The Interstellar Medium and star formation on kpc size scales

Abstract

By resimulating a region of a global disc simulation at higher resolution, we resolve and study the properties of molecular clouds with a range of masses from a few 100's M${}_{\odot }$ to $10^6$ M${}_{\odot }$. The purpose of our paper is twofold, i) to compare the ISM and GMCs at much higher resolution compared to previous global simulations, and ii) to investigate smaller clouds and characteristics such as the internal properties of GMCs which cannot be resolved in galactic simulations. We confirm the robustness of cloud properties seen in previous galactic simulations, and that these properties extend to lower mass clouds, though we caution that velocity dispersions may not be measured correctly in poorly resolved clouds. We find that the properties of the clouds and ISM are only weakly dependent on the details of local stellar feedback, although stellar feedback is important to produce realistic star formation rates and agreement with the Schmidt-Kennicutt relation. We study internal properties of GMCs resolved by $10^4-10^5$ particles. The clouds are highly structured, but we find clouds have a velocity dispersion radius relationship which overall agrees with the Larson relation. The GMCs show evidence of multiple episodes of star formation, with holes corresponding to previous feedback events and dense regions likely to imminently form stars. Our simulations show clearly long filaments, which are seen predominantly in the inter-arm regions, and shells.

13 pages, 11 figures, accepted for publication in MNRAS, movies at http://empslocal.ex.ac.uk/people/staff/cld214/movies_region.html and http://empslocal.ex.ac.uk/people/staff/cld214/movies_region2.html

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• Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity
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• Discovery of a coherent, wave-like velocity pattern for the Radcliffe Wave
• The role of previous generations of stars in triggering star formation and driving gas dynamics
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• Weather Forecast of the Milky Way: Shear and Stellar feedback determine the lives of Galactic-scale filaments
• Dust Buried Compact Sources in the Dwarf Galaxy NGC 4449
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• Twelve Decades: Probing the Interstellar Medium from kiloparsec to sub-AU scales