Simulating jellyfish galaxies: a case study for a gas-rich dwarf galaxy
The Astrophysical Journal IOP Publishing 928:2 (2022) 144
Abstract:
We investigate the formation of jellyfish galaxies using radiation-hydrodynamic simulations of gas-rich dwarf galaxies with a multiphase interstellar medium (ISM). We find that the ram-pressure-stripped (RPS) ISM is the dominant source of molecular clumps in the near wake within 10 kpc from the galactic plane, while in situ formation is the major channel for dense gas in the distant tail of the gas-rich galaxy. Only 20% of the molecular clumps in the near wake originate from the intracluster medium (ICM); however, the fraction reaches 50% in the clumps located at 80 kpc from the galactic center since the cooling time of the RPS gas tends to be short owing to the ISM–ICM mixing (≲10 Myr). The tail region exhibits a star formation rate of 0.001–0.01 M⊙ yr−1, and most of the tail stars are born in the stripped wake within 10 kpc from the galactic plane. These stars induce bright Hα blobs in the tail, while Hα tails fainter than 6 × 1038 erg s−1 kpc−2 are mostly formed via collisional radiation and heating due to mixing. We also find that the stripped tails have intermediate X-ray-to-Hα surface brightness ratios (1.5 ≲ FX/FHα ≲ 20), compared to the ISM (≲1.5) or pure ICM (≫20). Our results suggest that jellyfish features emerge when the ISM from gas-rich galaxies is stripped by strong ram pressure, mixes with the ICM, and enhances the cooling in the tail.The effect of local universe constraints on halo abundance and clustering
(2022)
The NewHorizon simulation – to bar or not to bar
Monthly Notices of the Royal Astronomical Society Oxford University Press 512:1 (2022) 160-185
Abstract:
We use the NEWHORIZON simulation to study the redshift evolution of bar properties and fractions within galaxies in the stellar masses range M⋆ = 107.25–1011.4M⊙ over the redshift range of z = 0.25–1.3. We select disc galaxies using stellar kinematics as a proxy for galaxy morphology. We employ two different automated bar detection methods, coupled with visual inspection, resulting in observable bar fractions of fbar = 0.070+0.018−0.012 at z ∼ 1.3, decreasing to fbar = 0.011+0.014−0.003 at z ∼ 0.25. Only one galaxy is visually confirmed as strongly barred in our sample. This bar is hosted by the most massive disc and only survives from z = 1.3 down to z = 0.7. Such a low bar fraction, in particular amongst Milky Way-like progenitors, highlights a missing bars problem, shared by literally all cosmological simulations with spatial resolution <100 pc to date. The analysis of linear growth rates, rotation curves, and derived summary statistics of the stellar, gas and dark matter components suggest that galaxies with stellar masses below 109.5−1010M⊙ in NEWHORIZON appear to be too dominated by dark matter relative to stellar content to form a bar, while more massive galaxies typically have formed large bulges that prevent bar persistence at low redshift. This investigation confirms that the evolution of the bar fraction puts stringent constraints on the assembly history of baryons and dark matter on to galaxies.Momentum deposition of supernovae with cosmic rays
Monthly Notices of the Royal Astronomical Society Oxford University Press 511:1 (2022) 1247-1264
Abstract:
The cataclysmic explosions of massive stars as supernovae are one of the key ingredients of galaxy formation. However, their evolution is not well understood in the presence of magnetic fields or cosmic rays (CRs). We study the expansion of individual supernova remnants (SNRs) using our suite of 3D hydrodynamical (HD), magnetohydrodynamical (MHD) and CRMHD simulations generated using RAMSES. We explore multiple ambient densities, magnetic fields, and fractions of supernova energy deposited as CRs (χCR), accounting for CR anisotropic diffusion and streaming. All our runs have comparable evolutions until the end of the Sedov-Taylor phase. However, our CRMHD simulations experience an additional CR pressure-driven snowplough phase once the CR energy dominates inside the SNR. We present a model for the final momentum deposited by supernovae that captures this new phase: pSNR=2.87×105(χCR+1)4.82(ncm−3)−0.196M⊙ km s−1. Assuming a 10 per cent fraction of SN energy in CRs leads to a 50 per cent boost of the final momentum, with our model predicting even higher impacts at lower ambient densities. The anisotropic diffusion of CRs assuming an initially uniform magnetic field leads to extended gas and CR outflows escaping from the supernova poles. We also study a tangled initial configuration of the magnetic field, resulting instead in a quasi-isotropic diffusion of CRs and earlier momentum deposition. Finally, synthetic synchrotron observations of our simulations using the POLARIS code show that the local magnetic field configuration in the interstellar medium modifies the overall radio emission morphology and polarization.Catalogues of voids as antihaloes in the local Universe
Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press 511:1 (2022) L45-L49