5 research outputs found

    Relative baryon-dark matter velocities in cosmological zoom simulations

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    Supersonic relative motion between baryons and dark matter due to the decoupling of baryons from the primordial plasma after recombination affects the growth of the first small-scale structures. Large box sizes (greater than a few hundred Mpc) are required to sample the full range of scales pertinent to the relative velocity, while the effect of the relative velocity is strongest on small scales (less than a few hundred kpc). This separation of scales naturally lends itself to the use of `zoom' simulations, and here we present our methodology to self-consistently incorporate the relative velocity in zoom simulations, including its cumulative effect from recombination through to the start time of the simulation. We apply our methodology to a large-scale cosmological zoom simulation, finding that the inclusion of relative velocities suppresses the halo baryon fraction by 4646--2323 per cent between z=13.6z=13.6 and 11.211.2, in qualitative agreement with previous works. In addition, we find that including the relative velocity delays the formation of star particles by 20 Myr\sim 20 {~\rm Myr} Myr on average (of the order of the lifetime of a 9 M\sim 9~{\rm M}_\odot Population III star) and suppresses the final stellar mass by as much as 7979 per cent at z=11.2z=11.2.Comment: 14 pages, 12 figures. Accepted for publication in MNRA

    The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a new fully-coupled radiation-hydrodynamical simulation of the Epoch of Reionization

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    International audienceRecent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at z=6\rm z=6 are lower than many theoretical predictions. In order to gain insight, we investigate the evolution of the mfp in our new massive fully coupled radiation hydrodynamics cosmological simulation of reionization: Cosmic Dawn III (CoDa III). CoDa III's scale (943cMpc3\rm 94^3 \, cMpc^3) and resolution (81923\rm 8192^3 grid) make it particularly suitable to study the IGM during reionization. The simulation was performed with RAMSES-CUDATON on Summit, and used 131072 processors coupled to 24576 GPUs, making it the largest reionization simulation, and largest ever RAMSES simulation. A superior agreement with global constraints on reionization is obtained in CoDa III over CoDa II, especially for the evolution of the neutral hydrogen fraction and the cosmic photo-ionization rate, thanks to an improved calibration, later end of reionization (z=5.6\rm z=5.6), and higher spatial resolution. Analyzing the mfp, we find that CoDa III reproduces the most recent observations very well, from z=6\rm z=6 to z=4.6\rm z=4.6. We show that the distribution of the mfp in CoDa III is bimodal, with short (neutral) and long (ionized) mfp modes, due to the patchiness of reionization and the co-existence of neutral versus ionized regions during reionization. The neutral mode peaks at sub-kpc to kpc scales of mfp, while the ionized mode peak evolves from 0.1Mpc/h\rm 0.1 Mpc/h at z=7\rm z=7 to ~10 Mpc/h at z=5.2\rm z=5.2. Computing the mfp as the average of the ionized mode provides the best match to the recent observational determinations. The distribution reduces to a single neutral (ionized) mode at z>13\rm z>13 (z<5\rm z<5)

    The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a new fully-coupled radiation-hydrodynamical simulation of the Epoch of Reionization

    No full text
    Recent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at z=6\rm z=6 are lower than many theoretical predictions. In order to gain insight into this issue, we investigate the evolution of the mfp in our new massive fully coupled radiation hydrodynamics cosmological simulation of reionization: Cosmic Dawn III (CoDaIII). CoDaIII's scale (943cMpc3\rm 94^3 \, cMpc^3) and resolution (81923\rm 8192^3 grid) make it particularly suitable to study the evolution of the IGM during the Epoch of Reionization (EoR). The simulation was performed with RAMSES-CUDATON on Summit, and used 131072 processors coupled to 24576 GPUs, making it the largest EoR simulation, and largest RAMSES simulation ever performed. A superior agreement with global constraints on reionization is obtained in CoDaIII over CoDaII especially for the evolution of the neutral hydrogen fraction and the cosmic photo-ionization rate, thanks to an improved calibration, later end of reionization (z=5.6\rm z=5.6), and higher spatial resolution. Analyzing the mfp, we find that CoDaIII reproduces the most recent observations very well, from z=6\rm z=6 to z=4.6\rm z=4.6. We show that the distribution of the mfp in CoDaIII is bimodal, with short (neutral) and long (ionized) mfp modes, respectively, due to the patchiness of reionization and the co-existence of neutral versus ionized regions during the EoR. The neutral mode peaks at sub-kpc to kpc scales of mfp, while the ionized mode peak evolves from 0.1Mpc/h\rm 0.1 Mpc/h at z=7\rm z=7 to 10\sim 10 Mpc/h at z=5.2\rm z=5.2. Computing the mfp as the average of the ionized mode provides the best match to the recent observational determinations. The distribution reduces to a single neutral (ionized) mode at z>13\rm z>13 (z<5\rm z<5)
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