Extraplanar emission in isolated edge-on late-type galaxies.II. The H$\alpha$ kinematics

TL;DR

This study examines the Hα kinematics of isolated edge-on late-type galaxies, revealing rotational lags in half the sample and suggesting external interactions with the circumgalactic medium as a key factor in their gas dynamics.

Contribution

It provides the first detailed analysis of Hα kinematics in a representative sample of isolated edge-on galaxies, highlighting the role of external interactions over internal processes.

Findings

Half of the galaxies show a rotational lag along the z-axis.

Lag magnitude is consistent with previous studies (~32 km/s/pc).

No direct link between lag and galaxy morphology, but possible correlation with tidal strength.

Abstract

Isolated galaxies are rare yet invaluable for studying secular evolution, as their physical properties can remain largely unaffected by external influences for several billion years, primarily shaped by internal evolutionary processes. This study focuses on a representative sample of nearly edge-on ($i\geq80^{\circ}$) late-type galaxies selected from the Catalogue of Isolated Galaxies (CIG). We analyse the H$\alpha$ kinematics derived from Fabry-Perot data and integrate these findings with a comprehensive examination of the UV, optical, and FIR properties of these galaxies to study their dynamic evolutionary processes. We investigate the individual kinematics by computing rotation curves and dynamical masses for each galaxy in the sample. The accuracy of our kinematic results is confirmed through comparisons with HI data and by applying the B- and K-band Tully-Fisher relationships. Among the galaxies studied, we observed a rotational lag along the $z$-axis in half of the total sample (7 out of 14 cases), with an average lag ($\Delta V/\Delta z=32.0\pm10.6\,{\rm km\,s^{-1}\,pc^{-1}}$) consistent with previous research findings. Notably, not all galaxies exhibiting measurable lag display morphological extraplanar components, leading us to conclude that this cannot serve as a definitive marker for the extraplanar Diffuse Ionized Gas (eDIG) component. While we found no significant correlations between rotation lag and overall galaxy properties, there seems to be a potential correlation with tidal strength. Based on the kinematic characteristics observed in our sample, we suggest that that the extended disc gas likely originates from interactions with the Circumgalactic Medium (CGM) rather than arising internally within the galaxies themselves.