities in low-mass galaxies. Environmental stripping becomes increasingly more important at lower redshift., Comment: 8 pages, 3 figures, Accepted publication in APJL

A new class of extragalactic astronomical sources discovered in 2021, named Odd Radio Circles (ORCs, Norris et al. 2021), are large rings of faint, diffuse radio continuum emission spanning ~1 arcminute on the sky. Galaxies at the centers of several ORCs have photometric redshifts of z~0.3-0.6, implying physical scales of several 100 kiloparsecs in diameter for the radio emission, the origin of which is unknown. Here we report spectroscopic data on an ORC including strong [OII] emission tracing ionized gas in the central galaxy of ORC4 at z=0.4512. The physical extent of the [OII] emission is ~40 kpc in diameter, larger than expected for a typical early-type galaxy (Pandya et al, 2017) but an order of magnitude smaller than the large-scale radio continuum emission. We detect a ~200 km/s velocity gradient across the [OII] nebula, as well as a high velocity dispersion of ~180 km/s. The [OII] equivalent width (EW, ~50 Ang) is extremely high for a quiescent galaxy. The morphology, kinematics, and strength of the [OII] emission are consistent with the infall of shock ionized gas near the galaxy, following a larger-scale, outward moving shock driven by a galactic wind. Both the extended optical and radio emission, while observed on very different scales, may therefore result from the same dramatic event., Comment: 7 figures, accepted to Nature

We explore models of massive ($\gt 10^{10}~{\rm M}_{\odot}$) satellite quenching in massive clusters at $z\gtrsim1$ using an MCMC framework, focusing on two primary parameters: $R_{\rm quench}$ (the host-centric radius at which quenching begins) and $\tau_{\rm quench}$ (the timescale upon which a satellite quenches after crossing $R_{\rm quench}$). Our MCMC analysis shows two local maxima in the 1D posterior probability distribution of $R_{\rm quench}$ at approximately $0.25$ and $1.0~R_{\rm{200}}$. Analyzing four distinct solutions in the $\tau_{\rm quench}$-$R_{\rm quench}$ parameter space, nearly all of which yield quiescent fractions consistent with observational data from the GOGREEN survey, we investigate whether these solutions represent distinct quenching pathways and find that they can be separated between \textquote{starvation} and \textquote{core quenching} scenarios. The starvation pathway is characterized by quenching timescales that are roughly consistent with the total cold gas (H$_{2}$+H{\scriptsize I}) depletion timescale at intermediate $z$, while core quenching is characterized by satellites with relatively high line-of-sight velocities that quench on short timescales ($\sim 0.25$ Gyr) after reaching the inner region of the cluster ($\lt 0.30~R_{\rm{200}}$). Lastly, we break the degeneracy between these solutions by comparing the observed properties of transition galaxies from the GOGREEN survey. We conclude that only the \textquote{starvation} pathway is consistent with the projected phase-space distribution and relative abundance of transition galaxies at $z \sim 1$. However, we acknowledge that ram pressure might contribute as a secondary quenching mechanism., Comment: 15 pages; 8 figures; Accepted for publication in Monthly Notices of the Royal Astronomical Society

We present results on the properties of extreme gas outflows in massive ($\rm M_* \sim$10$^{11} \ \rm M_{\odot}$), compact, starburst ($\rm SFR \sim$$200 \, \rm M_{\odot} \ yr^{-1}$) galaxies at z = $0.4-0.7$ with very high star formation surface densities ($\rm \Sigma_{SFR} \sim$$2000 \,\rm M_{\odot} \ yr^{-1} \ kpc^{-2}$). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies we identify outflows with maximum velocities of $820 - 2860$ \kmps. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T $\sim$10$^4$ K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously-distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies' star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong \mgii \ absorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of $\rm \sim$50 $-$ 2200 $\rm M_{\odot} \, yr^{-1}$, assuming a fiducial outflow size of 5 kpc, and mass loading factors of $\eta\sim$5 for most of the sample. %with $\eta\sim$20 for two galaxies. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution., Comment: Accepted for publication in The Astrophysical Journal

The Makani galaxy hosts the poster child of a galactic wind on scales of the circumgalactic medium. It consists of a two-episode wind in which the slow, outer wind originated 400 Myr ago (Episode I; R_I = 20-50 kpc) and the fast, inner wind is 7 Myr old (Episode II; R_II = 0-20 kpc). While this wind contains ionized, neutral, and molecular gas, the physical state and mass of the most extended phase--the warm, ionized gas--is unknown. Here we present Keck optical spectra of the Makani outflow. These allow us to detect hydrogen lines out to r = 30-40 kpc and thus constrain the mass, momentum, and energy in the wind. Many collisionally-excited lines are detected throughout the wind, and their line ratios are consistent with 200-400 km/s shocks that power the ionized gas, with v_shock = $\sigma$_wind. Combining shock models, density-sensitive line ratios, and mass and velocity measurements, we estimate that the ionized mass and outflow rate in the Episode II wind could be as high as that of the molecular gas: M_II(HII) ~ M_II(H_2) = (1-2)x10^9 Msun and dM/dt_II(HII) ~ dM/dt_II(H_2) = 170-250 Msun/yr. The outer wind has slowed, so that dM/dt_I(HII) ~ 10 Msun/yr, but it contains more ionized gas: M_I(HII) = 5x10^9 Msun. The momentum and energy in the recent Episode II wind imply a momentum-driven flow (p ``boost" ~ 7) driven by the hot ejecta and radiation pressure from the Eddington-limited, compact starburst. Much of the energy and momentum in the older Episode I wind may reside in a hotter phase, or lie further into the CGM., Comment: ApJ, in press

We present a measurement of the intrinsic space density of intermediate redshift ($z\sim0.5$), massive ($M_{*} \sim 10^{11} \ \text{M}_{\odot}$), compact ($R_{e} \sim 100$ pc) starburst ($\Sigma_{SFR} \sim 1000 \ \text{M}_{\odot} \ \text{yr}^{-1} \text{kpc}^{-1}$) galaxies with tidal features indicative of them having undergone recent major mergers. A subset of them host kiloparsec scale, $>1000 \ \text{km}\ \text{s}^{-1}$ outflows and have little indication of AGN activity, suggesting that extreme star formation can be a primary driver of large-scale feedback. The aim for this paper is to calculate their space density so we can place them in a better cosmological context. We do this by empirically modeling the stellar populations of massive, compact starburst galaxies. We determine the average timescale for which galaxies that have recently undergone an extreme nuclear starburst would be targeted and included in our spectroscopically selected sample. We find that massive, compact starburst galaxies targeted by our criteria would be selectable for $\sim 148 ^{+27}_{-24}$ Myr and have an intrinsic space density $n_{\text{CS}} \sim (1.1^{+0.5}_{-0.3}) \times 10^{-6} \ \ \text{Mpc}^{-3}$. This space density is broadly consistent with our $z\sim0.5$ compact starbursts being the most extremely compact and star forming low redshift analogs of the compact star forming galaxies in the early Universe as well as them being the progenitors to a fraction of intermediate redshift post starburst and compact quiescent galaxies., Comment: 27 pages, 13 figures, accepted for publication in the Astrophysical Journal

We investigate the role of environment on star-formation rates of galaxies at various cosmic densities in well-studied clusters. We present the star-forming main sequence for 163 galaxies in four EDisCS clusters in the range 0.4 $<$ z $<$ 0.7. We use {\em Hubble Space Telescope}/Wide Field Camera 3 observations of the H$\alpha$ emission line to span three distinct local environments: the cluster core, infall region, and external field galaxies. The main sequence defined from our observations is consistent with other published H$\alpha$ distributions at similar redshifts, but differs from those derived from star-formation tracers such as 24$\mu$m. We find that the H$\alpha$-derived star-formation rates for the 67 galaxies with stellar masses greater than the mass-completeness limit of M$_*>$ 10$^{9.75}$M\textsubscript{\(\odot\)} show little dependence on environment. At face value, the similarities in the star-formation rate distributions in the three environments may indicate that the process of finally shutting down star formation is rapid, however, the depth of our data and size of our sample make it difficult to conclusively test this scenario. Despite having significant H$\alpha$ emission, 21 galaxies are classified as {\em UVJ}-quiescent and may represent a demonstration of the quenching of star formation caught in the act., Comment: 25 pages, 15 figures, 5 tables. Accepted for publication in Monthly Notices of the Royal Astronomical Society

We present results on the nature of extreme ejective feedback episodes and the physical conditions of a population of massive ($\rm M_* \sim 10^{11} M_{\odot}$), compact starburst galaxies at z = 0.4-0.7. We use data from Keck/NIRSPEC, SDSS, Gemini/GMOS, MMT, and Magellan/MagE to measure rest-frame optical and near-IR spectra of 14 starburst galaxies with extremely high star formation rate surface densities (mean $\rm \Sigma_{SFR} \sim 3000 \,M_{\odot} yr^{-1} kpc^{-2}$) and powerful galactic outflows (maximum speeds v$_{98} \sim$ 1000-3000 km s$^{-1}$). Our unique data set includes an ensemble of both emission [OII]$\lambda\lambda$3726,3729, H$\beta$, [OIII]$\lambda\lambda$4959,5007, H$\alpha$, [NII]$\lambda\lambda$6548,6583, and [SII]$\lambda\lambda$6716,6731) and absorption MgII$\lambda\lambda$2796,2803, and FeII$\lambda$2586) lines that allow us to investigate the kinematics of the cool gas phase (T$\sim$10$^4$ K) in the outflows. Employing a suite of line ratio diagnostic diagrams, we find that the central starbursts are characterized by high electron densities (median n$_e \sim$ 530 cm$^{-3}$), and high metallicity (solar or super-solar). We show that the outflows are most likely driven by stellar feedback emerging from the extreme central starburst, rather than by an AGN. We also present multiple intriguing observational signatures suggesting that these galaxies may have substantial Lyman continuum (LyC) photon leakage, including weak [SII] nebular emission lines. Our results imply that these galaxies may be captured in a short-lived phase of extreme star formation and feedback where much of their gas is violently blown out by powerful outflows that open up channels for LyC photons to escape.

We present multi-band Hubble Space Telescope imaging that spans rest-frame near-ultraviolet through near-infrared wavelengths (0.3-1.1 $\mu$m) for 12 compact starburst galaxies at z=0.4-0.8. These massive galaxies (M_stellar ~ 10^11 M_Sun) are driving very fast outflows ($v_{max}$=1000-3000 km/s), and their light profiles are dominated by an extremely compact starburst component (half-light radius ~ 100 pc). Our goal is to constrain the physical mechanisms responsible for launching these fast outflows by measuring the physical conditions within the central kiloparsec. Based on our stellar population analysis, the central component typically contributes $\approx$25% of the total stellar mass and the central escape velocities $v_{esc,central}\approx900$ km/s are a factor of two smaller than the observed outflow velocities. This requires physical mechanisms that can accelerate gas to speeds significantly beyond the central escape velocities, and it makes clear that these fast outflows are capable of traveling into the circumgalactic medium, and potentially beyond. We find central stellar densities comparable to theoretical estimates of the Eddington limit, and we estimate $\Sigma_1$ surface densities within the central kpc comparable to those of compact massive galaxies at $0.5

Feedback through energetic outflows has emerged as a key physical process responsible for transforming star-forming galaxies into the quiescent systems observed in the local universe. To explore this process, this paper focuses on a sample of massive and compact merger remnant galaxies hosting high-velocity gaseous outflows ($|v| \gtrsim 10^{3}$ km s$^{-1}$), found at intermediate redshift ($z \sim 0.6$). From their mid-infrared emission and compact morphologies, these galaxies are estimated to have exceptionally large star formation rate (SFR) surface densities ($\Sigma_{SFR} \sim 10^{3}$ $\mathrm{M_{\odot}}$ yr$^{-1}$ kpc$^{-2}$), approaching the Eddington limit for radiation pressure on dust grains. This suggests that star formation feedback may be driving the observed outflows. However, these SFR estimates suffer from significant uncertainties. We therefore sought an independent tracer of star formation to probe the compact starburst activity in these systems. In this paper, we present SFR estimates calculated using 1.5 GHz continuum Jansky Very Large Array observations for 19 of these galaxies. We also present updated infrared (IR) SFRs calculated from WISE survey data. We estimate SFRs from the IR to be larger than those from the radio for 16 out of 19 galaxies by a median factor of 2.5. We find that this deviation is maximized for the most compact galaxies hosting the youngest stellar populations, suggesting that compact starbursts deviate from the IR-radio correlation. We suggest that this deviation stems either from free-free absorption of synchrotron emission, a difference in the timescale over which each indicator traces star formation, or exceptionally hot IR-emitting dust in these ultra-dense galaxies., Comment: 15 pages, 9 figures, 2 tables; accepted for publication in ApJ

We present a study of the relation between galaxy stellar age and mass for 14 members of the $z=1.62$ protocluster IRC 0218, using multiband imaging and HST G102 and G141 grism spectroscopy. Using $UVJ$ colors to separate galaxies into star forming and quiescent populations, we find that at stellar masses $M_* \geq 10^{10.85} M_{\odot}$, the quiescent fraction in the protocluster is $f_Q=1.0^{+0.00}_{-0.37}$, consistent with a $\sim 2\times $ enhancement relative to the field value, $f_Q=0.45^{+0.03}_{-0.03}$. At masses $10^{10.2} M_{\odot} \leq M_* \leq 10^{10.85} M_{\odot}$, $f_Q$ in the cluster is $f_Q=0.40^{+0.20}_{-0.18}$, consistent with the field value of $f_Q=0.28^{+0.02}_{-0.02}$. Using galaxy $D_{n}(4000)$ values derived from the G102 spectroscopy, we find no relation between galaxy stellar age and mass. These results may reflect the impact of merger-driven mass redistribution, which is plausible as this cluster is known to host many dry mergers. Alternately, they may imply that the trend in $f_Q$ in IRC 0218 was imprinted over a short timescale in the protocluster's assembly history. Comparing our results with those of other high-redshift studies and studies of clusters at $z\sim 1$, we determine that our observed relation between $f_Q$ and stellar mass only mildly evolves between $z\sim 1.6$ and $z \sim 1$, and only at stellar masses $M_* \leq 10^{10.85} M_{\odot}$. Both the $z\sim 1$ and $z\sim 1.6$ results are in agreement that the red sequence in dense environments was already populated at high redshift, $z \ge 3$, placing constraints on the mechanism(s) responsible for quenching in dense environments at $z\ge 1.5$, Comment: 17 pages, 8 figures, 3 tables. Accepted for publication in ApJ

We identify a strong lensing galaxy in the cluster IRC 0218 (also known as XMM-LSS J02182$-$05102) that is spectroscopically confirmed to be at $z=1.62$, making it the highest-redshift strong lens galaxy known. The lens is one of the two brightest cluster galaxies and lenses a background source galaxy into an arc and a counterimage. With Hubble Space Telescope (HST) grism and Keck/LRIS spectroscopy, we measure the source redshift to be $z_{\rm S}=2.26$. Using HST imaging in ACS/F475W, ACS/F814W, WFC3/F125W, and WFC3/F160W, we model the lens mass distribution with an elliptical power-law profile and account for the effects of the cluster halo and nearby galaxies. The Einstein radius is $\theta_{\rm E}=0.38^{+0.02}_{-0.01}$" ($3.2_{-0.1}^{+0.2}$ kpc) and the total enclosed mass is M$_{\rm tot} (< \theta_{\rm E})=1.8^{+0.2}_{-0.1}\times10^{11}~{\rm M}_{\odot}$. We estimate that the cluster environment contributes $\sim10$% of this total mass. Assuming a Chabrier IMF, the dark matter fraction within $\theta_{{\rm E}}$ is $f_{\rm DM}^{{\rm Chab}} = 0.3_{-0.3}^{+0.1}$, while a Salpeter IMF is marginally inconsistent with the enclosed mass ($f_{\rm DM}^{{\rm Salp}} = -0.3_{-0.5}^{+0.2}$). The total magnification of the source is $\mu_{\rm tot}=2.1_{-0.3}^{+0.4}$. The source has at least one bright compact region offset from the source center. Emission from Ly$\alpha$ and [O III] are likely to probe different regions in the source., Comment: Accepted for publication in ApJL; emulateapj format; 6 pages, 3 figures, 1 table

[Abridged] Using public data from the NMBS and CANDELS surveys, we study the population of massive galaxies at z>3 to identify the potential progenitors of z~2 compact, massive, quiescent (CMQ) galaxies, furthering our understanding of the evolution of massive galaxies. Our work is enabled by high-resolution CANDELS images and accurate photometric redshifts, stellar masses and star formation rates (SFRs) from 37-band NMBS photometry. The total number of z>3 massive galaxies is consistent with the number of massive quiescent (MQ) galaxies at z~2, implying that the SFRs for all of these galaxies must be much lower by z~2. We discover 4 CMQ galaxies at z>3, pushing back the time for which such galaxies have been observed. However, the volume density for these galaxies is significantly less than that of galaxies at z<2 with similar masses, SFRs, and sizes, implying that additional CMQ galaxies must be created in the ~1 Gyr between z=3 and z=2. We find 5 star-forming galaxies at z~3 that are compact (Re<1.4 kpc) and have stellar mass M*>10^(10.6)Msun, likely to become members of the CMQ galaxy population at z~2. We evolve the stellar masses and SFRs of each individual z>3 galaxy adopting 5 different star formation histories (SFHs) and studying the resulting population of massive galaxies at z=2.3. We find that declining or truncated SFHs are necessary to match the observed number density of MQ galaxies at z~2, whereas a constant SFH results in a number density significantly smaller than observed. All of our assumed SFHs imply number densities of CMQ galaxies at z~2 that are consistent with the observed number density. Better agreement with the observed number density of CMQ galaxies at z~2 is obtained if merging is included in the analysis and better still if star formation quenching is assumed to shortly follow the merging event, as implied by recent models of formation of MQ galaxies., Comment: Re-submitted to ApJ after addressing referee's report

We present the discovery of compact, obscured star formation in galaxies at z ~ 0.6 that exhibit >1000 km/s outflows. Using optical morphologies from the Hubble Space Telescope and infrared photometry from the Wide-field Infrared Survey Explorer, we estimate star formation rate (SFR) surface densities that approach Sigma_SFR ~ 3000 Msun/yr/kpc^2, comparable to the Eddington limit from radiation pressure on dust grains. We argue that feedback associated with a compact starburst in the form of radiation pressure from massive stars and ram pressure from supernovae and stellar winds is sufficient to produce the high-velocity outflows we observe, without the need to invoke feedback from an active galactic nucleus., Comment: 6 pages, 4 figures, accepted for publication in ApJ Letters

We study the red sequence in a cluster of galaxies at z=1.62 and follow its evolution over the intervening 9.5 Gyr to the present day. Using deep YJKs imaging with the HAWK-I instrument on the VLT we identify a tight red sequence and construct its rest-frame i-band luminosity function (LF). There is a marked deficit of faint red galaxies in the cluster that causes a turnover in the LF. We compare the red sequence LF to that for clusters at z<0.8 correcting the luminosities for passive evolution. The shape of the cluster red sequence LF does not evolve between z=1.62 and z=0.6 but at z<0.6 the faint population builds up significantly. Meanwhile, between z=1.62 to 0.6 the inferred total light on the red sequence grows by a factor of about 2 and the bright end of the LF becomes more populated. We construct a simple model for red sequence evolution that grows the red sequence in total luminosity and matches the constant LF shape at z>0.6. In this model the cluster accretes blue galaxies from the field that are then quenched and subsequently allowed to merge. We find that 3--4 mergers among cluster galaxies during the 4 Gyr between z=1.62 and z=0.6 matches the observed luminosity function evolution between the two redshifts. The inferred merger rate is consistent with other studies of this cluster. Our result supports the picture that galaxy merging during the major growth phase of massive clusters is an important process in shaping the red sequence population at all luminosities., Comment: 15 pages, 7 figures, accepted for publication in the Astrophysical Journal. With respect to previous version, the likely descendants of the z=1.62 cluster now have a more modest mass and the required luminosity growth on the red sequence is slightly lower. No major conclusions have changed

We study the morphological content of a large sample of high-redshift clusters to determine its dependence on cluster mass and redshift. Quantitative morphologies are based on bulge+disk decompositions of cluster and field galaxies on deep VLT/FORS2 images of 18 optically-selected clusters at 0.45 < z < 0.80 from the ESO Distant Cluster Survey (EDisCS). Morphological content is given by the early-type galaxy fraction f_et, and early-type galaxies are selected based on their bulge fraction and image smoothness. A set of 158 SDSS clusters is analyzed exactly as the EDisCS sample to provide a robust local comparison. Our main results are: (1) f_et values for the SDSS and EDisCS clusters exhibit no clear trend as a function of sigma. (2) Mid-z EDisCS clusters around sigma = 500 km/s have f_et ~= 0.5 whereas high-z EDisCS clusters have f_et ~= 0.4 (~25% increase over 2 Gyrs). (3) There is a marked difference in the morphological content of EDisCS and SDSS clusters. None of the EDisCS clusters have f_et greater than 0.6 whereas half of the SDSS clusters lie above this value. This difference is seen in clusters of all velocity dispersions. (4) There is a strong correlation between morphology and star formation in SDSS and EDisCS clusters. This correlation holds independent of sigma and z even though the fraction of [OII] emitters decreases from z~0.8 to z~0.06 in all environments. Our results pose an interesting challenge to structural transformation and star formation quenching processes that strongly depend on the global cluster environment and suggest that cluster membership may be of lesser importance than other variables in determining galaxy properties. (ABRIDGED), Comment: 22 pages, 10 figures, accepted for publication in A&A

AIMS. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. METHODS. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. RESULTS. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. CONCLUSIONS. Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166-1080 km/s., Comment: 31 pages, 23 figures, accepted for publication in A&A