The slope of the Baryonic Tully-Fisher relation

TL;DR

This study measures the baryonic Tully-Fisher relation (BTFR) in local disk galaxies, finding a slope near 3 that aligns with cosmological predictions and exhibits less scatter than the stellar-mass TFR.

Contribution

It provides the first detailed measurement of the BTFR slope near 3 over a wide baryon mass range, supporting $ m extit{ extbf{Lambda}}$CDM models and suggesting the relation was established early in galaxy evolution.

Findings

BTFR slope is near 3 over 4 dex in baryon mass.

BTFR has less scatter than the stellar TFR.

Scatter correlates with galaxy rotation speed and gas-to-star ratio.

Abstract

We present the results of a baryonic Tully-Fisher relation (BTFR) study for a local sample of relatively isolated disk galaxies. We derive a BTFR with a slope near 3 measured over about 4 dex in baryon mass for our combined \textrm{H\,\scriptsize{I}} and bright spiral disk samples. This BTFR is significantly flatter and has less scatter than the TFR (stellar mass only) with its slope near 4 reported for other samples and studies. A BTFR slope near 3 is in better agreement with the expected slope from simple $\Lambda$CDM cosmological simulations that include both stellar and gas baryons. The scatter in the TFR/BTFR appears to depend on $W_{20}$: galaxies that rotate slower have more scatter. The atomic gas--to--stars ratio shows a break near $W_{20} = 250$ \kms\, probably associated with a change in star formation efficiency. In contrast the absence of such a break in the BTFR suggests that this relation was probably set at the main epoch of baryon dissipation rather than as a product of later galactic evolution.