Measuring the baryonic Tully-Fisher relation below the detection threshold

TL;DR

This paper introduces a Bayesian stacking method with a 2D flux density model to measure the baryonic Tully-Fisher relation below detection thresholds, extending analysis to higher redshifts and lower masses.

Contribution

It presents a novel Bayesian stacking technique combined with a 2D flux density model to accurately measure the baryonic Tully-Fisher relation below detection limits, applicable up to z=0.55.

Findings

Accurately reconstructs Tully-Fisher parameters across a broad redshift range.

Determines the M_HI - M_* relation beyond the local universe.

Effectively accounts for HI line shape and noise in measurements.

Abstract

We present a novel 2D flux density model for observed HI emission lines combined with a Bayesian stacking technique to measure the baryonic Tully-Fisher relation below the nominal detection threshold. We simulate a galaxy catalogue, which includes HI lines described either with Gaussian or busy function profiles, and HI data cubes with a range of noise and survey areas similar to the MeerKAT International Giga-Hertz Tiered Extragalactic Exploration (MIGHTEE) survey. With prior knowledge of redshifts, stellar masses and inclinations of spiral galaxies, we find that our model can reconstruct the input baryonic Tully-Fisher parameters (slope and zero point) most accurately in a relatively broad redshift range from the local Universe to $z = 0.3$ for all the considered levels of noise and survey areas, and up to $z = 0.55$ for a nominal noise of $90\,\mu$Jy/channel over 5 deg$^{2}$. Our model can also determine the $M_{\rm HI} - M_{\star}$ relation for spiral galaxies beyond the local Universe, and account for the detailed shape of the HI emission line, which is crucial for understanding the dynamics of spiral galaxies. Thus, we have developed a Bayesian stacking technique for measuring the baryonic Tully-Fisher relation for galaxies at low stellar and/or HI masses and/or those at high redshift, where the direct detection of HI requires prohibitive exposure times.