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Recent observations of high-redshift galaxies have revealed starburst galaxies with excessive amounts of nitrogen, well above that expected in standard evolutionary models. The Sunburst Arc galaxy, particularly its young and massive star cluster, represents the closest (⁠|$z=2.4$|⁠) and brightest of these as a strongly lensed object. In this work, we study the chemical history of this star cluster to determine the origin of the elevated gas-phase nitrogen using a chemical evolution model. Our model includes the enrichment of OB stars through stellar winds and core-collapse supernovae assuming that massive stars (⁠|$M\gt 25$|   |$\mathrm{ M}_\odot$|⁠) collapse directly into black holes at the end of their lives. We fit the model parameters to the observed chemical abundances of the Sunburst Arc cluster: O/H, C/O, and N/O. We find that the observed chemical abundances can be explained by models featuring intense star formation events, characterized by rapid gas accretion and high star formation efficiencies. Additionally, the stellar population contributing to the gas enrichment must exclude Wolf–Rayet stars. These conditions might be present in other nitrogen-rich objects as their similar chemical abundances suggest a common history. As previous studies have proposed the presence of Wolf–Rayet stars in the new nitrogen-rich objects, further research using chemodynamic modeling is necessary to ascertain the true nature of these objects. [ABSTRACT FROM AUTHOR]

Most star formation in the local Universe occurs in spiral galaxies, but their origin remains an unanswered question. Various theories have been proposed to explain the development of spiral arms, each predicting different spatial distributions of the interstellar medium. This study maps the star formation rate (SFR) and gas-phase metallicity of nine spiral galaxies with the TYPHOON survey to test two dominating theories: density wave theory and dynamic spiral theory. We discuss the environmental effects on our galaxies, considering reported environments and merging events. Taking advantage of the large field of view covering the entire optical disc, we quantify the fluctuation of SFR and metallicity relative to the azimuthal distance from the spiral arms. We find higher SFR and metallicity in the trailing edge of NGC 1365 (by 0.117 and 0.068 dex, respectively) and NGC 1566 (by 0.119 and 0.037 dex, respectively), which is in line with density wave theory. NGC 2442 shows a different result with higher metallicity (0.093 dex) in the leading edge, possibly attributed to an ongoing merging. The other six spiral galaxies show no statistically significant offset in SFR or metallicity, consistent with dynamic spiral theory. We also compare the behaviour of metallicity inside and outside the corotation radius (CR) of NGC 1365 and NGC 1566. We find comparable metallicity fluctuations near and beyond the CR of NGC 1365, indicating gravitational perturbation. NGC 1566 shows the greatest fluctuation near the CR, in line with the analytic spiral arms. Our work highlights that a combination of mechanisms explains the origin of spiral features in the local Universe. [ABSTRACT FROM AUTHOR]

Spiral arms, as those of our own Milky Way, are some of the most spectacular features in disc galaxies. It has been argued that star formation should proceed more efficiently in spiral arms as a result of gas compression. Yet, observational studies have so far yielded contradictory results. Here, we examine arm/interarm surface density contrasts at ∼100 pc resolution in 28 spiral galaxies from the PHANGS survey. We find that the arm/interarm contrast in stellar mass surface density (Σ⋆) is very modest, typically a few tens of percent. This is much smaller than the contrasts measured for molecular gas (Σmol) or star formation rate (ΣSFR) surface density, which typically reach a factor of ∼2 − 3. However, Σmol and ΣSFR contrasts show a significant correlation with the enhancement in Σ⋆, suggesting that the small stellar contrast largely dictates the stronger accumulation of gas and star formation. All these contrasts increase for grand-design spirals compared to multi-armed and flocculent systems (and for galaxies with high stellar mass). The median star formation efficiency (SFE) of the molecular gas is 16% higher in spiral arms than in interarm regions, with a large scatter, and the contrast increases significantly (median SFE contrast 2.34) for regions of particularly enhanced stellar contrast (Σ⋆ contrast > 1.97). The molecular-to-atomic gas ratio (Σmol/Σatom) is higher in spiral arms, pointing to a transformation of atomic to molecular gas. As a consequence, the total gas contrast (Σmol + Σatom) slightly drops compared to Σmol (median 4% lower, working at ∼kpc resolution), while the SFE contrast increases when we include atomic gas (median 8% higher than for Σmol). The contrasts show important fluctuations with galactocentric radius. We confirm that our results are robust against a number of effects, such as spiral mask width, tracers, resolution, and binning. In conclusion, the boost in the SFE of molecular gas in spiral arms is generally modest or absent, except for locations with exceptionally large stellar contrasts. [ABSTRACT FROM AUTHOR]

Stellar feedback-driven outflows are important regulators of the gas–star formation cycle. However, resolving outflow physics requires high-resolution observations that can only be achieved in very nearby galaxies, making suitable targets rare. We present the first results from the new VLT/MUSE large programme MAUVE (MUSE and ALMA Unveiling the Virgo Environment), which aims to understand the gas–star formation cycle within the context of the Virgo cluster environment. Outflows are a key part of this cycle, and we focus on the peculiar galaxy NGC 4383, which hosts a |$\sim\!\! 6\,$| kpc bipolar outflow fuelled by one of Virgo's most H  i -rich discs. The spectacular MUSE data reveal the clumpy structure and complex kinematics of the ionized gas in this M82-like outflow at 100 pc resolution. Using the ionized gas geometry and kinematics, we constrain the opening half-angle to θ = 25–35°, while the average outflow velocity is |$\sim\!\! 210\ \text{km} \, \text{s}^{-1}$|⁠. The emission line ratios reveal an ionization structure where photoionization is the dominant excitation process. The outflowing gas shows a marginally elevated gas-phase oxygen abundance compared to the disc but lower than the central starburst, highlighting the contribution of mixing between the ejected and entrained gas. Making some assumptions about the outflow geometry, we estimate an integrated mass outflow rate of |$\sim\!\! 1.8~\mathrm{M}_{\odot } \, \mathrm{yr}^{-1}$| and a corresponding mass-loading factor in the range of 1.7–2.3. NGC 4383 is a useful addition to the few nearby examples of well-resolved outflows, and will provide a useful baseline for quantifying the role of outflows within the Virgo cluster. [ABSTRACT FROM AUTHOR]

We present observations of the central 9 kpc of the Antennae merger (NGC 4038/9) at 55 pc resolution in the CO (2–1) line obtained with the Atacama Large Millimeter/submillimeter Array (ALMA). We use a pixel-based analysis to compare the gas properties in the Antennae to those in 70 nearby spiral galaxies from the PHANGS-ALMA survey, as well as the merger and nearest luminous infrared galaxy NGC 3256. Compared to PHANGS-ALMA galaxies at matched spatial resolution, the molecular gas in the Antennae exhibits some of the highest surface densities, velocity dispersions, peak brightness temperatures, and turbulent pressures. However, the virial parameters in the Antennae are consistent with many of the PHANGS-ALMA galaxies. NGC 3256 has similar gas surface densities but higher nuclear velocity dispersions than the Antennae, as well as higher system-wide peak brightness temperatures and virial parameters. NGC 3256 is at a later stage in the merging process than the Antennae, which may result in more intense merger-driven gas flows that could drive up the turbulence in the gas. The high virial parameters in NGC 3256 may indicate that this increased turbulence is suppressing future star formation as NGC 3256 moves out of the starburst phase. In comparison, the relatively normal virial parameters in the Antennae may imply that it is about to undergo a new burst of star formation. [ABSTRACT FROM AUTHOR]

Bars are important drivers of galaxy evolution, influencing many physical processes and properties. Characterizing bars is a difficult task, especially in large-scale surveys. In this work, we propose a novel morphological segmentation technique for determining bar lengths based on deep learning. We develop U-Nets capable of decomposing galaxy images into pixel masks highlighting the regions corresponding to bars and spiral arms. We demonstrate the versatility of this technique through applying our models to galaxy images from two different observational data sets with different source imagery, and to RGB colour and monochromatic galaxy imaging. We apply our models to analyse SDSS and Subaru HyperSuprime Cam imaging of barred galaxies from the NA10 and Sydney AAO Multi-object IFS catalogues in order to determine the dependence of bar length on stellar mass, morphology, redshift and the spin parameter proxy |$\lambda _{R_e}$|⁠. Based on the predicted bar masks, we show that the relative bar scale length varies with morphology, with early type galaxies hosting longer bars. While bars are longer in more massive galaxies in absolute terms, relative to the galaxy disc they are actually shorter. We also find that the normalized bar length decreases with increasing redshift, with bars in early type galaxies exhibiting the strongest rate of decline. We show that it is possible to distinguish spiral arms and bars in monochrome imaging, although for a given galaxy the estimated length in monochrome tends to be longer than in colour imaging. Our morphological segmentation technique can be efficiently applied to study bars in large-scale surveys and even in cosmological simulations. [ABSTRACT FROM AUTHOR]

Galactic fountains driven by star formation result in a variety of kinematic structures such as ionized winds and thick gas discs, both of which manifest as complex emission-line profiles that can be parametrized by multiple Gaussian components. We use integral field spectroscopy from the SAMI Galaxy Survey to spectrally resolve these features, traced by broad |${\rm H}\alpha$| components, and distinguish them from the star-forming (SF) thin disc, traced by narrow components, in 3068 galaxies in the local Universe. Using a matched sample analysis technique, we demonstrate that the presence of complex emission-line profiles in SF galaxies is most strongly correlated with the global star formation rate (SFR) surface density of the host galaxy measured within 1 R e (⁠|$\Sigma _{{\rm SFR},\, R_{\rm e}}$|⁠), even when controlling for both observational biases, including inclination, amplitude-to-noise and angular scale, and sample biases in parameters such as stellar mass and SFR. Leveraging the spatially resolved nature of the data set, we determine that the presence of complex emission-line profiles within individual spaxels is driven not only by the local ΣSFR, but by the |$\Sigma _{{\rm SFR},\, R_{\rm e}}$| of the host galaxy. We also parametrize the clumpiness of the SFR within individual galaxies, and find that |$\Sigma _{{\rm SFR},\, R_{\rm e}}$| is a stronger predictor of the presence of complex emission-line profiles than clumpiness. We conclude that, with a careful treatment of observational effects, it is possible to identify structures traced by complex emission-line profiles, including winds and thick ionized gas discs, at the spatial and spectral resolution of SAMI using the Gaussian decomposition technique. [ABSTRACT FROM AUTHOR]

Connecting the gas in H  ii  regions to the underlying source of the ionizing radiation can help us constrain the physical processes of stellar feedback and how H  ii  regions evolve over time. With PHANGS–MUSE, we detect nearly 24 000 H  ii regions across 19 galaxies and measure the physical properties of the ionized gas (e.g. metallicity, ionization parameter, and density). We use catalogues of multiscale stellar associations from PHANGS– HST to obtain constraints on the age of the ionizing sources. We construct a matched catalogue of 4177 H  ii regions that are clearly linked to a single ionizing association. A weak anticorrelation is observed between the association ages and the |$\mathrm{H}\, \alpha$| equivalent width |$\mathrm{EW}(\mathrm{H}\, \alpha)$|⁠ , the |$\mathrm{H}\, \alpha/\mathrm{FUV}$| flux ratio, and the ionization parameter, log  q. As all three are expected to decrease as the stellar population ages, this could indicate that we observe an evolutionary sequence. This interpretation is further supported by correlations between all three properties. Interpreting these as evolutionary tracers, we find younger nebulae to be more attenuated by dust and closer to giant molecular clouds, in line with recent models of feedback-regulated star formation. We also observe strong correlations with the local metallicity variations and all three proposed age tracers, suggestive of star formation preferentially occurring in locations of locally enhanced metallicity. Overall, |$\mathrm{EW}(\mathrm{H}\, \alpha)$| and log  q show the most consistent trends and appear to be most reliable tracers for the age of an H  ii region. [ABSTRACT FROM AUTHOR]

Star formation, from cold giant molecular clouds to diverse population of stars, is a complex process involving a wide variety of physical processes. In this work, we constrain the link between the gas-star formation cycle and several secular and environmental probe of galaxies. Specifically, we quantify the spatial correlation between molecular gas and star-forming regions for 49 nearby galaxies using the ALMA and narrowband-Hα imaging from the PHANGS survey. At the resolution (150 pc) at which the individual molecular clouds and star-forming regions can be identified, we find that molecular clouds and star-forming regions do not necessarily coexist. The decoupled molecular clouds and star-forming regions are a signature of evolutionary cycling and feedback of the star formation process. Therefore, the impact of galactic-scale conditions and environments must be considered for a complete understanding of how stars form in galaxies and how this process influences the evolution of the host galaxies. [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]

Lenticular (S0) galaxies are galaxies that exhibit a bulge and disc component, yet lack any clear spiral features. With features considered intermediary between spirals and ellipticals, S0s have been proposed to be a transitional morphology, however their exact origin and nature is still debated. In this work, we study the redshift evolution of the S0 fraction out to z ∼ 1 using deep learning to classify F814W (i band) Hubble Space Telescope -Advanced Camera for Surveys (HST -ACS) images of 85 378 galaxies in the Cosmic Evolution Survey (COSMOS). We classify galaxies into four morphological categories: elliptical (E), S0, spiral (Sp), and irregular/miscellaneous (IrrM). Our deep learning models, initially trained to classify Sloan Digital Sky Survey (SDSS) images with known morphologies, have been successfully adapted to classify high-redshift COSMOS images via transfer learning and data augmentation, enabling us to classify S0s with superior accuracy. We find that there is an increase in the fraction of S0 galaxies with decreasing redshift, along with a corresponding reduction in the fraction of spirals. We find a bimodality in the mass distribution of our classified S0s, from which we find two separate S0s populations: high-mass S0s, which are mostly red and quiescent; and low-mass S0s, which are generally bluer and include both passive and star-forming S0s, the latter of which cannot solely be explained via the faded spiral formation pathway. We also find that the S0 fraction in high-mass galaxies begins rising at higher z than in low-mass galaxies, implying that high-mass S0s evolved earlier. [ABSTRACT FROM AUTHOR]

In this work, we present a new catalogue of >40 000 ionised nebulae distributed across the 19 galaxies observed by the PHANGSMUSE survey. The nebulae have been classified using a new model-comparison-based algorithm that exploits the odds ratio principle to assign a probabilistic classification to each nebula in the sample. The resulting catalogue is the largest catalogue containing complete spectral and spatial information for a variety of ionised nebulae available so far in the literature. We developed this new algorithm to address some of the main limitations of the traditional classification criteria, such as their binarity, the sharpness of the involved limits, and the limited amount of data they rely on for the classification. The analysis of the catalogue shows that the algorithm performs well when selecting H II regions. In fact, we can recover their luminosity function, and its properties are in line with what is available in the literature. We also identify a rather significant population of shock-ionised regions (mostly composed of supernova remnants), which is an order of magnitude larger than any other homogeneous catalogue of supernova remnants currently available in the literature. The number of supernova remnants we identify per galaxy is in line with results in our Galaxy and in other very nearby sources. However, limitations in the source detection algorithm result in an incomplete sample of planetary nebulae, even though their classification seems robust. Finally, we demonstrate how applying a correction for the contribution of the diffuse ionised gas to the nebulae's spectra is essential to obtain a robust classification of the objects and how a correct measurement of the extinction using diffuse-ionised-gascorrected line fluxes prompts the use of a higher theoretical Ha/Hß ratio (3.03) than what is commonly used when recovering the E(B - V) via the Balmer decrement technique in massive star-forming galaxies. [ABSTRACT FROM AUTHOR]

A long-standing problem when deriving the physical properties of stellar populations is the degeneracy between age, reddening, and metallicity. When a single metallicity is used for all the star clusters in a galaxy, this degeneracy can result in 'catastrophic' errors for old globular clusters. Typically, approximately 10–20 per cent of all clusters detected in spiral galaxies can have ages that are incorrect by a factor of 10 or more. In this paper, we present a pilot study for four galaxies (NGC 628, NGC 1433, NGC 1365, and NGC 3351) from the PHANGS-HST survey. We describe methods to correct the age-dating for old globular clusters, by first identifying candidates using their colours, and then reassigning ages and reddening based on a lower metallicity solution. We find that young 'Interlopers' can be identified from their Hα flux. CO (2-1) intensity or the presence of dust can also be used, but our tests show that they do not work as well. Improvements in the success fraction are possible at the ≈15 per cent level (reducing the fraction of catastrophic age-estimates from between 13 and 21 per cent, to between 3  and 8 per cent). A large fraction of the incorrectly age-dated globular clusters are systematically given ages around 100 Myr, polluting the younger populations as well. Incorrectly age-dated globular clusters significantly impact the observed cluster age distribution in NGC 628, which affects the physical interpretation of cluster disruption in this galaxy. For NGC 1365, we also demonstrate how to fix a second major age-dating problem, where very dusty young clusters with E (B − V) > 1.5 mag are assigned old, globular-cluster like ages. Finally, we note the discovery of a dense population of ≈300 Myr clusters around the central region of NGC 1365 and discuss how this results naturally from the dynamics in a barred galaxy. [ABSTRACT FROM AUTHOR]

Observations of the neutral atomic hydrogen (⁠|${\rm H\, {\small I}}$|⁠) gas in galaxies are predominantly spatially unresolved, in the form of a global |${\rm H\, {\small I}}$| spectral line. There has been substantial work on quantifying asymmetry in global |${\rm H\, {\small I}}$| spectra ('global |${\rm H\, {\small I}}$| asymmetry'), but due to being spatially unresolved, it remains unknown what physical regions of galaxies the asymmetry traces, and whether the other gas phases are affected. Using optical integral field spectrograph (IFS) observations from the Sydney AAO Multi-object IFS (SAMI) survey for which global |${\rm H\, {\small I}}$| spectra are also available (SAMI- |${\rm H\, {\small I}}$|⁠), we study the connection between asymmetry in galaxies' ionized and neutral gas reservoirs to test if and how they can help us better understand the origin of global |${\rm H\, {\small I}}$| asymmetry. We reconstruct the global Hα spectral line from the IFS observations and find that while some global Hα asymmetries can arise from disturbed ionized gas kinematics, the majority of asymmetric cases are driven by the distribution of Hα-emitting gas. When compared to the |${\rm H\, {\small I}}$|⁠ , we find no evidence for a relationship between the global Hα and |${\rm H\, {\small I}}$| asymmetry. Further, a visual inspection reveals that cases where galaxies have qualitatively similar Hα and |${\rm H\, {\small I}}$| spectral profiles can be spurious, with the similarity originating from an irregular 2D Hα flux distribution. Our results highlight that comparisons between global Hα and |${\rm H\, {\small I}}$| asymmetry are not straightforward, and that many global |${\rm H\, {\small I}}$| asymmetries trace disturbances that do not significantly impact the central regions of galaxies. [ABSTRACT FROM AUTHOR]

We study environmental quenching using the spatial distribution of current star formation and stellar population ages with the full SAMI Galaxy Survey. By using a star formation concentration index [ C -index, defined as log10(r 50, H α/ r 50, cont)], we separate our sample into regular galaxies (C -index ≥−0.2) and galaxies with centrally concentrated star formation (SF-concentrated; C -index <−0.2). Concentrated star formation is a potential indicator of galaxies currently undergoing 'outside-in' quenching. Our environments cover ungrouped galaxies, low-mass groups (M 200 ≤ 1012.5M⊙), high-mass groups (M 200 in the range 1012.5–14 M⊙) and clusters (M 200 > 1014M⊙). We find the fraction of SF-concentrated galaxies increases as halo mass increases by 9 ± 2 per cent, 8 ± 3 per cent, 19 ± 4 per cent, and 29 ± 4 per cent for ungrouped galaxies, low-mass groups, high-mass groups, and clusters, respectively. We interpret these results as evidence for 'outside-in' quenching in groups and clusters. To investigate the quenching time-scale in SF-concentrated galaxies, we calculate light-weighted age (Age L) and mass-weighted age (Age M) using full spectral fitting, as well as the D n4000 and H δA indices. We assume that the average galaxy age radial profile before entering a group or cluster is similar to ungrouped regular galaxies. At large radius (1–2 R e), SF-concentrated galaxies in high-mass groups have older ages than ungrouped regular galaxies with an age difference of 1.83 ± 0.38 Gyr for Age L and 1.34 ± 0.56 Gyr for Age M. This suggests that while 'outside-in' quenching can be effective in groups, the process will not quickly quench the entire galaxy. In contrast, the ages at 1–2 R e of cluster SF-concentrated galaxies and ungrouped regular galaxies are consistent (difference of 0.19 ± 0.21 Gyr for Age L, 0.40 ± 0.61 Gyr for Age M), suggesting the quenching process must be rapid. [ABSTRACT FROM AUTHOR]

The processes of star formation and feedback, regulating the cycle of matter between gas and stars on the scales of giant molecular clouds (GMCs; ∼100 pc), play a major role in governing galaxy evolution. Measuring the time-scales of GMC evolution is important to identify and characterize the specific physical mechanisms that drive this transition. By applying a robust statistical method to high-resolution CO and narrow-band H α imaging from the PHANGS survey, we systematically measure the evolutionary timeline from molecular clouds to exposed young stellar regions on GMC scales, across the discs of an unprecedented sample of 54 star-forming main-sequence galaxies (excluding their unresolved centres). We find that clouds live for about 1−3 GMC turbulence crossing times (5−30 Myr) and are efficiently dispersed by stellar feedback within 1−5 Myr once the star-forming region becomes partially exposed, resulting in integrated star formation efficiencies of 1−8 per cent. These ranges reflect physical galaxy-to-galaxy variation. In order to evaluate whether galactic environment influences GMC evolution, we correlate our measurements with average properties of the GMCs and their local galactic environment. We find several strong correlations that can be physically understood, revealing a quantitative link between galactic-scale environmental properties and the small-scale GMC evolution. Notably, the measured CO-visible cloud lifetimes become shorter with decreasing galaxy mass, mostly due to the increasing presence of CO-dark molecular gas in such environment. Our results represent a first step towards a comprehensive picture of cloud assembly and dispersal, which requires further extension and refinement with tracers of the atomic gas, dust, and deeply embedded stars. [ABSTRACT FROM AUTHOR]

Using data from the SAMI Galaxy Survey, we investigate the correlation between the projected stellar kinematic spin vector of 1397 SAMI galaxies and the line-of-sight motion of their neighbouring galaxies. We calculate the luminosity-weighted mean velocity difference between SAMI galaxies and their neighbours in the direction perpendicular to the SAMI galaxies' angular momentum axes. The luminosity-weighted mean velocity offset between SAMI galaxies and neighbours, which indicates the signal of coherence between the rotation of the SAMI galaxies and the motion of neighbours, is 9.0 ± 5.4 km s−1 (1.7σ) for neighbours within 1 Mpc. In a large-scale analysis, we find that the average velocity offsets increase for neighbours out to 2 Mpc. However, the velocities are consistent with zero or negative for neighbours outside 3 Mpc. The negative signals for neighbours at a distance around 10 Mpc are also significant at the ∼2σ level, which indicate that the positive signals within 2 Mpc might come from the variance of large-scale structure. We also calculate average velocities of different subsamples, including galaxies in different regions of the sky, galaxies with different stellar masses, galaxy type, λRe, and inclination. Although subsamples of low-mass, high-mass, early-type, and low-spin galaxies show the 2–3σ signal of coherence for the neighbours within 2 Mpc, the results for different inclination subsamples and large-scale results suggest that the ∼2σ signals might result from coincidental scatter or variance of large-scale structure. Overall, the modest evidence of coherence signals for neighbouring galaxies within 2 Mpc needs to be confirmed by larger samples of observations and simulation studies. [ABSTRACT FROM AUTHOR]

We explore a sample of 1492 galaxies with measurements of the mean stellar population properties and the spin parameter proxy, |$\lambda _{R_{\rm {e}}}$|⁠ , drawn from the SAMI Galaxy Survey. We fit a global |$[\alpha /\rm {Fe}]$| –σ relation, finding that |${[\alpha /\rm {Fe}]}=(0.395\pm 0.010)\rm {log}_{10}(\sigma)-(0.627\pm 0.002)$|⁠. We observe an anti-correlation between the residuals |$\Delta [\alpha /\rm {Fe}]$| and the inclination-corrected |$\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}$|⁠ , which can be expressed as |${\Delta [\alpha /\rm {Fe}]}=(-0.057\pm 0.008){\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}+(0.020\pm 0.003)$|⁠. The anti-correlation appears to be driven by star-forming galaxies, with a gradient of |${\Delta [\alpha /\rm {Fe}]}\sim (-0.121\pm 0.015){\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}$|⁠ , although a weak relationship persists for the subsample of galaxies for which star formation has been quenched. We take this to be confirmation that disc-dominated galaxies have an extended duration of star formation. At a reference velocity dispersion of 200 km s−1, we estimate an increase in half-mass formation time from ∼0.5 Gyr to ∼1.2 Gyr from low- to high- |$\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}$| galaxies. Slow rotators do not appear to fit these trends. Their residual α-enhancement is indistinguishable from other galaxies with |${\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}\lessapprox 0.4$|⁠ , despite being both larger and more massive. This result shows that galaxies with |${\lambda _{\, R_{\rm {e}}}^{\rm {\, eo}}}\lessapprox 0.4$| experience a similar range of star formation histories, despite their different physical structure and angular momentum. [ABSTRACT FROM AUTHOR]

We investigate the mean locally measured velocity dispersions of ionized gas (σgas) and stars (σ*) for 1090 galaxies with stellar masses |$\log \, (M_{\!\ast }/M_{\odot }) \ge 9.5$| from the SAMI Galaxy Survey. For star-forming galaxies, σ* tends to be larger than σgas, suggesting that stars are in general dynamically hotter than the ionized gas (asymmetric drift). The difference between σgas and σ* (Δσ) correlates with various galaxy properties. We establish that the strongest correlation of Δσ is with beam smearing, which inflates σgas more than σ*, introducing a dependence of Δσ on both the effective radius relative to the point spread function and velocity gradients. The second strongest correlation is with the contribution of active galactic nuclei (AGN) (or evolved stars) to the ionized gas emission, implying that the gas velocity dispersion is strongly affected by the power source. In contrast, using the velocity dispersion measured from integrated spectra (σap) results in less correlation between the aperture-based Δσ (Δσap) and the power source. This suggests that the AGN (or old stars) dynamically heat the gas without causing significant deviations from dynamical equilibrium. Although the variation of Δσap is much smaller than that of Δσ, a correlation between Δσap and gas velocity gradient is still detected, implying that there is a small bias in dynamical masses derived from stellar and ionized gas velocity dispersions. [ABSTRACT FROM AUTHOR]

We study the morphologies of 3964 galaxies and their progenitors with M ⋆ > 1010M⊙ in the reference eagle hydrodynamical simulation from redshifts z = 1 to 0, concentrating on the redshift evolution of the bar fraction. We apply two convolutional neural networks (CNNs) to classify 35 082 synthetic g- band images across 10 snapshots in redshift. We identify galaxies as either barred or unbarred, while also classifying each sample into one of four morphological types: elliptical (E), lenticular (S0), spiral (Sp), and irregular/miscellaneous (IrrM). We find that the bar fraction is roughly constant between z = 0.0 and 0.5 (32–33 per cent), before exhibiting a general decline to 26 per cent out to z = 1. The bar fraction is highest in spiral galaxies, from 49 per cent at z = 0 to 39 per cent at z = 1. The bar fraction in S0s is lower, ranging from 22 to 18 per cent, with similar values for the miscellaneous category. Under 5 per cent of ellipticals were classified as barred. We find that the bar fraction is highest in low-mass galaxies (M ⋆ ≤ 1010.5M⊙). Through tracking the evolution of galaxies across each snapshot, we find that some barred galaxies undergo episodes of bar creation, destruction and regeneration, with a mean bar lifetime of 2.24 Gyr. We further find that incidences of bar destruction are more commonly linked to major merging, while minor merging and accretion is linked to both bar creation and destruction. [ABSTRACT FROM AUTHOR]

We use an unprecedented sample of about 23 000 H II regions detected at an average physical resolution of 67 pc in the PHANGS–MUSE sample to study the extragalactic H II region Hα luminosity function (LF). Our observations probe the star-forming disk of 19 nearby spiral galaxies with low inclination and located close to the star formation main sequence at z = 0. The mean LF slope, α, in our sample is =1.73 with a σ of 0.15. We find that α decreases with the galaxy's star formation rate surface density, ΣSFR, and argue that this is driven by an enhanced clustering of young stars at high gas surface densities. Looking at the H II regions within single galaxies, we find that no significant variations occur between the LF of the inner and outer part of the star-forming disk, whereas the LF in the spiral arm areas is shallower than in the inter-arm areas for six out of the 13 galaxies with clearly visible spiral arms. We attribute these variations to the spiral arms increasing the molecular clouds' arm–inter-arm mass contrast and find suggestive evidence that they are more evident for galaxies with stronger spiral arms. Furthermore, we find systematic variations in α between samples of H II regions with a high and low ionization parameter, q, and argue that they are driven by the aging of H II regions. [ABSTRACT FROM AUTHOR]

We present a new set of index-based measurements of [α/Fe] for a sample of 2093 galaxies in the SAMI Galaxy Survey. Following earlier work, we fit a global relation between [α/Fe] and the galaxy velocity dispersion σ for red sequence galaxies, |$[\alpha /\text{Fe}]=(0.378\pm 0.009)\rm {log}_{10}\left(\sigma /100\right)+(0.155\pm 0.003)$|⁠. We observe a correlation between the residuals and the local environmental surface density, whereas no such relation exists for blue cloud galaxies. In the full sample, we find that elliptical galaxies in high-density environments are α-enhanced by up to 0.057 ± 0.014 dex at velocity dispersions σ < 100 km s−1, compared with those in low-density environments. This α-enhancement is morphology-dependent, with the offset decreasing along the Hubble sequence towards spirals, which have an offset of 0.019 ± 0.014 dex. At low velocity dispersion and controlling for morphology, we estimate that star formation in high-density environments is truncated ∼1 Gyr earlier than in low-density environments. For elliptical galaxies only, we find support for a parabolic relationship between [α/Fe] and σ, with an environmental α-enhancement of at least 0.03 dex. This suggests strong contributions from both environment and mass-based quenching mechanisms. However, there is no evidence for this behaviour in later morphological types. [ABSTRACT FROM AUTHOR]

Understanding the spatial distribution of metals within galaxies allows us to study the processes of chemical enrichment and mixing in the interstellar medium. In this work, we map the 2D distribution of metals using a Gaussian Process Regression (GPR) for 19 star-forming galaxies observed with the Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT–MUSE) as a part of the PHANGS–MUSE survey. We find that 12 of our 19 galaxies show significant 2D metallicity variation. Those without significant variations typically have fewer metallicity measurements, indicating this is due to the dearth of |${\rm H\, {\small II}}$| regions in these galaxies, rather than a lack of higher-order variation. After subtracting a linear radial gradient, we see no enrichment in the spiral arms versus the disc. We measure the 50 per cent correlation scale from the two-point correlation function of these radially subtracted maps, finding it to typically be an order of magnitude smaller than the fitted GPR kernel scale length. We study the dependence of the two-point correlation scale length with a number of global galaxy properties. We find no relationship between the 50 per cent correlation scale and the overall gas turbulence, in tension with existing theoretical models. We also find more actively star-forming galaxies, and earlier type galaxies have a larger 50 per cent correlation scale. The size and stellar mass surface density do not appear to correlate with the 50 per cent correlation scale, indicating that perhaps the evolutionary state of the galaxy and its current star formation activity is the strongest indicator of the homogeneity of the metal distribution. [ABSTRACT FROM AUTHOR]

It is a major open question which physical processes stop gas accretion on to giant molecular clouds (GMCs) and limit the efficiency at which gas is converted into stars. While feedback from supernova explosions has been the popular feedback mechanism included in simulations of galaxy formation and evolution, 'early' feedback mechanisms such as stellar winds, photoionization, and radiation pressure are expected to play an important role in dispersing the gas after the onset of star formation. These feedback processes typically take place on small scales (∼10–100 pc) and their effects have therefore been difficult to constrain in environments other than the Milky Way. We apply a novel statistical method to ∼1 arcsec resolution maps of CO and H α across a sample of nine nearby galaxies, to measure the time over which GMCs are dispersed by feedback from young, high-mass stars, as a function of the galactic environment. We find that GMCs are typically dispersed within ∼3 Myr on average after the emergence of unembedded high-mass stars, with variations within galaxies associated with morphological features rather than radial trends. Comparison with analytical predictions demonstrates that, independently of the environment, early feedback mechanisms (particularly photoionization and stellar winds) play a crucial role in dispersing GMCs and limiting their star formation efficiency in nearby galaxies. Finally, we show that the efficiency at which the energy injected by these early feedback mechanisms couples with the parent GMC is relatively low (a few tens of per cent), such that the vast majority of momentum and energy emitted by the young stellar populations escapes the parent GMC. [ABSTRACT FROM AUTHOR]

The kinematic morphology–density relation of galaxies is normally attributed to a changing distribution of galaxy stellar masses with the local environment. However, earlier studies were largely focused on slow rotators; the dynamical properties of the overall population in relation to environment have received less attention. We use the SAMI Galaxy Survey to investigate the dynamical properties of ∼1800 early and late-type galaxies with log (M ⋆/ M ⊙) > 9.5 as a function of mean environmental overdensity (Σ5) and their rank within a group or cluster. By classifying galaxies into fast and slow rotators, at fixed stellar mass above log (M ⋆/ M ⊙) > 10.5, we detect a higher fraction (∼3.4σ) of slow rotators for group and cluster centrals and satellites as compared to isolated-central galaxies. We find similar results when using Σ5 as a tracer for environment. Focusing on the fast-rotator population, we also detect a significant correlation between galaxy kinematics and their stellar mass as well as the environment they are in. Specifically, by using inclination-corrected or intrinsic |$\lambda _{R_{\rm {e}}}$| values, we find that, at fixed mass, satellite galaxies on average have the lowest |$\lambda _{\, R_{\rm {e}},\rm {intr}}$|⁠ , isolated-central galaxies have the highest |$\lambda _{\, R_{\rm {e}},\rm {intr}}$|⁠ , and group and cluster centrals lie in between. Similarly, galaxies in high-density environments have lower mean |$\lambda _{\, R_{\rm {e}},\rm {intr}}$| values as compared to galaxies at low environmental density. However, at fixed Σ5, the mean |$\lambda _{\, R_{\rm {e}},\rm {intr}}$| differences for low and high-mass galaxies are of similar magnitude as when varying Σ5 (⁠|$\Delta \lambda _{\, R_{\rm {e}},\rm {intr}} \sim 0.05$|⁠ , with σrandom = 0.025, and σ syst < 0.03). Our results demonstrate that after stellar mass, environment plays a significant role in the creation of slow rotators, while for fast rotators we also detect an independent, albeit smaller, impact of mass and environment on their kinematic properties. [ABSTRACT FROM AUTHOR]

Classifying the morphologies of galaxies is an important step in understanding their physical properties and evolutionary histories. The advent of large-scale surveys has hastened the need to develop techniques for automated morphological classification. We train and test several convolutional neural network (CNN) architectures to classify the morphologies of galaxies in both a 3-class (elliptical, lenticular, and spiral) and a 4-class (+irregular/miscellaneous) schema with a data set of 14 034 visually classified SDSS images. We develop a new CNN architecture that outperforms existing models in both 3-way and 4-way classifications, with overall classification accuracies of 83 and 81 per cent, respectively. We also compare the accuracies of 2-way/binary classifications between all four classes, showing that ellipticals and spirals are most easily distinguished (>98 per cent accuracy), while spirals and irregulars are hardest to differentiate (78 per cent accuracy). Through an analysis of all classified samples, we find tentative evidence that misclassifications are physically meaningful, with lenticulars misclassified as ellipticals tending to be more massive, among other trends. We further combine our binary CNN classifiers to perform a hierarchical classification of samples, obtaining comparable accuracies (81 per cent) to the direct 3-class CNN, but considerably worse accuracies in the 4-way case (65 per cent). As an additional verification, we apply our networks to a small sample of Galaxy Zoo images, obtaining accuracies of 92, 82, and 77 per cent for the binary, 3-way, and 4-way classifications, respectively. [ABSTRACT FROM AUTHOR]

We have entered a new era where integral-field spectroscopic surveys of galaxies are sufficiently large to adequately sample large-scale structure over a cosmologically significant volume. This was the primary design goal of the SAMI Galaxy Survey. Here, in Data Release 3, we release data for the full sample of 3068 unique galaxies observed. This includes the SAMI cluster sample of 888 unique galaxies for the first time. For each galaxy, there are two primary spectral cubes covering the blue (370–570 nm) and red (630–740 nm) optical wavelength ranges at spectral resolving power of R = 1808 and 4304, respectively. For each primary cube, we also provide three spatially binned spectral cubes and a set of standardized aperture spectra. For each galaxy, we include complete 2D maps from parametrized fitting to the emission-line and absorption-line spectral data. These maps provide information on the gas ionization and kinematics, stellar kinematics and populations, and more. All data are available online through Australian Astronomical Optics Data Central. [ABSTRACT FROM AUTHOR]

Feedback from massive stars plays a key role in molecular cloud evolution. After the onset of star formation, the young stellar population is exposed by photoionization, winds, supernovae, and radiation pressure from massive stars. Recent observations of nearby galaxies have provided the evolutionary timeline between molecular clouds and exposed young stars, but the duration of the embedded phase of massive star formation is still ill-constrained. We measure how long massive stellar populations remain embedded within their natal cloud, by applying a statistical method to six nearby galaxies at |$20{-}100~\mbox{${\rm ~pc}$}$| resolution, using CO, Spitzer 24 |$\rm \, \mu m$|⁠ , and H α emission as tracers of molecular clouds, embedded star formation, and exposed star formation, respectively. We find that the embedded phase (with CO and 24 |$\rm \, \mu m$|  emission) lasts for 2−7 Myr and constitutes |$17{-}47{{\ \rm per\ cent}}$| of the cloud lifetime. During approximately the first half of this phase, the region is invisible in H α, making it heavily obscured. For the second half of this phase, the region also emits in H α and is partially exposed. Once the cloud has been dispersed by feedback, 24 |$\rm \, \mu m$| emission no longer traces ongoing star formation, but remains detectable for another 2−9 Myr through the emission from ambient CO-dark gas, tracing star formation that recently ended. The short duration of massive star formation suggests that pre-supernova feedback (photoionization and winds) is important in disrupting molecular clouds. The measured time-scales do not show significant correlations with environmental properties (e.g. metallicity). Future JWST observations will enable these measurements routinely across the nearby galaxy population. [ABSTRACT FROM AUTHOR]

The [C  ii ] deficit, which describes the observed decrease in the ratio of [C  ii ] 158  μ m emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [C  ii ] detections from across the observable universe. In an attempt to further decode the cause of the [C  ii ] deficit, the [C  ii ] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [C  ii ] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [C  ii ] line in H  ii regions plays a significant role in the deficit observed in our sample. [ABSTRACT FROM AUTHOR]

We measure the gas-phase metallicity gradients of 248 galaxies selected from Data Release 2 of the SAMI Galaxy Survey. We demonstrate that there are large systematic discrepancies between the metallicity gradients derived using common strong emission line metallicity diagnostics. We determine which pairs of diagnostics have Spearman's rank coefficients greater than 0.6 and provide linear conversions to allow the accurate comparison of metallicity gradients derived using different strong emission line diagnostics. For galaxies within the mass range 8.5 < log (M /M⊙) < 11.0, we find discrepancies of up to 0.11 dex/ R e between seven popular diagnostics in the metallicity gradient–mass relation. We find a suggestion of a break in the metallicity gradient–mass relation, where the slope shifts from negative to positive, occurs between 9.5 < log (M /M⊙) < 10.5 for the seven chosen diagnostics. Applying our conversions to the metallicity gradient–mass relation, we reduce the maximum dispersion from 0.11 dex/ R e to 0.02 dex/ R e. These conversions provide the most accurate method of converting metallicity gradients when key emission lines are unavailable. We find that diagnostics that share common sets of emission line ratios agree best, and that diagnostics calibrated through the electron temperature provide more consistent results compared to those calibrated through photoionization models. [ABSTRACT FROM AUTHOR]

The sensitivity and angular resolution of photometric surveys executed by the Hubble Space Telescope (HST) enable studies of individual star clusters in galaxies out to a few tens of megaparsecs. The fitting of spectral energy distributions (SEDs) of star clusters is essential for measuring their physical properties and studying their evolution. We report on the use of the publicly available Code Investigating GALaxy Emission (cigale) SED fitting package to derive ages, stellar masses, and reddenings for star clusters identified in the Physics at High Angular resolution in Nearby GalaxieS– HST (PHANGS– HST) survey. Using samples of star clusters in the galaxy NGC 3351, we present results of benchmark analyses performed to validate the code and a comparison to SED fitting results from the Legacy Extragalactic Ultraviolet Survey. We consider procedures for the PHANGS– HST SED fitting pipeline, e.g. the choice of single stellar population models, the treatment of nebular emission and dust, and the use of fluxes versus magnitudes for the SED fitting. We report on the properties of clusters in NGC 3351 and find, on average, the clusters residing in the inner star-forming ring of NGC 3351 are young (<10 Myr) and massive (105 M⊙) while clusters in the stellar bulge are significantly older. Cluster mass function fits yield β values around −2, consistent with prior results with a tendency to be shallower at the youngest ages. Finally, we explore a Bayesian analysis with additional physically motivated priors for the distribution of ages and masses and analyse the resulting cluster distributions. [ABSTRACT FROM AUTHOR]

Local examples of jet-induced star formation lend valuable insight into its significance in galaxy evolution and can provide important observational constraints for theoretical models of positive feedback. Using optical integral field spectroscopy, we present an analysis of the ISM conditions in Minkowski's object (z = 0.0189), a peculiar star-forming dwarf galaxy located in the path of a radio jet from the galaxy NGC 541. Full spectral fitting with ppxf indicates that Minkowski's object primarily consists of a young stellar population |$\sim \! 10\, \rm Myr$| old, confirming that the bulk of the object's stellar mass formed during a recent jet interaction. Minkowski's object exhibits line ratios largely consistent with star formation, although there is evidence for a low level (⁠|$\lesssim \! 15 \, \rm per \, cent$|⁠) of contamination from a non-stellar ionizing source. Strong-line diagnostics reveal a significant variation in the gas-phase metallicity within the object, with |$\log \left(\rm O / H \right) + 12$| varying by |$\sim \! 0.5\, \rm dex$|⁠ , which cannot be explained by in-situ star formation, an enriched outflow from the jet, or enrichment of gas in the stellar bridge between NGC 541 and NGC 545/547. We hypothesize that Minkowski's object either (i) was formed as a result of jet-induced star formation in pre-existing gas clumps in the stellar bridge, or (ii) is a gas-rich dwarf galaxy that is experiencing an elevation in its star formation rate due to a jet interaction, and will eventually redden and fade, becoming an ultradiffuse galaxy as it is processed by the cluster. [ABSTRACT FROM AUTHOR]

The spatial distribution of metals reflects, and can be used to constrain, the processes of chemical enrichment and mixing. Using PHANGS-MUSE optical integral field spectroscopy, we measure the gas-phase oxygen abundances (metallicities) across 7138 H  ii regions in a sample of eight nearby disc galaxies. In Paper I, we measure and report linear radial gradients in the metallicities of each galaxy, and qualitatively searched for azimuthal abundance variations. Here, we examine the 2D variation in abundances once the radial gradient is subtracted, Δ(O/H), in order to quantify the homogeneity of the metal distribution and to measure the mixing scale over which H  ii region metallicities are correlated. We observe low (0.03–0.05 dex) scatter in Δ(O/H) globally in all galaxies, with significantly lower (0.02–0.03 dex) scatter on small (<600 pc) spatial scales. This is consistent with the measurement uncertainties, and implies the 2D metallicity distribution is highly correlated on scales of ≲600 pc. We compute the two-point correlation function for metals in the disc in order to quantify the scale lengths associated with the observed homogeneity. This mixing scale is observed to correlate better with the local gas velocity dispersion (of both cold and ionized gas) than with the star formation rate. Selecting only H  ii regions with enhanced abundances relative to a linear radial gradient, we do not observe increased homogeneity on small scales. This suggests that the observed homogeneity is driven by the mixing introducing material from large scales rather than by pollution from recent and on-going star formation. [ABSTRACT FROM AUTHOR]

The Study of H α from Dwarf Emissions (SHαDE) is a high spectral resolution (R = 13 500) H α integral field survey of 69 dwarf galaxies with stellar masses 106 < M ⋆ < 109 M⊙. The survey used FLAMES on the ESO Very Large Telescope. SHαDE is designed to study the kinematics and stellar populations of dwarf galaxies using consistent methods applied to massive galaxies and at matching level of detail, connecting these mass ranges in an unbiased way. In this paper, we set out the science goals of SHαDE, describe the sample properties, outline the data reduction, and analysis processes. We investigate the log  M ⋆–log  S 0.5 mass–kinematics scaling relation, which has previously shown potential for combining galaxies of all morphologies in a single scaling relation. We extend the scaling relation from massive galaxies to dwarf galaxies, demonstrating this relation is linear down to a stellar mass of M ⋆ ∼ 108.6 M⊙. Below this limit, the kinematics of galaxies inside one effective radius appears to be dominated by the internal velocity dispersion limit of the H α-emitting gas, giving a bend in the log  M ⋆–log  S 0.5 relation. Replacing stellar mass with total baryonic mass using gas mass estimate reduces the severity but does not remove the linearity limit of the scaling relation. An extrapolation to estimate the galaxies' dark matter halo masses, yields a log  M h–log  S 0.5 scaling relation that is free of any bend, has reduced curvature over the whole mass range, and brings galaxies of all masses and morphologies on to the virial relation. [ABSTRACT FROM AUTHOR]

We investigate the stellar kinematics of the bulge and disk components in 826 galaxies with a wide range of morphology from the Sydney-AAO Multi-object Integral-field spectroscopy Galaxy Survey. The spatially resolved rotation velocity (V) and velocity dispersion (σ) of bulge and disk components have been simultaneously estimated using the penalized pixel fitting (ppxf) method with photometrically defined weights for the two components. We introduce a new subroutine of ppxf for dealing with degeneracy in the solutions. We show that the V and σ distributions in each galaxy can be reconstructed using the kinematics and weights of the bulge and disk components. The combination of two distinct components provides a consistent description of the major kinematic features of galaxies over a wide range of morphological types. We present Tully–Fisher and Faber–Jackson relations showing that the galaxy stellar mass scales with both V and σ for both components of all galaxy types. We find a tight Faber–Jackson relation even for the disk component. We show that the bulge and disk components are kinematically distinct: (1) the two components show scaling relations with similar slopes, but different intercepts; (2) the spin parameter λ R indicates bulges are pressure-dominated systems and disks are supported by rotation; and (3) the bulge and disk components have, respectively, low and high values in intrinsic ellipticity. Our findings suggest that the relative contributions of the two components explain, at least to first order, the complex kinematic behaviour of galaxies. [ABSTRACT FROM AUTHOR]

We infer the intrinsic ionized gas kinematics for 383 star-forming galaxies across a range of integrated star formation rates (SFR ∈ [10−3, 102] M⊙ yr−1) at z ≲ 0.1 using a consistent 3D forward-modelling technique. The total sample is a combination of galaxies from the Sydney-AAO Multiobject Integral field Spectrograph (SAMI) Galaxy survey and DYnamics of Newly Assembled Massive Objects survey. For typical low- z galaxies taken from the SAMI Galaxy Survey, we find the vertical velocity dispersion (σ v,z ) to be positively correlated with measures of SFR, stellar mass, H  i gas mass, and rotational velocity. The greatest correlation is with SFR surface density (ΣSFR). Using the total sample, we find σ v,z increases slowly as a function of integrated SFR in the range SFR ∈ [10−3, 1]  M⊙ yr−1 from 17 ± 3 to 24 ± 5 km s−1 followed by a steeper increase up to σ v,z ∼80 km s−1 for SFR ≳ 1 M⊙ yr−1. This is consistent with recent theoretical models that suggest a σ v,z floor driven by star formation feedback processes with an upturn in σ v,z at higher SFR driven by gravitational transport of gas through the disc. [ABSTRACT FROM AUTHOR]

It remains a major challenge to derive a theory of cloud-scale (⁠|$\lesssim100$|  pc) star formation and feedback, describing how galaxies convert gas into stars as a function of the galactic environment. Progress has been hampered by a lack of robust empirical constraints on the giant molecular cloud (GMC) lifecycle. We address this problem by systematically applying a new statistical method for measuring the evolutionary timeline of the GMC lifecycle, star formation, and feedback to a sample of nine nearby disc galaxies, observed as part of the PHANGS-ALMA survey. We measure the spatially resolved (∼100 pc) CO-to-H α flux ratio and find a universal de-correlation between molecular gas and young stars on GMC scales, allowing us to quantify the underlying evolutionary timeline. GMC lifetimes are short, typically |$10\!-\!30\,{\rm Myr}$|⁠ , and exhibit environmental variation, between and within galaxies. At kpc-scale molecular gas surface densities |$\Sigma _{\rm H_2}\ge 8\,\rm {M_\odot}\,{{\rm pc}}^{-2}$|⁠ , the GMC lifetime correlates with time-scales for galactic dynamical processes, whereas at |$\Sigma _{\rm H_2}\le 8\,\rm {M_\odot}\,{{\rm pc}}^{-2}$| GMCs decouple from galactic dynamics and live for an internal dynamical time-scale. After a long inert phase without massive star formation traced by H α (75–90 per cent of the cloud lifetime), GMCs disperse within just |$1\!-\!5\,{\rm Myr}$| once massive stars emerge. The dispersal is most likely due to early stellar feedback, causing GMCs to achieve integrated star formation efficiencies of 4–10 per cent. These results show that galactic star formation is governed by cloud-scale, environmentally dependent, dynamical processes driving rapid evolutionary cycling. GMCs and H  ii regions are the fundamental units undergoing these lifecycles, with mean separations of |$100\!-\!300\,{{\rm pc}}$| in star-forming discs. Future work should characterize the multiscale physics and mass flows driving these lifecycles. [ABSTRACT FROM AUTHOR]

We study the physical mechanisms that cause the offset between low-redshift and high-redshift galaxies on the [O  iii ] λ5007/H β versus [N  ii ] λ6584/H α 'Baldwin, Phillips & Terlevich' (BPT) diagram using a sample of local analogues of high-redshift galaxies. These high-redshift analogue galaxies are selected from the Sloan Digital Sky Survey. Located in the same region on the BPT diagram as the ultraviolet selected galaxies at z ∼ 2, these high-redshift analogue galaxies provide an ideal local benchmark to study the offset between the local and high-redshift galaxies on the BPT diagram. We compare the nitrogen-to-oxygen ratio (N/O), the shape of the ionizing radiation field, and ionization parameters between the high-redshift analogues and a sample of local reference galaxies. The higher ionization parameter in the high-redshift analogues is the dominant physical mechanism driving the BPT offset from low- to high-redshift, particularly at high [N  ii ] λ6584/H α. Furthermore, the N/O ratio enhancement also plays a minor role to cause the BPT offset. However, the shape of the ionizing radiation field is unlikely to cause the BPT offset because the high-redshift analogues have a similar hard ionizing radiation field as local reference galaxies. This hard radiation field cannot be produced by the current standard stellar synthesis models. The stellar rotation and binarity may help solve the discrepancy. [ABSTRACT FROM AUTHOR]

Hydrodynamical simulations predict that the jets of young radio sources can inhibit star formation in their host galaxies by injecting heat and turbulence into the interstellar medium (ISM). To investigate jet–ISM interactions in a galaxy with a young radio source, we have carried out a multiwavelength study of the z  = 0.025 Compact Steep Spectrum radio source hosted by the early-type galaxy UGC 05771. Using Keck/OSIRIS observations, we detected H2 1–0 S(1) and [Fe  ii ] emission at radii of 100s of parsecs, which traces shocked molecular and ionized gas being accelerated outwards by the jets to low velocities, creating a 'stalling wind'. At kpc radii, we detected shocked ionized gas using observations from the CALIFA survey, covering an area much larger than the pc-scale radio source. We found that existing interferometric radio observations fail to recover a large fraction of the source's total flux, indicating the likely existence of jet plasma on kpc scales, which is consistent with the extent of shocked gas in the host galaxy. To investigate the star formation efficiency in UGC 05771, we obtained IRAM CO observations to analyse the molecular gas properties. We found that UGC 05771 sits below the Kennicutt–Schmidt relation, although we were unable to definitively conclude if direct interactions from the jets are inhibiting star formation. This result shows that jets may be important in regulating star formation in the host galaxies of compact radio sources. [ABSTRACT FROM AUTHOR]

In the optical spectra of galaxies, the separation of line emission from gas ionized by star formation and an active galactic nucleus (AGN), or by star formation and shocks, are very well-understood problems. However, separating line emission between AGN and shocks has proven difficult. With the aid of a new three-dimensional diagnostic diagram, we show the simultaneous separation of line emission from star formation, shocks, and AGN in NGC 1068, and quantify the ratio of star formation, shocks, and AGN in each spaxel. The AGN, shock, and star formation luminosity distributions across the galaxy accurately align with X-ray, radio, and CO(3–2) observations, respectively. Comparisons with previous separation methods show that the shocked emission heavily mixes with the AGN emission. We also show that if the H α flux is to be used as a star formation rate indicator, separating line emission from as many sources as possible should be attempted to ensure accurate results. [ABSTRACT FROM AUTHOR]

We use data from the Sydney-AAO Multi-object Integral-field spectroscopy (SAMI) Galaxy Survey to study the dynamical scaling relation between galaxy stellar mass M ∗ and the general kinematic parameter |$S_K = \sqrt{K V_{\rm rot}^2 + \sigma ^2}$| that combines rotation velocity V rot and velocity dispersion σ. We show that the log  M ∗ – log  SK relation: (1) is linear above limits set by properties of the samples and observations; (2) has slightly different slope when derived from stellar or gas kinematic measurements; (3) applies to both early-type and late-type galaxies and has smaller scatter than either the Tully–Fisher relation (log  M ∗ − log  V rot) for late types or the Faber–Jackson relation (log  M ∗ − log σ) for early types; and (4) has scatter that is only weakly sensitive to the value of K , with minimum scatter for K in the range 0.4 and 0.7. We compare SK to the aperture second moment (the 'aperture velocity dispersion') measured from the integrated spectrum within a 3-arcsecond radius aperture (⁠|$\sigma _{3^{\prime \prime }}$|⁠). We find that while SK and |$\sigma _{3^{\prime \prime }}$| are in general tightly correlated, the log  M ∗ − log  SK relation has less scatter than the |$\log M_* - \log \sigma _{3^{\prime \prime }}$| relation. [ABSTRACT FROM AUTHOR]