arXiv subjects

Tibor Dome

Publications and source records attributed to Tibor Dome.

10 recordsLinked to original sources

arXiv2026

Halo mass functions in mixed cold and fuzzy dark matter models

We investigate the impact of mixed cold and fuzzy dark matter (MDM) cosmologies on the halo mass function (HMF) using numerical simulations performed with the AxiREPO framework. We consider models in which an ultralight axion-like component with mass $m =10^{-24.5} \mathrm{eV}$ constitutes a fraction $f \leq 0.3$ of the total dark matter. To enable consistent halo identification in mixed-species scenarios, we develop a grid-based halo-finding pipeline that combines the particle-based cold dark matter (CDM) and wave-like fuzzy dark matter (FDM) components into a unified density field. We find that FDM traces the large-scale CDM distribution while suppressing small-scale structure through wave interference effects, leading to a reduction in the abundance of low-mass haloes and modifying the HMF in a manner dependent on redshift and FDM fraction. Increasing the FDM fraction produces a systematic downward shift in the HMF and modifies its high-mass slope. Motivated by these trends, we introduce a phenomenological model that maps CDM HMFs to their MDM counterparts using a suppression function with parameters dependent on redshift and FDM fraction. This model reproduces the simulated HMFs within approximately 0.1 to 0.2 dex across the parameter space explored ($1 \leq z \leq 4$, $f \leq 0.3$). Our results provide a computationally efficient method for predicting structure formation in MDM cosmologies without requiring dedicated simulations for each parameter choice, and establish a framework for exploring the impact of MDM on cosmological structure formation.

astro-ph.CO↗

arXiv2026

The Impact of Fuzzy Dark Matter Dynamics on the Accumulation and Fragmentation of Primordial Gas

Fuzzy Dark Matter (FDM), particularly in the $10^{-22}$ eV mass regime is frequently used to characterize wave-like interference effects. It exhibits macroscopic wave properties, which drive distinct baryonic dynamics within collapsed haloes. Using the hydrodynamical code AREPO with the AxiREPO module and primordial chemistry, we simulate the assembly of haloes with masses $3 \times 10^{8} \le M_{\mathrm{h}} \le 8 \times 10^{9} \: M_\odot$ across a range of axion masses $1 \times 10^{-22} \le m_{\mathrm{a}} \le 7 \times 10^{-22}$ eV. We investigate how small-scale dynamics of the FDM density field affect the accumulation of cold, dense gas essential for primordial star formation. We demonstrate that gas collapse is suppressed by a two-fold mechanism: a delay driven by the geometry of the FDM solitonic core and a secondary dynamical barrier caused by stochastic wave fluctuations. While the flattened solitonic potential profile itself inhibits central gas accumulation, these wave-driven dynamics provide a further layer of disruption and angular momentum support, which in certain regimes prevents gas from reaching the central, compact, high-density configurations characteristic of CDM. Consequently, sites of star formation are shifted away from a single central peak toward a population of lower-mass clusters. Our work provides a physical framework for calibrating halo mass-dependent star formation efficiencies in FDM cosmologies, where internal processes may delay Cosmic Dawn beyond the effects of the initial power spectrum cut-off. These results are essential for interpreting realistic observational constraints from future 21-cm signal observations and the faint-end luminosity functions observed by the JWST, as well as providing an upper bound on the baryonic effects in the context of Mixed Dark Matter scenarios.

astro-ph.GA↗

arXiv2024

Increased Burstiness at High Redshift in Multi-Physics Models Combining Supernova Feedback, Radiative Transfer and Cosmic Rays

We study star formation variability, or burstiness, as a method to constrain and compare different galaxy formation models at high redshift using the Azahar simulation suite. The models range from magneto-hydrodynamics with a magneto-thermo-turbulent prescription for star formation (iMHD) to more sophisticated setups incorporating radiative transfer (RTiMHD) and cosmic ray physics (RTnsCRiMHD). Analysing a sample of galaxies at redshifts $z=4-10$, we find that the RTnsCRiMHD model exhibits more regular star formation periodicity compared to iMHD and RTiMHD, as revealed by the Lomb-Scargle periodogram. While the RTiMHD model captures a notable degree of stochasticity in star formation without cosmic rays, RTnsCRiMHD galaxies display even greater scatter in the burst intensity and in the scatter around the star-forming main sequence. To evaluate the burstiness in RTnsCRiMHD against observations, we generate a mock spectrum during a mini-quenching event at $z=7.5$. This spectrum aligns well with the low-mass quiescent galaxy JADES-GS-z7-01-QU observed at $z=7.3$, though some discrepancies attributed to stellar metallicity hint at a composite spectrum. Our findings highlight the importance of including complex physical processes like cosmic rays and radiative transfer in simulations to accurately capture the bursty nature of star formation in high-redshift galaxies. Future JWST observations, particularly regarding the scatter around the star-forming main sequence, have the potential to refine and guide the next generation of galaxy formation models.

astro-ph.GA↗

arXiv2024

Improved Halo Model Calibrations for Mixed Dark Matter Models of Ultralight Axions

We study the implications of relaxing the requirement for ultralight axions to account for all dark matter in the Universe by examining mixed dark matter (MDM) cosmologies with axion fractions $f \leq 0.3$ within the fuzzy dark matter (FDM) window $10^{-25}$ eV $\lesssim m \lesssim 10^{-23}$ eV. Our simulations, using a new MDM gravity solver implemented in AxiREPO, capture wave dynamics across various scales with high accuracy down to redshifts $z\approx 1$. We identify halos with Rockstar using the CDM component and find good agreement of inferred halo mass functions (HMFs) and concentration-mass relations with theoretical models across redshifts $z=1-10$. This justifies our halo finder approach a posteriori as well as the assumptions underlying the MDM halo model AxionHMcode. Using the inferred axion halo mass-cold halo mass relation $M_{\text{a}}(M_{\text{c}})$ and calibrating a generalised smoothing parameter $\alpha$ to our MDM simulations, we present a new version of AxionHMcode. The code exhibits excellent agreement with simulations on scales $k< 20 \ h$ cMpc$^{-1}$ at redshifts $z=1-3.5$ for $f\leq 0.1$ around the fiducial axion mass $m = 10^{-24.5}$ eV $ = 3.16\times 10^{-25}$ eV, with maximum deviations remaining below 10%. For axion fractions $f\leq 0.3$, the model maintains accuracy with deviations under 20% at redshifts $z\approx 1$ and scales $k< 10 \ h$ cMpc$^{-1}$, though deviations can reach up to 30% for higher redshifts when $f=0.3$. Reducing the run-time for a single evaluation of AxionHMcode to below $1$ minute, these results highlight the potential of AxionHMcode to provide a robust framework for parameter sampling across MDM cosmologies in Bayesian constraint and forecast analyses.

astro-ph.CO↗

arXiv2024

Linear rotor in an ideal Bose gas near the threshold for binding

We study a linear rotor in a bosonic bath within the angulon formalism. Our focus is on systems where isotropic or anisotropic impurity-boson interactions support a shallow bound state. To study the fate of the angulon in the vicinity of bound-state formation, we formulate a beyond-linear-coupling angulon Hamiltonian. First, we use it to study attractive, spherically symmetric impurity-boson interactions for which the linear rotor can be mapped onto a static impurity. The well-known polaron formalism provides an adequate description in this limit. Second, we consider anisotropic potentials, and show that the presence of a shallow bound state with pronounced anisotropic character leads to a many-body instability that washes out the angulon dynamics.

cond-mat.quant-gas↗

arXiv2023

Modeling Post-Reionization HI Distributions in Fuzzy Dark Matter Cosmologies Using Conditional Normalizing Flows

Upcoming 21 cm intensity mapping experiments like the Square Kilometer Array (SKA) hold significant potential to constrain the properties of dark matter. In this work, we model neutral hydrogen (HI) distributions using high-resolution hydrodynamical $N$-body simulations of both cold dark matter (CDM) and fuzzy dark matter (FDM) cosmologies in the post-reionization redshift range of $z=3.42-4.94$. We show that the HI abundance decreases in FDM-like cosmologies. Extreme FDM models with $m\sim 10^{-22}$ eV are at odds with a range of measurements. Due to the increased halo bias, the HI bias increases, paralleled by the damped Lyman-$α$ (DLA) bias which we infer from the cross-section of DLAs. The distribution of the latter in extreme FDM models has a high median at the low-mass end, which can be traced to the high column density of cosmic filaments. FDM models exhibit a very similar abundance of DLAs compared to CDM while sub-DLAs are already less abundant. We study the prospects of detecting the brightest HI peaks with SKA1-Low at $z=4.94$, indicating moderate signal-to-noise ratios (SNR) at angular resolution $θ_A = 2^{\prime}$ with a rapidly declining SNR for lower values of $θ_{A}$. After training the conditional normalizing flow network HIGlow on 2D HI maps, we interpolate its latent space of axion masses to predict the peak flux for a new, synthetic FDM cosmology, finding good agreement with expectations. This work thus underscores the potential of normalizing flows in capturing complex, non-linear structures within HI maps, offering a versatile tool for conditional sample generation and prediction tasks.

astro-ph.CO↗

arXiv2023

Mini-quenching of $z=4-8$ galaxies by bursty star formation

The recent reported discovery of a low-mass $z=5.2$ and an intermediate-mass $z=7.3$ quenched galaxy with JWST/NIRSpec is the first evidence of halted star formation above $z\approx 5$. Here we show how bursty star formation at $z=4-8$ gives rise to temporarily quenched, or mini-quenched galaxies in the mass range $M_{\star} = 10^7-10^9 \ M_{\odot}$ using four models of galaxy formation: the periodic box simulation IllustrisTNG, the zoom-in simulations VELA and FirstLight and an empirical halo model. The main causes for mini-quenching are stellar feedback, lack of gas accretion onto galaxies and galaxy-galaxy interactions. The abundance of (mini-)quenched galaxies agrees across the models: the population first appears below $z\approx 8$, after which their proportion increases with cosmic time, from $\sim 0.5-1.0$% at $z=7$ to $\sim 2-4$% at $z=4$, corresponding to comoving number densities of $\sim 10^{-5}$ Mpc$^{-3}$ and $\sim 10^{-3}$ Mpc$^{-3}$, respectively. These numbers are consistent with star formation rate duty cycles inferred for VELA and FirstLight galaxies. Their star formation histories (SFHs) suggest that mini-quenching at $z=4-8$ is short-lived with a duration of $\sim 20-40$ Myr, which is close to the free-fall timescale of the inner halo. However, mock spectral energy distributions of mini-quenched galaxies in IllustrisTNG and VELA do not match JADES-GS-z7-01-QU photometry, unless their SFHs are artificially altered to be more bursty on timescales of $\sim 40$ Myr. Studying mini-quenched galaxies might aid in calibrating sub-grid models governing galaxy formation, as these may not generate sufficient burstiness at high redshift to explain the SFH inferred for JADES-GS-z7-01-QU.

astro-ph.GA↗

arXiv2023

Cosmic Web Dissection in Fuzzy Dark Matter Cosmologies

On large cosmological scales, anisotropic gravitational collapse is manifest in the dark cosmic web. Its statistical properties are little known for alternative dark matter models such as fuzzy dark matter (FDM). In this work, we assess for the first time the relative importance of cosmic nodes, filaments, walls and voids in a cosmology with primordial small-scale suppression of power. We post-process $N$-body simulations of FDM-like cosmologies with varying axion mass $m$ at redshifts $z\sim 1.0-5.6$ using the NEXUS+ Multiscale Morphology Filter technique at smoothing scale $Δx = 0.04 \ h^{-1}$Mpc. The formation of wall and void halos is more suppressed than naively expected from the half-mode mass $M_{1/2}$. Also, we quantify the mass and volume filling fraction of cosmic environments and find that 2D cosmic sheets host a larger share of the matter content of the Universe as $m$ is reduced, with an $\sim 8-12$\% increase for the $m=7 \times 10^{-22}$ eV model compared to CDM. We show that in FDM-like cosmologies, filaments, walls and voids are cleaner and more pronounced structures than in CDM, revealed by a strong mid-range peak in the conditioned overdensity PDFs $P(δ)$. At high redshift, low-density regions are more suppressed than high-density regions. Furthermore, skewness estimates $S_3$ of the total overdensity PDF in FDM-like cosmologies are consistently higher than in CDM, especially at high redshift $z\sim 5.6$ where the $m=10^{-22}$ eV model differs from CDM by $\sim 6 σ$. Accordingly, we advocate for the usage of $P(δ)$ as a testbed for constraining FDM and other alternative dark matter models.

astro-ph.CO↗

arXiv2023

Cosmological Structure Formation and Soliton Phase Transition in Fuzzy Dark Matter with Axion Self-Interactions

We investigate cosmological structure formation in Fuzzy Dark Matter (FDM) with an attractive self-interaction (SI) with numerical simulations. Such a SI would arise if the FDM boson were an ultra-light axion, which has a strong CP symmetry-breaking scale (decay constant). Although weak, the attractive SI may be strong enough to counteract the quantum 'pressure' and alter structure formation. We find in our simulations that the SI can enhance small-scale structure formation, and soliton cores above a critical mass undergo a phase transition, transforming from dilute to dense solitons.

astro-ph.CO↗

arXiv2023

On the Cosmic Web Elongation in Fuzzy Dark Matter Cosmologies: Effects on Density Profiles, Shapes and Alignments of Halos

The fuzzy dark matter (FDM) scenario has received increased attention in recent years due to the small-scale challenges of the vanilla Lambda cold dark matter ($Λ$CDM) cosmological model and the lack of any experimental evidence for any candidate particle. In this study, we use cosmological $N$-body simulations to investigate high-redshift dark matter halos and their responsiveness to an FDM-like power spectrum cutoff on small scales in the primordial density perturbations. We study halo density profiles, shapes and alignments in FDM-like cosmologies (the latter two for the first time) by providing fits and quantifying departures from $Λ$CDM as a function of the particle mass $m$. Compared to $Λ$CDM, the concentrations of FDM-like halos are lower, peaking at an $m$-dependent halo mass and thus breaking the approximate universality of density profiles in $Λ$CDM. The intermediate-to-major and minor-to-major shape parameter profiles are monotonically increasing with ellipsoidal radius in $N$-body simulations of $Λ$CDM. In FDM-like cosmologies, the monotonicity is broken, halos are more elongated around the virial radius than their $Λ$CDM counterparts and less elongated closer to the center. Finally, intrinsic alignment correlations, stemming from the deformation of initially spherically collapsing halos in an ambient gravitational tidal field, become stronger with decreasing $m$. At $z\sim 4$, we find a $6.4 σ$-significance in the fractional differences between the isotropised linear alignment magnitudes $D_{\text{iso}}$ in the $m=10^{-22}$ eV model and $Λ$CDM. Such FDM-like imprints on the internal properties of virialised halos are expected to be strikingly visible in the high-$z$ Universe.

astro-ph.CO↗