Browsing by Author "Robson, Dylan"

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    Redshift evolution of galaxy group X-ray properties in the SIMBA simulations
    (Oxford University Press, 2023) Robson, Dylan; Dave, Romeel
    We examine the evolution of intragroup gas rest-frame X-ray scaling relations for group-sized haloes (M500 = 1012.3–1015 M) in the SIMBA galaxy formation simulation. X-ray luminosity LX versus M500 shows increasing deviation from self-similarity from z = 3 → 0, with M500 < 1013.5 M haloes exhibiting a large reduction in LX and slight increase in X-ray luminosity-weighted temperature TX. These shifts are driven by a strong drop in fgas with time for these haloes, and coincides with the onset of SIMBA’s black hole (BH) jet feedback, occurring when MBH > 107.5 M and Eddington ratio <0.2, in group haloes at z ∼ 1.5. The connection with BH feedback is corroborated by fBH ≡ MBH/M500 in M500 < 1013.5 M haloes being strongly anticorrelated with LX and fgas at z 1.5. This is further reflected in the scatter of LX − TX: haloes with small fBH lie near self-similarity, while those with the highest fBH lie furthest below. Turning off jet feedback results in mostly self-similar behaviour down to z = 0. For the X-ray weighted metallicity ZX, stellar feedback impacts the enrichment of halo gas. Finally, halo profiles show that jet feedback flattens the electron density and entropy profiles, and introduces a core in X-ray surface brightness, particularly at M500 < 1013.5 M. This argues that in SIMBA, intragroup X-ray evolution is largely driven by jet feedback removing hot gas from the cores of massive groups, and expelling gas altogether in less massive groups.
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    X-ray emission from hot gas in galaxy groups and clusters in SIMBA
    (Oxford University Press, 2020-08-31) Davé, Romeel; Robson, Dylan
    We examine X-ray scaling relations for massive haloes (M500 > 1012.3 M) in the SIMBA galaxy formation simulation. The X-ray luminosity, LX versus M500 has power-law slopes ≈5 3 and ≈8 3 above and below 1013.5 M, deviating from the self-similarity increasingly to low masses. TX − M500 is self-similar above this mass, and slightly shallower below it. Comparing SIMBA to observed TX scalings, we find that LX, LX-weighted [Fe/H], and entropies at 0.1R200 (S0.1) and R500 (S500) all match reasonably well. S500 − TX is consistent with self-similar expectations, but S0.1 − TX is shallower at lower TX, suggesting the dominant form of heating moves from gravitational shocks in the outskirts to non-gravitational feedback in the cores of smaller groups. SIMBA matches observations of LX versus central galaxy stellar mass M∗, predicting the additional trend that star-forming galaxies have higher LX(M∗). Electron density profiles for M500 > 1014 M haloes show a ∼0.1R200 core, but the core is larger at lower masses. TX are reasonably matched to observations, but entropy profiles are too flat versus observations for intermediate-mass haloes, with Score ≈ 200–400 keV cm2. SIMBA’s [Fe/H] profile matches observations in the core but overenriches larger radii. We demonstrate that SIMBA’s bipolar jet AGN feedback is most responsible for increasingly evacuating lower-mass haloes, but the profile comparisons suggest this may be too drastic in the inner regions.