Speaker
Diederik Kruijssen
(MPA Garching)
Description
It was recently found that the SFR in the Central Molecular Zone (CMZ, i.e. the central 500 pc) of the Milky Way is lower by a factor of 10-100 than expected for the substantial amount of dense gas it contains, which challenges existing star formation (SF) theories. I show that in terms of properties unrelated to SF activity, the CMZ follows several of the scaling relations that hold for gas-rich, high-redshift galaxies, and I quantify which physical mechanisms could be causing the low SFR. Possible explanations are episodic SF, the dynamical heating fo clouds by mutual interactions, and an elevated critical density for SF due to the high turbulent pressure - potentially in conjunction with weak magnetic effects and a bottom-heavy IMF. I rule out the existence of a universal density threshold for SF, as well as any key influence of the Toomre stability of the disc, the atomic-to-molecular phase transition of hydrogen, the tidal field, the magnetic field, and cosmic ray heating.