Stellar encounters with giant molecular clouds

Abstract

Giant molecular clouds (GMCs) are believed to affect the biospheres of planets as their host star passes through them. We simulate the trajectories of stars and GMCs in the Galaxy and determine how often stars pass through GMCs. We find a strong decreasing dependence with Galactocentric radius, and with the velocity perpendicular to the Galactic plane, $V_z$. The \textit{XY}-component of the kinematic heating of stars was shown to not affect the GMC hit rate, unlike the \textit{Z}-dependence ($V_z$) implies that stars hit fewer GMCs as they age. GMCs are locations of star formation, therefore we also determine how often stars pass near supernovae. For the supernovae the decrease with $V_z$ is steeper as how fast the star passes through the GMC determines the probability of a supernova encounter. We then integrate a set of Sun-like trajectories to see the implications for the Sun. We find that the Sun hits $1.6\pm 1.3$ GMCs per Gyr which results in $1.5\pm 1.1$ or (with correction for clustering) $0.8\pm 0.6$ supernova closer than 10 pc per Gyr. The different supernova frequencies are from whether one considers multiple supernova per GMC crossing (few Myr) as separate events. We then discuss the effect of the GMC hits on the Oort cloud, and the Earth's climate due to accretion, we also discuss the records of distant supernova. Finally, we determine Galactic Habitable Zone using our model. For the thin disk we find it to lie between 5.8-8.7 kpc and for the thick disk to lie between 4.5-7.7 kpc.

Accepted to MNRAS

References in corpus (19)

• The mass distribution and gravitational potential of the Milky Way
• Physical properties of molecular clouds for the entire Milky Way disk
• ATLASGAL --- properties of a complete sample of Galactic clumps
• Bias-free Measurement of Giant Molecular Cloud Properties
• From Shock Breakout to Peak and Beyond: Extensive Panchromatic Observations of the Type Ib Supernova 2008D associated with Swift X-ray Transient 080109
• The observed spiral structure of the Milky Way
• The Global Evolution of Giant Molecular Clouds. I: Model Formulation and Quasi-Equilibrium Behavior
• Transient spirals as superposed instabilities
• Time resolved 2 million year old supernova activity discovered in Earth's microfossil record
• ATLASGAL - Kinematic distances and the dense gas mass distribution of the inner Galaxy
• A radial age gradient in the geometrically thick disk of the Milky Way
• The age-velocity dispersion relation of the Galactic discs from LAMOST-Gaia data
• Dissecting simulated disc galaxies I: the structure of mono-age populations
• Recent advances in the determination of some Galactic constants in the Milky Way
• The galactic habitable zone of the Milky Way and M31 from chemical evolution models with gas radial flows
• A new method for estimating the pattern speed of spiral structure in the Milky Way
• Capture of exocomets and the erosion of the Oort cloud due to stellar encounters in the Galaxy
• Stable habitable zones of single Jovian planet systems
• Supernova Ejecta in Ocean Cores Used as Time Constraints for Nearby Stellar Groups