Towards a multi-tracer timeline of star formation in the LMC -- I.\ Deriving the lifetimes of H\,{\sc i} clouds

Abstract

The time-scales associated with the various stages of the star formation process remain poorly constrained. This includes the earliest phases of star formation, during which molecular clouds condense out of the atomic interstellar medium. We present the first in a series of papers with the ultimate goal of compiling the first multi-tracer timeline of star formation, through a comprehensive set of evolutionary phases from atomic gas clouds to unembedded young stellar populations. In this paper, we present an empirical determination of the lifetime of atomic clouds using the Uncertainty Principle for Star Formation formalism, based on the de-correlation of H$\alpha$ and H\,{\sc i} emission as a function of spatial scale. We find an atomic gas cloud lifetime of 48$\begin{array}{c}+13\\ -8\end{array}$\,Myr. This timescale is consistent with the predicted average atomic cloud lifetime in the LMC (based on galactic dynamics) that is dominated by the gravitational collapse of the mid-plane ISM. We also determine the overlap time-scale for which both H\,{\sc i} and H$\alpha$ emission are present to be very short ($t_{over}<1.7$\,Myr), consistent with zero, indicating that there is a near-to-complete phase change of the gas to a molecular form in an intermediary stage between H\,{\sc i} clouds and H\,{\sc ii} regions. We utilise the time-scales derived in this work to place empirically determined limits on the time-scale of molecular cloud formation. By performing the same analysis with and without the 30 Doradus region included, we find that the most extreme star forming environment in the LMC has little effect on the measured average atomic gas cloud lifetime. By measuring the lifetime of the atomic gas clouds, we place strong constraints on the physics that drives the formation of molecular clouds and establish a solid foundation for the development of a multi-tracer timeline of star formation in the LMC.

17 pages, 8 figures. Accepted for publication in MNRAS

References in corpus (14)

• The lifecycle of molecular clouds in nearby star-forming disc galaxies
• Fast and inefficient star formation due to short-lived molecular clouds and rapid feedback
• The dynamical evolution of molecular clouds near the Galactic Centre - I. Orbital structure and evolutionary timeline
• The Herschel Dwarf Galaxy Survey: I. Properties of the low-metallicity ISM from PACS spectroscopy
• Dynamically Driven Evolution of the Interstellar Medium in M51
• Dust and Gas in the Magellanic Clouds from the HERITAGE Herschel Key Project. II. Gas-to-Dust Ratio Variations across ISM Phases
• Short GMC lifetimes: an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS)
• The 21-SPONGE HI Absorption Survey I: Techniques and Initial Results
• How Galactic Environment affects the Dynamical State of Molecular Clouds and their Star Formation Efficiency
• Not all stars form in clusters -- $Gaia$-DR2 uncovers the origin of OB associations
• The Transition from Atomic to Molecular Hydrogen in Interstellar Clouds: 21cm Signature of the Evolution of Cold Atomic Hydrogen in Dense Clouds
• Seeding the Galactic Centre gas stream: gravitational instabilities set the initial conditions for the formation of protocluster clouds
• Not all stars form in clusters - measuring the kinematics of OB associations with $Gaia$
• An ATCA Survey of HI Absorption in the Magellanic Clouds I: HI Gas Temperature Measurements in the Small Magellanic Cloud

Cited by in corpus (13)

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• PHANGS-JWST First Results: Duration of the early phase of massive star formation in NGC628
• A scaling relation for the molecular cloud lifetime in Milky Way-like galaxies
• PHANGS: Constraining Star Formation Timescales Using the Spatial Correlations of Star Clusters and Giant Molecular Clouds
• Empirically-motivated early feedback: momentum input by stellar feedback in galaxy simulations inferred through observations
• WISDOM project -- XI. Star Formation Efficiency in the Bulge of the AGN-host Galaxy NGC 3169 with SITELLE and ALMA
• Towards a multi-tracer timeline of star formation in the LMC -- II. The formation and destruction of molecular clouds
• Pre-supernova feedback mechanisms drive the destruction of molecular clouds in nearby star-forming disc galaxies
• An uncertainty principle for star formation -- V. The influence of dust extinction on star formation rate tracer lifetimes and the inferred molecular cloud lifecycle
• Duration and properties of the embedded phase of star formation in 37 nearby galaxies from PHANGS-JWST