Establishing the level of cylindrical rotation in Boxy/Peanut bulges

TL;DR

This study uses integral-field spectroscopy and simulations to analyze the degree of cylindrical rotation in Boxy/Peanut bulges, confirming high rotation levels and proposing a new robust measurement method.

Contribution

It introduces a new method to quantify cylindrical rotation that is resistant to inner disk components and applies it to both observations and simulations.

Findings

High levels of cylindrical rotation in boxy/peanut bulges

Cylindrical rotation observed in some rounder bulges, likely barred galaxies viewed end-on

Milky Way bulge exhibits cylindrical rotation comparable to strong barred galaxies

Abstract

We present SAURON integral-field observations of a sample of 12 mid to high-inclination disk galaxies, to unveil hidden bars on the basis of their kinematics, i.e., the correlation between velocity and h3 profiles, and to establish their degree of cylindrical rotation. For the latter, we introduce a method to quantify cylindrical rotation that is robust against inner disk components. We confirm high-levels of cylindrical rotation in boxy/peanut bulges, but also observe this feature in a few galaxies with rounder bulges. We suggest that these are also barred galaxies with end-on orientations. Re-analysing published data for our own Galaxy using this new method, we determine that the Milky Way bulge is cylindrically rotating at the same level as the strongest barred galaxy in our sample. Finally, we use self-consistent three-dimensional N-body simulations of bar-unstable disks to study the dependence of cylindrical rotation on the bar's orientation and host galaxy inclination.