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We analyse maps of the spatially resolved nebular emission of ≈1500 star-forming galaxies at z ≈ 0.6–2.2 from deep K -band Multi-Object Spectrograph and MUSE observations to measure the average shape of their rotation curves. We use these to test claims for declining rotation curves at large radii in galaxies at z ≈ 1–2 that have been interpreted as evidence for an absence of dark matter. We show that the shape of the average rotation curves, and the extent to which they decline beyond their peak velocities, depends upon the normalization prescription used to construct the average curve. Normalizing in size by the galaxy stellar disc-scale length after accounting for seeing effects (⁠|$R_{\rm {d}}^{\prime }$|⁠), we construct stacked position-velocity diagrams that trace the average galaxy rotation curve out to |$6R_{\rm {d}}^{\prime }$| (≈13 kpc, on average). Combining these curves with average H  i rotation curves for local systems, we investigate how the shapes of galaxy rotation curves evolve over ≈10 Gyr. The average rotation curve for galaxies binned in stellar mass, stellar surface mass density and/or redshift is approximately flat, or continues to rise, out to at least |$6R_{\rm {d}}^{\prime }$|⁠. We find a trend between the outer slopes of galaxies' rotation curves and their stellar mass surface densities, with the higher surface density systems exhibiting flatter rotation curves. Drawing comparisons with hydrodynamical simulations, we show that the average shapes of the rotation curves for our sample of massive, star-forming galaxies at z ≈ 0–2.2 are consistent with those expected from lambda cold dark matter theory and imply dark matter fractions within 6 R d of at least ≈60 per cent. [ABSTRACT FROM AUTHOR]

We present dynamical measurements for 586 Hα-detected star-forming galaxies from the KMOS (K-band Multi-Object Spectrograph) Redshift One Spectroscopic Surʋey (KROSS). The sample represents typical star-forming galaxies at this redshift (z = 0.6-1.0), with a median star formation rate of ≈7 M☉ yr-1 and a stellar mass range of log (M☉[M☉]) ≈ 9-11. We find that the rotation ʋelocity-stellar mass relationship (the inʋerse of the Tully- Fisher relationship) for our rotationally dominated sources (ʋC/σ 0 > 1) has a consistent slope and normalization as that obserʋed for z = 0 discs. In contrast, the specific angular momentum (j☉ angular momentum diʋided by stellar mass) is ≈0.2-0.3 dex lower on aʋerage compared to z = 0 discs. The specific angular momentum scales as js ∝ M0.6±0.2 ☉ , consistent with that expected for dark matter (i.e. jDM α M 2/3 DM). We find that z ≈ 0.9 star-forming galaxies haʋe decreasing specific angular momentum with increasing Sérsic index. Visually, the sources with the highest specific angular momentum, for a giʋen mass, haʋe the most disc-dominated morphologies. This implies that an angular momentum-mass-morphology relationship, similar to that obserʋed in local massiʋe galaxies, is already in place by z ≈ 1. [ABSTRACT FROM AUTHOR]

ABSTRACT In Paper I of this series we introduced a volume-limited parent sample of 871 galaxies from which we extracted the ATLAS3D sample of 260 early-type galaxies (ETGs). In Papers II and III we classified the ETGs using their stellar kinematics, in a way that is nearly insensitive to the projection effects, and we separated them into fast and slow rotators. Here we look at galaxy morphology and note that the edge-on fast rotators generally are lenticular galaxies. They appear like spiral galaxies with the gas and dust removed, and in some cases are flat ellipticals (E5 or flatter) with discy isophotes. Fast rotators are often barred and span the same full range of bulge fractions as spiral galaxies. The slow rotators are rounder (E4 or rounder, except for counter-rotating discs) and are generally consistent with being genuine, namely spheroidal-like, elliptical galaxies. We propose a revision to the tuning-fork diagram by Hubble as it gives a misleading description of ETGs by ignoring the large variation in the bulge sizes of fast rotators. Motivated by the fact that only one third (34 per cent) of the ellipticals in our sample are slow rotators, we study for the first time the kinematic morphology-density T-Σ relation using fast and slow rotators to replace lenticulars and ellipticals. We find that our relation is cleaner than using classic morphology. Slow rotators are nearly absent at the lowest density environments [ per cent] and generally constitute a small fraction [ f(SR) ≈ 4 per cent] of the total galaxy population in the relatively low-density environments explored by our survey, with the exception of the densest core of the Virgo cluster [ f(SR) ≈ 20 per cent]. This contrasts with the classic studies that invariably find significant fractions of (misclassified) ellipticals down to the lowest environmental densities. We find a clean log-linear relation between the fraction f(Sp) of spiral galaxies and the local galaxy surface density Σ3, within a cylinder enclosing the three nearest galaxies. This holds for nearly four orders of magnitude in the surface density down to Σ3≈ 0.01 Mpc−2, with f(Sp) decreasing by 10 per cent per dex in Σ3, while f(FR) correspondingly increases. The existence of a smooth kinematic T-Σ relation in the field excludes processes related to the cluster environment, like e.g. ram-pressure stripping, as main contributors to the apparent conversion of spirals into fast rotators in low-density environments. It shows that the segregation is driven by local effects at the small-group scale. This is supported by the relation becoming shallower when using a surface density estimator Σ10 with a cluster scale. Only at the largest densities in the Virgo core does the f(Sp) relation break down and steepen sharply, while the fraction of slow rotators starts to significantly increase. This suggests that a different mechanism is at work there, possibly related to the stripping of the gas from spirals by the hot intergalactic medium in the cluster core and the corresponding lack of cold accretion. [ABSTRACT FROM AUTHOR]

We report the discovery of a powerful molecular wind from the nucleus of the non-interacting nearby S0 field galaxy NGC 1266. The single-dish CO profile exhibits emission to ±400 km s-1 and requires a nested Gaussian fit to be properly described. Interferometric observations reveal a massive, centrally concentrated molecular component with a mass of 1.1 × 109 M ☉ and a molecular outflow with a molecular mass of ≈2.4 × 107 M ☉. The molecular gas close to the systemic velocity consists of a rotating, compact nucleus with a mass of about 4.1 × 108 M ☉ within a radius of ≈60 pc. This compact molecular nucleus has a surface density of ≈2.7 × 104 M ☉ pc-2, more than two orders of magnitude larger than that of giant molecular clouds in the disk of the Milky Way, and it appears to sit on the Kennicutt-Schmidt relation despite its extreme kinematics and energetic activity. We interpret this nucleus as a disk that confines the outflowing wind. A mass outflow rate of ≈13 M ☉ yr-1 leads to a depletion timescale of lsim85 Myr. The star formation in NGC 1266 is insufficient to drive the outflow, and thus it is likely driven by the active galactic nucleus. The concentration of the majority of the molecular gas in the central 100 pc requires an extraordinary loss of angular momentum, but no obvious companion or interacting galaxy is present to enable the transfer. NGC 1266 is the first known outflowing molecular system that does not show any evidence of a recent interaction. [ABSTRACT FROM AUTHOR]

The ATLAS project is a multiwavelength survey combined with a theoretical modelling effort. The observations span from the radio to the millimetre and optical, and provide multicolour imaging, two-dimensional kinematics of the atomic (H ), molecular (CO) and ionized gas (H, [O ] and [N ]), together with the kinematics and population of the stars (H, Fe5015 and Mg b), for a carefully selected, volume-limited ( Mpc) sample of 260 early-type (elliptical E and lenticular S0) galaxies (ETGs). The models include semi-analytic, N-body binary mergers and cosmological simulations of galaxy formation. Here we present the science goals for the project and introduce the galaxy sample and the selection criteria. The sample consists of nearby ( Mpc, |δ− 29°| < 35°, | b| > 15°) morphologically selected ETGs extracted from a parent sample of 871 galaxies (8 per cent E, 22 per cent S0 and 70 per cent spirals) brighter than mag (stellar mass ). We analyse possible selection biases and we conclude that the parent sample is essentially complete and statistically representative of the nearby galaxy population. We present the size-luminosity relation for the spirals and ETGs and show that the ETGs in the ATLAS sample define a tight red sequence in a colour-magnitude diagram, with few objects in the transition from the blue cloud. We describe the strategy of the SAURON integral field observations and the extraction of the stellar kinematics with the p method. We find typical 1 errors of km s km s in the mean velocity, the velocity dispersion and Gauss-Hermite (GH) moments for galaxies with effective dispersion km s. For galaxies with lower (40 per cent of the sample) the GH moments are gradually penalized by p towards zero to suppress the noise produced by the spectral undersampling and only and can be measured. We give an overview of the characteristics of the other main data sets already available for our sample and of the ongoing modelling projects. [ABSTRACT FROM AUTHOR]

We study resolution effects in numerical simulations of gas-rich and gas-poor major mergers, and show that the formation of slowly rotating elliptical galaxies often requires a resolution that is beyond the present-day standards to be properly modelled. Our sample of equal-mass merger models encompasses various masses and spatial resolutions, ranging from about 200 pc and 105 particles per component (stars, gas and dark matter), i.e. a gas mass resolution of , typical of some recently published major merger simulations, to up to 32 pc and in simulations using collisionless particles and gas particles, among the highest resolutions reached so far for gas-rich major merger of massive disc galaxies. We find that the formation of fast-rotating early-type galaxies, that are flattened by a significant residual rotation, is overall correctly reproduced at all such resolutions. However, the formation of slow-rotating early-type galaxies, which have a low-residual angular momentum and are supported mostly by anisotropic velocity dispersions, is strongly resolution-dependent. The evacuation of angular momentum from the main stellar body is largely missed at standard resolution, and systems that should be slow rotators are then found to be fast rotators. The effect is most important for gas-rich mergers, but is also witnessed in mergers with an absent or modest gas component (0–10 per cent in mass). The effect is robust with respect to our initial conditions and interaction orbits, and originates in the physical treatment of the relaxation process during the coalescence of the galaxies. Our findings show that a high-enough resolution is required to accurately model the global properties of merger remnants and the evolution of their angular momentum. The role of gas-rich mergers of spiral galaxies in the formation of slow-rotating ellipticals may therefore have been underestimated. Moreover, the effect of gas in a galaxy merger is not limited to helping the survival/rebuilding of rotating disc components: at high resolution, gas actively participates in the relaxation process and the formation of slowly rotating stellar systems. [ABSTRACT FROM AUTHOR]

Two-dimensional stellar kinematics of 48 representative elliptical (E) and lenticular (S0) galaxies obtained with the SAURON integral-field spectrograph reveal that early-type galaxies appear in two broad flavours, depending on whether they exhibit clear large-scale rotation or not. We define a new parameter , which involves luminosity-weighted averages over the full two-dimensional kinematic field as a proxy to quantify the observed projected stellar angular momentum per unit mass. We use it as a basis for a new kinematic classification: early-type galaxies are separated into slow and fast rotators, depending on whether they have values within their effective radius Re below or above 0.1, respectively. Slow and fast rotators are shown to be physically distinct classes of galaxies, a result which cannot simply be the consequence of a biased viewing angle. Fast rotators tend to be relatively low-luminosity galaxies with . Slow rotators tend to be brighter and more massive galaxies, but are still spread over a wide range of absolute magnitude. Three slow rotators of our sample, among the most massive ones, are consistent with zero rotation. Remarkably, all other slow rotators (besides the atypical case of NGC 4550) contain a large kpc-scale kinematically decoupled core (KDC). All fast rotators (except one galaxy with well-known irregular shells) show well-aligned photometric and kinemetric axes, and small velocity twists, in contrast with most slow rotators which exhibit significant misalignments and velocity twists. These results are supported by a supplement of 18 additional early-type galaxies observed with SAURON. In a companion paper (Paper X), we also show that fast and slow rotators are distinct classes in terms of their orbital distribution. We suggest that gas is a key ingredient in the formation and evolution of fast rotators, and that the slowest rotators are the extreme evolutionary end point reached deep in gravitational potential wells where dissipationless mergers had a major role in the evolution, and for which most of the baryonic angular momentum was expelled outwards. Detailed numerical simulations in a cosmological context are required to understand how to form large-scale KDCs within slow rotators, and more generally to explain the distribution of values within early-type galaxies and the distinction between fast and slow rotators. [ABSTRACT FROM AUTHOR]

We analyse the orbital distribution of elliptical (E) and lenticular (S0) galaxies using SAURON integral-field stellar kinematics within about one effective (half-light) radius. We construct the anisotropy diagram, which relates the ratio of the ordered and random motion in a galaxy ( V/σ) to its observed ellipticity (ℇ), for the 48 E/S0 galaxies from the SAURON survey. For a subsample of 24 galaxies consistent with axisymmetry, we use three-integral axisymmetric Schwarzschild dynamical models to recover the detailed orbital distribution, and we find good agreement with the anisotropy derived from the diagram. In a companion paper (Paper IX), we show that the early-type galaxies can be subdivided into two classes of systems with or without a significant amount of specific stellar angular momentum. Here, we show that the two classes have different distributions on the diagram. The slow rotators are more common among the most massive systems and are generally classified as E from photometry alone. Those in our sample tend to be fairly round , but can have significant kinematical misalignments, indicating that as a class they are moderately triaxial, and span a range of anisotropies . The fast rotators are generally fainter and are classified as either E or S0. They can appear quite flattened , do not show significant kinematical misalignments (unless barred or interacting), indicating they are nearly axisymmetric and span an even larger range of anisotropies . These results are confirmed when we extend our analysis to 18 additional E/S0 galaxies observed with SAURON. The dynamical models indicate that the anisotropy inferred from the diagram is due to a flattening of the velocity ellipsoid in the meridional plane , which we quantify with the β anisotropy parameter. We find a trend of increasing β for intrinsically flatter galaxies. A number of the fast rotators show evidence for containing a flattened, kinematically distinct component, which in some cases counter-rotates relative to the main galaxy body. These components are generally more metal rich than the galaxy body. All these results support the idea that fast rotators are nearly oblate and contain disc-like components. The role of gas must have been important for their formation. The slow rotators are weakly triaxial. Current collisionless merger models seem unable to explain their detailed observed properties. [ABSTRACT FROM AUTHOR]

In this first paper of a series on the structure of boxy and peanut-shaped (B/PS) bulges, Kn-band observations of a sample of 30 edge-on spiral galaxies are described and discussed. Kn-band observations best trace the dominant luminous galactic mass and are minimally affected by dust. Images, unsharp-masked images, as well as major-axis and vertically summed surface brightness profiles are presented and discussed. Galaxies with a B/PS bulge tend to have a more complex morphology than galaxies with other bulge types, more often showing centred or off-centred X structures, secondary maxima along the major-axis and spiral-like structures. While probably not uniquely related to bars, those features are observed in three-dimensional N-body simulations of barred discs and may trace the main bar orbit families. The surface brightness profiles of galaxies with a B/PS bulge are also more complex, typically containing three or more clearly separated regions, including a shallow or flat intermediate region (Freeman Type II profiles). The breaks in the profiles offer evidence for bar-driven transfer of angular momentum and radial redistribution of material. The profiles further suggest a rapid variation of the scaleheight of the disc material, contrary to conventional wisdom but again as expected from the vertical resonances and instabilities present in barred discs. Interestingly, the steep inner region of the surface brightness profiles is often shorter than the isophotally thick part of the galaxies, itself always shorter than the flat intermediate region of the profiles. The steep inner region is also much more prominent along the major-axis than in the vertically summed profiles. Similarly to other recent work but contrary to the standard ‘bulge + disc’ model (where the bulge is both thick and steep), we thus propose that galaxies with a B/PS bulge are composed of a thin concentrated disc (a disc-like bulge) contained within a partially thick bar (the B/PS bulge), itself contained within a thin outer disc. The inner disc likely formed secularly through bar-driven processes and is responsible for the steep inner region of the surface brightness profiles, traditionally associated with a classic bulge, while the bar is responsible for the flat intermediate region of the surface brightness profiles and the thick complex morphological structures observed. Those components are strongly coupled dynamically and are formed mostly of the same (disc) material, shaped by the weak but relentless action of the bar resonances. Any competing formation scenario for galaxies with a B/PS bulge, which represent at least 45 per cent of the local disc galaxy population, must explain equally well and self-consistently the above morphological and photometric properties, the complex gas and stellar kinematics observed, and the correlations between them. [ABSTRACT FROM AUTHOR]

We present absorption line strength maps of 48 representative elliptical and lenticular galaxies obtained as part of a survey of nearby galaxies using our custom-built integral-field spectrograph, SAURON, operating on the William Herschel Telescope. Using high-quality spectra, spatially binned to a constant signal-to-noise ratio, we measure four key age, metallicity and abundance ratio sensitive indices from the Lick/IDS system over a two-dimensional field extending up to approximately one effective radius. A discussion of calibrations and offsets is given, along with a description of error estimation and nebular emission correction. We modify the classical Fe5270 index to define a new index, , which maximizes the useable spatial coverage of SAURON. Maps of Hβ, Fe5015, Mg b and are presented for each galaxy. We use the maps to compute average line strengths integrated over circular apertures of one-eighth effective radius, and compare the resulting relations of index versus velocity dispersion with previous long-slit work. The metal line strength maps show generally negative gradients with increasing radius roughly consistent with the morphology of the light profiles. Remarkable deviations from this general trend exist, particularly the Mg b isoindex contours appear to be flatter than the isophotes of the surface brightness for about 40 per cent of our galaxies without significant dust features. Generally, these galaxies exhibit significant rotation. We infer from this that the fast-rotating component features a higher metallicity and/or an increased Mg/Fe ratio as compared to the galaxy as a whole. The Hβ maps are typically flat or show a mild positive outwards radial gradient, while a few galaxies show strong central peaks and/or elevated overall Hβ strength likely connected to recent star formation activity. For the most prominent post-starburst galaxies, even the metal line strength maps show a reversed gradient. [ABSTRACT FROM AUTHOR]

We have identified two new galaxies with gas counter-rotation (NGC 1596 and 3203) and have confirmed similar behaviour in another one (NGC 128), this using results from separate studies of the ionized-gas and stellar kinematics of a well-defined sample of 30 edge-on disc galaxies. Gas counter-rotators thus represent 10 ± 5 per cent of our sample, but the fraction climbs to 21 ± 11 per cent when only lenticular (S0) galaxies are considered and to 27 ± 13 per cent for S0 galaxies with detected ionized gas only. Those fractions are consistent with but slightly higher than previous studies. A compilation from well-defined studies of S0 galaxies in the literature yields fractions of 15 ± 4 and 23 ± 5 per cent, respectively. Although mainly based on circumstantial evidence, we argue that the counter-rotating gas originates primarily from minor mergers and tidally induced transfer of material from nearby objects. Assuming isotropic accretion, twice those fractions of objects must have undergone similar processes, underlining the importance of (minor) accretion for galaxy evolution. Applications of gas counter-rotators to barred galaxy dynamics are also discussed. [ABSTRACT FROM AUTHOR]

We present a near-infrared Kn-band photometric study of edge-on galaxies with a box/peanut-shaped ‘bulge’. The morphology of the galaxies is analysed using unsharp masking and fits to the vertical surface brightness profiles, and the results are compared to N-body simulations and orbital calculations of barred galaxies. Both theoretical approaches reproduce the main structures observed. [ABSTRACT FROM AUTHOR]

Early results are reported from the SAURON survey of the kinematics and stellar populations of a representative sample of nearby E, S0 and Sa galaxies. The survey is aimed at determining the intrinsic shape of the galaxies, their orbital structure, the mass-to-light ratio as a function of radius, the age and metallicity of the stellar populations, and the frequency of kinematically decoupled cores and nuclear black holes. The construction of the representative sample is described, and its properties are illustrated. A comparison with long-slit spectroscopic data establishes that the SAURON measurements are comparable to, or better than, the highest-quality determinations. Comparisons are presented for NGC 3384 and 4365, where stellar velocities and velocity dispersions are determined to a precision of 6 km s[sup -1], and the h[sub 3] and h[sub 4] parameters of the line-of-sight velocity distribution to a precision of better than 0.02. Extraction of accurate gas emission-line intensities, velocities and linewidths from the data cubes is illustrated for NGC 5813. Comparisons with published line strengths for NGC 3384 and 5813 reveal uncertainties of &lsim;0.1 Å on the measurements of the Hβ, Mg b and Fe5270 indices. Integral-field mapping uniquely connects measurements of the kinematics and stellar populations to the galaxy morphology. The maps presented here illustrate the rich stellar kinematics, gaseous kinematics, and line-strength distributions of early-type galaxies. The results include the discovery of a thin, edge-on, disc in NGC 3623, confirm the axisymmetric shape of the central region of M32, illustrate the LINER nucleus and surrounding counter-rotating star-forming ring in NGC 7742, and suggest a uniform stellar population in the decoupled core galaxy NGC 5813. [ABSTRACT FROM AUTHOR]

We report recent results from the photometric follow-up study we are conducting in the context of the SAURON project. We use ground-based MDM V-band and Spitzer/IRAC 3.6 µm imaging to characterise our sample of E, S0 and Sa galaxies photometrically. Combined with SAURON integral-field spectroscopic observations, this information allows us to explore and understand the location of these galaxies on the Fundamental Plane relation, providing an important diagnostic tool to study their formation and evolution. [ABSTRACT FROM AUTHOR]