Comments on the paper `Unifying Boxy Bulge and Planar Long Bar in the Milky Way' by Martinez-Valpuesta & Gerhard [arXiv:1105.0928]

TL;DR

This paper critiques a recent model proposing a single twisted bulge/bar in the Milky Way, arguing that it fails to explain certain observations better than the traditional bulge plus long bar model.

Contribution

It provides a critical comparison highlighting the limitations of the twisted bulge/bar model over the established bulge and long bar hypothesis.

Findings

The twisted bulge/bar model leaves some observational facts unexplained.

The traditional bulge + long bar model better accounts for certain features.

The authors favor the existing bulge and long bar interpretation.

Abstract

We comment on the recent paper by Martinez-Valpuesta & Gerhard (arXiv:1105.0928, 2011), who suggest, as an alternative to the bulge + long bar hypothesis in the inner 4 kpc of our Galaxy, a single boxy-bulge structure with a twisted major axis. In principle, we find this proposal acceptable; indeed, from a purely morphological point of view, this is more a question of semantics than science, and possibly all of us are talking about the same thing. However, we think that the particular features of this new proposal of a "single twisted bulge/bar" scenario leaves certain observational facts unexplained, whereas the model of a misaligned bulge + long bar successfully explains them.