Kavli Affiliate: Yingjie Peng
| First 5 Authors: Bitao Wang, Yingjie Peng, Michele Cappellari, ,
| Summary:
The hierarchical structure formation of our Universe inherently involves
violent and chaotic episodes of mass assembly such as galaxy mergers. The level
of bulk rotation of the collisionless stellar systems of galaxies reflects to
what extent the galaxies, on the other hand, have assembled their stars during
tranquil and ordered formation history, which fosters the growth of cohesively
rotating structures. Observationally, galaxy populations show a wide spectrum
of morphology and shapes, with different levels of rotational support. Despite
the obvious variety and complexity, in this work we find that at a given
stellar mass of galaxies, the distribution of the intrinsic spin parameter
$lambda_{R_{rm e},mathrm{intr}}$, i.e. the normalized specific angular
momentum of stars, appears to be universally bimodal among galaxies in all star
formation states and also in different environments. This ubiquitous bimodality
in kinematic morphology evolves systematically with star formation and is
particularly apparent for transitional galaxies of intermediate star formation
rates, indicating that star formation quenching is proceeding separately within
two distinct kinematic populations dominated by cold discs and hot spheroids.
We show that the two populations also have contrasting recent star formation
histories and metal enrichment histories, which reveal their divergent pathways
to formation and quenching.
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