Disk Mass-to-Light ratio distribution from stellar population synthesis: Application to rotation curve decomposition of NGC 5278 (KPG 390A)

TL;DR

This study analyzes the mass distribution of NGC 5278 using stellar population synthesis and rotation curve decomposition, revealing that the galaxy lacks a bulge and that different dark matter halo models fit the data depending on disk mass assumptions.

Contribution

It introduces a detailed method combining photometry, population synthesis, and rotation curve analysis to determine the baryonic and dark matter distribution in NGC 5278, highlighting the variability of M/L ratios.

Findings

No bulge detected, only a bright source and exponential disk.

Constant M/L ratio assumption is invalid for NGC 5278.

Different dark matter halos fit the rotation curve depending on disk mass assumptions.

Abstract

In this work we extend the study on the mass distribution of the spiral galaxy NGC 5278, performing 1D and 2D bulge-disk decomposition to determine which components constitute the baryonic mass in this galaxy. Our analysis does not detect any bulge, instead we find a bright source, probably related with the central AGN, and an exponential disk. We fix the stellar disk contribution to the rotation curve (RC) with broad band photometric observations and population synthesis models, to obtain 2D mass distribution of the stellar disk. In the particular case of NGC 5278, we find that the typical assumption of considering the mass-to-luminosity ratio (M/L) of the disk as constant along the galactocentric radius is not valid. We also extract a baryonic RC from the mass profile, to determine the inability of this baryonic RC and also of the baryonic RC with more and less 30% disk mass (in order to consider the disk mass errors) to fit the entire RC. We perform the RC decomposition of NGC 5278 considering the baryonic RC and four types of dark matter halos: Hernquist; Burkert; Einasto and Navarro, Frenk & White. Our results show that Hernquist halo models better our observed RC in the case of determined disk mass ($M_d=5.6\times 10^{10}$ solar masses) and also with 30% less disk mass. In the case of 30% more disk mass the cored Einasto (n < 4) halo is the best fitting model.