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Register a new userFIGARO Simulation: FIlaments & GAlactic RadiO Simulation
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We produce the first low to mid frequency radio simulation that incorporates both traditional extragalactic radio sources as well as synchrotron cosmic web emission. The FIlaments & GAlactic RadiO (FIGARO) simulation includes ten unique SI{4x4}{degree} fields, incorporating active galactic nucleii (AGNs), star forming galaxies (SFGs) and synchrotron cosmic web emission out to a redshift of $z = 0.8$ and over the frequency range 100-1400 MHz. To do this, the simulation brings together a recent $100^3$ Mpc$^3$ magneto-hydrodynamic simulation (Vazza et al., 2019), calibrated to match observed radio relic population statistics, alongside updated `T-RECS code for simulating extragalactic radio sources (Bonaldi et al., 2019). Uniquely, the AGNs and SFGs are populated and positioned in accordance with the underlying matter density of the cosmological simulation. In this way, the simulation provides an accurate understanding of the apparent morphology, angular scales, and brightness of the cosmic web as well as -- crucially -- the clustering properties of the cosmic web with respect to the embedded extragalactic radio population. We find that the synchrotron cosmic web does not closely trace the underlying mass distribution of the cosmic web, but is instead dominated by shocked shells of emission surrounding dark matter halos and resembles a large, undetected population of radio relics. We also show that, with accurate kernels, the cosmic web radio emission is clearly detectable by cross-correlation techniques and this signal is separable from the embedded extragalactic radio population. We offer the simulation as a public resource towards the development of techniques for detecting and measuring the synchrotron cosmic web.
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A large portion of the baryons at low redshifts are still missing from detection. Most of the missing baryons are believed to reside in large scale cosmic filaments. Understanding the distribution of baryons in filaments is crucial for the search for missing baryons. We investigate the properties of cosmic filaments since $z=4.0$ in a cosmological hydrodynamic simulation, focusing on the density and temperature profiles perpendicular to the filament spines. Our quantitative evaluation confirm the rapid growth of thick and prominent filaments after $z=2$. We find that the local linear density of filaments shows correlation with the local diameter since $z=4.0$. The averaged density profiles of both dark matter and baryonic gas in filaments of different width show self-similarity, and can be described by an isothermal single-beta model. The typical gas temperature increases as the filament width increasing, and is hotter than $10^6$ K for filaments with width $D_{fil} gtrsim 4.0 rm{Mpc}$, which would be the optimal targets for the search of missing baryons via thermal Sunyaev-Zeldovich (SZ) effect. The temperature rises significantly from the boundary to the inner core regime in filaments with $D_{fil} gtrsim 4.0 rm{Mpc}$, probably due to heating by accretion shock, while the temperature rise gently in filaments with $D_{fil}< 4.0 rm{Mpc}$.
We present the study of gas phases around cosmic-web filaments detected in the TNG300-1 hydro-dynamical simulation at redshift z=0. We separate the gas in five different phases according to temperature and density. We show that filaments are essentially dominated by gas in the warm-hot intergalactic medium (WHIM), which accounts for more than 80% of the baryon budget at $r sim 1$ Mpc. Apart from WHIM gas, cores of filaments ($r<1$ Mpc) also host large contributions other hotter and denser gas phases, whose fractions depend on the filament population. By building temperature and pressure profiles, we find that gas in filaments is isothermal up to $r sim 1.5$ Mpc, with average temperatures of T_core = $4-13 times 10^5$ K, depending on the large scale environment. Pressure at cores of filaments is on average P_core = $4-12 times 10^{-7}$ keV/cm^3, which is ~1000 times lower than pressure measured in observed clusters. We also estimate that the observed Sunyaev-Zeldovich (SZ) signal from cores of filaments should range between $0.5 < y < 4.1 times 10^{-8}$, and these results are compared with recent observations. Our findings show that the state of the gas in filaments depend on the presence of haloes, and on the large scale environment.
We present a comprehensive study of the distribution of matter around different populations of filaments, using the IllustrisTNG simulation at z=0. We compute the dark matter (DM), gas, and stellar radial density profiles of filaments, and we characterise the distribution of the baryon fraction in these structures. We find that baryons exactly follow the underlying DM distribution only down to r~7 Mpc to the filament spines. At shorter distances (r<7 Mpc) the baryon fraction profile of filaments departs from the cosmic value Omega_b/Omega_m. While in the r~0.7 - 7 Mpc radial domain this departure is due to the radial accretion of WHIM gas towards the filament cores (creating an excess of baryons with respect to the cosmic fraction), the cores of filaments (r<0.7 Mpc) show instead a clear baryon depletion, quantified by a depletion factor of Y_b = 0.63-0.68. The analysis of the efficiency of AGN feedback events in filaments reveals that they are potentially powerful enough to eject gas outside of the gravitational potential wells of filaments. We show that the large-scale environment (i.e. denser vs less-dense, hotter vs colder regions) has a non-negligible effect on the absolute values of the DM, gas, and stellar densities around filaments. Nevertheless, the relative distribution of baryons with respect to the underlying DM density field is found to be independent from the filament population. Finally, we provide scaling relations between gas density, temperature, and pressure for the different populations of cosmic filaments. We compare these relations to those pertaining to clusters of galaxies, and find that these cosmic structures occupy separate regions of the density-temperature and density-pressure planes.
The fragmentation of filaments in molecular clouds has attracted a lot of attention as there seems to be a relation between the evolution of filaments and star formation. The study of the fragmentation process has been motivated by simple analytical models. However, only a few comprehensive studies have analysed the evolution of filaments using numerical simulations where the filaments form self-consistently as part of molecular clouds. We address the early evolution of pc-scale filaments that form within individual clouds. We focus on three questions: How do the line masses of filaments evolve? How and when do the filaments fragment? How does the fragmentation relate to the line masses of the filaments? We examine three simulated molecular clouds formed in kpc-scale numerical simulations performed with the FLASH code. We compare the properties of the identified filaments with the predictions of analytic filament stability models. The line masses and mass fraction enclosed in the identified filaments increase continuously after the onset of self-gravity. The first fragments appear early when the line masses lie well below the critical line mass of Ostrikers hydrostatic equilibrium solution. The average line masses of filaments identified in 3D density cubes increases far more quickly than those identified in 2D column density maps. Our results suggest that hydrostatic or dynamic compression from the surrounding cloud has a significant impact on the early dynamical evolution of filaments. A simple model of an isolated, isothermal cylinder may not provide a good approach for fragmentation analysis. Caution must be exercised in interpreting distributions of properties of filaments identified in column density maps, especially in the case of low-mass filaments. Comparing or combining results from studies that use different filament finding techniques is strongly discouraged.
Context. Gravitational collapse theory and numerical simulations suggest that the velocity field within large-scale galaxy filaments is dominated by motions along the filaments. Aims. Our aim is to check whether observational data reveal any preferred orientation of galaxy pairs with respect to the underlying filaments as a result of the expectedly anisotropic velocity field. Methods. We use galaxy pairs and galaxy filaments identified from the Sloan Digital Sky Survey data. For filament extraction, we use the Bisous model that is based the marked point process technique. During the filament detection, we use the centre point of each pair instead of the positions of galaxies to avoid a built-in influence of pair orientation on the filament construction. For pairs lying within filaments (3012 cases), we calculate the angle between the line connecting galaxies of each pair and their host filament. To avoid redshift-space distortions, the angle is measured in the plain of the sky. Results. The alignment analysis shows that the orientation of galaxy pairs correlates strongly with their host filaments. The alignment signal is stronger for loose pairs, with at least 25% excess of aligned pairs compared to a random distribution. The alignment of galaxy pairs and filaments measured from the observational data is in good concordance with the alignment in the Millennium simulation and thus provides support to the {Lambda}CDM formalism.
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