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 x 10...M... ... M* ...... 6 x 10...M... Kinematic maps of the stellar line-of-sight velocity, velocity dispersion and higher order Gauss-Hermite moments h... and h... are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the ...-parameter. The velocity, velocity dispersion, h... and h... fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS... survey. This includes fast (regular), slow and misaligned rotation, hot spheroids with embedded cold disc 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 (... ... 0.46) with a clear anticorrelation of h3 and v/... An additional formation path for fast rotators includes gas-poor major mergers leading to a spin-up of the remnants (... ... 0.43). This formation path does not result in anticorrelated h... and v/... 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 (... ... 0.11). The galaxies most consistent with the rare class of non-rotating 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. (ProQuest: ... denotes formulae/symbols omitted.)
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 x 10...M... ... M* ...... 6 x 10...M... Kinematic maps of the stellar line-of-sight velocity, velocity dispersion and higher order Gauss-Hermite moments h... and h... are constructed for each central galaxy and for the most massive satellites. The amount of rotation is quantified using the ...-parameter. The velocity, velocity dispersion, h... and h... fields of the simulated galaxies show a diversity similar to observed kinematic maps of early-type galaxies in the ATLAS... survey. This includes fast (regular), slow and misaligned rotation, hot spheroids with embedded cold disc 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 (... ... 0.46) with a clear anticorrelation of h3 and v/... An additional formation path for fast rotators includes gas-poor major mergers leading to a spin-up of the remnants (... ... 0.43). This formation path does not result in anticorrelated h... and v/... 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 (... ... 0.11). The galaxies most consistent with the rare class of non-rotating 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. (ProQuest: ... denotes formulae/symbols omitted.)
We combine JWST and HST imaging with ALMA~CO(2-1) spectroscopy to study the highly turbulent multi-phase intergalactic medium (IGM) in Stephan's Quintet on 25-150 pc scales. Previous Spitzer ...observations revealed luminous H\(_2\) line cooling across a 45 kpc-long filament, created by a giant shock-wave, following the collision with an intruder galaxy NGC~7318b. We demonstrate that the MIRI/F1000W/F770W filters are dominated by 0-0~S(3)~H\(_2\) and a combination of PAH and 0-0~S(5)~H\(_2\) emission. They reveal the dissipation of kinetic energy as massive clouds experience collisions, interactions and likely destruction/re-cycling within different phases of the IGM. In one kpc-scaled structure, warm H\(_2\) formed a triangular-shaped head and tail of compressed and stripped gas behind a narrow shell of cold H\(_2\). In another region, two cold molecular clumps with very different velocities are connected by an arrow-shaped stream of warm, probably shocked, H\(_2\) suggesting a cloud-cloud collision is occurring. In both regions, a high warm-to-cold molecular gas fraction indicates that the cold clouds are being disrupted and converted into warm gas. We also map gas associated with an apparently forming dwarf galaxy. We suggest that the primary mechanism for exciting strong mid-IR H\(_2\) lines throughout Stephan's Quintet is through a fog of warm gas created by the shattering of denser cold molecular clouds and mixing/recycling in the post-shocked gas. A full picture of the diverse kinematics and excitation of the warm H\(_2\) will require future JWST mid-IR spectroscopy. The current observations reveal the rich variety of ways that different gas phases can interact with one another.
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