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Cosmic evolution of stellar quenching by AGN feedback: clues from the Horizon-AGN simulation
Beckmann, R. S.,Devriendt, J.,Slyz, A.,Peirani, S.,Richardson, M. L. A.,Dubois, Y.,Pichon, C.,Chisari, N. E.,Kaviraj, S.,Laigle, C.,Volonteri, M. Oxford University Press 2017 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.472 No.1
<P>The observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard Lambda cold dark matter paradigm. In this paper, we investigate the impact of active galactic nuclei (AGN) feedback on star formation in massive galaxies. We isolate the impact of AGN by comparing two simulations from the HORIZON suite, which are identical except that one also includes supermassive black holes (SMBHs) and related feedback models. This allows us to cross-identify individual galaxies between simulations and quantify the effect of AGN feedback on their properties, including stellar mass and gas outflows. We find that massive galaxies (M-* >= 10(11) M-circle dot) are quenched by AGN feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. SMBHs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 10(9) M-circle dot <= M-* <= 10(11) M-circle dot, and a disruption of central gas inflows, which limits in situ star formation. As a result, net gas inflows on to massive galaxies, M-* >= 10(11) M-circle dot, drop by up to 70 per cent. We measure a redshift evolution in the stellar mass ratio of twin galaxies with and without AGN feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. This evolution is driven by a progressive flattening of the M-SMBH-M-* relation with redshift, particularly for galaxies with M-* <= 10(10) M-circle dot. M-SMBH/M-* ratios decrease over time, as falling average gas densities in galaxies curb SMBH growth.</P>
Implications of strong intergalactic magnetic fields for ultrahigh-energy cosmic-ray astronomy
Alves Batista, Rafael,Shin, Min-Su,Devriendt, Julien,Semikoz, Dmitri,Sigl, Guenter American Physical Society 2017 Physical review. D Vol.96 No.2
<P>We study the propagation of ultrahigh-energy cosmic rays in the magnetized cosmic web. We focus on the particular case of highly magnetized voids (B similar to nG), using the upper bounds from the Planck satellite. The cosmic web was obtained from purely magnetohydrodynamical cosmological simulations of structure formation considering different power spectra for the seed magnetic field in order to account for theoretical uncertainties. We investigate the impact of these uncertainties on the propagation of cosmic rays, showing that they can affect the measured spectrum and composition by up to. similar or equal to 80% and. similar or equal to 5%, respectively. In our scenarios, even if magnetic fields in voids are strong, deflections of 50 EeV protons from sources closer than similar to 50 Mpc are less than 15 degrees in approximately 10-50% of the sky, depending on the distribution of sources and magnetic power spectrum. Therefore, UHECR astronomy might be possible in a significant portion of the sky depending on the primordial magnetic power spectrum, provided that protons constitute a sizeable fraction of the observed UHECR flux.</P>
Gas flows in the circumgalactic medium around simulated high-redshift galaxies
Mitchell, Peter D,Blaizot, Jé,ré,my,Devriendt, Julien,Kimm, Taysun,Michel-Dansac, Lé,o,Rosdahl, Joakim,Slyz, Adrianne Blackwell Publishing Ltd 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.474 No.4