The mid-infrared Tully-Fisher relation: Spitzer Surface Photometry

TL;DR

This paper discusses a new mid-infrared calibration of the Tully-Fisher relation using Spitzer Space Telescope data, emphasizing photometric consistency and minimal obscuration for accurate galaxy distance measurements.

Contribution

It introduces a uniform analysis procedure for Spitzer mid-infrared data and provides a calibrator sample of 235 galaxies for the Tully-Fisher relation.

Findings

Photometry uncertainties below 0.05 mag for normal spirals

A calibrator sample of 235 galaxies established

Preparation for calibration of luminosity-rotation relation underway

Abstract

The availability of photometric imaging of several thousand galaxies with the Spitzer Space Telescope enables a mid-infrared calibration of the correlation between luminosity and rotation in spiral galaxies. The most important advantage of the new calibration in the 3.6 micron band, IRAC ch.1, is photometric consistency across the entire sky. Additional advantages are minimal obscuration, observations of flux dominated by old stars, and sensitivity to low surface brightness levels due to favorable backgrounds. Through Spitzer cycle 7 roughly 3000 galaxies had been observed and images of these are available at the Spitzer archive. In cycle 8 a program called Cosmic Flows with Spitzer has been initiated that will increase by 1274 the available sample of spiral galaxies with inclinations greater than 45 degrees from face-on suitable for distance measurements. This paper describes procedures based on the photometry package Archangel that are being employed to analyze both the archival and the new data in a uniform way. We give results for 235 galaxies, our calibrator sample for the Tully-Fisher relation. Galaxy magnitudes are determined with uncertainties held below 0.05 mag for normal spiral systems. A subsequent paper will describe the calibration of the [3.6] luminosity-rotation relation.