CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations IV. Testing warm dark matter cosmologies with galaxy scaling relations: A joint simulation-observation study using DREAMS simulations

TL;DR

This paper tests warm dark matter (WDM) cosmologies by linking galaxy scaling relations to cosmology, astrophysical feedback, and WDM mass using DREAMS simulations and SPARC/LVDB observations. It employs two simulation tiers—uniform-box and Milky Way–mass zoom-ins—and a bootstrap-based D^2 fitting approach to recover parameters, with calibration to mitigate resolution biases. The results show robust recovery of $\\Omega_m$, $\sigma_8$, and SN feedback strengths in the uniform-box runs, while the WDM mass is not constrained by these scaling relations at the current resolution; the Milky Way–scale zoom-ins reveal subtle WDM-induced trends at low stellar masses and a clear suppression of galaxy counts with lower $M_{ m WDM}$. The study highlights the value of multi-resolution simulations and diverse datasets to disentangle baryonic physics from DM properties, and points to galaxy abundance at the faint end and future surveys as promising avenues to improve WDM constraints.

Abstract

Small-scale discrepancies in the standard Lambda cold dark matter paradigm have motivated the exploration of alternative dark matter (DM) models, such as warm dark matter (WDM). We investigate the constraining power of galaxy scaling relations on cosmological, astrophysical, and WDM parameters through a joint analysis of hydrodynamic simulations and observational data. Our study is based on the DREAMS project and combines large-volume uniform-box simulations with high-resolution Milky Way zoom-in runs in a $Λ$WDM cosmology. To ensure consistency between the different simulation sets, we apply calibrations to account for resolution effects, allowing us to exploit the complementary strengths of the two suites. We compare simulated relations, including stellar size, DM mass and fraction within the stellar half-mass radius, and the total-to-stellar mass ratio, with two complementary galaxy samples: the SPARC catalog of nearby spirals and the LVDB catalog of dwarf galaxies in the Local Volume. Using a bootstrap-based fitting procedure, we show that key cosmological parameters ($Ω_m$, $σ_8$) and supernova feedback strength can be recovered with good accuracy, particularly from the uniform-box simulations. While the WDM particle mass remains unconstrained, the zoom-in simulations reveal subtle WDM-induced trends at low stellar masses in both the DM mass and total-to-stellar mass ratio. We also find that the galaxy stellar mass function exhibits a measurable dependence on the WDM particle mass below log10(M_*/Msun) <~ 8, which appears separable from the impact of feedback, suggesting it as a promising complementary probe. Our results highlight the importance of combining multi-resolution simulations with diverse observational datasets to jointly constrain baryonic processes and DM properties.

Figures (18)

• Figure 1: Median scaling relations as a function of total stellar mass illustrating the dependence on cosmological parameters. The relations for stellar half-mass radius, total-to-stellar mass ratio within the stellar half-mass radius, DM mass within the stellar half-mass radius, and total galaxy mass are shown for both uncalibrated (solid line) and calibrated (dashed line) cases. Trends were calculated using galaxies from 1024 uniform-box simulations divided into the following stellar mass intervals: $\rm log_{10} M_*/M_\odot<9.3$, $9.3\leq \rm log_{10} M_*/M_\odot<9.6$, $9.6\leq \rm log_{10} M_*/M_\odot<10.4$, $10.4\leq \rm log_{10} M_*/M_\odot<11.2$, and $\rm log_{10} M_*/M_\odot\geq 11.2$. Red and blue indicate trends for high and low parameter values, respectively, while the dashed gray line marks the threshold $N_{*,1/2} =50$. The thresholds and median values for the parameters are provided in Table \ref{['tab:thresholds']}. Error bars represent the scatter (16th–84th percentile range), while shaded areas indicate uncertainty estimates on the median values.
• Figure 2: Same as Fig. \ref{['fig: boxes cosm trend']}, but for the astrophysical parameters $A_{\rm SN1}$, $A_{\rm SN2}$, and $\rm BH_{\rm FF}$.
• Figure 3: Median scaling relations as a function of total stellar mass showing the dependence on astrophysical parameters and WDM mass for both MW zoom-in simulations (solid line) and calibrated uniform-box simulations (dashed line) for comparison. Trends are derived from 1024 MW zoom-in simulations divided into the following stellar mass intervals: $\rm log_{10} M_*/M_\odot<7.5$, $7.5\leq\rm log_{10} M_*/M_\odot<8.5$, $8.5\leq \rm log_{10} M_*/M_\odot<10$, and $\rm log_{10} M_*/M_\odot\geq10$. Red and blue indicate trends for high and low parameter values, respectively. The dashed gray line indicates $N_{*,1/2} = 50$.
• Figure 4: Differences between the median trends corresponding to the high and low values of two parameters: $A_{\rm SN1}$ (green) and $M_{\rm WDM}$ (brown). Solid lines represent MW zoom-in simulations; dashed lines represent uniform-box runs. Shaded regions show propagated uncertainties. The dashed gray line indicates $N_{*,1/2} = 50$.
• Figure 5: Median number of galaxies as a function of median total stellar mass computed in the stellar mass bins $\rm log_{10} M_*/M_\odot < 6.5$, $6.5 \leq\rm log_{10} M_*/M_\odot < 7.5$, $7.5\leq \rm log_{10} M_*/M_\odot < 8.5$, and $\rm log_{10} M_*/M_\odot \geq 8.5$. The four panels, from top to bottom, correspond to variations in $A_{\rm SN1}$, $A_{\rm SN2}$, $\rm BH_{\rm FF}$, and $M_{\rm WDM}$, respectively. In each case, the red and blue curves represent parameter values above and below the thresholds listed in Table \ref{['tab:thresholds']}, respectively. The plots are based on the 1024 MW zoom-in simulations from DREAMS.