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# Discovery of massive star formation quenching by non-thermal effects in the centre of NGC 1097

## Abstract

Observations show that massive star formation quenches first at the centres of galaxies. To understand quenching mechanisms, we investigate the thermal and non-thermal energy balance in the central kpc of NGC 1097—a prototypical galaxy undergoing quenching—and present a systematic study of the nuclear star formation efficiency and its dependencies. This region is dominated by the non-thermal pressure from the magnetic field, cosmic rays and turbulence. A comparison of the mass-to-magnetic flux ratio of the molecular clouds shows that most of them are magnetically critical or supported against the gravitational collapse needed to form the cores of massive stars. Moreover, the star formation efficiency of the clouds drops with the magnetic field strength. Such an anti-correlation holds with neither the turbulent nor the thermal pressure. Hence, a progressive build up of the magnetic field results in high-mass stars forming inefficiently, and this may be the cause of the low-mass stellar population in the bulges of galaxies.

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## Acknowledgements

We thank P. Y. Hsieh and R. Beck for providing us with the Submillimeter Array CO and Very Large Array 3.6 cm data. F.S.T. and M.A.P. acknowledge financial support from the Spanish Ministry of Economy and Competitiveness under grant numbers AYA2016-76219-P and MEC-AYA2015-53753-P, respectively.

## Author information

Authors

### Contributions

F.S.T. conceived and designed the project, provided the thermal and non-thermal separation code, analysed the data and wrote the paper. P.M. co-analysed some of the data and contributed to the materials. M.A.P. helped to set up the project. J.A.F.-O. obtained the continuum-subtracted Hα and Paα maps and produced Fig. 1. M.A.P. and J.A.F.-O. commented on the paper and were involved in the science discussion.

### Corresponding author

Correspondence to F. S Tabatabaei.

## Ethics declarations

### Competing interests

The authors declare no competing financial interests.

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Tabatabaei, F.S., Minguez, P., Prieto, M.A. et al. Discovery of massive star formation quenching by non-thermal effects in the centre of NGC 1097. Nat Astron 2, 83–89 (2018). https://doi.org/10.1038/s41550-017-0298-7

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• DOI: https://doi.org/10.1038/s41550-017-0298-7

• ### Star formation quenching in massive galaxies

• Allison Man
• Sirio Belli

Nature Astronomy (2018)