The AIDA-TNG project: gas distributions inside and around haloes

TL;DR

This paper uses the AIDA-TNG hydrodynamical simulation suite to compare CDM, SIDM, vSIDM, and WDM models in terms of gas and HI distributions around haloes. It finds that median gas profiles are largely insensitive to the DM model, while HI shows model-dependent features, especially in the presence of AGN feedback, with SIDM1 producing larger central cores and greater HI retention in some massive halos. The authors forward-model Lyman-α and Lyman-β spectra and analyze the galaxy-Lyα cross-correlation to identify observable signatures, finding limited discrimination in many cases due to cosmic variance but notable potential in specific halo-mass/redshift regimes and with optimized sightline sampling. They propose halo-centered sightline sampling and quantify the observational requirements (e.g., ~160 halos with ~20 sightlines each) to distinguish DM models, highlighting the relevance for upcoming facilities and the feasibility of Lyα-based DM constraints.

Abstract

The nature of Dark Matter (DM) is one of the most outstanding mysteries of modern astrophysics. While the standard Cold DM (CDM) model successfully explains observations on most astrophysical scales, DM particles have not yet been detected, leaving room for a plethora of different models. In order to identify their observable signatures, we use the AIDA-TNG cosmological simulation suite to predict the distributions of gas and neutral hydrogen (HI) in the CDM, Self-Interacting DM (SIDM), velocity-dependent SIDM (vSIDM), and Warm DM (WDM) models. We find that the DM models investigated have very limited impact on the median gas and HI profile of haloes. In particular, for the most massive haloes ($M_{\rm vir}\sim10^{14}\,\mathrm{M}_\odot$), we find that DM self-interactions can shallow the central potential and thereby enhance gas cooling. We find that, in all models, the halo-to-halo variation in the HI profiles is explained by AGN feedback, and that the specific characteristics of DM model is largely subdominant. Nevertheless, we detect some systematic difference in the case of SIDM, with more HI surviving close to the centre with respect to other models. We provide fitting functions for the gas and HI profiles. We investigate the galaxy-Ly$α$ cross-correlation function (\galacc) for different halo masses, redshift and observation strategies. We find that at $z=0$ vSIDM can be distinguished from CDM in haloes with $10^{12}\lesssim M_{\rm vir}\lesssim10^{13}\,{\rm M}_\odot$, while SIDM1 can be distinguished from CDM in haloes with $M_{\rm vir}\gtrsim10^{13}\,{\rm M}_\odot$. We estimate that statistically-robust detection requires sampling $\sim160$ haloes with $\sim20$ sightlines each, a task that can be achieved with current and future facilities like WEAVE, 4MOST, PFS, ELT and WST.

Figures (12)

• Figure 1: The projected dark matter (top), total gas (middle), and HI (bottom) density for a halo with mass $M_{\rm vir} \approx 4.3 \times 10^{13}\,\rm M_\odot$ at $z=0$ in the 100/A full-physics runs. We show the same halo in the CDM, SIDM1, vSIDM, and WDM3 (from left to right respectively). The white dashed circle denotes the virial radius of the halo ($R_{\rm vir}\sim400\,\rm kpc/h$). Some small-scale differences can be appreciated between the DM models.
• Figure 2: Same as Fig. \ref{['fig:halo67_proj']}, but stacking of $100$ randomly selected haloes in mass range $\log_{10}M_{\rm vir} \in [12.9, 13.1)\,\rm M_\odot$ at $z=0$, from the 100/A full-physics runs. We use the same haloes for each DM model. The white dashed circle denotes the mean virial radius of the haloes in this bin ($\langle R_{\rm vir}\rangle \sim 273\,\rm kpc/h$). There are no clear differences between DM models.
• Figure 3: The median gas over-density profiles in different DM models, namely: CDM (black), SIDM1 (blue), vSIDM (green), and WDM3 (orange). In the lower part of each panel, we show the the ratio of each profile to the CDM case. Columns, from left to right, correspond to increasing redshifts in the range $z=0-5$. Each row corresponds to a different halo-mass bins, increasing from top to bottom. For the top two rows ($10^9,10^{10}\,\rm M_\odot$), we use haloes from the 50/A full-physics runs for better resolution while the rest use the haloes from the 100/A full-physics runs for larger halo samples. For each panel, we limit the maximum number of haloes employed to $5000$ for computational efficiency. The exact number of haloes used is reported in Table \ref{['tab:prof_numhalo']}. The grey band marks the average $68\%$ scatter about the mean profile, while the vertical hatched band shows the estimated resolution limit for the gas distribution in the simulation.
• Figure 4: Left panel: Gas core radius $r_\mathrm{c}$ as a function of redshift $z$, for haloes with virial mass $\sim10^{13}\,\rm M_\odot$ (solid lines) and $\sim10^{11}\,\rm M_\odot$ (dashed lines) for different DM modesls, namely: CDM (black), SIDM1 (blue), vSIDM (green), and WDM3 (orange). Right panel: Gas core radius $r_\mathrm{c}$ as a function of halo mass $M_{\rm vir}$, at $z=0$ (solid lines) and $z=2$ (dashed lines) for different DM modes. SIDM1 exhibits the largest central gas core, and core sizes in all models increase as redshift decreases. The HI profiles steepen towards lower redshift across all models, though SIDM1 and vSIDM remain slightly flatter.
• Figure 5: Same as Fig. \ref{['fig:GAS_profiles']} but for the HI content of haloes. The HI profiles appear less homogeneous across DM models than the total gas profiles.