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We use the SAMI Galaxy Survey to examine the drivers of galaxy spin, |$\lambda _{R_{\rm e}}$|⁠ , in a multidimensional parameter space including stellar mass, stellar population age (or specific star formation rate), and various environmental metrics (local density, halo mass, satellite versus central). Using a partial correlation analysis, we consistently find that age or specific star formation rate is the primary parameter correlating with spin. Light-weighted age and specific star formation rate are more strongly correlated with spin than mass-weighted age. In fact, across our sample, once the relation between light-weighted age and spin is accounted for, there is no significant residual correlation between spin and mass, or spin and environment. This result is strongly suggestive that the present-day environment only indirectly influences spin, via the removal of gas and star formation quenching. That is, environment affects age, then age affects spin. Older galaxies then have lower spin, either due to stars being born dynamically hotter at high redshift, or due to secular heating. Our results appear to rule out environmentally dependent dynamical heating (e.g. galaxy–galaxy interactions) being important, at least within 1  R e where our kinematic measurements are made. The picture is more complex when we only consider high-mass galaxies (M * ≳ 1011 M⊙). While the age-spin relation is still strong for these high-mass galaxies, there is a residual environmental trend with central galaxies preferentially having lower spin, compared to satellites of the same age and mass. We argue that this trend is likely due to central galaxies being a preferred location for mergers. [ABSTRACT FROM AUTHOR]

We explore local and global dynamical differences between the kinematics of ionized gas and stars in a sample of galaxies from Data Release 3 of the SAMI Galaxy Survey. We find better agreement between local (i.e. comparing on a spaxel-to-spaxel basis) velocities and dispersion of gas and stars in younger systems as with previous work on the asymmetric drift in galaxies, suggesting that the dynamics of stars and ionized gas are initially coupled. The intrinsic scatter around the velocity and dispersion relations increases with increasing stellar age and mass, suggesting that subsequent mechanisms, such as internal processes, divergent star formation, and assembly histories, also play a role in setting and altering the dynamics of galaxies. The global (flux-weighted) dynamical support of older galaxies is hotter than in younger systems. We find that the ionized gas in galaxies is almost always dynamically colder than the stars with a steeper velocity gradient. In absolute terms, the local difference in velocity dispersion is more pronounced than the local difference in velocity, possibly reflecting inherent differences in the impact of turbulence, inflow and/or feedback on gas compared to stars. We suggest how these findings may be taken into account when comparing high and low redshift galaxy samples to infer dynamical evolution. [ABSTRACT FROM AUTHOR]

We present SAMI-H  i , a survey of the atomic hydrogen content of 296 galaxies with integral field spectroscopy available from the SAMI Galaxy Survey. The sample spans nearly 4 dex in stellar mass (⁠|$M_\star = 10^{7.4}-10^{11.1}~ \rm M_\odot$|⁠), redshift z < 0.06, and includes new Arecibo observations of 153 galaxies, for which we release catalogues and H  i spectra. We use these data to compare the rotational velocities obtained from optical and radio observations and to show how systematic differences affect the slope and scatter of the stellar-mass and baryonic Tully–Fisher relations. Specifically, we show that |$\rm H\alpha$| rotational velocities measured in the inner parts of galaxies (1.3 effective radii in this work) systematically underestimate H  i global measurements, with H  i / |$\rm H\alpha$| velocity ratios that increase at low stellar masses, where rotation curves are typically still rising and |$\rm H\alpha$| measurements do not reach their plateau. As a result, the |$\rm H\alpha$| stellar mass Tully–Fisher relation is steeper (when M ⋆ is the independent variable) and has larger scatter than its H  i counterpart. Interestingly, we confirm the presence of a small fraction of low-mass outliers of the |$\rm H\alpha$| relation that are not present when H  i velocity widths are used and are not explained by 'aperture effects'. These appear to be highly disturbed systems for which |$\rm H\alpha$| widths do not provide a reliable estimate of the rotational velocity. Our analysis reaffirms the importance of taking into account differences in velocity definitions as well as tracers used when interpreting offsets from the Tully–Fisher relation, at both low and high redshifts and when comparing with simulations. [ABSTRACT FROM AUTHOR]

The stellar surface density within the inner 1 kpc (Σ1) has become a popular tool for understanding the growth of galaxies and its connection with the quenching of star formation. The emerging picture suggests that building a central dense core is a necessary condition for quenching. However, it is not clear whether changes in Σ1 trace changes in stellar kinematics and the growth of dispersion-dominated bulges. In this paper, we combine imaging from the Sloan Digital Sky Survey with stellar kinematics from the Sydney-AAO Multi-object Integral-field unit and Mapping Nearby Galaxies at Apache Point Observatory surveys to quantify the correlation between Σ1 and the proxy for stellar spin parameter within one effective radius (λre) for 1599 nearby galaxies. We show that, on the star-forming main sequence and at fixed stellar mass, changes in Σ1 are mirrored by changes in λre. While forming stars, main-sequence galaxies remain rotationally-dominated systems, with their Σ1 increasing but their stellar spin staying either constant or slightly increasing. The picture changes below the main sequence, where Σ1 and λre are no longer correlated. Passive systems show a narrower range of Σ1, but a wider range of λre compared to star-forming galaxies. Our results indicate that, from a structural point of view, passive galaxies are a more heterogeneous population than star-forming systems, and may have followed a variety of evolutionary paths. This also suggests that, if dispersion-dominated bulges still grow significantly at z ∼ 0, this generally takes place during, or after, the quenching phase. [ABSTRACT FROM AUTHOR]

Large galaxy samples from multiobject integral field spectroscopic (IFS) surveys now allow for a statistical analysis of the z ∼ 0 galaxy population using resolved kinematic measurements. However, the improvement in number statistics comes at a cost, with multiobject IFS survey more severely impacted by the effect of seeing and lower signal-to-noise ratio. We present an analysis of ∼1800 galaxies from the SAMI Galaxy Survey taking into account these effects. We investigate the spread and overlap in the kinematic distributions of the spin parameter proxy |$\lambda _{R_{\rm {e}}}$| as a function of stellar mass and ellipticity ε e. For SAMI data, the distributions of galaxies identified as regular and non-regular rotators with kinemetry show considerable overlap in the |$\lambda _{R_{\rm {e}}}$| – ε e diagram. In contrast, visually classified galaxies (obvious and non-obvious rotators) are better separated in |$\lambda _{R_{\rm {e}}}$| space, with less overlap of both distributions. Then, we use a Bayesian mixture model to analyse the observed |$\lambda _{R_{\rm {e}}}$| –log (M ⋆/M⊙) distribution. By allowing the mixture probability to vary as a function of mass, we investigate whether the data are best fit with a single kinematic distribution or with two. Below log (M ⋆/M⊙) ∼ 10.5, a single beta distribution is sufficient to fit the complete |$\lambda _{R_{\rm {e}}}$| distribution, whereas a second beta distribution is required above log (M ⋆/M⊙) ∼ 10.5 to account for a population of low- |$\lambda _{R_{\rm {e}}}$| galaxies. While the Bayesian mixture model presents the cleanest separation of the two kinematic populations, we find the unique information provided by visual classification of galaxy kinematic maps should not be disregarded in future studies. Applied to mock-observations from different cosmological simulations, the mixture model also predicts bimodal |$\lambda _{R_{\rm {e}}}$| distributions, albeit with different positions of the |$\lambda _{R_{\rm {e}}}$| peaks. Our analysis validates the conclusions from previous, smaller IFS surveys, but also demonstrates the importance of using selection criteria for identifying different kinematic classes that are dictated by the quality and resolution of the observed or simulated data. [ABSTRACT FROM AUTHOR]