We present a detailed two-dimensional stellar dynamical analysis of a sample of 44 cosmological hydrodynamical simulations of individual central galaxies with stellar masses of 2 × 10 10 M M * 6 × 10 11 M . Kinematic maps of the stellar line-of-sight velocity, velocity dispersion, and higher-order Gauss-Hermite moments h 3 and h 4 are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the λ R -parameter. The velocity, velocity dispersion, h 3 , and h 4 fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS 3D survey. This includes fast (regular), slow, and misaligned rotation, hot spheroids with embedded cold disk components as well as galaxies with counter-rotating cores or central depressions in the velocity dispersion. We link the present day kinematic properties to the individual cosmological formation histories of the galaxies. In general, major galaxy mergers have a significant influence on the rotation properties resulting in both a spin-down as well as a spin-up of the merger remnant. Lower mass galaxies with significant ( 18 per cent) in-situ formation of stars since z ≈ 2, or with additional gas-rich major mergers -resulting in a spin-up -in their formation history, form elongated ( ∼ 0.45) fast rotators (λ R ∼ 0.46) with a clear anti-correlation of h 3 and v/σ. An additional formation path for fast rotators includes gas poor major mergers leading to a spin-up of the remnants (λ R ∼ 0.43). This formation path does not result in anti-correlated h 3 and v/σ. The formation histories of slow rotators can include late major mergers. If the merger is gas-rich the remnant typically is a less flattened slow rotator with a central dip in the velocity dispersion. If the merger is gas poor the remnant is very elongated ( ∼ 0.43) and slowly rotating (λ R ∼ 0.11). The galaxies most consistent with the rare class of nonrotating round early-type galaxies grow by gas-poor minor mergers alone. In general, more massive galaxies have less in-situ star formation since z ∼ 2, rotate slower and have older stellar populations. We discuss general implications for the formation of fast and slowly rotating galaxies as well as the weaknesses and strengths of the underlying models.

We present measurements of the star formation rate (SFR) in the early-type galaxies (ETGs) of the ATLAS 3D sample, based on Wide-field Infrared Survey Explorer (WISE) 22 µm and Galaxy Evolution Explorer far-ultraviolet emission. We combine these with gas masses estimated from 12 CO and H I data in order to investigate the star formation efficiency (SFE) in a larger sample of ETGs than previously available. We first recalibrate (based on WISE data) the relation between old stellar populations (traced at K s -band) and 22 µm luminosity, allowing us to remove the contribution of 22 µm emission from circumstellar dust. We then go on to investigate the position of ETGs on the Kennicutt-Schmidt (KS) relation. Molecular gas-rich ETGs have comparable star formation surface densities to normal spiral galaxy centres, but they lie systematically offset from the KS relation, having lower star formation efficiencies by a factor of ≈2.5 (in agreement with other authors). This effect is driven by galaxies where a substantial fraction of the molecular material is in the rising part of the rotation curve, and shear is high. We show here for the first time that although the number of stars formed per unit gas mass per unit time is lower in ETGs, it seems that the amount of stars formed per freefall time is approximately constant. The scatter around this dynamical relation still correlates with galaxy properties such as the shape of the potential in the inner regions. This leads us to suggest that dynamical properties (such as shear or the global stability of the gas) may be important second parameters that regulate star formation and cause much of the scatter around star-formation relations.

We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS 3D molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a 12 CO(1-0) integrated flux of 18.5 Jy km s −1 ‡, and it represents the largest, best-studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g − r color image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50%), rings (15%), bars+rings (10%), spiral arms (5%), and mildly (12.5%) and strongly (7.5%) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted molecular gas mass across the sample of 2.48 × 10 10 M ⊙ , or approximately 8.3 × 10 8 M ⊙ per minor merger within the sample, consistent with minor merger stellar mass ratios.

We use interferometric 12 CO(1-0) observations to compare and contrast the extent, surface brightness profiles and kinematics of the molecular gas in CO-rich ATLAS 3D early-type galaxies (ETGs) and spiral galaxies. We find that the molecular gas extent is smaller in absolute terms in ETGs than in late-type galaxies, but that the size distributions are similar once scaled by the galaxies optical/stellar characteristic scalelengths. Amongst ETGs, we find that the extent of the gas is independent of its kinematic misalignment (with respect to the stars), but does depend on environment, with Virgo cluster ETGs having less extended molecular gas reservoirs, further emphasizing that cluster ETGs follow different evolutionary pathways from those in the field. Approximately half of ETGs have molecular gas surface brightness profiles that follow the stellar light profile. These systems often have relaxed gas out to large radii, suggesting they are unlikely to have had recent merger/accretion events. A third of the sample galaxies show molecular gas surface brightness profiles that fall off slower than the light, and sometimes show a truncation. These galaxies often have a low mass, and either have disturbed molecular gas, or are in the Virgo cluster, suggesting that recent mergers, ram pressure stripping and/or the presence of hot gas can compress/truncate the gas. The remaining galaxies have rings, or composite profiles, that we argue can be caused by the effects of bars. We investigated the kinematics of the molecular gas using position-velocity diagrams, and compared the observed kinematics with dynamical model predictions, and the observed stellar and ionised gas velocities. We confirm that the molecular gas reaches beyond the turnover of the circular velocity curve in ≈70% of our CO-rich ATLAS 3D ETGs, validating previous work on the CO Tully-Fisher relation. In general we find that in most galaxies the molecular gas is dynamically cold, and the observed CO rotation matches well model predictions of the circular velocity. In the galaxies with the largest molecular masses, dust obscuration and/or population gradients can cause model predictions of the circular velocity to disagree with observations of the molecular gas rotation, however these effects are confined to the most star-forming systems. Bars and non-equilibrium conditions can also make the gas deviate from circular orbits. In both these cases one expects the models circular velocity to be higher than the observed CO velocity, in agreement with our observations. Molecular gas is a better direct tracer of the circular velocity than the ionised gas, justifying its use as a kinematic tracer for Tully-Fisher and similar analyses.

Context. The high degree of deuteration observed in some prestellar cores depends on the ortho-to-para H 2 ratio through the H + 3 fractionation. Aims. We want to constrain the ortho/para H 2 ratio across the L183 prestellar core. This is required to correctly describe the deuteration amplification phenomenon in depleted cores such as L183 and to relate the total (ortho+para) H 2 D + abundance to the sole ortho-H 2 D + column density measurement. Methods. To constrain this ortho/para H 2 ratio and derive its profile, we make use of the N 2 D + /N 2 H + ratio and of the ortho-H 2 D + observations performed across the prestellar core. We use two simple chemical models limited to an almost totally depleted core description. New dissociative recombination and trihydrogen cation-dihydrogen reaction rates (including all isotopologues) are presented in this paper and included in our models. Results. We estimate the H 2 D + ortho/para ratio in the L183 cloud, and constrain the H 2 ortho/para ratio: we show that it varies across the prestellar core by at least an order of magnitude, being still very high (≈0.1) in most of the cloud. Our time-dependent model indicates that the prestellar core is presumably older than 1.5−2 × 10 5 years but that it may not be much older. We also show that it has reached its present density only recently and that its contraction from a uniform density cloud can be constrained. Conclusions. A proper understanding of deuteration chemistry cannot be attained without taking into account the whole ortho/para family of molecular hydrogen and trihydrogen cation isotopologues as their relations are of utmost importance in the global scheme. Tracing the ortho/para H 2 ratio should also place useful constraints on the dynamical evolution of prestellar cores.