Discovery of massive star formation quenching by nonthermal effects in the center of NGC 1097

TL;DR

This study reveals that in the center of NGC 1097, nonthermal effects like magnetic fields and cosmic rays suppress massive star formation, providing insights into galaxy quenching processes.

Contribution

It demonstrates that magnetic support and nonthermal pressures are key factors in quenching star formation in galaxy centers, a novel focus in understanding galactic evolution.

Findings

Magnetic fields are critical in supporting molecular clouds against collapse.

Star formation efficiency decreases with increasing magnetic field strength.

Nonthermal pressures dominate over thermal and turbulent pressures in the central region.

Abstract

Observations show that massive star formation quenches first at centers of galaxies. To understand quenching mechanisms, we investigate the thermal and nonthermal energy balance in the central kpc of NGC1097- 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 nonthermal 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 gravitational collapse needed to form 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 built up of the magnetic field results in high-mass stars forming inefficiently, and it may be the cause of the low-mass stellar population in the bulges of galaxies.