Earth-Like is an interactive website and twitter bot that allows users to explore changes in the average global surface temperature of an Earth-like planet due to variations in the surface oceans and emerged land coverage, rate of volcanism (degassing) and the level of the received solar radiation. The temperature is calculated using a simple carbon–silicate cycle model to change the level of CO2 in the atmosphere based on the chosen parameters. The model can achieve a temperature range exceeding −100°C to 100°C by varying all three parameters, including freeze-thaw cycles for a planet with our present-day volcanism rate and emerged land fraction situated at the outer edge of the habitable zone. To increase engagement, the planet is visualized by using a neural network to render an animated globe, based on the calculated average surface temperature and chosen values for land fraction and volcanism. The website and bot can be found at earthlike.world and on twitter as @earthlikeworld. Initial feedback via a user survey suggested that Earth-Like is effective at demonstrating that minor changes in planetary properties can strongly impact the surface environment. The goal of the project is to increase understanding of the challenges we face in finding another habitable planet due to the likely diversity of conditions on rocky worlds within our Galaxy.

We performed high resolution 3D hydrodynamical simulations of the barred galaxy M83 and investigated formation and evolution of the giant molecular clouds (GMCs) and star formation activity. We compared two simulations with and without stellar feedback. We found that the feedback disperses the cloud gas and causes clouds to inflow toward the galactic centre region due to hydrodynamical drag. The effect raises the star formation rate (SFR) and star formation efficiency (SFE) in the central bar region.

We performed three-dimensional hydrodynamical simulations of idealized giant molecular cloud collisions including star formation and radiative transfer. We found that the characteristics of the colliding systems are similar to the observations of the Spitzer bubbles, suggesting these objects could be created in such interactions. A high velocity collision creates a top-heavy core mass distribution but is not strongly affected by radiation. At lower collision speeds, the HII regions have time to expand within the shock and promote the formation of massive cores.

The existence of grand design spiral galaxies in the universe is still a standing problem. The passage of a small companion is known to be able to induce spiral structures in disc galaxies, but there remains questions over how relevant this mechanism is to the galaxies observed in the real universe. Our study aims to address two key points regarding such interactions; the limiting mass companion needed to drive tidal spiral structures, and the differences between the resulting gas and stellar morphology. We find the minimum mass of a companion to be as low as 5% of the stellar mass of the galaxy, and that the arms formed in the gas and the stars display very minor dynamical and morphological differences.

Observations and simulations have now reached the point where the giant molecular cloud (GMCs) populations can be studied over a whole galaxy. This is immensely helpful for understanding star formation. Yet, are these two groups really comparing the same objects? While simulators work in 6D (x, y, z, vx, vy, vz) position-position-position (PPP) space, observers see 2 + 1D (RA, Dec, vlos) projected properties along the line of sight, identifying clouds in position-position-velocity (PPV) space. In this research we generated PPP and PPV data for a high-resolution simulated galaxy and compared the identified clouds in both data sets. The results show that 70% of the clouds have a single counterpart in each data structure. Cloud boundaries of these clouds are indeed the same. Scatter of the derived cloud properties (radius and velocity dispersion) between PPP and PPV are typically within a factor of two. However, this small scatter can make it difficult to determine if a cloud is truly gravitationally bound.

We simulated an isolated quiescent Milky Way-type galaxy with a maximum effective resolution of 7.8 pc. Clouds formed in the interstellar medium through gravitational fragmentation and became the sites for star formation. We tracked the evolution of the clouds through 300 Myr in the presence of star formation, photoelectric heating and feedback from Type II supernovae. The cloud mass distribution agreed well with observational results. Feedback suppressed star formation but did not destroy the surrounding cloud. Collisions between clouds were found to be sufficiently frequent to be a significant factor in determining the star formation rate.