Tracing Galaxy Evolution in the Nearby Universe: The Role of Dark Matter

TL;DR

This study analyzes the relationship between stellar and dynamical masses in late-type galaxies, revealing how dark matter's role varies with galaxy mass and redshift, and providing insights into galaxy evolution and baryon dominance.

Contribution

It offers a comprehensive analysis of dark matter's influence in late-type galaxies across different masses and redshifts, incorporating multiple mass estimation models and accounting for key observational factors.

Findings

Dark matter contribution varies with galaxy mass and redshift.

More massive and higher-redshift galaxies are increasingly baryon-dominated.

Dark matter within late-type galaxies is at most equal to the difference between dynamical and stellar mass.

Abstract

Using a sample of 126000 late-type galaxies from the SDSS, we analyzed stellar mass as a function of the dynamical mass. Stellar masses are estimated using eight stellar population synthesis (SPS) models with constant IMF, while dynamical masses are derived from seven formulations based on Newtonian dynamics and virial equilibrium, incorporating both stellar and gas velocity dispersions. We account for key factors affecting mass estimation, including inclination, color, concentration, and S\'ersic index. The difference between dynamical and stellar mass (Delta log(M)) ranges from nearly zero to 95% of the dynamical mass, depending on mass and redshift, decreasing with increasing redshift, exhibiting a saddlelike trend at low mass and low redshift -- especially in disk-dominated LTGs, and transitioning into a steep, linear trend at higher masses and redshifts. This trend is not discrete but follows a continuous transition between morphological regimes. In the high-mass regime, the behavior resembles that of early-type galaxies. More massive or higher-redshift LTGs seem to be increasingly baryon-dominated, likely reflecting efficient baryon aggregation in compact, gas-rich early-Universe galaxies, less concentrated dark matter halos at high redshift, and dynamic gas inflows that concentrate baryons in galaxy centers, diminishing the dynamical role of dark matter. Dark matter within LTGs is at most equal to Delta log(M), depending on the impact of the IMF and SPS on stellar mass estimation. Although SPS-based stellar masses do not include the gas component, previous studies have shown that galaxies with log(M_Stellar/M_Solar) > 10 at z <= 0.3 are predominantly stellar-mass dominated, indicating that our sample mass estimates have minimal impact from gas exclusion. The results provide insight into the role of dark matter in determining galaxies' structure and evolution in the nearby Universe.