Cosmicflows-2: I-band Luminosity - HI Linewidth Calibration

TL;DR

This paper refines the calibration of galaxy luminosity and rotation rate relations using new linewidth measures and photometry, aiming to improve distance measurements and contribute to the Cosmicflows-2 dataset.

Contribution

It introduces a new linewidth parameter and reconstructs the luminosity-linewidth template with updated calibration data.

Findings

Calibrated the luminosity-linewidth relation using 267 galaxies in clusters.

Set the zero point with 36 galaxies having Cepheid or TRGB distances.

Estimated H0 to be approximately 75 km s-1 Mpc-1.

Abstract

In order to measure distances with minimal systematics using the correlation between galaxy luminosities and rotation rates it is necessary to adhere to a strict and tested recipe. We now derive a measure of rotation from a new characterization of the width of a neutral Hydrogen line profile. Additionally, new photometry and zero point calibration data are available. Particularly the introduction of a new linewidth parameter necessitates the reconstruction and absolute calibration of the luminosity-linewidth template. The slope of the new template is set by 267 galaxies in 13 clusters. The zero point is set by 36 galaxies with Cepheid or Tip of the Red Giant Branch distances. Tentatively, we determine H0 = 75 km s-1 Mpc-1. Distances determined using the luminosity-linewidth calibration will contribute to the distance compendium Cosmicflows-2.