A Transition Mass in the Local Tully-Fisher Relation

TL;DR

This study identifies a critical stellar mass in the local Tully-Fisher relation where galaxy morphology and kinematics shift, indicating a transition in disk formation processes.

Contribution

It reveals a specific transition mass in the Tully-Fisher relation, distinguishing between disk-dominated and irregular galaxies at low redshift.

Findings

A transition stellar mass at log M* = 9.5 M_sun.

Above this mass, galaxies are predominantly rotation-dominated disks.

Below this mass, galaxies show diverse morphologies and kinematics.

Abstract

We study the stellar mass Tully-Fisher relation (TFR, stellar mass versus rotation velocity) for a morphologically blind selection of emission line galaxies in the field at redshifts 0.1 $<$ z $<$ 0.375. Kinematics ($\sigma_g$, V$_{rot}$) are measured from emission lines in Keck/DEIMOS spectra and quantitative morphology is measured from V- and I-band Hubble images. We find a transition stellar mass in the TFR, $\log$ M$_*$ = 9.5 M$_{\odot}$. Above this mass, nearly all galaxies are rotation-dominated, on average more morphologically disk-like according to quantitative morphology, and lie on a relatively tight TFR. Below this mass, the TFR has significant scatter to low rotation velocity and galaxies can either be rotation-dominated disks on the TFR or asymmetric or compact galaxies which scatter off. We refer to this transition mass as the "mass of disk formation", M$_{\mathrm{df}}$ because above it all star-forming galaxies form disks (except for a small number of major mergers and highly star-forming systems), whereas below it a galaxy may or may not form a disk.