Detection of non-ordered central gas motions in a sample of four low surface brightness galaxies

TL;DR

This study uses integral-field spectroscopy to analyze ionized gas motions in four low surface brightness galaxies, revealing significant non-ordered motions that complicate mass density profile determinations.

Contribution

It demonstrates the prevalence of non-ordered gas motions in low surface brightness galaxies, impacting the accuracy of central mass density slope measurements.

Findings

Three out of four galaxies show strong non-ordered gas motions.

Non-ordered motions hinder distinguishing between cuspy and core density profiles.

Regular velocity field observed only in one galaxy.

Abstract

We present integral-field spectroscopy of the ionized gas in the central regions of four galaxies with a low surface brightness disk taken with the Visible Multi Object Spectrograph at the Very Large Telescope and aimed at testing the accuracy in the determination of the central logarithmic slope $\alpha$ of the mass density radial profile $\rho(r) \propto r^\alpha$ in this class of objects. For all the sample galaxies we subtracted from the observed velocity field the best-fit model of gas in circular motions and derived the residuals. Only ESO-LV 5340200 is characterized by a regular velocity field. We extracted the velocity curves of this galaxy along several position angles, in order to estimate the uncertainty in deriving the central gradient of the total mass density from long-slit spectroscopy. We report the detection of strong non-ordered motions of the ionized gas in three out of four sample galaxies. The deviations have velocity amplitudes and spatial scales that make not possible to disentangle between cuspy and core density radial profiles.