Resolving the star formation cycle from GMCs to star clusters in lensed galaxies at cosmic noon

by Mirka Dessauges-Zavadsky (Université de Genève)

Wednesday 20 Sept 2023, 11:30 → 12:30 Europe/Rome

Sala Jappelli (Osservatorio Astronomico di Padova)

Galaxies at z>1 show increasingly higher gas fractions and SFRs, in the form of rotationally-supported turbulent disks. Their morphology is characterised by UV-bright clumps. Deep HST and now JWST observations of strongly lensed galaxies has enabled us to resolve these clumps down to tens of parsecs, revealing they are young, massive (10^6-10^8 Msun) and dense star cluster complexes, significantly contributing to the recent star formation of the host galaxy and the build-up of its stellar mass. They are believed to be formed from the fragmentation due to gravitational instability of the galaxy disks, which at high z can fragment at larger scales than in local disks because of their gas-rich and turbulent nature. Our recent detection of giant molecular clouds (GMCs) in two strongly lensed clumpy galaxies at z=1, observed with ALMA in CO down to 30 pc resolution, reveals also more massive and denser (~10^3 Msun/pc^2) GMCs than the local GMCs. They point toward an evolution in their physical properties, reflecting the overall evolution of the ISM conditions (disk hydrostatic pressure, turbulence, density, radiation field) of galaxies across cosmic time and suggesting that GMC properties are adjusted to the ambient ISM where they form. The comparison between the mass distribution of GMCs and stellar clumps hosted in the same z=1 galaxies, moreover, evidences a much higher star formation efficiency (~30%) than observed in nearby galaxies (<6%). Our JWST IFU observations will enable us to confirm the possible fundamental increase of the efficiency of high-z GMCs in forming stars thanks to the spatial cross-match of GMCs with very young star-forming regions (<10 Myr) as traced by the Ha emission. These first studies demonstrate that multi-wavelength observations of strongly lensed high-z galaxies can probe the star-formation cycle from the collapse of transient GMCs to the formation of stars in clustered and hierarchically organised star-forming regions at <100 pc scales.

 

Link alla videochiamata: https://meet.google.com/tzd-crqx-rpx
 

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