The Planetary Nebula Spectrograph survey of S0 galaxy kinematics. Data and Overview

TL;DR

This study uses planetary nebulae as tracers to analyze the stellar kinematics of six S0 galaxies across different environments, providing insights into their formation mechanisms through detailed kinematic data.

Contribution

It introduces a new dataset of planetary nebulae kinematics for six S0 galaxies, demonstrating their effectiveness in tracing stellar motions and aiding in understanding galaxy origins.

Findings

PNe spatial distribution matches stellar light

PNe kinematics extend previous measurements smoothly

Rotational motion dominates galaxy kinematics

Abstract

The origins of S0 galaxies remain obscure, with various mechanisms proposed for their formation, likely depending on environment. These mechanisms would imprint different signatures in the galaxies' stellar kinematics out to large radii, offering a method for distinguishing between them. We aim to study a sample of six S0 galaxies from a range of environments, and use planetary nebulae (PNe) as tracers of their stellar populations out to very large radii, to determine their kinematics in order to understand their origins. Using a special-purpose instrument, the Planetary Nebula Spectrograph, we observe and extract PNe catalogues for these six systems*. We show that the PNe have the same spatial distribution as the starlight, that the numbers of them are consistent with what would be expected in a comparable old stellar population in elliptical galaxies, and that their kinematics join smoothly onto those derived at smaller radii from conventional spectroscopy. The high-quality kinematic observations presented here form an excellent set for studying the detailed kinematics of S0 galaxies, in order to unravel their formation histories. We find that PNe are good tracers of stellar kinematics in these systems. We show that the recovered kinematics are largely dominated by rotational motion, although with significant random velocities in most cases.