[en] We present measurements of the [N ii]/Hα ratio as a probe of gas-phase oxygen abundance for a sample of 419 star-forming galaxies at z = 0.6–2.7 from the KMOS^3D near-IR multi-integral field unit (IFU) survey. The mass–metallicity relation (MZR) is determined consistently with the same sample selection, metallicity tracer, and methodology over the wide redshift range probed by the survey. We find good agreement with long-slit surveys in the literature, except for the low-mass slope of the relation at $z\sim <!--\; ???\; -->2.3$, where this sample is less biased than previous samples based on optical spectroscopic redshifts. In this regime we measure a steeper slope than some literature results. Excluding the contribution from active galactic nuclei from the MZR reduces sensitivity at the high-mass end, but produces otherwise consistent results. There is no significant dependence of the [N ii]/Hα ratio on star formation rate at fixed redshift and stellar mass. The IFU data allow spatially resolved measurements of [N ii]/Hα, from which we can infer abundance gradients for 180 galaxies, thus tripling the current sample in the literature. The observed gradients are on average flat, with only 15 gradients statistically offset from zero at $><!--\; >\; -->3\mathrm{\sigma <!--\; ??\; -->}$. We have modeled the effect of beam smearing, assuming a smooth intrinsic radial gradient and known seeing, inclination, and effective radius for each galaxy. Our seeing-limited observations can recover up to 70% of the intrinsic gradient for the largest, face-on disks, but only 30% for the smaller, more inclined galaxies. We do not find significant trends between observed or corrected gradients and any stellar population, dynamical, or structural galaxy parameters, mostly in agreement with existing studies with much smaller sample sizes. In cosmological simulations, strong feedback is generally required to produce flat gradients at high redshift.

[en] We present the analysis of the fundamental plane (FP) for a sample of 19 massive red-sequence galaxies ($M_{\star <!--\; ???\; -->}><!--\; >\; -->4\times <!--\; ??\; -->{10}^{10}$ $M_{\odot <!--\; ???\; -->}$) in three known overdensities at $1.39<<!--\; <\; -->z<<!--\; <\; -->1.61$ from the K-band Multi-object Spectrograph (KMOS) Cluster Survey, a guaranteed-time program with spectroscopy from the KMOS at the VLT and imaging from the Hubble Space Telescope. As expected, we find that the FP zero-point in B band evolves with redshift, from the value 0.443 of Coma to −0.10 ± 0.09, −0.19 ± 0.05, and −0.29 ± 0.12 for our clusters at z = 1.39, z = 1.46, and z = 1.61, respectively. For the most massive galaxies ($\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\star <!--\; ???\; -->}/M_{\odot <!--\; ???\; -->}><!--\; >\; -->11$) in our sample, we translate the FP zero-point evolution into a mass-to-light-ratio M/L evolution, finding $\mathrm{\Delta <!--\; ??\; -->}\mathrm{l}\mathrm{o}\mathrm{g}M/L_B=(-<!--\; ???\; -->0.46\pm <!--\; ??\; -->0.10)z$, $\mathrm{\Delta <!--\; ??\; -->}\mathrm{l}\mathrm{o}\mathrm{g}M/L_B=(-<!--\; ???\; -->0.52\pm <!--\; ??\; -->0.07)z$, to $\mathrm{\Delta <!--\; ??\; -->}\mathrm{l}\mathrm{o}\mathrm{g}M/L_B=(-<!--\; ???\; -->0.55\pm <!--\; ??\; -->0.10)z$, respectively. We assess the potential contribution of the galaxy structural and stellar velocity dispersion evolution to the evolution of the FP zero-point and find it to be ∼6%–35% of the FP zero-point evolution. The rate of M/L evolution is consistent with galaxies evolving passively. Using single stellar population models, we find an average age of ${2.33}_{-<!--\; ???\; -->0.51}^{+0.86}$ Gyr for the $\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\star <!--\; ???\; -->}/M_{\odot <!--\; ???\; -->}><!--\; >\; -->11$ galaxies in our massive and virialized cluster at z = 1.39, ${1.59}_{-<!--\; ???\; -->0.62}^{+1.40}$ Gyr in a massive but not virialized cluster at z = 1.46, and ${1.20}_{-<!--\; ???\; -->0.47}^{+1.03}$ Gyr in a protocluster at z = 1.61. After accounting for the difference in the age of the universe between redshifts, the ages of the galaxies in the three overdensities are consistent within the errors, with possibly a weak suggestion that galaxies in the most evolved structure are older.

[en] We explore the H α emission in the massive quiescent galaxies observed by the KMOS"3"D survey at 0.7 < z < 2.7. The H α line is robustly detected in 20 out of 120 UVJ -selected quiescent galaxies, and we classify the emission mechanism using the H α line width and the [N ii]/H α line ratio. We find that AGNs are likely to be responsible for the line emission in more than half of the cases. We also find robust evidence for star formation activity in nine quiescent galaxies, which we explore in detail. The H α kinematics reveal rotating disks in five of the nine galaxies. The dust-corrected H α star formation rates are low (0.2–7 M _⊙ yr"−"1), and place these systems significantly below the main sequence. The 24 μ m-based, infrared luminosities, instead, overestimate the star formation rates. These galaxies present a lower gas-phase metallicity compared to star-forming objects with similar stellar mass, and many of them have close companions. We therefore conclude that the low-level star formation activity in these nine quiescent galaxies is likely to be fueled by inflowing gas or minor mergers, and could be a sign of rejuvenation events.

[en] We investigate the stellar populations of 25 massive galaxies ($\mathrm{l}\mathrm{o}\mathrm{g}[M_{\ast <!--\; ???\; -->}/M_{\odot <!--\; ???\; -->}]⩾<!--\; ???\; -->10.9$) at $1.5<<!--\; <\; -->z<<!--\; <\; -->2$ using data obtained with the K-band Multi-Object Spectrograph (KMOS) on the ESO VLT. Targets were selected to be quiescent based on their broadband colors and redshifts using data from the 3D-HST grism survey. The mean redshift of our sample is $\stackrel{¯<!--\; ??\; -->}{z}=1.75$, where KMOS YJ-band data probe age- and metallicity-sensitive absorption features in the rest-frame optical, including the G-band, Fe i, and high-order Balmer lines. Fitting simple stellar population models to a stack of our KMOS spectra, we derive a mean age of ${1.03}_{-<!--\; ???\; -->0.08}^{+0.13}$ Gyr. We confirm previous results suggesting a correlation between color and age for quiescent galaxies, finding mean ages of ${1.22}_{-<!--\; ???\; -->0.19}^{+0.56}$ Gyr and ${0.85}_{-<!--\; ???\; -->0.05}^{+0.08}$ Gyr for the reddest and bluest galaxies in our sample. Combining our KMOS measurements with those obtained from previous studies at $0.2<<!--\; <\; -->z<<!--\; <\; -->2$ we find evidence for a 2–3 Gyr spread in the formation epoch of massive galaxies. At $z<<!--\; <\; -->1$ the measured stellar ages are consistent with passive evolution, while at $1<<!--\; <\; -->z\lesssim <!--\; ???\; -->2$ they appear to saturate at ∼1 Gyr, which likely reflects changing demographics of the (mean) progenitor population. By comparing to star formation histories inferred for “normal” star-forming galaxies, we show that the timescales required to form massive galaxies at $z\gtrsim <!--\; ???\; -->1.5$ are consistent with the enhanced α-element abundances found in massive local early-type galaxies.

[en] We exploit the deep, resolved, Hα kinematic data from the KMOS^3D and SINS/zC-SINF surveys to examine the largely unexplored outer-disk kinematics of star-forming galaxies (SFGs), out to the peak of cosmic star formation. Our sample contains 101 SFGs, representative of the more massive ($9.3\lesssim <!--\; ???\; -->\mathrm{l}\mathrm{o}\mathrm{g}{M}_{\ast <!--\; ???\; -->}/M_{\odot <!--\; ???\; -->}\lesssim <!--\; ???\; -->11.5$) main sequence population at 0.6 ≤ z ≤ 2.6. Through a novel stacking approach, we are able to constrain a representative rotation curve extending out to ∼4 effective radii. This average rotation curve exhibits a significant drop in rotation velocity beyond the turnover, with a slope of $\mathrm{\Delta <!--\; ??\; -->}V/\mathrm{\Delta <!--\; ??\; -->}R=-<!--\; ???\; -->{0.26}_{-<!--\; ???\; -->0.09}^{+0.10}$ in units of normalized coordinates V/V _max and R/R _turn. This result confirms that the fall-off seen in some individual galaxies is a common feature of our sample of high-z disks. The outer fall-off strikingly deviates from the flat or mildly rising rotation curves of local spiral galaxies that have similar masses. Through a comparison with models that include baryons and dark matter, we demonstrate that the falling stacked rotation curve is consistent with a high mass fraction of baryons, relative to the total dark matter halo (m _d ≳ 0.05), in combination with a sizeable level of pressure support in the outer disk. These findings agree with recent studies demonstrating that high-z star-forming disks are strongly baryon-dominated within the disk scale, and furthermore suggest that pressure gradients caused by large, turbulent gas motions are present even in their outer disks. These results are largely independent of our model assumptions, such as the presence of stellar bulges, the effect of adiabatic contraction, and variations in halo concentration.

[en] We present the surface density of luminous active galactic nuclei (AGNs) associated with a uniformly selected galaxy cluster sample identified in the 8.5 deg² Booetes field of the NOAO Deep Wide-Field Survey. The clusters are distributed over a large range of redshift (0 < z < 1.5), and we identify AGN using three different selection criteria: mid-IR color, radio luminosity, and X-ray luminosity. Relative to the field, we note a clear overdensity of the number of AGNs within 0.5 Mpc of the cluster centers at z > 0.5. The amplitude of this AGN overdensity increases with redshift. Although there are significant differences between the AGN populations probed by each selection technique, the rise in cluster AGN surface density generally increases more steeply than that of field quasars. In particular, X-ray-selected AGNs are at least 3 times more prevalent in clusters at 1 < z < 1.5 compared to clusters at 0.5 < z < 1. This effect is stronger than can be explained by the evolving median richness of our cluster sample. We thus confirm the existence of a Butcher-Oemler-type effect for AGN in galaxy clusters, with the number of AGNs in clusters increasing with redshift.

[en] We present half-light sizes measured from $\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}$ emission tracing star formation in 281 star-forming galaxies from the ${\mathrm{K}\mathrm{M}\mathrm{O}\mathrm{S}}^{3\mathrm{D}}$ survey at $0.7\lesssim <!--\; ???\; -->z\lesssim <!--\; ???\; -->2.7$. Sizes are derived by fitting 2D exponential disk models, with bootstrap errors averaging 20%. $\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}$ sizes are a median (mean) of 1.19 (1.26) times larger than those of the stellar continuum—which, due to radial dust gradients, places an upper limit on the growth in stellar size via star formation—with just $\sim <!--\; ???\; -->43\mathrm{\%<!--\; \%\; -->}$ intrinsic scatter. At fixed continuum size the $\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}$ size shows no residual trend with stellar mass, star formation rate, redshift, or morphology. The only significant residual trend is with the excess obscuration of $\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}$ by dust, at fixed continuum obscuration. The scatter in continuum size at fixed stellar mass is likely driven by the scatter in halo spin parameters. The stability of the ratio of $\mathrm{H}\mathrm{\alpha <!--\; ??\; -->}$ size to continuum size demonstrates a high degree of stability in halo spin and in the transfer of angular momentum to the disk over a wide range of physical conditions and cosmic time. This may require local regulation by feedback processes. The implication of our results, as we demonstrate using a toy model, is that our upper limit on star-formation-driven growth is sufficient only to evolve star-forming galaxies approximately along the observed size–mass relation, consistent with the size growth of galaxies at constant cumulative comoving number density. To explain the observed evolution of the size–mass relation of star-forming disk galaxies, other processes, such as the preferential quenching of compact galaxies or galaxy mergers, may be required.

[en] We exploit deep integral-field spectroscopic observations with KMOS/Very Large Telescope of 240 star-forming disks at $0.6<<!--\; <\; -->z<<!--\; <\; -->2.6$ to dynamically constrain their mass budget. Our sample consists of massive ($\gtrsim <!--\; ???\; -->{10}^{9.8}{M}_{\odot <!--\; ???\; -->}$ ) galaxies with sizes $R_e\gtrsim <!--\; ???\; -->2\mathrm{k}\mathrm{p}\mathrm{c}$. By contrasting the observed velocity and dispersion profiles with dynamical models, we find that on average the stellar content contributes ${32}_{-<!--\; ???\; -->7}^{+8}\mathrm{\%<!--\; \%\; -->}$ of the total dynamical mass, with a significant spread among galaxies (68th percentile range $f_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}\sim <!--\; ???\; -->18\mathrm{\%<!--\; \%\; -->}\text{--}62\mathrm{\%<!--\; \%\; -->}$). Including molecular gas as inferred from CO- and dust-based scaling relations, the estimated baryonic mass adds up to ${56}_{-<!--\; ???\; -->12}^{+17}\mathrm{\%<!--\; \%\; -->}$ of the total for the typical galaxy in our sample, reaching $\sim <!--\; ???\; -->90\mathrm{\%<!--\; \%\; -->}$ at $z><!--\; >\; -->2$. We conclude that baryons make up most of the mass within the disk regions of high-redshift star-forming disk galaxies, with typical disks at $z><!--\; >\; -->2$ being strongly baryon-dominated within R _e. Substantial object-to-object variations in both stellar and baryonic mass fractions are observed among the galaxies in our sample, larger than what can be accounted for by the formal uncertainties in their respective measurements. In both cases, the mass fractions correlate most strongly with measures of surface density. High-${\mathrm{\Sigma <!--\; ??\; -->}}_{\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{r}}$ galaxies feature stellar mass fractions closer to unity, and systems with high inferred gas or baryonic surface densities leave less room for additional mass components other than stars and molecular gas. Our findings can be interpreted as more extended disks probing further (and more compact disks probing less far) into the dark matter halos that host them.

[en] We study the dynamical properties of massive quiescent galaxies at 1.4 < z < 2.1 using deep Hubble Space Telescope WFC3/F160W imaging and a combination of literature stellar velocity dispersion measurements and new near-infrared spectra obtained using the K-band Multi Object Spectrograph (KMOS) on the ESO Very Large Telescope. We use these data to show that the typical dynamical-to-stellar mass ratio has increased by ∼0.2 dex from z = 2 to the present day, and we investigate this evolution in the context of possible changes in the stellar initial mass function (IMF) and/or fraction of dark matter contained within the galaxy effective radius, f _DM[<r _e]. Comparing our high-redshift sample to their likely descendants at low redshift, we find that f _DM[<r _e] has increased by a factor of more than 4 since z ≈ 1.8, from f _DM[<r _e] = 6.6% ± 1.0% to ∼24%. The observed increase appears robust to changes in the methods used to estimate dynamical masses or match progenitors and descendants. We quantify possible variation of the stellar IMF through the offset parameter α, defined as the ratio of dynamical mass in stars to the stellar mass estimated using a Chabrier IMF. We demonstrate that the correlation between stellar velocity dispersion and α reported among quiescent galaxies at low redshift is already in place at z = 2, and we argue that subsequent evolution through (mostly minor) merging should act to preserve this relation while contributing significantly to galaxies’ overall growth in size and stellar mass.

[en] We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 1 < z < 5.2 using all three cameras on board the Spitzer Space Telescope. The resulting spectral energy distributions unambiguously show a stellar population in 46 sources and hot dust emission associated with the active nucleus in 59. Using a new rest-frame S_3μm/S_1.6μm versus S_5μm/S_3μm criterion, we identify 42 sources where the rest-frame 1.6 μm emission from the stellar population can be measured. For these radio galaxies, the median stellar mass is high, 2 x 10¹¹ M_sun, and remarkably constant within the range 1 < z < 3. At z>3, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z ∼ 3, but confirmation by more detailed decomposition of stellar and active galactic nucleus (AGN) emission is needed. The rest-frame 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the rest-frame 5 μm hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance-an indicator of jet orientation-is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6'') companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers.