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

TL;DR

This study analyzes dark matter content in a large sample of nearby late-type galaxies by comparing dynamical masses $M_{\text{Dyn}}$ with stellar masses $M_{\text{Stellar}}$ derived from eight SPS models and seven dynamical estimators calibrated against rotation curves. By employing quasi-constant mass and redshift bins, the authors mitigate selection effects and reveal a complex dependence of the mass difference $\Delta \log M$ on both dynamical mass and redshift, with a saddle-like pattern at low mass evolving into a linear, DM-influenced trend at higher masses and redshifts. The results indicate that DM within LTGs is at most as large as $\Delta \log M$, subject to IMF and SPS choices, and that higher redshift LTGs are more baryon-dominated, consistent with local Milky Way–Andromeda benchmarks. Overall, the work demonstrates a continuous morphological transition in DM contribution from disk- to bulge-dominated LTGs and emphasizes the need to account for IMF variations and baryonic mass in mass-budget studies of galaxy evolution.

Abstract

Using a sample of $\sim$126,000 late-type galaxies (LTGs) from SDSS, we analyzed stellar mass as a function of dynamical mass. Stellar masses were estimated using eight SPS models with constant IMFs, while dynamical masses were derived from seven formulations based on Newtonian dynamics and virial equilibrium, incorporating both stellar and gas velocity dispersions. We account for key factors affecting dynamical mass estimation, including inclination, colour, concentration, and Sérsic index. We find that the difference between dynamical and stellar mass ($Δ\log \mathbf{M}$) ranges from nearly zero to $\sim$95% of the dynamical mass, depending on mass and redshift. $Δ\log \mathbf{M}$ appears to decreases with increasing redshift, but exhibits a saddle-like shape at low mass and low redshift-especially in disk-dominated LTGs-transitioning into a steep, linear trend at higher masses and redshifts. In the high-mass regime, the behavior resembles that of early-type galaxies. Moreover, our results indicate that this evolution is not discrete but follows a continuous transition between morphological regimes. Dark matter within LTGs is at most equal to $Δ\log \mathbf{M}$, 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($\mathbf{M_{Stellar}/M_{Solar}}) > 10$ at $z \leq 0.3$ are predominantly stellar-mass dominated. Most galaxies in our sample fall within this regime, minimizing the impact of gas exclusion. Our findings go beyond the scope of single galaxies, providing insight into the nearby Universe and highlighting the influence of dark matter in determining the Universe's structure and evolution.

Figures (31)

• Figure 1: Color $g$-$r$ distribution of the sample of 126,815 LTGs used in this work.
• Figure 2: Concentration index (R90/R50) distribution of the sample of 126,815 LTGs used in this work.
• Figure 3: Sérsic index ($n$) distribution of the sample of 126,815 LTGs used in this work.
• Figure 4: Behavior of stellar mass $({\bf M_{ED}})$ as function of redshift for quasi-constant dynamical mass. Each colour and symbol represents quasi-constant dynamical mass. The lower-left part of the graph (black dots) corresponds to $\log({\bf M_{Dyn}/{\bf M_{Solar}}})$$\sim$ 10.30 while the upper-right part of the graph (blue triangles) corresponds to $\log({\bf M_{Dyn}/{\bf M_{Solar}}})$$\sim$ 11.80. The difference in $\log({\bf M_{Dyn}/{\bf M_{Solar}}})$ between consecutive symbols is approximately 0.5. The mean uncertainty of the $\log({\bf M_{ED}/{\bf M_{Solar}}})$ is approximately 0.062 dex.
• Figure 5: Difference between dynamical and stellar mass ($\Delta {\bf log M_{(Dyn - ED)}}$ = $\log({\bf M_{Dyn}/{\bf M_{Solar}}})$ - $\log({\bf M_{ED}/{\bf M_{Solar}}})$) as function of dynamical mass for the LTGs samples. Each row corresponds to a specific estimation of dynamical mass ($\mathbf{M_{KS}}$, $\mathbf{M_{KA}}$, $\mathbf{M_{KB}}$, $\mathbf{M_{nS}}$, $\mathbf{M_{IS}}$, $\mathbf{M_{IA}}$, $\mathbf{M_{IB}}$). Each colour and symbol represents a quasi-constant redshift. The difference in redshift between consecutive symbols is approximately 0.01. The mean uncertainty of the difference between $\log({\bf M_{Dyn}/{\bf M_{Solar}}})$ and $\log({\bf M_{ED}/{\bf M_{Solar}}})$ is approximately 0.280 dex. The left column of the mosaic contains the full range of redshift, while the right column only contains three specific redshifts: low (black dots $z \sim 0.025$), intermediate (purple squares $z \sim 0.095$), and high ( dark green triangles $z \sim 0.165$), the latter with the aim of appreciating more clearly the differences in dynamical and stellar masses due to redshift and also to display the uncertainties for each point.