Accurate determination of the mass distribution in spiral galaxies III. Fabry-Perot imaging spectroscopy of 6 spiral galaxies

TL;DR

This study uses high-resolution Fabry-Perot spectroscopy to analyze the kinematics and rotation curves of six spiral galaxies, revealing differences between Halpha and HI data and highlighting the impact of beam smearing.

Contribution

It extends previous high-resolution galaxy studies to earlier types and provides detailed analysis of kinematics, including peculiar motions and beam smearing effects.

Findings

Halpha rotation curves are steeper than HI curves.

Beam smearing significantly affects velocity measurements at higher scale-length/beam-width ratios.

NGC 5055 exhibits peculiar central kinematics possibly due to a compact object.

Abstract

High resolution Fabry-Perot data of six spiral galaxies are presented. Those data extend the previous sample of spiral galaxies studied with high resolution 3D spectroscopy to earlier morphological types. All the galaxies in the sample have available HI data at 21 cm from the VLA or Westerbork. Velocity fields are analyzed and Halpha rotation curves are computed and compared to HI curves. The kinematics of NGC 5055 central regions are looked at more closely. Its peculiar kinematics can be interpreted either as a bipolar outflow or as a counter-rotating disk, possibly hosting a 9 pm 2 10^8 Msol compact object. Most of the Halpha rotation curves present a significantly steeper inner slope than their HI counterparts. The 21 cm data thus seems affected by moderate to strong beam smearing. The beam smearing has an effect at higher scale-length/beam-width than previously thought (up to 20 km/s at a ratio of 8.5).