Bimodality of low-redshift circumgalactic O vi in non-equilibrium eagle zoom simulations

Oppenheimer, Benjamin D.; Crain, Robert A.; Schaye, Joop; Rahmati, Alireza; Richings, Alexander J.; Trayford, James W.; Tumlinson, Jason; Bower, Richard G.; Schaller, Matthieu; Theuns, Tom

doi:10.1093/mnras/stw1066

Cited by 213 publications

(315 citation statements)

References 124 publications

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“…The central requirement for a significant PZF effect is therefore that the star-forming galaxy hosted an active AGN within a timescale comparable to the recombination time of a high metal ion, which for circumgalactic O vi is of the order of 10 7 years. We vary AGN lifetimes, luminosities, duty cycle fractions, and isotropy in an EAGLE zoom simulation of a typical star-forming galaxy using the non-equilibrium module introduced in Oppenheimer et al (2016) with the addition of a spatially and time variable AGN field 3 . Our focus is to investigate whether an AGN can reproduce the strong O vi around star-forming galaxies observed by COS-Halos while having an evolutionarily sustainable SMBH growth rate and a small duty cycle fraction so that most galaxies appear as inactive AGN.…”

Section: Discussionmentioning

confidence: 99%

Flickering AGN can explain the strong circumgalactic O viobserved by COS-Halos

Oppenheimer¹,

Segers

Schaye

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Proximity zone fossils (PZFs) are ionization signatures around recently active galactic nuclei (AGN) where metal species in the circumgalactic medium remain overionized after the AGN has shut-off due to their long recombination timescales. We explore cosmological zoom hydrodynamic simulations using the EAGLE model paired with a non-equilibrium ionization and cooling module including time-variable AGN radiation to model PZFs around star-forming, disk galaxies in the z ∼ 0.2 Universe. Previous simulations typically under-estimated the O vi content of galactic haloes, but we show that plausible PZF models increase O vi column densities by 2 − 3× to achieve the levels observed around COS-Halos star-forming galaxies out to 150 kpc. Models with AGN bolometric luminosities 10 43.6 erg s −1 , duty cycle fractions 10%, and AGN lifetimes 10 6 yr are the most promising, because their supermassive black holes grow at the cosmologically expected rate and they mostly appear as inactive AGN, consistent with COS-Halos. The central requirement is that the typical star-forming galaxy hosted an active AGN within a timescale comparable to the recombination time of a high metal ion, which for circumgalactic O vi is ≈ 10 7 years. H i, by contrast, returns to equilibrium much more rapidly due to its low neutral fraction and does not show a significant PZF effect. O vi absorption features originating from PZFs appear narrow, indicating photo-ionization, and are often well-aligned with lower metal ion species. PZFs are highly likely to affect the physical interpretation of circumgalactic high ionization metal lines if, as expected, normal galaxies host flickering AGN.

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Section: Discussionmentioning

confidence: 99%

Flickering AGN can explain the strong circumgalactic O viobserved by COS-Halos

Oppenheimer¹,

Segers

Schaye

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…Meanwhile, a significant computational effort is underway by cosmological simulators to understand the origin of oxygen in the hot circumgalactic gas: Stinson et al (2013);Suresh, et al (2015); Liang, Kravtsov & Agertz (2016); Roca-Fabrega et al (2016);Oppenheimer, et al (2016); Sokolowska et al (2016) etc. In these studies most of the circumgalactic oxygen is provided by supernova-driven galactic winds from the central galaxy.…”

Section: Introductionmentioning

confidence: 99%

“…From this we construct several approximate atmospheres distorted by increasing amounts of feedback heating which must be maintained by continued feed- gas density profiles. Orange line: L ne(r) profile for 50 < r < 240 kpc from Oppenheimer et al (2016). (c) dark halo (dashed line) and cumulative gas mass profiles in M .…”

Section: Introductionmentioning

confidence: 99%

Circumgalactic Oxygen Absorption and Feedback

Mathews

Prochaska

2017

ApJL

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OVI absorption in quasar spectra caused by intervening circumgalactic atmospheres suggests a downturn in the atmospheric column density in sightlines passing beyond about 100 kpc from central star-forming galaxies. This turnover supports the hypothesis that the oxygen originates in the central galaxies. When converted into oxygen space density using an Abel integral inversion, the OVI columns require > ∼ 10 9 M of oxygen concentrated near 100 kpc. Circumgalactic gas within this radius cools in less than 1 Gyr and radiates ∼ 10 42.2 erg s −1 overall. The feedback power necessary to maintain such oxygen-rich atmospheres for many Gyrs cannot be easily supplied by galactic supernovae. However, massive central black holes in star-forming galaxies may generate sufficient accretion power and intermittent shock waves at r ∼ 100 kpc to balance circumgalactic radiation losses in late-type L galaxies. The relative absence of OVI absorption observed in early-type, passive L galaxies may arise from enhanced AGN feedback from their more massive central black holes.

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“…Recently, Oppenheimer et al (2016) used the EAGLE simulations to compare the column density of various oxygen ionisation states as a function of halo mass and found that the presence and strength of O VI absorption are strongly related to the mass of the halo. Halos of sub-L * galaxies contain little O VI absorption because the virial temperature is too low to ionise oxygen to such a high state.…”

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confidence: 99%

“…They find that oxygen is more likely to exist as O VII and O VIII for more massive halos, in particular, halos significantly larger than L * . To investigate the simulation predictions from Oppenheimer et al (2016) and compare to Mg II and CIV absorption results, we use two O VI samples, one which contains only isolated galaxies and the other contains galaxies in group environments. The isolated sample, which represents L * galaxies, has been presented in the "Multiphase Galaxy Halos" survey Muzahid et al 2015Muzahid et al , 2016Nielsen et al 2017).…”

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confidence: 99%

The Impact of the Group Environment on the O vi Circumgalactic Medium

Pointon

Nielsen

Kacprzak

et al. 2017

ApJ

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We present a study comparing O VI λλ1031, 1037 doublet absorption found towards group galaxy environments with that of isolated galaxies. The O VI absorption in the circumgalactic medium (CGM) of isolated galaxies has been studied previously by the "Multiphase Galaxy Halos" survey, where the kinematics and absorption properties of the CGM have been investigated. We extend these studies to group environments. We define a galaxy group to have two or more galaxies having a line-of-sight velocity difference of no more than 1000 km s −1 and located within 350 kpc (projected) of a background quasar sightline. We identified a total of six galaxy groups associated with O VI absorption W r > 0.06 Å that have a median redshift of z gal = 0.1669 and a median impact parameter of D = 134.1 kpc. An additional 12 non-absorbing groups were identified with a median redshift of z gal = 0.2690 and a median impact parameter of D = 274.0 kpc. We find the average equivalent width to be smaller for group galaxies than for isolated galaxies (3σ). However, the covering fractions are consistent with both samples. We used the pixel-velocity two-point correlation function method and find that the velocity spread of O VI in the CGM of group galaxies is significantly narrower than that of isolated galaxies (10σ). We suggest that the warm/hot CGM does not exist as a superposition of halos, instead, the virial temperature of the halo is hot enough for O VI to be further ionised. The remaining O VI likely exists at the interface between hot, diffuse gas and cooler regions of the CGM.

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Bimodality of low-redshift circumgalactic O vi in non-equilibrium eagle zoom simulations

Cited by 213 publications

References 124 publications

Flickering AGN can explain the strong circumgalactic O viobserved by COS-Halos

Flickering AGN can explain the strong circumgalactic O viobserved by COS-Halos

Circumgalactic Oxygen Absorption and Feedback

The Impact of the Group Environment on the O vi Circumgalactic Medium

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