Mapping the inner regions of the polar disk galaxy NGC4650A with MUSE

TL;DR

This study uses MUSE observations to produce the first detailed 2D kinematic map of NGC4650A's inner regions, revealing the coexistence of two distinct disks and informing its formation history.

Contribution

It provides the first 2D velocity and dispersion maps of NGC4650A's central regions, demonstrating the galaxy's structure as two perpendicular disks and modeling its mass distribution.

Findings

The galaxy consists of two distinct, perpendicular disks with complex kinematics.

A multicomponent mass model successfully reproduces the observed kinematics.

Results support formation via accretion of material with different angular momentum.

Abstract

[abridged] The polar disk galaxy NGC4650A was observed during the commissioning of the MUSE at the ESO VLT to obtain the first 2D map of the velocity and velocity dispersion for both stars and gas. The new MUSE data allow the analysis of the structure and kinematics towards the central regions of NGC4650A, where the two components co-exist. These regions were unexplored by the previous long-slit literature data available for this galaxy. The extended view of NGC~4650A given by the MUSE data is a galaxy made of two perpendicular disks that remain distinct and drive the kinematics right into the very centre of this object. In order to match this observed structure for NGC4650A, we constructed a multicomponent mass model made by the combined projection of two disks. By comparing the observations with the 2D kinematics derived from the model, we found that the modelled mass distribution in these two disks can, on average, account for the complex kinematics revealed by the MUSE data, also in the central regions of the galaxy where the two components coexist. This result is a strong constraint on the dynamics and formation history of this galaxy; it further supports the idea that polar disk galaxies like NGC~4650A were formed through the accretion of material that has different angular momentum.