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

Abstract

In this work we extend the study on the mass distribution of the spiral galaxy NGC 5278, performing 1D and 2D (GALFIT) 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 to the central active galactic nucleus and an exponential disk. We fix the stellar disk contribution to the rotation curve (RC) with broadband photometric observations and population synthesis models, to obtain the 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 the baryonic RC with more than and less than 30% disk mass (in order to consider the disk mass errors) to fit the entire RC. We perform the RC decomposition of NGC 5278 by considering the baryonic RC and four types of dark matter (DM) halo: Hernquist, Burkert, Navarro, Frenk, & White, and Einasto. Our results determine that the Hernquist DM halo better models our observed RC in the case of disk mass Md = 5.6 × 1010 M⊙ and also with less than 30% disk mass. In the case of more than 30% disk mass, the cored Einasto (n < 4) DM halo is the best-fitting model. © 2013. The American Astronomical Society. All rights reserved..