How galaxies replenish their gas supply in order to sustain star formation, is a research topic of many of the new and upcoming neutral atomic hydrogen (Hi) surveys on the SKA precursor instruments. This replenishment, or accretion, of gas in the form of Hi is likely to occur at column densities one or two orders of magnitude below previous observational limits and it has, so far, not been unambiguously detected. We present recent deep Hi observations of NGC 5068, an isolated nearby star-forming galaxy observed by MeerKAT as part of the MHONGOOSE survey. This survey is the deepest Hi survey of nearby galaxies until the advent of the SKA and is reaching column densities of resolution. The combination of the resolution and sensitivity of the MeerKAT HI data have revealed “fingers” of low column density gas extending out from the main Hi disk of the galaxy. While the origin of these fingers remains a mystery for now, the dynamics of the main galaxy disk and the outer disk in which the fingers are located, as well as the morphology of the fingers, does not seem to suggest a previous merger event.

The formation of the global stellar system of galaxies are studied through the circular velocity curves of CALIFA nearby galaxies by sequencing the depth and size of the central gravitation-potential vessel and its dynamical mass, relative to the masses of the stellar system and of the parent halo, with the population or age parameters, to explore the dynamical characteristics of the dissipative contracting baryonic matter.

Winds of massive stars are an important ingredient in determining their evolution, final remnant mass, and feedback to the surrounding interstellar medium. We compare empirical results for OB star winds at low metallicity with theoretical predictions. Observations suggest very weak winds at SMC metallicity, but there are exceptions. We identified promising candidates for rotationally enhanced mass-loss rates with two component wind and partially stripped stars hiding among OB stars with slow but dense wind in the SMC. A preliminary analysis of these systems, derived parameters, and their implications are discussed. Finally, we briefly discuss the interaction of OB winds near black holes in X-ray binaries.

Jellyfish galaxies are starburst galaxies with ram-pressure-stripped tails and blue star-forming knots. These galaxies show a snapshot of star formation enhancement triggered by ram pressure stripping (RPS), being important targets for studying the RPS-induced star formation in gas-rich galaxies. Here we investigate the star formation activity of five jellyfish galaxies in massive clusters, using Gemini GMOS/IFU observations. From the Hα-derived star formation rates (SFRs), we find that our sample shows higher SFR excess to the star formation main sequence than the jellyfish galaxies in low-mass clusters. From the compiled sample of jellyfish galaxies in low-mass to high-mass host clusters, we suggest that the star formation activity of jellyfish galaxies has positive correlations with host cluster mass and degree of RPS. These relationships imply that higher ram pressure environments tend to trigger stronger starbursts in jellyfish galaxies in the early stage of RPS.

The long-term behavior of a colliding wind binary WR 25 is presented using archival X-ray data obtained over a time span of : 16 years. The present analysis reveals phase-locked variations repeating consistently over many consecutive orbits of the source (with binary orbital period : 208 days). A significant deviation of the X-ray flux with respect to the theoretical 1/D trend (D is the binary separation) close to periastron passage has been observed. This may occur due to the shifting of the adiabatic wind collision to the radiative regime in that part of the orbit. Further, no signature of X-ray emission in 10.0-79.0 keV energy range attributable to inverse Compton scattering is detected by NuSTAR.

At least half of the local galaxies reside in galaxy groups, which indicates that the group is the common environment where galaxies evolve. Therefore, it is important to probe how significantly galaxies are affected by group environmental processes, in order to obtain a better understanding of galaxy evolution. We carried out a new CO imaging survey for 31 galaxies in the IC 1459 and NGC 4636 groups, using the Atacama Compact Array, to study the effect of the group environment on the molecular gas properties and the star formation activity. With our resolved CO data, combined with high-resolution H i images, we find asymmetric CO and H i distributions in the group galaxies. Compared to isolated galaxies, group members have relatively low molecular gas fraction and low star formation rate. These results suggest that the group environment can change the properties of cold gas components and star formation in group galaxies.

High-energy stellar irradiation can photoevaporate planetary atmospheres, which can be observed in spectroscopic transits of hydrogen lines. Here, we investigate the effect of planetary magnetic fields on the observational signatures of atmospheric escape in hot Jupiters.

When a supernova shockwave launched deep inside the star exits the surface, it probes the circumstellar medium established by prior mass loss from the pre supernova star. The bright electromagnetic display accompanying the shock breakout is influenced by the properties of the star and scripts the history of the stellar mass loss. We investigate with MESA and STELLA codes the radiative display resulting from a set of progenitors that we evolved to core collapse. We simulate with different internal convective overshoot and compositional mixing and two sets of mass loss schema, one the standard “Dutch” scheme and another, an enhanced, episodic mass loss at a late stage. Shock breakout from the star shows double peaked bolometric light curves for the Dutch wind, as well as high velocity ejecta accelerated during shock breakout. We contrast the breakout flash from an optically thick CSM with that of the rarified medium.

Radial colour gradients within galaxies arise from gradients of stellar age, metallicity, and dust reddening. Large samples of colour gradients from wide-area imaging surveys can be used to constrain galaxy formation models. Here we measured colour gradients for low-redshift galaxies using photometry from the 9th DESI Legacy Imaging Survey (LS), which reaches r ∼ 24 over ∼14,000 deg2. We investigate empirical relationships between colour gradients, M*, and sSFR. We compared our results with the prediction of the Illustris TNG-100 simulation using SDSS mock images.

In order to study gas evolution in the central region of a barred galaxy, we have performed numerical simulations of gas in the potential of the barred galaxy. We have found that the bar potential produces a gas ring within the central 1 kpc region. In the gas ring, active star and star cluster formations take place. Since the gas ring is dense enough to become self-gravitationally unstable, gas clouds form in the ring. These gas clouds interact gravitationally and collide with the other clouds. Such interaction and collision reduces their angular momentums effectively, and finally gas clouds fall into the galactic center. These processes triggers episodic gas fueling to the galactic center.

NGC 7293, the Helix nebula, represents one of the rare instances in which theoretical predictions of stellar evolution can be accurately tested against observations since the precise parallax distance and the velocity and proper motion of the star are well known. We present numerical simulations of the formation of the Helix PN that are fully constrained by the progenitor stellar mass, stellar evolution history, and star-interstellar medium (ISM) interaction. In the simulations, multiple bow-shock structures are formed by fragmentation of the shock front where the direct interaction of the stellar wind with the ISM takes place.

The role of atmospheric evaporation in shaping exoplanet populations remains a major unsolved problem in the literature. Observational evidence, like the bimodal distribution of exoplanet radii, suggests a catastrophic past in which exoplanets with masses of approximately 1–10M⊕ often lose their primordial envelopes and experience a drastic reduction in their radii. Our knowledge of the mechanisms behind atmospheric evaporation remains nebulous, with new models regularly introduced in the literature. Understanding the principles behind these models and knowing when to apply them is essential for constraining how planets evolve. This communication reviews the mechanisms behind atmospheric evaporation by exploring observations and theory, as well as introducing some of the principles in the forthcoming paper Modirrousta-Galian & Korenaga (in press).

The standard galaxy formation model predicts that galaxies form within a Cold Dark Matter (CDM) halo and that galaxies are dominated by dark matter. However, recent observations have discovered dark-matter-deficient galaxies with much less dark matter mass than theoretical predictions, and the process of their formation has been discussed. Here, we investigate the physical processes of galaxy formation by collisions between gas-rich dark matter subhalos within the context of the CDM paradigm. We investigate the formation process of dark-matter-deficient galaxies by running three-dimensional simulations of the collision process between dark matter subhalos (DMSHs) with the same mass of 109M⊙ colliding the velocity of 100 km s−1. We then compared the effect of different supernova feedback models, the subgrid physics of the simulation, on the collision-induced formation of galaxies. The results show that the strong feedback model ejects gas out of the system more efficiently than the weak feedback model, leading to lower star formation rates and the formation of a more extended galaxy. Finally, dark-matter-deficient galaxies with stellar masses of ∼ 107M⊙ and ∼ 108M⊙ are formed in the weak and strong feedback models, respectively.

The KEPLER transit survey with follow-up spectroscopic observations has discovered numerous small planets (super-Earths/sub-Neptunes) and revealed intriguing features of their sizes, orbital periods, and their relations between adjacent planets. The planet size distribution exhibits a bimodal distribution separated by a radius gap at around 1.8 Earth radii. Besides, these small planets within multiple planetary systems show that adjacent planets are similar in size and their period ratios of adjacent planet pairs are similar as well, a phenomenon often dubbed as peas-in-a-pod in the exoplanet community. While the radius gap has been predicted and theorized for years, whether it can be relevant to the orbital architecture peas-in-a-pod is physically unknown. For the first time, we attempted to model both features together through planet formation and evolution processes involving giant impacts and photoevaporation. We showed that our model is generally consistent with the KEPLER results but with a smaller radius gap. The impact of Kubyshikina’s model for photoevaporation on our model is discussed.

Recent integral-field spectroscopy observations have revealed that thick- and thin-disk star-formation histories are regulated by the interplay of internal and external processes. We analyze stellar-population properties of 24 spiral galaxies from the AURIGA zoom-in cosmological simulations, to offer a more in-depth interpretation of observable properties. We present edge-on maps of stellar age, metallicity and [Mg/Fe] abundance, and we extract the star-formation and chemical-evolution histories of thin and thick disks. Both show signs of the interplay between internal chemical enrichment and gas and star accretion. Thick disks show particularly complex stellar populations, including an in-situ component, formed from both slowly enriched and accreted more pristine gas, and an additional significant fraction of ex-situ stars.

Magnetism can greatly impact the evolution of stars. In some stars with OBA spectral types there is direct evidence via the Zeeman effect for stable, large-scale magnetospheres, which lead to the spin-down of the stellar surface and reduced mass loss. So far, a comprehensive grid of stellar structure and evolution models accounting for these effects was lacking. For this reason, we computed and studied models with two magnetic braking and two chemical mixing schemes in three metallicity environments with the mesa software instrument. We find notable differences between the subgrids, which affects the model predictions and thus the detailed characterisation of stars. We are able to quantify the impact of magnetic fields in terms of preventing quasi-chemically homogeneous evolution and producing slowly-rotating, nitrogen-enriched (“Group 2”) stars. Our model grid is fully open access and open source.

This paper reports on four of the sources observed in the KAGONMA (KAgoshima Galactic Object survey with the Nobeyama 45-m telescope by Mapping in Ammonia lines) project for which mapping observations have been completed (KAG35, KAG45, KAG64, and KAG71). In this study, we compiled the analysis results of four sources for which mapping observations were completed in the KAGONMA project and statistically investigated the range to which star formation activity affects the molecular gas. In order to investigate the affected range, we analyzed the heating range by focusing on the temperature distribution of the molecular cloud and found that it is within about 3 pc. This suggests that direct star formation feedback in molecular clouds is very spatially limited.

Very massive stars (VMS) dominate the physics of young clusters due to their extreme stellar winds. The mass lost by these stars in their winds determine their evolution, chemical yields and their end fates. In this contribution we study the main-sequence evolution of VMS with a new mass-loss recipe that switches from optically-thin O star winds to optically-thick Wolf-Rayet type winds through the model independent transition mass loss.

The CO-to-H2 conversion factor (αCO) is crucial for accurate estimation of the amount and properties of molecular gas. However, αCO is known to vary with environmental conditions, and previous kpc-scale studies have revealed lower αCO in the centers of some barred galaxies, including NGC 3351, 3627, and 4321. We present ALMA Band 3, 6, and 7 observations toward the inner ∼2 kpc of these galaxies tracing 12CO, 13CO, and C18O lines at ∼100 pc resolution. We show that dynamical effects resulting from turbulence/shear can lead to substantially lower αCO in the bar-driven inflows of NGC 3351 due to lower optical depth. A clear, positive correlation between αCO and 12CO optical depth is seen in all three galaxy centers. We also find that the CO/13CO(2–1) ratio mainly traces the 12CO optical depth, and thus it may be a useful observable in predicting αCO variation in galaxy centers.

Atmospheric escape has traditionally been observed using hydrogen Lyman-α transits, but more recent detections utilise the metastable helium triplet lines at 1083nm. Capable of being observed from the ground, this helium signature offers new possibilities for studying atmospheric escape. Such detections are dependent however on the specific high-energy flux received by the planet. Previous studies show that the extreme-UV band both drives atmospheric escape and populates the triplet state, whereas lower energy mid-UV radiation depopulates the state through photoionisations. This is supported observationally, with the majority of planets with 1083nm detections orbiting a K-type star, which emits a favourably high ratio of EUV to mid-UV flux. The goal of our work is understanding how the observability of escaping helium evolves. We couple our one-dimensional hydrodynamic non-isothermal model of atmospheric escape with a ray-tracing technique to achieve this. We consider the evolution of the stellar radiation and the planet’s gravitational potential.