The universal rotation curve of low surface brightness galaxies IV: the interrelation between dark and luminous matter

TL;DR

This study analyzes the rotation curves of low surface brightness galaxies to understand the interplay between dark and luminous matter, revealing a universal pattern and new scaling relations that connect their structural properties.

Contribution

It introduces a detailed mass modeling approach for LSB galaxies, highlighting the role of dark matter and proposing the stellar compactness as a key parameter in the universal rotation curve.

Findings

Dark matter dominates in less luminous LSB galaxies.

Dark matter halos have a consistent central surface density across galaxy types.

A new luminous parameter, stellar compactness, is essential for modeling rotation curves.

Abstract

We investigate the properties of the baryonic and the dark matter components in low surface brightness (LSB) disc galaxies, with central surface brightness in the B band $\mu_0 \geq 23 \, mag \, arcsec^{-2}$. The sample is composed by 72 objects, whose rotation curves show an orderly trend reflecting the idea of a universal rotation curve (URC) similar to that found in the local high surface brightness (HSB) spirals in previous works. This curve relies on the mass modelling of the coadded rotation curves, involving the contribution from an exponential stellar disc and a Burkert cored dark matter halo. We find that the dark matter is dominant especially within the smallest and less luminous LSB galaxies. Dark matter halos have a central surface density $\Sigma _0 \sim 100 \, M_{\odot} pc^{-2}$, similar to galaxies of different Hubble types and luminosities. We find various scaling relations among the LSBs structural properties which turn out to be similar but not identical to what has been found in HSB spirals. In addition, the investigation of these objects calls for the introduction of a new luminous parameter, the stellar compactness $C_*$ (analogously to a recent work by Karukes \& Salucci), alongside with the optical radius and the optical velocity in order to reproduce the URC. Furthermore, a mysterious entanglement between the properties of the luminous and the dark matter emerges.