A cosmologically motivated description of the dark matter halo profile for the Low Surface Brightness Galaxy, Malin 1

TL;DR

This study derives a mass profile for Malin 1, a low surface brightness galaxy, revealing a dark matter halo with adiabatic contraction and a baryon-dominated core, challenging typical LSB galaxy assumptions.

Contribution

It presents a detailed mass profile of Malin 1, showing a contracted dark matter halo and baryon dominance in the central region, which is novel for LSB galaxies.

Findings

Dark matter halo of Malin 1 shows adiabatic contraction.

Malin 1 is baryon dominated within 10 kpc.

Malin 1 aligns with normal galaxy rotation curve relations.

Abstract

In this paper we derive a possible mass profile for the low surface brightness galaxy, Malin 1, based upon previously published space-based and ground-based photometric properties and kinematics. We use properties of the bulge, normal disk, outer extended disk and \ion{H}{1} mass as inputs into mass profile models. We find that the dark matter halo model of Malin 1 is best described by a halo profile that has undergone adiabatic contraction, inconsistent with the findings for most disk galaxies to date, yet consistent with rotation curve studies of M31. More importantly, we find that Malin 1 is baryon dominated in its central regions out to a radius of $\sim10$ kpc (in the bulge region). Low-surface brightness galaxies are often referred to as being dark matter dominated at all radii. If this is the case, then Malin 1 would seem to have characteristics similar to those of normal barred disk galaxies, as suggested by other recent work. We also find that Malin 1 also falls on the rotation curve shear versus spiral arm pitch angle relation for normal galaxies, although more LSB galaxies need to be studied to determine if this is typical.