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 centers of galaxies. To understand quenching mechanisms, we investigate the thermal and nonthermal 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 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.

On the origin of magnetic driven winds and the structure of the galactic dynamo in isolated galaxies

“…(v) Relation between SFR and magnetic field: Globally we find that the SFR scales with the star formation rate surface density with a power law slope between 0.3 and 0.45 in good agreement with the results from Schleicher & Beck (2013), Niklas & Beck (1997) and Tabatabaei et al (2013). However, locally in the spiral arms we find that the star formation rate can increase while the magnetic field is decreasing due to magnetic dissipation and diffusion which is included in our MHD equations (Tabatabaei et al 2018).…”

“…We find regions within the galaxy that do not follow the global power law scaling and the magnetic field is decreasing as a function of the star formation rate. This is consistent with the findings of Tabatabaei et al (2018) who observed several molecular clouds in the nearby galaxy NGC 1097 and find a power law scaling with a negative exponent. In our simulations this effect is due to the effect that we include a diffusion term within our induction equation.…”

“…Niklas & Beck 1997). Further, we note the results of Tabatabaei et al (2018) who observed the centre of NGC 1047 and found a antic correlation between the magnetic field strength and the star formation rate surface density. We find the same if we look on more local regions of the galaxy.…”

New Insights in Extragalactic Magnetic Fields

“…The blue and red points show the narrow-and broad-line GMAs, respectively. Strong non-circular motions/shocks in the broad-line GMAs can act as additional cause of the low SFR ff in these clouds (Tabatabaei et al 2018).…”

“…This is particularly important in high-resolution studies of galaxies even at low frequencies. The dust-unbiased Thermal Radio Template (TRT) methods, developed by Tabatabaei et al (2007), Tabatabaei et al (2013), and Tabatabaei et al (2018), map the thermal and the nonthermal synchrotron emission in galaxies 1 81 2 Fatemeh S. Tabatabaei without any assumption about the synchrotron spectrum. These methods are sensitive to the diffuse ISM structures and hence ideal to study the role of the magnetic fields in the energy balance and structure formation in different locations in a galaxy.…”